US2118403A - Compressor control - Google Patents

Description

E. E. HEWITT' COMPRESSOR CONTROL Filed Sept. 11, 1957 May 24, 193

QINVENTOR ELLIS E. HEWITT ATTORNEY Patented May 24, 1938 UNITED STATES PATENT 'OFFICE COBIPBESSOR CONTROL -Applicaticn September 11, 1937, Serial No. 163,449

20 Claims.

This invention relates to a compressor control system, and particularly to a control system 'for a motor driven compressor employed on a traction vehicle.

On vehicles equipped with motor driven fluid compressors, governors are provided which are responsive to the pressure of the fluid in the reservoir into which fluid is compressed by the compressor. These governors operate to com- 10 plete the circuit to the compressor driving motor on a reduction in the pressure of the fluid in the reservoir to a predetermined value, and to interrupt this circuit on an increase on the pressure of the fluid in the reservoir to a higher predeter- 15 mined value. v

During operation of a-compressor some noise is created. This noise is not noticeable when the vehicle is in motion as it is obliterated by the other noises present at that time, but the noise created by operation of a compressor is noticeable and is objectionable when the vehicle is standing still, at which time no other noise is created.

Accordingly it is desirable that the control system for the cdmpressor on' a vehicle be arranged so that the compressor normally will'be operated only when the vehicle is in motion. However, if while the vehicle is idle the'pressure of the fluid in the reservoir should be reduced to an abnor- 30 mally low value, the supply of fluid under' p-res-' sure might be insuflicient to maintain the brakes on the vehicle applied, or to effect an application of the brakes if necessary. 7

It is desirable, therefore, that the compressor control system be arranged to effect operation of the compressor when the vehicle is not in motion if the pressure of the fluid in the reservoir falls to a value substantially lower than that at which the control system initiates operation of the compressor when the vehicle is in motion.

It is an object of this invention, therefore, to provide an improved compressor control system which operates in response to variations in the pressure of the fluid in the reservoir into which 45 fluid is compressed by a compressor carried by a vehicle to effect operation of the compressor on a reduction in .this pressure to a predetermined value when the vehicle is in motion,v and which also operates to effect operation of the compressor when the vehicle is not in motion only if the pressure of the fluid in the reservoir reduces to a value substantially lower than said predetermined value.

A further object of the invention is to provide 55 an improved control system for a compressor mounted on a motor driven vehicle, the control system being interconnected with the power controller for the vehicle driving motor so that when the power controller is conditioned to out off the supply of current to the vehicle driving motor, 5 the compressor will be maintained inoperative unless the pressure of the fluid in the reservoir into which fluid is compressed by the compressor is reduced to an abnormally low value.

Another object of the invention is to provide :a compressor control system of the type described and incorporating means responsive to current generated by the vehicle driving motor during movement of the vehicle subsequent to the interruption of the supply of current to the vehicle driving motor to prevent operation of the compressor unless the pressure in the reservoir into which fluid is compressed by the compressor is reduced to a relatively low value.

A further object of the invention is to provide an improved compressor control system incorporating a pneumatic switch device responsive to the pressure of the fluid supplied thereto for con-- trolling the circuit to a compressor driving motor, a valve device for supplying fluid to said switch device at a predetermined pressure below that present in the reservoir into whichflu-id is compressed by the compressor, and havingv means responsive to movement of the vehicle for supplying fluid under pressure to said switch device at 39 the full pressure present in the reservoir.

Another object of the invention is to provide an improved control system for a compressor mounted on a vehicle.

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawing, the single figure of which is a diagrammatic view, partly in section, of a compressor control system embodying this invention.

The equipment shown in the drawing includes a fluid compressor I, an electric compressor driving motor 2, a reservoir 3, a brake cylinder 4, a brake valve device 5, a vehicle driving motor having an armature l, and a field winding 8, a trolley ID, a power controller I2, a pneumatic switch device I 3, valve means M, and a magnet valve device I5.

The compressor l maybe of any suitable well known construction and compresses fluid under pressure into the reservoir 3 through a pipe l'l, while the compressor is driven by the electric driving motor 2 which may be of any suitable construction.

The brake valve device 5 may be of any well known construction and is connected with the reservoir 3 by way of a pipe l8 and with the brake cylinder 4 by way of a pipe 23. The brake valve device is adapted to control the supply of fluid under pressure from the reservoir 3 to the brake cylinder 6, and to also control the release of fluid under pressure from the brake cylinder 4 to thereby control the application and release of the brakes on the vehicle. 7

The power controller I2 may be of the well known construction, and has a handle 22 which is movable between a power off position and a plurality of positions in a power on zone to control the supply of current from the trolley ill to the vehicle driving motor.

The power controller i2 has associated therewith a magnetic contactor having a winding 23 and a movable contact 2 which engages either of two sets of stationary contacts. The movable contact 24 has biasing means associated therewith and yieldingly pressing the contact into engagement with stationary contacts 25, one of which is connected by way of a wire 25 to one terminal of the winding, not shown, of the magnet valve device !5, while the other stationary contact 25 is connected by way of a wire 28 with a wire 30 which leads from the power controller l2 to one of the brushes of the armature 1 of the vehicle driving motor. The other terminal of the winding of the magnet valve device i5 is connected by way of a wire 3| with the wire 32 which leads from the other of the brushes of the armature I to one terminal of the motor field winding 8, while the other terminal of the field winding 8 is connected to ground.

When the winding 23 of the magnetic contactor associated with the power controller I2 is energized, the movable contact M is moved against the biasing means associated therewith out of engagement with the stationary contacts 25 and into engagement with the stationary contacts 34, one of which is connected by way of a wire 35 with the trolley l0, while the other of the stationary contacts 34 is connected by way of a wire 36 to a contact, not shown, mounted within the body of the power controller i2. The handle 22 of the power controller it has associated therewith a movable contact, not shown, which when the handle 22 is in any of its power on positions engages a contact to which is connected a branch of the wire 35 to establish a circuit between the wire 35 and the wire 38 which is connected to one terminal of the winding 23, the other terminal of which is connected to ground. In the power oiT position of the handle 22, the circuit between the wires 35 and 38 is interrupted.

Similarly, in the power off position of the handle 22 of the power controller i2, no circuit is established between the wire 30 leading to the armature l of the vehicle driving motor and the wire 36 leading from the contact M. In the power on positions of the handle 22 a circuit is established between the wire 36 and the wire 33 through suitable resistance, not shown, the amount of the resistance being varied in the usual manner in accordance with the position in the power on zone to which the handle 22 is moved.

A circuit is provided between the wire 33, which is connected to one of the brushes of the armature 1 of the vehicle driving motor, and the wire 26 leading to the winding of the magnet valve device I5. This circuit includes current limiting resistance 40 for limiting the amount of current which may be supplied from the wire 39 to the winding of the magnet valve device 15.

The vehicle driving motor is of a type which, on continued rotation on the armature 1 thereof occasioned by continued movement of the vehicle subsequent to the interruption of the supply of current by the power controller 52, generates a counter E. M. F.

The pneumatic switch device l3 may be of any suitable well known construction, and one form of switch device which may be employed is shown in application Serial No. 79,937 of Burton S. Aikman, filed May 15, 1936. The switch device 53 has a movable abutment in the form of a flexible diaphragm 42 which is responsive to the pressure of the fluid in a control chamber 44, and which actuates mechanism, not shown, for operating a switch controlling the flow of current from the wire 45, which is connected to a suitable source of current, such as the trolley IE, to a wire 46 which is connected to one terminal of the compressor driving motor 2, the other terminal of which is connected to ground.

The mechanism actuated by the diaphragm 42 is arranged so that on a reduction in the pressure of the fluid in the control chamber 44 to a predetermined value, the circuit to the compressor determined value, whereupon the circuit will be interrupted and will remain interrupted until the pressure of the fluid in the control chamber is reduced to the first mentioned predetermined value.

The valve means I4 is provided to control the supply of fluid under pressure to and the release of fluid under pressure from the control chamber 44 of the switch device l3 to normally maintain the pressure of the fluid in the control chamber 44 at a predetermined value less than that present in the reservoir 3.

As shown the valve means i4 comprises a movable abutment in the form of a flexible diaphragm 50 which is clamped between confronting flanges on a cover 5| and a body 52. The flexible diaphragm 5 0 has at one face thereof a chamber 54 which is constantly connected by way of a branch of the pipe l8 with the reservoir 3, while the diaphragm 50 has at the other face thereof a chamber 55 which is constantly connected by way of a pipe 53 with the control chamber 45 of the switch device l3.

The diaphragm has secured centrally thereof a valve seat membertifl which is guided by a bore in the cover 5i and by a bore in a tubular projection 5'! formed on the body 52 and extending into the chamber 55. A coil spring 59 is mounted in the chamber 55 and extends between the seat member 58 and the body 52 and yieldingly urges the seat member 53 and the diaphragm 50 upwardly, as viewed in the drawing, while upward movement of the seat member and of the diaphragm is limited by engagement of a nut 60 with a surface (it formed on the cover 5!.

Downward movement of the diaphragm 50 and the seat member 58 is limited by engagement of the seat member with the end of the projection 51, and the various parts of the valve means it are arranged so that on movement of the seat member 58 into engagement with the end of the tubular projecting portion 51, the lower end of the seat member 58 will not close off communication between the chamber within the tubular portion 51 and the chamber 55 through the ports 63.

The seat member 58 has a central bore extending therethrough in which is mounted .a valve element 65 having a fluted stem and having a seating face 66 formed thereon and adapted to engage a seat formed on the seat member 58 surrounding the passage in which the valve element 65 is mounted. A coil spring 61 is mounted in the chamber 54 and extends between the valve element 65 and the cover 5| and yieldingly presses the valve 85 downwardly so that the seating face 68 thereon engages the seat on the seat member 58.

The valve element 65 also has a seating face 68 formed thereon which is adapted to engage a seat surrounding a passage formed in the body 52 and communicating with the atmosphere by way of passages 69. The valve element 65 has a reduced fluted end portion which extends through the passage in the body 52 and guides the lower end of the valve element 65.

The portion of the body 52 surrounding the passage in which the end of the valve element 65 is mounted has a seating face indicated at 18 formed thereon andadapted to be engaged by a seating face indicated at H on a plunger 13 which is mounted in a bore in the body 52. The head of the plunger 13 is engaged by one face of a flexible diaphragm 15 which is clamped between the body 52 and a cover 18. The diaphragm has at the face thereof a chamber 18 which is open to the atmosphere through a passage 79. The diaphragm l5 has at the other face thereof a chamber 80 which is connected by way of a pipe 8| with a chamber 82 in the magnet valve device IS.

The plunger l8 is adapted on the supply of fluid under pressure to the chamber 38 to be moved upwardly, as viewed in the drawing, and to engage the end of the stem of the valve element 65 before the seating face H thereon engages the seating face 18 formed on the body 52. On further movement of the plunger '53, the seating face 68 on the valveelement 65 is moved away from the seating face formed on the body 52, while the seating face H on the plunger 7; is moved into engagement with the seating face 10 formed on the body 52.

The magnet valve device I5 may be of any suitable construction and as shown has a body having a chamber 82 therein in which is mounted a double seating valve element 85, which is adapted to seat upon a seat surrounding a passage open to a chamber 88 which is constantly connected by way of a branch of the pipe G8 with the reservoir 3. The double seating valve element 85 is also adapted to seat upon a seat surrounding a passage open to a chamber 88 which is constantly connected to the atmosphere by way of the passage 89.

A coil spring 98 is mounted in the chamber 86 and yieldingly presses the double seating valve element 85 to its upper seated position to cut off communication between the chamber 82 and the atmospheric chamber 88, and to permit the sup-- ply of fluid under pressure from the chamber 85 to the chamber 82. On energization of the winding, not shown, of the magnet valve device 15, the double seating valve element 85 is moved to the lower seated position, as shown in the drawing, to cut off communication between the chamber 86 and the chamber 82, and to establish communication between the chamber 82 and the chamber 88.

The equipment is shown in the drawing in the position which it assumes when the handle 22 of the power controller I2 is in one of its power on positions, at which time a circuit is established between a branch of the wire leading from the trolley l8, and the wire 38 leading to the winding of the magnetic contactor associated with the power controller.

As a result of energization of the winding. 23, the movable contact 28 is held in the upper position as shown in the drawing, thereby establishing a circuit between the stationary contacts 34, thus establishing a circuit between the Wire 35 and the wire 36 so that current is supplied from the wire 38 to the wire 38 through the resistanoe incorporated in the power controller l2, the amount of which depends upon the position of the handle 22. As a result of the supply of current to the wire 38, current flows to the armature and the winding 8 of the vehicle driving motor and causes the motor to drive the vehicle.

Current supplied to the Wire 3!) flows through the wire 23 to one of the contacts 25, out as the movable contact 24 is in its upper position no circuit is established between the stationary con tacts 25, and current cannot flow from the wire 38 through the contacts 25 to the wire 28 leading to the winding of the magnet valve device i5.

Current supplied to the wire 38 flows therefrom through the current limiting resistance 48 and the Wire 26 to one terminal of the Winding of the magnet valve device l5, and from the other terminal of this winding through the wire 3| to the wire 82, which connects a brush of the armature l with the fleld Winding 8, and thence through the field winding 8 to ground, thereby energizing the winding of the magnet valve device l5.

As a result of energization of the winding of the magnet valve device !5, the double seating valve element 85 is held in its lower seated position against the spring 98, thereby preventing communication between the chamber 86 and the chamber 82 andconnecting the chamber 82 to the atmospheric chamber 88.

The switch device i3 is shown in the drawing in the position to complete the circuit to the compressor driving motor 2, while the various parts of the valve means M are shown in the position which they assume when fluid under pressure is present in the reservoir 3 at a pressure above a low value.

As the circuit to the compressor driving motor 2 is completed, the motor will drive the compressor and the compressor will compress fluid into the reservoir 3 and increase the pressure of the fluid present therein. On the increase in the pressure of the fluid in the reservoir 3 there is a similar increase in the pressure of the fluid in the chamber 54 of the valve means 54, and a corresponding increase in the force exerted on the diaphragm 58, and the diaphragm and the seat member 58 are moved downwardly against the opposing pressures of the fluid present in the chamber 55 and of the spring 59, thereby moving the seat on the seat member 58 away from the seating face 85 on the valve element to permit fluid under pressure to flow from the chamber E i to the chamber 55, and to the control chamber M- of the switch device It to increase the pressure of the fluid in the chambers 44 and 55.

On an increase in the pressure of the fluid in the chamber 55 there is an increase in-the force exerted on the diaphragm 58 in opposition to the force exerted by the fluid in the chamber 54.

When the pressure of the fluid in the chamber 55 increases to a predetermined value below that present in the chamber 541, the force exerted by the fluid in the chamber 55, assisted by the spring 59, overcomes the opposing force of the fluid in the chamber 54, and the diaphragm 56 and the seat member 58 are moved upwardly, as viewed in the drawing, so that the seat on the seat member 58 engages the seating face 56 on the valve element E5 to cut ofi the further supply of fluid under pressure from the chamber 54 to the chamber 55 and to the control chamber 4 of the switch device l3.

It will be seen, therefore, that the valve means l4 operates during an increase in the pressure of the fluid in the reservoir 3 to supply fluid under pressure from the reservoir 3 to the control chamber it of the switch device iii to maintain the pressure of the fluid therein at a predetermined value below that present in the reservoir 3, and that this pressure differential is determined by the spring 59.

When the pressure of the fluid in the reservoir 3 and in the chamber 5d of the valve means M has increased to a predetermined relatively high value, the valve means it will be operated to supply fiuid under pressure to the chamber 55 and to the control chamber at of the switch device is to increase the pressure of the fluid present therein to a value high enough to efiect movement of the diaphragm 42 of the switch device 53 to actuate the mechanism associated therewith to interrupt the circuit leading to the driving motor 2 for the compressor l, thereby interrupting operation of the compressor 1.

On a subsequent reduction in the pressure of the fluid in the reservoir 3, which may be occasioned by the use of fluid under pressure from the reservoir 3 by the brake valve device 5 in applying the brakes, there is a similar reduction in the pressure of the fluid in the chamber 54 of the valve means Hi. On the reduction in the pressure of the fluid in the chamber 54, there is a corresponding reduction in the force exerted upon the diaphragm 59, and the fluid under pressure in the chamber 55, assisted by the spring 59, moves the diaphragm 5i and the seat member 58 upwardly, as viewed in the drawing,while the seat on the seat member 53 presses against the seating face 615 on the valve element so that the valve element 65 is moved against the spring 61 with the result that the seating face 68 on the valve element 65 is moved away from the seat on the body 52.

On movement of the seating face 68 of the valve element "55 away from the seat on the body 52, fluid under pressure is released from the chamber 55 of the valve means M and from the control chamber 44 of the switch device l3 to the atmosphere through the passages 59, thereby reducing the pressure of the fluid present in the chambers id and 55.

On this reduction in the pressure of the fluid in the chamber 55, there is a corresponding reduction in the force exerted by this fluid upon the diaphragm. 5!], and the higher pressure of the fluid in the chamber 54 at the opposite face of the diaphragm moves the diaphragm 5G and the seat member 58 downwardly against the opposing force of the fluid in the chamber 55 and of the spring 59, while the spring 6? maintains the seating face 66 on the valve element 65 in engagement with the seat on the seat member 58, and also moves the valve element 65 towards the seat on the body 52 to cut off the release of fluid under pressure from the chamber 55 through the passages 69.

When the pressure of the fluid in the chamber 55 has been reduced by flow therefrom through the passages 69 to a predetermined value below that present in the chamber 54, the diaphragm 5B and the seat member 58 will be moved downwardly against the opposing force of the fluid in the chamber 55, and of the spring 59, far enough to permit the spring 5'! to move seating face 68 on the valve element 65 into engagement with the seat on'the body 52 to thereby cut on" the further release of fluid under pressure from the chamber 55.

It will be seen, therefore, that on a reduction in the pressure of the fluid in a reservoir 3, the valve means It operates to release fluid under pressure from the chamber 55 and from the control chamber '34 of the switch device l3 to maintain the pressure of the fluid therein at a predetermined value below that present in the reservoir 3, and that this pressure differential is determined by the value of the spring 59.

On the reduction in the pressure of the fluid in the control chamber d4 of the switch device l3 there is a corresponding reduction in the force exerted on the diaphragm. e2, but the mechanism actuated by the diaphragm d2 is arranged so that when it is conditioned to interrupt the circuit to the driving motor 2 of the compressor I, it will not be operated to establish this circuit until the pressure of the fluid in the control chamber 44 is reduced to a value substantially below that which is required to effect operation of the switch device to interrupt the circuit to the compressor driving motor.

Accordingly, on a reduction in the pressure of the fluid in the control chamber 54, the switch device It will operate to maintain the circuit to the compressor driving motor interrupted until the pressure of the fluid in the control chamber is reduced to a predetermined value, whereupon the diaphragm 42 will be moved against the 0pposing force of the fluid in the control chamber 44, and the mechanism actuated by the diaphragm S2 will operate to establish the circuit to the compressor driving motor 2, and the compressor i will then be operated to supply fluid under pressure to the reservoir 3 to increase the pressure of the fluid therein.

On the increase in the pressure of the fluid in the reservoir 3, the valve means M operates as described in detail above to supply fluid under pressure to the control chamber 46 of the switch de vice 15 to maintain the pressure of the fluid therein at a predetermined value below that present in the reservoir 3, while upon an increase in the pressure of the fluid in the reservoir 3 to a predetermined relatively high value, the pressure of the fluid in the control chamber 44 will be increased to a value high enough to efi'ect operation of the switch device It to again interrupt the circuit to the driving motor 2 for the compressor l.

The spring 59 which determines the differential maintained by the valve means M between the fluid in the reservoir 3 and the chambers 55 and 44 is proportioned so that this differential is equal to that which it is desired to maintain between the pressures at which operation of the compressor is initiated when the vehicle is in motion and when the vehicle is not in motion.

Thus if when the vehicle is in motion, it is desired to initiate operation of the compressor on a reduction in the pressure of the fluid in the reservoir 3 to one hundred pounds, and when the vehicle is not in motion to maintain the compressor inoperative until the pressure of the fluid in the reservoir is reduced to ninety pounds, the spring 59 will be proportioned to prevent movement of the diaphragm 50 by the fluid in the chamber 54 until the pressure of the fluid therein is increased to a value of ten pounds above that present in the chamber 55.

The compressor control system provided by this invention is arranged so that when the vehicle is not in motion, the compressor 1 will not be operated to supply fluid under pressure to the reservoir 3 until the pressure of the fluid in the reservoir is reduced to a somewhat lower value than that at which operation of the compressor is initiated when the vehicle is in motion, and so that operation of the compressor is cut off when the pressure of the fluid in the reservoir is increased to a somewhat lower value than the pressure at which operation of the compressor is cut off when the vehicle is in motion.

When movement of the vehicle is to be stopped, the handle 22 of the power controller !2 is turned from a position in the power on zone to the power off position, and on this movement of the handle 22, the movable contact, not shown, operated by the handle 22 interrupts the circuit from the branch of the wire 35 to the wire 38 leading to one terminal of the winding 23 of the magnetic contactor associated with the power controller l2. In addition, on this movement of the handle 22, the circuit from the wire 35 leading from the stationary contact 34 to the wire 35 is interrupted.

On the interruption of the circuit through the Winding 23 of the contactor associated with the power controller l2, the winding 23 ceases to exert force to maintain the movable contact 24 in engagement with the stationary contacts 34, and the movable contactv 24 is moved by the biasing means associated therewith into engagement with the stationary contacts 25, thereby completing a circuit from the wire, 30 to the Wire 26 leading to the winding of the magnet valve device I5.

This completes a circuit from the vehicle driving motor through the winding of the magnet valve device l5 which shunts the current limiting resistance 45.

After movement of the handle 22 of the power controller 12 from the position in the power on zone to the power off position, movement of the vehicle will continue for a time interval, and the armature l of the vehicle driving motor will be rotated. As a result of rotation of the armature l a counter E. M. F. or current will be generated and will flow through the winding of the magnet valve device l5 by way of a circuit which includes the wire 30 and the wire 28, the movable contact 24, the wire 26, and the wire 31. As long as the vehicle continues to move at any substantial speed, the current generated by the vehicle driving motor will be suificient to energize the winding of the magnet valve device 15 and cause the double seating valve element 85 to be held in its lower seated position against the spring 90.

Accordingly, as long as the vehicle is in motion with the handle 22 of the power controller l2 either in one of its power on positions or in the power off position, the double seating valve element 85 of the magnet valve device [5 will be held in its lower seated position, while the chamber 80 at the face of the diaphragm "l5 of the valve means l4 will be connected to the atmosphere. As a result, therefore, the valve means l4 will operate as long as the vehicle is .in motion to maintain the pressure of the fluid in the chamber 55 and in the control chamber 44 of the switch device H1 at a predetermined value below that present in the reservoir 3.

When the vehicle is not in motion, the armature T of the vehicle driving motor is not rotated and no current or counter E. M. F. is generated thereby, and hence current is not supplied to the winding of the magnet valve device l5. On deenergization of the winding of the magnet Valve device I5, the double seating valve element 85 is moved by the spring from the lower seated position to the upper seated position, thereby cutting off communication between the chamber 82 and the atmospheric chamber 88, and permitting communication from the chamber 86 to the chamber 82. I

On movement of the double seating valve element 85 to the upper seatedposition, fluid under pressure supplied from the reservoir 3 flows to the chamber 32 and thence by way of the pipe 8! tothe chamber 8 9 at the face of the diaphragm 15 of the valve means I4. As a result of the supply of fluid under pressure to the chamber 85 force is exerted upon the diaphragm l5 and moves the stem l3 upwardly so that the end of this stem engages and presses against the end of the valve element 65, thereby moving this valve element against the spring 61, while the seating face 66 on the valve element 65 is moved away from the seat on the seat member 58 to thereby open communication between the chamber 54 and the chamber 55. In addition, on this movement of the valve element 65, the seating face 58 thereon is moved away from the seat formed on the body 52. However, the release of fluid under pressure from the chamber to the atmosphere is prevented because on upward movement of the plunger '13, the seating face H thereon seats upon the seating face 10 on the body 52 and cuts off the flow of fluid from the chamber 55.

On movement of the seating face 66 on the valve element 55 away from the seat on the seat member 58, fluid under pressure flows from the reservoir 3 and the chamber 54 to the chamber 55, and thence to the control chamber of the switch device l3 and increases the pressure of the fluid in these chambers. On an increase of the pressure of the fluid in the chamber 55 there is a corresponding increase in the force exerted upon the diaphragm 50, and the diaphragm and the seat member 58 are moved upwardly against the opposing force of the fluid in the chamber 54.

On this upward movement of the seat member 55, the seating face thereon is moved towards the seating face 56 on the valve element 65.

The various parts of the valve means I 4 are arranged and proportioned, however, so that further upward movement of the seat member 58 is prevented by engagement of the nut 60 with the surface '6! on the cover section 5! before the seat on the seat member 58 engages the seating face '56 on the valve element when the valve element 65 is in the position in. which it is held by the plunger 73 when the surface 11 on the plunger 13 is in engagement with the seating face it formed on the body 52.

Accordingly fluid under pressure from the reservoir 5 and the chamber 54 flows past the seating face 55 on the valve element 65 to the chamber 55, and to the control chamber 44 of the switch device l3 to increase the pressure of the fluid in the chambers 44 and 55 to the full pressure present in the reservoir 3.

As the switch device I3 is subject at this time to the full pressure of the fluid. in the reservoir 3, instead of to a pressure a predetermined value below that present in the reservoir, the switch device l3 will operate to prevent operation of the compressor l until the pressure of the fluid in the reservoir 3 is reduced to a lower value than that at which operation of the compressor is initiated when the vehicle is in motion.

Similarly, the switch device it will operate to cut oiT operation of the compressor I when the pressure of the fluid in the reservoir 8 is increased to a lower value than that at which operation of the compressor is cut off when the vehicle is in motion.

Thus if the spring 58 is proportioned to maintain a pressure differential of ten pounds between the pressure of the fluid in the chambers 54 and 55, and if the switch device i3 is adjusted to initiate operation of the compressor l on a reduction in the pressure of the fluid in the con-- trol chamber 44 to ninety pounds, the switch device will operate when the vehicle is in motion to initiate operation of the compressor upon a reduction in the pressure in the fluid of the reservoir 3 to one hundred pounds, because, as pointed out above, when the vehicle is in motion, the valve means I4 operates to maintain the pressure of the fluid in the control chamber M ten pounds below that present in the reservoir 3.

However, when the Vehicle is not in motion, the switch device l3, being then supplied with fluid under pressure at the full pressure carried in the reservoir 3, will operate to initiate operation of the compressor I only after a reduction in the pressure in the fluid in the reservoir 3 to ninety pounds.

Likewise, the switch device l3 will operate when the vehicle is not in motion to cut oif operation of the compressor 1 when the pressure of the fluid in the reservoir 3 has built up to a lower value than is effective to cause operation of the switch device l3 to cut oif operation of the compressor 1 when the vehicle is in motion.

On a subsequent movement of the handle 22 of the power controller l2 from the power off position to a position in the power on zone, the movable contact controlled by the handle 22 establishes a circuit between a branch of the wire 35 and the wire 38 leading to the winding 23 of the contactor associated with the power controller !2. On energization of the winding 23, the movable contact 24 is moved out of engagement with the stationary contacts 25, thereby interrupting the circuit through which current was supplied from the vehicle driving motor to the winding of the magnet valve device i5. On this movement of the movable contact 215 it is moved into engagement with the stationary contacts 34, thereby establishing a circuit from the wire 35 leading from the trolley ill to the wire 35, while on movement of the handle 22 of thepower controller l2 to a position in the power on zone a circuit is established between the wire 35 and the wire 30 leading to one of the brushes of the armature 1 of the vehicle driving motor, and the vehicle driving motor is operated to effect movement of the vehicle.

On the supply of current to the wire 30, current flows therefrom through the current limiting resistance 4!] to the wire 35, through the winding of the magnet valve device l5, and thence by way of the wire 3i and the field winding 8 to ground, thereby energizing the winding of the magnet valve device [5.

On energization of the winding of the magnet valve device I5, the double seating valve element 85 is moved from its upper seated position to its lower seated position, thereby cutting off the supply of fluid under pressure from the reservoir 3 and the chamber 86 to the chamber 82 and establishing communication between the chamber 82 and the atmospheric chamber 88. Upon movement of the double seating valve element 85 to the lower seated position, therefore, fluid under pressure is released from the chamber 85 at the face of the diaphragm of the valve means M.

On the reduction in the pressure of the fluid in the chamber there is a corresponding reduction in the force exerted on the diaphragm 75 and on the plunger 13. 'When the pressure of the fluid in the chamber 80 is reduced to a relatively low value, the spring 51 operating through the valve element 65 moves the plunger it downwardly so that the seating face H on the plunger 73 is moved away from the seating face if! on the body 52.

On this movement of the plunger 13 the spring 67 moves the valve element relative to the seat member 58, which at this time is held by the fluid under pressure in the chamber 55 in the position determined by engagement of the nut 60 with the surface 6! on the cover 5i. On this movement of the valve element 65 by the spring 6?, the seating face 58 on the valve element 65 is moved towards the seating face formed on the body 52, while theseating face 65 on the valve element 65 is moved into engagement with the seating face formed on the seat member 58.

The various parts of the valve means M are arranged and proportioned so that when the seat member 58 is in the position determined by engagement of the nut 50 with the surface 6!, the seating face 65 on the valve element 55 will be moved into engagement with the seating face on the seat member 58 to thereby cut off the flow of fluid under pressure from the chamber 54 tothe chamber 55 before the seating face 58 on the Valve element 65 is moved into engagement with the seating face formed on the body 52 to cut off the release of fluid under pressure from the chamber 55.

Accordingly, upon movement of the plunger 13 occasioned by the release of fluid under pressure from the chamber 80, the valve element 55 will be moved to a position to cut off the supply of fluid under pressure to the chamber 55, but to permit the release of fluid under pressure from the chamber 55 through the passages 55.

As a result of the release of fluid under pressure from the chamber 55 through the passages 69 there is a reduction in the pressure of the fluid in the chamber 55 and in the control chamber 44 of the switch device it, and a corresponding reduction in the force exerted by the fluid under pressure in the chamber 55 upon the diaphragm 55.

On a reduction in the pressure of the fluid in the chamber 55 to a predetermined value below that present in the chamber 5 5, the force exerted by the fluid in the chamber 55 and by the spring 59 on the diaphragm 55 is insufllcient to maintain the diaphragm 5!) and the seat member 53 against the opposing force of the fluid in the chamber 54, and the diaphragm 5t and the seat member 58 are thereupon moved downwardly, as viewed in the drawing, against the opposing force of the fluid in the chamber 55 assisted by the spring 59.

On this downward movement of the diaphragm and the seat member 58, the valve element 65 is moved with the seat member 58 by the spring 61 with the result that the seating face 65 on the valve element 65 is held in engagement with the seat on the seat member 58, while the seating face 68 on the valve element 65 is moved towards its seat on the body 52. When the pressure of the fluid in the chamber 55 is reduced to a predetermined value below that present in the chamher 54, the diaphragm 50 and the seat member 58 will be moved far enough by the fluid in the chamber 54 to cause the seating face 68 on the valve element 65 to engage the seat on the body 52 to cut off the further release of fluid under pressure from the chamber 65 and from the control chamber 44 of the switch device l3, and the valve means M will operate thereafter to maintain the pressure of the fluid in the chamber 55 and in the control chamber 44 at a predetermined value below that present in the reservoir '3, while the switch device It will operate as described above in response to variations in the pressure of the fluid in the control chamber 44 tocomplete or interrupt the circuit to the driving motor 2 for the compressor I.

From the foregoing it will be seen that the compressor control system provided by this invention incorporates a pressure responsive switch device for controlling the circuit to the compressor driving motor, and that valve means is provided for normally maintaining the pressure of the fluid supplied to the switch device at a predetermined value below that present in the reservoir into which fluid is compressed by the compressor.

It will be seen also that the control system incorporates means controlled by the power controller for the vehicle driving motor for supplying fluid under pressure to the switch device at the full pressure present in the reservoir when the vehicle is not in motion to thereby eiTect operation of the switch device to maintain the circuit to the compressor driving motor interrupted when the vehicle is not in motion until the pressure of the fluid in the reservoir is reduced to a somewhat lower value than that at which operation of the compressor is initiated when the vehicle is in motion.

While one embodiment of the improved compressor control system provided by this invention has been illustrated and described in detail, it should be understood that the invention is not limited to these details of construction, and that numerous changes and modifications may be made Without departing from the scope of the following claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In combination, a fluid compressor carried by a vehicle, an electric motor for driving said compressor, switch means responsive to a predetermined increase in fluid pressure in a control chamber vfor opening the circuit of said motor and to a predetermined decrease in the pressure of fluid in said chamber for closing the circuit, a valve device operative to supply fluid under pressure to said chamber at a predetermined degree less. than the pressure of fluid compressed by the compressor, and means operative upon stopping of the vehicle for supplying fluid at the pressure of fluid compressed by said compressor to said chamber.

2. In combination, a fluid compressor carried by a vehicle, said vehicle having a driving motor operative on continued movement of the vehicle subsequent to the interruption of the supply of current thereto to generate a counter E. M. F., an electric motor for driving said compressor, switch means responsive to a predetermined increase in the pressure of the fluid in a control chamber for opening the circuit of the compressor driving motor and to a predetermined decrease in the pressure of the fluid in said chamber for closing said circuit, valve means operative to supply fluid under pressure to said chamber at a predetermined degree less than the pressure of the fluid compressed by the compressor, and means controlled by the counter E. M. F. generated by the vehicle driving motorand operative upon a predetermined reduction in said counter E. M. F. for supplying fluid to said chamber at the pressure of the fluid compressed by the compressor.

3. The combination with a vehicle having a driving motor and a power controller for said motor, said power controller having power on and power ofi positions, a fluid compressor carried by said vehicle, a driving motor for said compressor, a reservoir into which fluid is com- I pressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the circuit to the compressor driving motor, a valve controlling the supply and release of fluid under pressure to and from said control chamber, a movable abutment subject to the pressure of the fluid in said reservoir for controlling said valve, and means controlled by said power controller for also controlling said valve.

4. The combination with a vehicle having a driving motor and a power controller for said motor, said power controller having power on and power off positions, a fluid compressor carried by said vehicle, a driving motor for said compressor, a reservoir into which fluid is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the circuit to the compressor driving motor, a movable abutment subject to the opposing pressures of the fluid in the reservoir and of the fluid in said control chamber, a valve operated by said abutment and controlling the supply and release of fluid under pressure to and from said control chamber, and means. controlled by said power controller for also operating said valve.

5. The combination with a vehicle having a driving motor and a power controller for said motor, said power controller having power on and power off positions, a fluid compressor carried by said vehicle, a driving motor for said compressor, a reservoir into which fluid is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the circuit to the compressor driving motor, a movable abutment subject to the opposing pressures of the fluid in said reservoirand of the fluid in said control chamber for controlling the supply of fluid under pressure to said control chamber and for also controlling a release passage through which fluid under pressure may be released from said control chamber, and means controlled by said power controller for supplying fluid under pressure to said control chamber and for cutting off communication through said release passage.

6. The combination with a vehicle having a driving motor and a power controller therefore, said'power controller having power on and power Cir vehicle, a driving motor for said compressor, a reservoir into which fluid is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the circuit to the compressor driving motor, valve means responsive to the opposing pressures of the fluid in said reservoir and of the fluid in said control chamber for supplying fluid under pressure to and for releasing fluid under pressure from. said control chamber to maintain the pressure of the fluid in said control chamber at a predetermined value below that present in the reservoir, and means controlled by said power controller for supplying fluid under pressure to said control chamber at the pressure present in the reservoir and for cutting off the release of fluid from said control chamber by said valve means.

7. The combination with a vehicle, a fluid compressor carried by said vehicle, a driving motor for said compressor, a reservoir into which fluid is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the circuit to the compressor driving motor, valve means responsive to the opposing pressures of the fluid in said reservoir and of the fluid in said control chamber for supplying fluid under pressure to and for releasing fluid under pressure from said control chamber to maintain the pressure of the fluid in said control chamber at a predetermined value below that present in the reservoir, and means responsive to movement of the vehicle for supplying fluid under pressure to said control chamber at the pressure present in the reservoir and for cutting off the release of fluid from said control chamber by said valve means.

8. The combination with a vehicle having a driving motor and a power controller therefore, said power controller having power on and power oiT positions, a fluid compressor carried by said vehicle, a driving motor for said compressor, a reservoir into which fluid is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the circuit to the compressor driving motor, valve means responsive to the opposing pressures of the fluid in said reservoir and of the fluid in said control chamber for supplying fluid under pressure to and for releasing fluid under pressure from said control chamber to maintain the pressure of the fluid in said control chamber at a predetermined value below that present in the reservoir, and means controlled by said power controller for conditioning said valve means to supply fluid under pressure to said control chamber at the full pressure present in the reservoir and for cutting off the release of fluid from said control chamber by said valve means.

9. The combination with a vehicle, a fluid compressor carried by said vehicle, a driving motor for said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the circuit to the compressor driving motor, valve means responsive to the opposing pressures of the fluid in said reservoir and of the fluid in said control chamber for supplying fluid under pressure to and for releasing fluid under pressure from said control chamber to maintain the pressure of the fluid in said control chamber at a predetermined value below that present in the reservoir, and means responsive to movement of the vehicle for conditioning said oif positions, a fluid compressor carried by said valve means to supply fluid under pressure at the full pressure present in the reservoir and for cutting off the release of fluid from said control chamber by said valve means.

10. In a control system for a fluid compressor mounted on a vehicle, in combination, a fluid compressor, a reservoir into which fluid is compressed by said compressor, an electric driving motor for driving the compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the supply of current to said compressor driving motor, a valve controlling the supply and release of fluid under pressure to and from said control chamber, a movable abutment subject to the pressure of the fluid in said reservoir for actuating said valve, an abutment subject to the pressure of the fluid in an operating chamber for also controlling said valve, a driving motor for the vehicle, a power controller for controlling the supply of current to said vehicle driving motor, and means controlled by said power controller for controlling the supply of fluid under pressure to said operating chamber.

11. The combination with a vehicle having a driving motor and a power controller for said motor, said power controller having power on and power oiT positions, a fluid compressor carried by said vehicle, a driving motor for said compressor, a reservoir into which fluid is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for con trolling the circuit tothe compressor driving motor, a valve controlling the supply and release of fluid under pressure to and from said control chamber, a spring, a movable abutment subject to the opposing. pressures of said spring and of the fluid in said reservoir for controlling said valve, and means controlled by said power controller for also controlling said valve.

12. The combination with a vehicle having a driving motor and a power controller for said motor, said power controller having power on and power off positions, a fluid compressor carried by said vehicle, a driving motor for said com- I pressor, a reservoir into which fluid is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the circuit to the compressor driving motor, a movable abutment responsive to the pressure or" the fluid in said reservoir, a valve movable with said abutment for releasing fluid under pressure from said control chamber and movable relative to said abutment for supplying fluid under pressure to said control chamber, and means controlled by said power controller for moving said valve relative to said abutment.

13. The combination with a vehicle having a driving motor and a power controller for said motor, said power controller having power on and power off positions, a fluid compressor carried by may be supplied to said control chamber and also controlling a release passage through which fluid under pressure may be released from said control chamber, and means controlled by said power controller for controlling the release passage and for operating said valve to open said supply passage. 1

14. The combination with a vehicle having a drivingmotor operative on the supply of current thereto to propel the vehicle, said motor being also operative to generate a current on movement of the vehicle while the supply of current thereto is cut off, a fluid compressor mounted on said vehicle, a driving motor for said compressor, a reservoir into which fluid under pressure is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the supply of current to said compressor driving motor, valve means responsive to the pressure of the fluid in said reservoir for supplying and releasing fluid under pressure to and from said control chamber, and means operative on the supply of current to the vehicle driving motor and on the generation of a current by said motor for controlling said valve means.

15. The combination with a vehicle having a driving motor operative on the supply of current thereto to propel the vehicle, said motor being also operative to generate a current on movement of the vehicle while the supply of current thereto is cut oii, a fluid compressor mounted on said vehicle, a driving motor for said compressor, a reservoir into which fluid under pressure is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamher for controlling the supply of current to said compressor driving motor, valve means responsive to the pressure of the fluid in said reservoir for supplying and releasing fluid under pressure to and from said control chamber, and means operative on the supply of current to the vehicle driving motor and on the generation of a current by said motor for supplying fluid under pressure from said reservoir to said control chamber.

16. The combination with a vehicle having a driving motor operative on the supply of current thereto to propel the vehicle, said motor being also operative to generate a current on movement of the vehicle while the supply of current thereto is out off, a fluid compressor mounted on said vehicle, a driving motor for said compressor, a reservoir into which fluid under pressure is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the supply of current to said compressor driving motor, valve means responsive to the pressure of the fluid in said reservoir for supplying and releasing fluid under pressure to and from said control chamber, and means operative on the supply of current to the vehicle driving motor and on the generation of a current by said motor for supplying fluid under pressure from said reservoir to said control chamber, and for also cutting oiT the release of fluid from said control chamber by said valve means.

17. The combination with a vehicle having a driving motor operative on the supply of current thereto to propel the vehicle, said motor being also operative to generate a current on movement of the vehicle while the supply of current thereto is out ofl, a fluid compressor mounted on said vehicle, a driving motor for said compressor, a reservoir into which fluidunder pressure is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the supply of current to said compressor driving motor, valve means responsive to the opposing pressures of the fluid in said control chamber and of the fluid in said reservoir for supplying fluid under rent to said vehicle driving motor and on the generation of a current by said motor to supply fluid under pressure from said reservoir to said control chamber and to cut oif communication through said release passage.

18. The combination with a vehicle having a driving motor operative on the supply of current thereto to propel the vehicle, said motor being also operative to generate a current on movement of the vehicle while the supply of current thereto is cut ofl", a fluid compressor mounted on said vehicle, a driving motor for said compressor, a reservoir into which fluid under pressure is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the supply of current to said compressor driving motor, valve means responsive to the opposing pressures of the fluid in the reservoir and of the fluid in the control chamber and operative to supply fluid from the reservoir to the control chamber and to release fluid from the control chamber through a release passage to maintain the pressure of the fluid in the control chamber at a predetermined value below that present in the reservoir, and means responsive to the supply of current to the vehicle driving motor and to the generation of a current by said motor for supplying fluid from said reservoir to said control chamber and for cutting off communication through said release passage.

19. The combination with a vehicle having a driving motor operative on the supply of current thereto to propel the vehicle, said motor being also operative to generate a current on movement of the vehicle while the supply of current thereto is cut off, a power controller for controlling the supply of current to the driving motor, said power controller having power on and power ofl positions, a fluid compressor mounted on said vehicle, a driving motor for said compressor, a control device for controlling the circuit to the compressor driving motor, and means operative when the power controller is in the power on position or when the motor is generating a current to effect operation of the control device to establish the circuit to the compressor driving motor on a reduction on the pressure of the fluid in said reservoir to a predetermined value, said means being operative when the power controller is in the power off position and the motor is not generating a current to effect operation of the control device to complete the circuit to the compressor driving motor only on a reduction in the pressure of the fluid in said reservoir to a value less than said predetermined value.

20. The combination with a vehicle having a driving motor operative on the supply of current thereto to propel the vehicle, said motor being also operative to generate a current on movement of the vehicle while the supply of current thereto is cut ofi, a power controller for controlling the supply of current to said motor, a fluid compressor mounted on said vehicle, a driving motor for said compressor, a reservoir into which fluid under pressure is compressed by said compressor, switch means responsive to the pressure of the fluid in a control chamber for controlling the supply of current to said compressor driving motor, valve means responsive to the opposing pressures of the fluid in the reservoir and of the fluid in the control chamber and operative to supply fluid from the reservoir to the control chamber and to release fluid from the control chamber through a release passage to maintain the pressure of the fluid in the control chamber at a predetermined value below that present in the reservoir, and means controlled by said power controller and responsive to current generated by said vehicle driving motor for supplying fluid from said reservoir to said control chamber and for cutting off communication through said release passage.

ELLIS E. HEWITT.

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