Leaf spring eye wrap scarf gap cover component

Details Leaf spring eye wrap scarf gap cover component Leaf spring eye wrap scarf gap cover component

2000-08-08

2003-08-05

Schwartz, Christopher P. (Department: 3683)

Spring devices

Vehicle

Leaf

C267S268000

Reexamination Certificate

active

06601836

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to vehicle suspension system components and more particularly to a new component used in association with a leaf spring of the type typically included in vehicle suspension systems.
BACKGROUND OF THE INVENTION
Leaf springs are components used in a variety of vehicle suspension systems. As an example, leaf springs are used on most heavy-duty truck suspensions as a component thereof. Leaf springs are used to support the load of the vehicle and typically connect at opposite ends of the conventional C-shaped frame rail extending longitudinally on one side of the vehicle. Typically, a similar spring is incorporated for connection with the C-shaped frame rail positioned on the opposite side of the vehicle. The leaf springs are connected to the rails through frame hangers at pivot points that control the articulation of the suspension.
Leaf springs ordinarily connect to the frame rails at their opposing ends by way of an end wrap, or eye, of the leaf spring that accepts a bushing adapted to permit such fastening. Traditionally, leaf spring bushings include a rubber core that is confined by an outer metal sleeve. Such bushings conventionally have three layers, including an inner metal sleeve. The bushings are typically installed or assembled into each eye located at opposite ends of the leaf spring to permit connection with the frame hangers.
Use of traditional bushings having an outer metal sleeve to connect the leaf springs to the frame hangers has at least two notable drawbacks. First, the cost associated with manufacture and assembly of the bushing increases when an outer metal sleeve is incorporated therein. Second, bushings having an outer metal sleeve typically do not fit as well within the eye of the leaf spring in that the generally perfectly round outer metal “rocks” within the inconsistent inner diameter of the leaf spring eye wrap. In an extreme case, the rocking action of the bushing during leaf spring deflection resulting from suspension system articulation can cause the bushing to walk out of the leaf spring eye wrap, creating hazardous conditions.
These drawbacks associated with use of traditional bushings having an outer metal sleeve have led to the development of a sleeveless bushing. Sleeveless bushings eliminate the outer metal sleeve and thereby reduce the costs associated with the manufacture and assembly of the bushings. Further, sleeveless bushings provide for a consistent fit within the leaf spring eye wrap as they are permitted to flow within the wrap to achieve the desired confinement required for adequate fatigue resistance.
One foreseeable drawback of sleeveless bushings for use within leaf spring eye wraps is attributed to the construction of conventional leaf spring eye wraps.
FIG. 1
illustrates an end of a leaf spring
20
of the type typically used in vehicle suspension systems. As shown, the end of the leaf spring includes an eye wrap
22
that is formed by encircling the end of the leaf spring back onto itself.
The eye wrap
22
is generally circular, but typically not perfectly circular, and includes an inner diameter and an outer diameter radially spaced from each other by the thickness of leaf spring
20
at its end. The inner diameter of leaf spring
20
can be defined as beginning at an inner diameter beginning line
24
, extending along the top surface of leaf spring
20
, and ending at an inner diameter end line
26
positioned on the top surface of the leaf spring and coincident with one boundary of leaf spring end
28
. The inner diameter is defined entirely by the top surface of leaf spring
20
. The outer diameter of leaf spring
20
can be defined as beginning at an outer diameter beginning line
30
positioned on the top surface of the leaf spring, extending across the thickness of leaf spring
20
and along the bottom surface of the leaf spring up to and including an outer diameter end line
32
positioned on the bottom surface of the leaf spring and coincident with a boundary of leaf spring end
28
.
As shown, a gap
34
, referred to as a scarf gap by those skilled in the art, is included in the construction of a conventional leaf spring used in suspension systems. Gap
34
is defined by the space between the end
28
of leaf spring
20
and that portion of the top surface of the leaf spring closely positioned in opposed relationship thereto. In particular, the gap
34
is bounded by inner diameter beginning point
24
, inner diameter end line
26
, outer diameter end line
32
and outer diameter beginning line
30
.
Because the inner diameter of leaf spring
20
is not entirely continuous but rather includes gap
34
, a sharp edge that presents a potential problem for the use of sleeveless bushings is formed at inner diameter end line
26
. With traditional bushings, the outer metal sleeve protects the rubber inner or middle core from being torn during assembly and worn during suspension articulation. Accordingly, no additional barrier need be placed between the scarf gap and the bushing when a traditional bushing having an outer metal sleeve is installed or assembled in the leaf spring eye wrap.
With sleeveless bushings, however, the sharp edge can tear the unprotected rubber body of the bushing during installation within the leaf spring eye wrap and also wear down the bushing during suspension articulation.
FIG. 2
illustrates a sleeveless bushing
36
having an elastomeric body
38
and a bore
40
extending longitudinally through it. As shown, sleeveless bushing
36
includes opposing end flange portions
42
,
44
for providing a proper fit within the eye wrap
22
of leaf spring
20
(
FIG. 1
) and for preventing walking out during leaf spring deflection. In the illustrated embodiment, sleeveless bushing
36
has a spool-like shape.
In the past, to prevent the wear caused by a scarf gap on a sleeveless bushing during suspension articulation, fiber-reinforced tape in combination with an electrical tape has been used to cover the scarf gap and thereby protect the bushing. Until the present invention, the only alternative has been to leave the bushing unprotected and sacrifice its field life.
FIG. 3
illustrates the former method. As shown, a tape combination
46
, which includes fiber-reinforced tape in combination with electrical tape, covers the sharp edge created by the gap
34
(see
FIG. 1
) positioned at the end of the leaf spring eye wrap
22
. Although this method is more desirable than leaving the elastomeric body
38
of a sleeveless bushing
36
(
FIG. 2
) unprotected, it has considerable drawbacks. Among others, using tape, such as tape combination
46
, to cover the scarf gap is an inefficient method of manufacture. Preparing the scarf gap with tape is an arduous task. Also, the tape itself ordinarily wears as a result of suspension articulation, resulting in the sleeveless bushing being effectively left without protection from the scarf gap.
In light of the foregoing, it is desirable to design a suspension system component that will provide a barrier between the scarf gap formed by a leaf spring eye wrap and a sleeveless bushing assembled therein to provide a method of fastening the leaf spring to a conventional frame hanger.
It is also desirable to design a suspension system component that minimizes the risk of tearing sleeveless bushings when such bushings are assembled in the leaf spring eye wrap of a suspension system leaf spring.
It is still yet desirable to design a suspension system component that minimizes the risk of wearing sleeveless bushings assembled in the leaf spring eye wrap of a suspension system leaf spring during deflection of the leaf spring.
It is further desirable to design a suspension system component that enables use of a sleeveless bushing that replaces traditional bushings having an outer metal sleeve, thereby reducing the cost associated with the suspension system.
It is yet further desirable to design a suspension system component that provides for an effective method of manufacture and eliminates the arduous task of prepar

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