Testing footwear soles
BACKGROUND OF THE INVENTION 
     This invention relates to machines for testing footwear soles. Typically such machines are designed for accelerated life testing of soles under simulated conditions of actual use. 
     SUMMARY OF THE INVENTION 
     The invention provides an improved machine capable of accurately simulating a variety of conditions of actual use. The machine is rugged, easily operated, and inexpensive to manufacture, and yet provides high speed operation with sophisticated adjustable control over several parameters associated with human walking motion. The preferred embodiment is particularly designed for greatly accelerated testing of so-called unit construction soles made from a rubbery composition. 
     In general the invention features apparatus for testing footwear soles, comprising a frame, treadmill supports mounted on the frame for movement along an axis, a treadmill assembly mounted on the supports, the assembly including an operative treadmill surface movable in its own plane along a direction transverse to the axis, resilient means connected to the frame and the supports for biasing the treadmill surface in a rest position and for resiliently opposing movement of the surface along the axis away from the rest position to a range of operating positions, a shaft mounted on the frame, the shaft being located with its longitudinal axis parallel to the operative treadmill surface and spaced from the rest position thereof in the direction away from its range of operating positions, a drive for rotating the shaft about its axis, and a sole support mounted on the shaft at a distance from the shaft axis sufficient so that when a sole to be tested is installed on the sole support and the shaft is rotated by the drive, the sole support will carry the sole along the operative treadmill surface to move the surface along its plane and, against the resilient force of the resilient means, to the range of operating positions. In preferred embodiments the frame includes a base and a plurality of posts on the base, the posts extending through openings in the treadmill supports, and the resilient means comprises coil springs around the posts between the base and the supports; the treadmill assembly comprises a plurality of rollers having shafts carried between the supports, and an endless belt wrapped around the rollers; a plurality of sole supports are connected to the shaft through threaded rods screwed into a hub mounted on the shaft, the rods being angularly spaced for balance and adjustable radially with respect to the shaft axis; each sole support includes a sole plate with a toe portion hinged to a heel and shank portion, whereby when a sole to be tested is mounted on the sole plate and carried along the belt the sole will flex along the line of intended flexure in use on a foot; an adjustable brake is provided to vary the force necessary to move the belt over the rollers whereby the soles can be caused to at least partially slip along the belt to simulate scuffing; a counter is mounted adjacent the shaft to count its revolutions; and an indicator is provided for indicating the distance between the rest position and the operative position of the treadmill surface at any given moment in operation, whereby the indicator provides a reading of the force applied to the sole by the belt. 
     Other advantages and features of the invention will be apparent from the description and drawing herein of a preferred embodiment thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a semi-schematic isometric view of apparatus embodying the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, the main machine frame consists of a base 10, two shaft support posts 12, and four treadmill support posts 14 arranged at the corners of a rectangle between posts 12. 
     Each post 14 carries a coil spring 16. Treadmill support frame 17 includes support brackets 18 and 19, each with horizontal flanges 20, 21 which have holes to receive the ends of posts 14 extending above springs 16, and vertical portion 22, 23 provided with openings to receive the ends of parallel shafts 24, 24a. Each shaft 24, 24a carries a freely rotatable roller 26. The endmost shaft 24a is received in elongated slots 28 and is connected at its ends to eye bolts 30 and 31. The eye bolts extend through end flanges 32 of frame 17 and have nuts 33, 34 on their ends to form adjustable take-ups for shaft 24a. Endless neoprene belt 36 is wrapped around rollers 26 to form a treadmill. By adjusting take-up bolts 30 and 31 the horizontal position of shaft 24a, and hence the tension in belt 36, can be changed, in turn changing the force necessary to rotate the treadmill rollers (because a tighter belt increases the friction between the end rollers and their shafts). In this sense the take-ups constitute a treadmill brake. 
     Cross shaft 40 extends through posts 12 above the treadmill, and has its axis 42 parallel to the axes of the treadmill rollers. Hub 44 is fixed at the center of shaft 40. Radially extending adjustable threaded rods 46, 48 are screwed into the hub, 180° apart to provide a balanced assembly. Fixed to the outer end of each rod is a metal sole plate 50, 52. Each sole plate has the general shape of the sole 60 to be tested, and has a toe portion 62 connected to a shank and heel portion 64 by hinge 66 located at the line along which the sole is intended to flex in use. 
     A spring loaded snubber 68 is pivoted to toe portion 62 of plate 50 and is connected through adjustable threaded rod 72 to hub 44. The snubber provides additional force (beyond that provided by the inherent resilience of the sole itself) to bias toe portion 62 outwardly toward a position coplanar with portion 64. A similar snubber may be used with the other sole plate if desired. 
     Motor 80 is mounted on base 10 and is arranged to rotate shaft 40 through chain and sprocket drive assembly 82. Revolution counter 84 is mounted adjacent eccentric 86 on the end of shaft 40 to count its revolutions. 
     To operate the device described above, soles 60 to be tested are attached to plates 50 and 52, e.g., with contact cement, or even with straps (not shown) located in areas not intended to contact the treadmill. Rods 46, 48 and 72 are adjusted so that when shaft 40 is rotated by motor 80, plates 50 and 52 will carry soles 60 along and press them against the upper operative surface 96 of the treadmill belt, compressing springs 16 so that a selected amount of back force against the sole bottoms is exerted through belt 36. A pointer 100 is mounted on flange 21 and cooperates with graduations on post 12 to indicate the amount by which springs 16 are compressed, and hence the reaction force applied to the soles. That force can be increased by adjusting the sole plates to positions radially farther out from hub 44. 
     As the soles pass over the treadmill, they will flex along the lines of hinges 66. That flexure (the resistance to which can be adjusted in the case of plate 50 by adjusting snubber rod 72 in hub 44), along with the resilient quality of the treadmill provided by springs 16, closely simulates the flexure and sole compression of actual walking conditions. Furthermore, a controlled degree of scuffing can be introduced by tightening take-up bolts 30 and 31 so that belt 36 resists movement sufficiently to cause the soles to at least partially slip along surface 96. The ability to apply substantial force against the sole bottoms greatly accelerates the testing process. 
     A variety of surface conditions can be simulated by applying substances such as oil or abrasives to belt 36. 
     Other embodiments are within the following claims.