USRE21758E - Power transmission - Google Patents

Description

April 1, 1941. G. A. FOISY POWER TRANSMISSION Original Filed March 12, 1936 INVENTOR 6505 05 A. FOISY ATTORN EY Reissued Apr.- 1, 1 941 I POWER TRANSMISSION George L Foley, New Haven, Conn, ass gnor to The Waterbury Tool Company, Waterbury, Conn., a corporation of Connecticut Original No. 2,114,443, dated April 19, 1938, Serial No. 68,433, March 12, 1936. Application for reissue January 31, 1940, Serial No. 316,593

s Claims.

This invention relates to power transmission devices and more particularly to those of the fluid type utilizing a variable displacement pump. It is an object of the invention to provide a variable speed fluid power transmission wherein a variable displacement pump is incorporated and in which means are provided for varying the displacement of the pump for automatically maintaining a constant fluid pressure in the discharge line from the pump.

A further object is to provide a displacement regulator for a variable displacement pump wherein fluid pressure motor means is utilized for operating the displacement varying mechanism under the control of a small pressure responsive pilot valve.

A further object is to provide a control of this character which has a rapid response to sudden changes 01' operatingconditions and which employs simple and reliable mechanism which is economical in cost.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing:

pistons 24 will have zero stroke while if the tilting box 28 be tilted clockwise to its full movement, the stroke of the pistons 24 will be at maximum. 1

Fluid is delivered to and from the cylinder- The mechanism thus far described is well known in the art by itself and forms no part of the present invention.

In order to regulate the position of the tilting box 28 and consequently the displacement of the pump l8, there is provided a pair of aligned cyl- Fig. 1 is a longitudinal cross sectional view of a in a variable displacement pump adapted to form a part 01 a variable speed fluid power transmission. The pump II is illustrated as of the well- .known Waterbury type, although it will be understood that the invention may be applied to [variable displacement pumps or motors, of any construction. A motor l2 drives a shaft ll of the pump ill which in turn rotates a cylinder barrel l8 through the medium of keys I8 and also rotates a socket ring through the medium of a universal joint 22. Pistons 24 reciprocate in the bores of the cylinder barrel I8 and are articulated .ito the socket ring 20 by means of ball-ended connectiug rods 26. The socket ring 20 is iournalled in a tilting box 28 pivotally mounted on trunnions 30 for a limited movement clockwise from the position illustrated in Fig. 1. g The stroke of the pistons 24 and consequently the displacement of the pump may be varied by moving the tilting box '28 on its trunnions-88.

Thus. if the tilting box be maintained in the posi socket ring 20 perpendicular to the shaft II, the

'tion illustrated, that'is, with the plane ofthe inder bores 36 and 38., the bore 38 having a some- .what larger diameter than the bore 38. A sliding control member 40 carries pistons 42 and 44 at its opposite ends which are a fluid tight, sliding fit within the bores 38 and 38 respectively. The control member 40 is connected to operate the tilting box 28 by means of an arm 46 rigidlysecured to the tilting box having a sliding and pivotal connection with the control member 40 at 48.

The space below the piston 44 in the cylinder bore 38 communicates by means of a passage 88 with the delivery port of the valve plate 32, this passage being permanently open and unrestricted. The space above the piston 44 in bore 38 and below the piston 42 in bore 36 communicates with the interior of pump casing 52 through an ample clearance space around the control member 48. A conduit 54 connects the lower end of cylinder bore 38 with the upper end of cylinder bore 36 and has acheck valve 58 at one end and an adjustable restriction L at the other end. Communicating with the upper end. of the bore I I8 is a bleeder passage 68 which is under the control of a valve 82 for varying the quantity of fluid passing from the passage 60 to a filia'mber' 64 which opens to the interior of the casing 52. Valve 82 is biased to the right in Fig. 2 by a spring 56 which is adjustable by means of a screw threaded abutment member 68.

Above the piston 42 there is formed-a chamber .1. which is in communication with the upper end if; the cylinder 38 at all times through an opening 12. A cover I4 closes'the upper end of the chamber 10 and carries a bellows l6 and stop means II limiting its expansion. A connection ll is provided for filling the interior of the bellows II with compressed air or other elastic fluid medium.

In operation of theydevice, the pump ll being connected to a suitable load device which requires the delivery of fluid at variable rates of flow and at constant pressure; the motor I2 is started and the cylinder barrel I 8 and. socket ring Ill thus caused to rotate at a constant speed. The pressure maintained in the delivery port of the valve plate 32 is transferred to the piston 44 through the conduit III. A counter-balancing pressure is maintained on top of the piston 42 by a small quantity of fluid flowing through the conduit 54 to'the upper end of the cylinder bore 36. This quantity is initially regulated by the adjustable restriction II which. when once set, may remain flxed thereafter. The spring 68 is adjusted by means of the adjustable abutment It to open the bleeder passage 80 to the pump casing through passage 84, at a pressure somewhat under the amasresponse of the device to sudden changes in flow pressure which it is desired to maintain in the discharge conduit.

When the pressure is maintained at the desired value in the discharge conduit and the quantity of fluid taken by the load device is constant, the control member 40 will be maintained in a position such that the displacement of the pump in is equal to the quantity required by the load device. Under these conditions, the valve 62 will be maintained open to a degree Just suiiicient to pass the same quantity of fluid which is permitted to pass the restriction ll; Thereafter when the quantity of fluid taken by the load device decreases, the flrst eflect is to build up a slightly increased pressure in the delivery port of valve plate 32 since the displacement of the pump momentarily remains flxed at a greater value than the quantity taken by the load device. This increased pressure is transmitted through the conduit II to the piston 44 which in turn transmits the increase in pressure to the fluid above the piston 42, thus opening the valve 62 wider to bleed more fluid to the interior of the casing 52. Under these conditions the control member ll is permitted to move upwardly and decrease the displacement of the pump I ll since fluid is now being discharged from the upper end of the cy1inder bore 38 at a greater rate than it is entering through the restriction 58. As soon as this action has taken place sufliciently to bring the pump displacement down to the value required by the load device, the pressure in the outlet port of the valve plate 32 reaches its normal value and conditions again become equalized.

'During. the operation Just described, the bellows I. which has been previously filled with compressed air or other elastic medium at a pressure substantially equal to the normal op erating pressure of the pump is maintained in the collapsed position illustrated, by the fluid pressure within the chamber ll. When the quantity of fluid required by the load device increases necessitating an increase in the displacement of the pump ID, the pressure at first falls off, in the discharge port of the valve plate 32. The elastic fluid within the bellows 10 is thereby permitted to expand, forcing fluid out of the chamber II and driving the control memberll downwardly to displace fluid from the cylinder bore 38 until such time as the displacement of the pump has been increased to the new value required by the load device.

During this operation the check valve 56 acts to prevent the back flow of fluid through the conrequirements may be made very sensitive since movement of the control member III is under the primary influence of the valve 02 which may be light and free acting. Likewise, the response is rapid in either direction of movement since the bellows Ii acts to maintain pressure on the piston 42 under all conditions. Thus, for example, were the pump operating at a small displacement and were the load requirements suddenly in ased to a value corresponding tomaximum disp acement of the pump III. the discharge pressure would fall ofl rapidly. Were it not for the elastic action of the bellows II, the response of the pump under theseconditions will be somewhat delayed due to the lack of suitable operating pressure for moving the control member 40.

While the form of embodiment of the invention of the translating device, and including a small bypass from the high pressure side of the device to a point of lower pressure and having an intermediate portion in communication with one of said piston faces, said bypass being continuously open when the piston faces are stationary and including a resiliently biased valve and a fixed restriction one of which controls the inlet to said one piston face and the other of which controls the outlet therefrom, said valve being responsive to a predetermined increase or decrease in the operating fluid pressure on said pressure responsive means, for unbalancing said piston faces in a manner to move the displacement varying means in the direction tending to counteract said change, whereby the displacement varying means may be brought to and maintained stably in the position corresponding to any load requirement.

2. In a fluid pressure energy translating device the combination of means for varying the eiiective displacement of the device, a pair of oppositely acting, normally balanced piston faces operatively associated with the displacement varying means, conduits connecting each piston face with one side of the working circuit of'the trans: lating device, and including a small bypass from the high pressure side of the device to a point or lower pressure and having an intermediate portion in communication with one of said piston faces, said bypass being continuously open when the piston faces are stationary and including a resiliently biased valve and a fixed restriction one of which controls the inlet to one piston face and the other of which controls the outlet therefrom, said valve being responsive to a predetermined increase or decrease inthe operating fiuid pressure on said pressure responsive means for unbalancing said piston faces in a manner to a'mss move the displacement varying'means in the diconduit to one piston being unobstructed, a. conduit for bleeding fluid from the other piston, a valve responsive to pressure changes on said pistons and arranged to control the bleeding of fluid from the other piston, a flxed restriction in the conduit between the outlet of the pump and the other piston, said valve and restriction being in series between the high pressure side of the de vice and a point of lower pressure, and resilient, fluid displacing means for maintaining pressure on the other piston when the outlet pressure of the pump tends to fall of! suddenly, whereby the normal quick response or the pressure responsive 1 A 3 6. In a variable displacement pump the combination of means for varying the elective displacement of the pump. a pair of pistons for operating said means, a conduit connecting each of said pistons with the outlet of the pump, the conduitv to one piston being unobstructed, a conduit for bleeding fluid from the other piston, a valve responsive to changes in the pressure et- .fective on said pistons, and a fixed restriction,

one ofwhich is located in the inlet conduit to the other piston and the other of which is located in the outlet conduit from the other piston, said valve and restriction being in series between the high pressure side of the device and a point of lower pressure, said pistons acting to take up a stable position whereby the pump displacement is automatically adjusted to the value corresponding to any requirement made on the pump, and energy-storing means for maintainmeans is maintained regardless of pressure conditions in said circuit.

4. In a variable displacement pump the combination of means for varying the eiiective displacement of the pump, a pair of pistons for operating said means, a conduit connecting each of said pistons with the outlet of the pump, the conduit to one piston being imobstructed. a conduit for bleeding fluid from the other piston, a valve responsive to changes in the pressure elective on said pistons, a fixed restriction, one of which is located in the inlet conduit to the other piston and the other of which is located inthe outlet conduit from the, other piston, said valve and restriction being in series between the high Pressure aided the device and a point of lower pressure, and an air chamber for maintaining pressure on the other piston when the outlet pressure 1 of the pump tends to fall ofl suddenly, whereby the normal quick response of the pressure responsive means is maintained regardless of pressure conditions in said circuit.

ing force on the other piston when the outlet pressure of the pump tends to fall oil suddenly, whereby the normal quick response of the pistons is maintained regardless of pressure fluctuations I in the outlet of the pump. I

"I. In a variable displacement pump having a,

horizontaldrive shaft projecting centrally from one side thereof, the combination of means for varying the effective displacement of the pump, a pair of diflerenttal pistons extending perpendicularly to said shaft at one side thereof for operating said means, a conduit connecting each of said pistons with the outlet of the pump, the

conduit to the smaller piston being unobstructed, a conduit for bleeding fluid from the larger piston, a valve responsive to pressure changes on said diflerential pistons and arranged to control the bleeding of fluid from the larger piston, a

' flxed restriction in the conduit between the out- 5. In a variable displacement pump the com- I I bination of means for varying the efl'ective discated in the inlet conduit to the largerpiston' let of the pump and the larger piston and resilient, fluid displacing means for maintaining pressure on the larger piston when the outlet pressure oi the pump tends to fall ofl' suddenly, whereby the normal quick response of the pressure responsive means is maintained regardless of pressure conditions in said circuit.

8. In a fluid pressure energy translating device the combination of means for varying the effective displacement of the device, normally balanced, pressure responsive means including a piston operatively associated with the displacement varying means, conduits connecting said pressure responsive means with oneside of the working circuit of the translating device, and means including a resiliently biased valve and a fixed restriction one of which controls the inlet to said piston and the other of which controls the outlet therefrom, said valve and restriction balauciugsaidnieansinamannertoiuovethe displacement varyin means in the direction tending to counteract said change.

Gml A. I'OIBY.

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