Abstract:
A fastener machine is provided. In another aspect, a rivet machine employs a rivet feeding mechanism. A further aspect includes a guide located at an intersection between a feed track and a feed rail with the guide having an angular offset orientation relative to both in order to deter ricocheting of the rivet back into the feed track when the rivet enters the feed rail. Moreover, an aspect of the present machine employs a rocker arm.

Description:
BACKGROUND AND SUMMARY 
       [0001]    This present invention relates generally to a fastener machine and more particularly to a feeding mechanism for a rivet machine. 
         [0002]    Various feeding and setting machines have been used for rivets. Such traditional machines are disclosed in U.S. Pat. Nos. 6,592,015 entitled “Feeding Heads for Fastening Machines” which issued to Gostylla et al. on Jul. 15, 2003, and U.S. Pat. No. 5,752,305 entitled “Self-Piercing Riveting Method and Apparatus” which issued to Cotterill et al. on May 19, 1998. Both of these patents are incorporated by reference herein. 
         [0003]    Another conventional, self-piercing rivet setting machine employs a right angled, T-shaped intersection between a guide track and feed rail paths. This causes a pneumatically driven rivet to undesirably bounce back or ricochet off of the abutting wall of the feed rail (e.g., the top of the T) thereby either jamming the feeding mechanism or being out of position for the subsequent advancement of a pusher shaft. Furthermore, this conventional device employs two linearly moveable plungers, one of which is in the guide track path (e.g., stem of the T) and the other of which is in the trailing branch of the feed rail path. These plungers are hollow and each have a height generally the same as the width. Each plunger is depressed against a compression spring until the plunger directly contacts against a conical face of a set screw. The quick advancing movement of the rivet past each plunger causes each plunger to downwardly move at about 30 feet per second which prematurely fatigues the spring after a number of cycles. Moreover, the air pressure can disadvantageously push the rivet past the plunger in the feed rail prior to advancement of the pusher shaft. 
         [0004]    In accordance with the present invention, a fastener machine is provided. In another aspect, a rivet machine employs a rivet feeding mechanism. A further aspect includes a guide located at an intersection between a feed track and a feed rail with the guide having an angular offset orientation relative to both in order to deter ricocheting of the rivet back into the feed track when the rivet enters the feed rail. Moreover, an aspect of the present machine employs a rocker arm pivotable adjacent a feed rail with a finger of the rocker arm being moveable through a hole in a channel to selectively limit movement of the rivet in the channel. In another aspect, a biased plunger has: a longitudinally longer aspect ratio relative to its nominal width to deter misalignment or cocking during movement of the plunger, a stop surface abutting a flange of the plunger to deter fatigue of a biasing member, and/or a beveled hole edge to deter tripping of the rivet when the rivet moves past the hole. Yet another aspect of the rivet machine provides at least a return sensor, an advancing sensor, a rivet feed sensor and a controller. A method of using a rivet machine is additionally provided. 
         [0005]    Further advantageous and areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view showing a rivet machine; 
           [0007]      FIG. 2  is a perspective view showing a feeding mechanism employed in the rivet machine; 
           [0008]      FIG. 3  is a fragmentary perspective view, with a cover removed, showing the feeding mechanism; 
           [0009]      FIGS. 4-6  are a series of elevational views, with the cover removed, showing operation of the feeding mechanism; 
           [0010]      FIGS. 7-9  are a series of diagrammatic views showing the operation of a rocker arm employed in the feeding mechanism; 
           [0011]      FIG. 10  is a cross-sectional view, taking along line  10 - 10  of  FIG. 4 , showing a plunger assembly employed in the feeding mechanism; 
           [0012]      FIG. 11  is an enlarged cross-sectional view, like that of  FIG. 10 , showing the plunger assembly; and 
           [0013]      FIG. 12  is a perspective view showing sensors employed in the feeding mechanism. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring to  FIG. 1 , a rivet setting machine  21  includes a C-frame  23  which is mounted to an articulated robotic arm  25  for automated movement between various operating positions within an industrial factory. An anvil section  27  of C-frame  23  has a die  29  mounted thereon. A ram assembly  31  is mounted to the opposite end of C-frame  23  and includes an air-over-oil fluid actuated cylinder  33 , a nose piece  35  and a linearly moving ram  37 . Alternately, cylinder  33  can be solely hydraulically, pneumatically, or less preferably, servo-motor actuated. A rivet feeding mechanism  41  is mounted to a generally middle segment of C-frame  23  and is elongated in a direction generally perpendicular to the movement direction of ram  37 . 
         [0015]    A vibratory bowl  43  supplies individualized fasteners, such as a self-piercing rivet  45 , to feeding mechanism  41  via a pneumatically pressurized and flexible hose  47 . When multiple workpiece sheets  49  are inserted between ram  37  and die  29 , ram  37  will thereafter push and set the rivet into the upper surface of the workpieces as they are being compressed against die  29 . Self-piercing rivet  45  is preferably a solid (e.g., not hollow) rivet which punches out a blank or slug from the previously unpunched workpiece areas, whereafter the blanks are withdrawn through an aperture in die  29 . The rivet ends are generally flush with the adjacent outside surfaces of workpieces  49 . One such self-piercing rivet is disclosed in U.S. Pat. No. 4,130,922 entitled “Headless Riveting System” which issued to Koett on Dec. 26, 1978, which is incorporated by reference herein. 
         [0016]      FIGS. 2-6  show further details of feeding mechanism  41 . Feeding mechanism  41  includes a curved guide track  61  within a rigid body  63 , and a linearly elongated channel  65  within a rigid feed rail  67 . A removeable cover  69  is bolted onto body  63  and an oppositely mounting gib  71 . Various bolts  73  and dowl pins  75  secure and align cover  69  to body  63 . Hose  47  is connected to one end of feed track  61 . 
         [0017]    A guide  81  is located at an intersection of feed track  61  and feed channel  65 , but is angularly offset relative to adjacent sections of both. An angle α between the direction of guide  81  and an elongation direction  83  of feed channel  65  is between 110° and 160°, and more preferably about 120°. This offset configuration deters ricochet or bounce back of rivet  45  when it initially enters feed channel  65  and contacts a back wall  85  thereof. A plunger  87  further urges rivet  45  toward an intermediate and temporary holding position (as shown in  FIG. 4 ) while also deterring movement of rivet  45  back into feed track  61 . 
         [0018]    Feeding mechanism additionally includes a pusher shaft  91 , a tie rod  93  rotatably pinned to shaft  91 , a piston rod  95  coupled to tie rod  93 , and a pneumatic fluid actuator cylinder  97  which operably advances and retracts pusher shaft  91 . Cylinder  97  and body  63  are affixed to a rigid frame  99 . 
         [0019]    With reference to  FIGS. 3 ,  8 ,  10  and  11 , an elongated hole  101  is positioned in a bottom surface  103  of guide  81 . A nominal section of plunger  87  is moveably positioned within hole  101  such that a rounded or frusto-conical distal end  105  thereof projects beyond bottom surface  103  when the plunger is fully extended. The plunger is preferably a solid part. A laterally enlarged and circular flange  107  is located at a proximal end of plunger  87 . It is noteworthy that a longitudinal distance from the proximal to distal ends are at least two and more preferably at least three times greater than the diameter width of the nominal section of plunger  87 . This aspect ratio helps to align plunger  87  within hole  101  thereby preventing undesired cocking or jamming of the plunger during operation. A compression spring  109  fits within a bore  111  in a retainer block  113  fastened to a bottom of feed rail  67  by bolts  115  and dowl pins  117 . An intermediate countersink  119  is provided between hole  101  and bore  111  such that abuttment surfaces  121  and  123  contact against the facing surfaces of flange  107  to limit the longitudinal movement of plunger  87 . This serves to prevent overcompression and premature fatigue of spring  109 . Feed rail  67  is mounted to body  63  by a spring loaded pin  80 . 
         [0020]    Additionally, a beveled edge  131  is machined at an intersection between hole  101  and bottom surface  103 . Such a bevel annularly extends around the periphery of the intersection and preferably has an angle β of 15° to 30° relative to bottom surface  103 , and more preferably 30°, but may alternately be rounded. This bevel edge deters tripping or jamming of the rivet when it depresses plunger  87  as it rides over hole  101  in response to the feeding pneumatic pressure. Land is present laterally adjacent hole  101  on bottom surface  103  so as to provide supporting ledges for the rivet. 
         [0021]    FIGS.  3  and  7 - 9 , best illustrate a further rivet positioning device of the present feeding mechanism. A rocker arm  161  includes an upwardly projecting finger  163  at a first end and an upwardly projection foot  165  at an opposite end thereof. A fulcrum  167  is positioned in a generally middle section projecting oppositely from finger  163  and foot  165 . Fulcrum  167  has a somewhat triangular side view shape, the rounded apex of which is received within a valley  169  of a podium upstanding from retainer block  113 . A cavity  171  is present between facing surfaces of retainer block  113  and channel  65  of feed rail  67 . 
         [0022]    An elongated slot or hole  181  is accessible by cavity  171  and extends through a bottom surface of channel  65  and laterally bordered by supporting ledges. Thus, when rocker arm  161  is pivoted to a rivet holding position as shown in  FIG. 7 , finger  163  protrudes through hole  181  so as to deter undesired advancement of rivet  45  therepast. In this condition, a nominal underside surface  183  of shaft  91  abuts against foot  165 , via hole  185 , to maintain the rocker arm  161  in the position shown in  FIG. 7  with finger  163  extending into a blocking position in channel  65 . 
         [0023]    When shaft  91  is advanced to an intermediate position, as shown in  FIG. 8 , foot  165  of rocker arm  161  is upwardly rotated into a relief gap  191  in rod  91  such that rivet  45  downwardly depresses finger  163  in a detented manner as rivet  45  passes over hole  181 . An intersecting edge of hole  181  adjacent the bottom surface of channel  65  is beveled like that illustrated in  FIG. 11 . Subsequently,  FIG. 9  shows rivet  45  advanced to a setting ram-engagement position beyond feed rail  67  and with rocker arm  161  downwardly rotated. Alternately, a pivot pin and/or biasing spring can be used to move the rocker arm, however, such an alternate configuration may not be as cost effective as with the preferred embodiment. 
         [0024]    Pushing shaft  91  is preferably machined from AMPCO  18  bronze. This material prevents magnetization of shaft  91  which would otherwise occur if steel. Magnetization would undesireably prevent the shaft from releasing the rivet. Furthermore, plunger  87  and rocker are machined from 6150 steel which is heat treated, hardened and ground to RC 60-63 and RC 50-54, respectively. The feed rail, retaining block and body are machined from M2 steel, which is heat treated, hardened and ground to RC 60-63. 
         [0025]    Turning now to  FIGS. 1 and 12 , multiple sensors are connected to a programmable controller  201 , preferably a computer, including non-transient memory such as RAM, ROM, a hard disc drive, removeable memory or the like. A microprocessor uses this stored software and received data to interface with input and output devices such as a keyboard, display screen, warning lights or the like. Programmed software instructions are stored in the memory for receiving sensor signals and making the necessary calculations and determinations as to whether the rivet machine is operating properly and whether an error signal needs to be output. 
         [0026]    More particularly, a first sensor is a no-rivet proximity switch  203  which detects if no rivet is present when cylinder  97  actuates the pusher shaft. A second sensor is an in-position proximity switch  205  which detects whether the pusher shaft has fully advanced the rivet. A third sensor is a return proximity switch  207  which detects whether the pusher shaft has fully retracted. A rod  209  extending from a back side of the piston and moveable with the pusher shaft, includes a forward/return flag  211  and a missing rivet flag  213 . Flag  211  is sensed by switches  205  and  207  while flag  213  is sensed by switch  203 . Switches  203 ,  205  and  207  are preferably photo-electric sensors such as model BGL 20A-001-S49 which can be obtained from Balluff Inc. 
         [0027]    Furthermore, proximity sensors  231  and  233  are positioned adjacent entrance and exit ends of feed tube  47 . The tube sensors are preferably of a ring proximity switch type that are connected to controller  201  and used to determine if a rivet has entered and exited tube  47 . Tube sensors  231  and  233  send appropriate signals to controller  201  which determines if a rivet has been properly fed through the tube, and prevents multiple rivets from being fed during the same feed cycle in the feeding mechanism to prevent rivet jamming therein. Accordingly, controller  201  will send an error message to an output device if a misfeed has occurred. 
         [0028]    The control logic is as follows. Before a rivet is sent to the rivet insertion unit from the bowl feeder, the pusher shaft is in its retracted position which is indicated by the return position photo-electric sensor being activated. Subsequently, when the bowl feeder receives a signal to send a rivet from the controller software, the bowl feeder blows a single rivet through the hose whereby the rivet passes through the first ring sensor which inductively senses the passage of the rivet therethrough and communicates with the software that the bowl feeder actually sent a rivet as so instructed by the software. If no rivet passes through the first ring sensor in a predetermined amount of time, then the controller software will indicate a fault or error that the bowl feeder failed to send a rivet. An operator then must clear this fault before the system will further cycle. 
         [0029]    Next, the rivet will pass the second ring sensor at the opposite end of the tube. When the second ring sensor is activated and sends the appropriate signal to the controller software, then the software will cause a cessation of pneumatic pressure into the hose. But if no rivet passes the second inductive ring sensor within a predetermined period of time, the controller software will indicate a fault that the rivet is stuck in the hose. In this event, the operator must clear the fault before the system will cycle. 
         [0030]    Furthermore, after the second sensor has indicated that the rivet has travelled through the hose and is in the rivet staging area, the controller software sends a signal to feed a rivet to the nose piece in the ram assembly. In this event, the controller software causes the actuator cylinder to advance the pusher shaft. The pusher shaft accordingly advances until the rivet is pushed into the setting ram-engaging position aligned between the ram and die. The rivet advance-return flag activates the advance photo-electric sensor for a predetermined amount of time (preferably 0.1-0.2 seconds) to ensure that it is in the final position. Once the advance photo-electric sensor has been activated, the pusher shaft is then caused to return by reverse actuation of the cylinder. If no rivet is present then the missing rivet flag activates the associated no-rivet photo-electric sensor and the controller software signals that a fault is caused by the rivets being stuck in the feeding track. Action must be taken to clear this fault before the system will continue to cycle. Moreover, if the pusher shaft is activated and no sensor is activated then there is a rivet jam between the pusher shaft and feed rail which must be cleared before cycle resumption. 
         [0031]    While various constructions have been disclosed, other modifications may be made. For example, alternate fasteners can be set by the machine although many of the benefits of the present machine will not be achieved. Furthermore, different types of sensors can alternately be employed but certain advantages may not be realized. Such variations are not to be regarded as a departure from the present invention and all such modifications are intended to fall within the scope of the present invention.