Abstract:
A preferred embodiment of a fluid powered apparatus has a housing, a piston and an off-axis member to deter piston rod rotation relative to the housing. In a further aspect of the present invention, an off-center pin actuates one or more sensors while also deterring rotation of a piston rod relative to a housing. An additional aspect of the present invention provides for complete retention and sealing of a sensor within a housing.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention relates generally to fluid powered devices and more particularly to a fluid powered, part locator. 
     It is known to employ automatically powered locating pins which are moved from retracted positions to advanced positions to engage and locate workpiece parts on an assembly line or checking station. For example, one conventional pin part locator employs a pneumatically driven piston, having an oval peripheral shape, which advances and retracts an elongated piston rod connected to a tapered workpiece locating pin. However, the tolerances and accuracy of the piston rod and locator pin relative to the body are poor and can vary by as much as plus or minus one-half degree from the desired centerline. This type of inaccuracy is even further accentuated when employed to locate or orient sheet metal panels on an automotive vehicle assembly line when a small tolerance mismatch at the bottom of the vehicle may accumulate to a considerable tolerance stack-up at the vehicle&#39;s roof. 
     It is also known to use proximity switches with pneumatically powered industrial devices such as pin part locators, powered clamps and robotic grippers. For example, reference should be made to U.S. Pat. No. 5,190,334 entitled “Powered Clamp with Parallel Jaws” which issued to Sawdon on Mar. 2, 1993, and U.S. Pat. No. 5,871,250 entitled “Sealed Straight Line Gripper” which also issued to Sawdon on Feb. 16, 1999; these patents are incorporated by reference herein. It is noteworthy, however, that the proximity switches are mounted in optional fluid ports and protrude externally from the devices, thereby requiring additional assembly line clearance. 
     In accordance with the present invention, a preferred embodiment of a fluid powered apparatus has a housing, a piston and an off-axis member to deter piston rod rotation relative to the housing. In another aspect of the present invention, the member is a finger extending between the piston rod and the piston. In a further aspect of the present invention, the member is an off-center pin aligning the piston and the housing. Still another aspect of the present invention employs an off-center pin projecting from both opposed faces of the piston for removably projecting into opposed holes in the housing on either side of a fluid chamber. In yet a further aspect of the present invention, an off-center pin actuates one or more sensors while also deterring rotation of a piston rod relative to a housing. An additional aspect of the present invention provides for complete retention and sealing of a sensor within a housing. 
     The apparatus of the present invention is advantageous over conventional devices in that the present invention is significantly more compact and precise. When used with a pin part locator, the compactness allows for reduced component dimensions and closer proximity of the actuating components to the workpiece; this increases precise repeatability and improves tolerance stack-ups within the apparatus. The compactness is enhanced by the multiple functionality of the off-center pin and sensor packaging. Furthermore, the tolerance stack-ups within the apparatus are improved by the multiple anti-rotation features employed as well as positive seating of the piston rod and piston relative to the housing. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view showing the preferred embodiment of a pin part locator of the present invention; 
     FIG. 2 is a perspective view showing the preferred embodiment pin part locator; 
     FIG. 3 is an exploded perspective view showing the preferred embodiment pin part locator; 
     FIG. 4 is a cross sectional view, taken along line  4 — 4  of FIG. 6, showing the preferred embodiment pin part locator; 
     FIG. 5 is a cross sectional view, taken along line  5 — 5  of FIG. 4, showing the preferred embodiment pin part locator disposed in a retracted position; 
     FIG. 6 is a cross sectional view, like that of FIG. 5, showing the preferred embodiment pin part locator disposed in an advanced position; 
     FIG. 7 is a fragmentary cross sectional view, taken along line  7 — 7  of FIG. 4, showing the preferred embodiment pin part locator disposed in a retracted position; 
     FIG. 8 is a side elevational view showing a body employed with the preferred embodiment pin part locator; 
     FIG. 9 is a cross sectional view, taken along line  9 — 9  of FIG. 8, showing the body of the preferred embodiment pin part locator; 
     FIG. 10 is a side elevational view showing an end cap employed with the preferred embodiment pin part locator; 
     FIG. 11 is a cross sectional view, taken along line  11 — 11  of FIG. 10, showing the end cap of the preferred embodiment pin part locator; 
     FIG. 12 is a perspective view showing an off-center pin employed with the preferred embodiment pin part locator; 
     FIG. 13 is a side elevational view showing the off-center pin of the preferred embodiment pin part locator; and 
     FIG. 14 is a perspective view showing a seal employed with the preferred embodiment pin part locator. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment of a pin part locator  21  is shown in FIGS. 1 and 2. Pin part locator  21  includes a housing  23 , a piston rod  25  and a part locator pin  27 . Housing  23  further consists of a body  29  and an end cap  31 . Body  29  is attached to a bracket  33  secured to a work table, manufacturing plant floor or robot. Multiple bolts secure bracket  33  to holes  35  and dowels serve to orient and prevent rotation of bracket  33  relative to holes  37 . It should be appreciated that the rectangular body configuration allows for mounting of pin part locator  21  along any of the external body surfaces such as  39 ,  41 ,  43 ,  45  or the like. Piston rod  25  can be retracted and extended in order to protrude through a pair of openings  42  in multiple sheet metal panels or workpieces  44  and  46 . This serves to align these panels about a common gauging point. The arcuately tapered and somewhat conical shape of locating pin  27 , enhances entry through the panel openings when the piston rod and locator pin are advanced. Locator pin  27  is secured to a distal end of the piston rod by way of roll pins  47  or the like. 
     Referring to FIGS. 3-7, body  29  includes an internal fluid chamber  51 , a longitudinally elongated bore  53  and fluid ports  55  and  57 . A piston  59  is movably located within fluid chamber  51  and piston rod  25  is movably positioned in bore  53 . Piston  59  may be moved in a first direction  60  toward workpiece  44  or in a second direction  62  away from workpiece  44 . Piston  59  has a pair of opposed and generally flat faces  61  and  63  which are acted upon by the fluid pressure flowing from either port  55  or port  57 . Piston  59  further has an oval peripheral shape which is sealed against the oval shaped internal wall of body  29  defining fluid chamber  51 . A pair of V-shaped seals  65  are employed. 
     A cap screw  67  centrally fastens piston  59  to piston rod  25 . Furthermore, a circular-cylindrically shaped finger  69  is machined as an integral part of piston rod  25 . Finger  69  protrudes from a proximal end of piston rod  25  and engages in a corresponding circular hole  71  of piston  59 . Finger  69  is transversely offset from a longitudinal centerline  73  of piston  59  and piston rod  25 . Thus, finger  69  and fastener  67  act to significantly deter rotation between piston rod  25  and piston  59 . Additionally, the oval shape of piston  59  and the internal body wall defining fluid chamber  51  serve to significantly deter rotation between piston  59  and body  29 . 
     An off-center pin  81  is also attached to piston  59 . This can best be observed in FIGS. 4,  7 ,  12  and  13 . Off-center pin  81  has a threaded central segment  83  bordered by a pair of generally cylindrical segments  85  and  87 . Frusto-conical leading end segments  89  and  91  are also provided. A pair of opposed wrench receiving flats  93  are employed on one of the cylindrical segments  87 . Threaded segment  83  is secured within an internally threaded passage of piston  59 . A Locktite brand adhesive is then used to further secure off-center pin  81  to piston  59 . Cylindrical segments  85  and  87  project from the opposing faces of piston  59  and are oriented with an elongated centerline generally parallel to longitudinal piston centerline  73 , but transversely offset therefrom. 
     Segment  87  is receivable within an elongated hole  101  (FIG. 7) of body  29  when piston  59  is located in its advanced position, as shown in FIG.  6 . This engagement of off-center pin  81  with hole  101  serves the multiple functions of ensuring the accurate positioning of the workpiece locator relative to the body while also actuating a proximity switch sensor  103 . Similarly, retracted positioning of piston  59 , as shown in FIG. 7, causes off-center pin  81  to enter an opposite hole  105  in end cap  31 . This also serves to actuate a second proximity switch sensor  105 . 
     Accordingly, Applicant respectfully requests withdrawal of the objections to the specification. 
     FIGS. 7-11 illustrate the switch pocket configurations. A switch pocket  111  is machined within body  29  in an elongated direction generally perpendicular to piston centerline  73 . Switch pocket  111  has a generally rectangular shape with rounded edges. A rounded opening  113  is also drilled through and past switch pocket  111  to intersect hole  101 . This allows communication between switch pocket  111  and fluid chamber  51 . Proximity switch  103  entirely fits within pocket  111  such that it is completely disposed below the adjacent nominal exterior surface of body  29 . A molded rubber proximity head seal  121 , with a generally oval peripheral shape, is located in an undercut area of switch pocket  111 . Thus, proximity switch  103  is sealed within switch pocket  111  to prevent fluid from flowing therepast. Proximity switch can preferably be obtained from the Turck Inc. 
     A similar switch pocket  123  and seal  125  arrangement is provided on end plate  31  for retaining proximity switch  105  and for interfacing with the corresponding segment of off-center pin  81 . A dc or ac status controller switch block  127 , which can also be obtained from Turck Inc., is bolted to a generally flat, cold rolled sheet metal plate  129  which, in turn, is fastened to the corresponding external surface of body  29  by screws  131 . Status controller switch block  127  contains display lights and the appropriate input/output electrical connectors. A depressed channel  141  is machined in body  29  and end cap  31 . This can be observed in FIGS. 3 and 10. These channels provide for passage of wires  143  to connect proximity switches  103  and  105  with status controller switch  127  (see FIG.  7 ). Plate  129  also serves to completely cover and protect proximity switches  103  and  105  as well as wires  143  in channels  141 . 
     Referring again to FIGS. 3-6, a wiper ring  151  and cup seal  153  act in combination with body  29  to provide an enlarged multiple point seat to accurately contact against and position piston rod  25 . An O-ring  155  also is used to seal end cap  31  to body  29 . A pair of roll pins  157  and four screws  159  secure end cap  31  to body  29 . Off-center pin  81  is made of  4150  heat treated steel, piston rod  25  is machined from  6150  chrome-plated steel, while piston  59 , end cap  31  and body  29  are all machined from 6061-T651 aluminum stock. The body is further hard coated to provide a hard and durable bearing, so as to eliminate the need for additional inserted bearings. 
     The pin part locator of the present invention achieves enhanced precision of the piston rod and attached workpiece interface, relative to the desired centerline and housing by way of the offset finger, off-center pin and oval shaped piston. The internal mounting of the proximity switches further enhances compactness of the pin part locator thereby achieving easy packaging and mounting on a busy assembly line and also close spacing of the actuator portion of the locator, such as the piston, relative to the workpiece interfacing portion. The compact design may be machined to interface with other existing pin part locators by simply increasing the body size to suit the mounting area needed. The compact design can offer a flange mount, front face mount, side mount and center key mount. Moreover, the stroke may vary by changing only the rod length, the body length and switch cover; all other components remain standard. 
     While the preferred embodiment of the pin part locator has been disclosed, it should be appreciated that various other modifications may be made without departing from the present invention. For example, the workpiece interface may be a gripper arm or cam actuated clamp coupled to the piston rod. Furthermore, the body may alternately have a cylindrical shape. While pneumatic fluid is preferred, hydraulic fluid can be employed. Additionally, other piston location sensors can be used in place of proximity switches. It is also envisioned that the finger may project from the piston for engaging in an aperture located in the piston rod. While various materials, shapes and manufacturing processes have been disclosed, it will be appreciated that others can be also employed. It is intended by the following claims to cover these and any other departures from the disclosed embodiments which fall within the true spirit of this invention.