US2356916A - Variable capacity pump or motor - Google Patents

Description

Aug'. 29, 1944.

*Ori

P. D. BREWSTER VARIABLE CAPACITY PUMP 0R Mo'fo` Filed Sept. 11, 1940 2 Sheets-Sheet 1 A118129, 1,944. P. D. BREWSTER 2,356,916

` VARIABLE CAPACITY PUMP OR MOTOR Fi1ed sept. 11, 1940 2 sheets-sheet 2 22 l l r 7 Patented Aug. 29, 1944 VARIABLE CAPACITY PUMP R MOTOR Percy D. Brewster, Holmdel, N. J., assignor to Casse Brewster, East Orange, N. J.

Application September 11, 1940, Serial No. 356,250

4 Claims. (Cl. 10S- 120) My invention relates to variable capacity-pressure rotary hydraulic pumps and variable torque-v It is particularspeed hydraulic rotary motors. ly related to the type of pump or motor consisting of a round cylinder in which a rotor revolves which has a plurality of cavities or slots in its periphery containing rollers adapted .to maintain contact with the rotor cavities and the cylinder bore.

In my copending patent applications Ser. Nos. 356,248 and 356,249 relating to pumps of the above type, I describe among other thingsv compound rollers of diierent constructions adapted to maintain substantial contact between the rotor and cylinder. These compound rollers have in common the principle that one part of the roller rolls on the cylinder bore and another part of the roller. adapted to. turn freely in relation to first part. rolls on the side of the rotor slots, no part touching both the cylinder and rotor. Improved means were also described in these applications for maintaining the rollers in substantial contact with the cylinder bore. Some of these ideas are shown in the accompanying drawing but are not particularly described herein.

Throughout the specification and claims the term engine is understood to include motors and gether behind the rollers but it is to be understood that any number of slots or cavities may be used and that they be independent of each other or connected together without departing from my invention.

An object of my invention is to provide a. variable capacity hydraulic pump adapted to operate efllciently at high rotative.y speeds. Another object is to convert the roller type pump into a variable capacity pump. A furtherobject is to provide simple means, operated hydraulically,for controlling the output of the pump. Another object is to provide main inlet and discharge ports in the movable cylinder and auxiliary ports in the fixed cylinder heads. To these and other ends my invention comprises the novel features hereinafter described.

Fig. 1 in the drawings is a section on the ;enter line AB of Fig. 2 with rotor and rollers shown as end elevations; Fig. 2 is a section on CD, Fig. 1;

for the rollers, of motors operating clockwise, and Fig. 10 is similar section of a motor revers- Figs. 1 and 2 and the diagram Fig. 4 illustrate a motor that without changing the position of its drive shaft or inlet and discharge ports is adapted to operate in either direction as a variable speedtorque motor.

The motor comprises a housing I that is practically square with the cylinder heads or end plates 2, 3 on either end. Oil under pressure is admitted to the motor through port 4 in the housing I and discharged through port 5. The rotor 6 consists of the two steel headers 1 and 8, Fig. 2, which are formed in one piece with the 'shafts 9, Il respectively. Three triangular segments II, I I, Il are equally spaced about the periphery of the headers and the three parts are fastened together with bolts I2, I2, I2. The completed rotor contains three slots, formed by the segments, in which the compound rollers I3, I3,

roller is that one element rolls on the bore of the cylinder while other elements roll on the rotor slot but neither element touches both the rotor and cylinder bore. 'I'he rollers I3, I3, I3 are held in substantial contact with bore Il of the cylinder by means of a fourth" roller 20 in the center of the rotor that rolls in contact with the rollers I4, Il, I4. Fluid under pressure is preferably fed into the center of the rotor by passage 2l from the inlet port that registers vwith the annular groove 22 turned on one or both headers and reaches the center through holes 23, 23, 23. A- number of constructions of rotors and rollers are described in my copending patent applications Ser. Nos. 356,248 and 356,249.

'I'he motor, as shown in Fig. 1,' runs clockwise and develops maximum torque at lowest speed for the rotoris in its nearest position to the top of the cylinder in which it will use the maximum amount4 of fluid per revolution. The cylinder Il 'f l2li between the housing 'I and block I8 through" pipes 26 and 21 respectively to move the block I8, in relation to rotor and housing I. The rollers positions radially in the rotor slots. Fluid admitted presses the roller forward at the bottom of the cylinder by the energy represented by the pressure multiplied by an effective area of one half of the diameter of the roller multiplied by its length, while, at the same time, the roller just entering the inlet port presses in the opposite direction with equal energy but the iirst roller delivers its pressure at a point on the rotor slot further from the center than the second roller does, so the rotor turns clockwise.

Fig. 7 shows the motor at its maximum torque and lowest speed in clockwise -rotation, with the block I8 in contact with the stop 28 on the cylinder block; in Fig. 8 fluid admitted into space 24 has lifted the cylinder'block away from the stop 28 and increased the distance between the rotor 6 and the cylinder bore which decreases the amount of fluid used for revolution and decreases the torque but using a xed amount of iluid per minute increases the speed of the rotor. Fig. 9 illustrates a further movement of the cylinder block and consequently an increase in speed and a decrease in torque. Fig. 3 illustrates. a condif tion when the center of the cylinder and the center of the rotor coincide, and when all the rollers press on the rotor slots at the same distance from the center and the pressure is balanced and the l rotor stops. If operating as a pump there will be no discharge under these conditions.

The effect of a further movement of the cylinder block is shown in Fi'g. 10 in which the block I8 has reached the stop 29 at the top of the housing I and the rotor 6 is nearly touching the bottom of the cylinder bore. Under these conditions the motor operates at high torque and low speed in the counterclockwise rotation. The position of the cylinder block in relation to the rotor is controlled by the amount of fluid admitted or discharged from the spaces 24 and 25.

All the fluid may be admitted to the pump, Fig. 1, through passage 30 and .discharged through passage 3| (later called lay-passes) in the cyl@ inder heads 2 and 3 to serve as a .variable pump or to operate as a motor. The method of determining the shapes of these by-passes will be later described. It'is. desirable for efficiency in high .speed pump operation to avoid small passages or abrupt change of direction of the fluid in passinglttshrough the pump or the inlet and discharge por An important part of this`l invention is the provision in variable capacity pump of inlet and discharge ports in the movable cylinder block and xed inlet. and discharge by-passes in one or preferably both of the cylinder heads.

Themaximum size of the inlet 4and discharge ports and position of the by-passes in a variable capacity pump are dependent onv the number and size of the rollers, the bore of the cylinder and especially on the amount the capacity of the pump varies as that controls the movementof the cylinder block.

The method for locating these ports and bypasses, in accordance with my invention, is described for a three roller motor that is adapted to vary between full torque clockwise to full torque counter clockwise operation. All angles are based at the center of rotor (which does not change) and degrees is at the point the rotor comes nearest to the cylinder bore when in clockwise operation.

pump having three rollers, the vanes are spaced equidistantly with respect to the center of the rotor. 1f lines are drawn through the center of each slot and through the center of each roller, adjacent lines will form angles of These lines will not necessarily intersect the bore of the cylinder at the point of tangency between the cylinder and each roller except when the eccentricity is reduced to zero.

When the eccentricity is not zero, lines drawn from the center of the cylinder through the center of each roller will not necessarily make angles of 120 with respect to each other; neither will lines drawn from the center of the cylinder to the point of tangency between each roller and the cylinders make such angles. The angles in such cases may be less than 120 and approach a maximum greater than 120 during a half revolution of the rotor, the angles thereafter being reduced until the minimum is reached.

Reference hereafter to the 60, 120,180, 240, and 300 positions respectively of the rollers means the position of the roller when the line from the center of the rotor through the center of a roller makes the foregoing angles respectively, measured clockwise from the top 'of the vertical axis.

With the pump and its parts in the position shown in Fig. 1, a horizontal axis through the .center of the rotor in the plane of the drawings will divide the cylinder bore into two unequal parts.

During a half revolution of the rotor a, roller would traverse .either of said parts of the cylinder. Thus, though the speed of the rotor may be constant, the speed of the rollers would change continuously from a minimum at zero degree position in Fig. 1 to a maximum at position and then become gradually slower until the minimum is then reached at zero position.

For optimum operation of a three-roller vane pump, as shown in Fig. 1, operating in a clock- Wise direction, the upper right-hand roller should open the intake port with respect to the space between that roller, the cylinder, and the next adjacent roller, in a counter-clockwise d1- rection, at the same instant that the said next roller closes the exhaust port with respect to the same space. These cut-oft points should be when the said rollers are in the 60 and 300 positions.

Likewise when the rollers are in the 120 and 240 positions, as shown in Fig. 7, the right-hand roller should cut off the intake port and the lefthand roller open the discharge port at the same instant with respect to the space between the said rollers and the bottom of the cylinder.

The space or volume in Fig. 1 between the 60 and 300 rollers, the top of the cylinder, and the casing heads is at a minimum and gradually increases in volume during a half revolution until it is at a maximum when the rollers are in the 120 and 240 positions, as in Fig. '1.

Since the volume of the said space is continuously changing, it follows that the cut-oi! of the intake in one side must be simultaneous with the opening of the discharge in the other side, except that a very small lead or lag maybe necessary, depending on pump and fluid characteristics. If in Fig. the discharge opened before the intake closed, then the fluid would pass through without eil'ective results. If the opening of the discharge is delayed for even an instant after the closing of the intake, disas- In the case of a three-vane pump, thatis a 76 trous results will follow when a. non-compressible fluid is involved, depending on whether during that instant the space or volume between the said rollers and the cylinder is increasing or decreasing. If it is decreasing the pump or motor must stop or burst, since the fluid is incompressible. If the space is increasing, a partial vacuum will be created, followed by suction and ineiiicient displacement of uid when the port is subsequently opened, or by a hammer or poundingaction when the said space or volume is again reduced.

The same ls true when the rollers are in the position as shown in Fig. 1.

An important object of this invention is to determine the proper location of the ports for optimum operation.

A further object is to determine such ports for optimum operation in a variable capacity pump, that is, in a pump or motorwhere the capacity and operating conditions are varied by varying the eccentricity.

In the case of a variable capacity pump, ports 30 and 3| are shown in. thel casing headers which form the cylinder heads. In will be noticed that -a portiorrof the ports in the cylinder headers is covered ,by the cylinder and that this portion varies and changes as the relative position of the cylinder is changed. The intake and exhaust passages 30 and 3| in the casing headers are so located that they compensate for shifting position of cut-on so that at varying points of ad- Ajustment-that is, at varying amounts of eccentricity-the cut-oir and opening points of the ports will always be proper for the optimum operation as heretofore explained.

' The method of dening the said passages in the casing headers is hereafter fully explained with respect to Fig. 4. The method may be more easily understood if it is realized that with the rotor in any position as in Fig. 1, the point oi tangency between the upper rollers and the cyl-` inders changes as the eccentricity is varied by raising the cylinder, and the ports must be so deiined that its point of cut-E will be at the new and changing points of t-angency at all points within the limits of the movement o1' the cylinder.

The cut-oft points are lshown at 38 and 39, which correspond to 40 and 4| when the cylinder is moved to the opposite limit by raising. If the rotor is turned 180 in Fig. 1 to the position in Fig; 7, the p oints of opening and cut-off will be 34, 35. Thus the line 34, 40 and 35, 4| and corresponding lines at the tops of the ports are the paths taken bythe points of tangency between the rollers in the 60, 120, 240, and 300 positions, and the cylinder, yas the cylinder is moved from maximum eccentricity displacement in one direction as in Fig. 1, to a maximum eccentricity displacement in the opposite direction as in Fig. 10.

The ports 30 and 3| in the cylinder casing headers may be suilicient, but additional ports may be used and are shown at 32 and 33 through the cylinder and casing'.

The inlet port 32 and discharge port 33 are located in the center of the cylinder block I8 on either side of the rotor and register with the inlet port 4 and discharge port 3 in the housing The ports 32 and 33 are preferably located in the center of the cylinder block leaving -an unbroken annular ring around the cylinder on either side on which the discs, I5, l5 may roll.

The maximum size of the ports 32 and 33 is determined by locating the bottom of the ports tion, as in Fig. 7. The bottom of the ports is at the point of contact 34 and 35 of rollers at the 120 and 240 degrees positions respectively with the cylinder bore. The exact point may be determined by lines drawn from the center of the cylinder through P and Q (the centers of the rollers) respectively. The outside o! the bottoms of the by-passes 30 and 3| are also fixed at points 34 and 35 respectively.

'I'he tops of the ports 32 and 33 are determined when the motor is at full torque counter clockwise operation, as in Fig. 10. kThe centers of 60 and 300 degree rollers are indicated at Z and T1 respectively. Lines drawn from the center U through Z and T1 intersect the bore at 31 and 31a respectively which represent the tops of the ports 32 and 33 and outside point of the top of the by-passes 30 and 3 I.

The inside of the bottom of the by-passes 33 and 3| ,are `also determined from Fig. 10. The points X and Y represent the centers of rollers at 120 and 240 degrees. Lines drawn from the center of the cylinder U through X and Y intersect the cylinder bore at 40 and 4|, respectively which are the inside bottom limits of the bypasses 30 and 3|.

The inside of the top of the by-passes are located from the full torque clockwise motor position, as shown in Fig. 1. V and W represent the center of rollers at 60 and 300 degrees and lines drawn from the cylinder center H through V and `W intersect the cylinder at 33 and 39 respectively which are the inside top limits of the by-passes 30 and 3 I.

As shown in the drawings, the by-passes 30 and 3| are connected to inlet and discharge ports 4 and 5 through the cylinder ports 32 and 33 respectively but they may be connected directly through the cylinder heads with the source of fluid under pressure.

It is apparent that the cylinder ports 32- and 33 are always fully open irrespective of the position of the cylinder block but the by-passes are partly covered by the movement of the cylinder block, for example in Fig. 1 the top of the bypasses are closed by the cylinder. The cylinder ports 32 and 33, while they probably supply a major portion of the uid to the pump could not operate the variable motor alone. Again referring to Fig. 1 it is apparent that there has been a minor amount of fluid discharged through bypass 3| from in front of the 300V degree roller after this roller passed the top 31a of the discharge port 33. 'I'he movement of the cylinder block in the housing uncovers the top and bottom of the by-passes to admit fluid to an expanding area (formed by two rollers, the rotor and cylinder bore) and to receive fluid from a contracting area.

The shape of the top and bottom of by-passes 30 and 3| are shown in Fig. 4 which is a diagram of a half of motor showing the relationof the cylinder bore is shown by 1, the position when the rotor is at full torque, clockwise rotaof discharge port in the cylinder is indicated by the space between I-I, the positions of the upper and lower ends of by-passes are deter- The second position of the cylinder, as shown in Fig. 8, which develops reduced torque with clockwise rotation is represented by letter J" and position of discharge port by the space J -J, and so forth.

The third position of the cylinder, as shown in Fig. 9' develops less torque still with clockwise rotation is represented by letter K with the positions of ports and by-passes determined as above.

Fourth position of the cylinder with its center and center of rotor coinciding, as illustrated in Fig. 3, shows the rotor on ,"dead center and stationary. Position of ports and by-passes are represented by L. The lines from L to its cylinder bore coincide with 240 and 300 degree lines.

Fifth position of the cylinder is represented by M with the center of the cylinder above the center of the rotor and motor operating counterclockwise under reduced torque. `Position of ports are determined in the same manner.

Sixth position of the cylinder, as shown in Fig. 10, represents the motor at full torque in counterclockwise operation and is represented by letter "N. Position of ports and by-passes are determined in the same manner.

Any number of positions of the cylinder in relation to the rotor may be used to plot the points of contacts between the cylinder bore and the rollers at 60, 120, 240 and 300 degrees from the rotor center, lines drawn through these points determine shape of top and bottom of 'by-passes in the cylinder heads. The line of the top and bottom of the recesses curves slightly down to the common center position L when the angle changes materially for the reverse positions.

Fig. 3 illustrates a pump or motor that does not reverse but is adapted to vary between full torque as a motor or high pressure as a pump to a dead center position in which a motor would stop and a pump discharges no tluid. The upper end of cylinder discharge port 33 and the outside of the top of the by-pass 3l are located when the rotor is at the dead center position in which the centers of both the rotor and the cylinder coincide at R, by a line RS (S is center of a roller I3 at the 300 degree position) to the cylinder at 36, while the line R1S1 from the center of the rotor at full torque clockwise r0- v tation through the center of the 300 degree roller I3 to 42 at inside of the top of the by-pass determines the top of the discharge by-pass 3|. recess 3i is located by line RTz from common center at dead center through the center '4F32 of a roller at the 240 degree position to point and the outside of the bottom of by-pass 3l are determined with the cylinder and roller (thin line in drawings) in the position for full torque clockwise rotation. A line drawn through R1 the cylinder center, and T2 the center of a 240 degree roller locate the bottom of the cylinder discharge port 33 and the outside of the bottom of the bypass 3| at 44. 'Ihe rollers are held against the cylinder bore by center roller 20 when rolls on the roller I4 which contacts the rotor slots. Fluid under pressure is led into the center of the rotor from inlet port I in case of a motor or dis- `charge port 5 in case of a pump through passage 2|, Fig. 1, through the cylinder head and into `the ring groove 22 on the outside of the rotor header 8 and through holes 23,- 23 into the center of the rotor.

In place of admitting fluid underv pressure to The inside of the bottom of the The position of bottom of cylinder port 33 either side of the cylinder block in order to vary the position of the cylinder, I may use any mechanical means, such as screws, springs, etc., known to this art without departing from my invention.

While the form of apparatus herein described constitutes a preferred embodiment of my invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims,

What is claimed is:

1. A variable capacity pump for non compressible fluids comprising a casing having heads on both ends, inlet and discharge ports in opposite sides of the casing, a movable block fitting between the sides of the casing which contain the said ports, a cylinder bored in the said block, a rotor journaled in at least one of the heads and adapted to revolve in the cylinder, a plurality of slots in the periphery of the rotor, a roller in each of the said slots, means for moving the cylinder block in relation to the rotor for varying the capacity of the pump, xed inlet and discharge ports in the cylinder block connecting respectively with said inlet and discarge ports in the casing to admit and receive the major part of the fluid from the pump, and inlet and discharge passages in at least one head which, in conjunction with the position of the cylinder block, admit fluid from the inlet port in the cylinder block to all expanding areas within the pump while expanding, and allow fluid to escape through the discharge port in the cylinder block from all contracting areas while contracting.

2. In a hydraulic machine, a block having a cylinder therein movably supported in a casing provided with end plates, a rotor having a plurality of movable roller vanes therein andl journaled to rotate eccentrically within said cylinder to form a plurality of variable capacity chambers within said cylinder during rotation, means to move the cylinder to vary the eccentric relation between the rotor and the cylinder, inlet ports in said cylinder and casing to admit iluid to said chambers, discharge ports in said cylinvder and casing to discharge iiuid from said chambers, auxiliary inlet and discharge passages in at least one of said end plates controlled by the movement of said cylinder block and adapted to permit passage of uid from the inlet port in'said cylinder to said chambers while expanding and to permit discharge of Iiuid through the discharge port in said cylinder while contracting.

3. A variable capacity pump for non-compressible fluids comprising a casing having heads on both ends and inlet and discharge ports in the opposite sides of the casing, a movable block fitting between the sides of the casing which contain the said ports, a cylinder bored in the said block, inlet and discharge ports in opposite sides of said .cylinder in partial registry respectively with the inlet and discharge ports in`said casing, a rotor journaled in at least one of the heads adapted to revolve in the cylinder, a plurality of spots in the periphery of the rotor, a roller in each of the said slots adapted to roll on the cylinder bore, means for holding the rollers against the cylinder bore, means for moving the cylinder block in relation to the rotor to vary the capacity of the pump, and inlet and discharge passages located in at least one of said heads and adapted to admit fluid from the cylinder inlet port to all expanding spaces within the pump while expanding and to allow fluid to escape through the cylinder discharge port from all contracting spaces within the pump while contracting.

4. A variable capacity pump for 'noncompressible fluids comprising a casing having heads on both ends, 'inlet and discharge ports in the opposite sides of the casing, a. movable block tting between the sides of the casing which contain the said ports, a cylinder bored in the said block, inlet and discharge ports in opposite sides of said cylinder in partial-registry respectively with the inlet and discharge ports in said casing, a rotor journaled in at least one of the heads adapted to revolve in the cylinder, a plurality of slots in the periphery of the rotor, a roller in each of said slots adapted to roll on the cylinder bore, means for holding the rollers against the cylinder bore, means for moving the cylinder block in relation to the rotor tovary the capacity of the pump, and inlet and discharge passages in at least one head which, in conjunction with the position of the cylinder block, admit fluid from the cylinder inlet port to all expanding spaces within the pump while expanding and allow iluid to escape from the cylinder discharge port from all contracting spaces within the pump while contracting. y

PERCY D. BREWSTER.

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