Fastener with attached compression limiting sleeve

A fastener system that includes a fastener, a compression-limiting sleeve, and a retainer which generally retains the compression-limiting sleeve on the fastener. By providing that the compression-limiting sleeve is not staked to the fastener, existing technology can be used, and no extra staking processing step needs to be performed. The fastener may comprise a conventional metal threaded screw or bolt, possibly having a recess in its head for receiving a driver. Preferably, the compression-limiting sleeve is cold headed as opposed to being stamped, and preferably includes a counter bore which assures that an end of the retainer is below an end surface of the compression-limiting sleeve. Preferably, the retainer is formed of a thermoplastic elastomer or another suitable material.

BACKGROUND

The present invention generally relates to fasteners, and more specifically relates to a fastener system that has a compression-limiting sleeve effectively attached to a fastener.

In a fastener application where there is a need to limit compression, a conventional fastener system provides that a compression limiting member, such as a stamped sleeve or bushing, is staked to a threaded fastener. The sleeve or bushing, with the threaded fastener staked thereto, is then inserted into a hole which is provided in a first workpiece, and subsequently the fastener is threaded into a threaded bore which is provided in a second workpiece. This secures the first workpiece to the second workpiece, and provides that the sleeve or bushing absorbs compressive forces that otherwise would have to be absorbed by the first workpiece.

Disadvantages of such a fastener system include the fact that staking requires a secondary operation. Additionally, stamping the sleeve or bushing results in significant scrap and provides that tolerances cannot be closely controlled. Furthermore, the system does not readily provide that the column strength of the sleeve or bushing can be changed merely by altering the wall thickness or hardness of the sleeve or bushing.

SUMMARY

An object of an embodiment of the present invention is to provide an improved fastener system for use in an application where compression is relevant or must be absorbed.

Briefly, an embodiment of the present invention provides a fastener system that includes a fastener, such as a threaded bolt or screw, a compression-limiting sleeve, and a retainer which generally retains the compression-limiting sleeve on the fastener. By providing that the compression-limiting sleeve is not staked to the fastener, existing technology can be used, and no extra staking processing step needs to be performed.

DESCRIPTION OF AN ILLUSTRATED EMBODIMENT

While this invention may be susceptible to embodiment in different forms, there is shown in the drawings and will be described herein in detail, a specific embodiment with the understanding that the present disclosure is to he considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated.

FIG. 1illustrates a fastener system10which in accordance with an embodiment of the present invention. The fastener system10is configured for use in applications where limiting compression is relevant. Specifically, the fastener system10comprises a fastener12, such as a conventional threaded screw or bolt. The fastener12is preferably formed of metal, and preferably incorporates a drive system (such as a recess14on a head16of the fastener12) to transfer tightening torque, such as a drive system consistent with that which is disclosed in U.S. Pat. No. 3,584,667, for example. While the fastener12is shown as having a head16with a recess14, the present invention can be employed with effectively any head style with regard to the fastener12.

The fastener system10also comprises a compression-limiting sleeve20. Preferably, the compression-limiting sleeve20is also formed of metal, and is preferably cold headed as opposed to being stamped. This not only results in significantly less scrap, but also provides that both the outer diameter and the inner diameter of the compression-limiting sleeve20can be formed to a tight tolerance. Preferably, the compression-limiting sleeve20is generally cylindrical, but may include a lip22at one end24thereof as shown inFIG. 1. As shown, the compression-limiting sleeve20also preferably includes an internal counter bore26. The function of this counter bore26will be described more fully hereinbelow. Preferably, the compression-limiting sleeve20has a minimum bearing surface which is engineered to effectively meet the strength of the fastener12being used in the system10. While the compression-limiting sleeve20is shown as having a lip22, the present invention can be employed with or without the lip22.

As shown inFIG. 1, the fastener system10also comprises a retainer30. The retainer30is configured to generally retain the compression-limiting sleeve20on the fastener12, without having to physically stake the compression-limiting sleeve20to the fastener12. Preferably, the retainer30is formed of a thermoplastic elastomer or another suitable material. Specifically, the retainer30may have a profile as shown inFIG. 2, and specifically may be provided as being consistent with that which is disclosed in U.S. Pat. No. 5,395,194; Reissue No. 36,164; and U.S. Pat. No. 6,039,525. As shown inFIG. 1, the fastener12extends through the retainer30, and the retainer30is disposed generally between the fastener12and the compression-limiting sleeve20. Preferably, the retainer30retains the fastener12relative to the compression-limiting sleeve20such that the fastener12can float longitudinally, such as at least 1 mm, to facilitate alignment during installation.

As discussed briefly above, the compression-limiting sleeve20preferably includes a counter bore26. The space32between an internal shoulder34of the counter bore26of the compression-limiting sleeve20and the one end36of the retainer30assures that the other end38of the retainer30will be below an end surface40of the compression-limiting sleeve20once the fastener system10is installed.

To install the fastener system10, the compression-limiting sleeve20, while being retained on the fastener12by the retainer30, is inserted in a hole80in a first workpiece82(seeFIG. 1). Then, an end42of the fastener12is aligned with a threaded bore84in a second workpiece86. A driver is engaged with the recess14in the head16of the fastener12, and the driver is actuated to drive the fastener12into the second workpiece, thereby effecetively securing the second workpiece to the first workpiece (as indicated by arrow90inFIG. 1). During and after installation, the compression-limiting sleeve limits or absorbs compressive forces which otherwise would impact the first workpiece.

As discussed above, preferably the compression-limiting sleeve20is cold headed as opposed to being stamped. This not only results in significantly less scrap, but also provides that the compression-limiting sleeve20can be formed to tighter tolerances. Additionally, because the retainer30functions to retain the compression-limiting sleeve20on the fastener12as opposed to the compression-limiting sleeve20having to he staked on the fastener12, a secondary staking operation need not be performed and existing technology can be utilized to assemble and hold the components of the fastener system10together. Furthermore, the fastener system10provides that the column strength of the compression-limiting sleeve20can be easily matched to the application by varying the wall thickness or hardness (or both) of the compression-limiting sleeve20.

While a specific embodiment of the invention has been shown and described, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the present invention.