Vane structure for compressor

Abstract

A vane structure for a compressor comprises: a Z-plate located in a cylinder assembly for dividing an inner space of the cylinder assembly into a plurality of compression spaces and notated by a driving unit to suck, compress, and discharge fluid; and vanes undergoing reciprocating movements by being contacted to both surfaces of the Z-plate for dividing the respective compression space into a suction area and a compression area, wherein the vane includes a vane roller which is rolling contacted to the Z-plate to reduce a friction resistance between the Z-plate and the vane, and thereby an abrasion can be minimized, a noise generation can be reduced, life spans of components can be increased, and a reliability of the compressor can be improved.

Description

TECHNICAL FIELD

[0001] The present invention relates a vane structure for a compressor in which a vane is in contact with a Z-plate, a rotation member, so that a fluid can be compressed in a compression chamber and discharged therefrom

BACKGROUND ART

[0002] Generally, compressors convert a mechanical energy into a compression energy of an compressible fluid, of which a freezing compressor is classified into a reciprocating compressor, a scroll type compress, a centrifugal type compressor and rotary type compressor depending on a compression method.

[0003] The present applicant has developed a compressor with a novel concept, which can be classified into the rotary compressor, and filed an application for the invention to the Korean Industrial Patent Office (Application No. 10-1999-0042381, Application date: Oct. 1, 1999), which has been laid open May 7, 2001 with a-publication number 2001-0035687.

[0004] The former application invention of the same applicant will now be described with reference to FIG. 1.

[0005] FIG. 1 is a vertical sectional view showing a compressor of the former application invention of the present invention.

[0006] As shown in FIG. 1, a compressor of the former application invention of the present invention includes: a electric mechanism unit 4 consisting of a stator and a rotor 3 inside a casing 1 and generating a rotational force; and a compression mechanism unit 10 for compressing a fluid by a rotational force generated from the rotor 3 of the electric mechanism unit 4 and discharging it.

[0007] FIG. 2 is a partial cut-out perspective view showing the compression mechanism unit 10.

[0008] With reference to FIGS. 1 and 2, the compression mechanism unit. 10 includes: a cylinder 11 fixed at a lower portion of the casing 1; a first bearing plate 13 and a second bearing plate 14 fixed at an upper surface and a lower surface of the cylinder 11 and forming a compression space (V) together with the cylinder 11; a rotational shaft 12 for transmitting a rotational driving force generated from the rotor 3 of the electric mechanism unit 4 to the compression mechanism unit; a Z-plate 15 coupled at the rotational shaft 12 and rotated, and dividing the compression space (V) of the cylinder 11 into a first space (V1) and a second space (V2); and a first vane 17 and a second vane 18 each being in contact with the upper surface and lower surface of the Z-plate and dividing the spaces V1 and V2 into suction areas (V1s and V2s) and compression area (V1p and V2p) when the Z-plate is rotated.

[0009] The cylinder 11, the first bearing plate 13 and the second bearing plate 14 are cylinder assembly forming the compression space (V).

[0010] In FIG. 1, reference number 5 denotes a suction pipe through which a fluid is sucked into the casing 1, and 6 denotes a discharge pipe through which a fluid is discharged.

[0011] Reference numerals 11a and 11b denote suction passages through which a fluid is sucked into the compression space (V) of the cylinder 11, 13a and 14a denote discharge passages for discharging a compressed fluid, and 13b and 14b denote discharge valves.

[0012] Reference numerals 19 and 20 denote discharge mufflers for reducing a discharge noise, and 19a and 20a denote discharge holes formed at the discharge mufflers 19 and 20, through which a compressed fluid is discharged.

[0013] Primary construction elements of the compressor will now be described in detail.

[0014] The Z-plate 15 is formed as disk type when projected on plane so that its outer circumference face can slidably contact an inner circumferential face of the cylinder 11, and its side is formed with a cam surface of a sine wave curve which has the same thickness from the inner circumferential face to the outer cicumferential face in its development, so that its upper dead point (R1) is in contact with the lower surface of the first bearing plate 13 and rotated, and a lower dead point (R2) is closely adhered to the upper surface of the second bearing plate 14 and rotated.

[0015] As shown in FIG. 3, the first vane 17 and the second vane 18 are formed in square plate shape with a certain thickness, penetrating each bearing plate 13 and 14, so that when the rotational shaft 12 is rotated the first vane 17 and the second vane 18 linearly and reciprocally moved in the axial direction along the cam surface of the Z-plate 17 while being in contact with the upper surface and lower surface of the Z-plate 15, respectively.

[0016] The first vane 17 and the second vane 18 receives an elastic force from springs 21 and 22 supplied by the bearing plates 13 and 14 at their rear portion 17a (refer to FIG. 1). An outer side 17b of each vane 17 and 18 is in contact with the inner circumferential face of the cylinder 11, and an inner side of each vane 17 and 18 is in contact with the outer circumferential face of the rotational shaft 12. A front end portion 17d of each vane 17 and 18 slidably contacts the upper surface and the lower surface of the Z-plate 15 (reference to FIG. 2).

[0017] The operation process of the compressor of the former application invention constructed as described above will now be explained.

[0018] When the rotational shaft 12 is rotated by a driving force of the electric mechanism unit 4, the Z-plate 15 coupled at the rotational shaft 12 is simultaneously rotated in the cylinder 11, thereby sucking, compressing and discharging a fluid.

[0019] Namely, with reference to FIG. 2, the first space V1 positioned at an upper portion of the Z-plate 15 is divided into a suction area V1s and a compression area V1p by taking the upper dead point (R1) and the first vane 17 as a boundary, and the second space V2 positioned at the lower portion of the Z-plate 15 is divided into a suction area (V2s) and a compression area (V2p) by taking the lower dead point (R2) and the second vane 18 as a boundary.

[0020] In this state, as the Z-plate 15 is rotated, the upper dead point (R1) and the lower dead point (R2) of the Z-plate 15 are moved to vary a volume of the suction area and the compression area of each space.

[0021] At this time, the first vane 17 and the second vane 18 are reciprocally moved in the mutually opposite direction up to as high as the cam face of the Z-plate.

[0022] Accordingly, a fresh fluid is simultaneously sucked into each suction area (V1s, V2s) through each suction passage 11a and 11b of the first space V1 and the second space V2 and gradually compressed, and then, when the upper dead point R1 or the lower dead point R2 of the Z-plate reaches a discharge initiation point, the fluid is simultaneously discharged outwardly of the compression space (V) through the discharge passages 13a and 14a of each space V1 and V2.

[0023] However, in the compressor of the former application invention, as the vanes which are linearly and reciprocally moved are in contact with the upper surface and the lower surface of the Z-plate 15, a sliding friction takes place at the contact side between the vanes 17 and 18 and the Z-plate 15.

[0024] Accordingly, a driving force loss is increased due to the friction resistance between the vanes 17 and 18 and the Z-plate 15, and a friction noise is generated.

[0025] In addition, as the friction face between the vanes 17 and 18 and the Z-plate 15 is abraded t shorten a life span of the parts, and especially, as the fluid at the side of the compression area is leaked toward the suction area, so that a compression efficiency is degraded.

[0026] Technical Gist of the Pesent Invention

[0027] Therefore, an object of the present invention is to provide a vane structure of a compressor that is capable of heightening an efficiency and a reliability of a compressor by reducing a friction loss and abrasion between a vane and a Z-plate.

DETAILED DESCRIPTION OF THE INVENTION

[0028] In order to achieve the above objects, there is provided a vane structure for a compressor including a cylinder assembly having a suction passage and a discharge passage, a Z-plate dividing an inner space of the cylinder assembly into a plurality of compression spaces, and sucking, compressing and discharging a fluid while being rotated by a driving unit, and vanes being in contact with both sides of the Z-plate to make a reciprocal movement, and dividing each compression space into a suction area and a compression area, wherein the vane has a vane roller being in rolling-contact with the Z-plate.

[0029] The vane includes a vane plate reciprocally moved along both sides of the Z-plate and a vane roller provided at the vane plate and being in a rolling-contact with the Z-plate.

[0030] The vane plate includes a roller receiving hole into which the vane roller is inserted and mounted.

[0031] In one embodiment of the present invention, the vane roller is formed having a bar structure with the same diameter on the whole, and the roller receiving hole is formed in a hole structure having the same inner diameter.

[0032] An opened portion of the roller receiving hole so that the vane roller comes in contact with the Z-plate therethrough is smaller than a diameter of the vane roller to prevent the vane roller from releasing.

[0033] At least one of both sides of the roller receiving hole has an opened structure.

[0034] In another embodiment of the present invention, a roller support extended from the vane plate is formed at both sides of the roller receiving hole, and the vane roller can be rotatably supported by the roller support.

[0035] The vane roller is installed at the roller support through a pin member.

[0036] In still another embodiment of the present invention, the vane roller is formed in a bar structure with a tapering shape, and the roller receiving hole is formed in a tapering hole structure.

[0037] The vane roller is positioned such that a side with a relatively smaller diameter is directed inward of the cylinder assembly and a side with a relatively greater diameter is directed outward of the cylinder assembly.

[0038] The vane structure for a compressor of the present invention has effects that by mounting the vane roller being in rotatably contact with the Z-plate in the vane, a friction resistance between the Z-plate and the vane can be reduced when a compressor is operated, according to which a friction between the Z-plate and the vane can be minimized, a noise is restrained from generating, a durability of parts can be lengthened, and a reliability of the compressor can be heightened.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a vertical-sectional view showing a compressor of a former application invention of the present invention;

[0040] FIG. 2 is a partial cut-out perspective view showing a compression mechanism unit of a compressor of the former application invention of the present invention;

[0041] FIG. 3 is a perspective view of a vane of the compressor of the former application invention of the present invention;

[0042] FIG. 4 is a vertical-sectional view showing a compression mechanism unit of a compressor in accordance with the present invention;

[0043] FIGS. 5 and 6 are a perspective view and an exploded perspective view showing a vane structure in accordance with a first embodiment of the present invention;

[0044] FIGS. 7 and 8 are a perspective view and an exploded perspective view showing a vane structure in accordance with a second embodiment of the present invention;

[0045] FIG. 9 is an exploded perspective view showing a vane structure and a vane installation structure in accordance with a third embodiment of the present invention; and

[0046] FIG. 10 and FIG. 11 are explanatory side views showing a vane operation state of the third embodiment of the present invention.

MODE FOR CARRYING OUT THE PREFERRED EMBODIMENTS

[0047] The present invention will now be described with reference to accompanying drawings.

[0048] FIG. 4 is a vertical-sectional view showing a compression mechanism unit of a compressor in accordance with the present invention, and FIGS. 5 and 6 are a perspective view and an exploded perspective view showing a vane structure in accordance with a first embodiment of the present invention.

[0049] The same reference numerals are given to the same and similar parts as in the former application invention as described above in the following descriptions.

[0050] A compression mechanism unit 10 of a compressor where vanes are installed includes: a rotational shaft 12 coupled at a rotor of an electric mechanism unit provided inside a casing 1; a Z-plate 15 dividing the inner space of the cylinder assembly including the cylinder 11 coupled with the rotational shaft 12 into a first space V1 and a second space V2; and a first vane 50 and a second vane 55 respectively inserted into the first and second bearing plates 13 and 14 and linearly and reciprocally moved along the cam face of the Z-plate 15.

[0051] Especially, each vane 50 and 55 include vane rollers 52 and 57 at their front end portion so as to be in rolling-contact with the Z-plate 15.

[0052] In FIG. 4, reference number 5 is suction pipes through which a fluid is sucked into the casing 1, 19 and 20 denote discharge mufflers for reducing a discharge noise, and 19a and 20a denote discharge holes formed at the discharge mufflers 19 and 20, through which a compressed fluid is discharged.

[0053] Major constructional elements of the compression mechanism unit 10 will now be described.

[0054] The first and second bearing plats 13 and 14 are respectively mounted at an upper side and a lower side of the cylinder 11, which form a compression space of the cylinder assembly together with the cylinder 11.

[0055] The suction passages 11a and 11b are respectively formed at the cylinder 11, communicating with the first space V1 and the second space V2, in order to suck a fluid from outside. Discharge passages 13a and 14a are formed at each bearing plate 13 and 14, which respectively include discharge valves 13b and 14b.

[0056] The Z-plate 15 is formed as a disk type when viewed from plane projection so that its outer circumferential surface can slidably contact the inner circumferential surface of the cylinder 11, and the circumferential side is formed as a cam face of a sine wave curve having the same thickness from the inner circumferential face to the outer circumference face when the side is opened.

[0057] In the first embodiment of the present invention, as shown in FIGS. 5 and 6, the first vane 50 and the second vane 55 include a vane plate 51 formed in a square plate structure with a certain thickness and area; and a vane roller 52 rotatably mounted at a front end portion of the vane plate 51 and being in rolling-contact with the upper surface and the lower surface of the Z-plate 15.

[0058] The vane plate 51 is supplied by springs 21 and 22 at its rear portion 51a, and both sides 51b and 51c are respectively in contact with the inner circumferential face of the cylinder and the outer circumferential face of the rotational shaft 12.

[0059] A long circular roller receiving hole 51e is formed at a front end portion 51d of the vane plat 51, into which the vane roller 52 is inserted and mounted.

[0060] The roller receiving hole 51e has a certain inner diameter as large as the vane roller 51 can be inserted. The roller receiving hole 51e is preferably formed in such a structure that both sides of the vane plate 51 are all opened, but according to a designing condition, either one side may be opened or both sides may not be opened.

[0061] The vane roller 52 is formed in a circular bar structure with an outer diameter and length corresponding to the inner diameter and length of the roller receiving hole 51e and is in rolling-contact with the cam face constituted by upper and lower sides of the Z-plate 15.

[0062] The vane roller 52 is inserted and mounted in the roller receiving hole 51e, and at this time, the both end portions of the vane roller 52 may be mounted exposed outwardly of the roller receiving hole 51e.

[0063] The vanes 50 and 55 are respectively inserted into the vane slots of the first and second bearing plates 13 and 14, so that the vane roller 52 of the front end portion 51d is in rolling-contact at the upper surface and the lower surface of the Z-plate, and the both sides 51b and 51c of the vane plate 51 are respectively in contact with the inner circumferential surface of the cylinder 11 and the outer circumferential surface of the rotational shaft 12.

[0064] At this time, the vanes 50 and 55 are positioned in a radial direction, directing to the center of the Z-plate, and positioned perpendicular to the rotational shaft 12.

[0065] The roller receiving hole 51e is formed such that a center of the circular section thereof is positioned at a rather inner side than the front end portion 51d of the vane plate 51 so that the vane rollers 52 and 57 are not released therefrom.

[0066] That is, as shown in FIG. 5, the roller receiving hole 51e has a space (L) between both ends smaller than the diameter (D) of the vane rollers 52 and 57.

[0067] The operation and effect of the compressor having such a vane structure in accordance with the first embodiment of the present invention will now be described.

[0068] When power is applied to the electric mechanism unit, the Z-plate 15 is rotated together with the rotational shaft 12, and vanes 50 and 55 are vertically and reciprocally moved in the mutually opposite direction according to the height of the cam face of the Z-plate 15.

[0069] At this time, as for the vanes 50 and 55 being in contact with the upper and lower can face of the Z-plate 15, the vane rollers 52 and 57 provided at the front end portion roratably contact along the cam face of the Z-plate 15 when the vane rollers 52 and 57 are rotated, so that a friction resistance between the Z-plate 15 and the vanes 50 and 55 can be considerably reduced.

[0070] That is, the Z-plate 15 makes a rotational motion centering around the rotational shaft 12, whereas the vanes 50 and 55 make a linear motion in an axial direction of the rotational shaft 12 while being in contact at the cam face of the Z-plate. Accordingly the motion direction of the Z-plate 15 and the vanes 50 and 55 makes 90°, causing a problem of generation of a severe friction at the mutual contact side.

[0071] Comparatively, however, in the present invention, the vane rollers 52 and 57 are provided at the vanes 50 and 55, to make a rolling motion between the vanes 50 and 55 and the Z-plate 15, agreeing with the rotation direction of the Z-plate 15. Thus, a friction resistance between the Z-plate 15 and the vanes 50 and 55 can be minimized.

[0072] In order to mount the vane rollers 52 and 57, the vane rollers 52 and 57 are pushed from the side and inserted into the roller receiving hole 51e formed at each vane plate 51. Therefore, less number of parts are required to mount the vane rollers 52 and 57 and its assembly work is easy, so that a productivity degradation can be prevented.

[0073] In addition, since the center of the roller receiving hole 51e for receiving the vane rollers 52 and 57 is formed at the inner side of the contact end of the front end portion, so that the vane rollers 52 and 57 can be prevented from releasing during operation.

[0074] FIGS. 7 and 8 are a perspective view and an exploded perspective view showing a vane structure in accordance with a second embodiment of the present invention.

[0075] Compared to the construction of the first embodiment of the present invention in which only the vane rollers are inserted into the roller receiving hole, the second embodiment of the present invention proposes a structure that both sides of vanes 60 and 65 are rotatably supported by vane plates 61 and 66.

[0076] That is, in the vane plates 61 and 66, roller receiving holes 61e and 66e are formed at a front end portion being in contact with the Z-plate, of which both sides are not opened, and roller supports 61b and 66b are formed to rotatably support the vane rollers 62 and 67 by means of pin members 63 and 68.

[0077] Pin through holes 62a, 67a, 61c and 66c are formed at the vane rollers 62 and 67 and at the roller supports 61b and 66b, into which the pin members 63 and 68 are inserted.

[0078] It is preferred that the size of the roller supports 61b and 66b is adjusted such that they are formed less protruded than the vane rollers 62 and 67 so as not directly to be in contact with the Z-plate.

[0079] Meanwhile, though not presented in the drawings, protrusions may be formed at both ends of the vane rollers 62 and 67 and inserted and mounted into grooves of the roller supports 61b and 66b, without installing pin members.

[0080] FIG. 9 is an exploded perspective view showing a vane structure and a vane installation structure in accordance with a third embodiment of the present invention, and FIG. 10 and FIG. 11 are explanatory side views showing a vane operation state of the third embodiment of the present invention.

[0081] Unlike the vane rollers which are formed in a cylindrical structure with the same diameter as in the first and second embodiments as described above, a vane roller 72 in the third embodiment has a structure that it is tapering off.

[0082] That is, a roller receiving hole 71e of a vane plate 71 is form in a conical shape, for which the vane roller 72 inserted into the roller receiving hole 71e is also formed in a conical bar shape corresponding to the roller receiving hole 71e. The conical vane roller 72 is in rolling-contact with the Z-plate 15.

[0083] The vane roller 72 has a length corresponding to the length of the roller receiving hole 71e and different diameters at both end portions as it tapers off to form a conical bar shape.

[0084] The roller receiving hole 71e is formed in a conical shape with different inner diameters at both ends, of which lower surface being in contact with the Z-plate is opened.

[0085] The roller receiving hole 71e is preferably formed from the side being in contact with an outer circumference of the rotational shaft 12 to the side being in contact with an inner wall of the cylinder 11.

[0086] Namely, the roller receiving hole 71e is preferably formed penetrating both sides of the vane plate 71. In this respect, however, one side of the roller receiving hole 71e may penetrate one side of the vane plate 71 with some portion of the other side remaining, or otherwise, a roller support may be formed at both sides likewise in the second embodiment of the present invention.

[0087] The center of the roller receiving hole 71e is to be formed inclined against the front end side of the vane plate 71. The reason for this is to allow the contact surface of the tapering vane roller 72 inserted into the roller receiving hole 71e to tightly adhered onto the upper surface or the lower surface of the Z-plate 15, being level therein without a gap.

[0088] The tapering vane roller 72 is inserted such that the side with smaller diameter is positioned at the side of the rotational shaft 12 and the side with a larger diameter is positioned at the side of the inner wall of the cylinder 11.

[0089] As vane 70 is inserted into the vane slot 13a formed at the bearing plate 13, the tapering vane roller 72 is in rolling-contact with the Z-plate and both sides of the vane plate 71 are respectively in contact with the outer circumferential face of the rotational shaft 12 and the inner circumferential face of the cylinder 11.

[0090] At this time, the vane 70 is positioned in a radial direction toward the center of the Z-plate 15 and positioned perpendicular to the rotational shaft 12.

[0091] The vane 70 is elastically supported by a spring coupled at one side of the bearing plate 13. Accordingly, the vane 70 makes a rolling movement as the tapering vane roller is in line-contact with the Z-plate with an elastic force constantly.

[0092] The vane slot 13a, into which the vane 70 is inserted, is penetratingly formed at the bearing plate 13, having a width corresponding to the thickness of the vane 70 and a length corresponding to the length of the vane 70.

[0093] That is, the vane slot 13a has the same section and shape with the vane plate 71 of the vane 70.

[0094] The operation and effect of the vane structure in accordance with the third embodiment of the present invention will now be described.

[0095] When a rotational shaft 12 is rotated upon receiving a driving force from the electric mechanism unit, the Z-plate 15 is rotated along with the rotational shaft 12, to respectively and successively change the first and second spaces within the cylinder assembly into a suction area and a compression area together with vanes 70, to suck and compress and discharge a fluid.

[0096] In the above process, as the Z-plate 15 is rotated, vanes 70 being in contact with the waveform cam surface of the Z-plate are vertically moved along the cam surface, and at this time, the vane roller 72 of the vane 70 is rotated in a state of being in line-contact with the waveform curved surface of the Z-plate 15.

[0097] According to the rotation of the Z-plate 15, the vane roller 72 of the vane 70 makes a rolling movement in a state of being in line-contact with the Z-plate 15, changing the first and second space within the cylinder assembly consisting of the cylinder 11 and the bearing plate to each suction area and compression area. Hence, a friction resistance between the Z-plate 15 and the vane 70 can be minimized and movement of the vane 70 can be smoothly made.

[0098] With reference to FIG. 10, there is a difference between a curvature of an inner curved line (a) of the Z-plate 15, that is, the curved line where the rotational shaft 12 and the Z-plate 15 meet, and the inner diameter, and a curvature of an outer curved line (b) of the Z-plate 15 and the outer diameter. In this connection, if the vane roller 72 of the vane 70 is formed in a bar structure wholly having the same diameter, an infinitesimal gap may occur due to the curvature difference between the inner curved line (a) and the outer curved line (b) of the Z-plate 15. Then, an infinitesimal pressure leakage may occur between the suction area and the compression are.

[0099] However, if the vane roller 72 of the vane 70 is formed in a tapering bar shape, as shown in FIG. 11, such an infinitesimal gap possibly caused due to the curvature difference between the inner curved line (a) and the outer curved line (b) of the Z-plate 15 can be prevented from occurrence. Therefore, a friction resistance can be minimized and a pressure leakage can be prevented.

INDUSTRIAL APPLICABILITY

[0100] As so far described, according to the vane structure for a compressor of the present invention, by mounting the vane roller being in rotatably contact with the Z-plate in the vane, a friction resistance between the Z-plate and the vane can be reduced when the compressor is operated. Thus, abrasion between the Z-plate and the vane can be minimized, a noise occurrence can be restrained, durability of parts can be lengthened, and accordingly, a reliability of the compressor can be heightened.

Claims

1. A vane structure for a compressor including a cylinder assembly having a suction passage and a discharge passage, a Z-plate dividing an inner space of the cylinder assembly into a plurality of compression spaces, and sucking, compressing and discharging a fluid while being rotated by a driving unit, and vanes being in contact with both sides of the Z-plate to make a reciprocal movement, and dividing each compression space into a suction area and a compression area,

wherein the vane has a vane roller being in rolling-contact with the Z-plate.

2. The vane structure of claim 1, wherein the vane includes a vane plate reciprocally moved along both sides of the Z-plate and a vane roller provided at the vane plate and being in a rolling-contact with the Z-plate.

3. The vane structure of claim 2, wherein the vane plate includes a roller receiving hole into which the vane roller is inserted and mounted.

4. The vane structure of claim 3, wherein the vane roller is formed as a bar type with the same diameter wholly, and the roller receiving hole is formed in a hole structure having the same inner diameter.

5. The vane structure of claim 3, wherein an opened portion of the roller receiving hole so that the vane roller comes in contact with the Z-plate therethrough is smaller than a diameter of the vane roller to prevent the vane roller from releasing.

6. The vane structure of claim 3, wherein at least one of both sides of the roller receiving hole has an opened structure.

7. The vane structure of claim 3, wherein a roller support extended from the vane plate is formed at both sides of the roller receiving hole, and the vane roller can be rotatably supported by the roller support.

8. The vane structure of claim 7, wherein the vane roller is installed at the roller support through a pin member.

9. The vane structure of claim 3, wherein the vane roller is formed in a bar structure with a tapering shape, and the roller receiving hole is formed in a tapering hole structure.

10. The vane structure of claim 9, wherein the vane roller is positioned such that a side with a relatively smaller diameter is directed inward of the cylinder assembly and a side with a relatively greater diameter is directed outward of the cylinder assembly.