US3899957A

US3899957A - Radial piston fluid translating device with cylinder positioning means

Info

Publication number: US3899957A
Application number: US408823A
Authority: US
Inventors: Jr Guy C Carlson; Willard J Haak
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1973-10-23
Filing date: 1973-10-23
Publication date: 1975-08-19
Anticipated expiration: 1992-08-19
Also published as: JPS5073203A; JPS5759915B2; GB1426148A

Abstract

A fluid pump or motor of the type having a rotor with hollow radially directed spokes each extending into a separate one of a series of cylinders that ride against an eccentrically positioned circular race as the rotor turns is provided with resilient means for maintaining the cylinders adjacent the race and in proper orientation relative thereto. This avoids possible damage from a tilted cylinder while enabling the cylinders to shift radially as necessary to accommodate to thermal expansion changes within the mechanism.

Description

United States Patent Carlson, Jr. et al.

[ 1 Aug. 19, 1975 MEANS 3,514,224 5/1970 Budecker.... 417/273 3,742,818 7/1973 Eagel v t 91/490 3,777,622 12/1973 l-lause 91/497 [75] Inventors: Gny C. Carlson, Jr., East Peoria; Primary Examiner wimam L Freeh wlnard Haak Peond both of Attorney, Agent, or FirmPhillips, Moore, [73] Assignee: Caterpillar Tractor Company, weissenbel'ger, mpio & t ala Peoria, 111. 1221 Filed: on. 23, 1973 7] TRACT 21 1 APPL 403 23 A fluid pump or motor of the type having a rotor with hollow radially directed spokes each extending into a separate one of a series of cylinders that ride against [52] US. Cl z 91/490 an eccentricany positioned circular race as the rotor [51 l lilt- Cl. F018 13/06 tunfls is provided with resilient means f maintaining [58] Field of Search 91/490, 491', 417/273 the Cylinders adjacent the race and in propel. Orienta tion relative thereto. This avoids possible damage [56] References cued from a tilted cylinder while enabling the cylinders to UN TED TATE AT T shift radially as necessary to accommodate to thermal 2,503,614 4/1950 Eynard 417/273 xp n i n ch nges within the mechanism. 2,818,816 H1958 Christenson 3,274,946 9/1966 Simmons 91 490 5 Clam, 5 Drawmg Figures 19' l2 .6 H is PATENTED AUG] 9 I975 SHEET 3 BF 3 RADIAL PISTON FLUID TRANSLATING DEVICE WITH CYLINDER POSITIONING MEANS BACKGROUND OF THE INVENTION This invention relates to fluid pumps and motors of the radial piston variety.

Certain mechanisms may be caused to function either as a pump or as a motor according to the external connections made to the mechanism. If externally driven, such mechanisms can draw fluid from a source and discharge the fluid under pressure thereby acting as a pump. Conversely, if fluid from a source is supplied under pressure, the mechanism may function as a motor. Accordingly, the structure of the present invention will hereinafter be referred to as a fluid translating device and this term should be understood to refer to either a pump or a motor or to a device which mayserve both functions at different times.

Radial piston pumps or motors constitute a compact and highly efficient class of fluid translating devices. These mechanisms employ a rotor having hollow radial spokes, each of which extends into a separate one of a plurality of cylinders. The cylinders in turn ride against a stationary circular race which is eccentrically positioned relative to the axis of rotation of the rotor. Ac cordingly. as the rotor turns, each cylinder reciprocates relative to the associated spoke and a pumping or motor action is realized depending on the nature of the fluid and mechanical connections made to the device.

As there is no fixed attachment between the rotor spokes and the cylinders, means must be provided for holding the cylinders in contact with the race. While centrifugal force or fluid pressures may perform this function under certain operating conditions, there are other circumstances under which there may not be any force urging the cylinders radially outward against the race. Gravity or negative fluid pressures may actually tend to pull the cylinders away from the race at certain times. Accordingly, it has been the practice to provide 1 a flange on the cylinders and to provide circular guide rings situated radially inward from the flanges in coaxial relationship to the race so that the flanges, and therefore the cylinder, are held in proximity to the race under all conditions.

Frictional forces resulting from the cylinders riding against the race and other effects as well may generate considerable heat. As a consequence, thermal expansion effects must be provided for to avoid binding, extreme wear and other adverse effects. If the guide ring were to be positioned to hold the cylinders tightly against the race while the device is in a relatively cold condition such as at start-up, then thermal expansion of such elements as the cylinders race and the like could cause tight clamping of the cylinder flanges against the race. To avoid this, it has been the practice to provide a small clearance between the race and the guide rings additional to the spacing needed to accommodate the cylinder flanges therebetween in a cold condition. Typically, at least several thousandths of an inch clearance are required for this purpose.

This amount of clearance is sufficient to allow significant tipping of a cylinder relative to the race and the spoke upon which it is carried. Accelerated wear or other damage may sometimes occur upon start-up of the device in a cold condition. Most notably, gouging of the leading edge of the cylinder into the adjacent race surface may occur.

SUMMARY OF THE INVENTION This invention provides a means for holding the cylinders of a radial piston fluid translating device adjacent the race thereof and in proper orientation relative thereto under all conditions while enabling self adjustment of the mechanism to accommodate to thermal expansion and contraction of components. In particular, the circular guide means which hold the cylinder flanges at the race is spaced a substantial distance inward from the cylinder flanges and resilient means are disposed between the guide means and the flanges to continually urge the cylinders towards the race.

Accordingly, it is an object of this invention to reduce wear and the risk of other damaging effects in radial piston fluid translating devices.

The invention together with other objects and advantages thereof will best be understood with reference to the following description of preferred embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. I is a cross-section view, with portions of internal elements broken out, of a radial piston fluid translating device embodying the invention,

FIG. 2 is an angled axial section view of the mechanism of FIG. 1 taken along angled line 11-" thereof,

FIG. 3 is a partial radial section view of the cylinder region of a first modification of the fluid translating device,

FIG. 4 is a fragmentary section view of the structure of FIG. 3 taken along line lV-IV thereof, and

FIG. 5 is a partial radial section view of the cylinder region of a second modification of the fluid translating device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 2 in conjunction, a fluid translating device 11 of the type to which the invention is applicable may typically have an annular outer housing 12 including an integral end member 13 and is closed at the other end by an end plate I4 secured to the housing by bolts 16. Housing 12 and end plate 14 define a chamber 17 which has semicircular portions 19 and 19' at opposite sides thereof connected by a short straight section 18.

Referring again to FIGS. 1 and 2 in conjunction, a

rotor support element 21 is secured to the center of housing end member 13 and extends axially into chamber 17 through an opening 22 in end member 13. A rotatably shaft 23 extends into the chamber 17, in coaxial relationship to rotor support 21, through an opening 24 in end plate 14 and in journaled therein by a bearing 26. The inner end of shaft 23 is journaled in a well 27 in the inner end of member 21 by an additional bearing 28. l The rotor 29 of the device 11 has an inner annular hub portion 31 which fits coaxially on the inner end of rotor support 21 within chamber 17 for rotation thereon. A spline coupling 32 at one end of the sleeve portion 31 links the rotor 29 to shaft 23 for rotation therewith.

Rotor 29 is provided with a plurality of radially directed spokes 33, of which there are seven in this example, and each of which has a central passage 34 extending therethrough. Each such spoke is further provided with a piston ring 36 secured coaxially to the radially outermost end of the spoke, the piston rings each having a convex outer surface 37 which enables each cylinder to tilt relative to the associated spoke.

An annular outer race member 38 and a relatively thin inner race member 39 fitted into the circular inner surface thereof is disposed in chamber 17 in position to encircle the rotor 29 in spaced relation therefrom. While the inner surfaces of

race members

38 and 39 are strictly circular, the outer surface of race member 38 has a curvature conforming to that of the circular portions 19 and 19' of chamber 17, but has a flattened portion 41 at the center adjacent the flat straight portion 18 of chamber 17. Accordingly, for purposes to be hereinafter described, the

race members

38 and 39 may be shifted diametrically within chamber 17 between ends 19 and 19' of the chamber. To provide for shifting of the race members in this manner and to hold such members at the selected position, circular seals 42 are disposed between outer race member 38 and housing end portion 13 and cover plate 16. As shown in FIG. 1, sealing means 43 are disposed between such circular seals and the adjacent

flat surfaces

18 and 41 of housing 12 and outer race 38 to extend along a plane which includes the rotational axis of rotor 29 and bisects the flat housing surfaces 18. One of a pair of bores 44 extends through housing 12 at each side of the sealing means 43. Thus, the race 38 may be shifted as described above and held at the selected position by forcing high pressure fluid into one of the bores 44 while venting the other bore 44.

Considering now how a pumping or motor action is achieved, the radially outermost end of each spoke 33 extends into a cylindrical skirt portion 46 of an associated separate one of a plurality of cylinders 47. The radially outermost end of each such cylinder 47 has a slipper pad flange 48 having an arcuate outer surface 49 for riding against the inner surface of inner race member 39 as the hub 29 revolves. To provide for a lubricating film of fluid between the slipper pads and race member 39, the outer surface of each slipper pad may have a shallow recess 51 communicated with the interior of the cylinder through an aperture 52.

With race 38 shifted to one end of the chamber 17 as previously described, the race is eccentric relative to the axis of rotation of rotor 29, and therefore, each cylinder 47 reciprocates relative to the associated rotor spoke 33 as the rotor revolves. To provide for the admission and release of fluid from the cylinders through the spokes, four

passages

53, 54, 56 and 57 extend within rotor support 21.

Passages

53 and 54 both communicate with a first port 58 at the exterior surface of rotor support 21 while

passages

56 and 57 both communicate with a second port 59 thereat, the two ports being connectable with an external source of fluid and a discharge for such fluid as will hereinafter be described in more detail. Within the region encircled by the hub 31 of rotor 29,

passages

53 and 54 terminate at

radial openings

61 and 62 respectively that are in communication with the internal passages 34 of the particular spokes which at any given time are in passage between opposite ends of housing chamber 17 at the side thereof at which the cylinders are being urged radially inwardly on the associated spokes 33. Similarly.

passages

56 and 57 terminate at radially directed

openings

63 and 64 respectively which communicate with the internal passages of the particular rotor spokes 33 that at any given time are moving between the ends of chamber 17 at the other side wherein the cylinders 47 are moving radially outward relative to the associated spokes 33.

1f the device 11 is to be operated as a motor, port 59 is connected to a source of pressurized fluid while port 58 is connected to a drain. High pressure fluid is thereby directed through

passages

56, 57, 63 and 64. Through rotor spoke passages 34, this pressure is transmitted to the cylinders 47 at one side of chamber 17 and the cylinders in turn react against inner race member 39 to create a torque force which causes the rotor 29 to revolve in a clockwise direction as viewed in FIG. 1. At the other side of chamber 17, where the cylinders 47 are being forced radially inward on the associated spokes, hydraulic fluid is released through

passages

61, 62, 53, 54 and port 58. As rotor 29 is rotationally linked to shaft 23 by spline coupling 32, the shaft 23 is forcibly turned and may be utilized to drive an external load.

To use the device 11 as a pump, shaft 23 is forcibly turned (e.g., clockwise) by an external motor. Port 59 may be connected to a source of fluid to be pumped while port 58 is communicated with the means which is to receive the discharge of the pump. The expanding volume within those of the cylinders 47 which are communicated with

passages

63 and 64 at any given time causes fluid to be drawn into port 59 by suction while the decreasing volume within those of the cylinders which are communicated with

openings

61 and 62 at any given time causes fluid to be forcibly discharged from port 58.

It should be noted that the direction of rotor rotation while functioning as a motor or the direction of flow between the two

ports

58 and 59 in the pumping mode can be controlled by shifting the race member 38 from one end of housing chamber 17 to the other in the manner previously described. The direction of the eccentricity of the path of cylinders 47 relative to the axis of rotation of hub 29 is thereby shifted in such a manner that the motor or pumping action reverses.

During operation as a motor, hydraulic fluid pressures within the cylinders 47 as well as centrifugal force tends to hold the cylinders 47 against the inner race member 39. During operation as a pump, centrifugal force again tends to hold the cylinders against the raceway, but hydraulic pressure is effective for this purpose for only a portion of the cylinders at any given time. Those of the cylinders 47 which are temporarily connected to the port which is functioning as the intake for the pump may be subjected to a negative pressure. Whether utilized as a motor or as a pump, these forces are not effective to hold the cylinders against the inner race 39 when the device is shut down and during a brief period at start up. Accordingly, supplementary means are needed to assure that the cylinders 47 are held at the inner race member 39 under all conditions.

For this purpose one of a pair of guide rings 66 is disposed at each side of cylinders 47 within the region encircled by inner race member 39 and in coaxial relationship therewith. An annular collar 67 encircles each cylinder 47 adjacent the slipper pad flange 48 of the cylinder and each such collar overlaps and rides against the guide rings 66, the guide rings and collars being proportioned to provide a clearance space 68 between the collars and flanges 48 to allow for thermal expansion without binding.

To maintain the cylinders 47 in contact with the inner race member 39, in the presence of clearance space 68, wells 69 are provided in each collar 67 and a coil spring 71 is received in each such well to exert a yieldable outwardly directed force against the flange 48 of the associated cylinder. Thus each cylinder is continuously urged towards the inner race 39 while enabling adjustment to thermal expansion effects.

Other means for exerting the resilient force between collars 67 and cylinder flanges 48 may readily be employed if desired. FIGS. 3 and 4 illustrate a modification of the invention wherein such means is a single annular wave washer 72 encircling cylinder 47' between collar 67' and slipper pad flange 48'. Such washers 72 are formed of resilient material and, as best seen in FIG. 4, have an undulated curvature whereby the washers may be compressed between collars 67 and flanges 48' to exert the desired outward force on the cylinders. FIG. 5 illustrates still another modification in which the resilient force exerting means is a Belleville spring 73 encircling cylinder 47" between collar 67" and slipper pad flange 48". Such springs 73 are also formed of resilient material and have a truncated conical configuration so that compression of the spring between the collar and flange causes a force to be exerted therebetween.

Thus many modifications are possible and it is not intended to limit the invention except as defined in the following claims.

What is claimed is:

1. In a fluid translating device, the combination comprising:

an annular race;

a rotor journaled for rotation within said race about an axis which is eccentric relative thereto, said rotor having hollow piston spokes extending radially towards the inner surface of said race and having means for admitting fluid to said spokes during a first portion of the angular movement thereof and for releasing fluid from said spokes during another portion of the angular movement thereof;

a plurality of cylinders each having an open inner end into which an associated one of said spokes is received and having an outer end which rides against said inner surface of said race as said rotor turns, said outer ends of said cylinders having flanges thereon.

a guide ring disposed coaxially within said race in radially spaced relationship therefrom, and

resilient means for urging each of said cylinders outwardly from the rotational axis of said rotor and towards said inner surface of said race, said resilient, means being disposed between said flanges and said guide ring to act against said flanges and to react against said guide ring.

2. The combination defined in claim 1 further comprising a plurality of annular collars each encircling a separate one of cylinders between said guide ring and said resilient means.

3. In a fluid translating device, the combination comprising an annular race.

a rotor journaled for rotation within said race about an axis which is eccentric relative thereto. said rotor having hollow spokes extending radially towards the inner surface of said race and having means for admitting fluid to said spokes during a first portion of the angular movement thereof and for releasing fluid from said spokes during another portion of the angular movement thereof,

a plurality of cylinders each having an open inner end into which an associated one of said spokes is received and having an outer end which rides against said inner surface of said race as said rotor turns, said outer ends of said cylinders having flanges thereon,

a guide ring disposed coaxially within said race in radially spaced relationship therefrom,

resilient means for urging each of said cylinders towards said inner surface of said race wherein said resilient means act against said flanges and reacts against said guide ring,

a plurality of annular collars each encircling a separate one of the cylinders between said guide ring and said resilient means,

wherein each of said collars has a plurality of wells therein opening at the surface of the collar which faces said flange of the associated one of said cylinders, and wherein said resilient means comprises a plurality of coil compression springs each being disposed in one of said wells of said collars and extending therefrom towards said flange of the associated one of said cylinders.

4. In a fluid translating device, the combination comprising an annular race,

a rotor journaled for rotation within said race about an axis which is eccentric relative thereto, said rotor having hollow spokes extending radially towards the inner surface of said race and having means for admitting fluid to said spokes during a first portion of the angular movement thereof and for releasing fluid from said spokes during another portion of the angular movement thereof,

resilient means for urging each of said cylinders towards said inner surface of said race wherein said resilient means act against said flanges and reacts against said guide ring, and

wherein said resilient means comprises a plurality of annular wave washers each encircling one of said cylinders between said flange thereof and said collar thereon, said washers being formed of resilient material and having an undulated configuration.

5. In a fluid translating device. the combination comprising an annular race.

resilient means for urging each of said cylinders towards said inner surface of said race wherein said figuration.

Claims

1. In a fluid translating device, the combination comprising: an annular race; a rotor journaled for rotation within said race about an axis which is eccentric relative thereto, said rotor having hollow piston spokes extending radially towards the inner surface of said race and having means for admitting fluid to said spokes during a first portion of the angular movement thereof and for releasing fluid from said spokes during another portion of the angular movement thereof; a plurality of cylinders each having an open inner end into which an associated one of said spokes is received and having an outer end which rides against said inner surface of said race as said rotor turns, said outer ends of said cylinders having flanges thereon, a guide ring disposed coaxially within said race in radially spaced relationship therefrom, and resilient means for urging each of said cylinders outwardly from the rotational axis of said rotor and towards said inner surface of said race, said resilient, means being disposed between said flanges and said guide ring to act against said flanges and to react against said guide ring.

3. In a fluid translating device, the combination comprising an annular race, a rotor journaled for rotation within said race about an axis which is eccentric relative thereto, said rotor having hollow spokes extending radially towards the inner surface of said race and having means for admitting fluid to said spokes during a first portion of the angular movement thereof and for releasing fluid from said spokes during another portion of the angular movement thereof, a plurality of cylinders each having an open inner end into which an associated one of said spokes is received and having an outer end which rides against said inner surface of said race as said rotor turns, said outer ends of said cylinders having flanges thereon, a guide ring disposed coaxially within said race in radially spaced relationship therefrom, resilient means for urging each of said cylinders towards said inner surface of said race wherein said resilient means act against said flanges and reacts against said guide ring, a plurality of annular collars each encircling a separate one of the cylinders between said guide ring and said resilient means, wherein each of said collars has a plurality of wells therein opening at the surface of the collar which faces said flange of the associated one of said cylinders, and wherein said resilient means comprises a plurality of coil compression springs each being disposed in one of said wells of said collars and extending therefrom towards said flange of the associated one of said cylinders.

4. In a fluid translating device, the combination comprising an annular race, a rotor journaled for rotation within said race about an axis which is eccentric relative thereto, said rotor having hollow spokes extending radially towards the inner surface of said race and having means for admitting fluid to said spokes during a first portion of the angular movement thereof and for releasing fluid from said spokes during another portion of the angular movement thereof, a plurality of cylinders each having an open inner end into which an associated one of said spokes is received and having an outer end which rides against said inner surface of said race as said rotor turns, said outer ends of said cylinders having flanges thereon, a guide ring disposed coaxially within said race in radiAlly spaced relationship therefrom, resilient means for urging each of said cylinders towards said inner surface of said race wherein said resilient means act against said flanges and reacts against said guide ring, and a plurality of annular collars each encircling a separate one of the cylinders between said guide ring and said resilient means, wherein said resilient means comprises a plurality of annular wave washers each encircling one of said cylinders between said flange thereof and said collar thereon, said washers being formed of resilient material and having an undulated configuration.

5. In a fluid translating device, the combination comprising an annular race, a rotor journaled for rotation within said race about an axis which is eccentric relative thereto, said rotor having hollow spokes extending radially towards the inner surface of said race and having means for admitting fluid to said spokes during a first portion of the angular movement thereof and for releasing fluid from said spokes during another portion of the angular movement thereof, a plurality of cylinders each having an open inner end into which an associated one of said spokes is received and having an outer end which rides against said inner surface of said race as said rotor turns, said outer ends of said cylinders having flanges thereon, a guide ring disposed coaxially within said race in radially spaced relationship therefrom, resilient means for urging each of said cylinders towards said inner surface of said race wherein said resilient means act against said flanges and reacts against said guide ring, a plurality of annular collars each encircling a separate one of the cylinders between said guide ring and said resilient means, wherein said resilient means comprises a plurality of annular Belleville springs each encircling one of said cylinders between said flange thereof and said collar thereon, said springs being formed of resilient material and having a truncated conical configuration.