Abstract:
A fluid-operated piston-type actuator includes a body having first and second axial ends and an inner surface that defines a bore that opens through at least one of the first and second axial ends to define an open end of the bore. A piston is slidably positioned in the bore. An end wall is positioned in blocking relation with the open end of the bore. The end wall comprises a peripheral surface that defines a first circumferentially extending groove that is axially aligned with a second circumferentially extending groove defined in the inner surface of the body when the end wall is positioned in blocking relation with the open end of the bore. The end wall further comprises an inner face oriented toward the piston and an opposite outer face oriented away from the piston. The first groove is located axially between the inner and outer faces. The outer face covers and blocks access to a majority of the first groove and comprises a first notch defined therein that intersects and provides access to the first groove. A retaining band is located partially in both the first and second grooves. The retaining band is resiliently expanded radially into abutment with an outer wall of the second groove. An end wall and a method of connecting same to a body of a fluid cylinder are also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from and hereby expressly incorporates by reference U.S. provisional application No. 60/301,350 filed Jun. 27, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to fluid operated piston type actuators. More particularly, the present invention relates to an improved end wall structure and method of fabricating an improved end wall structure for a fluid-operated piston-type actuator, as well as to a fluid operated piston type actuator including the improved end wall structure. 
     Fluid-operated piston-type actuators are well-known and in widespread use. Depending upon their particular structure, these actuators incorporate at least one and often two removable end walls for sealing the open end(s) of a bore defined in the actuator body. The end walls sealingly engage the wall of the actuator body defining the bore to prevent fluid from escaping the bore between the end wall and the actuator body. Typically, a piston rod extends through one of the end walls and is slidable relative thereto. Here, again, one or more seals are employed to prevent fluid from escaping the bore between the rod and the end wall. 
     Conventional end walls and arrangements for operably locating same in a fluid-operated piston-type actuator have been found to be sub-optimal for a variety of reasons. Many end walls are expensive and/or time-consuming to manufacture. Others render the actuator more difficult and expensive to assemble. Still others do not present a smooth, uninterrupted surface that can be tapped or otherwise used to anchor related components. Also, end walls that include large open cavities in their outer faces are undesirable in many application owing to the fact that dirt and other debris can collect in these cavities and the retaining band is exposed. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the present development, a fluid-operated piston-type actuator comprises a body having first and second axial ends and an inner surface that defines a bore that opens through at least one of said first and second axial ends to define an open end of the bore. A piston is slidably positioned in the bore. An end wall is positioned in blocking relation with the open end of the bore. The end wall comprises a peripheral surface that defines a first circumferentially extending groove that is axially aligned with a second circumferentially extending groove defined in the inner surface of the body when the end wall is positioned in blocking relation with the open end of the bore. The end wall further comprises an inner face oriented toward the piston and an opposite outer face oriented away from the piston. The first groove is located axially between the inner and outer faces. The outer face covers and blocks access to a majority of the first groove and comprises a first notch defined therein that intersects and provides access to the first groove. A retaining band is located partially in both the first and second grooves. The retaining band is resiliently expanded radially into abutment with an outermost wall of the second groove. 
     In accordance with another aspect of the present development, a method of connecting an end wall to a body of a fluid cylinder comprises placing an end wall inside an open mouth of a bore defined in a body of a fluid cylinder and adjusting an axial position of the end wall in the bore so that a first groove that is defined in a peripheral surface of the end wall is aligned with a second groove that is defined in the body. A first end of a retaining band is fed in a first direction into the first groove through a notch defined in an outer face of said end wall. The end wall is rotated in a second direction that is generally opposite the first direction so that the retaining band is received in the first and second grooves. 
     In accordance with another aspect of the present development, an end wall for a fluid cylinder comprises a peripheral cylindrical surface that defines a first circumferentially extending groove adapted to be aligned with a second circumferentially extending groove defined in an inner surface of an associated body when the end wall is positioned in blocking relation with an open end of the bore. The end wall further comprises an inner face and an outer face oriented away from the inner face. The first groove is located axially between the inner and outer faces and the outer face covers and blocking access to a majority of the first groove. A first notch is defined in the outer face and intersects and provides access to said first groove. 
     One advantage of the present invention resides in the provision of a novel and unobvious end wall for a fluid-operated piston-type actuator, a fluid-operated piston-type actuator including same, and a method of assembling a fluid-operated piston-type actuator. 
     Another advantage of the present invention is found in the provision of a novel and unobvious method for manufacturing an end wall for a fluid-operated piston-type actuator, and an end wall made according to the method. 
     Still another advantage of the present invention resides in the provision of an end wall for a fluid-operated piston-type actuator wherein an outer face of the end wall is primarily smooth and uninterrupted, e.g., planar. 
     A further advantage of the present invention is that it provides a cost-effective method for fabricating an end wall for a fluid operated piston type actuator. 
     A yet further advantage of the present invention resides in the provision of a fluid-operated piston-type actuator having an end wall secured to a body thereof by a metal band, wherein a majority of the band, when operably positioned, is inaccessibly located behind an outer face of the end wall. 
     Still other benefits and advantages of the present invention will become apparent to those of ordinary skill in the art to which the invention pertains upon reading this specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention comprises a variety of components and arrangements of components, and a variety of steps and arrangements of steps, preferred embodiments of which are illustrated in the accompanying drawings that form part hereof wherein: 
     FIG. 1 is a top plan view of a fluid-operated piston-type actuator constructed in accordance with the present invention and including an end wall formed in accordance with the present invention; 
     FIG. 2 is a sectional view taken along line  2 — 2  of FIG. 1; 
     FIG. 3 is a partial perspective view of the fluid-operated piston-type actuator of FIG. 1, with the preformed retaining band being operably positioned; 
     FIG. 4 is similar to FIG. 3 but shows the preformed retaining band only partially inserted into or removed from its operative position; 
     FIG. 5A is a top plan view of raw bar stock from which an end wall in accordance with the present invention is fabricated according to a novel and unobvious method; 
     FIG. 5B is a side elevational view of the raw bar stock shown in FIG. 5A; 
     FIG. 6 is a top plan view of an end wall formed in accordance with one embodiment of the present invention; and, 
     FIG. 7 is a sectional view taken along line  7 — 7  of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, FIGS. 1 and 2 illustrate a fluid-operated piston-type actuator constructed in accordance with the present invention. The actuator comprises a body  10  having an inner surface  12  that defines a cylindrical bore  14 . In the illustrated embodiment, the bore  14  is a through-bore that extends between and through opposite first and second axial ends  16 ,  18  of the body  10 . In an alternative embodiment, the bore  14  is a blind bore open at only one of the ends  16 ,  18 . One or more ports  20  are defined in the body and provide fluid communication with the bore  14 . 
     A piston  30  is closely received in the bore  14  and is adapted for reciprocal axial sliding movement between the first and second ends  16 ,  18  of the body  10 . Movement and positioning of the piston  30  is controlled by fluid pressure on its opposite faces as varied by fluid introduced into or exhausted from the bore  14  through the one or more ports  20 . As is generally well-known, the piston  30  is sealingly engaged to the inner surface  12  by one or more seals  32  that prevent or at least substantially inhibit fluid flow between the piston  30  and the inner surface  12  while still allowing for axial sliding movement of the piston as described. A rod  34  is connected to the piston  30  and projects outwardly therefrom. The rod  34  includes an outermost end  36  adapted to be connected to an associated member to be moved in response to axial movement of the piston/rod assembly  30 / 34 . 
     The bore  14  at the first end  16  of the body  10  is closed by a first end wall  40  formed in accordance with the present invention. The first end wall  40 , also illustrated separately in FIGS. 6 and 7, defines an outer face  42 , an inner face  44  and a peripheral surface  46 . The outer and inner faces  42 ,  44  preferably comprise planar surfaces while the peripheral surface  46  preferably comprises a cylindrical surface. The first end wall  40  is dimensioned and conformed for close, sliding receipt in the first end  16  of the bore  14 . The peripheral surface  46  of the end wall  40  defines a first circumferential groove  50  that, when the end wall  40  is operably positioned in the end  16  of the bore  14  as shown in FIG. 2, is adapted to align axially with a circumferential groove  52  defined in the inner surface  12  defining the bore  14 . 
     The grooves  50 , 52  together are adapted for receipt of a retaining band  56  (see also FIG. 4) that is preferably manufactured from a one-piece polymeric or metallic band member preformed into a circular or helical shape. An innermost wall  54  defines the groove  50  to have a first depth, while an outermost wall  58  defines the groove  52  to have a second depth. 
     The band  56 , as shown in an partially installed and relaxed condition in FIG. 4, is resilient and defines a maximum width W that is smaller than the combined depth D (FIG. 2) of the grooves  50 , 52 . Furthermore, the band  56  defines a relaxed maximum outer diameter OD 1  that is greater than a diameter OD 2  (FIG. 2) of the circumferential groove  52 . Thus, when the band  56  is operatively installed as shown in FIG. 2, it is radially compressed by the outermost wall  58  of the groove  52  so that its maximum outer diameter OD 1  is reduced and made equal to the diameter OD 2 . 
     Consequently, when installed in its operative position, the band  56  is in resilient compressed abutment with the outermost wall  58  of the groove  52  and a circumferentially extending gap S is defined between the band  56  and the innermost wall  54  of the first groove  50 . When the band  56  is operatively installed as shown in FIG. 2, it is partially located in each of the grooves  50 , 52 , and axial movement of the end wall  40  in the bore  14  is prevented by the presence of the band  56 . The space S facilitates installation of the band  56  by providing a temporary space into which the band can move temporarily during its installation. The presence of the space S allows for the first groove  50  to be substantially enclosed behind the outer face  42  of the end wall  40  without excessive binding of the band  56  in the first groove  50  during installation of the band  56 . A result of this arrangement is that the band  56  is not seated against the innermost surface  54  of the first groove  50  when operatively installed as is readily apparent from the drawings. 
     In one preferred embodiment, the band  56  is metallic and has a width W of 0.131 inches and the grooves  50 , 52  have a combined depth of 0.210 inches so that the space S is 0.079 inches. It is most preferred that the space S be at least 0.05 inches. Also, it is most preferred that the groove  50 , taken alone, also define a minimum depth of that is at least approximately 0.010 inches greater than the width W of the band  56  to allow sufficient clearance for the band during installation. Of course, these dimensions can vary without departing from the overall scope and intent of the present invention. Also, each groove  50 , 52  has a axial length sufficient to accommodate the band  56  when the band is operatively installed and compressed a maximum amount axially as shown in FIG.  2 . Generally, when the band  56  is operatively installed, it describes at least a full circle, i.e., 360° and can describe a helix having multiple turns, e.g., a helix that passes through 1080°. In any case, when axially compressed as shown in FIG. 2, the band  56  defines an axial length equal to the stacked height of its turns, and the grooves  50 , 52  are dimensioned to have a slightly greater axial length to accommodate the band. 
     The end wall  40  defines at least one and preferably two peripheral notches  60 , 62  that preferably open in both the outer face  42  and the peripheral surface  46 . The notches  60 , 62  are preferably located at diametrically opposed locations on the periphery of the end wall  40  and each intersects and communicates with the first groove  50 . Therefore, those of ordinary skill in the art will recognize that, when the end wall  40  is operably located in the first end  16  of the bore  14 , the notches  60 , 62  provide a location for feeding the retaining band  56  into (and for withdrawing the retaining band from) the aligned grooves  50 , 52 . The notches  60 ,  62  are also conformed and located to receive two projections of an associated tool (not shown) that is used to rotate the end wall  40  as needed during band installation as described below. A seal retaining peripheral groove  64  is also defined in the peripheral surface  46  of the end wall  40 . The groove  64  is adapted for operative receipt of an O-ring or other seal  66  that sealingly engages the surface  46  of the end wall  40  to the inner surface  12  of the housing  10  to prevent fluid passage between the end wall  40  and the inner surface  12 . 
     With reference now particularly to FIGS. 5A-7, a preferred method for manufacturing the end wall  40  is illustrated. An axial length of raw bar stock  70  is provided with or machined to have a circular cross-section. As shown in FIG. 5B, the stock  70  has a first planar face  72 , and second planar face  74  and a cylindrical peripheral face  76 . The surface  76  of the stock  70  is machined using conventional machinery to define the peripheral surface  46  of the end wall  40  including the first peripheral groove  50  and the seal-retaining groove  64  as shown in FIGS. 6 and 7. Also, if desired or necessary, the face  72  of the stock is machined to define the outer face  42  of the end wall  40 . The peripheral notches  60 , 62  are machined into the face  42  and peripheral surface  46  as described above. Furthermore, if necessary or desired, the face  74  of the stock  70  is machined to define the inner face  44  of the end wall  40 . Those or ordinary skill in the art will recognize that the machining involved is minimal as compared to conventional end wall structures. 
     Referring again to FIGS. 1 and 2, an end wall  140  is operably secured in the second end  18  of the bore  14 . Except and shown and described herein, the end wall  140  is identical to the end wall  40 . Thus, like features of the end wall  140  relative to the end wall  40  are identified using reference numbers that are one-hundred (100) greater than those used to identify features of the end wall  40 , and further repetition of these like features is not necessary or provided. New features are identified with new reference numerals and are described below. 
     The inner surface  12  that defines the bore  14  in the actuator body  10  defines a circumferential groove  152  that is identical to the groove  52  defined by the inner surface  12  at the first end  16  of the bore  14 . When the end wall  140  is operably located in the second end  18  of the bore  14 , the grooves  150 ,  152  are axially aligned with each other so that the retaining band  56  can be used to axially fix the end wall  140  in the bore  14  as described above in relation to the end wall  40 . 
     Unlike the end wall  40 , the end wall  140  defines a central opening  180  in which the piston rod  34  is slidably positioned. Thus, the piston rod  34  projects through the opening  180  in the end wall  140  and is axially movable relative to the end wall  140  in response to axial movement of the piston  30 . The opening  180  is defined to include a first stepped area  182  that receives an annular seal  184 . The seal prevents or at least inhibits fluid flow between the rod  34  and the end wall  140 . The opening  180  is also defined with a region  186  adapted to receive an annular bushing and/or seal  188 . 
     With reference now to FIGS. 3 and 4, installation of the end wall  140  into the second end  18  of the bore  14  is explained. The procedure in identical for operative installation of the end wall  40  into the first end  16  of the bore  14 . 
     As shown in FIG. 4, a first end  56   a  of the retaining band  56  is inserted into the aligned grooves  150 ,  152  through one of the notches  160 ,  162 . The band  56  is preferably fed into the grooves as far as possible, typically until the first end  56   a  travels circumferentially through the grooves for approximately 360°. After that, assuming the entire band  56  has not been inserted to the grooves  150 ,  152  (i.e., assuming that the band  56  describes more than a simple circle), the end wall  140  is rotated in a direction Al opposite the direction in which the band  56  has been fed into the grooves  150 ,  152 . Continued rotation of the end wall  140  in the direction A 1  results in the entire band  56  being fed into the grooves  150 ,  152 . Preferably, rotation of the end wall  140  is stopped when a second end  56   b  of the band  56  is located in one of the notches  160 ,  162  as shown in FIG.  3 . Most preferably, the second end  56   b  of the band  56  defines an upturned tail  56   c  that is inclined at an angle of, e.g., 30°, and that can be pulled using pliers or the like to facilitate removal of the band  56  according to a procedure that is a reverse of the foregoing installation procedure. During installation of the band  56 , the upturned tail  56   c  that is located in one of the notches  160 ,  162  is manually flattened and moved radially outwardly so that it is held substantially flat in the groove  52  as shown in FIG.  1 . When the band  56  is to be removed, the portion of the tail  56   c  that is visible in the notch  160 ,  162  is pulled radially inwardly (using e.g., a screwdriver or other blade) so that the tail is pulled from the groove  52  and resiliently springs and returns to its upturned state where it is easily accessible to pliers or a like tool. Because the notches  160 ,  162  are relatively small compared to the entire area of the outer surface  142 , the upturned tail  56   c  is important in that it allows for use of pliers or a like tool for grasping and puling the band  56  in the confined space of the notches  160 ,  162  during removal of the band. Furthermore, as noted, the tail  56   c  is selectively movable into the groove  52  to flatten the tail selectively after installation of the band  56  to minimize tampering, damage and the like. 
     As shown in FIG. 3, a main advantage of the present invention is that, when the band  56  is fully installed, the band is visible and exposed only at the notches  160 ,  162  (notches  60 , 62  of the end wall  40 ). A great majority of the band  56  is protected and inaccessible. It is preferred that at least 75% of the first groove  50 ,  150  be covered and rendered inaccessible behind the outer face  42 ,  142 , respectively. As such, a corresponding percentage of the band  56  is protected and unexposed when operatively installed. Stated another way, it is most preferred that the notches  60 , 62 , taken together, expose no more than 25% of the circumference of a band  56  held in the groove  50 . Similarly, it is preferred that the notches  160 ,  162 , taken together, expose no more than 25% of the circumference of a band  56  installed in the groove  150 . This limited size of the notches  160 ,  162  limits the space for accumulation of debris. In spite of the fact that the grooves  50 , 52  of the end wall  40  and the grooves  150 ,  152  of the end wall  140  are primarily enclosed behind the respective faces  42 ,  142 , installation of the band  56  in these grooves is not difficult owing to the presence of the space S described above. As noted, the space S temporarily accommodates the band  56  as required during its installation. 
     In an alternative embodiment, when the retaining band  56  is operatively installed, a tail portion  56   c  of the retaining band can remain outside of the grooves  50 , 52  and/or  150 ,  152  and extend from the notches  60 ,  62  and/or  160 ,  162 . In this case, at a minimum, the portion of the retaining band  56  actually located in the grooves  50 , 52  and/or  150 ,  152  is formed in accordance with the present invention. Thus, the appended claims are intended to encompass this alternative arrangement insofar and the claim limitations are satisfied by the portion of the band  56  actually located in the grooves  50 , 52  and/or  150 ,  152 . 
     The invention has been described with reference to preferred embodiments. Modifications may occur to those of ordinary skill in the art, and it is intended that the invention be construed as including all such modifications and alterations.