US 2940323 A
Description (OCR text may contain errors)
2 Sheets-Sheet l F. M- COUSlNS EVAL June 14, 1960 Filed Aug. 24, 1956 June 14, 1960 F. M. couslNs EVAL 2,940,323
Filed Aug. 24, 1956 2 Sheets-Sheet 2 FM. COUJ//VJ it E P- F- f//LDER PUB/[P li'rerl M. Cousins, Grosse Pointe Woods, and Harold L.
Brock, Detroit, Mich., assignors to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Filed Aug. 24, 1956, Ser. No. 606,118
3 Claims. (Cl. 74-60) This invention relates to pumps, and more specilically to a hydraulic pump in which one or more individual pistons are driven by a so-ca'lled swash plate.
The pump of the present invention, which is particularly useful in the pumping of hydraulic uids, consists of a pump body having `one or more planetarily arranged, nonrotating cylinders each of which are provided with an inlet and outlet port and a piston which is spring-pressed in its return stroke. 'I'he pistons are successively driven in their pumping strokes by a swash or wobble plate whose surface extends in a plane nonradially of the drive shaft of the pump. Among the characteristics of this pump are economy of manufacture and extreme durability and long-life, even when pumping hydraulic uids containing a relatively large amount of abrasive dirt and dust particles.
Among the objects of the present invention are to provide a pump for hydraulic iluids Which is economical to manufacture, is durable and long-lived, and which will pump uids containing va relatively large amount of abrasive dirt and dust particles without causing undue wear of the pump or otherwise affecting its operation.
Other objects and the nature and scope of the invention will become more `apparent from a consideration of the detailed description to follow, taken in conjunction with the drawings.
Our invention is clearly defined in the appended claims. In the claims, as well as in the description, parts may at times be identilied by specific names for clarity and convenience, but such nomenclature is to be understood as having the broadest meaning consistent with the context `and with the concept of our invention as distinguished from the pertinent prior The best form in which we have contemplated applying our invention is illustrated in the accompanying drawings forming part of this specification in which:
Figure 1 is `an axial section of the pump, certain of the parts of the pump being shown in side elevation.
Figure 2 is an enlarged fragmentary section of the pump, showing a portion of one of the cylinders, together with its intake and outlet valve and a portion of its piston.
Figure 3 is a somewhat diagrammatic enlarged fragmentary section showing .the contact between the end of one of the pistons and the swash plate.
Referring now to Figure l, the pump of the present invention comprises a pump body which may consist of a two-part casting, one part 11 of the body having one or more planetarily arranged cylinders extending parallel to a central axis and preferably also including an inlet manifold 12 communicating with each of the cylinders. The second part 14 of the pump body rotatably mounts Ka drive shaft 15, which will be described hereinafter. An outlet manifold 16 may be secured to an end of the pump body part 11 to close the ends of the cylinders and to mount the outlet valve for each cylinder, as will be described.
Referring now more specically to the pump body part 1l, this part has one or more cylinders 19 formed therein hired States Patent G which are parallel to and equally spaced from a central axis 20 of the pump body 10. Each cylinder 19 has a bore 21 extending from an enlarged, axially centered chamber 22 communicating with all of the cylinders 19 and receiving the end of the drive shaft 15. The end 24 `of each cylinder 19 adjacent the outlet manifold 16 is of slightly larger diameter (preferably about fifteen thousandths of an inch larger) and is on a common axis with the bore 21 to provide a step or ledge 25 for wiping and `accumulating abrasive particles from the side bearing surface of a piston 26 positioned within the cylinder.
rI'he inlet manifold 12 is preferably cast integrally with fthe pump body part 10 and completely surrounds the cylinders 19. The inlet manifold 12 may be provided with a ilange 29 surrounding the entrance to the manifold, the flange 29 being provided with -a groove 30 to retain an O ring (not shown). Preferably the manifold 12 is cast with a hole 180 from the liange 29 to aid in removing the core sand, the hole subsequently being closed with a plug 27.
A series of inlet ports 31 are provided, one for each cylinder, connecting the manifold 12 with the cylinders 19. Each inlet pont 31 is provided with an inlet valve which is preferably of the check-valve type consisting of a steel sphere or ball 34 spring-pressed by a spring 35 into sealing engagement with a ring-shaped valve seat 36. Preferably, the inlet valves are received within a space disposed radially outwardly of the cylinders 19 and communicating therewith, as indicated in the drawings.
The outlet manifold 16 preferably comprises an end casting bolted to the end of the pump body part `11 and having `an annular passage 37 extending opposite the ends of the cylinders 19. A ange 39 surrounding the outlet passage 37 and preferably coplanar with the inlet flange 29 and provided .with a gasket groove 40 provides a leak-tight connection for the outlet passage. Studs 4l may be provided for holding the flanges 29 and 39 in sealing relation to hydraulic conduits (not shown) leading to and from the pump body 10.
An outlet port 42 connects each cylinder 19 with the outlet manifold passage 37. Preferably, each outlet port 42 extends axially from the end of a cylinder 19. Each port 42 is provided with an outlet valve ofthe checkvalve type, consisting of a steel ball 45 which is biased into seating engagement by a spring 46. Preferably, the springs 46 are supported against displacement by pilot pins 47.
For convenience of manufacture, and for easy replacement of rthe valve seats of the outlet valves 44, the valve seats and outlet ports 42 are formed within la iiat plate 49 which may be secured to the outlet manifold 16 by a screw 50 located axially of the pump. The plate 49 seals the ends of the cylinders 19, gaskets being interposed between -the plate, the pump body part 11 and the manifold casting `i6. The plate 49 also has pins 48 mounted therein for supporting the inlet springs 35 against displacement.
Each piston 26, yadjacent the enlarged, pumping end 24 of the cylinder, has an end portion 51 of reduced diameter to provide clearance for a helical piston spring 52 extending between the plate 49 surrounding the outlet port 42 and the portion of the piston fitting within the bore 21 of each cylinder. The springs 52 serve to return the pistons in their suction stroke, at which time the outlet valve 44 is closed and fluid is drawn in through the inlet valve 32, displacing the ball 34 from its seat. Preferably, each piston spring 52 is maintained axially centered within the the enlarged end 24 of the cylinder and out of contact with the end portion 51 of the piston by a concentric stepped portion 54 of the piston of diameter Patented June 14, 1960l intermediate between that of the end portion and the maximum diameter ofthe piston. Y
The pistons 26 are operated by Vrotation of the drive l loads and a needle'bearing 5S'. The end -of the drive shaft 15"towards the pistons 26 is formedfto provide a Hat circular plate or surface 56 extending nonradially thereof andreceived within the chamber 22. The surface 56 of the shaft is provided with a cylindrical central portion v57 projecting perpendicularly to the surface 56 and retaining a'circular Vs'wash plate 59 separated from the-surface 56 of the shaft Vlby a thrust bearing 60 of the roller type. The construction Yis such that the nplate 59 is free to turn on the surface 56 of the shaft 15 Vand Yis maintained centeredlon such surface bythe projecting portion -57 lof the shaft. The surface 61 kof the plate59 is concentric with, the axis of the drive shaft 15 but extends nonradially thereof, the assembly of drive shaft Y and plate forming `a swash plate drive -for operating the pistons .26. Y l
The amount which -eaoh piston is reciprocated by the plate 59 depends 'upon the degree of angularityriof the plane of the plate 59 to the axis of the driveshaft 15, and also upon the distance from the axis of the drive shaft to the point of contact between the plate and piston. Thegpump shown herein is of the fixed displacement-type, theangularity ofthe plate 59 being xed and the point of contact between the plate' and the pistons being a fixed distance `from the axis of shaft 15.
"Ilhe piston springs 52 bias the pistons towards the surface 61 of the plate 59Y so that the pistons tend to follow the plate during the suction stroke of each piston and are `driven by the plate during then-pumping stroke. Although the drive Yshaft is rotated ata lrelatively iii-gh speed, eg., up to 2000 rpm. or greater, there is essenface `of the plate. Y Y Y Y Y Y.
In order to assure long pump life, even when pumpl ing hydraulic Yfluids containing substantialA amounts ofV abrasive. particles .and operating at pressures of 2000 p.s.`i. Vonmore, the `ends of Ythe pistons are given a specific contour which is shown in more detail in Figure 3. The end of each piston 26 lhas a convexly arched surface of `rotation 62, the amount of arch or crown of the surface being about .O02 of an inch. The surface of rotation 62 closelyrapproximates a truncated cone, thefelements of which make an angle with the axis of the piston equal .to the angle betweenthe surface 61 of the plate 59 and the -axis ,of Vthe drive shaft 15 in the present pump); Y
Preferably, each Vpiston 26 is provided with a marginal Y surface 62 and preferably alittle closer to the outer diameter of such surface. Il`he'above-described contour of .the endsof pistons 26 prevents contact over a small area adjacent either the center or the periphery ofV the I. pistons, even despite'minor misalignmentfof portions ofA the pump dueto normal manufacturing tolerances andY Y construction of the pump body in twowpieces, and thus contributes' to 4long life of the pump.'` f
" 'libe-drive shaft 15 is providedv with asmooth, cylindri- (about 111/2 degreesV cal surface 66 for receiving a shaft seal 67 to prevent passage of hydraulic iiuid along the shaft.' However, the .circular chamber 272 which contains the plate 59 is vented to the inlet manifold 27 by one or more holes 69 so that any leakage that may occur past the pistons 26 will feed back into the inlet manifold rather than force its way past the shaft seal, ,and the maximum hydraulic pressure on the shaft seal will he the pressure in the inlet manifold. The needle bearing 58 also engages the surfacet.` i'
. The end 76 ofthe drive shaft 15 may befsplined or keyed if desired `toreceive a drive lgear '.71 which' may Y project through an opening 72 in the vside of the pump valve springs A46,a;re made heavier to assure prompt closing-ofthe valves after pumping strokes of the pistons are complete. The piston springs 52 normally are made sufcientlylstrong to maintain the ends of the pistons against theswash plate 59 at all times.
For some purposes, e.g., ypower lsteering of vehicles, it is desirable to haveV a pump lthat will provide a more or -less uniform volume of output over a substantial speed range.v The pump of the present invention is particularly adaptable for such-a purpose by placing a restricted orifice or choke 77 in the inlet manifold 12V to resistrict the flow of iluid Vto the' pump. 'Ilhe piston springs 52 may be lchosen Vof-such strength that, at lower rotative speeds .tof .the pump, `the ends of the pistons will follow the swash Aplate 59 during its entire cycle of rotation. However, at higher speeds the choke 77 will starve-the .cylinders 19, .the pistons following the swash plate 59for only a portion of its cycle and thus pumping less than their fnll'volume. The nutative movement of the Vplate 59 will permit it to reengage the ends of the pistons 26 without undue shock and vibration.
The above-described pump is simple and economical 1 tomanufacture and -at the Sametime is efficient and dependable in operation. The unswept volume of each cylinder -is slight, making Vthe pump self-priming under mostycircumstances. g The pump body 10 is formed of two pieces for ease and economy of manufacture, and
minor-inaccuraciesV of alignment :resolving Vfrom normalV tolerances andthe two pieceV body are compensated for by the specific contour of the piston ends, thus providing apump in which wear isV reduced to theminimum, thus assurin'gllong life and dependable operation.
We claim; Y
Vl. In a-,purnpjfor'hydraulic fluids-of the type iu'which pistons `operating in parallel cylinders within a'firstrpump boFlYPQl'on are yoperated in their pumping` stroke by a drive shaft journalled in a second pump body ,portion and carrying a nonradially extendinglatplateportion positioned opposite the ,ends ofthe Ycylinders,'the pump body portions being united, the improvement whichcomprises: the kplate-p ortion-contacting.end Yof each piston being. shaped to provide Va convexly arched surface of rotation closely approximating the surface of Va truncated cone, the elements of which-make an angle with ythe axis of the piston ,corresponding to Ithe angle betweenzthe plane of the-plate portion offthe driveshaft `and its axis, the arch of said surface of Yrotation being crowned 'onY the order'ofa few thousandths-of an inch Wherebythe zione of contactbetween the plate portion andthe endsvof the pistons will Vfall within the boundaries-of vthe surface of rotation despite minor misalignment between the rst and the second pump body portions.
2. In a pump for hydraulic iiuids of the type in which pistons operating in parallel cylinders within a irst pump -body portion are operated in their pumping stroke by a drive shaft journalled in a second pump body portion and carrying a nonradially extending at plate portion positioned opposite the ends of the cylinders, the pump body portions being united, the improvement which comprises: the plate-portion-contacting end of each piston having the same diameter as the portion of the piston within the cylinder, having a peripheral chamfer and being shaped to provide a convexly arched surface of rotation closely approximating the surface of a truncated cone, the elements of which make an angle with the axis of the piston corresponding to the angle rbetween the plane of the plate portion of the drive shaft .and its axis, the arch of said surface of rotation being crowned on the order of a few thousandths of an inch whereby the zone of contact between the plate portion and the ends of the pistons will fall within the boundaries of the surface of rotation despite minor misalignment between the rst and the second pump body portions.
3. In a pump for hydraulic uids of the type in which pistons operating in parallel cylinders within a rst pump body portion are operated in their pumping stroke by a drive shaft extending -axially of a second pump body portion and carrying -a nonradially extending at platen portion positioned approximate the ends of the cylinders, the pump body portions being united, the improvement which comprises: the plate-portion-contacting end of each piston being shaped to provide a convexly arched surface of rotation closely approximating the surface of a truncated cone, the elements of which make an angle with the -axis of the piston corresponding to the angle -between the plane of the plate portion of the drive shaft and its axis, the arch of said surface of rotation being crowned on the order of two thousandths of an inch whereby the zone of contact between the plate portion and the ends of the pistons will @all within the boundaries of the surface of rotation despite minor misalignment between the iirst and the second pump body portions.
References Cited in the le of this patent UNITED STATES PATENTS 2,785,639 Huber Mar. 19, 1957 FOREIGN PATENTS 484,257 Great Britain May 3, 1938