GB2043828A

GB2043828A - Thermoplastic Mountings

Info

Publication number: GB2043828A
Application number: GB8002090A
Authority: GB
Original assignee: Barry Wright Corp
Current assignee: Hutchinson Aerospace and Industry Inc
Priority date: 1979-03-05
Filing date: 1980-01-22
Publication date: 1980-10-08
Also published as: DE3005161A1; FR2450682A1; IT1146113B; IL59204A0; IT8047927A0

Abstract

A thermoplastic shock and vibration-absorbing mounting of a structural configuration which provides equal spring rates in three orthogonal directions comprises end members (10, 12) and a hemispherical concavo-convex wall (14) connecting the two which is provided with slots 24 defined by ribs 22. <IMAGE>

Description

SPECIFICATION Thermoplastic Mountings Mountings designed to isolate vibration, shock and the like for machinery, structural supporting members, instruments and the like are old in the art. Most such devices provide for absorbing shock in three orthogonal directions. Vibration isolators or absorbers comprise wholly or partly of an elastomer are disclosed in such United States patents as Stewart 3,350,042; Henley 3,305,227; Schwartz 2,766,163; Skala 3,721,417: and the Johnson Patents 3,288,405; 3,337,167; and 3,417,950.

Although the aforesaid patents provide structure in which shock and vibration are absorbed orthogonally, that is, along X, Y and Z axes, their configuration and mounting is such that they do not provide for large excursion in both axial and radial directions and do not permit equal spring rates in three orthogonal directions.

It is an object of this invention to provide a structure which differs from any of the structures shown in the foregoing patents in that it is capable of providing approximately equal spring rates in three orthogonal directions, a structure which is simple and a structure which can be made of an elastomer and inexpensively molded in quantity at a very low cost per part.

The present invention provides a thermoplastic mounting comprising relatively rigid end members and intermediate said end members a fluted structure.

As herein iilustrated, a thermoplastic mounting (preferably having elastomeric properties) embodying this invention is structured to provide for equal spring rates in three orthogonal directions and, for this purpose, comprises relatively rigid end members and intermediate said end members and integrally formed therewith, a hemispherical concavo-convex wall structure of circular right section perpendicular to the axis of the end members, which wail is fluted axially with respect to the centers of said end members. The fluted structure defines peripherally of the axis a plurality of c;rcularly- arranged ribs connected at their opposite ends to the end members, each of which is of substantially uniform width lengthwise and each of which is concavo-convex.The end members comprise a hub of circular right section at one end and a substantially rectangular panel-like flange at the other end containing a circular opening of larger diameter than the diameter of the hub. The ends of the ribs are at one end integral with the peripheral edge of the hub and spaced at equal distances about the axis of the hub and the ends of the ribs at the other end are integral with the face of the flange and spaced equally about the center circular opening therein. The ribs between the end members are symmetrically arranged in a circle about the axis and are concavo-convex. The hub contains a center opening and defines a planar surface perpendicular to the axis of the structure and the flange contains symmetrically arranged openings at its corners and defines a planar end surface perpendicular to the axis of the structure.There are symmetrically arranged stiffening ribs, one at each edge of the flange.

By way of example only, an illustrative embodiment of the invention will now be described with reference to the accompanying drawings, wherein: Fig. 1 is a plan view of one side of a thermoplastic mounting constructed according to this invention with portions thereof broken away and in section; Fig. 2 is a fragmentary plan view of the other side of the thermoplastic mounting; Fig. 3 is a section taken on the line 3-3 of Fig.

1;and Fig. 4 is a section taken on the line 4-4 of Fig.

1.

Referring to the drawings, Fig. 2, a thermoplastic mounting embodying this invention comprises end parts 10 and 12 symmetrical with respect to a common axis X-X and intermediate the end parts a part 14 which is structured to provide for relatively large excursions in both axial and radial directions and which permits equal spring rates in three orthogonal directions. The end parts provide for connecting two structures where it is desirable to prevent vibration and shock from being transmitted from one part to the other.The end part 10 is of circular right section and contains an axial opening 1 6 centered with respect to the axis X-X. The end part 12 is of rectangular configuration and contains a circular opening 18 and openings 20, the axes of which are spaced from and parallel to the axis X-X.

The part 14 is fluted, the flutes defining peripherally-spaced ribs 22 spaced at equal distances apart about the axis X-X. The ribs 22 are of uniform width lengthwise and are integrally connected at their opposite ends to the end members at different radial distances from the axis of the end members respectively to the periphery of the end part 10 and to the face of the end part 12 peripherally of the opening 16. The ribs 22 are concavo-convex spaced at equal distances apart peripherally and define the flutes or openings 24 between ribs which are somewhat triangular in configuration tapering from a maximum base width 24a at the end part 12 to a minimum apex width 24b at the end part 10.This fluted structure provides for substantially equal spring rates in three orthogonal directions so as to permit torsion and circumferential bending of the structural member.

The structure comprising the end parts 10 and 12 and fluted wall 14 are comprised of thermoplastic, for example, a thermoplastic such as polyvinyl chloride. Other suitable thermoplastics for use herein would include other vinyls, acrylics, polyethylenes, nylons and fluoro carbons.

As shown in the drawings, the end parts 10 and 12 have planar surfaces 26 and 28 perpendicular to the axis X-X for attachment to parts to be isolated from each other. The axial thickness of the end part exceeds the thickness of the end of the ribs joined thereto so that the outer plane surface 26 extends outwardly from the end of the ribs and the inner plane surface 27 extends inwardly of the end of the ribs. The end of the ribs at the juncture with the hub are filleted. The axial thickness of the end part 1 2 is approximately half that of the hub and is stiffened at its rear (inner) side along each of its four edges by a reinforcing rib 30.

The mounting has the important characteristics that approximately equal spring rates in three orthogonal directions are achieved by fluting the plastic material to permit torsional and circumferential bending of the flexural members and that the wholly plastics material structure enables mass-production molding at very small costs per unit. Variations in the spring rates may be achieved by changing the plastics material or by minor changes in the mounting dimensions.

Claims

1. A thermoplastic mounting comprising relatively rigid end members and intermediate said end members a fluted structure.

2. A mounting according to claim 1 wherein said end members define planar surfaces substantially perpendicular to orthogonal directions.

3. A mounting according to claim 1 or 2 wherein the fluted structure is spherically concavo-convex and symmetrical with respect to the axis defined by the centers of the end members.

4. A mounting according to any preceding claim wherein the fluted part is structured spherically so as to yield at substantially equal rates orthogonally.

5. A mounting according to any preceding claim having spaced end elements and an intermediate, integrally-formed, hemispherical wall fluted so as to yield at substantially equal rates in three orthogonal directions.

6. A mounting according to any preceding claim comprising end members and a fluted wall connecting said end members defining circumferentially-spaced ribs which are concavoconvex and which diverge from one end member to the other and are uniformly spaced about the axis of the end members about circles of different radius and a hub.

7. A mounting according to claim 6 wherein the hub, wall and end members comprise an integral structure.

8. A mounting according to any preceding claim comprising relatively rigid end members and intermediate the end members a plurality of ribs spaced at equal distances about the axis defined by the centers of the end members with flutes therebetween, said end members being so disposed about the end members that the ribs are disposed in a hemispherical array.

9. A mounting according to any preceding claim comprising relatively rigid end members and intermediate the end members a plurality of elongate ribs spaced equally about the axis defined by the centers of the end members at different radial distances from the centers of the end members, with spaces between adjacent ribs, said ribs being attached at their ends to the end members and being concavo-convex therebetween.

1 0. A mounting according to claim 9 wherein the concavo-convex configuration of the ribs is hemispherical, wherein the ribs are of equal width lengthwise, and wherein the openings defined by the ribs taper from a maximum width at one end to a minimum width at the other end.

11. A thermoplastic mounting substantially as herein described with reference to and as illustrated by the accompanying drawings.