US2344517A - Adjustable stroke pump - Google Patents

Description

21, 1944.. s SCHNELL 2,344,517

ADJUSTABLE STROKE PUMP Filed June 8, 1942 2 Sheets-Sheet l INVENTOR ATTORNEY arch 21, 1944. s, sc-HNELL 2,344,517

ADJUSTABLE STROKE PUMP Filed June 8,- 1942 '2 Sheets-Sheet 2 5Q 45 &

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TO z S. SC LL BY Mm Patented:Mar. 2 1.1944

JUSTABLE STRQKE PM Steve Schneli, Kirkwood, Mo., assignor to Wagner- Electric Corporation tion of Delaware st. Louis, .Mo., a corpora- Application June 8. 1942, Serial No. 446,187

I 11 Claims. (Cl. 103173) My invention relates to pump'for developing. fluid pressure and more particularly to means for adjusting the stroke of the 'i'eciprocable element or elements thereof.

One of the objects of .my invention is to provide ina pump having are'ciprocable pressure developing element, improved means for adjusting the length ofthe stroke thereof.

, Another and more specific object of my invention is to provide stroke adjusting means in a well-'mown manner by a rotating shaft ll journaled in the housing I. The inner end of this shaft lies in compartment 3 and carries an actuating roller i8 pivotally mounted on a pin ii of the shaft which has its axis at right angles to the axis of rotation of said shaft. The exterior end of the shaft has secured thereto -a for the reciprocable elements of a reciprocating pump of the swash plate type having meansassociated therewith for controlling the conditioni-ng of the swash plate in order to make the pump operative or inoperative.

Other objects of my invention will become sectional view taken on the line 3-3 of Figure 2; and Figure 4 is a sectional view of.a portion means is embodied.

Referring first to Figure 2, there is disclosed a reciprocating pump of the swash plate type which is enclosed within a housing I having compartments 2 and 31 therein filled with a suitable liquid. A second casing t carries a plurality of reciprocating pumps generally indicated by the numeral 5. These pumps may be of any number desired and are equally spaced clrcumferentially about a common axis. Each pump comprises a cylinder 6 having, reciprocable therein a piston I! provided with a passage 8 for admitting fluid from compartment. 3 to the compressing chamher 9 ahead of the piston. The piston passage is controlled by a check valve I0 in order that fluid may be trapped in the compressing chamher during the forward movement of the piston.

The compressing chamber has an outlet passage 'ill' controlled by a check valve structure l2 for preventing return flow of fluid to the compressing vchamber after it is once forced out of said chamber. The pistons l of the pumps have ball and-socket connections M with a swash plate I t pivotally mounted at its center by a ball and of a pump in which a-manual stroke adjusting pulley 20 so that the shaft can be driven by a belt from a suitable source of power.

of the pump. Thus if this piston should be in the position shown, the pumps will not be operated by the rotation of shaft l1 since the swash plate can then'assume a position at right angles to the axis of the driving shaftf However, if piston 16 is moved to the.right, this will move the center of the swash plate toward the shaft and thereby cause it to be tilted, that is, lie in a plane other than a plane which is at right angles to the axis of the driving'shaft. This shaft ll, by means of roller l8, will cause the swash plate to wobble back and forth as the roller moves around the surface of the swash plate. This causes the pistons of the pumps to be reciprocated and consequently force fluid under pressure past the outlet valves l2.

The pumps may be employed to develop fluid pressure for use in any type of fluid pressure actuating system. The piston I6 may be controlled in various manners so that the pumps will be operative or inoperative as desired. How- 'ever, by way of example, I have shown the pumps associated with a fluid pressure actuating' system wherein the pumps are adapted todevelop fluid pressure to actuate a brake and to be controlled by fluid pressure developed man- As shown in Figure ,1, the system comprises a master cylinder device 2| which has a cylinder 22 and a reciprocating piston 23, said piston being operated by a piston rod 24 and a pedal 25. Thepiston is normally held in its retracted position by a spring 26 which uncovers a porthole 21 for placing the cylinder in communication with a; reservoir 28 when the piston isin its inoperative position.

The reservoir 20 is connected to be in constant I I communication with compartments 2 and 3 of socket connection [5V to a movable member It which is in the form of a piston. v The swash plate i4 is adapted to be actuated the pump by means ofa conduit 29 The outlet of the master cylinder device is connected by way of conduit 30 to casing 4 to control'piston I6 and a conduit 3| leads from the outlet of $118 p' gnps to fluid motors 32 of brake assem- The movable member or piston 16 is adapted to control the operativeness and inoperativeness being larger pressure will maintain and i6 will be moved to the leftto their original positions. This will permit the swashplate larger than and axially aligned with the cylinder in which piston i6 is mounted. Within cylinder 34 is a piston 36 formed as an integral extension of piston l6. Between the pistons 36 and i6 is a chamber 36 which is in constant communicatlon with the outlets of the pumps by means of passages 31. This chamber is also in constant communication with conduit 3| leading to the fluid motors, said communication being by way of passage 38, the end of a'cylinder 33 (to be referred to later) and a passage 43. 'A packing cup 4i seals the piston i6 and a packing cup 42 seals piston 36, said cups preventing fluid under .pressurefrom passing the pistons from chamber 36. The cup 42, however, does permit fluid to pass piston 36 in a direction so that fluid under pressure may flow from conduit 30 to chamber 36. This flow is permitted by the collapse of the cup lip and it is facilitated by passages 43 in piston 36.

The cylinder cylinder 44 by way of a passage 46, said cylinder than the previously mentioned cylinder 39 and forming a continuation thereof; Within cylinders 44 and 33 is a two-diameter piston 46 having a passage 41 therethrough. The small end of the piston" is provided with a valve portion 48 for cooperation with a valve seat 43 so that the passage 41 can be cut of! from com- 'munication with cylinder 33 and consequently with conduit 3| which communicates with said cylinder. A spring 66 biases the valve portion 43 to a seated position. Suitable packing cups 6| and 62 prevent fluid from flowing past rection. It is seen that with the pump associated with a fluid pressure system in the manner described, when the master cylinder device is actuated to develop fluid pressure,this pressure will act upon the large piston 36 and thus force piston ii to the night to cause the swash plate to be actuated. thereby bringing the pumps into operation'so as to develop fluid under pressure. This fluid under pressure will be forced into chamber 36 and from :4 communicates with another to againassume a position wherein it will no longer be actuated by the roller on the driving shaft il. Consequently, no more fluid pressure will be developed in the pumps. 4

when it is desired to release fluid pressure in the fluid motors, all that need be 'done is to release the master cylinder device. There will then be a drop in fluidpress-ure in cylinder 44, thereby resulting in the two-diameter piston 46 being moved to the left to unseat the valve portion 46. This will open up passage 41 and fluid can then return to the master cylinder device where it will enter reservoir 23 and push fluid back up into compartments 2 and 3 associated with the pump.

It is desirable in a swash plate driven pump to v be able to control the stroke of the pistons so that the volume of fluid pumped can be maintained at a desired value. When the driving shaft ll of the pump is driven at variable speeds. the only way-this can be done is to provide an automatic means for varying the stroke of the pumping pistons. To maintain ,a constant volume of fluid pumped, the' stroke of. the pistons must be decreased for an increase in shaft speed. I have accomplished this in the pump shown in Figure 2 by means of an adjustable means automatically t p riphery of the two-diameter piston in either di-' controlled by a governor.

Referring to Figures 2 and 3, a rod 63 is slidably mounted in the driving shaft l1 and has its inner end 64 positioned adjacent the central part of the swash'pla'te. The other end of this rod is rounded and adapted to cooperate with cam surfaces 66 and 66 formed on pins 61 and 63,

respectively, slidably carried on' -the pulley and shaft. These pins are parallel with each other and one end of pin 61 has a weight 63 secured thereto and the opposed end of pin 63 has a weight 66 secured thereto. Since these weights there out into conduit 3| and the fluid motors 32 to thus cause actuation of the brakes. The valve 43 will be held seated due to the pressure of the fluid from the master cylinder acting upon device. If the ratios of theseareas are taken as two to one, then the pressurein the fluid motors will always be twice that of the pressure developed in the master cylinder device. In orlie on opposite sides of theaxis of the shaft, they will move the pins outwardly and relatively to each other under the action of centrifugal force.

A spring 6| is connected to oppose the outward movement'of the weights.

Thus with the automatic adjusting structure shown, the greater the speed of the shaft, the farther rod 63 will be moved inwardly. Since the inner end 64 of the rod lies adjacent the central part of the swash plate, it will control the angle of tilt of the swash plate, which tilt determines der to maintain valve 43 seated and prevent the fluid under the higher pressure from being in communication with the fluid under lower pressure, the two-diameter piston 46 also has substantially the same ratio as the ratios of. the areas of piston 36. Thus under condiflons where flfty pounds per square inch of fluid pressure is developed by the master cylinder device, this piston IS in such a tion that the pumps will continue to be operated until they develop one hundred pounds per square inch of pressure. When this occurs, pistons 36 the stroke of the pistons, and thus it is seen'that the stroke of each piston can be varied. If we assume, for example, that the Weights 63 and 63 will not move outwardly when the speed of the shaft is under four hundred revolutions per minute then the stroke of thepumps'wili be a maximum for speeds under this flgure, this stroke being determined by the distance between the end of rod 64 and the central surface of the swash plate when the swash plate is in its vertical position as shown in Figure 2. With a shaft speed of four hundred revolutions per "minutethe pumps will pump a certain volume offluid. As the speed of the driving shaft increases, the

' weights 63 and 63 will move outwardly, thus moving rod 63 inwardly. This inward movement of rod 63 will push the center of the swash plate to the left, consequently decreasing the stroke of the pistons. With shorter strokes at higher shaft speed the volume of fluid pumped will remain approximately the same as it was with the longer stroke and the lower shaft speed.

Thus it is seen that when the pump i driven by a source of power which has a variable speed, the pump, nevertheless, can be caused to pump substantially constant volumes for a unit of time.

If the pump shaft should be driven by a power means having a constant speed, it, of course, will not be necessary to have any automatic means for adjusting the stroke of the pump pistons. However, there should be manual adjusting means provided so that the volume of fluid being pumped for a given speed can be changed. The manual adjusting means shown in Figure 4 can be employed to accomplish stroke adjustments. Referring now to this figure, the pumping structure is the same as previously described. However, in place of rod 53 there is substituted a rod 3' which has a threaded end 62 cooperating with threads 63 in the end of shaft H. A screwdriver receiving slot 64 is provided in the outer end of the rod for turning the rod and thus move it axially with respect to shaft i1 so as to vary the amount of tilt of the swash plate. The outer end of the rod has cooperating therewith a threadednut 65 which acts both as a protecting means and a locking nut to hold the rod in adjusted position.

With this. manual adjusting means it is seen that if the driving shaft is being rotated at a constant speed, as, for example, six hundred revolutions per minute, the swash plate can be adjusted so that the stroke of the pumps will pump.

a given volume of fiuidper interval of time. If the driving shaft should have a speed of only four hundred revolutions per minute and the same volume is desired to be pumped, then an adjustment can be made so as to cause the pumps to have a longer stroke.

Being aware of the possibility of modifications in the particular structure herein described without departing'from the .iundamental principles of my invention, I do not intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a pump of the swash plate type, a pin-- rality o1 reciprocable circumferentially spaced pistons, a swash plate pivotally mounted at its center and connected to the pistons adjacent its periphery, a rotatable driving member for the swash plate, means for moving the pivot of the swash plate from a position where the swash plate is not actuated by its driving member to an actuated position, a stop for limiting the movement of the swash plate, and means for adjusting the position of the stop.

2. Ina pump of the swash plate type, a plurality of reciprocable circumferentially spaced pistons, a swash plate pivotally mounted at its center and connected to the pistons adjacentits periphery, a rotatable driving member for the swash plate, means for moving the pivot of.the

swash plate from a position where the swash plate is not actuated by its driving member to an actuated position, a stop for limiting the movement of the swash plate, and means for auto-- matically adjusting the position of the stop in accordance with the speed of, the rotatable driving member.

3. In a pump of the swash plate type, a plu rality of reciprocable circumferentially spaced pistons, a swash plate pivotally mounted at its center and connected to the pistons adjacent its periphery, a rotatable driving member for the swash plate, means for moving the pivot of the swash plate from a. position where the swash plate is not actuated by its driving member to an actuated position, a stop for limiting the move ment of the swash plate, and means for automatically adjusting the position of the stop in ac- 5 cordance with the speed of the rotatable driving member, said last named means comprising move able weights mounted on the driving member and movable by the action of centrifugal force.

4-.In a pump of the swash plate type, aplurality *of reciprocable circumferentially spaced pistons, a swash plate pivotally mounted at its center and connected to the pistons adjacent its periphery, a rotatable driving member for the swash plate, means for moving the pivot of the swash plate from a position where the swash plate is not actuated by its driving member to an actuated position, a-member carried by the driving member and positioned to be engaged by the central'part of the swash plate and'provide a stop therefor when moved to the actuated position,

and means for'adjusting the position of the stop member. I I

5. In a pump, a plurality of parallel cylinders arranged about a central axis, pistons in the cyl-; inders, means for reciprocating the pistons including a rotatable driving member and a swash plate having a piston actuating position in which it is tilted with respect to a plane normal to the axis of the rotatable driving member, and means 0 responsive to the speed of the driving member for varying the angle of tilt.

6. In a pump, a plurality of parallel cylinders arranged about a central axis, pistons in the 'cylinders, means for reciprocating the pistons including a rotatable driving member and a swash plate having a piston actuating position in which it is tilted with respect to a plane normal to the axis of the rotatable driving member, a stop for limiting the angle of tilt, means for moving the swash plate to the tilted position as determined by the stop, and means for adjusting the position of the stop to ther'by vary the angle of tilt.

' 7. In a pump, a plurality of parallel cylinders arranged about a central axis, pistons in the cylinders, a swash plate pivotally mounted at the central axis and connected to actuate the pistons, a driving shaft having a part rotatable in a fixed circular path and so engageable with the swash plate as to cause the swash plate to be wobblederate with the swash plate at its pivot for adjusting the relative axial positions of the pivot of the swash plate and the swash plate engaging part on the shaft to thereby vary the stroke of the pistons. 8. In a pump, a plurality of parallel cylinders arranged about a central axis, pistons in the cylinders, a swash plate pivotally mounted at the central axis and connected to actuate the pistons, a driving shaft having a part rotatable in a fixed circular path and so engageable with the swash plate as to cause the swash plate to be wobbled and sequentially reciprocate the pistons, and.

means for adjusting the relative axial positions of engaging part on the shaft to thereby vary the stroke of the pistons, said adjusting means comprising a rod carried by the shaft having an end engaging with the swash plate at its pivot for moving its pivot and means for moving said rod;

9. In a pump, a plurality of cylinders and pi tons grouped about a'central axis and adapted to [develop fluid under pressure, a swash plate pivoted at its center and. connected to the piston at radially spaced points, arotatable driving memthe pivot of the swash plateand the swash plate her for actuating the swash plate, fluid pressure operated means for moving the pivot of the swash plate to a position where it can be engaged and wobbled by the driving member to operate the pistons, and adjustable stop means associated with the swash plate for varying the position the pivot or the swash plate is caused to assume by the fluid pressure operated means.

10. In a pump, a plurality of parallel cylinders arranged about a central axis, pistons in the cyl-- inders, a swash plate for actuating the pistons, means for pivotally mounting the swash plate on the central axis, 'a rotatable element having a fixed circular path of movement for directly cooperating with the peripheral portion of the swash plate radially outward of its pivot, and means carried solely by the rotatable element and cooperating with the swash plate at its pivot for ad- I lusting the position of the pivot 01 the swash and means carried solely by the rotatable element vthe operative angle of the swash s'ravnscnnmh'.

and responsive to the speed of the rotatable element for-adjusting the position the movable member and pivot of the swash plate may assume with respect to the rotatable element to thereby vary stroke of the pistons.

to the rotatable element to plate and the

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