Non-linear spring rate sway bar bushing

This invention relates in general to article support members and deals more particularly with an improved elastomeric sway bar bushing for supporting a sway bar and controlling motion of the bar in response to applied force.

Heretofore elastomeric bushings of various designs have been employed to support a sway bar and control motion of the bar. Where a vehicle or apparatus in which a sway bar is employed is subjected to relatively light impact loads linear sway bar displacement in response to impact may be acceptable. However, where large impact loads are encountered, as, for example, in a sway bar for a skip car for receiving and transporting heavy loads of rock or ore in a quarry. A bushing which provides a greater degree of energy absorption in response to large impact loads is required.

Accordingly, it is the general aim of the present invention to provide an elastomeric sway bar bushing which has a non-linear spring rate which enables disproportionately large sway bar displacements for improved energy absorption of large impact loads.

In accordance with the present invention a non-linear spring rate sway bar bushing comprises a unitary bushing member formed from resilient elastomeric material and having an axially elongated tubular inner portion defining a bore extending axially therethrough for receiving and containing a portion of a sway bar therein. An elongated outer portion of the bushing member is supported in radially outwardly spaced relation to the inner portion by radially extending ribs angularly spaced about the axis of the bore and integrally connected to and extending between the inner portion and the outer portion and maintaining the inner portion in radially inwardly spaced relation to the outer portion.

FIG. 1 is a transverse sectional view through a non-linear spring weight sway bar bunching embodying the present invention.

FIG. 2 is a perspective view of the bushing shown in FIG. 1 illustrating an application thereof.

FIG. 3 is a sectional view taken generally along the line 3 — 3 of FIG. 1 .

FIG. 4 is a load vs. deflection graft of the application shown in FIG. 2 .

Turning now to the drawing and referring first particularly to FIGS. 1 and 2, a non-linear spring rate sway bar bushing embodying the present invention is indicated generally by the reference numeral 10 . The illustrated sway bar bushing 10 essentially comprises a unitary bushing member molded or otherwise formed from a resilient elastomeric material, such as a rubber compound, and includes an axially elongated tubular inner portion 12 which has a bore 14 extending axially through it for receiving and containing a portion of a sway bar therein. The bushing 10 further includes an elongated outer portion 16 . A plurality of radially extending ribs 18 , 18 angularly spaced about the axis of the bore 14 and integrally connected to and extending between the inner portion 12 and the outer portion 16 maintain the inner portion in radially inwardly spaced relation to the outer portion. Considering now the sway bar bushing in further detail, the illustrated bushing member 10 is preferably made from an elastomeric material of substantially uniform thickness. The inner and outer portions 12 and 16 are preferably generally cylindrical tubular portions maintained in coaxial alignment with each other by the ribs or spokes 18 , 18 which are angularly spaced about the central axis of the bore 14 . The bore is also generally cylindrical to receive and retain a complementary cylindrical portion of a sway bar, such as the bar shown in FIG. 2 and indicated generally by the letter B.

In accordance with presently preferred construction, the sway bar bushing 10 has four equiangularly spaced apart and radially extending ribs or spokes 18 , 18 .

Preferably, and as shown, the inner portion 12 and the outer portion 16 are of substantially identical axial length, the inner portion being wholly disposed within the outer portion of the bushing. The ribs 18 , 18 are integrally connected to the inner and outer portions 12 and 16 along the entire lengths of the inner and outer portions.

A typical application of the bushing 10 is shown in FIG. 2 . The outer part 16 is mounted in a fixed position relative to a part of an apparatus (not shown) to support and control movement of an associated portion of the sway bar B which is connected to another part of the aforementioned apparatus. As illustrated, the sway bar B is generally constrained within the apparatus to move in the direction indicated by the directional arrows F, F in response to an impact force acting upon the apparatus. The preferred geometry and mounting arrangement of the bushing 10 is such that sway bar movement occurs generally within a diametric plane of the cylindrical bushing which plane bisects the angles between the equiangularly spaced apart spokes at diametrically opposite sides of the sway bar bushing. In FIG. 2 the spokes at one side of the bushing are indicated at 18 , 18 , whereas the spokes at the diametrically opposite sides are indicated at 18 ′, 18 ′.

When the apparatus (not shown) is subjected to an impact force which causes the sway bar B to move in the direction of the arrows F, F in FIG. 2 the spokes 18 ′, 18 ′ will be subjected to compressive force whereas the spokes 18 , 18 will be in tension. It should be apparent that the spokes will undergo a change in angular relationship relative to each other. This change in the angular relationship between the spokes causes a non-linear spring rate to develop within the bushing acting upon the sway bar B. The resulting deflection of the bar in response to an increasing impact load is graphically illustrated in the graph shown in FIG. 4 .