Abstract:
A piston assembly is provided. The piston assembly may include: a piston rod; a piston pivotally connected to the piston rod; and a rotatable rod bearing configured to allow the piston rod to pass therethough and rotate along with the piston rod as the piston rod pivots with respect to the piston. A method of making a piston assembly may be provided. The method may include: attaching a piston rod to a piston in a pivoting connection; providing a rotatable bearing for the piston rod; and supporting the piston rod with the rotatable bearing.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to hydraulic cylinders. More particularly, the present invention relates to a self aligning cylinder piston and rod bearing contained within a hydraulic cylinder. 
       BACKGROUND OF THE INVENTION 
       [0002]    Hydraulic cylinders (sometimes referred to as rams, jacks or linear actuators) are typically designed with basic components of: a cylinder body, end caps, seals, piston, piston rod and rod bearing. The rod bearing as well as the piston itself act to support any eccentric loading that the cylinder assembly may encounter during use. This eccentric loading, also referred to as side loading, can get quite large. If not properly supported the side loading may result in damage of internal parts of the cylinder. 
         [0003]    The rod bearing and piston are typically in fixed alignment with the longitudinal axis of the cylinder, and as side loading is applied, the reaction points of the contact between the piston rod and the rod bearing, as well as the piston to the cylinder walls become concentrated into a point of contact. This reduces the bearing area of the reaction points and the increased stress can easily exceed the load resistance of the cylinder or rod and bearing material. This may cause material to be stressed beyond the yield limits, causing material to be displaced. Galling typically results, which may potentially damage the cylinder. 
         [0004]    Accordingly, it is desirable to provide a method and/or apparatus that can perform the functions of a piston and cylinder where forces placed on the piston and/or piston rod may not be exactly parallel to the axis of the piston rod, and distribute the load forces over larger bearing areas. Such a self aligning piston, piston rod, cylinder and rod bearing may be useful. 
       SUMMARY OF THE INVENTION 
       [0005]    The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments a method and apparatus that provides a self aligning cylinder piston and rod bearing that allows the piston rod to actuate the cylinder when forces acting upon the rod are not exactly parallel to axis of the piston rod without causing the piston rod to move out of alignment within the cylinder. By allowing self aligning rod and piston bearings, more bearing contact area between mating surfaces is achieved, thereby reducing concentrated stress loading. 
         [0006]    In accordance with one embodiment of the present invention, a piston assembly is provided. The piston assembly may include: a piston rod; a piston pivotally connected to the piston rod; and a rotatable rod bearing configured to allow the piston rod to pass therethough and rotate along with the piston rod as the piston rod pivots with respect to the piston. 
         [0007]    In accordance with another embodiment of the present invention, a method of making a piston assembly may be provided. The method may include: attaching a piston rod to a piston in a pivoting connection; providing a rotatable bearing for the piston rod; and supporting the piston rod with the rotatable bearing. 
         [0008]    In accordance with yet another embodiment of the present invention, a piston assembly may be provided. The piston assembly may include: means for pushing a piston; a piston pivotally connected to the means for pushing a piston; and a rotatable bearing means configured to allow the means for pushing a piston to pass therethough and rotate along with the means for pushing a piston as the means for pushing a piston pivots with respect to the piston. 
         [0009]    There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
         [0010]    In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
         [0011]    As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a side view of a hydraulic cylinder and piston rod in accordance with an embodiment of the invention. 
           [0013]      FIG. 2  is cross-sectional view of a hydraulic cylinder and piston rod according to related art. 
           [0014]      FIG. 3  is an enlarged cross-sectional partial view of a hydraulic cylinder and piston rod according to the related art. 
           [0015]      FIG. 4  is an enlarged partial cross-sectional view of a hydraulic cylinder and piston rod in accordance with an embodiment of the invention. 
           [0016]      FIG. 5  is a cross-sectional perspective view of a portion of a hydraulic cylinder and piston and piston rod in accordance with an embodiment of the invention. 
           [0017]      FIG. 6  is a partial perspective cross-sectional view of a hydraulic cylinder and piston rod in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. An embodiment in accordance with the present invention provides a hydraulic cylinder, piston, and piston rod that is able to withstand forces on the piston rod that are not directly parallel with the axis of the piston rod. 
         [0019]      FIG. 1  illustrates a hydraulic cylinder  10 . The hydraulic cylinder  10  shown in  FIG. 1  can be, according to the present invention, or it could also be according to related art as the internal structures hydraulic cylinder  10  are not shown. The hydraulic cylinder  10  includes a cylinder housing  12  a piston rod  14  and hydraulic inlet/outlet  16  and a hydraulic inlet/outlet  18 . 
         [0020]    The hydraulic inlets/outlets  16  and  18  are inlets or outlets of hydraulic fluid depending on whether the piston rod  14  is moving inward into the cylinder housing  12  or outward of the cylinder housing  12 . For example, when the piston rod  14  is moving inward towards the cylinder housing  12  feature  18  is acting as an inlet for hydraulic fluid into the hydraulic cylinder  10  whereas feature  16  is working as an outlet of hydraulic fluid out of the hydraulic cylinder  10 . When the hydraulic fluid is pumped into the feature  16  and the feature  16  acts as an inlet, the hydraulic fluid will push upon the piston (not shown in  FIG. 1 ) connected to the piston rod  14  thereby forcing the piston rod  14  out of the cylinder housing  12 . Hydraulic fluid will flow out of the hydraulic cylinder housing  12  through feature  18  which is such case will act as an outlet. 
         [0021]    For a variety of reasons, such as, off center loading, tolerances, warping of parts, parts manufactured out of specification or a variety of other reasons, the forces acting on the piston rod  14  may not be parallel to an axis of the hydraulic piston rod  14 . Arrow  20  illustrates an exaggerated, example force that may act on the piston rod  14 . The piston rod  14  may be connected to a variety of mechanical equipment or other features that are moved when the piston rod  14  moves. The reaction force from this equipment is approximated as a vector and illustrated by arrow  20  in  FIG. 1 . As can be seen, the force illustrated by vector  20  has a vertical component  22 . As shown in  FIG. 2 , the vertical component  22  acts as a force acting downwardly on the piston rod  14 . 
         [0022]      FIG. 2  is a cross-sectional view of hydraulic cylinder  10 . The hydraulic cylinder  10  may include an inlet/outlet  16  and  18  and internal bore  24  within the cylinder housing  12 . Set within the internal bore  24  is a piston  26 . The piston  26  is attached to the piston rod  14 . The piston rod  14  is supported in part by the piston  26  and a rod bearing  28 . The vertical force component  22  may generate reactionary force components illustrated as force arrows  30  and  32  in  FIGS. 2 and 3 . 
         [0023]      FIG. 3  is an enlarge partial cross-sectional view of the cylinder housing  12  containing the piston  26  and piston rod  14  located within internal bore  24 . Inlet/outlet  18  is also shown. The reactionary force arrows  30  and  32  indicate where reactionary forces may be generated to keep the piston rod  14 , piston  26  located within the internal bore  24 . These reactionary forces  30  and  32  may urge against the wall  34  of the internal bore  24 , the piston rod  14 , the piston  26  and the rod bearing  28  creating wear points  36  and  38 . 
         [0024]    As the hydraulic piston  26  and piston rod  14  continue to move in and out of the cylinder housing  12 , the wear points  36  and  38  may subject to galling or other types of the undesirable wear along the piston rod  14 , the internal bore  24 , the piston  26  and/or the bearing  28 . In order to avoid or minimize the situation, different types of pistons  40  and rod bearings  60  may be used as shown and described with respect to  FIGS. 4 ,  5 , and  6 . 
         [0025]    For example, as shown in  FIGS. 4 and 5 , a piston  40  may be a two part piston  40  and include a front part  42  and rear part  44 . The front part  42  and the rear part  44  may define a socket cavity  46 . Socket cavity  46  may be generally round or spherical in shape. 
         [0026]    Fasteners  48  may attach the front part  42  to the rear part  44  which together comprise the piston  40 . The front part  42  and the rear part  44  may include a fastener bore  50  which allow the fasteners  48  to attach the front part  42  and the rear part  44 . A ball  52  may be used to connect the piston rod  14  to the piston  40 . The ball  52  is attached to a shaft  54 . The shaft  54  is located in the bore  56  of the piston rod  14 . The shaft  54  may attach to the bore  56  via threads  58  as shown in  FIGS. 4 and 5 . 
         [0027]    However in some embodiments of the invention, other attaching means besides the threads may be used. For example, press fitting, welding or any other suitable way of attaching the ball  52  to the piston rod  14  may be used. The ball  52  is free to move within the socket cavity  46  defined by the front part  42  and rear part  44  of the piston  40 , thus enabling the piston rod  14  to pivot with respect to the piston  14  as illustrated by arrow  68 . 
         [0028]    A rotatable bearing  60  is also used and is able to rotate in order assist or aid in the piston rod  14  pivoting with respect to the piston  40 without creating undue wear or galling within the cylinder housing  12  or piston rod  14 . The rotatable rod bearing  60  includes a rounded external surface  62 . The rotatable rod bearing  60  is contained within a rounded socket  64  within the cylinder housing  12 . The rounded surface  62  of the rotatable rod bearing  60  is able to rotate due to the rounded socket  64  in which the rotatable rod bearing  60  is located as illustrated by arrow  66  (see  FIG. 4 ). Thus, the moving or pivoting motions of both the piston rod  14  and the rotatable rod bearing  60  allow the rod bearing  14  to be in a position not exactly square with respect to the piston  40 . 
         [0029]    However, one of ordinary skill in the art will appreciate after reviewing the disclosure that as the piston rod  14  travels into the cylinder housing  12  it will self align and become more and more square with respect to the piston  40 . However, the piston rod  14  moves out of the cylinder housing  12 , it can move more and more out of square with respect to the piston  40 . The rotatable rod bearing  60  may be equipped with an “O” ring  67  set with a “O” ring groove  69  in order to seal the internal bore  24  with respect to having conditions of hydraulic cylinder  10 . 
         [0030]      FIG. 6  illustrates a hydraulic cylinder  10  in accordance with another embodiment of the invention. A partial view of the cylinder housing  12  is illustrated in cross-section along with the inlet/outlet  16 . Piston rod  14  is located within the internal bore  24 . 
         [0031]    The piston rod  14  is terminated with a rounded surface  70  on the rod  14 . The rounded surface  70  butts against with a corresponding rounded surface  72  on the piston  74 . The corresponding rounded surface  70  on the rod  14  and the rounded surface  72  on the piston  74  permit the piston rod  14  to pivot or move with respect to the piston  14  is shown in accordance with the invention and is shown in  FIG. 6 . 
         [0032]    The piston rod  14  may have “O” ring groove  76  and “O” rings  78  contained within them to provide a seal for the area in which the fastener  80  is contained within a fastener hole  82 . 
         [0033]    The fastener  80  may attach to the piston rod  14  via threads  84  in the fastener hole  82  and on fastener  80 . A single fastener  80  along with a resilient washer  86  will permit some movement of the piston rod  14  with respect to the piston  74 . The resilient washer  86  may flex when the piston rod  14  moves or pivots with respect to the piston  74 . 
         [0034]    The embodiment shown in  FIG. 6  may also use a rotatable rod bearing  60  like that shown in  FIGS. 4 and 5 . Because the pivotal rod bearing  60  used in the embodiment shown in  FIG. 6  is similar or identical to those shown  FIGS. 4 and 5 , the rotatable rod bearing  60  will not be shown further described with respect to  FIG. 6 . 
         [0035]    The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.