Releasable connection for sortation conveyor pusher

A pusher has a retaining member disposed within an opening in the pusher cap, a fastening member secured to the pusher base and a fuse element interposes between the retaining member and the fastening member, the fuse element failing upon the application of an undesirable level of force to said pusher cap.

TECHNICAL FIELD

The present invention relates generally to a pusher shoe assembly for a sortation conveyor, and more particularly to a releasable pusher shoe assembly. The invention will be disclosed in connection with, but not necessarily limited to, a fuse element retaining the pusher cap to the pusher base cap which permits the pusher cap to separate from the pusher base upon the application of a sufficient load.

BACKGROUND

Pusher shoe sortation conveyors are well known for directing articles on the conveyor to a desired path. In general, such sortation conveyors include a longitudinally moving endless conveying surface for carrying articles. Pusher shoes, also referred to as pushers or shoes, are carried by the conveyor, configured to be selectively directed to move across the lateral width of the sortation conveyor by actuation of a switch. The switch directs the pusher from a home path, along an outside edge of the sortation conveyor, onto a divert guide path underlying the conveying surface conveyor. The guide path, typically defined by a guide track, causes the pusher to move laterally so as to engage an article and divert it onto a spur conveyor.

Under certain circumstances, pushers may be subjected to an undesired level of force, such as might be applied to pusher cap during lateral divert of the pusher, which interferes with the desired travel of the pushers. In such instances, damage may occur to components of the conveyor, such as the guide tracks, switches, slats and pushers. A pusher which is configured for the pusher cap to separate from the pusher base upon the application of an undesired level of force can minimize or prevent damage to conveyor components.

Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings.

DETAILED DESCRIPTION

In the following description, like reference characters designate like or corresponding parts throughout the several views. Also, in the following description, it is to be understood that terms such as front, back, inside, outside, and the like are words of convenience and are not to be construed as limiting terms. Terminology used in this patent is not meant to be limiting insofar as devices described herein, or portions thereof, may be attached or utilized in other orientations. Referring in more detail to the drawings, an embodiment of the invention will now be described.

Referring toFIGS. 1,23&3A, there is shown pusher, generally indicated at2, configured as a dual sided pusher, although the teachings of the present invention may be applied to single sided pushers also. Pusher2comprises pusher cap4and pusher base6, which may be made of any suitable material such as black Nylon ST (Super Tough). Pusher cap4and pusher base6may be of any configuration suitable to incorporate a releasable connection in accordance with teachings of the present invention.

Pusher cap4is releasably retained to pusher base6by connection8. Connection8is configured to function as a mechanical fuse to allow pusher cap4to separate from pusher base6in the event an undesirable level of force is applied to pusher cap4. In the embodiment depicted, pusher cap4includes opening10having retaining member12. Retaining member12functions as a reaction member for fuse member14, resisting relative movement of fuse member14. In the embodiment depicted, retaining member12is configured as comprising annular surface between upper portion10aof opening10, having a larger diameter, and lower portion10bof opening10, having a smaller diameter. In the embodiment depicted, as a result of manufacturing processes, lower portion10bincludes draft in its upper wall section with the lower wall section being straight wall, with the intersection therebetween being illustrated as a horizontal line segment. Any suitable configuration of retainer member12may be utilized, such as a plurality of inwardly projecting members presenting a discontinuous annular land, providing resistance to relative movement of fuse member14.

Pusher base6includes opening or bore16, the center of which, when pusher cap10is disposed adjacent pusher base6in its proper location, is generally aligned with the center of opening10.

Spacer18is disposed mostly within lower portion10b, being shaped complementary thereto. With pusher cap4disposed atop pusher base6as shown, lower surface18bof spacer18is adjacent and in contact with upper surface6aof pusher base6. In the embodiment depicted, spacer18is annular, with its outer diameter being slightly less than the inner diameter of lower portion10b. Alternatively, the outer diameter could be sized to provide a press fit therebetween. Any suitable height and diameter dimensions will work. In the embodiment depicted, spacer18is made of Nylon 6/6, has a 0.500 inch diameter, and a 0.030 inch nominal clearance to lower portion10b. Spacer18is 0.250 inches tall with lower portion10bhaving a height of 0.243 inches.

Fuse member14is disposed adjacent and in contact with upper surface18aof spacer18. In the embodiment depicted, fuse member14is configured as a washer, and as such, outer peripheral surface14ais a generally circular circumference, although any shape complementary to opening10may be used. In the embodiment depicted, outer peripheral surface14ahas a diameter slightly less than the inner diameter of upper portion10aof opening10, which allows fuse member to be easily located in opening10adjacent retaining member12. In the embodiment depicted, outer diameter14ais 0.750 inches, and the inner diameter of upper portion10ais 0.781 inches, leaving a radial clearance of about 0.015 inches. The diameter of outer peripheral surface14ais larger than the inner diameter of lower portion10b. In the embodiment depicted, the inner diameter of lower portion10bwas about 0.558 inches, providing about a 0.096 inch radial overlap with retaining member12. In the embodiment depicted, with pusher cap4disposed atop pusher base6as shown, there is about 0.007 inch clearance between retaining member12and the lower surface of fuse member14. Within teachings of the present invention, this clearance may be greater, or zero (line to line). It may even be negative with spacer18being shorter than the height of lower portion10b, preloading fuse member14against retaining member12.

Fastening member20includes head20awhich is configured not to fit through the inner opening in fuse element14. In the embodiment depicted, head20ahas circular circumferential surface20bwith about a 0.492 inch diameter and inner diameter14bof fuse element14is about 0.390 inches, producing about 0.051 inches radial overlap.

Fastening member20includes body portion20cwhich cooperates with bore16to secure fastening member to pusher base6. In the embodiment depicted, fastening member20is a BosScrew from ITW Shakeproof 0.250–20×1.00 L. Body portion20chas a nominal diameter of 0.250 inches providing clearance with disposed through the central hole of spacer18, having an inner diameter of about 0.258 inches.

In the embodiment depicted, head20ais drawn tight to clamp fuse element14and spacer18between head20aand upper surface6aof pusher body6. It is this stackup which results in the 0.007 clearance between fuse element14and retaining member12. Spacer18provides upper surface18aagainst which head20aclamps fuse element14, to prevent head20afrom being rotated enough to pull head20athrough fuse element14(although over tightening of fastening member20could squeeze fuse element14out from between head22aand surface18a.

In the embodiment depicted, upon the application of an undesired level of force to pusher cap4will produce a separating force acting to separate pusher cap4from pusher base6. This will result from retaining member12exerting an upward force against the lower surface of fuse element14, and a resisting force exerted by head20cdown against the upper surface of fuse element14. The components of connection mechanism8are dimensioned such that fuse element14yields to permit head portion to pass through the inner opening of fuse element14when the level of force reaches the design level-the desired level of force. In the embodiment depicted, fuse element14is made of Nylon 6/6, about 0.063 inches thick. Head20cwill be pulled through the central opening in fuse element14, deflecting portions of fuse element14, making spacer18and head portion20cfree to pass out through the bottom of opening10, allowing separation of pusher head4from pusher base6.

The components of connection mechanism8may be of any suitable dimensions and materials to permit separation. For example, fuse element14could be brittle instead of flexible, breaking upon the application of an undesired level of force, allowing spacer and head portion20cto pass out of opening10. Fuse element14could sufficiently flexible and there could be adequate clearance between the outer diameter of head20cand the inner diameter of retaining member12to permit fuse element14to remain secured by fastening member20and pulled through lower portion10bof opening10. The level of force required to trigger connection mechanism8to allow separation can be increased or decreased by changing the dimensions of components, for example such as fuse element14, fastening member18, retaining member12or opening10. Alternatively, fuse element14could replaced by a member (not shown) which does not act as the weakest link, and fastening member20could be configured to act as the fuse element, breaking or otherwise separating upon the application of an undesirable level of force.

Although connection mechanism8releasably retains pusher cap4to pusher base6, the first resistance to separation is from the mounting configuration between pusher cap4and pusher base6. Referring toFIGS. 4 and 5, the bottom of pusher cap comprises a plurality of keys22a,22b,22cand22dextending therefrom. Keys22aand22care disposed on the same axis, with keys22band22ddisposed on another axis at a right angle to the axis for keys22aand22c, with the axes passing through the center of opening10. Although any suitable angle between axes may be used. In the embodiment depicted, keys22aand22care about 0.089 inches to about 0.090 inches wide, about 0.390 inches long and about 1.15 inches center to center. Keys22band22dare about 0.090 inches to about 0.093 inches wide, about 0.456 inches long and about 2.350 inches center to center.

Pusher base6includes corresponding keyways24a,24b,24cand24dcarried by upper surface6a. Keyways24aand24care shaped and located complementary to keys22aand22c, and keyways24band24dare shaped and located complementary to keys22band22d. In the embodiment depicted, keyways24aand24care about 0.093 inches to about 0.095 inches wide, and keyways24band24dare about 0.100 inches to about 0.103 inches wide.

Keys22a–22dand keyways24a–24dhelp reduce concerns about fits up, shrink rates and the action of dual sided diverting moving pusher cap4back and forth on pusher base6. These two sets of keys22aand22c, and22band22d, and corresponding keyways24aand24c, and24band24d, position and function to maintain the relationship between pusher cap4and pusher base6.

The initial resistance to forces loading pusher2come from keys22aand22c. Additional resistance is provided by tabs26aand26bmounted on resilient arm28a, and26cand26dmounted on resilient arm28b, in conjunction with tabs30a,30b,30cand30d. When pusher cap4is assembled to pusher base6, tabs30a,30b,30cand30dengage recesses32a,32b,32cand32dof pusher base6, and tabs28a,28b,28cand28dengage similar complementarily shaped recesses (not seen). The amount of force exerted by tabs26a–26dcontrols the grip of the tabs on pusher base6. To increase the force exerted by resilient arms28aand28bthrough tabs26a–26d, a resilient material, such as foam, may be placed into openings34aand34b. Any other suitable configuration may be used.

If the force applied to pusher cap6exceeds the restraining force of the keyways and tabs, connection mechanism8releasable retains pusher cap4to pusher base6. Connection mechanism8, keys and keyways, and tabs and slots may be utilized independently of each other, or in combination with any or all of each other.

The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described in order to best illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims submitted herewith.