GB2138491A - Joint Structure - Google Patents

Abstract

A first member (10) of a joint structure is held between parts (14, 15) of a second member which carries a screw-threaded collar (19) which can be used to tighten the parts of the second member onto the first member to restrain relative movement. When the parts 14 and 15 are released by the collar, the first member can pivot relative to the second member. In figures 2, 3 the first member is a ball. <IMAGE>

Description

SPECIFICATION Joint structure This invention relates to a joint structure comprising first and second members which co-operate with each other to restrain relative displacement whilst permitting relative angular movement. Examples of such joint structures include ball joints and clevisjoints.

The invention has been devised for use in dummy human figures used in investigating the forces to which such figures are subjected during simulations of vehicle accidents. In connection with such dummy figures, there is a requirementforjointswhich permit relative angular movement of parts ofthe figures, whilst impeding such angular movement and in which the degree of resistance to relative angular movement of parts ofthefigures can be adjusted.

According tothe invention, there is provided a joint structure comprising first and second members which co-operate with each other to restrain relative dis placementwhilst permitting relative angular movement, wherein a part of the first member is trapped between respective gripping parts ofthe second member and there is provided an adjustable element for urging said gripping parts towards each other.

In ajointstructure in accordance with the invention, the pressure underwhich the gripping parts engage the first member can be adjusted to achieve a selected frictional resistance to relative angular movement of the members.

In the preferred joint structure, said element and the second member have respective screw th reads which are mutually engaged so thatthe element can be adjusted along the thread ofthe second member.

The gripping parts ofthe second member may be formed on respective limbs ofthe second member, each of which is integral with a common stem ofthe second member.

Examples ofthree joint structures embodying the invention will now be described, with reference to the accompanying drawing, wherein: FIGURES 1,2 and 3 illustrate respective ones ofthe joint structures diagrammatically.

Thejointstructure illustrated in Figure 1 comprises a first member 10 and a second member 11 which co-operate with each otherto restrain relativedis- placement but which can undergo relative angular movement about a single axis 12. The member 11 includes a stem 13, which is partly broken away, and from which there extend two substantially parallel limbs 14 and 15 which are spaced slightly from each other. Adjacent to their free ends, the limbs 14 and 15 include respective gripping parts 16 an 17 which present towards each other respective flat, parallel faces. Aslot is defined between those parts of the limbs 14 and 15 which extend from the gripping parts to the stem.

Aflat,terminal portion ofthememberl0is received between the gripping parts 16 and 17 and is connected with the member 11 by a pin 18 which extends through aligned apertures in the gripping parts 16 and 17 and the terminal portion of the member 10. The pin defines the axis 12, is a free sliding fit in the apertures formed in the gripping parts 16 and 17 and is an interference fit in the apertureformed in the member 10 or is otherwise rigidly secured to that member.

Alternatively, the pin may be a part of the member 11 and rigidly secured to one of the gripping parts 16 and 17.

The members 10 and 11 are formed of a plastics material which is resiliently deformable. When each component of the joint structure is in an unstressed condition,the gripping parts 16 and 17 engagethe terminal portion of the member 10 under vary light contact and there is no substantial resistance to relative angular movement ofthe members 10 and 11.

For urging the gripping parts into pressure contact with the member 10, there is provided an adjustable element in the form of a collar 19 mounted on the member 11. The collar is formed with an internal screwthread and a complementary male screwthread isformed on the stem l3adjacenttothelimbs 14 and 15. The male screw thread also extends a partofthe way along each of these limbs.

Between the male screwthread and the gripping parts 16 and 17, each of the limbs 14 and 15 isformed with a part-conical external surface which is engaged by a frusto-conical internal surface 20 ofthe collar 19.

The external surface ofthe collar 19 is knurled or otherwise adapted to be gripped easily bya user. If the collar is screwed along the member 11 in a direction away from the stem 13, the gripping parts 16 and 17 are urged towards each other into pressure contact with the terminal portion ofthe member 10. The pressure can be adjusted by screwing the collar along the member 11. Generally, friction between the screw threads will be sufficient to retain the collar in any position to which it is set by the user. If required, known means may be provided for releasably restraining rotation ofthe collar relative to the member 11.

Thejointstructure of Figure 1 is suitable for use in a dummy human figure, for example as a knee joint.

The joint structures illustrated in Figures 2 and 3 each include parts corresponding to those hereinbefore described with referenceto Figure 1. In Figures2 and 3, such corresponding parts are indicated by like reference numerals with the prefixes 1 and 2 respectively. Exceptforthe differences hereinafter mentioned, the preceding description is deemed to apply to such corresponding parts.

Inthe jointstructure illustrated in Figure 2, the members 110 and 111 are connected for universal movement. The first member 110 has a terminal portion in the form of a ball 121 and the gripping parts 116and1170fthetwolimbs114and1150fthe member 111 have respective part-spherical surfaces which engagethe ball. The gripping parts can be urged into pressure contact with the ball by means of the collar 119, which can be screwed along the member 111.

In thejoint structure illustrated in Figure 3, thefirst member 210 also has a terminal portion 221 in the form of a ball.This ball is received between gripping parts 216 and 217 of the second member 211 and these gripping parts have part-spherical concave surfaces engaged with the ball.

In the joint structure of Figure 3, the second member 211 does not have a pair of limbs with free ends remote from the stem 213. Instead, the gripping parts 216 and 217 are integrally connected with each other atthe stem 213 and at a free end ofthe member 211 remotefrom the stem. When the collar 219 is screwed along the member 211 away from the stem 213, engagement of a frusto-conical surface 220 on the sleeve with the gripping parts 216 and 217 deforms these partssufficientlyto increase the pressure under which they contact the ball 221. Such deformation is permitted by the slot 222 which extends from the ball 221 to the stem 213.

In each ofthe embodiments illustrated, the components can readily be formed of plastics materials and thejointstructures can be used in dummy human figures. The ball joints illustrated in Figures 2 and 3 are suitable for wrist and hip joints respectively.

In each embodimentofthe invention illustrated in the accompanying drawing,the adjustable element is formed with a screw thread for co-operation with the second member. Alternatively, the adjustable element and second member may have respective cam formations which co-operate to move the adjustable member along the second member when the element is rotated relative to the second member. In afurther alternative arrangement, the adjustable element may be rotatable on the second member without moving along the second member and be provided with respective cam formations which act on the limbs or gripping parts ofthe second memberto urgethese more strongly againstthe first memberwhen the element is adjusted relative to the second member. In each case where the adjustable element is rotatable relative to the second member, means may be provided for releasably restraining relative rotation of these parts.

Claims (8)

1. Ajointstructure comprising first and second members which co-operate with each other to restrain relative displacement whilst permitting relative angular movement, wherein a part of the first member is trapped between respective gripping parts of the second member and there is provided an adjustable element for urging said gripping parts towards each other.

2. A joint structure according to Claim 1 wherein said element and the second member have respective screwthreadswhich are mutually engaged so thatthe element can be adjusted along thethread of the second member.

3. Ajoint structure according to Claim 1 or Claim 2 wherein the second member has a plurality of spaced limbs, on respective ones of which the gripping parts areformed and wherein the adjustable element engages each ofthe limbs.

4. Ajointstructure accordingto Claim 3 wherein each limb has a part-conical surfaceandtheadjust- able element has a frusto-conical surface engaged with said part-conical surface of each limb.

5. AjointstructureaccordingtoClaim4wherein the limbs ofthe second member are all integral with a common stem ofthe member.

6. Ajointstructure according to any preceding claim wherein thefirst and second members are formed of a plastics material.

7. A joint structure substantially as herein describedwith referenceto and as illustrating in anyone of Figures 1,2 and 3 ofthe accompanying drawing.

8. Any novel feature or novel combination of features disclosed herein or in the accompanying drawing.