US3819167A

US3819167A - Buffering device

Info

Publication number: US3819167A
Application number: US00306835A
Authority: US
Inventors: K Nakamura; H Yamazaki; Y Kondo
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 1971-11-17
Filing date: 1972-11-15
Publication date: 1974-06-25
Anticipated expiration: 1991-06-25
Also published as: CA960236A; JPS5122578B2; JPS4857077A

Abstract

A buffering device for protecting a body, comprising an impactreceiving plate carrying a hollow resilient cylindrical buffering member, a core shaft coaxially secured to the impact-receiving plate, an intermediate hollow shaft extending from the body into the space between the buffering member and the core shaft, and an elastomeric filler secured to the core shaft and the intermediate shaft so as to fill the space therebetween. The opposite end of the buffering member to the shock-receiving plate is secured to the intermediate shaft.

Description

United States Patent [191 Nakamura et al.

[ 1 June 25, 1974 BUFFERING DEVICE Inventors: Kihei Nakamura, Yokohama;

Harumichi Yamazaki; Yoshikazu Kondo, both of Tokyo, all of Japan Bridgestone Tire Company Limited, Tokyo, Japan Filed: Nov. 15, 1972 Appl. No.: 306,835

Assignee:

Foreign Application Priority Data Nov. 17, 1971 Japan 46-91466 3,412,990 11/1968 Gladstone ..267/35 Primary Examiner-James B. Marbert Attorney, Agent, or Firm-Fleit, Gipple & Jacobson hollow shaft extending from the body into the space U.S. Cl. 267/139, 267/35 Int. Cl F16f 7/12 Field of Search 267/35, 33, 63 A, 139,

References Cited UNITED STATES PATENTS 10/1954 Dentler 267/63 A between the buffering member and the core shaft, and an elastomeric filler secured to the core shaft and the intermediate shaft so as to fill the space therebetween. The opposite end of the buffering member to the shock-receiving plate is secured to the intermediate shaft.

5 Claims, 3 Drawing Figures PATENIEDJUN25I974 3.819.167

SHEET 2 BF 3 Load F lexure BUFFERING DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention:

This invention relates to a buffering device, and more particularly to a buffering device which is suitable for use in an automobile, a ship, or a machine for protection thereof by absorbing impact load thereto, such as collision impact.

2. Description of the Prior Art:

There are a variety of buffering devices which use resilient rubber or metallic springs. Most of the conventional buffering devices, however, absorb only a comparatively small amount of impact energy, and if one tries to absorb a large amount of impact energy with a buffering device of conventional structure, the buffering device becomes bulky. It is difficult to install a bulky buffering device in a limited space, such as in an automobile.

Conventional buffering device also has a shortcoming in that the amount of energy absorbed thereby heavily depends on the angle at which an impact is applied to the buffering device. More particularly, if the impact is applied to a conventional buffering device in a direction which is greatly deviated from a direction of compressive axis of the device, or if the impact is a concentrated load which is applied to the buffering device at a point greatly offset from the compressive axis thereof, the amount of the impact energy absorbed by the buffering device is drastically reduced.

Therefore, an object of the present invention is to obviate the aforesaid difficulties of the conventional buffering devices by providing an improved bufiering device.

SUMMARY OF THE INVENTION According to the present invention, there is provided a buffering device, which comprises a cylindrical buffering member having one end secured to an impactreceiving plate, an intermediate shaft having one end secured to a body to be protected, the free end of the buffering member being coaxially secured to the outer peripheral surface of the intermediate shaft, a core shaft coaxially extending through the inside of the intermediate shaft and having one end thereof secured to the impact-receiving plate, and an elastomeric filler secured to the core shaft and the intermediate shaft so as to fill a space therebetween. Whereby, impact energy applied to the impact-receiving plate is absorbed in a dual fashion, i.e., at the inside and the outside of the intermediate shaft.

The buffering device of the aforesaid structure according to the present invention has two impactabsorbing elements; namely, an inner element formed by the core shaft connected to the impact-receiving plate and the intermediate shaft connected to the body being protected with the elastomeric tiller connecting the two shafts, and an outer element formed by the cylindrical buffering member having one end connected tothe impact-receiving plate and the opposite end connected to the pheripheral surface of the intermediate shaft.

With the aforesaid structure according to the present invention, the compressive axis of the buffering device, along which the buffering device contracts upon application of an impact to the body at the impact-receiving plate, apparently coincides with the common axis of the coaxial core shaft, intermediate shaft, and buffering member. The use of the aforesaid two impactabsorbing elements ensures a high energy absorption by the buffering device, even when the impact is applied to the impact-receiving plate in an angular relation to the aforesaid compressive axis or when an impact is applied to the impact-receiving plate at a position which is offset from the compressive axis by a comparatively large distance.

In a preferred embodiment of the present invention, the buffering member is made of a hollow rubber-like resilient cylinder having a comparatively large impact energy absorbing capacity, so that the core shaft and the intermediate shaft may fit in the hollow space of the buffering member in a coaxial fashion. The elastomeric filler for connecting the core shaft to the intermediate shaft is preferably made of high-grade rubber, for instance, it is made of soft rubber having an elongation of not smaller than 500 percent at breakdown.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of the invention, reference is made to the accompanying drawings, in which:

FIG. 1 is a schematic longitudinal sectional view of a buffering device according to the present invention;

FIG. 2 is a graph showing the load-flexure characteristics of the buffering device of FIG. 1; and

FIG. 3 is a schematic longitudinal sectional view of another buffering device according to the present invention.

Like parts are designated by like numerals and symbols throughout the different figures of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a hollow cylindrical buffering member 1, e.g., a resilient rubber cylinder with a hard ness of 40 to 98 according to Japanese Industrial Standard (118) K 6301, is secured to an impactreceiving plate 9, and a bush-type buffering assembly 2 is coaxially disposed in the hollow space of the buffering member 1. The common longitudinal central axis of the buffering member 1 and the bush-type buffering as sembly 2 is represented by a line X-X in the figure. The bush-type buffering assembly 2 includes a metallic core shaft or cylinder 3 with a circular or rectangular cross section and an outer shaft or cylinder 4 which telescopically receives the core cylinder 3 with a suitable spacing therefrom. A resilient. filler 5, which is, for instance, made of soft rubber having an elongation of not smaller than 500 percent at breakdown and a modulus of elasticity of 30 Kg/cm at 300 percent elongation, is fitted in the spacing between the core cylinder 3 and the outer cylinder 4. The opposing surfaces of the filler 5 are fastly bonded to the inner peripheral surface of the outer cylinder 4 and the outer peripheral surface of the core cylinder 3, respectively. One end of the core cylinder 3 is secured to the impact-receiving plate 9, and a long bolt 6 extends from the opposite end of the core cylinder 3 to that end of the outer cylinder 4 which faces said opposite end of the core cylinder 3. A nut 7 threadedly engages the long bolt 6 at the outside of the outer cylinder 4, relative to the core cylinder 3, so as to interconnect the two

cylinders

3 and 4. Such interconnection by the long bolt 6 and the nut 7, however, is not essential to the buffering device of the present invention. For instance, the bolt 6 and the nut 7 may be dispensed with, if the tiller keeps the two

cylinders

3 and 4 in proper alignment with each other. The nut connected end of the outer cylinder 4 is secured to a body to be protected, such as an automobile chas- In the embodiment, as shown in FIG. 1, the outer cylinder 4 is of unitary construction. Alternately, it is possible to form the outer cylinder 4 with a plurality of separate elements, so as to guide the core cylinder 3 while holding the tiller 5 against impact load applied thereto.

To operatively connect the cylindrical buffering member 1 to the bush-type buffering assembly 2, a connecting member or flange 8 is secured to the opposite end of the buffering member 1 to the impact-receiving plate 9. The flange 8 is secured to the outer cylinder 4 by a suitable means, e.g., by welding.

In operation, let is be assumed that a load F is applied to the impact-receiving plate 9 in alignment with the longitudinal axis XX of the buffering device. As a result, the cylindrical buffering member 1 is compressed,

because the impact-receiving plate 9 is forced toward the fixed flange 8. If the outer diameter d of the buffering member 1 is represented by d 2r and its inner diameter is represented by 2r the cross sectional area S of the buffering member, which is taken at right angles to the axis XX and surrounded by the outer peripheral surface thereof, is given by S 1 'n-r and the similar cross sectional area of the hollow space S of the buffering member is given by S 111 If a ratio of the outer diameter d of the buffering member 1 to its height h, taken in parallel to the axis XX, is kept constant, the amount of energy to be absorbed by the buffering member 1 in response to its compression depends on the ratio of the aforesaid two areas, namely 8 /8 The ratio of h/d of the buffering member 1 is preferably 0.8 to 1.7, but the invention is not restricted by such range of the h/d ratio.

FIG. 2 shows load-flexure characteristics of the buffering device of the present invention, as shown in FIG. 1. In the figure, the curve a represents such characteristics for the buffering member 1 alone, for the case of a medium S /S ratio of about 1.4 to about 4.0. The curve a represents the similar characteristics for the case of a comparatively large S /S ratio of about 4.0 or larger, while the curve a represents the similar charac' teristics for the case of a comparatively small S 18 ratio of about 1.4 or smaller.

The curve b of FIG. 2 shows the load-flexure characteristics of the tiller 5, in response to the movement of the core cylinder 3 relative to the outer cylinder 4, in the direction of the axis XX. The relative movement of the

cylinders

3 and 4 causes shearing stress in the tiller 5, and the flexure of the curve b is due to such shearing stress. With such flexure, the filler 5 also absorbs the impact energy.

In the buffering device according to the present invention, the buffering member 1 and the bush-type buffering assembly 2 are disposed in a coaxial fashion about the longitudinal axis XX, so that the impact load F applied to the impact-receiving plate 9 is simultaneously borne by both the buffering member 1 and the bush-type buffering assembly 2. Thus, the overall load-flexure characteristics of the buffering device becomes the sum of that of the member I and that of the assembly 2, as shown by the curves c c, and c of FIG. 2.

More particularly, if the buffering member 1 has a comparatively small S,/S ratio of about 1.4 or smaller resulting in the load-flexure characteristics of the curve a of FIG. 2, the overall load-flexure characteristics of the buffering device according to the present invention is given by the summation of that of the curve a and that of the curve b for the tiller 5, as shown by the curve 0 If the 8 /8 ratio of the buffering member 1 is about 1.4 to 4.0, the overall load-flexure characteristics of the buffering device becomes as shown by the curve 0. Similarly, for a large S /S ratio in excess of about 4.0, the overall load-flexure characteristics of the buffering device becomes as shown by the curve c of FIG. 2. Thus, a desired load-flexure characteristics can be selected from the curves of FIG. 2, by properly selecting a suitable configuration of the buffering member 1 and the bush-type buffering assembly 2.

The inventors have found out that the desired loadflexure characteristics can be achieved with a smaller buffering device according to the present invention, as compared with conventional buffering devices. The amount of the impact energy to be absorbed by the buffering device depends on the aforesaid load-flexure characteristics. Thus, with the present invention, a desired impact energy absorption can be achieved with a device of smaller size than that of conventional buffering devices.

In the buffering device of the present invention, as shown in FIG. 1, if an impact load F is applied at an angular relation to the longitudinal axis XX, or if a concentrated load F" is applied to the impact-receiving plate 9 at a point offset from the axis XX, the core cylinder 3 which is surrounded by the resilient filler 5 resists against any swaying of the impact-receiving plate 9 relative to the axis X-X. Whereby, the buffering device of the present invention ensures a high energy absorption for the angularly applied impact load and the offset impact load.

The long bolt 6 carrying the nut 7 acts to guide the displacement of the inner cylinder 3 along the axis XX. In addition to such guiding, the initial loading to the buffering member 1 and the tiller 5 can be adjusted by turning the nut 7 so as to regulate the position of the impact-receiving plate 9 relative to the body 10 being protected. Whereby, the load-flexure characteristics and the energy absorption by the buffering device can be controlled at will.

FIG. 3 illustrates another embodiment of the present invention. If a concentrated impact load F" is applied to an impact-receiving plate 9 at a position which is off set from a longitudinal axis X-X of the buffering device, a bufi'ering member 1 may tend to sway relative to the axis XX, especially when the buffering member 1 has a comparatively low rigidity in the lateral direction as shown by the arrow P. When the buffering member 1 is swayed, the desired load-flexure characteristics and impact absorption, as shown by the curves c, 0 and 0 cannot be achieved. In the embodiment of FIG. 3, two guide pieces 11 and 12 are used to guide the movement of a core cylinder 3 relative to an outer cylinder 4 along the axis X--X. Whereby, the core cylinder 3 and the impact-receiving plate 9 are prevented from the swaying, and the desired compression of the buffering member I and the shearing stress of the filler 5 can be ensured.

The guide pieces 11 and 12, in effect, improve the lateral rigidity of the buffering device, by preventing the impact-receiving plate 9 from swaying relative to the axis X-X. The guide piece 11 is secured to the opposite end of the core cylinder 3 to the impactreceiving plate 9, so as to keep a clearance 11a between the inner peripheral surface of the outer cylinder 4 and the outer peripheral edge of the guide piece 11. The other guide piece 12 has a central hole 12a and is secured to the opposite end of the outer cylinder 4 to a body being protected, while allowing the core cylinder 3 to move through the central hole 12a.

It is, of course, possible to use only one of such guide pieces, i.e., 11 or 12.

As described in the foregoing disclosure, with the structure according to the present invention, a large impact energy absorption can be obtained by a comparatively small buffering device, and the desired energy absorption can be ensured even for angularly applied impact load and concentrated offset load.

We claim:

1. A buffering device comprising a buffering member having one end secured to an impact-receiving plate, an intermediate shaft having one end secured to a body to be protected, the free end of the buffering member being coaxially secured to the outer peripheral surface of the intermediate shaft, 21 core shaft coaxially extending through the inside of the intermediate shaft and having one end thereof secured to the impact-receiving plate, an elastomeric filler secured to the core shaft and the intermediate shaft so as to fill a space therebetween, and guide means connected between the end of the core shaft remote from said impact-receiving plate and the body to be protected, for maintaining a substantially coaxial relationship between said intermediate shaft and said core shaft during impact.

2. A buffering device according to claim 1 wherein said guide means comprises a guide bolt secured to the end of the core shaft opposite from said impactreceiving plate so as to extend into said body through one end of said intermediate shaft, and a nut threadedly engaging said bolt at the outside of said intermediate shaft, whereby the initial relation between said core shaft and said intermediate shaft is controlled by adjusting said nut relative to said bolt.

3. A buffering device according to claim 1 and further comprising a guide piece secured to the end of the core shaft opposite from said impact-receiving plate so as to maintain a small clearance from the inner peripheral surface of said intermediate shaft to said core shaft for guiding the movement of the core shaft relative to the intermediate shaft.

4. A buffering device according to claim 1 and further comprising a guide piece secured to the end of said intermediate shaft opposite from said body, said guide piece having a central hole through which said core shaft moves under guidance of the guide piece.

5. A buffering device according to claim 3 and further comprising a second guide piece secured to the end of said intermediate shaft opposite from said body, said second guide piece having a central hole through which said core shaft moves under guidance of said second guide piece.

Claims

1. A buffering device comprising a buffering member having one end secured to an impact-receiving plate, an intermediate shaft having one end secured to a body to be protected, the free end of the buffering member being coaxially secured to the outer peripheral surface of the intermediate shaft, a core shaft coaxially extending through the inside of the intermediate shaft and having one end thereof secured to the impact-receiving plate, an elastomeric filler secured to the core shaft and the intermediate shaft so as to fill a space therebetween, and guide means connected between the end of the core shaft remote from said impact-receiving plate and the body to be protected, for maintaining a substantially coaxial relationship between said intermediate shaft and said core shaft during impact.

2. A buffering device according to claim 1 wherein said guide means comprises a guide bolt secured to the end of the core shaft opposite from said impact-receiving plate so as to extend into said body through one end of said intermediate shaft, and a nut threadedly engaging said bolt at the outside of said intermediate shaft, whereby the initial relation between said core shaft and said intermediate shaft is controlled by adjusting said nut relative to said bolt.