US3312239A

US3312239A - Crosshead assembly

Info

Publication number: US3312239A
Application number: US375726A
Authority: US
Inventors: Fred F Chellis
Original assignee: Arthur D Little Inc
Current assignee: Arthur D Little Inc; Azenta Inc
Priority date: 1964-06-17
Filing date: 1964-06-17
Publication date: 1967-04-04
Anticipated expiration: 1984-04-04

Description

April 4, 1967 F. F. CHELLIS 3,312,239

CROS SHEAD AS SEMBLY Filed June 17, 1964 '4 Shets-Sheet a F i g 3 INVENTOR.

Fred F. Chellis Arforney April 4, 1967 F. F. CHELLIS 3,312,239

I v CROSSHEAD ASSEMBLY I Filed June 17, 1964 4 Sheets-Sheet 4 N M lo INVENTOR. Fred F. Challis United States Patent chusetts Filed June 17, 1964, Ser. No. 375,726

6 Claims. (Cl. 137-560) This invention relates to fluid regulating apparatus and more particularly to apparatus which is capable of controlling the flow of fluid into, within, and out of a refrigerator where such control must be extremely accurate to insure eflicient performance of the cycle on which the refrigerator operates.

There has recently been developed new basic refrigerator cycles which depend upon the introduction of a highpressure expansible fluid into a refrigerator, its transfer within the refrigerator for initial cooling by regeneration, and its subsequent expansion and further cooling with discharge as low-pressure fluid from the refrigerator. The basic cycle, along with modifications and improvements, is described in detail in U.S. Patents 2,906,101, 2,966,- 035, 3,115,015, and 3,115,016, as well as in copending application Ser. Nos. 280,577, now Patent No. 3,148,512, 375,721, new Patent No. 3,218,815, and 375,854. These refrigerator cycles and that portion of the apparatus in which the regenerative cooling and expansion takes place are not part of this invention. The apparatus of this invention is rather an improved means for providing the proper valving sequence and displacer motion for control of the fluid into, within, and out of the refrigeration apparatus; and it will be understood that the apparatus of this invention (conveniently referred to as a crosshead assembly) can be adapted for use in the apparatus disclosed in the above-identified patents and copending applications. The crosshead assembly of this invention is, however, particularly suitable for use in controlling the fluid flow in a refrigerator described in copending application Ser. No. 375,721, and as an integral component of the cryogenic liquefier described in Ser. No. 375,854, all of the applications referred to being assigned to the same assignee as this application.

A number of devices are available which are capable of controlling the flow of fluid in two directions, but in general the greater the accuracy of control that is achieved, the more complicated becomes the apparatus for doing it. Moreover, when it is necessary to add valving means and a synchronously timed means for moving a displacer, the prior art equipment becomes even more complicated and expensive to build. It would therefore be desirable to have available apparatus which is capable of achieving the type of fluid flow control required and which at the same time is relatively simple to construct and extremely reliable in its operation. This latter quality of reliability becomes very important when the crosshead is to be incorporated in a refrigerator or liquefier which is to be installed in equipment, such as spacecraft, required to operate reliably over extended periods of time without maintenance.

It is therefore a primary object of this invention to provide an apparatus which is capable of accurately controlling the flow of fluid into, within, and out of an enclosed space, the control incorporating valving means and means for moving a displacer. It is another objective of this invention to provide an apparatus of the character described which is relatively'simple to build, and lends itself readily to fine adjustments both with respect to valve timing and displacer motion. It is yet another object of this invention to provide apparatus of the character described which may be incorporated into a refrigerator or liquefier which is required to operate over extended pcriods of time without maintenance. Other objects of the invention will in part be obvious and will in part be apparent hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objectives of the invention reference should be had to the following detailed description taken in connection with the accompanying drawings in which FIG. 1 is a side elevational view of the crosshead assembly with the enclosing structure shown in crosssection;

FIG. 2 is a cross-section of the crosshead assembly taken along line 2-2 of FIG. 1;

FIG. 3 is a cross-section of the crosshead assembly taken along line 33 of FIG. 1;

FIG. 4 is a cross-section of the crosshead assembly taken along line 4--4 of FIG. 1; and

FIG. 5 is a cross-section of a crosshead assembly taken along line 55 of FIG. 4.

The crosshead assembly of this invention incorporates poppet values which are driven in the proper sequence by unique adjustable cam followers, and a Scotch yoke which is synchronized with the valve operation for imparting the proper up and down motion to a displacer within the refrigerator, this motion achieving the desired fluid flow control within the refrigerator.

FIG. 1 illustrates the general arrangement of the crosshead assembly components. This assembly will be seen to comprise a crankcase housing 10 mounted in fluid tight relationship on a crankcase block 11 which in turn is mountedthrough suitable sealing means to make a fluid-tight connection with a refrigerator support 12 and the cylindrical wall 13 of the refrigerator itself. Within the refrigerator a displacer 14 (only a fragment of which is shown) moves up and down to define within the enclosure two or more fluid volumes one of which is shown as the upper warm volume 15. The remaining portion of the refrigerator is not illustrated here since it isnot part of the invention and reference should be had to copending application Ser. No. 375,721, which illustrates a typical refrigerator for which this crosshead assembly is suitable.

Movement of the displacer and of the valves is accomplished by means of an electrical motor (not shown) which is located within motor housing 16, which in turn is afiixed to the crankcase housing 10 and made fluid- V tight through the use of a front plate 17 and a back plate 18 held in position by bolts 19. Thus the assembly as illustrated in FIG. 1 is fluid-tight for reasons which will be explained subsequently. The displacer 14 is given suitable up and down motion through a suitable connection between motor shaft 21 and displacer rod 22 acting through a bearing 23 which is positioned in a Scotch yoke 24. The details of this driving mechanism will be described in detail in connection with FIGS. 2 and 3.

The required motion is imparted to poppet valves through the up and down motion of an inlet valve cam follower 26 which is driven by inlet cam bearing 27 and a discharge valve cam follower 28 which is driven by a discharge cam bearing 29. The crankcase 32 is sealed in front by means of a plastic window assembly 33 and suitable sealing ring 34. This plastic window assembly can be moved back and forth and rotated, for purposes described below, by means of a knurled piece 35.

The mechanism by which the displacer is moved up and down in proper sequence is illustrated in detail in FIGS. 2 and 3. FIG. 2 illustrates the relationship between the motor shaft 21 and the auxiliary shaft associated with the Scotch yoke bearing. Attached to motor shaft 21 is a collar 49 which is made integral with an auxiliary off-center shaft 41. The bearing 23 which drives the Scotch yoke 24 is mounted on this auxiliary shaft 41. Mounted on collar 49 is a second collar 42 and the entire collar assembly is permanently fixed to the motor shaft through the use of a key pin 43. The collar assembly rotates in a back plate 44 which completes the crankshaft enclosure. Finally, it will be seen in FIG. 2 that the bearing 27 associated with the inlet valve is mounted on collar 40 and the bearing 29 which is associated with the discharge valve is mounted on collar 42. These bearings are mounted slightly eccentric to each as is apparent from FIG. 1.

Turning now to FIG. 3 it will be seen that rod 22 is mechanically affixed to displacer 14 through a suitable means such as pin 45. It moves within a block 11 through a bushing 46 and a seal housing 47 which has associated with it sealing

rings

48 and 49. There must of course be complete fluid isolation between chamber in the refrigerator and the crankcase 32 of the crosshead assembly inasmuch as all fluid flow must be controlled through valve means. The upper extension of rod 22 has associated with it a bushing 50. It r'ecipr'ocates within an enclosed volume 52 which is defined by an extension 53 of the crankcase housing. This extension is in turn made fluid-tight through the use of suitable screw 54 with sealing rings 55. Bushing 50 has a flattened area on its outside surface to insure free fluid flow around the bushing 50 into chamber 52 so that at no time will there be a pressure differential between 32 and 52. Finally, the Scotch yoke 24 has on one side a groove 56, the purpose of which is to engage a pin 57, mounted in housing 10, to prevent any rotational movement of the yoke or the rod. Movement of the rod 22 and of the

cam followers

26 and 28 may be effected externally by forcing the plastic window assembly 33 (FIG. 2) inwardly until shaft 41 is engaged in a recess 58 in the plastic window assembly. By turning the knurled piece 35 it is ossible to rotate the

shafts

41 and 21 thus achieving external adjustments.

The manner in which the high-pressure fluid is introduced into and low-pressure fluid is withdrawn from chamber 15 through the poppet valves is illustrated in detail in FIGS. 4 and 5. However, before describing the apparatus in detail it will be helpful to trace the fluid flow path. High-pressure fluid is brought in by line 60 through conduit 61 and its flow controlled by high-pressure valve 62. The high-pressure fluid passing through valve 62 enters chamber 15 by way of conduit 63. The low-pressure fluid which is to be discharged from the refrigerator by way of chamber 15 passes first through conduit 64, then through low-pressure valve 65 and finally 7 through conduit 66 to enter the crankcase interior 32.

Thus it will be apparent why the crankcase must be fluid tight since it is an integral part of the fluid flow path. From crankcase 32 the fluid flows through ports 67 (one of which is shown) into the motor housing 16 and then by way of conduit 68 (FIG. 1)'to the compressor where it is compressed prior to its recycling by way of conduit '60 into the refrigerator. In passing through motor housing 16, the low-pressure fluid cools the motor.

FIG. 4 illustrates the high-pressure valve in detail. Inasmuch as the low-pressure valve 65 is identical with the high-pressure valve 62, only one valve system need be described. Valve block 72 is sealed into the crankcase block 11 through the use of sealing rings 73, 74, and 75. The main valve body 76 is actuated downwardly by valve rod 77. It extends into a fluid volume 78 and is normally held in the closed position shown in FIG. 4 by means of a spring 79 which extends into a recess 80 and acts on valve body 76 to force it upwardly. When the valve body is in its lower position by reason of force applied through valve rod 77, fluid flows upwardly into volume 82 and then in o conduit 63 through passage 83.

In a similar manner low-pressure fluid flows upwardly through conduit 64 through low-pressure valve 65, which is similarly actuated, and then by way of conduit 66 out of the refrigerator.

The actuation of the valve rods 77 is achieved by two cam followers, the one for the inlet valve being designated by numeral 26, and the one for the discharge valve by numeral 28 (see FIG. 5). As in the case of the valves these actuation mechanisms are identical and need be described in detail for the inlet valve only. The cam follower 26 is in effect a rocker arm formed of an upper prong 88 and a lower prong 89 which define between them at one end a gap of varying cross-section, and which are integral at the other end. Movable within this gap of varying cross-section is an adjusting pin 90 which is attached to a horizontal rod 91 which in turn may be moved back and forth by means of screw 92 to increase or decrease the distance between prongs 88 and 89. Hence the movement of rod 91 is used to adjust the degree of displacement of valve rod 77. This achieves an extremely fine degree of adjustment which is important in a device such as this. The cam follower 26 is mounted on a suitable pivot pin 93 and is given its downward motion to open the valve by contact with the surface of bearing 27.

Finally FIG. 4 illustrates the means by which the crankcase block can be conveniently attached to the refrigerator support plate 12 through the use of suitable keyed pieces 97 which engage a groove 98 in the block 11 and which are held in place by means of screws 99.

It will be seen from the above description of the crosshead assembly of this invention that it is possible to synchronize the movement of the inlet and discharge valves with the movement of the displacers within the refrigerator so that high-pressure fluid is admitted while the displacer is moving upwardly and dwelling in an uppermost position and to open the discharge valve while the displacer is moving downwardly and remaining in its lowermost position. It Will be appreciated that this is a very general and simplified statement of the desired fluid flow pattern which must be accomplished in a refrigeration cycle such as that disclosed in US. Patent 2,966,035. It is of course within the scope of this invention to adjust the movements of the valves and the displacer rod to achieve any desired fluid flow pattern. A further examination of the description and drawings will show that the crosshead assembly of this invention achieves the required fluid flow into, within, and out of a refrigerator with a relatively simple apparatus. However, accuracy of adjustment and control and reliability of operation are not sacrificed in the achievement of this simplicity.

It will thus be seen that the objects set forth above among those made apparent from the preceding description are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

I claim:

1. A crosshead assembly capable of controlling the flow of a fluid into and out of an enclosure and of controlling the circulation of said fluid within said enclosure through the motion of a member movable within said enclosure, comprising in combination '(a) motor means adapted to rotate a motor shaft;

(b) a motor housing;

(0) la crankcase block aflixed in fluid-tight relationship to said enclosure;

(d) a crankcase housing forming withsaid motor housing and said crankcase block a fluid-tight crankcase;

(e) fluid conduit means adapted to conduct high-pressure fluid into and low-pressure fluid out of said enclosure;

(f) mechanically actuated high-pressure inlet :and lowpressure exhaust fluid control valves associated with said fluid conduit means, located within said crankcase block and adapted to control the flow of said high-pressure and said w-pressure fluid;

(g) a driving rod associated with said movable member in said enclosure and extending through said crankcase block into said crankcase;

(h) an auxiliary shaft aflixed to said motor shaft, through first collar means, and eccentrically mounted thereto;

(i) second collar means mounted on said motor shaft adjacent to said first collar means and eccentric thereto;

(j) driving rod moving means within said crankcase and comprising a Scotch yoke and an associated hearing cam mounted on said auxiliary shaft;

(k) inlet valve actuating means affixed to said first collar means and eccentrically mounted thereto; and

(1) outlet valve actuating means affixed to said second collar means.

2. A crosshead assembly in accordance with claim 1 wherein said fluid conduit means comprises (1) a high-pressure conduit communicating between an external source of said high-pressure fluid and said enclosure by way of said high-pressure inlet fluid control valve, and

(2) a low-pressure path communicating between external discharge means and said enclosure, said path comprising in combination said low-pressure exhaust fluid control valve, said crankcase, and said motor housing, whereby said motor is located in said fluid path and is cooled by said low-pressure fluid.

3. A crosshead assembly in accordance with claim 1 wherein each of said fluid control valves is a poppet valve having spring means associated therewith adapted to apply a positive force thereto, said force being in opposition to force applied by said valve actuating means associated therewith.

4. A crosshead assembly in accordance with claim 3 wherein each of said poppet valves has a valve rod extending into said crankcase; and said valve actuating means comprises (1) a rocker arm engaging said valve in force-applying relationship, and

(2) a bearing cam mounted on its associated collar means and adapted to apply force to said rocker arm over those periods when said valves are to be opened.

5. A crosshead assembly in accordance with claim 4 wherein said rocker arm comprises two prongs and means for adjusting the distance between said prongs whereby the displacement of said valve rod may be adjusted.

6. A crosshead assembly in accordance with claim 1 wherein said crankcase housing has as a portion of one side a circular transparent plastic assembly having in its inner surface a recess adapted to engage the end of said auxiliary shaft and being rotatable and movable inwardly thereby to engage said end of said auxiliary shaft whereby said shaft may be turned for adjustment by a force external of said crankcase.

References Cited by the Examiner UNITED STATES PATENTS 2,966,034 12/1960 Gifford 626 2,979,917 4/1961 Meagher 62508 M. CARY NELSON, Primary Examiner.

W. R. CLINE, Assistant Examiner.

Claims

1. A CROSSHEAD ASSEMBLY CAPABLE OF CONTROLLING THE FLOW OF A FLUID INTO AND OUT OF AN ENCLOSURE AND OF CONTROLLING THE CIRCULATION OF SAID FLUID WITHIN SAID ENCLOSURE THROUGH THE MOTION OF A MEMBER MOVABLE WITHIN SAID ENCLOSURE, COMPRISING IN COMBINATION (A) MOTOR MEANS ADAPTED TO ROTATE A MOTOR SHAFT; (B) A MOTOR HOUSING; (C) A CRANKCASE BLOCK AFFIXED IN FLUID-TIGHT RELATIONSHIP TO SAID ENCLOSURE; (D) A CRANKCASE HOUSING FORMING WITH SAID MOTOR HOUSING AND SAID CRANKCASE BLOCK A FLUID-TIGHT CRANKCASE; (E) FLUID CONDUIT MEANS ADAPTED TO CONDUCT HIGH-PRESSURE FLUID INTO AND LOW-PRESSURE FLUID OUT OF SAID ENCLOSURE; (F) MECHANICALLY ACTUATED HIGH-PRESSURE INLET AND LOWPRESSURE EXHAUST FLUID CONTROL VALVES ASSOCIATED WITH SAID FLUID CONDUIT MEANS, LOCATED WITHIN SAID CRANKCASE BLOCK AND ADAPTED TO CONTROL THE FLOW OF SAID HIGH-PRESSURE AND SAID LOW-PRESSURE FLUID; (G) A DRIVING ROD ASSOCIATED WITH SAID MOVABLE MEMBER IN SAID ENCLOSURE AND EXTENDING THROUGH SAID CRANKCASE BLOCK INTO SAID CRANKCASE; (H) AN AUXILIARY SHAFT AFFIXED TO SAID MOTOR SHAFT, THROUGH FIRST COLLAR MEANS, AND ECCENTRICALLY MOUNTED THERETO; (I) SECOND COLLAR MEANS MOUNTED ON SAID MOTOR SHAFT ADJACENT TO SAID FIRST COLLAR MEANS AND ECCENTRIC THERETO; (J) DRIVING ROD MOVING MEANS WITHIN SAID CRANKCASE AND COMPRISING A SCOTCH YOKE AND AN ASSOCIATED BEARING CAM MOUNTED ON SAID AUXILIARY SHAFT; (K) INLET VALVE ACTUATING MEANS AFFIXED TO SAID FIRST COLLAR MEANS AND ECCENTRICALLY MOUNTED THERETO; AND (L) OUTLET VALVE ACTUATING MEANS AFFIXED TO SAID SECOND COLLAR MEANS.