US2973137A

US2973137A - Cam piston two-stage compressor

Info

Publication number: US2973137A
Application number: US787610A
Authority: US
Inventors: Raymond W Jensen
Original assignee: Garrett Corp
Current assignee: Garrett Corp
Priority date: 1959-01-19
Filing date: 1959-01-19
Publication date: 1961-02-28
Anticipated expiration: 1978-02-28
Also published as: GB904820A; GB904821A

Description

Feb. 28, 1961 R. w. JENSEN 2,973,137

CAM PISTON TWO-STAGE COMPRESSOR Filed Jan. 19, 1959 2 Sheets-Sheet 1 INVENTOR. RA YMOND h. JENSEN @WMWWM I A TTORNE Y Feb. 28, 1961 R. w. JENSEN 2,973,137

CAM PISTON TWO-STAGE COMPRESSOR Filed Jan. 19, 1959 2 Sheets-Sheet 2 N INVENTOR.

RA YMOND M. JENSEN A TTORNEY CAM PrsroN TWO-STAGE coMPREssoR Filed Jan. 19, 1959, Ser. No. 787,610

7 Claims. (Cl. 230-200) This invention relates to compressors and more particularly to compressors of the multistage, positive displacement type.

Generally, a device of the class comprehended by the present invention comprises a plurality of synchronously driven, reciprocating pistons disposed in a housing. These pistons are supported and caused to rotate by a common drive shaft. Means are employed with the pistons to etfect reciprocation thereof with rotation of the shaft, thus causing compressible fluid to be drawn into a first-stage compression section. Valves automatically direct the fluid to flow from said first-stage section, through passage means to subsequent sections, and then to an outlet.

An object of the above-mentioned construction is to provide an extremely compact compressor capable of producing high pressures and having a relatively large output capacity.

Another object of the invention is to provide a compact auxiliary compressor for jet aircraft and missiles.

Another object ofthis invention is to provide a compressor comprising cam-operated pistons disposed conciprocating pistons to cause flow of fluid from an inlet through various stages of compression to an outlet.

A still further object of this invention is to provide a cam piston operated compressor having a hollow drive shaft which communicates with breather means to relieve certain areas of the compressor from undesirable pressure and conduct heat from said shaft.

A still further object of the present invention is to provide passage means, in a cam piston operated compressor, which establishes communication between the interior of the piston components of a compressor and a source of coolant to conduct heat from said pistons.

These and other objects and advantages of the present invention will become apparent to persons skilled in the art from a reading of the following description, together with the attached drawings, wherein:

Figure 1 represents a longtudinal sectional view of a device constructed in accordance with the present invention, portions of certain parts thereof being shown in elevation;

Fig. 2 represents a transverse sectional view of the device taken on line 22 of Fig. 1; and

Fig. 3 represents a transverse sectional view of the device taken on line 3-3 of Fig. 1.

Patented Feb. 28, 1961 With particular reference to Fig. 1, the drawing shows a two-piece housing which is represented generally by the reference numeral 1. Each piece, 2 and 3, of the housing 1 contains a bore 4 and 5, respectively, the diameter of the bore 4 of the first piece 2 being greater than that of the bore 5 in the second piece 3. The two pieces 2 and 3 of the housing 1 are joined and held together by screws 6, and the. respective bores 4 and 5 therein are locked in concentric alignment by the engagement of an annular land 7 with a matching groove 8.

Each of the bores 4 and 5 in the housing 1 receives a piston 10 and 11, respectively, which is disposed for combined rotation and reciprocation therein. These pistons 10 and 11 are provided with grooves 12 and 13 to receive suitable sealing rings 14 and 15, and said pistons also include circumferentially disposed, undulating, annular cam grooves 16 and 17 for engagement with

followers

18 and 20.

The

followers

18 and 21 extend radially inward from

bosses

21 and 22 which are formed on the housing 1; thus,

bosses

21 and 22 are arranged in two circumferential rows on the housing 1, each row being disposed intermediate the ends of the pieces 2 and 3 of the housing 1. The

bosses

21 and 22, in each row, are circumferentially spaced degrees apart, as shown in Figs. 2 and 3.

The

followers

18 and 21 comprise conventional antifriction bearings 23 retained in position by bolts 24 which extend therethrough and engage the internal threads of cup-shaped nuts 25. The nuts 25 are also provided with external threads which are engaged by corresponding threads formed in sleeves 26, said sleeves being pressed into the

bosses

21 and 22.

Both of the pistons 10 and 11 contain centrally disposed, axially aligned, cylindrical openings 27 and 28 and a plurality of spaced, axially extending, semicylindrical spline grooves 30 and 31 which are formed in the walls of said openings 27 and 28.

A hollow, composite drive shaft 32 extends longitudinally of the housing 1 to traverse the opening 27 'in one piston 10 and project therefrom into the opening 28 of the other piston 11. The drive shaft 32 comprises a hollow, cylindrical coupling section 33 which includes internal splines 34 formed at one end thereof, the end opposite said internal splines 34 being formed to include a plurality of spaced, axially directed, radially projecting lands 35, which define parallel, semicylindrical spline grooves 36 therebetween. A hollow, cylindrical centerpiece 37 abuts the last-mentioned end of the coupling section 33 and extends axially therefrom to an annular collar 38. This collar 38 is also formed to include a plurality of spaced, axially directed, radially projecting lands 40, which define parallel, semicylindrical spline grooves 41 therebetween. A bolt 42 extends axially through the collar 38 and centerpiece 37 to have the threaded terminus 43 thereof engage a threaded portion 44 in the coupling section 33. A set of pins 45 extend axially from each end of the centerpiece 37 into the collar 38 and coupling section 33 to maintain alignment and prevent relative rotation between the shaft components.

The spline grooves 36 and 41 in the shaft 32, and the corresponding grooves 36 and 31 in the pistons 10 and 11, cooperate to define a plurality of spaced cylindrical openings which receive sets of ball elements 46. These elements 46 establish a driving connection between the shaft 32 and the pistons 10 and 11, which is capable of transmitting any rotary motion of the shaft 32 to the pistons 10 and 11 and simultaneously allowing free axial movement of the latter for a limited distance. Cylindrical sleeves 47 are pressed into the openings 27 and 28 of the pistons 10 and 11 to be closely fitted around the shaft 32 for sliding contact with sealing rings 48, which 3. are disposed in grooves 59 formed near the ends of the centerpiece 37.

It will be noted that when the pistons and 11 are connected to the' drive shaft 32, as above described, the cam grooves 16 and 17, of the pistons 19 and 11, are phased, with respect to their followers, to cause axially directed countermovernent of the pistons 13. and 11 upon their rotation.

A circular block 51 having a bore 52 and a counterbore 53 is disposed in the open end of the large bore 4 in the housing 1. The bore 52 and counterbore 53 in the block 50 cooperate to form a shoulder 54 to act as a stop for an antifriction bearing 55, which is positioned in the counterbore 53 and retained therein by a snap-ring 56 disposed in a groove 57 formed adjacent the open end of the counterbore 53. The bearing 55 provides a substantially frictionless support for the drive shaft 32 which projects concentrically therethrough.

A rotary seal member 58 is pressed on the drive shaft 32 and is disposed for rotation in the bore 52 of the block 51. A sealing ring 60 fits into a groove 61 formed in the seal 58 and makes fluid-sealing, sliding contact with the wall of bore 52 in which it is disposed.

A counterbore 62 is formed in the end of the housing 1, opposite the end which contains the block 51, for receiving a disc-shaped valve plate 63 and the annular projection 64 of an end cover 65 which is attached to the housing 1 by screws 66. The valve plate 63 contains a plurality of axially directed passages 67 and an annular groove 68 which communicates with the passages 67 and faces the end of the housing 1.

A floating, ring-shaped check valve 70 is loosely positioned in the space between the surfaces of the groove 68 in the valve plate 63 and the end of the housing 1, and another smaller ring-shaped check valve 71 is loosely disposed in a space between the valve plate 63 and the end cover 65. A third floating, ring-shaped check valve 72 is disposed adjacent the head of the large piston 10 and retained in loose association therewith by a snap-ring 73 which fits into a groove 74 formed in one of the sleeves 47.

With the pistons 10 and 11 disposed in the housing 1, as shown in Fig. 1 of the drawings, afirst-stage chamber 75 is defined between the two pistons 10 and 11 and a second-stage chamber 76 is defined between the small piston 11 and the valve plate 63. A screened inlet 77 is provided in the wall of the housing 1 and communicates via the cam groove 16, in the large piston 10, and a plurality of axially directed passages 78 which are formed in the head portion of the same piston 10, with the first-stage chamber 75. Communication between the first-stage chamber 75 and the second-stage chamber 76 is established by a plurality of longitudinally directed passages 79, which are formed in the section of the housing 1 surrounding the small bore 5. An outlet means 80 is provided in the end cover 65 and communicates with the second-stage chamber 76 via the passages 67 in the valve plate 63.

A third chamber 81 is defined between the large piston 1t and the block Sll. Breather means for establishing communication between this third chamber 81 and the ambient region at the exterior of the housing 1 comprises a plurality of radially directed passages 82 which extend from the exterior of the housing 1 to an annulus 83 formed in the seal 58. Short, radially directed passages 84 extend from the above-mentioned annulus 83 to another annulus 85 which communicates with passages 86 provided in the coupling section of the shaft 32 and communicating with the open end of a bore 87 in the bolt 42. A set of radially directed openings 88 are provided in the bolt, near the head thereon, to establish communication between the bore 87 and a longitudinal, cylindrical passage 90 formed by a space between the bolt 42 and the inner surface of the shaft 32. A second set j% of openings 91 extend from the passage 91) to the chamber 81 to complete the breather circuit.

A number of vent passages 92 are formed at the base of the cam groove 17 in the small piston 11, and establish communication between an enclosed space 93 located in the internal head portion of the piston 11 and the ambient atmosphere outside of the housing 1, via radially directed passages 94 formed in the wall of the housing 1 and extending from the cam groove region 17 to the exterior of the housing.v

In operation, the internal splines 34' 0f the coupling section 33 are engaged with a source of rotary power, not shown, for causing rotation of the shaft 32 together with the pistons 10 and 11 which are connected thereto by the ball spline means. The shapes of the undulating cams 16 and 17 are such that their coaction with the

followers

18 and 20, when the pistons are rotated, will cause simultaneous, oppositely phased reciprocation of the'pistons 10 and 11, the direction of movement of the pistons 10 and 11 at any given time depending on the position of the followers 13 and 20 relative to the slopes of the earns 16 and 17.

When the pistons 10 and 11 are moved apart, due to the above-described coaction of the cams 16 and 17 and

followers

18 and 20, the volume of the first-stage chamber 75 will be increased, causing a reduction of pressuretherein. This pressure in the first-stage chamber 75 will create a pressure differential across the check valve 72 which will open, thereby allowing some of the air outside of the housing 1 to be drawn through the inlet 77 to the first-stage chamber 75 via cam groove 16 and the axially directed passages 78. The reduction of pressure in the first-stage chamber 75, via passages 79, will also cause a pressure differential across the check valve 70, causing it to close and block any back-flow of fluid from the second-stage chamber 76 to the first-stage chamber 75.

As the pistons 10 and 11 continue to rotate, their axial movement will be reversed by the coaction of the earns 16 and 17 and the

followers

19 and 20 to decrease the volume of the first-stage chamber 75 and increase the volume of the second-stage chamber 76. As the volume of the first-stage chamber 75 starts to decrease, the fluid therein will be compressed, creating a pressure differential across the valve 72, which will move it to the closed position and block any flow of fluid from the first-stage chamber '75 toward the inlet 77. Continued movement of the pistons 10. and 11 toward one another will force some of the fluid in chamber 75 through the axially directed passages 79 to open the valve 70 and allow flow of fluid to the second-stage chamber 76. As the pistons 10 and 11 reach the limit of movement toward each other, as determined by the contour of cam grooves 16 and 17, the

followers

18 and 20 will again engage the cams at the opposite sides of grooves 16 and 17 and cause separation of. the pistons 10 and 11, the small piston moving toward the valve plate 63. As the small piston 11 is urged toward the valve plate 63, the volume of the second-stage chamber 76 is decreased, compressing the fluid therein, which will close the check valve 70 and block the flow of fluid from the second-stage chamber 76 back to the first-stage chamber 75. Any increase in pressure in the secondstage chamber 76 will cause a pressure differential across the check valve 71, causing it to open to allow flow of fluid from the second-stage chamber 76 through the axially directed passages 67 and the outlet means 80. When the pressure in the outlet 8'1)v exceeds that in the second-stage chamber 76, valve 71 will close. It will be seen, therefore, that the valves 70, 71 and 72 cooperate with the pistons 10 and 11, upon reciprocation of the latter, to cause flow of fluid from the inlet 77 through the various stages of compression to the outlet.

I claim':

1. A compressor comprising: a housing; first and second piston means disposed for combined rotation and reciprocation in said housing, said pistons and housing sewing to define a first chamber between said pistons, a second chamber between said second piston and said housing and a third chamber between said first piston and said housing; shaft means provided with a longitudinally extending bore, said shaft being supported for rotation in said housing and extending longitudinally thereof for driving connection with said pistons; means on said housing and pistons for effecting reciprocation of said pistons upon the rotation of said shaft; breather passage means connecting said third chamber with an ambient region outside said housing via the bore of said shaft; means for establishing communication between a source of fluid and said first chamber; passage means connecting said first and second chambers; outlet means leading from said second chamber; and valve means operative upon the reciprocation of said pistons to permit flow of fluid from said source to said first and second chambers and through said outlet.

2. A compressor comprising: a housing; first and second piston means disposed for combined rotation and reciprocation in said housing, said pistons and housing serving to define a first chamber between said pistons, a second chamber between said second piston and said housing, and a third chamber between said first piston and said housing; shaft means containing a longitudinally extending bore and having splined portions thereon, said splined portions being provided to establish a driving connection between said pistons and said shaft and pernfit free axial movement therebetween; means on said housing and pistons for effecting reciprocation of said pistons upon the rotation of said shaft; breather passage means connecting said third chamber with an ambient region outside said housing via the bore of said shaft;

means for establishing communication between a source of fluid and said first chamber; passage means connecting said first and second chambers; outlet means leading from said second chamber; and valve means operative upon the reciprocation of said pistons to permit flow of fluid from said source to said first and second chambers and through said outlet.

3. A compressor comprising: a housing; first and second piston means disposed for combined rotation and reciprocation in said housing, said pistons and housing serving to define a first chamber between said pistons, a second chamber between said second piston and said housing, and a third chamber between said first piston and said housing; shaft means containing a longitudinally extending bore and having splined portions thereon, said splined portions being provided to establish driving connection between said pistons and said shaft allowing free axial movement therebetween; means on said housing and pistons for effecting reciprocation of said pistons with the rotation of said shaft; breather passage means connecting said third chamber with an ambient region outside said housing via the bore of said shaft; means for establishing communication between a source of fluid and said first chamber; passage means connecting said first and second chambers; outlet means which leads from said second chamber; and valve means which, in cooperation with the reciprocation of said pistons, causes fiow of fluid from said source through said outlet.

4. A compressor comprising: a housing;-first and second piston means disposed for combined rotation and reciprocation in said housing, said pistons and housing serving to define a first chamber between said pistons, a second chamber between said second piston and said housing, and a third chamber between said first piston and said housing; shaft means containing a longitudinally extending bore and having splined portions thereon, said splined portions establishing driving connections between said pistons and said shaft and allowing free axial movement therebetween; undulating cams circumferentially disposed on said pistons; follower means fixed to said housing for engagement with said cams, said cams and said followers cooperating to cause reciprocation of said pistons when the latter are rotated; breather passage means connecting said third chamber with an ambient region outside said housing via the bore in said shaft; means for establishing communication between a source of fluid and said first chamber; passage means connecting said first and second chambers; outlet means leading from said second chamber; and valve means operative upon the reciprocation of said pistons to'permit flow of fluid from said source to said first and second chambers and outwardly through said outlet.

5. A compressor comprising: a housing; a first and second piston means disposed for combined rotation and reciprocation in said housing, said pistons and housing serving to define a first chamber between said pistons, a second chamber between said second piston and said housing, and a third chamber between said first piston and said housing; shaft means containing a longitudinally extending bore and having splined portions thereon, said splined portions establishing driving connections between said pistons and said shaft and allowing free axial movement therebetween; undulating cams circumferentially disposed on said pistons; follower means fixed to said housing for engagement with said cams, said cams and said followers cooperating to cause reciprocation of said pistons when the latter are rotated; breather pass-age means connecting said third chamber with an ambient region outside said housing via the bore in said shaft; means for establishing communication between a source of fluid and said first chamber; passage means connecting said first and second chambers; outlet means leading from said second chamber; and check valve means operative upon the reciprocation of said pistons to permit flow of fluid from said source to said first and second chambers and outwardly through said outlet.

6. A compressor comprising: a housing; first and second differential piston elements disposed for combined rotary and reciprocatory movement in said housing, said piston elements and housing serving to define a first chamber betweenthe piston elements, a second chamber between the second piston element and said housing, and a third chamber between the first piston element. and said housing, said second piston element having a fourth chamber formed internally thereof; shaft means provided with a longitudinally extending passage communicating at one end with said third chamber and with the atmosphere outside of said housing at the other end, said shaft means being supported at one end for rotation in said housing and projecting through said first piston element into the fourth chamber in the second piston element; means forming a rotary driving connection between said shaft and piston elements, said means permitting relative longitudinal movement between said piston elements and shaft means; means on said housing and piston elements for effecting reciprocation of the piston elements upon rotation of said shaft means; additional passage means establishing communication between said fourth chamber and the exterior of said housing; passage means establishing communication between a source of fluid and said first chamber and between the latter and said second chamber, said housing having an outlet port leading from said second chamber; and valve means operative upon reciprocation of said piston elements to permit flow of fluid from the source thereof to said first and second chambers and through said outlet, reciprocation of said piston elements also causing air flow into and out of said third chamber through the passage in said shaft means and air flow into and out of said fourth chamber through said additional passage means.

7. A compressor comprising: a housing; first and second differential piston elements disposed for combined rotary and reciprocatory movement in said housing, said piston elements and housing serving to define a first 7 chamber between the piston elements, a second chamber between the second piston element and said housing, and a third chamber between the first piston element and said housing, said second piston element having a fourth chamber formed internally thereof; a composite shaft means supported at one end in said housing for rotary movement, said shaft means projecting through said first piston element and into the chamber in said second piston element, said shaft means providing a passage extending substantially twice the length of said shaft means and establishing communication between said third chamber and the atmosphere outside of said housing; means forming a rotary driving connection between said shaft and piston elements, said means permitting relative longitudinal movement between said piston elements and shaft means; means on said housing and piston elements for efiecting reciprocation of the piston elements upon rotation of said shaft means; additional passage means establishing communication between said fourth chamber and the exterior of said housing; passage means establishing communication between a source of fluid and said first chamber and between the latter and said second chamber, said housing having an outlet port leading from said second chamber; and valve means operative upon reciprocation of said piston elements to permit flow of fluid from the source thereof to said first and second chambers and through said outlet, reciprocation of said piston elements also causing air flow into and out of said third chamber through the passage in said shaft means and air flow into and out of the fourth chamber through said additional passage means.

References Cited in the file of this patent UNITED STATES PATENTS 179,689 Durre July 11, 1876 415,822 Sergeant Nov. 26, 1889 949,940 Myers Feb. 22, 1910 1,513,302 Wahlstrom Oct. 28, 1924 1,613,147 Wahlstrom Jan. 4, 1927 1,649,196 Sandage Nov, 15, 1927