US3204863A

US3204863A - Compressor

Info

Publication number: US3204863A
Application number: US194626A
Authority: US
Inventors: Hausammann Werner
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-05-13
Filing date: 1962-05-14
Publication date: 1965-09-07
Anticipated expiration: 1982-09-07
Also published as: DE1428134A1; CH392760A

Description

Sept. 7, 1965 w. HAUSAMMANN 3,204,863

COMPRESSOR Filed May 14, 1962 3 Sheets-Sheet 1 FIG. 2

INVENTOR 4/6 finer flag .ro 111171.21;

ATTORNEY Sept. 7, 1965 w. HAUSAMMANN 3,204,863

COMPRESSOR Filed May 14, 1962 3 Sheets-Sheet 2 I II" "I I" "I'IIIIIIIIIIII/IIIIIIIIIIIIIIIIIII.,

INVENTOR S t, 7, 1965 w. HAUSAMMANN 3,204,863

COMPRESSOR Filed May 14, 1962 3 Sheets-Sheet 3 FIG. 6

IN VEN TQR United States Patent 3,204,863 COMPRESSOR Werner Hausammann, Dahliastrasse 16, Zurich, Switzerland Filed May 14, 1962, Ser. No. 194,626 Claims priority, application Switzerland, May 1'3, 1961, 5,601/ 61 4 Claims. (Cl. 230-114) The present invention relates to fluid flow producing machines in general, and more particularly to improvements in a method of and in means for varying the capacity or throughput without changing the characteristic pressure-volume curve of a fluid flow producing machine. Still more particularly, the invention relates to improvements which may be embodied with great advantage in compressors of the type known as turboblowers or turbocompressors wherein the fluid flows at supersonic speeds.

Many types of compressors, especially multi-stage axial flow compressors, exhibit a characteristic pressure-volume curve which allows only for slight variations in the capacity or throughput of the machines. Thus, if the capacity is reduced to a very small extent (for example, by throttling), i.e. if such compressors operate at slightly below their rated capacity, they become unstable in their operation by reaching the pumping point, also known as surge point. Therefore, there exists an urgent need for compressors whose capacity may be varied within a wide range well above and/ or below the rated capacity. The capacity of a compressor, e.g. an axial flow compressor, is determined by the effective cross-sectional area of the inlet or by the height (i.e. the fluid-contacting areas) of the impeller blades. If the fluid-contacting areas of the blades are reduced, the capacity will drop. Consequently, and if the velocity vector diagrams of the impeller can remain unchanged, particularly at the inlet of the compressor, the latter will exhibit a substantially horizontal characteristic pressure-volume curve and a substantially flat efficiency curve.

An important object of the present invention is to provide a compressor, particularly a supersonic axial flow compressor, whose capacity may be varied well above and/ or below its rated capacity without in any way or without substantially affecting the characteristic curve of the compressor.

Another object of the invention is to provide a compressor of the just outlined characteristics whose capacity may be varied substantially between 25 and 120 percent of its rated capacity without reaching the surge point, and whose efliciency and pressure-volume characteristics remain satisfactory even if its capacity is reduced well below the rated capacity.

A further object of the invention is to provide a compressor of the above outlined type which is provided with a very simple, easy-to-manipulate and highly reliable regulating arrangement by means of which the actual capacity may be varied at will above or below the rated capacity.

Still another object of the invention is to provide a method of varying the capacity without or by only slightly changing the characteristic curve of a compressor.

An additional object of the invention is to provide a method of varying the capacity of a compressor which can be resorted to in connection with singleor multistage compressors and which can be resorted to in all or nearly all types of modern fluid flow producing machines.

With the above objects in view, the invention resides in the provision of a fluid flow producing machine which comprises a hollow first element having fluid admitting inlet means, a second element extending into and defining with the first element at least one pressure chamber and 3 ,204,863 Patented Sept. 7, 1965 at least one suction chamber which latter communicates with the inlet means, means for rotating one of these elements with respect to the other element, blade means provided on the one element intermediate the two chambers and defining with the two elements passage means through which fluid admitted into the suction chamber is caused to flow into the pressure chamber when the one element rotates with respect to the other element, and regulating means provided in the interior of the first element for varying the effective cross-sectional area of the passage means and for proportionally changing the fluid-contacting areas (height) of the blade means so as to change the capacity without substantially changing the performance curve of the machine.

In accordance With my method, the effective crosssectional areas of the passage means between the lower pressure side and the higher-pressure side of the rotary element are changed proportionally and simultaneously with changes in the fluid-contacting surface areas of the blades, and such changes may be brought about while the compressor is in operation, i.e. While the rotary element is driven.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of certain embodiments with reference to the accompanying drawings, in which:

FIG. 1 is an axial section through a turbo-compressor which embodies one form of my invention and whose hydraulically actuated regulating means is shown in a position it assumes when the volume of fluid flowing from the lower-pressure side to the higher-pressure side of the impeller is increased;

FIG. 2 is a similar axial section through .a modified turbocompressor, showing a pneumatically actuated regulating means in a position it assumes when the volume of fluid flowing from the lower-pressure side to the higherpressure side of the impeller is reduced;

FIG. 3 is a fragmentary axial section through a turbocompressor wherein the regulating means is adjustable by mechanical actuating means;

FIG. 4 is a fragmentary axial section through a further turbocompressor wherein the regulating means is mounted in and is centered by hearing elements provided along the internal surface of the casing;

FIG. 5 is a similar fragmentary axial section through a turbocompressor in which the regulating means is axially reciprocably supported and centered by the impeller blades; and

FIG. 6 is a perspective view of a turbocompressor which comprises an impeller having helical blades and wherein the regulating means performs a composite movement when it is caused to change its axial position in the casing.

Referring now in greater detail to the illustrated embodiments, and first to FIG. 1, there is shown a fluid flow producing machine in the form of a turbocompressor which comprises a hollow casing A having a fluid admitting inlet 1, the latter secured to a vane ring 2 forming part of the casing and provided with radially extending internal guide vanes 3. The tips of these vanes support a substantially hemispherical profiled body 5 which is located centrally between the vanes so that its axis coincides with the axis 4 of the casing A. The profiled body 5 constitutes the last element of the fluid guiding portion of the compressor.

At the downstream side of the profiled body 5, there is provided an impeller B which is driven by a co-axial shaft 6, the latter coaxial with the ring 2 and secured at its forward end to a substantially frustoconical hub 'I forming part of the impeller B and provided with an annularly arranged group of external impeller blades, 8. The'rnain body portion 9 of the casing A surrounds the impeller B and is connected to an outwardly extending flange of the ring 2 so as to define with the latter an annular compartment 10 which is open to the lower-pressure or control chamber of the compressor prior to accommodation in chamber luf of the annular piston 11, as more fully described hereinafter. The

parts

2 and 9 together form a double-acting cylinder and the compartment 10 actually constitutes a cylinder chamber and accommodates an axially reciprocable actuating or adjusting element in the form of an annular piston 11. The adjusting element 11 extends through a narrow gap defined by an internal annular collar 9a of the main body portion 9, and its forward edge portion 12 projects or may be caused to project into the suction chamber 15. The collar 9a is provided with an internal annular groove for a sealing ring 13 which cooperates with the adjusting element 11 to seal the compartment 10 from the control chamber 15. The main body portion 9 of the casing A is provided with

spaced bores

14, 14a which conduct a hydraulic pressure fluid (e.g. oil) to the opposite sides of an annular flange 11a forming part of the adjusting element 11' so that the latter is shift-ed to the right when pressure fluid is admitted through the bore 14 and that the flange 11a causes the adjusting element 11 to move in a direction to the left when the pressure fluid flows through the bore 14a to fill the right-hand portion of the compartment 10. The source of pressure fluid may assume the form of an oil tank 141; which is connected with a four-way valve 14c by a pressure conduit 14d. The conduit 14d contains a pump 14c and a pressure relief valve 14 which is disposed between the pump 142 and valve 140 and which returns pressure fluid to the tank 14b through a conduit 14g when the pressure prevailing in the compartment 10' reaches a predetermined maximum value. 7 The

bores

14, 14a communicate with

conduits

14h, 14i leading tothe valve 140, and the latter is connected with the tank 14b by a further return conduit 14 which, in the position of FIG. 1, communicates with the conduit 14i so that pressure fluid admitted into the lefthand portion of the compartment 10 (conduit 14-h) may expel the fluid filling the right-hand portion of the compartment 10. The adjusting element 11 and the parts 14-141 together constitute a hydraulic actuating means for a rotary regulating means 17 which is accommodated in the cylinder 9 of the casing A and which is: rotated by and is axially movable along the blades 8 so as to vary the effective cross-sectional area of a series of elongated passages 8a defined by the cylinder 9, by the hub 7 and by the blades 8 and extending from the control chamber 15 to a higher-pressure chamber 16.

The chamber 16 is surrounded by a diverging conical portion 9b of the casing A, and this casing further comprises a cover 18 which defines a volute chamber 22. The ducts 23 connecting the pressure chamber 16 with the volute chamber 22 accommodate stationary guide vanes 21. The cover 18 receives a bearing sleeve 19 for the impeller shaft 6.

The regulating means 17 assumes the form of an annular member whose cylindrical periphery is slightly spaced from the internal surface of the main body portion 9 to define therewith an annular channel 20 through which some fluid may leak from the pressure chamber 16 to the control chamber 15. The conically diverging internal surface 17a of the annular member 17 is formed with radially outwardly extending slots 17b each of which slidably accommodates a portion of a blade 8 so that the annular member 17 is axially movable between the

chambers

15, 16 and may thereby adjust the effective crosssectional areas of the passages 8a by simultaneously changing the exposed or fluid-contacting surface areas (height) of the blades 8. In the position of FIG. 1, the annular member 17 is located mainly in the suction chamber 15'so that the cross-sectional areas of the passages Sa reach a maximum magnitude and that the fluid contacting surface areas of the blades 8 also attain .a maximum magnitude, i.e. the blades are nearly fully exposed and compel the fluid admitted through the inlet 1 to flow into the control chamber 15', through the passages 801, into the chamber 16; through the ducts 23 and into the volute chambert22. The hydraulic actuating means 11, 14-141 is shown in a position its parts assume just before the adjusting element 11 is caused to move in a direction to .the right, as viewed in FIG. 1, in order to reduce the capacity without, however, appreciably changing the characteristic curve of the compressor. As soon as the pressure of fluid admitted to the left-hand side of the flange 11a causes the adjusting element 11 to move in a direction to the right, the edge portion 12 contacts the annular member 17 and prevents flow of compressed fluid from the control chamber 15 into the passages 8a so that the pressure prevailing in the chamber 15 increases. This higher pressure acts against the left-hand end face of the annular member 17 to shift this annular member in a direction to the right, i.e. away from actual contact with the edge portion 12. Consequently, the combined cross-sectional area of the passagesSa is reduced by simultaneousreduction in the fluid-contacting areas of the blades48 since the slots 1712 now accommodate larger portions of these blades. The reduction in the fluid-contacting-areas of the blades is proportional with the reduction in the cross-sectional areas of the passages So so that the characteristic pressure-volume curve of the compressor remains unchanged. It can be said, once movement of the edge portion 12 results in shifting of the annular member 17, the latter automatically finds a new axial position of equilibrium in which the reduction in the fluid-contacting areas of the blades 8 is proportional with the reduction in the crosssectional areas of the passages 8a. The forces acting on the annular member 17 are now in equilibrium and the annular member thereupon retains its axial position unless the adjusting element 11 is caused to move to the left or to the right, as viewed in FIG. 1. Since the forces acting in the passages 8a vary at a constant rate in response .to reduction or increase in the cross-sectional areas of these passages, the volume of fluid flowing through the passages 8a is proportional with pressures prevailing in that section of the compartment 10 which is momentarily connected with the pressure side of the pump 14a.

The situation is reversed if the adjusting element is caused to move in a direction to the left so as to move its edge portion 12 away from the annular member 17. The cross-sectional area of the clearance between the element 11 and the annular member 17 then increases so that pressure in the control chamber 15 drops and that the pressure prevailing in the chamber 16 causes the annular member to move to the left until it finds a new axial position of equilibrium. Owing to such leftward movement of the annular member 17, the combined cross-sectional area of the passages 8a increases proportionally with an increase in the fluid-contacting surface areas of the blades 8 in the passages 17a in order to make sure that the characteristic curve of the compressor remains unchanged. In other words, the characteristic curve of the compressor remains unchanged even though the capacity of the compressor is changed above or below its rated capacity While the rpm. of the impeller B may remain constant. The characteristic curve is substantially horizontal and the efli'ciency curve resembles a straight line.

The compressor of FIG. 2 is identical with the compressor of FIG. 1, excepting that it comprises a pneumatic actuating means because the oil tank 14b is replaced by a port 14k which supplies pressure fluid from the volute chamber 22 through the conduit 14d and to the valve 140. The annular member 17 is shown in a position in which it greatly reduces the cross-sectional areas of the passages 8a and in which it nearly completely conceals the impeller blades 8 in the slots 17b.

In the compressor of FIG. 3, the annular member 17 is shiftable by mechanical actuating means including a bracket 25 which is secured to the flange 111a of a slightly modified adjusting element 111, a pivot pin 26 which connects this bracket with a push rod 27 passing with play through registering bores provided in the inlet 1 and ring 2, a two-armed lever 28 which is rockable about a pivot pin 29 secured to a bracket 30 provided on the inlet 1, and a further pivot pin 31 which a-rticulately connects the push rod 27 with one arm of the lever 28. The other arm of the lever 28 is provided with a handgrip means in the form of a knob 32 which is grasped when the operator desires to operate the

link train

27, 23 and to shift the adjusting element 111 toward or away from the annular member 17. In the position of FIG. 3, the annular member 17 is moved close to its extreme righthand position so that the combined cross-sectional area of the passages 81:: is reduced proportionally with a reduction in the combined area of fluid-contacting surfaces of the blades 8. Otherwise, the construction of the compressor shown in FIG. 3 is identical with the construction of both previously described compressors. FIG. 4 illustrates a further modification of my invention according to which the main body portion 9 of the casing is provided with inwardly extending projections 33 which constitute bearing elements for axially movably guiding and for centering the annular member 17.

FIG. 5 illustrates an analogous construction wherein the impeller blades 8 are provided with radially extending projections 34 to center and to guide the annular member 17 in its axial movements within the main body portion 9. The width of the channel is exaggerated for the sake of clarity.

It is further possible to provide bearing elements on the hub 7 so that the latter serves as a means for centering the annular member 17. This modification is so obvious that it can be construed without necessitating a separate illustration.

FIG. 6 shows a further compressor wherein the hub '7 is provided with helically arranged impeller blades 108. Therefore, the annular member 117 is formed with helical slots 11712 which guide the annular member in such a way that the latter performs a composite movement (axially and circumferentially) when it is shifted by the adjusting element 11 or when it is permitted to move in response to leftward displacement of the element 11. Otherwise, the construction of this compressor is the same as the construction of the compressor described in connection With FIG. 1, i.e. it is assumed that the adjusting element 11 forms part of a hydraulic actuating means. The blades 103 preferably assume a form as described in my copending application Serial No. 716,504 to which reference may be had if necessary.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An axial flow compressor comprising, in combination, a hollow casing having fluid admitting inlet means; an impeller comprising a hub extending into and defining with said casing an annular control chamber and a higher-pressure annular chamber, said control chamber in communication with said inlet means; means for rotating said impeller; rotary blade means provided on said hub intermediate said chambers and defining with said casing and with said hub passage means through which fluid admitted into said inlet means is caused to flow into said higher-pressure chamber when said impeller is rotated; regulating means comprising an annular member axially movably received in said casing and surrounding at least a portion of said hub, said annular member having internal slot means for said blades and adapted to change the cross-sectional areas of said passages in response to axial movements thereof and to proportionally change the areas of the fluid-contacting surfaces of said blades by receiving larger or smaller portions of said blades in the respective slot means so that the capacity of the compressor changes but the characteristic curve of the compressor remains substantially unchanged, said control chamber and said higher-pressure chamber communicating with one another through a path other than the path provided by said passages so that pressure fluid can flow from said higher-pressure chamber to said control chamber; and hydraulically actuated control means for controlling the axial position of said annular member in said casing, said actuating means comprising a double-acting cylinder in said casing at the upstream side of said regulating means, a piston reciprocably received in said cylinder and having a portion movable with respect to said annular member to control the communication of the control chamber with said inlet means, a source of hydraulic pressure fluid, and an operative connection between said source and said cylinder for selectively admitting hydraulic fluid from said source and for thereby moving said piston toward or away from said annular member.

2. A compressor comprising, in combination, a hollow casing having fluid admitting inlet means at one end thereof and cover means defining a volute chamber at the other end thereof; an impeller comprising a hub located in and defining with said casing a control chamber in communication with said inlet means and a higher-pressure chamber in communication with said volute chamber; means comprising a shaft extending through said cover means and drivingly secured to said hub for rotating said impeller; rotary blade means provided on and disposed about said hub, said blade means located intermediate said inlet means and said higher-pressure cham her and defining with said casing and with said hub a plurality of passages through which fluid admitted through said inlet means is caused to flow into said higher-pressure chamber when said impeller is rotated; regulating means comprising an annular member disposed in said casing and surrounding said hub, said annular member having internal slot means slidably receiving said blade means so that the annular member is movable in the axial direction of said impeller to thereby vary the combined cross-sectional areas of said passages and to proportionally change the areas of fluid-contacting surfaces of said blades so that the capacity of the compressor is changed without appreciable changing the characteristic curve of the compressor, said annular member defining with said casing an annular channel through which the fluid may leak from said higher-pressure chamber to said control chamber; and actuating means provided at the upstream side of said impeller for axially moving said annular member in said casing, said actuating means comprising an adjusting element axially movably received in said casing and having a motion-transmitting portion adapted to move with respect to said annular member, said adjusting element and said annular member defining between themselves a clearance through which fluid may flow from said channel into said passages when the adjusting element is spaced from said annular member, said channel being sealed from said passages at the upstream side of said passages when the adjusting element approaches said annular member so that the pressure of fluid in said control chamber increases and the fluid shifts the annular member in a direction away from said adjusting element.

3. A compressor comprising, in combination, a hollow casing havingfluid admitting inlet means at one end thereof and cover means defining a volute chamber at the other end thereof; an impeller comprising a hub located in and defining with said casing a control chamber in communication with said inlet means and a higherpressure chamber in communication with said volute chamber, said hub having a conical periphery diverging in a direction from said inlet means to said higher-pres sure chamber; means comprising a shaft extending through said cover means and drivingly secured to said hub for rotating said impeller; rotary blade means provided on and disposed about said hub, said blade means located intermediate said inlet-means and said higher-pressure chamber and defining with said casing and with said hub a plurality of passages through which fluid admitted through said inlet means is caused to flow into said higher-pressure chamber when said impeller is rotated; regulating means comprising an annular member disposed in said casing and surrounding. said hub, said annular member having a conical internal surface diverging in a direction from said inlet means to said higher-pressure chamber and slot means provided in said internal surface for slidably receiving said blade means so that the annular member is movable in the axial direction of said impeller to thereby vary the combined cross-sectional areas of said passages and to proportionally change the areas of fluidcontracting surfaces of said blades so that the capacity of the compressor is changed without appreciably changing the characteristic curve of the compressor, said annular member defining with said casing an annular channel through which the fluid may leak from said higherpressure chamber to said lower-pressure chamber; and actuating means provided at the upstream side of said impeller for axially moving said annular member in said casing, said actuating means comprising an adjusting element axially movabl'y received in said casing and having a motion-transmitting portion adapted to move with respect to said annular member, said adjusting element and said annular member defining between themselves a clearance through which fluid may flow from said channel into said passages when the adjusting element is spaced from said annular member, said channel being sealed from said passages at the upstream side of said passages when the adjusting element approaches said annular member so that the pressure of fluid in said control chamber increases and the fluid shifts the annular member in a direction away from said adjusting element.

4. An axial flow compressor comprising a hollow casing having fluid admitting inlet means; an impeller comprising a hub extending into and defining with said casing an annular control chamber which communicates with said inlet means and a higher-pressure annular chamber; means for rotating said impeller; blade means provided on said hub intermediate said chambers and defining with said casing and with said hub a plurality of passages through which fluid admitted into said inlet means is caused to flow into said higher-pressure chamber in response to rotation of said impeller; regulating means comprising an annular member axially movably received in said casing and spaced therefrom to surround at least a portion of said hub and having internal slots for said blades so as to change the cross-sectional areas of said passages in response to axial movements thereof and to proportion-ally change the areas of the fluid-contacting surfaces of said blades by receiving larger or smaller portions of said blades in the respective slots whereby the capacity of the compressor changes but the characteristic curve of the compressor remains substantially unchanged; and mechanical actuating means for axially adjusting said annular member in said casing, said actuating means comprising a cylinder in said casing at the upstream side of said regulating means, a piston reciprocably received in said cylinder and having a portion movable with respect to said annular member, and a link train connected with and arranged to move said piston in said cylinder toward or away from said annular member.

References Cited by the Examiner UNITED STATES PATENTS 1,742,215 1/30 Pigott 103-120 2,358,744 9/44 Stepanoff 103-97 2,927,536 3/60 Rhodes 103-97 2,936,948 5/60 Eck 230-114 2,955,541 10/60 Moore 103-120 2,957,424 10/60 Brundage 103-97 2,968,146 1/61 Howell 230-114 2,986,218 5/61 Wagner 253-59 3,045,894 7/62 Ross 230-114 LAURENCE V. EFNER, Primary Examiner.

JOSEPH H. BRANSON, Examiner.

I f g

Claims

1. AN AXIAL FLOW COMPRESSOR COMPRISING, IN COMBINATION, A HOLLOW CASING HAVING FLUID ADMITTING INLET MEANS; AN IMPELLER COMPRISING A HUB EXTENDING INTO AND DEFINING WITH SAID CASING AN ANNULAR CONTROL CHAMBER AND A HIGHEX-PRESSURE ANNULAR CHAMBER, SAID CONTROL CHAMBER IN COMMUNICATION WITH SAID INLET MEANS; MEANS FOR ROTATING SAID IMPELLER; ROTARY BLADE MEANS PROVIDED ON SAID HUB INTERMEDIATE SAID CHAMBERS AND DEFINING WITH SAID CASING AND WITH SAID HUB PASSAGE MEANS THROUGH WHICH FLUID ADMITTED INTO SAID INLET MEANS IS CAUSED TO FLOW INTO SAID HIGHER-PRESSURE CHAMBER WHEN SAID IMPELLER IS ROTATED; REGULATING MEANS COMPRISING AN ANNULAR MEMBER AXIALLY MOVABLY RECEIVED IN SAID CASING AND SURROUNDING AT LEAST A PORTION OF SAID HUB, SAID ANNULAR MEMBER HAVING INTERNAL SLOT MEANS FOR SAID BLADES AND ADAPTED TO CHANGE THE CROSS-SECTIONAL AREAS OF SAID PASSAGES IN RESPONSE TO AXIAL MOVEMENTS THEREOF AND TO PROPORTIONALLY CHANGE THE AREAS OF THE FLUID-CONTACTING SURFACES OF SAID BLADES BY RECEIVING LARGER OR SMALLER PORTIONS OF SAID BLADES IN THE RESPECTIVE SLOT MEANS SO THAT THE CAPACITY OF THE COMPRESSOR CHANGES BY THE CHARACTERISTIC CURVE OF THE COMPRESSOR REMAINS SUBSTANTIALLY UNCHANGED, SAID CONTROL CHAMBER AND SAID HIGH-PRESSURE CHAMBER COMMUNICATING WITH ONE ANOTHER THROUGH A PATH OTHER THAN THE PATH PROVIDED BY SAID PASSAGES SO THAT PRESSURE FLUID CAN FLOW FROM SAID HIGH-PRESSURE CHAMBER TO SAID CONTROL CHAMBER; AND HYDRAULICALLY ACTUATED CONTROL MEANS FOR CONTROLLING THE AXIAL POSITION OF SAID ANNULAR MEMBER IN SAID CASING, SAID ACTUATING MEANS COMPRISING A DOUBLE-ACTING CYLINDER IN SAID CASING AT THE UPSTREAM SIDE OF SAID REGULATING MEANS, A PISTON RECIPROCABLY RECEIVED IN SAID CYLINDER AND HAVING A PORTION REMOVABLE WITH RESPECT TO SAID ANNULAR MEMBER TO CONTROL THE COMMUNICATION OF THE CONTROL CHAMBER WITH SAID INLET MEANS, A SOURCE OF HYDRAULIC PRESSURE FLUID, AND AN OPERATIVE CONNECTION BETWEEN SAID SOURCE AND SAID CYLINDER FOR SELECTIVELY ADMITTING HYDRAULIC FLUID FROM SAID SOURCE AND FOR THEREBY MOVING SAID PISTON TOWARD OR AWAY FROM SAID ANNULAR MEMBER.