The present invention relates to pistons and is more particularly concerned with a piston with a polygonal section to prevent rotation thereof about its displacement axis.

BACKGROUND OF THE INVENTION

It is well known in the art of piston-rod assemblies to prevent rotation thereof using key-slot arrangements, rod square sections, and the like.

It is well known in the art to build non-rotating pistons or weights not having rods connected thereto, especially pistons having an elliptical section (rather than circular), in order to prevent twisting of cable or the like connected thereto. The main drawback of this elliptical piston is the cost of machining thereof, which is even worse when dealing with large size pistons, of a few feet in diameter or the like. Furthermore, when dealing with large size pistons, even circular or elliptical section pistons are quite expensive to manufacture, especially when referring to the seal between the piston and its housing of the same sectional shape.

When dealing with large structures and large size pistons, one may need to control a predetermined gap size between the seal and the piston housing (such as to allow a predetermined fluid leak that serves as lubricant between the piston and the housing), which is almost impossible to do when dealing with oval or elliptical piston shapes, as opposed to polygonal shapes having rectilinear section edges and corners at the different edge intersections.

Accordingly, there is a need for an improved non-rotating piston. SUMMARY OF THE INVENTION

It is therefore a general object of the present invention to provide an improved non-rotating piston that solves the above-mentioned disadvantages and drawbacks. An advantage of the non-rotating piston of the present invention is that it does ensure that any flexible link connected thereto, such as cables or the like, are not being twisted whatsoever.

Another advantage of the non-rotating piston of the present invention, especially when it has a polygonal section is that the seal between the piston and its housing is along rectilinear sections, and at the angles between two adjacent edges of the polygon, corner seals are used, and these corner seals are relatively inexpensive when the angle is about 90 degrees, the further away the angle is from 90 degrees, the more complicated and expensive it gets (especially when the angle is acute). A further advantage of the non-rotating piston of the present invention, especially when it has a polygonal section is that the gap between the seal of the piston and the housing is easily controllable, as to ensure predetermined leakage of pressurized fluid there through for lubrication there between.

Yet another advantage of the piston of the present invention is that it includes a top seal to ensure seal contact with a top wall of the housing to prevent air (or pressure fluid) leakage when the piston reached its maximum top position within the housing.

According to an aspect of the present invention there is provided a non-rotating piston for slidable and longitudinal displacement within a corresponding channel housing defining a housing axis thereof, said piston comprising:

a body having a polygonal section formed with a plurality of rectilinear section edges defining corners therebetween, the body defining a piston axis being locally coaxial with the housing axis; a seal assembly mounted on the body for operably interfacing with an inner wall of the housing, the seal assembly including, along each said section edge, at least one seal plate being biased radially outwardly towards the housing inner wall in a direction generally perpendicular to said respective section edge, and at each said corner, a seal wedge slidably and sealably connected to respective said seal plates of the section edges defining said corner, the seal wedge being biased radially outwardly towards a respective inner corner of the housing defined by corresponding housing inner walls. In one embodiment, each said at least one seal plate is biased towards the respective inner wall of the housing by a plurality of spaced apart compression springs.

Conveniently, the plurality of spaced apart compression springs are generally equally spaced apart along said respective seal plate. In one embodiment, each said at least one seal plate is slidably and sealably mounted between respective upper and lower guiding plates.

Conveniently, each seal wedge is further slidably and sealably mounted between respective upper and lower guiding plates of respective said seal plates of the section edges defining said corner. Typically, each seal wedge includes a main wedge plate being slidably mounted into and along a generally U-shape channel of each respective said seal plates of the section edges defining said corner, each said main wedge plate being mounted in generally sealing abutment contact with side walls of each said U-shape channel. Conveniently, each seal wedge further includes upper and lower wedge cams slidably mounted onto said main wedge plate with said main wedge plate located in sandwiched therebetween, each said upper and lower wedge cam being slidably and sealably mounted between respective adjacent said upper and lower guiding plates and said main wedge plate. Conveniently, each upper and lower seal wedge cam is in sealing abutment contact with a respective inner surface of each said adjacent corresponding upper and lower guiding plates.

Typically, each upper and lower seal wedge cam is biased in said sealing abutment contact by a respective compression coil spring relative to said main wedge plate a main wedge plate.

Conveniently, each seal wedge is biased towards the respective inner corner of the housing by a compression spring.

In one embodiment, the piston further includes a top seal to ensure seal contact with a top wall of the housing to prevent a pressure fluid leakage when the piston reached a maximum top position within the housing.

Conveniently, the top seal being positioned on said top wall along a perimeter thereof and adjacent said plurality of rectilinear section edges.

According to another aspect of the present invention, there is provided a piston for slidable and longitudinal displacement within a corresponding channel housing, said piston comprising a top seal to ensure seal contact with a top wall of the housing to prevent air (or pressure fluid) leakage when the piston reached a maximum top position within the housing.

Other objects and advantages of the present invention will become apparent from a careful reading of the detailed description provided herein, with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of the present invention will become better understood with reference to the description in association with the following Figures, in which similar references used in different Figures denote similar components, wherein: Figure 1 is a broken top perspective view of a non-rotating piston/weight slidable inside a corresponding housing in accordance with an embodiment of the present invention;

Figure 2 is a broken bottom perspective section view of the piston/weight of Figure 1 , showing the perimeter seal at the bottom of the piston;

Figure 3 is an enlarged broken section view taken along line 3 of Figure 2;

Figure 4 is a broken bottom perspective section view of a piston/weight of Figure 1 , showing the perimeter seal from the outside;

Figure 5 is an enlarged broken bottom perspective section view of a piston/weight of Figure 1 , showing the corner seal with the lower guide plates removed for clarity purposes;

Figure 6 is an enlarged top perspective view of a corner seal of the piston/weight of Figure 4;

Figure 7 is an enlarged broken top perspective section view of a piston/weight of Figure 1 , showing the top seal in seal contact with a top wall of the housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the annexed drawings, in most of which many parts have voluntarily been omitted for clarity purposes, the preferred embodiments of the present invention will be herein described for indicative purpose and by no means as of limitation.

Referring to Figure 1 , there is schematically shown an embodiment 10 of a non- rotating piston, or weight, slidably movable along a corresponding housing 12 in the form of a channel for displacement of the piston therealong. In the present case, the piston 10 is connected, and suspended, to a load (not shown) via cables 14 or the like. In this embodiment, the piston 10, being substantially heavy and weighting many tons (as its relative size to a human body H of an adult shown in Figure 1) is permanently forced downward into the housing 12 under gravity, and partially held back by the load/cables 14 that are not sufficient to stop and/or raise the piston 10. The piston 10 with the portion of the housing 12 located therebelow form a closed chamber 16. The fluid pressure, preferably gas such as simply air, inside the chamber is controllable via a valve system 18. In order to raise the piston 10, or maintain it a specific location within the housing 2, the chamber 16 is simply pressurized. Since the mass of the piston 10 is sized to be have a weight slightly larger than the load connected to the cables 14, a relatively low pressure, such as typically below about 10 psi (70 kPa), and preferably below about 4 psi (30 kPa), is required to raise the piston within the housing 12. Accordingly, the piston 10 is sealably mounted into the housing 12. As shown in Figures 1 to 2, the typical embodiment of a non-rotating piston 10 includes a body 20 having a polygonal section formed with a plurality of rectilinear section edges 22 defining corners 24 at the different intersections thereof. The body 20 defines a piston axis 26 that is locally coaxial with the housing axis 28. A seal assembly 30 is typically mounted on the body 20, in this case adjacent the piston longitudinal lower end, for operably interfacing with an inner wall 32 of the housing 12. The seal assembly 30 typically includes, along each section edge 22, at least one seal plate 34 biased radially outwardly, typically via at least one compression spring 36 or the like, towards the housing inner wall 32 in a direction generally perpendicular to the respective section edge 22, and at each corner 24, a seal wedge 38 slidably and sealably connected to the respective seal plates 34 of the section edges 22 defining the corner 24.

As better seen in Figure 3, each seal plate 34 is typically secured in the axial direction by upper and lower guiding rigid plates 42, 44, between which the seal plate 34 is slidably and sealably mounted. The seal plate 34 typically protrudes radially outwardly from the respective upper and lower plates 42, 44 and has a length generally slightly smaller than the length of the corresponding housing inner wall 32 it abuttingly interfaces with. The slightly smaller dimension is just enough to ensure that adjacent seal plates 34 do not get into contact with one another. Each coil spring 36 of the plurality of springs biasing a same seal plate 34 towards the corresponding housing inner wall 32 is held in compression against the seal plate by a respective spring back plate 46 mechanically secured to a spring housing block 48, itself secured to both upper and lower rigid plates 42, 44. Each spring 36 is then housed within a cylindrical through bore 49 extending through the housing block 48 and closed by the back plate 46. Referring now more specifically to Figures 4 through 6, each seal wedge 37 has a main wedge plate 38 that is slidably mounted into a corresponding U-shaped slot channel 50 extending along a slanted end of each one of the two adjacent seal plates 34, and in generally sealing abutment contact with the two side walls of each U-shaped channel 50. The main wedge plate 38 has its two longitudinal outer wedge surfaces 52 of the wedge outer end substantially coplanar with the respective outer surface 54 of the seal plates 34 so as to get in abutment contact interface with the two housing inner walls 32, at the intersection thereof. The main wedge plate 38 is terminated by an intermediate plate 56 at the wedge inner end and, similarly to the seal plates 34, is biased radially outwardly by a compression coil spring 58 or the like held in compression between the intermediate plate 56 and a corner spring back plate 60 secured to a corner spring housing block 62, itself secured to the upper and lower rigid plates 42, 44 of both adjacent seal plates 34. Upper and lower wedge cams 64, 66 of the seal wedge 37 are respectively slidably and sealably sandwiched between respective upper 42 and lower 44 rigid plate and the main wedge plate 38 to prevent the fluid entering into the space between the seal wedge and the corresponding seal plate 34, along the bottom side wall of the corresponding U-shaped channel 50 from escaping through the space between the two seal plates 34 adjacent the respective upper and lower rigid plates 42, 44. To prevent any fluid leak, each wedge cam 64, 66 is biased, typically by a respective compression coil spring 68, 70 or the like held in compression between the cam and the intermediate plate 56, against, and in sealing abutment contact with a preferably intermediate rear inner surface 72 of each of the two adjacent seal plates 34. Accordingly, the location of each abutment contact is obviously closer to the seal wedge axis than the respective space between the main wedge plate 38 and the U-shaped channel bottom side wall, namely the respective side wall of the main wedge plate 38. In order to ensure a proper guided displacement of the piston 10 within the housing, each piston body lateral wall 74 corresponding to a respective section edge 22 includes a guiding mechanism 76. The guiding mechanism 76, at each lateral wall 74, typically includes a plurality, preferably four rollers 78 or the like (one adjacent each wall corner) rotatably mounted on the lateral wall 74 adapted to roll along the corresponding housing inner wall 32 during axial displacement of the piston within the housing 12. To allow radial displacement or misalignment of the piston 10 within the housing 12, for each lateral wall 74 having rollers 78 protruding therefrom by a fixed distance, the generally opposite lateral wall 74 has the rollers 78 biased radially outwardly, using compression springs 79 or the like (see Figure 4), towards the corresponding housing inner wall 32 for a constantly adapting protrusion distance. At the same time, the seal plates 34, and the seal wedges 37, are also obviously constantly and continuously adapting to the lateral displacement of the piston 10 to maintain the proper seal along the entire length or perimeter of the piston/housing interface.

In operation, the non-rotating piston 10 of the present invention is typically heavy (many tons) and weighs slightly more than the weight of the object (or the load - not shown) it has to displace and/or raise, such as a large structure, and is connected thereto via a flexible link 14 such as a cable or the like. Because of the slight difference in weight between the piston 10 and the object, the fluid, preferably a gas such as compressed air or the like, pressure to apply below the piston 10 is relatively small due to the large surface area of the piston section. Such a fluid pressure inside the housing chamber 16 formed below the piston 10 is sufficient to partially escape between the piston seal plates 34 and seal wedges 37. The compression springs 36, 58 are properly selected to allow such a retraction of the corresponding plates 34 and wedges 37 sufficiently to provide an air cushion acting as a lubricant, all along the seal, for a smooth displacement of the piston 10 within the housing 12. By using relatively low fluid pressure, it is very easy to compensate for that predetermined fluid leakage and therefore accurately control the position of the piston 10 along the housing 12, and accurately maintain a selected position therealong within a precision of a few thousands of an inch, such as about a millimeter.

Referring now more specifically to Figures 1 and 7, the piston 10 typically includes a top seal 80 to ensure seal contact of the piston with a top wall 82 of the housing 12 to prevent air (or pressure fluid) leakage when the piston 10 reached a maximum top position within the housing 12, and could maintained in that position for some extended periods of time, thus limiting the amount of pressurized air in that position.

Although not specifically shown in the drawings, the housing (and the piston) could be inclined, rather than being vertical. Similarly, the housing could include curved portions (as long as the radius or curvature is large enough) and the flexible link kept under tension by the weight/piston would have some guides (such as pulleys or the like) to ensure that it does not come into contact with the housing inner walls during displacement of the piston along the housing. Although the present invention has been described with a certain degree of particularity, it is to be understood that the disclosure has been made by way of example only and that the present invention is not limited to the features of the embodiments described and illustrated herein, but includes all variations and modifications within the scope and spirit of the invention as hereinafter claimed.