Abstract:
A method and apparatus is disclosed for simultaneously bending a length of handrail channel stock and handrail cap stock in an iron bender with a main frame and a swing frame, which comprises the steps of fitting the channel stock, with a length of flat stock inserted between its flanges, into the recessed underside of the cap stock, and bending the resultant assembly in a bender fitted with appropriately grooved back block, forming die and drawing block.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of edge bending metal stock. More particularly, this invention relates to the field of dies used in bending machines, and a method of simultaneously bending a piece of handrail cap stock and a piece of handrail channel stock. 
     2. Description of the Prior Art 
     In the installation of stair railings, several components are utilized: a length of channel stock is located 3 or 4 inches above the floor, a length of molded handrail cap stock is located approximately 3 feet above the floor, and plurality of spokes are mounted vertically between the handrail and the bottom channel approximately 4 or 5 inches apart from each other. Both the handrail and the bottom channel are parallel with the floor or stairway incline, and must be bent in a return bend to follow a winding stairway down or up. 
     Formerly, the lengths of cap stock and channel stock had to be bent in separate operations in a bending machine utilizing a radius block and in which the stock had to be continuously fed through the apparatus to achieve the desired curvature. The problems experience with &#34;feed through&#34; type production bending are that the bending process is slow, and that, since the amount of feed is regulated by the operator, the degree and trueness of the arc of curvature varies from piece to piece and operator to operator. These problems are magnified in the situation where two pieces, the channel piece and the handrail cap piece, must be mated in the final stair railing. 
     Methods and apparatus for &#34;single pull&#34; edge bending of flat stock without distortion or structural damage to the stock have been developed. Such systems utilize a stationary die to block movement of one end of the stock, called a back block, a die with a circular arc of predetermined radius around which the stock is to be bent, called a forming die, and a die to engage the stock along its unblocked portion and bend it around the forming die, called a drawing block. The drawing block is generally supported in an assembly which swings around the forming die by a roller block which rolls along the back surface of the drawing block. Once the stock has been placed between the forming die and drawing block, with one end blocked by the back block, the drawing block can be swung around the forming die in a single pull to achieve a bend of anywhere between 0° and approximately 180°. Such apparatus can be adapted to bend single pieces of stock having a fairly uniform cross section across their width, such as flat stock, or handrail cap stock, with no distortion. But twisting or distortion cannot be avoided if a piece of stock not having a generally uniform cross section across its width, such as the channel stock with its web and two flanges, is bent in such a bending operation. Thus, in order to shape the pieces of stock used to assemble a stair railing utilizing the previously known methods, the handrail cap stock can be bent in a single pull operation, but the bottom channel has to be bent in a separate operation. The problem of non-matching mate pieces remained unsolved until the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention solves the problems inherent in the prior art by providing a special set of dies and a unique method for simultaneously bending two pieces of mated stock to the desired curvature in a single pull operation. 
     The dies are designed to bend both pieces together by grooving the portions of the dies that will come in contact with the working pieces to conform with the general outline of those working pieces. The handrail cap stock is molded and has a recess in its underside which is equal in width to the width of the channel stock; by placing a length of cap stock on top of a length of channel stock, which is fitted into the recessed underside of the cap, a convenient unit capable of being simultaneously bent is formed. The grooves in the die faces have a cross section substantially conforming to the right or left half of the cross section of the cap/channel unit. 
     The dies are mounted in the bender so that the grooved face of the forming die faces toward the grooves in the back and drawing blocks; the opposed grooves then form a recess which substantially conforms in cross section to the cross section of the cap/channel unit. Before the cap/channel unit, a length of flat stock equal in width to the distance between the flanges of the channel stock is placed between those flanges to act as a spacer and to prevent them from deforming while the cap/channel unit is being edge bent. The cap/channel unit with insert in place is then bent to the desired curvature in the bender, after which the insert may be discarded. 
     Thus, the invention saves time and money by allowing two pieces to be bent in one operation with only one set of dies, resulting in two identically curved pieces that can be matched with each other in the assembly of a stair railing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view in perspective of an edge bending machine showing the dies of the present invention and a length of handrail/channel/flat stock mounted therein; 
     FIG. 2 is a top plan view of the edge bending machine of FIG. 1 with portions thereof broken away, showing the swing frame in the fully open position; 
     FIG. 3 is an end elevation taken generally along the line 3--3 of FIG. 2; 
     FIG. 4 is a view in perspective of the back block of the present invention; 
     FIG.5 is a view in perspective of the forming die of the present invention; 
     FIG. 6 is a view in perspective of the drawing block of the present invention; 
     FIG. 7 is a view in perspective of the flat stock spacer of the present invention; 
     FIG. 8 is an end elevation of a portion of FIG. 3, showing the recess formed by the opposed grooves of the die pieces of the present invention; 
     FIG. 9 is an end elevation of a piece of handrail cap stock; and 
     FIG. 10 is an end elevation of a piece of channel stock. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 discloses an iron bender 10 having a stationary main frame 11 and a swing frame 12 hingedly connected thereto by center pin 13. A flat surface roller block 14 is releasably mounted in swing frame 12 at a predetermined radial distance from center pin 13. 
     A forming die 15 is mounted on center pin 13. The forming die 15, which is more fully disclosed in FIG. 5, includes a generally semi-circular portion 16, a horn portion 17 extending generally tangentially from semi-circular portion 16, and a first side portion 18 extending along the periphery of semi-circular portion 16 and horn portion 17. Side portion 18 has a first groove 19 therein of uniform cross section over its length. As seen in FIG. 3, first groove 19 comprises a floor portion 42 extending inwardly from side portion 18, a channel flange engaging wall 43 extending upwardly from floor portion 42, a step portion 44 extending further inwardly from flange engaging wall 43, a cap edge engaging wall 45 extending further upwardly from step portion 44, and a ceiling portion 46 extending outwardly from cap edge engaging wall 45 at an oblique angle to intersect side portion 18. 
     Back block 20 is fixedly mounted in main frame 11 by means of pin 21 at a predetermined radial distance from center pin 13 so that back block 20 is adjacent horn portion 17. 
     Referring now to FIG. 4, back block 20 is generally rectangular in shape, being in dimension along its front-to-back axis generally equal in length to the length of horn portion 17. Back block 20 has a second side portion 22, which faces first side portion 18, having a second groove 23 therein of uniform cross section over its length, and a rear end portion 41. 
     Second groove 23 is symmetric with first groove 19, being a mirror image thereof. When the back block 20 and forming die 15 are mounted in bender 10, opposed grooves 19 and 23 complement each other, as shown in FIG. 8, defining a recess 24 that substantially conforms to the cross section of a length of channel stock 25 with a length of cap stock 26 fitted atop thereof. 
     Drawing block 36 is elongated and generally rectangular in shape, being in dimension along its front-to-back axis generally equal in length to the length of first side portion 18, and includes a third side portion 37 with a third groove 38 therein, an opposite side wall 39, and a leading end portion 40. Third groove 38 is symmetric with first groove 19, being a mirror image thereof. 
     Referring to FIGS. 1 and 3, handrail cap stock 26 is a molded piece of metal stock having a dome portion 27 opposite cap edge portions 28a and 28b, and a recessed underside portion 29 with internal opposed side walls 30a and 30b. 
     Channel stock 25 comprises web portion 31 and external opposed walls 32a and 32b, defined by flange portions 33a and 33b. 
     Side walls 30a and 30b of underside portion 29 are a distance apart essentially equal to the distance between side walls 32a and 32b of channel stock 25. 
     A convenient cap stock/channel stock/flat stock assembly 34 is formed by fitting a length of flat stock 35 of width essentially equal to the distance between flanges 33a and 33b within the recess of a corresponding length of channel stock 25. Flat stock 35 acts as a spacer to prevent deformation of channel stock 25 during the bending operation. The length of channel stock 25 is then fitted into recessed underside portion 29 of a corresponding length of cap stock 26, so that side walls 30a and 30b engage side walls 32a and 32b, and the longitudinal axis of the length of cap stock 26 overlies the longitudinal axis of a length of channel stock 25, as seen in FIGS. 1 and 2. 
     In operation, swing frame 12 is moved to its fully open position, as shown in FIG. 2, and one end of assembly 34 is inserted between back block 20 and forming die 15, extending through recess 24. With swing frame 12 in the fully open position, and assembly 34 extending through recess 24, drawing block 36 is positioned in swing frame 12 between roller block 14 and first side portion 18, with leading end portion 40 abutting rear end portion 41 of back block 20. In this position, groove 38 engages a portion of the length of assembly 34, and opposite side wall 39 abuts roller block 14. This configuration is clearly shown in FIG. 2. 
     The length of assembly 34 can then be bent to the desired degree of curvature -- up to 180° -- by moving swing frame 12 toward the fully closed position, illustrated in FIG. 1. 
     Once the desired bend has been achieved, roller block 14 and drawing block 36 are removed from swing frame 12 and assembly 34 is withdrawn from recess 24. The lengths of channel stock 25, cap stock 26, and flat stock 35 are then separated from each other and flat stock 35 discarded. 
     The results of the above-described operations are that correspondingly curved and undistorted lengths of channel stock 25 and cap stock 26 have been easily and inexpensively bent in a single pull operation. 
     Numerous characteristics and advantages of our invention have been set forth in the foregoing description, together with details of the structure and function of the invention, and the novel features thereof are pointed out in the appended claims. The disclosure, however, is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts, within the principle of the invention, to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.