US3801167A

US3801167A - Device for centrally guiding the working piston in the working cylinders of high-pressure compressors or pumps

Info

Publication number: US3801167A
Application number: US00132133A
Authority: US
Inventors: A Strebel
Original assignee: Maschinenfabrik Burckhardt AG
Current assignee: Burckhardt Compression AG
Priority date: 1970-04-07
Filing date: 1971-04-07
Publication date: 1974-04-02
Anticipated expiration: 1991-04-02
Also published as: NL152634B; BE765312R; GB1339962A; JPS5225561B1; IT993522B; NL7104538A; FR2089008A6

Abstract

A device for centrally guiding the working piston in the working cylinders of high-pressure compressors or pumps, wherein the faces of the working cylinders are releasably fitted to a lantern which is fixedly or releasably connected to the drive frame, and the working pistons are releasably fitted to the guide pistons which are guided inside the lantern and are connected to the crosshead via a fixedly fitted flexible stem. An intermediate piece with a flexible stem is centrally inserted in a co-axial bore inside the guide piston between the working piston and the supporting surface at the base of the bore. After the working piston has been fitted it is bought into non-positive connection with the guide piston in the supporting surfaces. When any axial departure occurs as a result of the oblique position of the guide piston the reaction force acting on the working piston, while it is moving longitudinally inside the bore of the working cylinder, is reduced to such an extent that said force is very largely prevented from having any detrimental effect on the sealing and guiding parts inside the working cylinder or on the working piston itself.

Description

United States Patent [191 Strebel Apr. 2, 1974 [75] Inventor: Albert Strebel,Binningen,

Switzerland [73] Assignee: Maschinentabrik Burckhardt AG,

Basle, Switzerland 22 Filed: Apr. 7, 1971 21 Appl. No.: 132,133

[30] Foreign Application Priority Data Apr. 7, 1970 Switzerland 5127/70 [52] US. Cl. 417/90, 308/3 CH [51] Int. Cl Fl6j 15/18 [58] Field of Search 308/3 CH; 287/20 P;

[56] References Cited UNITED STATES PATENTS 6/1972 Tyson 287/20 P 12/1971 Bimba 287/20 P 6/1952 France 92 255 Primary Examiner-Charles J. Myhre Assistant Examiner-R. H. Lazarus I Attorney, Agent, or Firm-Wenderoth, Lind & Ponack [57] ABSTRACT A device for centrally guiding the working piston in the working cylinders of high-pressure compressors or pumps, wherein the faces of the working cylinders are releasably fitted to a lantern which is fixedly or releasably connected to the drive frame, and the working pistons are releasably fitted to the guide pistons which are guided inside the lantern and are connected to the crosshead via a fixedly fitted flexible stem. An intermediate piece with a flexible stem is centrally inserted in a co-axial bore inside the guide piston betweenthe working piston andthe supporting surface at the base of the bore. After the working piston has been fitted it is bought into non-positive connection with the guide piston in the supporting surfaces. When any axial departure occurs as a result of the oblique position of the guide piston the reaction force acting on the working piston, while it is moving longitudinally inside the bore of the working cylinder, is reduced to such an extent that said force isvery largely prevented from having any detrimental effect on the sealing and guiding parts inside the working cylinder or on the working piston itself.

' 12 Claims, 4 Drawing Figures :"AIENTEB APR '2 H74 SHEEI 1 0F 4 I INVENTOR ALBERT STREBEL BY z mez I ATTORNEYS INVENTOR ALBERT STREBEL ATTORNEYS PATENTEDAPR 21974 SHEEI 3 OF 4 R Y L ME E N NB R Wm Q n 15 29 SHEET 0F 4 FIG.4

DEVICE FOR CENTRALLY GUIDING THE WORKING PISTON IN THE WORKING CYLINDERS OF HIGH-PRESSURE COMPRESSORS OR PUMPS A central-guiding device was proposed in U.S. Pat. No. 3,657,973, enabling the working piston of highpressure compressors or pumps, which for example deliver the medium at several thousand atmospheres, to be longitudinally guided inside the working cylinder independently of any guiding by the crosshead. According to this proposal, the face of the working cylinder is releasably connected to a lantern which is fixedly or releasably connected to the drive frame, and the working piston is releasably connected to the crosshead via a flexible connecting rod which is guided in the lantern. The guide-bore inside the lantern is co-axial with the piston-bore of the working cylinder in the direction defined by the stroke of the crosshead pin. The effect of flexibility in the connecting rod is that if the axis determined by the crosshead guide departs from the axis of the working cylinder fitted to the lantern, which can in fact occur if the crosshead tilts in its guide-track or if the crosshead moves within the play of its shoe, the piston continues to move longitudinallyin the axial direction inside the cylinder-bore, with the result that rapid wear of the piston-sealing elements is prevented and a better sealing action is thus attained. However, accurate longitudinal movement by the working piston inside the bore of the working cylinder is attainable only if the guide piston fixed to the flexible stem can be moved without any play in the guide-bore coaxial with the bore of the working cylinder, and no departures occur within the running clearances of the guide.

However, the effect in practice of the running clearances required for unhindered movement of the guide piston, particularly when it is of large diameter and short, may be that when the flexible stem connected to the crosshead bends the fixedly fitted guide piston may assume an oblique position, depending on the magnitude of the running clearances, while it is moving on its stroke inside the guide-bore. The consequence of this is that the axis of the working piston which is faceconnected to the guide piston sets itself to correspond to the oblique position of the guide piston, so that the bending moments which occur as the working piston moves longitudinally in the bore of the working cylinder set up positions of constraint inside the sealing and guiding elements of the working piston, possibly leading to rapid wear on these parts and fracture of the working piston. This can occur particularly when using working pistons which are relatively short or of fairly large diameter, or are made of a material with a high modulus of eleasticity.

The purpose of the present invention is to improve the arrangement of the guide piston with the fastening of the working piston in such a manner that even if running clearances in the guide-bore cause the guide piston to assume an oblique position during the stroke movement, the bending moments acting on the sealing and guiding elements of the working piston are reduced to the greatest possible extent.

The arrangement, according to the invention, of the guide piston with the working piston fitted in releasable connection with respect to the flexible stem is characterised in that an intermediate member with a flexible stem inside the guide piston is arranged co-axially between the guide piston and the working piston, and under pressure from the latter, in such a manner that if the guide piston assume as oblique position while the working piston is moving inside the bore of the working cylinder the bending moments acting on the working piston are reduced to the greatest possible extent.

Three examples of embodiments of the invention are depicted in the appended drawings. The illustrated embodiment for describing and illustrating the invention are intended for use with a conventional arrangement for very-high-pressure compressors or pumps with working cylinders fitted, in opposed fashion, to the drive mechanism such as shown in U.S. Pat. No. 3,657,973.

FIG. 1 shows an arrangement of the guide piston with a flexible stem fixed to the working piston, with a supporting foot having a diameter equal to or less than that of the working piston.

FIG. 2 shows an arrangement of the guide piston with a flexible stem fixed to the working piston, with a supporting foot of greater diameter than the working piston.

FIG. 3 shows an arrangement of the guide piston with an intermediate piece separate from the working piston and capable of being separately inserted, said intermediate piece having a flexible stem.

FIG. 4 shows a conventional arrangement of a high pressure compressor having a working cylinder fitted, in opposed fashion, to a drive mechanism, which arrangement provides the environment for the instant invention.

According to FIGS. 1-4, the guide piston l is arranged so as to be capable of longitudinal movement in the bore 5 of the guide cylinder 4 inside the lantern 40, said bore being co-axial with the bore of the working cylinder 41. The guide piston 1 is releasably fitted on the left-hand side by way of the fixedly fitted flexible rod 3 to the crosshead 42 located in the drive frame 43.

Since all of the basic elements shown in FIG. 4 are fully and specifically described in commonly assigned copending application Ser. No. 50,395 filed June 29, 1970 and now U.S. Pat. No. 3,657,973, which is incorporated herein by reference, the remainder of this specification will be directed mainly to the improvements shown in FIGS. 1-3.

Inside the guide piston l, and co-axially arranged therewith, is a receiving bore 6 having the end surface 7 which serves as a supporting surface.

The position of the supporting surface 7 is in the middle, or substantially in the middle, of the effective running surface of the guide piston l, which may for example be defined as shown in the drawing by the distance (a a) of two bearing metal running saddles 2 inserted at the periphery on the external surface of the piston.

According to the arrangement illustrated in FIG. 1, an intermediate member comprising a flexible stem 10 which is integral with the working piston 9, and a supporting foot 1 1 having a diameter equal to or less than that of the working piston 9, is inserted in the receiving bore 6.

The working piston 9 is caused to assume a co-axial position with respect to the guide piston l by way of the twoor multi-part centering piece 12 capable of being centrally inserted in the bore 6 and having a bored portion 13 for the purpose of centrally receiving the supporting foot 11 and an having external diameter correspond to the bore 6.

In order to fasten the working piston 9 to the guide piston 1, a screw-in piece 17 surrounding the working piston 9 is screwed into the co-axial threaded bore 8 at the projecting right-hand end until a non-positive connection is produced between the working piston 9 and the guide piston 1 by way of the sleeve 15 which can be pushed over the working piston 9, which is centrally inserted in the shoulder 14 of the centring piece 12, and which corresponds in external diameter to the bore 6. The diameter of the shoulder 14 on the centring piece 12 and of the internal bore 16 in the sleeve 15 is greater than the external diameter of the working piston 9, so that there is a gap X1. However, depending on the diameter of the working piston 9, it is possible to design the sleeve 15 in such a manner that it can be pushed in at the left-hand end of the piston over the flexible stem 10 with the supporting foot 11 before the multi-part centring piece 12 is inserted.

According to the arrangement illustrated in FIG. 2, an intermediate member comprising a flexible stem 10 which is integral with the working piston 9, and a supporting foot 18 having a diameter greater than that of the working piston 9, is inserted in the receiving bore 6. As a result of the supporting foot 18 being centred inside the bore 6, the working piston 9 is caused to assume a co-axial position with respect to the guide piston 1.

In order to fasten the working piston 9 to the guide piston l, a screw-in piece 17 surrounding the working piston 9 is screwed into the co-axial threaded bore 8 at the projecting right-hand end until a non-positive connection is produced between the working piston 9 and the guide piston 1 by way of the sleeve which can be pushed in only over the working piston 9, and which corresponds in external diameter to the bore 6.

According to the arrangement illustrated in FIG. 3, an intermediate piece 19, separate from the working piston 38, and having a flexible stem 20, is inserted in the receiving bore 6 in such a manner that upon assembly said intermediate piece is non-positively clamped between the working piston 38 and the supporting surface 7 inside the guide piston l.

The intermediate piece 19 has on the side remote from the supporting foot 21 a co-axially arranged shoulder 22 with a turned-in portion 39 having a supporting surface 23. Shoulder 24 projecting from the working piston 38 beyond the

clamping device

27, 28 is caused to rest on this surface 23. The shoulder 24 is centred in the bored portion 39, so that when the working piston 38, has been fitted it is axially connected to the guide piston 1.

In order to fasten the working piston 38 to the guide piston 1, a screw-in piece 30 surrounding the working piston 38 is screwed into the threaded bore 31 at the projecting right-hand end until a non-positive connection is produced between the working piston 38 and the guide piston 1. Internally coned clamping ring 27 presses on a corresponding externally coned multi-part clamp-ing ring 26 engaged in groove 28 having oblique supporting surfaces 29. As a result, the shoulder 21 presses against the supporting surface 7 and the shoulder 22 presses against the supporting surface 23. In order to enable the fast clamping action in the

conical clamping rings

26 and 27 to be preserved even when the stem 20 shortens under the action of the pressure set up during compression operations, guide pins 32 with pressure feet 33 are inserted inside the screw-in piece 30 and are uniformly distributed around the bore 35. These pressure feet 33 are forced by means of spring elements 34 on to the face 37 of the conical clamping ring 27.

When the working piston 38 is being fitted to the guide piston 1, which is done when there is no pressure in the machine, the inner face 36 of the screw piece 30 comes to bear against the face 37 of the conical clamping ring 27 as said screw piece is being screwed in, the spring elements 34 inserted in the screw piece 30 being tensioned by way of the

pressure pins

32, 33 while tightening is in progress.

If the intermediate member 19 shortens due to elasticity in the material when the working piston 38 is under pressure, the face 37 of the conical clamping ring 27 lifts away from the face 36 of the screw-in piece 30.

The effect of theguide pins 32 with the pressure feet 33 carrying out a following movement under the action of force from the tensioned spring elements 34, if the latter are of suitable characteristics, is that the concical clamping ring 27 and thus the multi-part conical clamping ring 26 participate in the shortening movements of the intermediate piece 19, without moving in relation to the latter.

In this connection, the bore 35 through the screw-in piece 30 must be made of such a size that there is no chance of its inside wall being touched by the working piston 38 inside the gap designated by X1 if the stem 20 bends.

The bored portion 25 at the entry to the receiving bore 6 must be made of such a size that if the flexible stem 20 bends the supporting shoulder 22 does not touch the wall of the bored portion 25 in the gap designated by X2.

With this arrangement, the working piston 38, as it moves longitudinally inside the bore of the working cylinder 41, is subjected to a reaction force depending on unhindered bending of the stem 20.

The method of fitting the working piston to the guide piston described in accordance with FIG. 3 may naturally also'be used for working pistons in which, as illustrated in FIG. 1 and FIG. 2, the flexible stem 20, with the supporting foot 21 is integral with or connected to the working piston 38.

The arrangement according to FIG. 3 with the stem 19 separate from the working piston 38 is used with advantage if the construction of the working-cylinder group requires it, of if the working piston is made of a material having a considerably higher modulus of elasticity than that of the intermediate piece 19.

As may be seen from the illustrations in the drawings and from the description, it is intended with these arrangements that the bending which is forced to take place when the guide piston 1 assumes an oblique position on the working piston 9 according to FIG. 1 and FIG. 2, or 38 according to FIG. 3, be transferred to the flexible stem 10 according to FIG. 1 and FIG. 2, or 20 according to FIG. 3, disposed inside the guide piston I.

Since in conventional high-pressure compressors or pumps the working piston 9 according to FIG. 1 and FIG. 2, or 38 according to FIG. 3, is always subjected to the effect of pressure both on the suction stroke and on the compression stroke, it follows that the flexible stem according to FIGS. 1 and 2, or according to FIG. 3, is also bound to be subjected to this pressure effect.

If the structure is relatively short, the diameter d of the stem 10 according to FIG. 1 and FIG. 2, or 20 according to FIG. 3, may be determined in accordance with the permissible compression stresses associated with the material.

Even if regard is had to buckling stress, the values of compression stress usually permissible in the case of high-duty steels enable the stem to have a relatively small diameter d.

If the guide piston 1 and thus the stem 10 according to FIG. 1 and FIG. 2, or 20 according to FIG. 3, assume an oblique position as the working piston 9 according to FIG. 1 and FIG. 2, or 38 according to FIG. 3, is being guided, the moment of resistance in the stem crosssection resulting from the small diameter d produces a bending moment in the bore of the working cylinder 41 depending on the magnitude of the given moment of resistance. This bending moment sets up reaction forces, which are only small in the case of small values, on the working piston as it is moving longitudinally. The supporting surfaces 7 on the supporting shoulder 13 according to FIG. 1, or 18 according to FIG. 2, or 7 and 23 on the supporting shoulders 21 and 22 according to FIG. 3, remain subjected to the effect of the high pressure while the working piston 9 according to FIG. 1 and FIG. 2, or 38 according to FIG. 3, is moving. These supporting surfaces are held immovable in nonpositive connection during both suction and compression operations. The bending moment which results when the guide piston 1 assumes an oblique position, and which acts on the working piston 9, is determined only by the magnitude of the moment of resistance in the flexible stem 10 according to FIG. 1 and FIG. 2, or 20 according to FIG. 3.

In the case of the arrangement according to FIG. 3, the clamping action on the conical clamping rings 27 and 28 is preserved even if the axis of the working piston 9 according to FIG. 1 and FIG. 2, or 38 according to FIG. 3, departs from the axis of the screw-in piece 30 releasably connected in the guide piston 1, since the spring-loaded pressure pins 32, 33,-which project beyond the face 37 when thrust is applied, can assume a position corresponding to the axial departure by sliding on the face 36 of the conical clamping ring 27.

In this connection, the gaps X1 and X2 prevent any contact from taking place inside the bored portion 25 or the bore when the working piston is forced to assume a new mean position under the action of the theoretical movement of the guide piston 1.

In order that the axis of the working piston 9 according to FIG. 1 and FIG. 2 or 38 according to FIG. 3, may depart as little as possible from the axis of the guide cylinder 4, the supporting surface 7 for the stem 10 according to FIG. 1 and FIG. 2, or 20 according to FIG. 3, centrally inserted in the bore 6 is so located that at point A, as illustrated in the drawings, the distance a to both running saddles 2 at the periphery of the guide piston l is equal or substantially equal. In this connection, even if the axis of the guide piston I assumes an oblique position the position of point A on the axis of the guide cylinder 4 is preserved during the stroke movement, resulting in minimum departure from the axis of the working-cylinder bore when the stem 10 according to FIG. 1 and FIG. 2, or 20 according to FIG. 3, assumes an oblique position in operation.

The arrangement illustrated and described in accordance with FIG. 3 offers the advantage, as compared to the arrangement illustrated in FIGS. 1 and 2, that should there be any fracture on the working piston, which would most probably occur only in the stem 20 as theweakest member, security is provided against the working-piston unit falling to pieces with resultant danger of an accident. If a fracture occurs, the broken stem 20 remains enclosed in the bore 6, even if the coupling consisting of the clamping rings 27 and 28 have been crushed.

I claim:

1. In a high pressure piston compressor machine having faces of the working cylinders releasably connected to a lantern member which in turn is releasably connected to a drive frame and further having at least one working piston releasably connected to a guide piston which is guided by a guide cylinder within the lantern means, said guide piston being connected to the machine crosshead via a flexible stem, the improvement comprising a bore within said guide piston, said bore being co-axial with said guide piston and having a supporting surface at the base of said bore facing outwardly therefrom towards said working piston; said working piston being co-axial with said bore and lying adjacent the open end thereof; an intermediate member having a flexible stem and at least one supporting means, said intermediate member being axially aligned within said bore between said working piston and said supporting surface; and means for connecting said stem and said working piston to said guide piston; whereby the reaction forces acting on the working piston due to an oblique position of the guide piston, are reduced so as to prevent any detrimental effect on the sealing and guiding parts of the working cylinder or piston.

2. The improvement according to claim 1 wherein the flexible stem of the intermediate member is coaxially connected to said working piston.

3. The improvement according to claim 1 wherein the flexible stem of the intermediate member is coaxially integral with said working piston.

4. The improvement according to claim 1 wherein said at least one supporting means of said intermediate member comprises a supporting foot connected to said flexible stem of said intermediate member, said supporting foot resting on said supporting surface.

5. The improvement according to claim 4 wherein said means for connecting said stem and said working piston to said guide piston comprises a tubular intermediate piece about said stem and an annular screw means surrounding said working piston, said screw means being threaded into said bore and forcing said supporting foot against said supporting surface via said tubular piece.

6. The improvement according to claim 5 wherein the diameter of the internal bore in the tubular intermediate piece and the internal diameter of the central bore in the annular screw piece define an annular gap which is required in order to allow the working piston to bend unhindered under the action of the flexible stem of the intermediate member.

7. The improvement according to claim I wherein said supporting means of said intermediate member comprises a supporting foot and a supporting shoulder, each connected to one end of said flexible stem.

8. The improvement according to claim '7 wherein said supporting foot rests on said supporting surface and said working piston is centered in a co-axially bored portion in the supporting shoulder of said intermediate member.

9. The improvement according to claim 1 wherein the supporting surface within said guide piston is located substantially at the middle of the effective guide length of said guide piston.

10. The improvement according to claim 8 wherein said means for connecting said stem and said working piston to said guide piston comprises a multipart clamping ring engaged in an annular groove in the working piston, a conical clamping ring adjacent said multipart clamping ring, and means connected to said guide piston for longitudinaily tensioning said conical clamping ring towards said multipart clamping ring.

11. The improvement according to claim 10 wherein said means for longitudinally tensioning comprises a plurality of pressure pistons uniformly distributed around the central bore and an annular screw means threaded to the end of said guide piston.

12. The improvement according to claim 1 I wherein an annular cap is formed between said annular screw means and said working piston, said annular cap being large enough to prevent said working piston or said shoulder of said intermediate member from contacting said annular screw means when said flexible stem causes bending to take place.

Claims

2. The improvement according to claim 1 wherein the flexible stem of the intermediate member is co-axially connected to said working piston.

3. The improvement according to claim 1 wherein the flexible stem of the intermediate member is co-axially integral with said working piston.

7. The improvement according to claim 1 wherein said supporting means of said intermediate member comprises a supporting foot and a supporting shoulder, each connected to one end of said flexible stem.

8. The improvement according to claim 7 wherein said supporting foot rests on said supporting surface and said working piston is centered in a co-axially bored portion in the supporting shoulder of said intermediate member.

10. The improvement according to claim 8 wherein said means for connecting said stem and said working piston to said guide piston comprises a multipart clamping ring engaged in an annular groove in the working piston, a conical clamping ring adjacent said multipart clamping ring, and means connected to said guide piston for longitudinally tensioning said conical clamping ring towards said multipart clamping ring.

12. The improvement according to claim 11 wherein an annular cap is formed between said annular screw means and said working piston, said annular cap being large enough to prevent said working piston or said shoulder of said intermediate member from contacting said annular screw means when said flexible stem causes bending to take place.