Abstract:
A conveyor drive chain is equipped with pads of a high friction, resilient material. Each pad has a body secured to and overlying one link of the chain and has an extension at each end overlying the adjacent chain link. The extensions are wedge shaped, lengthwise of the chain, having one side face extending at an angle to the axis of the chain whereby the extension portions of two adjacent pads are seated side-by-side with the line of separation between them laterally inclined across the chain.

Description:
FIELD OF THE INVENTION 
     This invention relates to powered conveyors and, more particularly, to an improved propelling member for powering such a conveyor, which propelling member consists of a primary, high strength, tension load-carrying chain and a padding which provides a high friction, non-metallic roller or article contacting surface for the propelling member. 
     BACKGROUND OF THE INVENTION 
     Over the years, various combinations of chain and rubber or plastic pads or belts have been devised and used in the conveyor field. These have included devices in which the pad or high friction member is a continuous band, similar to a belt, which is mounted on the chain. Other devices include individual pads, one of which is mounted on each link of the chain, or pads of greater length designed to overlay a number of adjacent links of the chain. Examples of these types of construction are found in patents such as U.S. Pat. No. 2,792,928 entitled &#34;Attachment Clip For Lumber Conveyor Chains&#34; issued May 21, 1957 to W. G. Holz; U.S. Pat. No. 3,189,161 entitled &#34;Powered Roller Curve&#34; issued June 15, 1965 to D. A. Schneider et al; U.S. Pat. No. 3,306,430 entitled &#34;Belt-Chain Combination Drive&#34; issued Feb. 28, 1967; and U.S. Pat. No. 4,074,805 entitled &#34;Installation Equipment With A Driving Mechanism&#34; issued Feb. 21, 1978 to Bodewes. 
     While each of the constructions disclosed by the preceding patents has various merits, these pad and chain combinations have not been entirely satisfactory. While they have provided the advantage of the strength of a chain and the high frictional characteristics of the rubber or plastic pad, they have failed to solve the problem of excessive noise. They have also failed to solve the problem of quick and inexpensive replacement when sections of the pad are damaged, lost, or excessively worn. Despite these shortcomings, the advantage of this type of a combination has been recognized and as a result has been extensively used because the combination provides a propelling member or drive which has wear characteristics much improved over belts, and eliminates the dual problems of tracking and stretch, which are experienced with even the best belt-driven conveyor system. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The invention provides individual pads which are secured to the chain with each pad being so shaped that it has a portion at each end overlaying at least one other link than the one to which it is attached. Further, each of the ends is shaped such that it tapers to a point, thus producing a line of separation between it and the end of the next adjacent pad that is at a bias to the axis of the chain. In this manner, as the chain and pads are moved beneath the rollers of the conveyor, the transition from one pad to the other is gradual and there is no abrupt or sudden transfer to produce either noise or interruption or variation in the motion transmitted to the roller. While the ends of the individual pads are radiused to facilitate the transit about the drive sprockets at the ends of the runs of the chain, because of the overlap and the gradual transition created by the biased line of demarcation between the individual pads, this radiusing has no affect upon the drive of the rollers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary, sectional, elevation view of a conveyor equipped with this invention with the side of the track supporting the chain removed for clarity; 
     FIG. 2 is a fragmentary, enlarged plan view of the chain and pad combination of this invention; 
     FIG. 3 is a fragmentary, enlarged partially broken side view of the chain equipped with the pads of this invention; 
     FIG. 4 is a sectional elevation view taken along the plane IV--IV of FIG. 3 showing the propelling member nested in its supporting channel; 
     FIG. 5 is a side elevation view of one of the pads of this invention; 
     FIG. 6 is a plan view of one of the pads of this invention; and 
     FIG. 7 is an end view of one of the pads of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the numeral 10 indicates a conveyor having sides 11 between which are rotatably mounted a plurality of rollers 12 which, collectively, provide an article conveying surface. Beneath the rollers is a channel 13 providing a guide and support for the propelling member 14 (FIGS. 1 and 4). The channel 13 has a liner 19 to provide a wear resistant, low friction surface for guiding and supporting the propelling member 14. The channel 13 and thus the propelling member 14 can be supported in any suitable, conventional manner such as by the springs 16 which rest on the crosspieces 17 of the conveyor frame. All of the structure which has been described is conventional and has long been used in the conveyor art. 
     As best seen in FIGS. 2 and 3, the propelling member 14 has a chain 15 of conventional construction consisting of links 20 and 20a pivotally joined together by pins 21 surrounded by roller sleeves 22. Each link, between the roller sleeves 22 at its opposite ends, provides an opening 23 of somewhat hourglass shape (FIG. 3). This type of chain is conventional and when designed for lighter duty, it is commonly marketed as bicycle chain. This type of chain has been used for many years in the conveyor industry. 
     Mounted to the chain are a plurality of pads 30. Each pad has a primary body portion 31 including a central section 32 and a pair of end portions 33 and 33a (FIG. 5). The central portion extends the full width of the opening 23 between a pair of the sides forming one of the links 20a and also the length of the opening 23 which corresponds substantially to the spacing between a pair of the roller sleeves 22. Each of the ends extends lengthwise of the chain sufficiently to overlap the remainder of the link to which the pad is attached and to overlap all or almost all of the next adjacent link. Each of the ends 33 and 33a is tapered by having one side extending parallel to the sides of the chain and the other side inclined in an oblique angle to the longitudinal axis of the chain whereby each end gradually tapers to a point lengthwise of the chain. Opposite ends of the same pad are tapered on opposite sides whereby the vertical planes of the inclined sides of each link are parallel, thus producing a pad having a top shape which is generally that of an oblique parallelogram. The top surface of the pad is flat except at the very tip ends of the end portions which are downwardly radiused at 37 to reduce or eliminate the problem of the ends projecting up any significant distance from the remaining surface of the propelling member as the pad and the chain pass around the pulleys at the end of each run. 
     Projecting from the bottom of the center section of each pad is an anchor member or stem 40. The stem 40 is of the full width of the pad and its lower end is bifurcated at 41 to form a pair of fingers 42 and 42a. The fingers flare lengthwise of the pad toward the end portions 33 and 33a and thus produce recessed pockets 43 and 43a on opposite sides of the anchor member. The pockets 43 and 43a are of a size and shape to snugly and firmly receive and seat against and around the roller sleeves 22 at the ends of the chain link to which the pad is secured. It will be noted that the bifurcation slot 41 separating the fingers 42 and 42a is V-shaped. This facilitates the compression or squeezing together of the fingers 42 and 42a when the stem is inserted through the opening 23 in one of the chain links. 
     The central section 32 has a pair of blind openings 44, one on each side. The combined depths of the openings 44 is less than the width of the pad leaving a longitudinal central web 45. These openings facilitate molding of the pad by helping to control shrinkage which produces sink marks in the surface due to differentials in shrinkage between sections of substantially different wall thickness. The central web 45 provides continuous longitudinal support for the pad&#39;s surface. 
     The pad is preferably molded from a material having high resistance to scuff and wear and also having a high coefficient of surface friction. The material must have a limited degree of resilience to permit it to cooperate with the chain and also to permit it to be installed on the chain. A preferred material for the manufacture of the pads is a moldable urethane, for example, urethane marketed by E. I. Dupont de Nemoirs under the trademark &#34;Hytrel&#34;. 
     It will be recognized that the invention provides a continuous surface so far as each individual driven roller is concerned contacted by the propelling member. The transfer of the roller from one pad to another is gradual, as the sloping line of separation or demarcation passes beneath the roller. Thus, there is nothing to bounce or vibrate the roller and its movement is continuous, and the noise incident to a transverse separation line between pads passing under a roller is eliminated. This makes it practical to utilize individual pads of short length. This is particularly desirable because such pads are easier and simpler to install and do not have a tendency to separate from the chain as the propelling member passes around the drive pulleys. Also, as normally occurs with any chain, there is, over a period of time, a stretching of the chain due to wear and other factors. Since each pad is secured to one link only, and bridge the surface of only a short length of the chain, this stretching of the chain has no adverse affect upon the pads. Even if it causes some increase in the gap between links, this will not cause trouble because the long overlap between links will prevent any increase in noise or change in roller operational characteristics. Chain stretch has been a problem where long pads were utilized which were continuous for a number of links because, while the chain stretched, the pads did not stretch correspondingly, and thus there was a tendency for the pads to pull loose from the chain as the hours of usage of the chain increased. Another problem encountered with long pads has been the stretching of the pads as the chain/pad combination passes around the pulleys due to the increase in path length for the pads because of the increased radius of their path of travel. This alternate stretching and contracting not only materially increases pad wear, it also causes the pads to pull free of the chain. 
     The arrangement is also particularly desirable because it renders immaterial the length of the chain since the pads are installed one by one. It is also true that the pads can be quickly, easily and relatively inexpensively replaced as needed. 
     It will be recognized that while a preferred embodiment of the invention has been described, that other embodiments can be made without departing from the principles of the invention. Such modifications are to be considered as included in the hereinafter appended claims unless these claims by their language expressly state otherwise.