Abstract:
A white cap dipper apparatus for metal fence posts and a method of dipping such posts, wherein the apparatus includes a shuttle car having a tilt frame for removing posts in successive groups from horizontal flow path cables, successively elevating such posts and dipping the same, and then returning the posts to the cables in horizontal position. The car reciprocates back and forth in the dipping zone in such timed relation to the flow path and with such speed that while it creates a gap in the flow path, it does not interrupt the continuity of the flow.

Description:
FIELD OF THE INVENTION 
     This invention relates to metal fence post dipping apparatus for while capping metal fence posts. 
     BACKGROUND OF THE INVENTION 
     In the manufacture of metal fence posts, it is common practice to perform a number of operations on posts or post stock with them in horizontal positions, including the operation of applying an overall paint job to the posts. However, the trade demands that the posts be white capped. To our knowledge this has been done by terminating the horizontal flow in advance of the white capping operation, then taking the posts, hanging them vertically, and passing them through a white dip bath. This is time-consuming and thus an expensive operation, and it does not lend itself to being integrated into horizontal flow path of the preceding operations. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the above problems by providing an apparatus which can be integrated into the flow of horizontal posts. Our apparatus is interposed in the flow and without interrupting the same, removes posts in successive groups or batches from the flow, dips the same, drips the same and returns them horizontally into the flow path in step with previously dipped posts. 
     It is a main object of the present invention to provide a dipper for performing the above operations and to provide a method of dipping, including steps for effecting the above results. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of a dipper incorporating the concepts of the present invention; 
     FIG. 2 is a plan view of the dipper, with the posts not being shown to reveal the construction of components of the dipper; 
     FIG. 3 is an elevational end view of the dipper; and 
     FIGS. 4-7 are schematic views showing the steps the dipper takes in performing the dipping operation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The dipper includes a wheeled shuttle car II (FIG.1) riding on rails or tracks 13 which are secured to a floor (such as provided by a concrete slab). The shuttle car is driven back and forth by a ball screw 15 which is journaled at one end in a bearing block 17 (FIG. 2), and threads through a ball nut 19 (FIGS. 1 and 2) on the car. The screw has an extension in the form of a shaft to be driven alternately by a motor 21 or a motor 23 (FIG. 2) mounted on a base B. The motors drive sheaves 25 and 27, respectively, which are carried by clutches 29 and 31, respectively, mounted on the shaft portion of the ball screw 15. There is also an electrical brake 32 connected to the extension of the ball screw. 
     The car is shown as comprising an open box-like framework including upper and lower longitudinal members 33 (FIGS. 1 and 2), upper and lower cross members 35, and uprights 37. 
     A tilt carrier 41 (FIGS. 2 and 3) for the posts is supported on the car by a pair of generally bell-crank shaped arms 43 (FIG. 3) which are secured at one set of ends to a heavy shaft 44. The shaft is journaled by bearings 45 (FIG. 2) on pads 46 secured to upper cross members 35 near the right side of the machine as the parts are depicted in FIG. 3. The opposite ends of the arms 43 support the tilt carrier 41. In the particular embodiment of the invention shown, the carrier is, in fact, in part formed by extensions 47 on the arms (FIG. 3). The extensions are connected by a pair of longitudinal connecting pieces 49. 
     The arms are actuated by a pair of double-acting air cylinders 51 (FIG. 3) anchored at the cylinder ends at 53 to the uppermost longitudinal member 33 and are pivotally connected at their piston rod ends at 55 to levers 57. The levers are secured at their upper ends to shaft 44. When the piston and cylinder units are contracted, the carrier 41 is elevated to the broken line position in FIG. 3, whereas when the piston and cylinder units are extended, the carrier is lowered to the solid line position shown in FIG. 3, resting on the uppermost longitudinal member 33. 
     The tilt carrier 41 includes a post carrying rack 61 (FIG. 3) in the form of an open framework which is supported on the tilt carrier by air springs or bags 63. These are stabilized by limited-motion guide devices 64 (FIG. 2). The rack 61 has a pair of parallel laterally spaced magnetic bars 65, whose upper surfaces are disposed at a level beneath that of a pair of conveyor cables 67 (FIG. 3) when the air springs are inactive, but above that of the cables (to pick up posts thereon) when the air springs 63 are actuated. The cables ride on the top surfaces of a pair of longitudinally extending cable support members 71. These members are supported by uprights 73 which are secured at their lower ends to the floor. 
     Disposed at one side of the shuttle car is a paint tank assembly including a longitudinally extending tank or trough 81. (FIGS. 2 and 3) which has a pair of brackets 83 (FIG.3) equipped with ball nuts 85 for receiving a pair of upright ball screws 87. The screws are journaled at their upper and lower ends in an open framework 89 which has a base portion 91 secured to the floor. A motor 93 (FIG. 2) is mounted on the framework 89 and has a flexible driving connection 95 with the nuts 85 so that when the motor operates in one direction, the tank 81 is elevated, and when operated in the opposite direction, the tank is lowered. 
     FIGS. 4-7 show the sequence of operations. It is pointed out that the scale of the drawing has been foreshortened for purposes of illustration, but the principle shown in FIGS. 4-7 is valid. The cables 67 are shown as conveying a number of posts P along from left to right. The posts can be considered as constituting a series of batches or groups, four of which are numbered 1, 2, 3 and 4 in FIGS. 4-7. The shuttle car 11 is shown only schematically, as is the post carrier 61 and the elevatable trough or tank 81. 
     In FIG. 4 it is assumed that the shuttle car and rack underlie post group 3, having just returned from right to left after depositing post group 2. First, the air springs 63 are activated to lift off the post group 3, whereupon the magnetic bars 65 are activated to releasably hold such posts onto the rack 61. The shuttle car is now driven to the left by motor 21, sheave 25, and clutch 29. The cylinders 51 are almost immediately contracted to swing the tilt carrier and its rack 61 from their horizontal positions to the broken line vertical position of FIG. 3, this being timed such that tank 81, in the process of being elevated by motor 93, rises beyond the lower ends of the posts as the parts are shown in FIG. 3 (and FIG. 5), to immerse or dip the lower end portions of the traveling posts in a paint bath contained within the tank. The tank is long enough to allow dipping of the traveling posts without physical interference between the tank and posts. 
     The immersion is brief and the tank immediately descends and the shuttle car continues moving to the right with the posts vertical to allow them to drip, for a desired period of time normally considerably in excess of the actual time of immersion. Then, shortly before the shuttle car reaches its right hand extreme position, the cylinders 51 are extended to swing carrier 41 and its rack downwardly to a horizontal position just above its final rest position. The carrier 41 now tracks the preceding group of posts, group 2, until a limit switch 101 (FIG. 2) on the tilt carrier 41 engages the nearest post of such group. When this occurs, brake 32 is actuated to stop the car and the magnet bars and air springs are inactivated to deposit post group 3 onto the cables 67 in proper spaced relation to group 2 so as to avoid a break in the continuity of the spacing of the posts being transported by the cables. 
     It is apparent from the above description that motor 21 drives the shuttle car from left to right at a rate exceeding that of the cables 67, to enable post group 3 to catch up with and track post group 2, and then to be deposited as recited above. 
     At start up in the morning, or in case the preceding post are inadvertently disarranged, the shuttle car will engage a limit switch 103 located on one of the tracks 13 (FIG. 1) to actuate brake 32, stop the car, and cause deposit of the transported group of posts onto the cables. 
     While post group 3 has been dipped and moved to the right, the posts remaining on the cables at the left hand side of the machine have been advancing as shown in FIGS. 5 and 6. After depositing post group 3 on cables 67, the shuttle car is rapidly driven in the reverse direction by motor 23, sheave 27 and clutch 31, until the car engages a limit switch 105 (FIG. 1) on one of the tracks 13 to actuate brake 32 to stop the travel of the shuttle car in a position to pick up post group 4. The movement effected by motor 23 is even substantially faster than that caused by motor 21, and sufficiently fast that car 11 arrives slightly ahead of time. Shortly thereafter, the leading post of group 4 engages a limit switch 107 (FIG. 2) on one of the cable support members. This initiates a succeeding cycle of operation like that previously described. The cycle of movement effected by motors 21 and 23 is such that the shuttle car can move back and forth picking up, dipping, depositing groups of posts and returning in such a time frame as to maintain the continuity of flow of the posts on cable 67 and without interrupting such flow. 
     For convenience in illustration, the tilt frame and rack are shown shorter than the shuttle car 11. Preferably they are longer and extend beyond the ends of the car. 
     A circuit diagram showing an arrangement for obtaining the above desired sequence of operation is unnecessary, because once the components are set forth and located and the sequences recited, such circuitry is well within the skill of those skilled in the art. Such a circuit is deemed incorporated herein by reference. 
     While we have shown and described a preferred embodiment of our invention, it will be apparent to those skilled in the art that changes and modifications may be made without departing from our invention in its broader aspects. We therefore intend the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.