Traction device

An improved traction device for a motor vehicle provides a rear support assembly positioned proximate to a rear axle and an adjacent portion of a leaf spring and a front rocker support assembly. The front rocker support assembly includes a front leaf spring bracket assembly attached to a selected portion of the leaf spring between the axle and the front leaf spring mount, a rocker pivotally attached to the front leaf spring bracket assembly, and a rocker head connected to an end of the rocker for engaging a lower surface of the leaf spring to limit pivotal movement of the front rocker support assembly relative to the front end of the leaf spring, and. An adjustable rigid link extends between the rear support assembly and the front rocker support assembly.

BACKGROUND OF THE INVENTION

This invention relates generally to suspension systems of high performance motor vehicles. More specifically, but not by way of limitation, the present invention relates to an improved traction device for limiting wrap-up of a leaf spring of a motor vehicle during acceleration.

Conventional leaf springs are widely used in rear-wheel drive vehicles. During acceleration, the leaf spring is subject to twisting forces which are opposite in direction to the acceleration of the drive wheels. The opposed twisting forces are commonly referred to as “wrap-up” and often contribute to rear wheel “hop”.

A number of devices have been designed to minimize leaf spring wrap-up and rear-wheel hop during acceleration. One of these is a simple bolt-on traction bar. A rigid bar, generally of steel, has a mounting pad on one end for attachment to the point at which the rear axle meets the leaf spring assembly. A rubber “snubber” at the other end is used to attach the rigid bar to the front eye of the leaf spring. The length of the bar extends forward from the mounting pad to a point under the front leaf spring eye. During acceleration, the counter-rotation of the rear axle is arrested when the snubber meets the spring eye. Bolt-on traction bars decrease leaf spring wrap-up, help to prevent rear wheel hop, and aid in improving rear wheel traction during acceleration. Additionally, the bolt-on traction bars are typically relatively inexpensive and easy to install.

Several other devices have been devised which represent improvements over the bolt-on traction bar. One such device is the ladder bar and another is the 4-link system. The ladder bar device comprises two mounting assemblies. One end of each mounting assembly is welded to the rear axle housing and the other is welded to a forward point of the chassis. These mounting assemblies are interconnected by a tubing structure. The 4-link system, which sometimes eliminates the conventional leaf spring from the motor vehicle, utilizes two 2-link assemblies (one on each side). One end of each 2-link assembly is welded to the rear axle housing and the other end is welded to a forward location on the chassis. Adjustable tubular links connect the rear axle housing to the chassis.

Each of these improved devices reduces leaf spring wrap-up and rear wheel hop, improves traction, and adjusts the instant center (the point at which the rear wheels push the vehicle forward). The ladder bar and the 4-link system, which are more expensive than simple bolt-on traction bars, require professional installation.

In U.S. Pat. No. 5,354,092, issued to Calvert, an improved traction bar includes a rear support assembly attached to the rear axle and the leaf spring and a front support assembly pivotally attached to the front end of the leaf spring. A rigid link extends between the rear support assembly and the front support assembly. The front support assembly is attached to the front of the leaf spring by a bushing which extends through the eye of leaf spring. The front support assembly includes a pivot stop which engages the upper surface of the leaf spring and limits movement of the front support assembly relative to the front end of the leaf spring. The pivotal movement limiting means includes means for engaging an upper surface of the leaf spring in the form of a pivot stop which extends across the upper surface of the leaf spring. The front support assembly includes a pair of generally triangular pivot plates which are pivotally attached to the front end of the leaf spring. The triangular pivot plates support the pivot stop at a fixed distance from the front end of the leaf spring and provide a point of attachment for the rigid link below the front end of the leaf spring. The pivot plates are secured to one another by three bolts positioned generally adjacent to the three corners of the triangular plates. The bolts serve to provide a pivot axis for the front support assembly relative to the front end of the leaf spring, the pivot stop itself, and the location of the point of attachment of the rigid link to the front support assembly. The rigid link is adjustable in length through the use of a threaded front eye connector and an oppositely threaded rear eye connector. Rotation of the rigid link thus changes the overall length of the rigid link.

While providing some improvement in leaf spring wrap-up, rear wheel hop, traction, and movement of the instant center forward with respect to the rear axle, the Calvert patent's effectiveness is limited by the structure of the front support assembly. The use of triangular pivot plates restricts the location of the pivot stop on the top surface of the leaf spring to a position comparatively close to the front eye of the leaf spring. Optional mounting apertures in the triangular pivot plates permit limited optional location of the threaded front eye connector of the rigid link, but additional adjustability is always helpful.

As can be seen, there is a need for a traction device for motor vehicles which is more effective in preventing leaf spring wrap-up and rear wheel hop by moving the vehicle instant center forward with respect to the rear axle and, simultaneously, improving traction during hard acceleration.

SUMMARY OF THE INVENTION

A traction device for a motor vehicle is provided, where the traction device comprises an adjustable link having a first attachment eye on an end of the adjustable link and a second attachment eye on an opposite end of the adjustable link; a rear support assembly positioned proximate to a rear axle and an adjacent portion of a leaf spring, where the rear support assembly comprises a rear support attachment means for attaching the rear support assembly against a lower surface of the leaf spring, and a rear attachment means for pivotal connection with the second attachment eye of the adjustable link; a front rocker support assembly that comprises the following: a front leaf spring bracket assembly removably attached a selected portion of the leaf spring between the axle and the front leaf spring mount, the leaf spring bracket assembly positioned against the lower surface of the leaf spring; a rocker subassembly pivotally attached to the front leaf spring bracket assembly, the rocker subassembly extending in a forward direction and terminating with a rocker head that bears on the lower surface of the leaf spring; and front attachment means for pivotal connection with the first attachment eye of the adjustable link.

In addition, a traction device is provided for limiting wrap-up of a leaf spring of a motor vehicle under acceleration, where the vehicle has a rear axle and the leaf spring has a front leaf spring mount in front of the rear axle and a rear leaf spring mount to the rear of the rear axle. The traction device comprises: a rear support assembly positioned proximate the rear axle, where the rear support assembly comprises: a flanged bracket bolted in place adjacent the leaf spring opposite the rear axle, and a rear mount bracket extending downwardly from a flanged bracket, with the rear mount bracket providing, at its lower end, an attachment means for connecting another member to the rear support assembly; a front rocker support assembly attached to a portion of the leaf spring between the axle and the front leaf spring mount, where the front rocker support assembly further comprises: a front leaf spring bracket assembly abutting a lower surface of the leaf spring; a rocker subassembly supported for pivotal movement by the front leaf spring bracket assembly, the rocker subassembly extending in a forward direction for a selected distance and terminating with a rocker stop for engaging a lower surface of the leaf spring to limit pivotal movement of the rocker subassembly; and a rocker attachment means for attaching a rigid link to the rocker; and a rigid link extending between the attachment means of the rear support assembly and the attachment means of the front support assembly.

A method for limiting wrap-up of a leaf spring on acceleration of a motor vehicle is also provided, where the method comprises the steps of: providing a traction device comprising a rear support assembly; a front rocker support assembly further comprising a front leaf spring bracket and a rocker pivotally attached to the front leaf spring bracket, with the rocker having a rocker head abutting a bottom surface of the leaf spring; and a rigid link extending between an attachment means of the rear support assembly and an attachment means of the rocker; selecting a portion of the leaf spring between an axle and a front leaf spring mount; removably attaching a front leaf spring bracket subassembly to the bottom surface at the selected portion of the leaf spring without disengaging the front leaf spring mount from the vehicle; and removably attaching the rear leaf spring bracket subassembly to the bottom surface of the leaf spring immediately adjacent the axle; wherein torque exerted by the wheels longitudinally along the rigid link forces the front leaf spring bracket subassembly downwardly while the rocker head exerts an upward force against the bottom surface of the leaf spring with the rocker head serving as a fulcrum to redirect the force downwardly against the leaf spring.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the of the present invention, like numerals and characters designate like elements throughout the figures of the drawings.

Referring toFIG. 1, an improved traction device20may be attached to a standard leaf spring L and a rear axle A. The rear axle A may support a wheel W in contact with a road surface S. The leaf spring L may include a rear leaf spring mount R (not shown) supported by the motor vehicle chassis and a front leaf spring eye E (not shown) supported by a front leaf spring mount F attached to the motor vehicle chassis. It will be appreciated by one skilled in the art that the standard leaf spring L, the rear axle A, the wheel W, the rear leaf spring mount R, the front leaf spring eye E, the front leaf spring mount F, and the motor vehicle chassis are typical and, therefore, no illustration is necessary.

The improved traction device20may include a rear support assembly22, a rigid link assembly52, and a front rocker support assembly82. Referring now to the rear support assembly22, a flanged bracket24may cooperate with a leaf spring axle bracket26to receive the leaf spring L therebetween. U-bolts28may encircle the axle A. Threaded ends30of the U-bolts28may extend through apertures32in the flanged bracket24. The U-bolts28may be held in place by nuts34. Parallel tabs36may project downwardly from the flanged bracket24. The flanged bracket24may include at least four apertures32through which the U-bolts28extend. Front and rear flanges38at the forward and rearward edges of the flanged bracket24may extend downwardly away from the leaf spring lower surface40. A fifth aperture42(seeFIG. 2) may be provided in the flanged bracket24for the leaf spring bolt, if necessary. The parallel tabs36may be generally triangular in shape and include two pairs of aligned apertures44-44and46-46at their lower ends for receiving a nut-bolt assembly48to secure a rear end54of the rigid link assembly52therein. Apertures50(only one shown) in the front and rear flanges38may provide a convenient mounting location for a shock absorber (not shown).

It will be understood by one skilled in the art that the rear support assembly22described herein is a modification of a support assembly well known in the art. The present improved traction device20according to applicant's invention may include optional aligned apertures44-44and46-46in the downwardly extending tabs36for attachment of the rear end54of the rigid link assembly52. The second pair of aligned apertures may provide further flexibility and adjustability in implementation of the improved traction device20, according to applicant's invention.

Referring toFIG. 1andFIG. 2, the rigid link assembly52may be employed to connect the rear end support assembly22with the front rocker support assembly82. The rigid link assembly52may have a rear end portion54attached to the rear support assembly22and a front end portion56attached to the front rocker support assembly82. A rear eye connector58may be threaded into a rigid bar60at the rear end54of the rigid link assembly52, and a front eye connector62may be threaded into the rigid bar at the front end portion56of the rigid link assembly52. The rigid bar60may be typically constructed by welding internally oppositely threaded front and rear inserts into the ends of a rigid bar. Oppositely internally threaded ends of the rigid bar60permit the rigid bar to be operated like a turnbuckle. i.e. the rigid bar60may be turned one direction to increase the distance between the eye portions of the eye connectors58,62or the rigid bar60may be turned the opposite direction to shorten the distance between the eye portions of the eye connectors58,62. An external hex fitting64may be provided to permit easy adjustment of the rigid bar60.

It will be understood that the rigid link assembly52described herein is well known in the art. A rotatable bushing may be typically deployed within the eye of the eye connectors58,62. Because the implementation of the rigid link assembly52shown herein is well known to persons skilled in the art, the rigid link assembly52will not be described in great detail.

Referring now toFIG. 1,FIG. 2, andFIG. 3, the front rocker support assembly82may include a rocker subassembly84pivotally attached to a front leaf spring bracket subassembly86. The rocker subassembly84may be formed by a pair of identical, generally triangular plates88permanently arranged in parallel relationship to a cylindrical spacer (not shown) with an axial channel therethrough. The axial channel may be aligned with a pair of aligned pivot bolt apertures, identified here by way of example as89-89and90-90, near one corner of each of the triangular plates88for pivotal movement of the rocker subassembly84. The number of pairs of aligned pivot bolt apertures may be arbitrary and dependent upon the size of the triangular plates88. The rocker subassembly84may also have a plurality of pairs of aligned link positioning apertures, identified here by way of example as91-91,92-92,93-93,94-94, and95-95, along a side common with the pivot bolt apertures89-89and90-90. The number of pairs of aligned link positioning apertures may be arbitrary and dependent upon the size of the triangular plates88. The aligned link position apertures may be positioned in a downwardly extending portion of the parallel triangular plates88. InFIG. 3, the front eye connector62of the rigid link assembly52may be attached to the rocker subassembly84by a nut-bolt assembly98disposed through the eye of the eye connector62and a selected pair of aligned link positioning apertures (91-91,92-92,93-93,94-94, and95-95) as designated above. The rocker subassembly84may further include a transverse rocker head100located at the third corner of the parallel triangular plates88. The transverse rocker head100may bear on the lower surface69of the leaf spring L.

The rocker subassembly84may be pivotally attached to the front leaf spring bracket subassembly86in a manner described below. The front leaf spring bracket subassembly86may include a generally horizontal plate70having a lower surface71from which two identical substantially parallel elongated plates110depend. The horizontal plate70may be removably secured against the lower surface40of the leaf spring L by a plurality of U-bolts73that each extend from the horizontal plate70over a spring leaf upper surface69and back to the horizontal plate70. Each U-bolt73may be inserted through holes74in the horizontal plate70and secured thereto. For example, the ends of each U-bolt73may be threaded to receive a nut75and washer so that it may draw the horizontal plate70against the lower surface40of the leaf spring for secure positioning without removal of either end of the leaf spring L. Other means of removably securing the horizontal plate70of the front leaf spring bracket subassembly86against the leaf spring L without departing from the scope of the invention.

Referring again toFIG. 3, the elongated plates110of the front leaf spring bracket subassembly86may be spaced apart a distance sufficient to allow the triangular plates88of the front rocker subassembly84to be inserted therebetween without frictional binding. The pair of elongated plates110may have a plurality of pairs of upper aligned apertures, indicated by way of example as112-112and114-114. A selected pair of upper aligned apertures (91-91,92-92,93-93,94-94, or95-95) may receive a nut-bolt assembly120that may be inserted through the selected upper aligned aperture and both the selected pair of aligned pivot bolt apertures (89-89or90-90) in the triangular plates88and the axial channel of the cylindrical spacer, so as to allow the rocker subassembly84to pivot freely about the nut-bolt assembly120.

The improved traction device20may be installed according to the following procedure. A portion of the leaf spring L between the axle A and the front leaf spring mount F may be selected for mounting the front leaf spring bracket subassembly86. This location may be selected according to criteria which may vary from vehicle to vehicle, e.g. load distribution of the vehicle, torque produced on the rear wheels by the drive train, length of the overall leaf spring, desired performance of the vehicle under acceleration, etc. These criteria may be known in advance or may be determined by experimentation.

Then, the front leaf spring bracket subassembly86may be removably attached to the bottom surface of the selected portion of the leaf spring L that extends between the axle A and the front leaf spring mount F without disengaging the front leaf spring mount F from the vehicle. This may be accomplished by placing the U-bolts of the front leaf spring bracket subassembly86over the upper surface69of the leaf spring L so that the downwardly depending ends of the U-bolt73may be inserted through the holes74of the horizontal plate70held against the lower surface40of the leaf spring L and secured to the horizontal plate70by nuts75. The nuts75may be tightened sufficiently so that frictional engagement of the horizontal plate70against the lower surface40is sufficient to prevent the horizontal plate70from moving longitudinally along the leaf spring L.

The rocker subassembly84may in turn be pivotally attached to the front leaf spring bracket subassembly86by the nut-bolt combination120disposed simultaneously through a selected upper aligned aperture, the selected pair of aligned pivot bolt apertures (89-89or90-90) in the triangular plates88, and the axial channel of the cylindrical spacer, so as to allow the rocker subassembly84to pivot freely about the nut-bolt assembly120.

The rear support assembly22may then be attached to an area of the leaf spring L below the rear axle A by positioning the flanged bracket24on the lower surface40of the leaf spring L with U-bolts28encircling the axle A. The threaded ends30of the U-bolts28may extend through apertures32in the flanged bracket24and secured by nuts34.

Next, the eye of eye connector58of rigid bar60may be positioned between the parallel tabs36of the flanged bracket24and secured for pivotal movement by a nut-bolt assembly48inserted through the eye connector58and a selected pair of aligned apertures44-44or46-46. The other eye connector62of the rigid bar60may be positioned between the triangular plates88of the rocker subassembly84and secured for pivotal movement by nut-bolt assembly98inserted through the eye of the eye connector62and a selected pair of aligned link positioning apertures (91-91,92-92,93-93,94-94, or95-95).

Finally, the rigid bar60of the rigid link assembly52may then be turned to lengthen or shorten the rigid link assembly52, so that the rocker head100bears on the lower surface40of the leaf spring L.

It should be noted that the previously enumerated steps for installing the improved traction device20on a vehicle may be performed in different orders without departing from the scope of the invention. Also, some steps of the procedure may be omitted since the improved traction device20may be shipped in a partially assembled state, without departing from the scope of the invention. The installation procedure is illustrative and given as an example only to better understand the device and the factors that may influence the installation.

In operation, force may be directed along arrow140during acceleration. The force directed along arrow140may be transferred through the rocker subassembly84to the front leaf spring bracket subassembly86. The front leaf spring bracket subassembly86may be forced downwardly while the rocker head100exerts an upward force against the lower surface40of the leaf spring L. With the rocker head100serving as a fulcrum, the force directed along arrow140is now applied downwardly against the upper surface69of the leaf spring L.

Referring again toFIGS. 1-3, Those persons skilled in the art may understand that, as the force originally applied along the arrow140is applied farther to the rear with respect to the front leaf spring mount F, greater benefit will be derived from the traction device of the present invention. This positioning towards the rear may be accomplished by a selected installation of the rocker subassembly84, extending the distance between rocker head100and the pivot location (nut-bolt assembly120), or a combination of the two.

During installation of the improved traction device20of the present invention, it is possible to pre-load either wheel W by initially adjusting the front rocker support assembly82so the rocker head100is forced against the lower surface40of the leaf spring L while the vehicle is stopped. Moreover, selective adjustment of left and right traction devices can adjust for traction differences between the left wheel and the right wheel of a vehicle.

From the foregoing, it will be understood by persons skilled in the art that an improved traction device has been provided. The invention is relatively simple and easy to manufacture, yet affords a variety of uses. While the description contains many specifics, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. The foregoing is considered as illustrative only of the principles of the invention. Further, because numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and numerous changes in the details of construction and combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.