US2206305A - Pump or motor - Google Patents

Description

July 2, 1940. E. ROSE ET AL 2,206,305

PUMP 0R MOTOR Filed April 28. 193'! INVENTOR ED L Ross (3 srmrv E. GROSSER ATTORNEY Patented July 2, 19 40 UNITED STATES 2,206,305 PUMP on oron Edwin L. Rose, Watertown, and Christian E. Grosser, Waterbury, Conn., assign'ors to The Waterbury Tool Company, Waterbury, Comm, a corporation of Connecticut Application April 28, 1937, Serial No. 139,414 10 Claims. (Cl. 103-162 This invention relates to power transmissions and more particularly tothose of the-type comprising two or more fluid pressure energy translating devices, one of which may function as a pumpand another as a fluid motor. The invention is particularly concerned with the positive displacement type offluid pressure energy translating device wherein a plurality of pistons and cylinders are provided and in which a rotary plate valve is used for alternately connecting each cylinder to the inlet and outlet port in phase with the piston strokes. A common type of device i of this class utilizesa rotary cylinder barrel having cylinders parallel to the axis thereof and spaced on a circle about that axis together with a swash plate mechanism for causing reciprocation of the pistons as the barrel revolves. One end face of the cylinder barrel is provided with a flat surface through which cylinder ports extend to each cylinder, its surface running against a flat surface on a stationary valve plate which is provided with a pair of arcuate inlet and out-' let ports with which the cylinder ports alternately communicate in theircycle'of rotation.

It is necessary in devices of this character to maintain the cylinder barrel in close proximity to the valve plate so as to minimize leakage atthis point. It has been customary to maintain this small running clearance between the cylinder barrel and valve port by establishing a hydraulic force of predetermined ratio to the operating pressure which constantly urges the cylinder bar- ,rel against the valve plate. This has been accomplished by careful correlation between the 35 area of the surface of contact between the cylinder barrel and valve plate, the area of the cylinder and valve plate ports, and the cylinder areas. For this purpose the cylinder ports aremade a small fraction of the cylinder area so that a sub- I 40 stantial area at the end of the cylinder bore is exposed to fluid pressure tending to urge the barreltoward the valve plate.

In designing machines of this character it is desirable from certain standpoints to decrease the 4.5 ratio between the cylinder diameter and the diameter of the circle upon which the cylinders are spaced. Thus for a given overall size of the unit, a smaller piston area permits themaximum operating pressure to be increased without in- 50 creasing the bearing loads at the swash plate mechanism. Such a procedure presents one difflculty, however, in that in order to maintain f the same hydraulic balance ratio between the' cylinder barrel and valve plate, the contact sur- 55 face must be decreased to a point where the leakage ratio becomes excessive; that is, the contact surface bounding the two arcuate valve ports becomes so narrow radially in relation to its circumferential length that even though the same clearance be maintained, the leakage is propor- 5 tionally much higher. Accordingly, it is found that in the design of devices of the construction heretofore used, a definite limit of operating pressure is reached which cannot be exceeded without either overloading the bearings in the swash plate mechanism or permitting excessive leakage at the valve plate contact surfaces.

It is, accordingly, an object of the present invention to provide a fluid pressure energy translating device having a plate type of valve mechanism wherein means are provided for permitting operation at higher pressures than have been possible heretofore without either overloading the bearings or permitting excessive leakage in the valve mechanism.

A further object is to provide a cylinder barrel construction for devices of this class wherein the portion containing the cylinder ports and cooperating with the valve plate is movable indegendently of the portion containing the cylinder ores.

A further object is to provide a fluid pressure energy translating device of the character described and to provide a. cylinder barrel construction therefor wherein that portion of the cylin- 0 der barrel cooperating with the valve plate may be hydraulically balanced and may be designed to provide any hydraulic balance desired independently of the cylinder areas.

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: 40 Fig. 1 is a longitudinal crosssection of a fluid pressure energy translating device incorporating a preferred form of the present invention.

Fig. 2 is a cross section on line 2-2 of Fig. 1. Fig. 3 is a cross section on line 3-3 of Fig. 1. The device illustrated in the drawing represents a fluid pressure energy translating device of the same general type as the well-known Waterbury device and may be operated either as a pump or as a fluid motor. The mechanism illustrated is of the variable displacement type although it will be understood that the invention may be incorporated to equal advantage in devices having a flxed displacement. The device comprises a casing in having its open left-hand end closed by a valve plate l2. Journalled on bearings I4 and 16 in the casing and valve plate, respectively, is a main shaft it. The right-hand end of the shaft carries a composite cylinder barrel generally designated at 20, the barrel being so fastened to the shaft |8.as to rotate therewith. A socket ring 22 is journalled in a tilting box 24 on radial and thrust bearings, not shown, and is connected to the shaft through the medium of a suitable universal joint, not shown, so that the socket ring 22 may be caused to rotate with the shaft 3 even though the plane of rotation of the socket ring be inclined in either direction away from the perpendicular position shown .in the drawing. The inclination of the plane of rotation of the socket ring 22 may be varied by adjusting the tilting box 24 on its trunnions 26 by means of a control shaft 28 which is connected by suitable linkage, not shown, to the tilting box 24. With the exception of the detailed construction of the cylinder barrel 20 the mechanism thus far described is well known and per se forms no part of the present invention.

The cylinder barrel 20 comprises a plate 30' which is shown as being keyed to the shaft H8. The plate 30, however, may be journalled separately on bearings at its circumference located on the casing, if desired. Positioned in recesses 32 in the plate 30 are a plurality of sleeves 34 having slight radial clearance in the recesses for permitting the sleeves to properly align themselves with the other parts of the cylinder barrel about to be described. The sleeves 34 are provided with interior bores 36 within which pistons 38 are reciprocable and are articulated by connecting rods 40 to the socket ring 22. At the lefthand end of the sleeves 34 there is provided a plate-like member 42 having a plurality of cylindrlcal chambers 44 within one of which each of the sleeves 34 is telescoped. The member 42 is slid ably but not rotatably attached to the shaft l8. The member 42 has a flat surface which abuts the flat surface of the valve plate i2. Extending through the member 42 at each chamber is a cylindrical port 46 of substantially smaller area than the area of the cylindrical chambers 44. The'contact surface of the valve plate l2 appears in Fig. 2 from which it will be seen that an annular band 48 is provided and contained within this band are a pair of arcuate valve ports 50 which communicate with the supply and delivery conduits 52. Auxiliary contact pads 54 and 56 may be provided for additional bearing surface which is independent of the operating pressure as described in the patent to Durner 1,867,308.

The present invention may be utilized to greatest advantage in machine's wherein it is desired to use relatively small diameter pistons on a large diameter cylinder circle. Thus, if the radius B of the piston is less than four tenths the chord A connecting two adjacent cylinder centers, the conventional construction involves difliculty with the leakage ratio at the valve plate pressure surface. Under these conditions the annular pressure surface 48, which would exactly balance the fluid pressure forces on a conventional one piece cylinder barrel, becomes so narrow radially that the leakage or slip is excessive. By the provision of the two part cylinder barrel, the cylindrical chambers 44 may be made with a radius C greater than four tenths of the chord A, and thus the member 42 may be proportioned as desired to balance with a sufliciently wide pressure surface 48. The factor, four tenths of the chord A to .which the. radii are compared is not a critical ,46, and the ports 46 and 50.

value in the usual sense of the term, but may be considered a representative of present day practice, in that the average machine if provided with a piston radius B less than this value, will have what is considered to be excessive leakage for most purposes if a conventional one piece cylinder barrel is utilized. Obviously some pump or transmission applications may require even less permissible leakage or may permit of greaterleakage without disadvantage. In the former case it may be desirable to make use of the present invention even though the piston radius be somewhat greater than four tenths the chord A. In the latter case the conventional construction may be satisfactory with the piston radius somewhat less than this value.

In operation as a pump, the shaft I8 may be driven by any suitable prime mover causing the cylinder barrel 20 and socket ring 22 torevolve therewith. So long as the tilting box 24 is held in the perpendicular or neutral position illustrated, no fluid will be pumped through the device since the pistons will not partake of any reciprocating motion in the cylinders 36. If the tilting box be inclined from the position illustrated, the pistons will be caused to reciprocate in the cylinders 36 to an extent determined by the angle of inclination of the tilting box 24. As each cylinder port 46 passes on to one of the valve plate ports 60, the corresponding piston will begin an outward stroke drawing fluid into the cylinder 36 and chamber 44. Substantially 180 later the same port 46 passes on to the other valve port 50 and the piston begins an inward stroke discharging fluid into the second valve port 56 The quantity of fluid pumped is thus dependent on the angle of inclination of the tilting box 24.

Likewise if the tilting box beinclined on the op-" exerted in the annular areas at the left ends of the sleeves 34 is transmitted through the plate 36 and shaft l8 to the bearings l4. The member 42 is subject at any given operating pressure to the resultant of the unit pressure applied over the areas'of the chambers 44, the annular band Since the area of the chambers 44 is independent of the area of the cylinders 36,- the former and the ports 46 and 56 and the contact pressure surface 48 may be proportioned to provide any desired radial width of the band 48 on each side of the ports 50. Thus, the leakage ratio at the valve mechanism may be kept down to a reasonable value while the diameter of the cylinders 36 and the pistons 38 may be made as small as desiredwith respect to the diameter of the circle on which the cylinders are located. Thus, the loadings on the thrust bearings in the socket ring 22 and the hearings in the universal joint may be kept within safe values at higher operating pressure because of the smaller piston area without reducing the leakage ratio of the valve plate.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a fluid pressure energy translating device flO the combination of a cylinder barrel having a plurality of parallel cylinders formed therein, a piston reciprocable in each cylinder, swash plate mechanism for causing reciprocating motion of the pistons, and a valve plate cooperating with one end of said cylinder barrel to control the entry and egress of fluid to and from said cylinders, said cylinder barrel being formed in two relatively movable sections each having a series of telescoping portions communicating with each cylinder, said telescoping sections providing at each cylinder an expansible chamber having an area greater than the piston area whereby fluid pressure forces are set up tending to separate the two sections of the cylinder barrel and maintain one section pressed against the valve plate with a net force greater than that due to the thrust of the pistons alone.

2. In a fluid pressure energy translating device the combination of a cylinder barrel having a plurality of parallel cylinders disposed in spaced relation about the barrel axis, said cylinders having an internal radius not greater than four tenths of the chord of the cylinder circle extending between adjacent cylinder centers, a piston reciprocable in each cylinder, motion converting means for causing reciprocating motion of the pistons, a valve plate cooperating with an end portion of the cylinder barrel for controlling the entry and egress of fluid to and from said cylinders, a movable end plate abutting the valve plate and slidably engaging said cylinders to form expansible chambers at the end of each cylinder, said chambers having a radius greater than four tenths of the chord of the cylinder circle extending between adjacent cylinder centers.

3. In a fluid pressure energy translating device i the combination of a cylinder barrel having a plurality of cylinders disposed in spaced relation about the barrel axis, a pistonreciprocablein each cylinder, motion converting means for causinglreciprocating motion of the pistons, a valve plate cooperating with an end portion of the cylinder barrel for controlling the entry and egress of fluid to and from said cylinders, a movable end plate abutting the valve plate and slidably engaging said cylinders to form expansible chambers at the end of each cylinder, said chambers having a diameter substantially differing from the cylinder diameter, and means for limiting movement of said cylinders out of said chambers.

4. In a fluid pressure energy translating device the combination of a member having a plurality of parallel cylindrical chambers formed therein and disposed in spaced relation substantially on a circle, a valve plate cooperating with one end of said member to control the flow of fluid to and from said chambers, a plurality of sleeves slidably engaging the cylindrical walls of said chambers, pistons reciprocable in said sleeves, motion converting means for causing reciprocation of said pistons upon relative rotation between said member and valve plate, and means associated with said member for, holding said sleeves against endwise movement independently of endwise movement of said member.

5. In a fluid pressure energy translating device the combination of a member having a plurality of parallel cylindrical chambers formed therein and disposed in spaced relation substantially on a circle, a valve plate cooperating with one end plate mechanism for causing reciprocation of said pistons upon relative rotation between said member and valve plate, and means associated with said member for holding said sleeves against endwise movement independently of endwise movement of said member.

6. In a. fluid pressure energy translating device the combination of a member having a plurality of parallel cylindrical chambers formed therein and disposed in spaced relation substantially on a circle, a valve plate cooperating with one end of said member to control the flow of fluid to and from said chamberaa plurality of sleeves slidably engaging the cylindrical walls of said chambers, pistons reciprocable in said sleeves, motion converting means for causing reciprocation of said pistons upon relative rotation between said member and valve plate, and means non-rotatably associated with said member for holding said sleeves against endwise movement independently of endwise movement of said member, said sleeves engaging said last named means in a manner permitting slight misalignment between said chambers and said last named means.

7. A cylindrical barrel for a fluid pressure energy translating device comprising a plurality of sleeves having an interior bore and a cylindrical exterior surface, a member at one end of said sleeves for positioning said sleeves against endwise movement, a member at the other end of said sleeves having chambers telescopically engaged with andfreely slidable on the sleeves during operation of the device and having ports extending through the member and communicating with said chambers.

8. A cylinder barrel fora fluid pressure energy translating device comprising means forming a plurality of cylinders adapted to be closed at one end by pistons receivable in the cylinders, a movable end member slidably engaging said cylinders to form expansible chambers at the end of each cylinder, said chambers having a diameter substantially differing from the cylinder diameter, and means forlimiting movement of said cylinders out of said chambers.

9. A cylinder barrel for a fluid pressure energy translating device comprising a plurality of sleeves having an interior bore and a cylindrical exterior surface, a member at one endof said sleeves for positioning said sleeves against endwise movement, 9. member at the other end of said sleeves having chambers telescopically engaged with and freely slidable on the sleeves during operation of the device and having ports extending through the member and communicating with said chambers, said last member having a flat face surrounding said ports at their ends opposite from said chambers.

10. A cylinder barrel for a fluid pressure energy translating devicecomprising means forming a plurality of cylinders adapted to be closed at one end by pistons receivable in the cylinders, a movable end member slidably engaging said cylinders to form expansible chambers at the end of each cylinder, said chambers having a diameter substantially differing from the cylinder diameter, and means for limiting movement of said cylinders out of said chambers, said member having ports extending through the member and communicating with said chambers, and having a flat face surrounding said ports at their ends opposite from said chambers.

EDWIN L. ROSE. CHRISTIAN GROSSER.

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