FIELD OF INVENTION

The present invention relates to a linear actuator. In more particular, the present invention relates to a mounting connection of a linear actuator for accuracy of alignment during installation and absorption of vibration during operation.

BACKGROUND OF THE INVENTION

Cylinders or actuators are used in various mechanical tasks to deliver reciprocating linear force. In a piling machine, actuators are used to lift a piling hammer to a highest point, release and drop it to drive piles into the ground for foundation. The piling hammer and the actuator, especially a cylinder barrel holding a piston rod, must be in coaxial relation with one another so that the actuator aligns with a housing of the piling hammer in order to allow smooth operation and prevent piston rod to break due to misalignment.

There are some patented technologies over the prior arts relating to mounting structure of a hydraulic cylinder. Of interest is a United States Patent No. US 4488701, which discloses a mounting structure for coupling a housing to a support plate that requires no tool or fasteners for mounting the housing in position. However, this prior art did not mentioned about any tapered flange surface of the mounting structure to facilitate accurate centre positioning of the mounting structure.

Another United States Patent No. US 3185043 discloses an improved cylinder having interchangeable parts, rapid convertibility to a desired function, sturdy structure that is light and may be rapidly assembled and dismantled. However, the cylinder comprises a cylinder barrel with a lock-up screw in its axial bore for anchoring the cylinder barrel against axial movement. The prior art did not focus on any taper configuration of the cylinder barrel for centre positioning during assembly of parts.

In still another United States Patent No. US 5487326, a hydraulic cylinder is disclosed by having a gland retainer welded to a cylinder barrel and a split ring spring retainer removably inserted into the gland retainer to hold a rod gland in place. However, this prior art .merely discloses connection . between the cylinder barrel and the gland retainer. It did not focus on connection between the cylinder barrel and a structure to be actuated.

In yet another United States Patent No. US 4529232, a flange connection for connecting hollow cylinder barrels in series forming a screw press is disclosed. The barrel flange connection requires no welding and the barrels can be easily detached therefprm. However, this prior art did not mentioned any approach to shape the flange with tapered ends for facilitating vertical installation of the cylinder into a piling hammer. The actuators should be placed in the centre position of the piling machine and the position should be easily adjustable during installation. Therefore, it is highly desirable for the present invention to produce an innovative mounting connection for the linear actuator which is capable of ensuring accurate installation of the actuator in the piling hammer. In an event that the actuator needs to be changed in a piling machine, fast and accurate installation can be achieved and non-productive time can be minimized.

SUMMARY OF INVENTION The primary object of the present invention is to provide a solution to correct misalignment of a linear actuator immediately above a fitting of a piling ram. Assembly of the linear actuator can be speeded up, calibration time can be reduced and non-productive downtimes can be minimized which therefore, resuming work in a relatively fast pace.

It is another object of the present invention to provide a linear actuator with a convenient structure where misalignment can be corrected even after putting the linear actuator into the casing. For further adjustment, the linear actuator is not required to be taken out from the casing. This allows the linear actuator to be aligned with a to-be-connected load.

At least one of the proceeding objects is met, in whole or in part, by the present invention, in which the preferred embodiment of the present invention describes a piling ram comprising a hollow elongated casing having an upper section connected to a lower section; a load positioned at the lower section of the casing; an assembly of linear actuator, which is defined by a barrel enclosing a piston rod fashioned to slidably move in related to the barrel, having one end of the piston rod attached onto the load and a free end extended from a circular flange of the barrel; a fitting located at the top of the casing for housing the circular flange; and a fluid driving system in communication with the assembly of linear actuator to operate the movement of the piston rod in related to the barrel to move the load within the lower section characterized in that the circular flange has the side edge tapered downwardly to facilitate the circular flange to slidably self-align into the fitting upon occurrence of misalignment of the circular flange immediately above the fitting.

One of the preferred embodiment of the present invention discloses that the piling ram further comprising a hollow passageway fabricated within the flange with an inlet and an outlet for fluid input and fluid output respectively.

Another preferred embodiment of the present invention discloses that the inlet and outlet comprising relief valves for controlling fluid input and output respectively.

In an embodiment of the present invention, the tapered side edge has an angle ranging from 30 degrees to 70 degrees in relative to the vertical axis of the barrel.

Another embodiment of the present invention is that the fluid driving system is a hydraulic driving system or a pneumatic driving system.

Still another embodiment of the present invention is that the assembly of linear actuator is secured in the fitting by a plurality of gaskets and washers. The present preferred embodiments of the invention consists of novel features and a combination of parts hereinafter fully described and illustrated in the accompanying drawings and particularly pointed out in the appended claims; it being understood that various changes in the details may be effected by those skilled in the arts but without departing from the scope of the invention or sacrificing any of the advantages of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawing the preferred embodiments from an inspection of which when considered in connection with the following description, the invention, its construction and operation and many of its advantages would be readily understood and appreciated. Figure 1 shows a front view of a piling ram (100) in accordance to the preferred embodiments of the present invention. Figure 2 shows a cross sectional view taken at A - A of Figure 1 in accordance to the preferred embodiments of the present invention.

Figure 3 shows an enlarged cross sectional view taken at B of Figure 2 in accordance to the preferred embodiments of the present invention.

Figure 4 shows an exploded view of Figure 3 in accordance to the preferred embodiments of the present invention.

Figure 5 shows an exploded and fragmented front view of an assembly of linear actuator (105) and a casing (101) in accordance to the preferred embodiments of the present invention.

Figure 6 shows an enlarged front view of the assembly of linear actuator (105) and the casing (101) in accordance to the preferred embodiments of the present invention.

Figure 7 shows an enlarged cross sectional, view of a circular flange (203) and fitting (205) as known in the prior art.

Figure 8 shows an enlarged cross sectional view of a circular flange (111) and a fitting (113) in accordance to the embodiments of the present, invention.

Figure 9 shows an enlarged view taken at C of Figure 3 in accordance to the embodiments of the present invention. Figure 10 shows a cross sectional view of the piling ram (100) in accordance to the preferred embodiments of the present invention.

Figure 11 shows an enlarged view taken at D of Figure 10 in accordance to the preferred embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the invention shall be described according to the preferred embodiments of the present invention and by referring to the accompanying description and drawings. However, it is to be understood that limiting the description to the preferred embodiments of the invention and to the drawings is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim.

The present invention relates to a linear actuator. In more particular, the present invention relates to a mounting flange of a linear actuator for accurate ^'4 alignment during installation and absorption of vibration during operation.

One of the preferred embodiment of the present invention discloses that a piling ram (100) comprising a hollow elongated casing (101) having an upper section connected to a lower section; a load (103) positioned at the lower section of the casing (101); an assembly of linear actuator (105), which is defined by a barrel (107) enclosing a piston rod (109) fashioned to slidably move in related to the barrel (107), having one end of the piston rod (109) attached onto the load (103) and a free end extended from a circular flange (111) of the barrel (107); a fitting (113) located at the top of the casing (101) for housing the circular flange (111); and a fluid driving system in communication with the assembly of linear actuator (105) to operate the movement of the piston rod (109) in related to the barrel (107) to move the load (103) within the lower section characterized in that the circular flange (111) has the side edge (111a) tapered downwardly to facilitate the circular flange (111) to slidably self-align into the fitting (113) upon occurrence of misalignment of the circular flange (111) immediately above the fitting (113).

Accordingly, the linear actuator as described in the present invention refers to an actuator that provides linear motion. The linear actuator comprising the elongated piston rod (109) connected to a piston (115), where most part of the piston rod (109) moves reciprocally within the barrel (107). A gap (123) between the piston rod (109) and an inner periphery of the barrel (107) is filled with the fluid and the fluid is secured within the barrel (107) by a head cover (117) at each end of the barrel (107). The head cover (117) seals the fluid within the barrel (107) and prevent compression lost. The linear actuator can be driven by fluid or in combination with gravity. Preferably, the fluid driving system a hydraulic driving system or a pneumatic driving system for better controllability of the motion compared to the driving system using gravity. The linear actuator can be a single-acting or a double acting actuator, but preferably a double-acting actuator with double-ended piston rod due to better controllability of stroke and displacement. The double-acting actuator uses the fluid to force the piston (115) within the barrel (107) to move in both extend and retract strokes. The actuator have at least two fluid ports to allow fluid input or output, one for the extend stroke and one for the retract stroke. The linear actuator is preferred to be operated vertically in relative to a pile to be driven. In another embodiment of the present invention, for the linear actuator powered by the hydraulic fluid driving system, the hydraulic oil is preferred to be supplied by a hydraulic fluid source and pressure within the hydraulic fluid driving system is maintained by accumulators (125). The accumulator (125) is a pressure storage reservoir functioning to maintain the pressure in the driving system during leakage, cope with extremes of demand using a less powerful pump, respond more quickly to a temporary demand and smooth out pulsations. The accumulator (125) is also helpful during changes of temperature range, where the accumulator (125) helps to absorb pressure excursions where the hydraulic fluid might otherwise be locked in a fluid passageway or within barrel (107) with no room for expansion due to the fluid passageway arrangement.

In a further embodiment of the present invention, a hollow passageway is fabricated within the circular flange (111) with an inlet and an outlet (127) for fluid input and fluid output respectively. The inlet is supplied with pressurized fluid and the pressurized fluid is exhausted through the outlet (127). Depending on the type of the linear actuator used, the inlet and outlet (127) is interchangeable when the actuator retracts or extends. Relief valves may be connected to the inlet and outlet for controlling fluid flow. For the double-acting hydraulic actuator, an unbalanced pressure of hydraulic fluid acting on alternate sides of the piston (115) controls position of the piston (115) in the barrel (107). The piston (115) moves between an upper position and a lower position within the barrel (107) upon supplying or exhausting the fluid from the inlet or outlet (127). Movement of the piston (115) causes the connected piston rod (109) to move reciprocally to the barrel (107).

In a preferred embodiment of the present invention, the circular flange (111) has side edge (111a) tapered towards the barrel (107). The circular flange (111) is preferred to be integrally cast or molded at a circumferential of the barrel (107). Preferably, the circular flange (111) is located at a top end of the barrel (107), extended horizontally from the circumferential of the barrel (107) and the side edge (111a) of the circular flange (111) tapers downwardly to the circumferential of the barrel (107) to form a truncated cone shape from a cross section view as depicted in Figure 5.

In the prior art as shown in Figure 7, the circular flange (203) is provided with a flat bottom surface and a matching flat circular fitting (205) to receive the circular flange (203). This arrangement is not desirable by the present invention mainly because during installation of the assembly of linear actuator (105) into the casing (101), the circular flange (203) might be disposed on a top surface of the fitting (205). Adjustment of such misplacement can only be achieved by lifting up the assembly of linear actuator (105) and put it into the fitting (205) of the casing (101) again. The assembly of linear actuator (105) for used in the piling ram (100) is extremely heavy. Therefore, lifting of the linear actuator must be carried out by a mechanical lifting equipment such as a forklift, crane or other mechanical lifting device. The assembly of linear actuator (105) might need several lifting before being successfully disposed into the fitting (205). Moreover, during operation of the piling ram, the circular flange (203) have a high tendency of abrasion with the fitting (205) by the continuous vibration caused by the impact and the fitting (205) tends to worn out. The circular flange (203) has no tendency to move during the vibration. This might cause the piston rod to fracture or break as the vibration which oscillates back and forth along the piling ram cannot be transmitted to other parts but return back to a weakest point of the piling ram, which may be the piston rod. As a result, the worn out fitting (205) has to be replaced by changing the casing (101) as the fitting (205) is attached to the casing (101). Lifespan of the linear actuator is consequently reduced and maintenance of such a piling ram is increased.

Another preferred embodiment of the present invention describes that the circular flange (111) is preferred to be extended horizontally from one end of the barrel (107). The tapered side edge (111a) is preferred to be in an angle ranging from 30 degrees to 70 degrees in relative to the vertical axis of the barrel (107). Most preferably, the tapered side edge (111a) is 45 degrees in relative to the vertical axis of the barrel (107). The fitting (113) is preferred to be extended from an inner periphery and located at the centre of the casing (101). The fitting (113) has a matching shape and dimension with the circular flange (111), in which it is tapered at its lower inner periphery. The tapered side edge (111a) of the circular flange is in a sliding contact with the top surface or top internal edges of the fitting (113). Beneficially, the assembly of linear actuator (105) can be fitted into the fitting (113) even when the assembly of linear actuator (105) fails to approach the top centre of the fitting (113), as depicted in Figure 8. This is because when the tapered side edge (111a) is placed immediately on the top surface of the fitting (113), the tapered side edge (111a) tends to slide downwardly from the top surface, causing the circular flange (111) to slide to the centre of the fitting (113). No lifting of the assembly of linear actuator (105) is required during misplacement but merely to continue dropping the assembly of linear actuator (105) slowly into the fitting (113). The fitting (113) may consist of a collar or ring to hold on to the circular flange (111). Subsequently, the load or piling weight (103) can be connected to the end of the piston rod (109).

Still another preferred embodiment of the present invention describes that the assembly of linear actuator (105) is secured in the fitting (113) by a plurality of gaskets and washers. At least one top cover plate (121) is secured on top of the circular flange (111) and fixed to the fitting (113) by a plurality of fasteners such as bolts and nuts, or screws. Preferably, a resilient washer (119) is placed between the top cover (121) and the top surface of the circular flange (111). The resilient washer (119) is most preferred to be made of polyurethane rubber for isolating shock produced from impact of the load (103) towards the top coyer plate (121) or any other washers and gaskets. Non-stick coating such as Teflon may be applied between the gaskets and washers for providing properties such as low friction, chemical resistance, wear resistance and heat resistance.

In yet another preferred embodiment of the present invention, further alignment of the linear actuator can be performed by adjusting the end of piston rod (109) to the load (103). A gap (131) between the circular flange (111) and the fitting (113), as shown in Figure 9, permits slight movement of linear actuator during operation. With the gap (131) between the fitting (113) and the circular flange (111), the linear actuator can be rotated to an angle ranging from -5.1° to 5.1° in relative to the vertical axis of the piling ram (100). Both Figure 10 and 11 show the linear actuator is tilted to a maximum angle of 5.1°, as labelled in 'F, in relative to the vertical axis, as labelled in Έ', of the piling ram (100) before being secured to the load (103). The tapered side edge (111a) functions as a rotatable joint between the linear actuator and the casing (101). The gap is preferred to be approximately 1mm to 2mm in width. During operation, impact of the piling ram causes vibration towards the linear actuator where the vibration travels back and forth along the piling ram (100). The tapered side edge (111a) of the circular flange (111) tends to slide at the tapered surface of the fitting (113) during vibration. On the side of the circular flange (111) where the tapered side edge (111a) slides upwards, it tends to upwardly push the resilient washer (119), which is placed on top of and in contact with the linear actuator. Due to the natural elasticity of the resilient washer (11 ), it returns to its initial shape when the pushing force is removed and the tapered side edge (111a) slides back to the centre of the fitting (113). Therefore, there is no major abrasion between the tapered side edge (111a) and the fitting (113) but merely sliding contact. As a result, the tapered side edge (111a) increases the absorption of vibration during operation which prolongs the lifespan of the piling ram (100). The present invention also ensures proper alignment of the assembly of linear actuator (105) which ultimately cuts down installation and calibration time.

While the invention has been disclosed in connection with the preferred embodiments shown and described in detail, various modifications and improvements thereon will become readily apparent to those skilled in the art. Accordingly, the spirit and scope of the present invention is not to be limited by the foregoing examples, but is to be understood in the broadest sense allowable by law.