Abstract:
A shaft bushing for an actuator cylinder includes a removeable, non-cylindrical lined sleeve bearing configured to a flat sided shaft. Interlocking inserts are captured in windows in the outer bushing wall. These engage flat outer sides of the bearing and keep it and the shaft from rotating. A shaft wiper secures the sleeve bearing but is removable for replacement of the bearing.

Description:
[0001]    This invention relates to shaft bushings for actuator cylinders and more specifically to bushings for preventing shaft rotation in pneumatic, hydraulic and electric actuator cylinders.  
           [0002]    In the past, front end shaft bushings for actuator cylinders have been manufactured using, in part, a broaching operation to form a shaft bore conforming to the cross-section of a flat-sided reciprocating shaft in order to keep the shaft from rotating. This broaching process typically added time and cost to the manufacturing operation. Also, the front end of such cylinders through which the shaft extended in the bushing typically had no shaft bearing. Actuator reliability and bushing life were limited.  
           [0003]    Accordingly, it has been one objective of this invention to provide an improved, anti-rotate shaft bushing for an actuator cylinder.  
           [0004]    Another objective of the invention has been to provide an improved method of replacing wear parts in an actuator shaft bushing.  
           [0005]    Another objective of the invention has been to improve the reliability of an actuator shaft bushing.  
         SUMMARY OF THE INVENTION  
         [0006]    To these ends, a bushing according to a preferred embodiment of the invention comprises an elongated bushing member, an elongated, non-cylindrical shaft bearing sleeve, two synthetic inserts captured in respective windows in the bushing member and having flat inner sides engaging flat outer sides of the bearing sleeve, and a wiper removeably securing the bearing sleeve within the bushing sleeve. Since the bearing sleeve cannot rotate in the bushing sleeve due to the interference of the captured inserts, and since the non-cylindrical inner bore of the bearing sleeve conforms to the flat-sided actuator shaft, that shaft is held against rotation by the bushing. The bearing sleeve is easily formed of thin gauge metal with a synthetic bearing liner, for example, rendering any broaching operation unnecessary, while retaining the anti-rotating feature for shaft control and while providing a sliding, wear resistant bearing for the shaft.  
           [0007]    When tolerances enlarge, due to wear, for example, the wiper can be removed from the bushing, the bearing sleeve pulled out and replaced, along with insert replacement if needed, without requiring an entire new bushing or shaft. The wiper, or a new one, is replaced, securing the bearing sleeve in the bushing.  
           [0008]    This new bushing provides significant cost, manufacturing, operating life and reliability to actuator cylinders, and is easily refitted when worn. Reliability and maintainability are improved, and manufacturing costs reduced.  
           [0009]    These and other advantages will become readily apparent from the following detailed written description and from the drawings in which:  
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a side view in partial cross-section of an assembled bushing according to the invention;  
         [0011]    [0011]FIG. 1A is an end view of FIG. 1;  
         [0012]    [0012]FIG. 2 is a side view in partial cross-section of the elongated bushing member of FIG. 1;  
         [0013]    [0013]FIG. 2A is an end view of FIG. 2;  
         [0014]    [0014]FIG. 3 is a side view of a shaft bearing;  
         [0015]    [0015]FIG. 3A is an end view of the shaft bearing of FIG. 3;  
         [0016]    [0016]FIG. 4 is a side view of an insert;  
         [0017]    [0017]FIG. 4A is an end view of two inserts as they reside in a bushing according to the invention;  
         [0018]    [0018]FIG. 5 is a side view of a shaft wiper;  
         [0019]    [0019]FIG. 5A is an end view of the wiper of FIG. 5;  
         [0020]    [0020]FIG. 6 is a side view of the shaft bearing of FIG. 3;  
         [0021]    [0021]FIG. 6A is an end view of the apparatus of FIG. 6; and  
         [0022]    [0022]FIG. 7 is a cross-sectional view taken along lines  7 - 7  of FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    Turning now to the drawings, there is shown therein an improved bushing  10  for supporting a reciprocating shaft and preventing rotation thereof. The bushing  10  can be used effectively in conjunction with shafts, such as a flat sided shaft  11  (FIG. 1) of a pneumatic, hydraulic or electric actuator cylinder. Shaft  11  has a longitudinal axis  11   a.    
         [0024]    Bushing  10  has a particularly useful application where the shaft  11  has two opposed flat sides  12  (one not shown) and two opposed rounded sides  13 ,  14 .  
         [0025]    As shown in the respective Figs., bushing  10  comprises a plurality of parts including an elongated cylindrical bushing wall or member  16  having external cylindrical wall surface  17  and cylindrical internal wall surface  18  (FIG. 12). Opposed windows  19  and  20  are defined in the bushing wall  16  as shown. At one end of bushing wall  16  is a radially outwardly projecting flange  22  having seal grooves  23 ,  24  therein for receiving O-ring seals to seal the bushing  10  within an actuator cylinder (not shown) for example. Set screw bores  25 ,  26  are provided in flange  22  to secure the bushing  10  in place in such a cylinder. Bushing  10  further includes a radially outwardly projecting flange  28  at the other end of member  16 . A radial groove  66  is disposed in the flange  28 , as will be described, and it terminates at a lower side with a sealing shoulder  67 .  
         [0026]    The assembled bushing  10  also has the following elements: a lined, non-cylindrical shaft sleeve bearing  30  (FIG. 3); two inserts  32 ,  34 ; and a shaft wiper and bearing retainer  36 .  
         [0027]    The lined, non-cylindrical shaft sleeve bearing  30  is preferably formed of a suitable metal and is lined with a liner  31  of preferably synthetic, wear-resistant material such as polytetrofluoroethylene or any other wear resistant surface on which a shaft  11  can slide. Liner  31  is applied by any suitable method. Bearing  30  has a radially outwardly extending flange  41  at one end thereof, interior flat sides  75 ,  76  and exterior flat sides  77  and  78 .  
         [0028]    Inserts  32 ,  34  are also made, preferably of a shear resistant synthetic material of any suitable type. Each insert has an elongated intermediate portion  43  and rounded portions  44 ,  45  with extending thin ends  46 ,  47 . Inserts  32 ,  34  each have an inwardly facing flat face surface  48 ,  49 , and each has two parallel grooves  50  proximate each end extending across the rounded surfaces  44 ,  45 .  
         [0029]    Shaft wiper  36  also functions as a bearing retainer as will be described. The wiper  36  is received within groove  66  after sleeve  30  is inserted, thereby securing the sleeve bearing  30  in the bushing  10 . Alternately, the wiper could be screwed or otherwise fastened onto the end of bushing  10 .  
         [0030]    Wiper  36  has an internal opening  37  defined by two opposed flat sides  61 ,  62  and two opposed rounded sides  63 ,  64  for accommodating a shaft  11  and wiping it clean as it reciprocates therein. An upward shaft wiper projection  68  of the wiper  36  extends away from the bushing while a flat under surface  38  sealingly engages surface  67  in bushing  10  at flange  28 , and the upper end of the flange  41  of the shaft sleeve bearing  30 .  
         [0031]    Assembly of the entire bushing  10  is accomplished by inserting inserts  32 ,  34  into windows  19 ,  20  from inside the cylindrical bore formed by wall surface  18 . Ends  46 ,  47  extend along interior walls  18  while rounded portions  44 ,  45  extend into the windows  19 ,  20  in the wall  16 . Grooves  50  of the inserts align with grooves  72 ,  73  and provide transverse passages for bolts or screws mounting any yoke or other bushing or actuator structure on the bushing  10 .  
         [0032]    After insertion of the inserts  32 ,  34 , the non-cylindrical sleeve bearing  30  is inserted into the bore defined by interior surfaces  18  of wall  16 , with the flat sides  77 ,  78  of the bearing  30  aligned with the flat surfaces  48 ,  49  (FIG. 4A) of the inserts  32 ,  34 . The inserts are captured in the windows  19 ,  20  with ends  46 ,  47  disposed between the wall  18  just externally of the flat side  77 ,  78  of bearing  30  (FIG. 7).  
         [0033]    In this manner, it will be appreciated that the flat exterior sides  77 ,  78  of the non-cylindrical sleeve bearing  30  are engaged by the inserts  32 ,  34 . Since the inserts are captured, however, in the discrete windows  19 ,  20 , they block any rotational movement of the bearing  30 , such as about a shaft axis  11   a.    
         [0034]    Thereafter, the wiper  36  is secured within groove  66  and this holds the sleeve bearing  30  in place against longitudinal movement.  
         [0035]    The assembled bushing  10  is then positioned over a shaft  11  and slid into position to be secured at one end of an actuator, or is secured thereto, awaiting introduction of a shaft  11 . The flat sides  12  of the shaft  11  align with the flat surfaces  75 ,  76  of non-cylindrical sleeve bearing  30  which slidably supports the shaft  11 , but maintains it against rotation about axis  11   a.    
         [0036]    Accordingly, it will be appreciated that the bushing  10  can be more inexpensively and quickly made than in the past; broaching to accommodate the shaft cross-section is not necessary. Moreover, any wear is accommodated by removal of bushing  10  and replacing only the lined, non-cylindrical bearing sleeve  30 , and perhaps the inserts  32 ,  34 , so the entire bushing is inexpensively refitted without an entirely new bushing being required. Since the shaft is harder than the bearing liner  31 , the shaft life is extended.  
         [0037]    These and other advantages and modifications will be readily apparent to those of ordinary skill in the art without departing from the scope of the invention and applicant intends to be bound only by the claims appended hereto.