GB2254650A

GB2254650A - Ball and socket joint.

Info

Publication number: GB2254650A
Application number: GB9107871A
Authority: GB
Inventors: Graham John Spencer
Original assignee: EMESS PLC
Current assignee: EMESS PLC
Priority date: 1991-04-12
Filing date: 1991-04-12
Publication date: 1992-10-14
Also published as: GB9107871D0

Abstract

A ball and socket joint includes a ball (20) defined part spherical surfaces which engage with part spherical surfaces of a socket (19). The ball is formed with a transverse and axially extending slot (23) and is formed from deformable material to allow it to be engaged in the socket. The component which defines the socket also carries a wedge shaped projection (24) which enters into the slot during engagement of the ball and socket to urge the part spherical surfaces of the ball and socket into engagement. <IMAGE>

Description

BALL AND SOCKET JOINT This invention relates to a ball and socket joint more particularly but not exclusively, for use in a security light system.

In a security light system it is often required to mount in association with a security lamp, a movement sensor such as a passive infra-red unit. The lamp is fixed by means of a bracket onto a support surface, the bracket being constructed so that the lamp can be aimed after being fixed on the surface. The movement sensor can be mounted by means of a further bracket either on the support surface or more usually, on the lamp. In known systems the brackets are formed from pressed metal and this means that the cable connecting the sensor to the lamp is exposed so that the points of entry of the cable into the sensor and the lamp have to be provided with special seals to guard against the ingress of moisture.

It is proposed to replace the bracket which supports the sensor on the lamp by a support incorporating a ball and socket joint. In this way the cable can be passed through suitable apertures formed in the two components which define the ball and socket joint without the need to provide seals.

It is convenient to form the two components by moulding them from plastics material with one component defining the ball and the other component defining a socket, and to engage the two components together by pressing the ball into the socket. The material from which at least one of the components is formed must be sufficiently resilient to permit slight deformation to take place as the ball is pressed into the socket but once engagement has taken place, the resulting joint should be stiff yet capable of manual adjustment. It has been found very difficult to construct such a joint so that the ball can be pushed into the socket and the resulting joint have the required degree of stiffness.

The object of the invention is to provide a joint of the aforesaid kind in a simple and convenient form.

According to the invention a ball and socket joint comprises a first component, a part spherical ball defined at one end of the component, a second component defining a part spherical open ended socket at one end thereof, a transverse slot in the ball, the ball being formed from material which can yield to permit the ball to be pushed into the socket, and a projection carried by the second component and extending into the socket for engagement within said slot as the ball is pushed into the socket, said projection acting to expand the ball into engagement with the part spherical surface of the socket.

An example of the joint in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of a security light system, Figures 2-4 illustrate stages in the construction of part of the system shown in Figure 1, and Figure 5 illustrates relative movement of two components of the system shown in Figure 1.

Referring to Figure 1 of the drawings there is illustrated a security light system including a lamp 10 and a movement sensor 11. The lamp 10 includes a housing 12 in which is mounted a reflector 13 and an elongated quartz halogen lamp 14. An electrical connector block 15 is mounted on the housing and the latter is provided with a lug 16 for attachment to a support bracket whereby it can be secured to a support surface. The lamp is pivotal about an axis 17 to permit aiming of the light produced by the lamp.

The sensor 11 is mounted on the housing 12 of the lamp and for this purpose there is provided a first component 18 of elongated form and which has one end secured within the housing 12. At its other end the component defines an open ended part spherical socket 19 in which is located a part spherical ball 20 formed at one end of a component 21. Conveniently the component 21 is formed integrally with the housing 22 of the sensor.

The tubular component 18 and the component 21 are provided with axially extending bores through which a cable (not shown) can extend from the sensor to the interior of the housing of the lamp. The components 18 and 21 are conveniently moulded from plastics and the ball and the open end of the socket are of such a dimension that the ball can be pressed into the socket and be retained therein.

As more clearly shown in Figures 2, 3 and 4, the ball 20 is provided with aligned transverse slots 23 which extend substantially the whole of the axial length of the ball. The slots facilitate the entry of the ball into the socket 19 by allowing deformation of the ball to take place however, once engaged and without a further item to be described, the ball and socket joint would probably not have sufficient stiffness to be able to hold the sensor at a predetermined setting. In order to avoid this difficulty there is mounted on the second component a pair of wedge shaped projections 24 which conveniently are formed integrally with an annular base 26 which locates against a step defined at the entrance from the ball into the socket.The projections are so dimensioned that during the final movement of the ball into the socket, they engage with the side walls of the respective slots to expand the portions of the ball so that the surfaces thereof engage the part spherical surface of the socket and afford the required degree of stiffness.

Once engaged within the socket, the ball cannot be removed therefrom without the possibility of damage to the socket. The provision of the projections however means that relative movement of the components 18 and 21 is no longer universal and they can be moved relative to each other in one plane only. This is indicated in Figure 5 and the plane is normal to the plane of the "window" of the sensor which is indicated at 30 in Figure 3. In most security light applications the "window" of the sensor will be pointing in the same direction as the beam of light and furthermore, will have a comparatively wide field of view. The joint will allow inclination of the sensor to be adjusted. If it is desired to point the sensor in some other direction the joint will allow the housing 22 of the sensor to be moved angularly and again the inclination can be adjusted. In this case the transverse axis of the "window" will no longer be horizontal.

As will be seen from the drawings the end of the component 18 remote from the socket is stepped with the reduced portion being provided with a screw thread which is engaged by a nut 27. A sealing washer 28 is provided between the step defined adjacent the end of the component and the external surface of the housing.

Moreover, it will be observed that the component 18 is provided with a plurality of peripheral ribs 29 which act to dissipate heat which may be transferred along the component towards the sensor.

As previously stated the bores formed in the components 18 and 21 accommodate a cable which electrically connects the sensor to the connector block and the close engagement of the surface of the ball with the spherical surface of the socket obviates the need for any form of seal.

Claims

1. A ball and socket joint comprising a first component, a part spherical ball defined at one end of the component, a second component defining a part spherical open ended socket at one end thereof, a transverse slot formed in the ball, the ball being formed from material which can yield to permit the ball to be pushed into the socket, and a projection carried by the second component and extending into the socket for engagement within said slot as the ball is pushed into the socket, said projection acting to expand the ball into engagement with the part spherical surface of the socket.

2. A joint according to Claim 1, in which said slot extends diametrically of the ball and axially thereto.

3. A joint according to Claim 2, in which said projection is of tapered form.

4. A joint according to Claim 3, in which said projection is mounted on a base which is located in a recess opening into the socket.

5. A joint according to Claim 4, in which said components are provided with axially extending bores and said base is of annular form and locates against a step defined in the bore in the second component, the projection being formed in two parts with the opposed inner surfaces of the two parts of the projection being spaced so as to allow a cable or the like to be threaded through the bores in the components.

6. A joint according to Claim 5, in which the outer surfaces of the two parts of the projection and the part spherical form are disposed in close proximity to the adjacent part spherical surface of the socket.

7. A joint according to any one of the preceding claims, in which said second component is formed with a plurality of peripheral ribs.

8. A joint according to Claim 7, in which the second component at its other end is provided with a screw thread whereby it can be retained within an opening in a housing of a lamp.

9. A joint according to Claim 7, in which the first component is formed integrally with the housing of a sensor.

10. A ball and socket joint comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.