US2953099A

US2953099A - Pump

Info

Publication number: US2953099A
Application number: US665387A
Authority: US
Inventors: Budzich Tadeusz
Original assignee: New York Air Brake LLC
Current assignee: New York Air Brake LLC
Priority date: 1957-06-13
Filing date: 1957-06-13
Publication date: 1960-09-20
Anticipated expiration: 1977-09-20

Description

T. BUDZICH PUMP Filed June is, 1957 2 Sheets-Sheet 1 INVENTOR Tadeus'z. Budzich BY MM 5 m X \H \Y H Q1 4 q Iv V //yv 0m m Tm @V x 5 \W Q Q 5 mm. mm! :11: I g wn W a. a a. 9 1 m mm Hm mm HN/ vN Nn AYW 3 N I? 1 ANIAM ATTORNEYS T. BUDZICH Sept. 20, 1960 PUMP 2 Sheets-Sheet 2 Filed June 13, 1957 Pie. '5

mvmon TadeuszBudzich ATTORNEYS nited States patent I PUMP Tadeusz Budzich, Watertown, N.Y., assignor to The New York Air Brake Company, a corporation of New Jersey Filed June 13, 1957, Ser. No. 665,387

4 Claims. (Cl. 103-162) This invention relates to fluid pressure pumps and more particularly to pumps of the type including a rotary cylinder barrel and a plurality of longitudinally reciprocating pistons.

In pumps of this type, the pistons are usually reciprocated by an inclined cam plate which moves them on their discharge strokes and a nutating plate which moves them on their suction strokes. The nutating plate is universally mounted on a support-ing collar which encircles the drive shaft and which is freely slidable in a longitudinal direction thereon. The pump also includes a biasing spring reacting between the cylinder barrel and the supporting collar for urging the pistons into operative engagement with the cam plate and for urging the cylinder barrel into contact with a ported valve plate located adjacent one of its end faces. It is thus seen that the spring serves two separate functions, viz: it prevents separation between the pistons and the cam plate and it provides a sealing force between the cylinder barrel and the valve plate during starting conditions.

Pumps of the type mentioned perform satisfactorily at low speeds but when the pump is operating at high speeds and the inertia loads transmitted to the nutating plate by the pistons are high, the biasing spring compresses and allows the pistons to leave the cam plate. The resultant hammering of the pistons on the cam plate causes serious maintenance problems and limits the usefulness of the pump. In order to minimize this effect, various methods of increasing the size of the biasing spring have been employed. This approach, however, is not rewarding because as the spring force is increased, so too is the sealing force between the cylinder barrel and the valve plate and consequently, the friction force acting between these members becomes very large. Most of these pumps are provided with a balancing film of oil between the cylinder barrel and the valve plate but since this film is effective only when the pump is operating, it can be seen that a large friction force would make it difficult to start the pump. Therefore, as a practical matter, the biasing spring must be designed to afford the best compromise between these two conflicting functions and accordingly, the operating speed of the pump will be limited.

The object of this invention is to provide a pump of the type mentioned in which the pistons are maintained in operative engagement with the cam plate regardless of operating speed, and in which the magnitude of the sealing force urging the cylinder barrel into contact with the valve plate can be selected to effect adequate sealing without causing undue friction. Briefly, the invention consists in constraining the nutating plate support against longitudinal movement relatively to the shaft and in providing a thrust bearing between the shaft and the housing for supplying the reactive force for the piston inertia loads transmitted to the shaft by the nutating plate and its supporting collar. Compared with the biasing spring, the housing affords a relatively unyielding reaction surface and therefore the difliculties stemming ice from the hammering effect, mentioned above, are avoided. Furthermore, since the biasing spring now performs only one function, it can be designed solely with respect to this function and optimum sealing can be realized.

In the preferred form of the invention, one portion of the thrust bearing is longitudinally adjustable so that after the pump is assembled, the shaft, supporting collar and nutating plate may be moved in a longitudinal direction to bring the pistons into operative engagement with the cam plate. In this way, manufacturing tolerances can be reduced and the adverse effects of their accumulation during assembly can be avoided.

Another feature of the invention relates to the provision of a universal support for that portion of the thrust bearing carried by the shaft so that the mating faces of the bearing members will remain in contact even though the shaft deflects during operation.

The invention will now be described in more detail with reference to the accompanying drawings, in which:

Fig. 1 is an axial section of a variable displacement pump employing a first embodiment of the invention.

Fig. 2 is an enlarged sectional view of the thrust bearing shown in Fig. 1.

Fig. 3 is a sectional view of a second form of thrust bearing suitable for use in the Fig. 1 embodiment.

Fig. 4 is a sectional view of a third embodiment of the invention.

Referring to Fig. l, the pump comprises a housing having two

separable sections

11 and 12 formed with mating flanges connected by bolts 13. The right end of the section 12 is bored to receive a conventional ported valve plate 14 which is constrained against rotation by pin 15. A two-part drive shaft, having

telescoping sections

16 and 17 connected by splines 20, extends through the housing and is journalled at its left end in the bearing 18 fitted in housing section 11. The right end of the shaft is splined to a collar 19 which is supported by bearing 21 mounted in valve plate 14.

A rotary cylinder barrel 22 is universally supported on the drive shaft by spherical enlargement 23 and is connected in driven relation with the shaft by torque tube 24 and splines 25 and 26. This method of supporting and driving the cylinder barrel is more fully described and claimed in applicants copend-ing application Serial No. 656,574, filed may 2, 1957. Surrounding the torque tube is a biasing spring 27 which reacts against adjustable seat 28 for urging the cylinder barrel into contact with valve plate 14. The opposite end of the spring is supported by shaft 17 via shoulder 29, washer 31, splines 25 and washer 32. The cylinder barrel contains a circumferential series of longitudinal cylinder bores 33 which extend through the barrel for receiving pistons 34. At its left end, each piston 34 is formed with a spherical head 35 for universally supporting a piston shoe 36. An adjustable cam plate 37 is supported in the housing section 12 by trunnion and yokes (not shown) for angular adjustment about an axis extending in a direction normal to the axis of the drive shaft and intersecting that axis at the point of intersection 38 of the plane of the centers of the spherical piston heads and the axis of the drive shaft. The lower end of the cam plate 37 is universally connected with spring plunger 39 and motor piston 41 which cooperate to vary its angular position about the above-mentioned axis.

A nutating plate 42, loosely connected with each the piston shoes 36, contains a central spherical recess 43 which cooperates with the outer surface 44 of the collar 45 to form a universal support for the nutating plate. The centers of the surfaces 43 and 44 are located at the point 38 mentioned above. The collar 45 abuts against annular shoulder 46 formed on the shaft. As will appear from the following description, the collar 45 functions as an integral part of the drive shaft 17 but, because of manufacturing considerations, it is made a separate part, as shown.

. Drive shaft section 17 contains an axial bore 47 havingathreade'd portion, as shown. A plug '48, having a plate engages loosely the surface of bore 47 V and is formed in the shape'of a sphere to permit relative rocka ing motion between this'member and the drive shaft.

After thepump has been assembled, a suitable tool wouldbeinsertedinto theleft end of bore 47 for turning the plug 48 and advancing it to'the right. This movement will bring surface52 in contact with bearing plate 53 and will bring. thelatter into contact with the end Wall of housing section 12. Further advancement of the plug 48'will move the shaft v17 to the left causing shoulder 46, acting through collar .45 and nutating plate 42, to bring piston shoes 36 into abutment with the surface of cam plate 37 When this adjustment is complete,the lock nut 51 would be 'screwedinto engagement with plug 48 and a sealing plug 56 would be threaded into the left end of V bore 47.

Duringoperation, rotation of cylinder barrel 22 will cause cam plate 37 to move the pistons 34 on their discharge strokes, and nutating plate 42, acting through the shoes 36, to move the pistons on their suction strokes.

The inertia of the pistons 34 will exert a force on the nutating plate 42 acting toward the right (as viewed in Fig. 1) and this force will be transmitted to the drive shaft by collar 45 and shoulder 46. The inertia forces will then travel through the support plug 48 and bearing plate 53 into the housing section 12. It is thus apparent .that no matter how large these inertia forces may be,

they'are resisted by the'housing 12 and consequently,the

shoes 36 will always remain in contact with the surface of cam plate 37.

It should be noted that biasing spring 27, acting through washer 32, splines 25, Washer 31, shoulders 29 and 46, collar and nuta ting plate 42, also transmits a force to shoes.36 urging them into contact with camplate 37. 7

However, this force is not large enough to maintain contactbetween the shoes and the cam plate and acts on the shoes merely as an incidentof providing a reaction seat for spring 27. In other words, in order for spring 27 to urge cylinder barrel 22 into abutment with valve plate 14, it is necessary to provide a reaction surface for the spring, and since the path just described aifords the a most convenient reaction surface, it is used.

Fig. 3 illustrates a second form of thrust hearing which the bearing plate 57 contains a central threaded bore for receiving an adjustable plug 58. The end face of the plug contacts a ball 59 which is seated ina conical bore 61 formed in the right end of shaft 17. A stationary 7 could be used in the pump of Fig. 1. In this embodiment,

hearing 62, located in alignment with plate57, is pressed into a bore in the end wall of housing section 12. The

' hea ing plate 57 is connected in drivenarelation with shaft 17 by splines 63 and collar 19.

bearing Plate 5 7 "will be forced to the right iritoabutment with stationary bearing 62, and the shaft will be moved to the left to place the shoes 36 in contact with cam plate '37 as previously described. 'The adjusted position of plug 58 is maintained by a conventional nylon lock and the bore 64 is sealedby an O-ring andplug as shown.

'Tfheinertia loads transmitted to-the shaft by the nutating plate. are delivered to the housing by ball 59, plug 58, hearing plate 57 and stationary bearing 62.

Fig. 4 illustrates a third embodiment of the invention. In this case, the thrust bearing is located at the left end of the drive shaft and comprises an annular bearing plate 66 encircling the shaft section 16 and connected to this section by key 67. Since deflect-ions of shaft section 17 Will not be transmitted to section :16, because of the inherent looseness in splines 20, it is not necessary to provide a uuiversal'supportforthe bearing plate 66.. A nut 63 is threaded on the outer :peripheral surface of shaft section 16 and abuts against an annular land 69 formed on the plate 66 The nut contains a circumferential groove 71 and a plurality oflocking screws 72 which, when tightened, cause the nut to distort and the threads to bind, thereby locking the nut. The stationary bearing 73 of the thrust bearing is carried by an intermediate wall 74 which is securely clamped between the

housing sections

11 and 12 when they are'ass embled.

When the nut 68 is turned so that it advances to the right, the bearing

members

66 and 73 are forced into contact. Further advancement of the nut moves the shaft section 16 to the left, the key 67 sliding in the longitudinal groove provided in bearing member 66. Since the flange75 ofthe shaft section 16 is clamped between the plug 56 and the end of the shaft section 17, the shaft section 17 will follow'the movements of section'16; When the parts are in proper position, the screws 72 would be tightened to lock'the'nut 68 in place. 'The 7 piston loads transmitted tothe-shaft by the nutatingplate 42'and collar 45 are delivered to the housing 12via plug 56, flange 75, nut 68, hearing

members

66 and 73, and intermediate wall 74.

It can now be seen that in each of the three embodiments' of the invention, the thrust bearing, shaft and nutating plate supporting collar provide a rigid, unyielding force transmitting link for conveying the piston inertia loads to the pump housing. ;Thus, the pistons in each embodiment will always be maintained in contact with the cam plate. Furthermore, the provision of this force path eliminates one of the heretofore essential functions of biasing spring 27, and therefore this spring can now be designed solely with regard to the sealing requirements between the cylinder barrel and valve plate.

'It can also be seen that the above-mentioned rigid force transmitting link carries only. the inertia forces of the pistons. The thrust or hydraulic loads (which for each piston equals the pressure in cylinder bore 33 multiplied by the cross-sectional area of the piston) are transmitted to the housing through the cam plate 37 and its yokes and trunnions (not show).

Since the drawings and description relate only to three of many possible embodiments of this invention, and since many changesin the structure of these embodiments can be made without departing from the inventive idea, the following claims should provide the sole meansure of the scope of the invention.

What is claimed is:

' 1. In a pump of the typeincluding a housing, a drive shaft journalled in the housing, a rotary cylinder barrel connected in driven relation with but being free to move longitudinally of the drive shaft, a plurality of reciprocable pistons mounted in longitudinal cylinder bores formed in the cylinder barrel, a stationary valve face located in a plane extending in a direction normal to the axis of rotation and containing inlet and outlet ports which com their suction strokesandin whichthe hydraulic loads of the pistons are transmitted to the housing through the cam plate and the inertia loads" of the pistons tend to move; the nutating' plate in a longitudinal direction, the im-- provement which comprises means forming a'rigid forcetransmitting link between the nutating plate and the shaft; and means forming a rigid force-transmitting link between the shaft and the housing, whereby the inertia loads of the pistons are transmitted to the housing through the nutating plate and the shaft without producing relative longitudinal movement between the nutating plate and the housing.

2. The improvement defined in claim 1 in which the inner end of the drive shaft is spaced from a wall of the housing and the shaft is formed with an axial bore having a threaded portion adjacent the inner end of the shaft, and in which the means forming a rigid force transmitting link between the shaft and the housing comprises a hearing support threaded in the bore; a thrust bearing mounted for universal movement on the support; means connecting the bearing in driven relation with the shaft but permitting free longitudinal movement of it relatively to the shaft; and a bearing surface in alignment with the thrust bearing and supported by the said wall of the housing.

3. The improvement defined in claim 1 in which the means forming a rigid force transmitting link between the shaft and the housing comprises a spherical member carried by the inner end of the shaft and centered on the shaft axis; a thrust bearing mounted for universal movement on the spherical member; means connecting the hearing in driven relation with the shaft but permitting free longitudinal movement of it relatively to the shaft; a bearing surface in alignment with the thrust bearing and supported by the housing; and an adjustable threaded member coaxial with the shaft and reacting between the shaft and the thrust bearing through the spherical member for moving the thrust bearing into contact with the bearing surface and for causing the shaft and nutating plate to move the pistons into operative engagement with the cam plate.

4. The improvement defined in claim 1 in which the means forming a rigid force transmitting link between the shaft and the housing comprises a thrust bearing; means connecting the bearing in driven relation with the shaft but permitting free longitudinal movement of it relatively to the shaft; a bearing surface in alignment with the thrust bearing and supported by the housing; means adjustable in the longitudinal direction and reacting between the thrust bearing and the shaft for moving the thrust bearing into contact with the bearing surface and for causing the shaft and nutating plate to move the pistons into operative engagement with the cam plate; and locking means for maintaining the adjustable means in its adjusted position.

References Cited in the file of this patent UNITED STATES PATENTS 895,961 Case Aug. 11, 1908 941,834 Wing Nov. 30, 1909 1,239,057 Sparks Sept. 4, 1917 1,242,744 Trautman Oct. 9, 1917 1,362,040 Pratt Dec. 14, 1920 1,688,825 Mills Oct. 23, 1928 1,839,497 Petuson Jan. 5, 1932 2,776,628 Keel Ian. 8, 1957 FOREIGN PATENTS 267,265 Great Britain Mar. 17, 1927 534,773 France Jan. 12, 1922 539,939 Germany Nov. 26, 1931 574,612 Germany Mar. 23, 1933 OTHER REFERENCES MacDufi: abstract of application Serial No. 717,764,

published October 31, 1950, 639 0.6, 1661.