US3761202A

US3761202A - Compressor with cross axis

Info

Publication number: US3761202A
Application number: US00218807A
Authority: US
Inventors: O Mitchell
Original assignee: John E Mitchell Co
Current assignee: John E Mitchell Co
Priority date: 1972-01-18
Filing date: 1972-01-18
Publication date: 1973-09-25
Anticipated expiration: 1990-09-25

Abstract

A multi-cylinder compressor of the nutating, or cam and wobble plate type, wherein the wobble plate is held against the cam rotor by a cross-axis mechanism that prevents rotation of the wobble plate while permitting its wobble, wherein all axial lost motion between the wobble plate and the cam is taken out by a continuous adjustable force transmitted through the cross-axis mechanism, preferably spring-maintained but capable of being positively and adjustably loaded, and wherein radial lost motion is prevented by design of the cross-axis mechanism.

Description

United States Patent 1191 Mitchell 1451 Sept. 25, 1973 COMPRESSOR WITH CROSS AXIS [75] Inventor: Orville Mitchell, Star Harbor,

Tex.

[73] -Assignee: John E. Mitchell Company,

Dallas. Tex. [22] Filed: Jan. 18, 1972 [21] Appl. No.: 218,807

[52] U.S. Cl. 417/269 [51] 1m.c1 F04b 1/12 [58] Field of Search 417/269, 270, 271;

[56] References Cited UNITEDSTATES PATENTS 3,552,886 1/1971 o1s'on....;...i 417/269 3,018,737 l/l962 Cook et al.... 417/269 3,455,585 7/l969 Raymond..... 417/269 3,257,960 6/1966 Keel 417/269 3,082,693 3/l963 Budzich 417/270 3,663,122 7/1972 Kitchen 417/269 Primary ExaminerWilliam L. Freeh Assistant ExaminerGregory LaPointe Attorney-Edmund C. Rogers [5 7] ABSTRACT A multi-cylinder compressor of the nutating, or cam and wobble plate type, wherein the wobble plate is held against the cam rotor by a cross-axis mechanism that prevents rotation of the wobble plate while permitting its wobble, wherein all axial lost motion between the wobble plate and the cam is taken out by a continuous adjustable force transmitted through the cross-axis mechanism, preferably spring-maintained but capable of being positively and adjustably loaded, and wherein radial lost motion is prevented by design of the crossaxis mechanism.

15 Claims, 11 Drawing Figures PAIENIEDsEPzswn Y SHEET 1 [IF 2 1 COMPRESSOR WITH CROSS AXIS BACKGROUND AND OBJECTS OF THE INVENTION Heretofore as, for example, in Olson U.S. Pat. No. 3,552,886, the wobble or follower plate has been maintained against rotation in the housing either by a pin and slot connection between the follower plate and the wall of the housing, or by a pair of intermeshing gearlike elements, one fixed to the housing and the other to the plate. Adjustments of the force holding the parts together, to minimizelost motion and noise, involved screw means acting axially from the housing to the plate. Severe problems arose with such constructions, particularly because of vibration and noise during operation of the compressor. It was found to be extremely difficult to adjust and control the amount of lost motion and to provide a precisely smooth operation both with respect to rotarymovements and rocking movements.

With the present invention, lost motion can be elimi nated by use of continuously acting axially adjustable pressure-applying means, acting through a two-axis connection'between the housing and the follower plate.

Furthermore, the lostmotion adjustment in the geartype connector of the kind illustrated in the Olson patent could directly affect only the force exerted by the wobble follower plate against the cam rotor, without adjusting the anti-rotation parts. In the applicant'sv device, the force controlling lost motion is transmitted throughout the cross-axis mechanism to the follower so that the working parts of the compressor are stabilized by the single continuous axial thrust.

Since'the presentarrangement involves a type of cross-axis connection permitting the wobble plate to rock in any direction, the same mechanism can be made to centralize the wobble follower on the cam rotor, prevent rotation of the follower, and by an adjustably applied force, prevent lost motion. The mechanism can be formed of parts that can be accurately machined to small tolerances at considerably less expense which is a further advantage over the Olson construction.

The foregoing has been accomplished with the further advantages that the piston rods move in radial planes only without significant peripheral movement of the outer ends thereof. A contributing factor to this is the more favorable lever arm length in the present construction, coupled with the lost motion take-up, as will be explained. This makes it possible to have the most accurate positioning of each of the pistons at the end of its compression stroke, thereby achieving the desired compression ratio with minimum tolerances. This is enhanced by the fact that the cross-axis connection permits the rocking movement to occur with a minimum of peripheral oscillation of the cam follower plate. The arrangement also permits the compressor to be made with the cylinders out of parallelism with the compressor' axis. g

The construction also makes possible the disposition of additional sets of cylinders radially outwardly from those illustrated and which would have different strokes, an arrangement that is particularly applicable to multi-stage compressors.

Another feature of the present arrangement is that it is unnecessary to have-a type of bearing at the center of the wobble plate such as is illustrated in the Olson patent to prevent lateral movement of the wobble plate. This advantage is obtained by the use of the cross-axis construction illustrated wherein the parts are so formed as to maintain the plate centered on the machine axis and to prevent such lateral movement. There are sufficiently close fits between the wobble plate and the cross-axis portion that, while rocking movement can occur, lateral displacement is prohibited.

Other advantages will appear from the description to follow.

IN THE DRAWINGS FIG. 1 is a view of the power input end of the compressor;

FIG. 2 is an opposite end view of the cylinder head of the compressor;

FIG. 3 is an enlarged diametrical section taken on the line 3-3 of FIG. 1;

FIG. 4 is a transverse section on the line 4-4 of FIG.

FIG. 5 is an elevation of the cross-axis connections and wobble plate, taken from the spring cavity;

FIG. 6 is a sectional view of the universal movement mechanism and wobble plate taken on the line 6-6 of FIG. 5;

FIG. 7, is a reduced view of the wobble plate;

FIG. 8 is a sectional view through the wobble plate taken on the line 8--8 of FIG. 7;

FIG. 9 is a diametrical section through' the wobble plate taken on the line 99 of FIG. 7 and enlarged;

FIG. 10 is an elevational view of the cross head; and

FIG. 11 is an edge view thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The compressor housing generally indicated at has a medial cylindrical portion 21, with a power input end cover 22 at oneend secured to it as by screws. A cylinder head 23 at the opposite end is likewise held on to the cylindrical portion 21 by screws, and clamps a valve plate 24 between itself and the housing.

The input head 22' supports an input shaft 25 that is adapted to be connected to a prime mover to be rotated thereby. An appropriate bearing and seal arrangement 26 provides for frictionless rotation of the shaft 25 within the housing 20. The shaft 25 supports a cam rotor 28. This rotor has its back face (the left side in FIG. 3). perpendicular to the axis of the shaft 25 and its forward surface at an angle thereto. Roller thrust bearings 30 between the back surface of the rotor and the inner surface of the head 22 take up thrust load on the rotor 28 as will appear.

The main housing portion 21 has a solid portion 32 at its right end as appears in FIGS. 3 and 4, which has a plurality of cylinders 33 cut therethrough. Centrally of this solid portion 32 of the housing 21 there is a cylindrical bore 35 that receives the cylindrical shaft end 36 of a joint holder or support member 37. The bifurcated head 38 of this member 37 has a medial recess 39, and, as will appear more fully, is drilled across to receive the ends of a rocking shaft.

' A cross head 41 has a first cross shaft or control shaft 42 that is snugly fitted into place in the cross head and held by a set screw 43. The shaft is rockably received in sleeve bearings 44 that are fixed in the holes drilled across the bifurcated head 38 of the joint holder member 37. The cross head 41 has shoulders or the like means 45 that fit closely between and bear against the two bifurcations of the member 38 or the two sleeve bearings 44 to reduce friction and yet to give a smooth operation with minimal end play or lost motion.

The cross head 41 also has, at ninety degrees to the shaft 42, projecting cylindrical oscillating shaft arms 48 having shoulders 49 adjacent the body of the cross head. The two rocker arms 48 are received for rocking movement in complementary semi-cylindrical grooves 50 mounted in a wobble type follower plate 51. This plate has roller thrust bearings 52 to permit the cam roller to roll freely against the non-rotatable follower plate 51 and rock it. The follower plate 51 has a rectangular recess 53 against the sides of which the shoulders 49 engage with a tolerance that permits free oscillation of the wobble plate but prevents radial movement of the follower plate.

The shaft 36 of the bifurcated support 37 is nonrotatably held in the cylindrical opening 35 by a key 54 anchored in the housing 21 that fits in a keyway 55 in the shaft portion 36. This key keeps the bifurcated member 38, the cross head member 41, and the follower 51 from rotating, while permitting axial movement of the support 37.

The shaft portion 36 of the support 37 is bored out at 56 to receive a compression spring 57. An adjusting screw 58 is threaded into the end of this bore and preferably bears against the end of the spring 57 whereby to apply a predetermined adjustable resilient force maintaining the member 38, the cross head 41, and the follower 51 and the rotor 28 in a close interengagement. Lost motion at this point should be minimized.

While the spring 57 is preferably relied upon to maintain this force, in some cases a fixed-force may be applied by tightening the screw 58 against the end of the support 37, usually without the spring 57, to take up lost motion between the cross-axis connections, the wobble plate, and the cam and housing.

The follower 51 has a plurality of hemispherical sockets 60 illustrated in FIG. 9. These receive the ball ends 62 of piston rods 63. The outer rims of the socket 60 are swaged over the spherical ends 62 to prevent withdrawal of the balls 62 from the sockets.

In similar fashion, the other end of each piston rod 63 has a ball portion 65 fitted into a spherical socket of a piston 66. The walls of the sockets are bent over to prevent withdrawal of the balls once the parts are assembled. However, the ball and socket joints, when properly lubricated, are realtively friction-free.

There are a number of pistons 66 corresponding to the number of cylinders 33, five being here illustrated, with their axes parallel to the axis of the machine, this being the preferred arrangement.- These pistons move from positions illustrated in FIG. 3, where their compression surfaces are coplanar with the ends of the cylinder housing 21 to an opposite extreme. As is known in the art, and as illustrated in Olson U.S. Pat. No. 3,552,886, the cylinder head comprises the valve plate 24 together with the head 23. The cylinder head has a fluid inlet 70 that opens into the inlet manifold 71, and through the valve plate 24 into each cylinder. A reed valve 72 regulating the inlet passage is closed in FIG. 3, and fluid previously drawn into the cylinder has been expelled through an outlet passage 76 past a reed valve 77 which now is open. The compressed fluid is forced out through an outlet manifold 78, that receives compressed fluid from all of the cylinders and the fluid is finally discharged through a discharge passage 79. The other cylinders operate in like fashion.

ASSEMBLY AND OPERATION In assembling this compressor, it will be assumed that the input head 22 is off. Before the pistons are installed, the shaft 36 of the bifurcated support 37 is inserted with the spring 57 in place, and the cross-axis mechanism attached to the support. As illustrated, the shoulders 45 hold the cross-head member with minimum tolerance between the arms of the bifurcated support 37 but in a manner to permit free rocking movement of the cross head about the axis of the cross shaft 42, here called the control axis. The other cylindrical arms 48 of the cross head 41 project at to the shaft 42.

After the foregoing, the pistons 66, attached to the follower plate 51, are all inserted in place with the proper rings or other compression-retaining means. The follower is moved into position so that its opposite grooves 50 receive the projecting rocker arms 48, in a manner to permit rocking movement of the wobble plate 51 about the axis of these arms 48, which axis is called the oscillating axis. Thereafter, the sub-assembly of the input head 22, drive shaft 25, and associated parts, with the cam rotor 28, secured to the shaft 25 to rotate therewith, are installed.

When this is completed, the adjusting screw 58 is turned until the proper force is applied to eliminate lost motion in the rocker assembly. Thereupon the valve plate and head 23 are installed with their appropriate gaskets and sealing means and subassemblied so that the compressor is ready to operate.

There is no circumferential lost motion, such as is inevitable in a gear or like arrangement, nor is there any problem of interengagement of teeth, since all of the connections remain permanently made throughout the drive train.

As the cam rotor 28 is rotated by the shaft 25, its high portion nutates the wobble plate 51, causing the pistons to be successively forced'in and out, as known in the art. The reed valves also operate in the known manner, the total result being compressed fluid delivered successively from the five cylinders out the outlet 79.

In the foregoing action, the spring 57 adjusted by the screw 58 applies force against the support 37, urging it leftward in FIG. 3. The head 38 of the support transmits this force to the pin 42 on the cross head 41, and by that member via the pins 48 to the plate 51; and any displacement of the cam 28 and input or drive shaft 25 is also taken up by forcing of the cam against the thrust bearing 30. Thus the single axially located mechanism regulates the pressure between all of the axially movable parts, centralizes and prevents rotation of the plate. Also there is little lost radial motion through the mechanism, and the plate 51 is held in position on the axis of the machine, and cannot slip radially, but has freedom to rock and operate the pistons.

As previously noted, lost motion, that can show itself in movement of the ends of the piston rods, and consequent variation in the compression ratio of the compressor, is reduced by this cross-axis construction, owing to the favorable leverage of the cross axis arrangement and the lost motion take-up. In former constructions, the lost motion take-up is applied very near to or at the axis of the wobble plate as by a ball-andsocket connection between a thrust member and the wobble plate, and the lost motion at that point of takeup is multiplied out at the ends of the piston rods.

The cross-axis mechanism hereof provides at least twice as much lever arm length as the prior art, since the lost motion take-up by the spring 57 or the shaft 36 is applied through the bifurcated arms of the head 38 and the

shafts

42 and 48, quite some distance from the axis. Also very close tolerances can be maintained in the shaft bearings, which can be held to closer tolerances than ball-and-socket joints.

With a predetermined lost motion tolerance at an axial point of take-up, such as at the ball 71 of 94 of the Olson patent, there can be a considerable multiplication of that tolerance at the location of the piston rod connections 54 or 112. In the present case, the same lost motion at the ends of the

cross axis arms

42 and 48, by geometry, permits only a fraction of the multiplication occuring in Olsons construction. And the cylindrical bearing construction reduces the amount of initial lost motion.

As a result, the amount of noise generated in the present cross-shaft arrangement is minimal, and the variation in compression ratio is brought down substantially to zero.

Various changes and modifications may be made within this invention as will be readily apparent to those skilled inthe art. Such changes and modifications are within the scope and teaching of this invention as defined by the claims appended hereto.

What is claimed'is:

1. In a nutating compressor or like machine of the type having a housing, adrive shaft passing through the housing, a sloping cam on the drive shaft inside the housing and rotated by the shaft, a wobble plate nutated by the rotation of the cam and at least one piston reciprocated within a cylinder in the housing by the plate; the combinationof: a joint support in axial alignment with the cam on the input shaft, mounted in the housing; a cross-axis member, means mounting the cross-axis member on the support for rocking movement about a control axis transverse to the cam axis, said means preventing rotation of the cross-axis member relatively to the support about the cam axis; con nections between the wobble plate and the cross-axis member providing rocking movement of the plate relatively to the cross-axis member about an oscillating axis at right angles to the control axis; means to hold the joint support against rotation. in the housing; and thereby holding the cross-axis member and wobble plate against rotation relatively to the housing; and means to fix the position of the joint support axially in the housing to prevent axial lost motion in the several movable interconnections between the joint support, the cross-axis member and the wobble plate.

2. The combination of claim 1, with frictionless thrust bearings between the cam and the wobble plate.

3. The combination of claim '1 wherein the lastnamed positioning means includes an unyieldable adjusting device to fix the position of the joint support in the housing.

4. The combination of claim 1, with means to prevent radial movement between the cross-axis member and the joint support and between the cross-axis member and the wobble plate.

5. The combination of claim 1, wherein the means mounting the cross-axis member on the support comprises a rock shaft device extending transversely to the axis of the cam and a journal bearing device to receive the cross shaft for rocking movement, one of said devices being on the support and the other device being on the cross-axis member.

6. The combination of claim 5 with means to prevent radial lost motion between the joint support and the cross-axis member.

7. The combination of claim 5, wherein the joint support has opposite radially extending arms, the crossaxis member being disposed between them, and radially extending rock shaft means between the cross-axis member and the arms, the arms embracing the crossaxis member with a fit that permits free rocking movement but prevents relative radial movement between these parts.

8. The combination of claim 1, wherein the connection between the wobble plate and cross-axis member includes a radially extending rock shaft device and a radially extending bearing device for the rock shaft, one of said devices being on the wobble plate and the other on the cross-axis member.

9. The combination of claim 8, with a recess in the wobble plate to receive the cross-axis member, the parts having a close fit to permit free rocking movement but to prevent radial lost motion between them.

10. The combination of claim 1, wherein the joint support has an axial shaft disposed in an axial socket in the housing, and has a bifurcated free end toward the cam, a control shaft mounted in the bifurcations and the cross-axis member to provide rocking of the crossaxis member about an axis transverse to the cam axis, the cross-axis member having second rock shaft means projecting from it along an oscillating axis at right angles to the control shaft, the wobble plate having recesses to receive the rock shaft means to permit rocking of the plate about the oscillating shaft.

11. The combination of claim 10, wherein the wobble plate has a central recess into which the cross head fits with the rock shaft means extending therefrom to engage the plate radially outwardly from the cross head.

12. The combination of claim-l2, with means engaging the end of the joint support for displacing it in its socket toward the wobble plate, thereby to take upv lost motion in the connection.

13. The combination of claim 12, wherein the engaging means includes a spring acting against the end of the joint support and against means fixed to the compressor housing.

14. In a nutating compressor having a housing, a plurality of pistons and piston rods in the front end of the housing, a drive shaft journalled through the rear of the housing; a rotor cam on the shaft, a wobble plate follower adapted to receive the piston rods, anti-friction means for the cam and follower including axial thrust bearing means, an axially slidable non-rotatable joint support on the housing, means for providing rearward axial thrust on the joint support; andtwo-axis means between the support and the wobble plate follower, said two-axis means being disposed to receive the rearward axial thrust of the means providing same on the joint support, and to transmit the thrust through to the follower, the two-axis means also providing for the rocking movement of the follower but preventing rotation thereof relative to the piston rods.

15. The combination of claim 14, wherein the twoaxis means includes abutting shoulders adjacent the axes to prevent radial displacement of its parts and the follower, while it transmits the non-rotation and rearward axial thrust.

Claims

1. In a nutating compressor or like machine of the type having a housing, a drive shaft passing through the housing, a sloping cam on the drive shaft inside the housing and rotated by the shaft, a wobble plate nutated by the rotation of the cam and at least one piston reciprocated within a cylinder in the housing by the plate; the combination of: a joint support in axial alignment with the cam on the input shaft, mounted in the housing; a crossaxis member, means mounting the cross-axis member on the support for rocking movement about a control axis transverse to the cam axis, said means preventing rotation of the cross-axis member relatively to the support about the cam axis; connections between the wobble plate and the cross-axis member providing rocking movement of the plate relatively to the cross-axis member about an oscillating axis at right angles to the control axis; means to hold the joint support against rotation in the housing; and thereby holding the cross-axis member and wobble plate against rotation relatively to the housing; and means to fix the position of the joint support axially in the housing to prevent axial lost motion in the several movable interconnections between the joint support, the cross-axis member and the wobble plate.

3. The combination of claim 1 wherein the last-named positioning means includes an unyieldable adjusting device to fix the position of the joint support in the housing.

7. The combination of claim 5, wherein the joint support has opposite radially extending arms, the cross-axis member being disposed between them, and radially extending rock shaft means between the cross-axis member and the arms, the arms embracing the cross-axis member with a fit that permits free rocking movement but prevents relative radial movement between these parts.

10. The combination of claim 1, wherein the joint support has an axial shaft disposed in an axial socket in the housing, and has a bifurcated free end toward the cam, a control shaft mounted in the bifurcations and the cross-axis member to provide rocking of the cross-axis member about an axis transverse to the cam axis, the cross-axis member having second rock shaft means projecting from it along an oscillating axis at right angles to the control shaft, the wobble plate having recesses to receive the rock shaft means to permit rocking of the plate about the oscillating shaft.

12. The combination of claim 12, with means engaging the end of the joint support for displacing it in its socket towarD the wobble plate, thereby to take up lost motion in the connection.

14. In a nutating compressor having a housing, a plurality of pistons and piston rods in the front end of the housing, a drive shaft journalled through the rear of the housing; a rotor cam on the shaft, a wobble plate follower adapted to receive the piston rods, anti-friction means for the cam and follower including axial thrust bearing means, an axially slidable non-rotatable joint support on the housing, means for providing rearward axial thrust on the joint support; and two-axis means between the support and the wobble plate follower, said two-axis means being disposed to receive the rearward axial thrust of the means providing same on the joint support, and to transmit the thrust through to the follower, the two-axis means also providing for the rocking movement of the follower but preventing rotation thereof relative to the piston rods.

15. The combination of claim 14, wherein the two-axis means includes abutting shoulders adjacent the axes to prevent radial displacement of its parts and the follower, while it transmits the non-rotation and rearward axial thrust.