Weldless u-clip end suspension strut

Abstract

According to one aspect of the disclosure, a suspension strut (30) for a work machine (1) is provided. The suspension strut (30) can have a forged, one-piece cylindrical inner shell (32) including a hollow shaft (36) forming a circumferential piston (37) at an open end (38) and a lower clevis (39) at a closed end (40) of the hollow shaft (36). The suspension strut (30) can also have a forged, one-piece cylindrical outer shell (31) including a hollow barrel (52) having an interior (53) and an exterior surface (54), a closed end (55) forming an upper clevis (56), an open end (66), and a port (34) on the exterior surface (54) of the hollow barrel (52). Further, the inner and outer shells (32, 31) can be coupled by a disc-shaped end cap (65) attached to the open end (66) of the hollow barrel, an inner diameter (68) of which is slidably engaged with an outer surface (69) of the hollow shaft (36).

Description

Technical Field

[0001] The present invention relates generally to working machines, and more specifically, to suspension struts associated with working machines. Background Technology

[0002] Working machines, such as large mining trucks, consist of a carrier that undergoes multiple loading and unloading operations, thus raising and lowering the carrier relative to the machine's frame multiple times. Furthermore, when loading, the working machine may travel over rough terrain, resulting in forces and vibrations being transmitted to the carrier. Suspension struts are placed between the carrier and the working machine's axles to support the carrier and dampen any forces or vibrations from the axles to the carrier.

[0003] Traditional suspension struts may include a housing assembly that slidably houses the rod and piston assemblies. Gas or hydraulic fluid can be introduced into the suspension strut cavity through an external valve port that allows the gas or hydraulic fluid to pass through a U-shaped clamp channel located in a U-shaped clamp welded to the suspension strut. However, housing assemblies made up of multiple welded parts can introduce wear points that are prone to failure due to wear from the working machine.

[0004] U.S. Patent No. 9,285,006B2, entitled "Shock Absorber," assigned to Hitachi Automotive Systems LTD., discloses a shock absorber. The shock absorber of the '006 patent includes a piston inserted into a cylinder sealed with hydraulic oil. An outer tube is disposed around the outer periphery of the cylinder to form a reservoir between the cylinder and the outer tube. A cylindrical housing, formed by forging, is joined to a side surface portion of the outer tube, and the housing houses a damping force control valve.

[0005] However, an effective method is still needed to manufacture suspension struts that do not require welding in order to increase the structural integrity of the suspension struts. Summary of the Invention

[0006] On one hand, the present invention relates to a suspension strut for use in a working machine between a shaft and a carrier. The suspension strut may include an integral cylindrical inner shell having a hollow rod forming a circumferential piston at an open end and a lower U-shaped clamp at a closed end. The lower U-shaped clamp is used to attach the inner shell to the shaft, and a first internal fluid reservoir extends between the open and closed ends of the hollow rod. The suspension strut may also include an integral cylindrical outer shell having a hollow cylinder having an inner surface and an outer surface, a closed end forming an upper U-shaped clamp, an open end, and ports on the outer surface of the hollow cylinder. The upper U-shaped clamp is used to attach the outer shell to the carrier, and the outer surface of the cylindrical piston slidably engages with the inner surface of the hollow cylinder. The suspension strut may also include a disc-shaped end cap coupled to the open end of the hollow cylinder, having an inner diameter slidably engaging with the outer surface of the hollow rod. The inner diameter of the end cap may be smaller than the outer diameter of the circumferential piston, and the disc-shaped end cap may form a second fluid reservoir defined by the bottom surface of the circumferential piston, the inner surface of the hollow cylinder, the outer surface of the hollow rod, and the top surface of the end cap.

[0007] On the other hand, the present invention relates to a method for manufacturing a suspension strut for a working machine having a shaft and a load-bearing body. The method includes forging an integral cylindrical inner shell with a hollow rod from alloy steel, the hollow rod forming a circumferential piston at its open end and a lower U-shaped clamp at its closed end. The lower U-shaped clamp is attachable to the shaft, and a first fluid reservoir extends between the open and closed ends of the hollow rod. The method also includes forging an integral cylindrical outer shell from alloy steel, the outer shell having a hollow cylinder that may have inner and outer surfaces, a closed end forming an upper U-shaped clamp, and an open end. The outer shell may also include a port. The upper U-shaped clamp is attachable to the load-bearing body. After forging the inner and outer shells, they are heat-treated and machined to remove excess material. The method may also include providing a disc-shaped end cap having an inner diameter. The inner diameter of the end cap is smaller than the outer diameter of the circumferential piston, and the closed end of the hollow rod passes through the inner diameter of the end cap. When placed, the inner diameter of the end cap is slidably engaged with the outer surface of the hollow rod. The method may further include attaching an end cap to the open end of the hollow cylinder to provide a slidable engagement between the outer surface of the circumferential piston and the inner surface of the hollow cylinder. The engagement with the disc-shaped end cap forms a second fluid reservoir defined by the bottom surface of the circumferential piston, the inner surface of the hollow cylinder, the outer surface of the hollow rod, and the top surface of the end cap.

[0008] Furthermore, one aspect of the invention may include a method for adjusting the chassis height of a working machine, the method comprising providing a working machine having a shaft, a carrier, and a suspension strut. The suspension strut may have an integral cylindrical inner shell forming a hollow rod having a circumferential piston at an open end and a lower U-shaped clamp at a closed end. The lower U-shaped clamp may be attached to the shaft, and a first internal fluid reservoir may extend between the open and closed ends of the hollow rod. The suspension strut also has an integral cylindrical outer shell having a hollow cylinder having an inner and outer surface, a closed end forming an upper U-shaped clamp, an open end, and a port on the outer surface of the hollow cylinder. The upper U-shaped clamp may be attached to the carrier, and the outer surface of the cylindrical piston may slidably engage with the inner surface of the hollow cylinder. The suspension strut may also have a disc-shaped end cap coupled to the open end of the hollow cylinder and including an inner diameter that slidably engages with the outer surface of the hollow rod. The inner diameter of the end cap may be smaller than the outer diameter of the circumferential piston, and the disc-shaped end cap may form a second fluid reservoir defined by the bottom surface of the circumferential piston, the inner surface of the hollow cylinder, the outer surface of the hollow rod, and the top surface of the end cap. Hydraulic fluid or gaseous fluid may be sealed inside the first and second fluid reservoirs, and as the circumferential piston moves toward the closed end of the hollow cylinder, the hydraulic fluid or gaseous fluid may flow from the first reservoir to the second reservoir via a check valve. The method may also include opening a port to open the seal of the first fluid reservoir, pumping additional gaseous fluid or hydraulic oil through the port, and sealing the port.

[0009] These and other aspects and features of the invention will be more readily understood when read in conjunction with the accompanying drawings. Attached Figure Description

[0010] Figure 1 This is a side view of a working machine according to an embodiment of the present invention;

[0011] Figure 2 This is a schematic diagram of an exemplary embodiment of a suspension strut for a working machine according to various aspects of the present invention;

[0012] Figure 3 According to various aspects of the present invention Figure 2 A schematic side view of the suspension strut;

[0013] Figure 4 According to various aspects of the present invention Figure 3 A schematic cross-sectional view of the suspension strut;

[0014] Figure 5 This is a schematic cross-sectional view of an exemplary embodiment of the housing of a suspension strut according to various aspects of the present invention;

[0015] Figure 6 This is a schematic cross-sectional view of an exemplary embodiment of the inner shell of a suspension strut according to various aspects of the present invention;

[0016] Figure 7 This is a schematic cross-sectional view of an exemplary embodiment of the end cap of a suspension strut according to various aspects of the present invention.

[0017] Figure 8 This is a flowchart illustrating an example process for manufacturing a suspension strut according to various aspects of the present invention.

[0018] While the invention is readily adaptable to various modifications and alternative constructions, certain illustrative embodiments will be shown and described in detail. The invention is not limited to the specific embodiments disclosed, but encompasses all modifications, alternative constructions, and equivalents thereof. Detailed Implementation

[0019] Now refer to the attached diagram, and specifically refer to... Figure 1 The working machine consistent with certain embodiments of the invention is generally referred to by reference numeral 1. Although the working machine 1 is shown as a large mining truck (LMT), the working machine 1 is shown primarily for illustrative purposes to aid in disclosing the features of various embodiments, because Figure 1 Not all parts of the working machine are depicted. Furthermore, the readings of this invention can also be applied to other earthmoving and construction machinery.

[0020] The working machine 1 may include a frame 2 supported by rear wheels 3 and front wheels 4. Although the front wheels 4 and rear wheels 3 are shown, other support and movement devices (not shown) may be tracks or any other type. A cab 5 may be mounted on the frame 2, where the operator of the working machine 1 sits. Those skilled in the art will understand that an engine 6 can provide propulsion to the wheels. The working machine also includes an axle 8 attached to the rear wheels 3 and a carrier 10. The carrier is connected to the frame 2 via a pivot pin 11 and a hydraulic cylinder 12, such that the load contents of the carrier 10 can be removed by controllably pressurizing the cylinder 12 to achieve pivoting movement of the carrier 10 about the pivot pin 11. The cylinder may be actuated by any number of hydraulic pumps and pipes (not shown) powered by the engine 6 or other power source. In transport mode, the cylinder 12 is not pressurized, and the weight of the carrier 10 is transferred to the frame via the pivot pin 11 and the rear suspension strut 13 located between the axle 8 and the carrier 10. Although the present invention is primarily directed toward rear suspension struts, such as rear suspension strut 13, those skilled in the art will recognize that the principles described herein also apply to front suspension struts, such as front suspension strut 14.

[0021] Reference Figure 2-4An exemplary embodiment of a suspension strut 30 having an integral outer shell 31 and an integral inner shell 32 joined together by end caps (discussed below) is shown. Each of the outer shell 31 and the inner shell 32 is not an assembly of multiple parts attached by welding, but rather a single integral component formed by forging (an overheated cylindrical member is pressed against a centrally, axially aligned die to form a void), resulting in the port 34 (discussed below) being integrated into the upper outer shell 31.

[0022] like Figure 4 As shown, the one-piece cylindrical inner shell has a hollow rod 36, which defines a circumferential piston 37 at its open end 38 and has a lower U-shaped clamp 39 at its closed end 40. The hollow rod may have an inner diameter 41 and an outer diameter 42. In this embodiment, the circumferential piston 37 may have an inner diameter 43 and an outer diameter 44, the inner diameter 43 being at least partially the same as the inner diameter 41 of the hollow rod 36 and the outer diameter 44 of the circumferential piston 37 being larger than the outer diameter 42 of the hollow rod 36. The hollow rod forms a first fluid reservoir 45, as... Figure 4 As shown, it extends between the open end 38 and the closed end 40 of the hollow rod 36. Figure 3 As shown, the lower U-shaped clamp 39 may also include first and second elongated members 46, 47 extending from the closed end of the hollow rod 40. (As shown...) Figure 2 As shown, elongated members 46 and 47 define first and second holes 48 and 49. Elongated members 46 and 47 and holes 48 and 49 allow the lower U-shaped clamp 39 to be attached to the shaft 8 of the working machine 1.

[0023] The one-piece cylindrical housing has a hollow cylinder 52 with an inner surface 53 and an outer surface 54. An upper U-shaped clamp 56 is formed on the closed end 55 of the hollow cylinder 52, configured to be attached to the carrier 10 of the working machine 1. In one embodiment, the outer surface 57 of the circumferential piston 37 slidably engages with the inner surface 53 of the hollow cylinder. In another embodiment, one or more bearings 58 may be placed between the circumferential piston 37 and the inner surface 53 of the hollow cylinder 52 to facilitate sliding engagement. Furthermore, a lifting ring 59 may be attached to the outer surface 54 of the hollow cylinder 52 for lifting the suspension strut 30. Figure 2 As shown, a warning and information label 60 or nameplate 74 with markings can be placed on the outer surface 54 of the hollow cylinder 52. Additionally, as... Figure 3 As shown, the upper U-shaped clamp 56 may further include third and fourth elongated members 61, 62 extending from the closed end of the hollow cylinder 52. Figure 2 As shown, elongated members 61 and 62 define third and fourth holes 63 and 64. Elongated members 61 and 62 and holes 63 and 64 allow the upper U-shaped clamp 56 to be attached to the support body 10 of the working machine 1.

[0024] To seal the suspension strut 30 and prevent the inner housing 32, which has a circumferential piston 37 that slides into the inner surface 53 of the hollow cylinder, from slipping out, a disc-shaped end cap 65 is provided. The end cap 65 is coupled to the open end 61 of the hollow cylinder 52. This coupling can be accomplished using one or more bolts 67 or other coupling devices. The inner diameter 68 of the end cap 65 can slide into the outer surface 69 of the hollow rod 36, thereby allowing the hollow rod 36 to extend into and retract into the hollow cylinder 52. In an exemplary embodiment, the disc-shaped end cap 65 may form a second fluid reservoir 71 defined by the bottom surface 72 of the circumferential piston 37, the inner surface 53 of the hollow cylinder 52, the outer surface 69 of the hollow rod 36, and the top surface 73 of the end cap. During the retraction and extension of the inner housing 32 into and out of the outer housing 31, the second fluid reservoir 71 allows one or more liquid or gaseous fluids to flow between the first and second reservoirs 45, 71.

[0025] In one exemplary embodiment, the hollow cylinder 52 may also include a port 34 located on its outer surface 54. The port 34 may further include one or more holes (not shown) sealed by a sealing plate (not shown). These one or more holes extend from the inner surface 53 of the hollow cylinder 52 to its outer surface 54 and allow fluid to be pumped through the port 34 into a first fluid reservoir 45. These fluids may include liquid fluids, such as hydraulic fluid oil, including 10W hydraulic oil or equivalent, and gaseous fluids, such as nitrogen or other gaseous fluids used for suspension struts.

[0026] In the manufacture of the suspension strut 30, the inner shell 32, the integral body forming the hollow rod 36, the circumferential piston 37, and the lower U-shaped clamp 39 are forged from alloy steel into an integral shell. Furthermore, the outer shell 31, an integral body forming the upper U-shaped clamp 56 and the hollow cylinder 52 with internal ports 34, is also forged from alloy steel into an integral shell. The alloy steel used to form the inner shell 31 and the outer shell 32 can be 4130 steel or other alloy steel compounds. After forging, the inner shell 31 and the outer shell 32 are heat-treated and then machined to remove any excess material generated during the forging process. Specifically, the upper and lower U-shaped clamps 56 and 39 are machined to remove excess material to form the first, second, third, and elongated members 46, 47, 61, and 62, and their corresponding holes, including the first, second, third, and fourth holes 48, 49, 63, and 64. After processing, before the end cap 65 is attached to the outer shell 31, the inner shell 32 is placed through the end cap 65, thereby assembling the integral outer shell 31 and the integral inner shell 32 into the suspension strut 30.

[0027] Once assembled, a charging operation is performed on the suspension strut 30. The charging operation involves first pumping a liquid fluid, such as hydraulic oil, at atmospheric pressure through port 34 and into a first fluid reservoir 45 until the inner shell 32 begins to extend 0.5 to 2 inches from the outer shell 31. This extension occurs when the liquid fluid begins to fill the first fluid reservoir 45 and the circumferential piston 37 begins to move toward the open end 66 of the hollow cylinder 52. After the inner shell 32 extends, a gaseous fluid, such as nitrogen, is pumped under pressure into the first fluid reservoir 45 through port 34. This pumping of the gaseous fluid causes any air inside the suspension strut to escape through a vent (not shown) in port 34, further causing the inner shell 32 to extend. Once the desired chassis height is reached, in one exemplary embodiment, port 34 is sealed with a sealing plate, but other sealing devices may be used.

[0028] Once manufactured and attached to the working machine, hydraulic oil will be located at the bottom of the first fluid reservoir 45, with gaseous fluid above the hydraulic oil in the first fluid reservoir 45. The gaseous fluid provides the elastic mechanism for the suspension strut. When a force is applied to the shaft 8 or the carrier 10, the inner shell 32 will retract into the outer shell 31, causing the circumferential piston 37 to move toward the closed end 55 of the hollow cylinder 52. This retraction will cause the liquid and gaseous fluids to mix. Because the gaseous fluid is compressible and the liquid fluid is incompressible, the pressure inside the first hydraulic reservoir 45 will increase, causing the mixture of liquid and gaseous fluids to pass through the check valve 76 and enter the second fluid reservoir 71. The check valve 76 may be a pressure valve, allowing fluid to pass only after reaching a pressure limit. The suspension strut 30 will then stabilize, and fluid will flow from the second reservoir 71 back to the first reservoir 45 through a drilled hole 80 located in the wall of the hollow strut 36, causing the circumferential piston 37 to move toward the open end 66 of the hollow cylinder 52. The inner shell 32 retracts into and extends out of the outer shell 31 to allow the suspension strut 30 to absorb forces and prevent forces from being transmitted from the shaft 8 to the load body 10, or from the shaft 8 to the load body 10.

[0029] In another embodiment, after the carrier 10 is attached to the machine tool 1, the chassis height of the carrier 10 can be adjusted by first opening the first reservoir 45 by removing a sealing plate or other sealing device. Once opened, more liquid fluid (at atmospheric pressure) or gaseous fluid (above atmospheric pressure) can be pumped through the port until the desired chassis height is achieved. If it is necessary to lower the chassis height, the liquid or gaseous fluid can be discharged through the drain valve 77. It is desirable to place the drain valve at the closed end 40 of the hollow rod 52 to allow fluid to be discharged from the reservoir by gravity.

[0030] Furthermore, an end cap bearing 78 may be present between the end cap 65 and the outer surface 69 of the hollow rod 36. To better seal the suspension strut and prevent fluid leakage or debris from entering between the end cap and the hollow rod, the end cap 65 may also include a primary pressure seal 81, a second protective seal 82, and a debris seal 83 as pressure or lubricating fluid seals. Additionally, the end cap 65 may include a cover plate 85, which covers the bolts 67 securing the end cap 65 to the hollow cylinder 52. This cover plate 85 serves to prevent the user from loosening the end cap 65 because the contents of the reservoir are under pressure when the end cap 65 is sealed. In one embodiment, the end cap 65 may include a safety passage (not shown) that allows a small amount of pressurized fluid to flow from a second fluid reservoir 71 or, in some embodiments, a first fluid reservoir 45, to the connection between the end cap 65 and the cover plate 85. Therefore, in this embodiment, when the user attempts to remove the cover plate 85, a small amount of pressurized fluid is released, warning the user that the suspension strut 30 contains pressurized fluid. In addition, another sealing ring 86 may be present between the end cap 65 and the inner surface 53 of the hollow cylinder 52.

[0031] Industrial applicability

[0032] Generally, the above-disclosed information can be used in various applications, such as earthmoving, construction, industrial, agricultural, mining, transportation, and forestry machinery. In particular, the disclosed suspension struts can be used in large mining trucks (LMTs) and other applications, such as smaller mining trucks. By applying the disclosed suspension struts, the method of manufacturing the suspension struts, and the method of adjusting the chassis height of the working machine, optimal elimination of fault points in conventional suspension struts and improved manufacturing efficiency of suspension struts can be achieved.

[0033] In particular, the disclosed suspension struts offer a one-piece inner shell and a one-piece outer shell, each forged as a single component, thus eliminating the need for welding. Furthermore, the suspension struts can be attached to the axles and carriers of large mining trucks and are designed to adjust the chassis height of the work machine carrier while the suspension struts are attached, thereby minimizing interference with mining operations.

[0034] Turn now Figure 8 Continue to refer to Figure 2-7 A flowchart illustrating an example process 100 for manufacturing a working machine is disclosed. In blocks 102-104, a one-piece inner shell 32 and a one-piece outer shell 31 are forged. Figure 6 As shown, the inner shell 32 includes a circumferential piston 37, a hollow rod 36, and a lower U-shaped clamp 39, all forged into a single structure. Figure 5 As shown, the outer shell 31, including the upper U-shaped clamp 56 and the hollow cylinder 52, is forged into a single structure.

[0035] In frame 106, the inner shell 32 and outer shell 31 are heat-treated prior to machining in frame 108 to remove excess material from the forging process. Excess material may include excess alloy steel removed from the upper and lower U-shaped clamps 56, 39.

[0036] In frame 110, the inner shell 32 is inserted through the end cap 65, as shown. Figure 7 As shown, the end cap is attached to the housing 31 to form the suspension strut 30. In block 110, a filling procedure is performed by pumping liquid and gaseous fluids into the suspension strut through an internal port located on the side of the hollow cylinder 52.

[0037] Although several different embodiments have been described in detail above, it should be understood that their legal scope is defined by the words of the claims appended to this patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment, as describing every possible embodiment would be impractical, if not impossible. Many alternative embodiments may be implemented using current technology or technology developed after the date of this patent application, which still fall within the scope of the claims defining the protection.

[0038] It should also be understood that unless a term is explicitly defined herein, there is no intention to limit the meaning of such term, whether expressly or implied, beyond its ordinary or general meaning, and such terms should not be construed as limiting the scope of any statement made in any part of this patent (other than the language of the claims). To some extent, any term referenced in the claims at the end of this patent is referred to herein in a manner consistent with a single meaning, done only for clarity and to avoid confusing the reader, and is not intended to limit such claim terms to that single meaning by implication or otherwise.

Claims

1. A suspension strut (30) for use on a machine (1) between a shaft (8) and a carrier (10), comprising: An integral cylindrical inner shell (32) includes a hollow rod (36) defining a circumferential piston (37) at an open end (38) and a lower U-shaped clamp (39) at a closed end (40). The integral body forming the hollow rod (36), the circumferential piston (37), and the lower U-shaped clamp (39) is forged from alloy steel into an integral inner shell. The lower U-shaped clamp (39) is configured to be attached to the shaft (8), and a first fluid reservoir (45) extends between the open end (38) and the closed end (40) of the hollow rod (36). An integral cylindrical shell (31) forged from alloy steel includes a hollow cylinder (52) having an inner surface (53) and an outer surface (54), a closed end (55) forming an upper U-shaped clamp (56), an open end (66), and a port (34) on the outer surface (54) of the hollow cylinder (52), wherein the upper U-shaped clamp (56) is configured to be attached to the carrier (10) and the outer surface (57) of the circumferential piston (37) is slidably engaged with the inner surface (53) of the hollow cylinder (52); the port (34) includes one or more holes extending from the outer surface (54) of the hollow cylinder (52) to the inner surface (53) of the hollow cylinder (52); and A disc-shaped end cap (65) is connected to the open end (66) of the hollow cylinder (52) and has an inner diameter (68) that slides into the outer surface (69) of the hollow rod (36), wherein the inner diameter (68) of the end cap (65) is smaller than the outer diameter (44) of the circumferential piston (37). The disc-shaped end cap (65) forms a second fluid reservoir (71) defined by the bottom surface (72) of the circumferential piston (37), the inner surface (53) of the hollow cylinder (52), the outer surface (69) of the hollow rod (36), and the top surface (73) of the end cap (65).

2. The suspension strut (30) according to claim 1, wherein, The upper and lower U-shaped clamps (56, 39) each further include two elongated members (46, 47, 61, 62), which independently define holes (48, 49, 63, 54) configured for attachment to the working machine (1).

3. The suspension strut (30) according to claim 1, wherein, The one or more orifices are configured to allow fluid to be pumped into the first fluid reservoir (45) through the one or more orifices.

4. The suspension strut (30) according to claim 3, wherein, The fluid is hydraulic oil and the fluid is pumped through the one or more orifices until the integral cylindrical inner shell (32) begins to extend from the integral cylindrical outer shell (31). After the integral cylindrical inner shell (32) begins to extend, a second fluid comprising gas is pumped through the one or more orifices and the one or more orifices are sealed by a sealing plate.

5. The suspension strut (30) according to claim 1, wherein, The circumferential piston (37) also includes a check valve (76) configured to allow fluid to flow from the first fluid reservoir (45) into the second fluid reservoir (71) as the circumferential piston (37) moves toward the closed end (55) of the hollow cylinder (52).

6. The suspension strut (30) according to claim 5, wherein, The hollow rod (36) also includes one or more boreholes (80) configured to allow fluid to flow from the second fluid reservoir (71) into the first fluid reservoir (45) when the circumferential piston (37) is removed from the closed end (55) of the hollow cylinder.

7. A method for manufacturing a suspension strut (30) for a working machine (1) having a shaft (8) and a load-bearing body (10), the method comprising: An integral cylindrical inner shell (32) forged from alloy steel includes a hollow rod (36) forming a circumferential piston (37) at an open end (38) and a lower U-shaped clamp (39) at a closed end (40), wherein the lower U-shaped clamp (39) is configured to be attached to the shaft (8) and a first fluid reservoir (45) extends between the open end (38) and the closed end (40) of the hollow rod (36); A one-piece cylindrical shell (31) forged from alloy steel includes a hollow cylinder (52) having an inner surface (53) and an outer surface (54), a closed end (55) defining an upper U-shaped clip (56) and an open end (66), wherein the upper U-shaped clip (56) is configured to be attached to the carrier (10) and the hollow cylinder (52) has a port (34) on its outer surface (54); the port (34) includes one or more holes extending from the outer surface (54) of the hollow cylinder (52) to the inner surface (53) of the hollow cylinder (52); The inner shell (32) and the outer shell (31) are subjected to heat treatment; The inner shell (32) and the outer shell (31) are machined to remove excess material; A disc-shaped end cap (65) with an inner diameter (68) is provided, wherein the inner diameter (68) of the end cap (65) is smaller than the outer diameter (44) of the circumferential piston (37); The closed end (40) of the hollow rod (36) is placed through the inner diameter (68) of the end cap (65), and after placement, the inner diameter (68) of the end cap (65) is configured to slidably engage with the outer surface (69) of the hollow rod (36). The end cap (65) is coupled to the open end (66) of the hollow cylinder (52) to provide a slidable engagement between the outer surface (57) of the circumferential piston (37) and the inner surface (53) of the hollow cylinder (52), wherein the engagement with the disc end cap (65) is configured to form a second fluid reservoir (71) defined by the bottom surface (72) of the circumferential piston (37), the inner surface (53) of the hollow cylinder (52), the outer surface (69) of the hollow rod (36) and the top surface (73) of the end cap (65).

8. The method according to claim 7, wherein, During the machining of the inner shell (32) and the outer shell (31), excess material is removed from the upper U-clamp (56) and the lower U-clamp (39) to form two elongated members (46, 47, 61, 62) on each of the upper U-clamp (56) and the lower U-clamp (39), each of the elongated members (46, 47, 61, 62) also defining a hole (48, 49, 63, 64), the port (34) being formed by the machining.

9. The method according to claim 8, wherein, The method further includes pumping hydraulic oil through the port (34) into the first fluid reservoir (45) at atmospheric pressure until the circumferential piston (37) slides 0.5 to 2 inches toward the open end (38) of the hollow cylinder (52).

10. The method according to claim 9, wherein, After the hydraulic oil is pumped in, the method further includes pumping a pressurized gaseous fluid through the port (34) to further slide the circumferential piston (37) toward the open end (38) of the hollow cylinder (52), and sealing the port (34) after pumping the gaseous fluid.

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