GB2088522A - Energy absorbing device - Google Patents

Abstract

A device is disclosed for absorbing linear, mechanical energy. A cylindrical rod (24) with a penetrator (26) is in contact with an elastomeric rod (16) contained within a retaining cylinder (10). The elastomeric rod has a frusto-conical end (20). When low energy is applied to the cylindrical rod, the elastomeric rod expands at the frusto-conical surface thus absorbing and returning the low energy. When high energy is applied to the cylindrical rod, the penetrator shears the elastomeric rod, thus absorbing the high energy (Fig. 3). <IMAGE>

Description

SPECIFICATION Energy absorbing device The present invention relates to an energy absorbing device of the type which is particularly adapted to absorb the impact of a moving body especially linear motions of a moving body. In particular, the present invention is concerned with an energy absorbing device that can in one mode adsorb low energy forces and restore them and in another mode absorb high energy forces.

The prior art reaches several different energy absorbing devices such as in U. S. Patent Nos.

3,583,530,3,804,446 and 3,847,252. Many of the energy absorbing devices taught in the prior art have employed inflated bags, spring loaded pistons, and cylinder assemblies, and combinations of said bags, pistons and cylinder assemblies. Such prior art devices have performed well as energy absorbing devices in either a high impact mode or in a low impact mode but have not been able to function well in both modes. U. S. Patent 3,913,707 discloses a device which has a two-mode operation but in essence requires two separate functional means to accomplish this result, i.e. a porous metal body for absorbing high impacts and a spring loaded bumper to absorb low impacts. U. S.Patent 3,752,462 to Wright, assigned to the same assignee as the present invention, discloses an elastomeric spring and frictional dampening shock absorber which deforms an elastomeric material within a confined housing. The Wright Patent works well for specific applications of energy within a desired performance criteria; however, the device contemplates the return of all energy forces, regardless of the level.

Objects ofthe invention An object of the present invention is to provide an energy absorbing device that will overcome the difficulties and disadvantages of the prior art devices.

Another object of the present invention is to provide an energy absorbing device in a single configuration that will absorb and restore low energy impact forces and will absorb high energy impact forces.

Summary ofthe invention The energy absorbing device according to the present invention comprises a housing, an elastomeric rod having a frusto-conical surface contained within the housing, a transmission member having a penetrator and a bearing to seal the transmission member and the housing. The penetrator is in engagement with the elastomeric rod. Low impact forces applied against the end of the transmission member force the elastomeric rod to deform along the frusto-conical surface and thus absorb the low energy forces. Application of high energy forces upon the transmission member will cause the penetratorto shear the elastomeric rod causing an effective viscous flow of the elastomeric material around the penetrator, thus absorbing the high energy force.

Description ofthe drawings Figure 1 is a sectional view of the device according to the present invention; Figure 2 is a sectional view of the device according to Figure 1, in which a low energy force is applied to the end of the transmission member; Figure 3 is a sectional view of the embodiment of the invention shown in Figure 1, in which a high energy force is applied to the end of the transmis sion member; Figure 4 is a graphical representation of typical load versus deflection characteristics of the invention; Figure 5 is an enlarged view of the bearing/seal portion of the embodiment shown in Figure 1; Figure 6 is an enlargment of the penetrator for a different embodiment of the present invention, and Figure 7 shows a further embodiment of the present invention in which a guide for the penetrator is depicted.

Description of the preferred embodiments A description of the invention follows, referring to the drawings in which like reference numerals denote like elements of structure in each of the several Figures.

As shown in the accompanying drawings, the present invention comprises a housing 10 having a closed end 12 and an open end 14. An elastomeric rod 16 is contained within the inner walls 18 of housing 10. The elastomeric rod 16 is preferably dimensioned so as to fit snugly within the inner walls 18 of housing 10. The elastomeric rod 16 has a frusto-conical surface 20 which radially declines towards opening 14 of housing 10 and has an end surface 22.

A transmission member 24, referablya rigid rod, having a penetrator 26, preferably conical in shape, extends through opening 14 of housing 10. The penetrator 26 can either be fixedly attached to transmiussion member 24 or may be an integral part thereof. The penetrator 26 preferably extends partially into elastomeric member 16 so that there is an initial, partial penetration of the elastomeric member 16 by penetrator 26 in an unloaded condition of transmission member 24. The transmission member 24 is held in a lateral position with respect to housing 10 by a bearing member 28 which axially surrounds transmission member 24 and fits snugly within the housing 10, yet permitting longitudinal motion of the transmission member 24.In another embodiment of the present invention, depicted in Figure 5, the housing 10 can have a radially declining surface 30 to better aid in holding the bearing member 28 against the transmission member 24.

A no-load condition is depicted in Figure 1 wherein the penetrator 26 is in intimate contact with the elastomeric rod 16 and preferably engaged in a partial penetration therewith. When low energy force is transmitted to the end of transmission member 24, such as would occur in a minor impact with a linearly moving object, the elastomeric rod 16 will swell and fill the air gaps or space caused by the frusto-conical surface 20 of elastomeric rod 16. Since the elastomeric rod 16 swells, no further penetration of elastomeric rod 16 occurs by penetrator 26. The result of this elastomeric swelling on low impact means that the low energy force will be returned, i.e.

the transmission member 24 will return to its original longitudinal position with respect to the housing 10.

Upon application of high energy forces to the end of transmission member 24, as depicted in Figure 3, there will be an initial swelling of elastomeric rod 16 which will fill the air gaps caused by frusto-conical surface 20 as was described above. However, penetration of elastomeric rod 16 by penetrator 26 will occurforthat energy greater than that required to permit complete swelling and filling of the air gaps.

This penetration of elastomeric rod 16 by penetrator 26 causes localized shearing of the elastomeric rod and effective viscous flow. The elastomeric material flows over the penetrator, thus creating additional retarding forces.

Atypical load versus deflection graph is illustrated in Figure 4 for a low energy force and for a high energy force. The X or horizontal axis of the graph represents deflection of the transmission member 24 and the Y or vertical axis represents the energy force applied to the end of the transmission member 24.

Low energy forces follow the curve from point "0" to "A" and then back to "O". All the energy is absorbed and the device is completely self-restored.

High energy forces follow the path from 0 to A which represents the swelling of the elastomeric rod 16 due to frusto-conical surface 20 and then proceeds to point B and would return along the curve C if no further load were applied to the end of the transmission member 24. If additional energy were applied to the end of the transmission member 24, i.e. an energy greater than curve at point B, the deflection would continue to move to a new point D until all the energy is absorbed. Once the energy is removed from the end of the transmission member 24, the member would return to a position along path E.

For the sake of simplicity the penetrator and transmission member have been shown as a conical tipped rod. The present invention also contemplates the use of a pyramid shaped point with three or more sides. The sides may either be flat, convex or concave based upon the desired load capacity and elastomer shear specifications. As is shown in Figure 6, the conical tip 26' may have edges or surfaces in contactwiththe housing inner surface 18to provide axial stability during penetration and installation.

Another embodiment of the present invention contemplates the use of a drift nose cone penetrator as shown in Figure 7. The purpose of this drift nose cone is to provide additional axial stability during penetration. The channel 32 within elastomeric rod 16 provides the guidance for the penetrator 26".

Although this invention has been described with respect to a preferred embodiment in which the elastomeric rod 16 has a frusto-conical surface 20, the invention contemplates another embodiment in which the elastomeric rod fills the housing 10 completely to some specific depth such that the device will only be used for high energy impacts, i.e.

any force applied to the end of transmission member 24 will cause shearing of the elastomeric rod 16 and no restoration will occur upon removal of the force.

This invention has been described with reference to preferred embodiments. Obvious modifications and alterations will occur to others upon reading and understanding the specification. The intention is to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalent thereof.

Claims (7)

1. A device for absorbing mechanical energy, said device comprising: a housing having one open end; an elastomeric rod located within said housing, said elastomeric rod having an end surface facing said open end of said housing; a penetrator located within said housing and in contact with said end of said elastomeric rod; a transmission member in communication with said penetrator and extending through said opening in said housing for transmitting external, mechanical energy to said penetrator so that said penetrator will shear said elastomeric rod, thus absorbing the external energy.

2. A device for absorbing mechanical energy, said device comprising: a housing having one open end; an elastomeric rod located within said housing, said elastomeric rod having a frusto-conical surface facing said open end of said housing; a penetrator located within said housing and in contact with said frusto-conical surface of said elastomeric rod; and a transmission member in communication with said penetrator and extending through said opening in said housing for transmitting external, mechanical energy to said penetrator so that low mechanical energy will cause the elastomeric rod to expand at the frusto-conical surface to absorb said low mechanical energy and return said transmission member to an original position upon removal of said low mechanical energy and so that high mechanical energy will cause said penetrator to shear said elastomeric rod causing effective viscous flow, thus absorbing said high mechanical energy.

3. The device of Claim 1 or 2 further comprising a bearing seal located the said open end of said housing and surrounding said transmission member so that the inside of said housing is sealed from the outside atmosphere.

4. The device of Claim 1 or 2 in which said penetrator is dimensioned so as to have a conical surface to aid in directing the penetration upon application of sufficient energy to said transmission member.

5. The device of Claim 1 or 2 in which said penetrator is integrally attached to said transmission member.

6. The device of Claim 1 or 2 in which said elastomeric rod has a channel with a longitudinal axis in line with said transmission member, and in which said penetrator is a drift nose cone, to aid said penetrator to remain in the same lateral position relative to said housing when shearing of said elastomeric rod occurs.

7. A device for absorbing mechanical energy, substantially as hereinbefore described with reference to the accompanying drawings.