GB2201037A

GB2201037A - Electrical tilt switch

Info

Publication number: GB2201037A
Application number: GB08702912A
Authority: GB
Inventors: Arthur Jeffrey Arnold
Original assignee: Arcolectric Switches PLC
Current assignee: Arcolectric Switches PLC
Priority date: 1987-02-10
Filing date: 1987-02-10
Publication date: 1988-08-17
Also published as: GB8702912D0; DK65088D0; DK65088A

Abstract

A tilt switch 10 comprises a rocking contact 60 which is rocked by a heavy cylindrical, spherical or cubic mass 90 rolling or sliding thereon, and guided by the housing and partitions 41, 42. The tilt switch may be combined with a lampholder (11, Fig. 3 not shown), the following members comprising a series electrical circuit: first switch terminal 70, side lamp contact (74), an inserted bulb, base lamp contact (55), conductive pivot 53, rocking contact 60, fixed contact 84 and second switch terminal 80. Terminals 70, 80 are protected by a terminal cap (13) which snap-fits or is heat sealed to the switch housing. <IMAGE>

Description

Electrical Switch The present invention relates to an electrical switch and more particularly to a tilt switch with a contact arrangement incorporating a movable mass, such as a rolling member.

Various types of tilt switch are known. One 'type employs a small amount of mercury to make and break contact; however this is a potential safety hazard because mercury is a toxic material. In another type, a silver-plated ball is used to bridge two fixed contacts; the plated ball is expensive to manufacture and special fixed contacts are also necessary.

In a further type of tilt switch a ball is used to actuate a contact made of resilient phosphor-bronze wire. The inherent resilience of the wire contact biases it to its off position, but, on engagement by the ball, the weight of the ball overcomes the resilience to move the wire contact to its on position.

However, it has been found that the wire contact is too thin and acts like a fuse since quite a small current surge is sufficient to burn it out. An attempt was made to overcome this disadvantage by emp] oying a thicker resilient wire; however, in practice, this would have needed a roller of four to five times the weight to actuate it; this would have required too much space and would have been prohibitively expensive, especially in roller material.

The present invention seeks to overcome or reduce one or more of the above disadvantages.

According to the present invention there is provided a tilt switch comprising a housing and, within the housing, a fixed contact, a rocking movable contact and a movable mass, the movable mass being actuated by tilting of the housing to rock the movable contact between a first position in engagement with the fixed contact and a second position out of engagement with the fixed contact.

The interior of the housing may have constraining means which define a path for the movement of the movable mass, one end of the path defining the position of the mass when the movable contact is in its first position and the other end of the path defining the position of the mass when the movable contact is in its second position.

The movable mass is preferably of circular crosssection and rolls along its path; the mass may be cylindrical or spherical. Alternatively, or in addition, the mass may slide along its path. The switch is preferably combined with a lampholder.

A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Fig.l is a view of one end of a switch in accordance with the present invention in the "off" position and with a terminal cover omitted for clarity; Fig.2 is a view similar to Fig.l with the tabs of the terminals also omitted for clarity and with the switch in the "on" position; Fig.3 is a sectional view taken on the line A-A of Fig.l with the terminal cover in position; Fig.4 is a top plan view of Fig.3, on a smaller scale; and Fig.5 is a view of the switch of Fig.l shown from the other end on a smaller scale.

Referring to the drawings there is shown a tilt switch 10 incorporating a -lampholder 11. The tilt switch comprises a plastics housing 12 having a removable plastics terminal cap 13. The housing 12 and cap 13 are both in the form of injection mouldings. The upper surface 14 of housing 12 is provided with a spigot 15; part of each of the side edges of the upper surface is formed as a flange 16 with a respective through hole 17 for mounting the switch 10. The end of the housing opposite to terminal cap 13 has a cylindrical recess 20 which tapers to a smaller internally threaded cylindrical redess 21 for receivina a lamp (not shown) with an externally threaded base.

The housing 12 also has four small square apertures 3C for receiving snap-in feet 31 of the terminal cap 13.

The terminal cap has two terminal compartments 32 defined on the one hand by an external end wall 33, two side walls 34, and a bottom wall 39, and on the other hand by an internal wall 35 and'a partition 36 which extend downwards only one half of the height of the switch. The terminal compartments 32 are open at the top to permit access thereto.

Housing- 12 has an interior wall 40 from which project partitions 41, 42 and 43 of which the first two extend right across internal space 47 so as to be abutted by the wall 35 of the terminal cap. A ledge 49 projects from a side wall of the housing.

Partition 43 located at a level below wall 35 and incorporates a channel section 45 and an inverted channel section 46 which extend into the terminal cap.

Wall 40 also has a rectangular through hole 48 located below partition 43.

Partition 43 has first and second projections 51, 52 at its upper surface. These projections are arranged to hold firmly between them the base portion of a conductive pivot member 53 of the switch. The top of pivot member 53 has a respective projecting limb at each side, i.e. one at the side adjacent wall 40 and one at the side adjacent wall 35. Between the limbs is a portion providing a pivot edge (not shown). Pivot member 53 has an integral tab portion 55 which proects through wall 40 to form the base contact for a lamp in the lampholder 11.

Pivotally arranged on the pivot edge of pivot member 53 is a rocking or see-saw movable conductive contact member 60. A central projection at each side of contact member 60 is bifurcated to engage a respective one of the limbs of the pivot member to locate the movable contact in its correct position. The contact member comprises a flat arm 62 and a curved arm 61 carrying a contact 65. The see-saw member is preferably a brass stamping with solid silver contact points.

Mounted in inverted channel section 46 is a first conductive terminal member 70. The terminal member comprises a vertical tab portion 71, located in one of the terminal compartments 32 of the terminal cap, a horizontal portion 72 extending snugly along and within inverted channel section 46 and thus serving to firmly mount the terminal member in the housing, a curved vertical portion 73, and a horizontal portion 74 which extends through aperture 48 to form the side.

contact for a lamp in the lampholder 11.

Mounted in channel section 45 is a second conductive terminal member 80 which comprises a vertical tab portion 81 located in the other of the terminal compartments 32, a horizontal portion extending snugly along and within the channel section 45 to firmly mount the terminal member 80 in the housing, and a vertical portion 83 carrying at its top a horizontal fixed contact 84.

Above movable contact member 60 and located within the space defined by partitions 41 and 42 is a cylindrical roller 90. The roller 90, which is preferably of brass, can move between the right hand end position of Fig.l in which it bears against ledge 49, and the left hand end position of Fig.2 in which the roller bears against partition 41.

In use a bulb is screwed into lampholder 11 so that its two contacts respectively engage conductive contact portions 55 and 74. With the roller 90 in its Fig.] position it engages arm 62 so that contact 65 is held clear of contact 84 and the switch is in its "off" condition. When the switch 10 is suitably tilted, roller 90 rolls to its Fig.2 position which causes contact member 60 to rock so that an electrical circuit is completed by contacts 65 and 84. The electrical circuit comprises terminal 70 (which is connected to one pole or terminal of a power source) contact 74, the inserted bulb, contact 55, pivot member 53, rocking contact member 60, contacts 65 and 84,and terminal 80 (which is connected to the other pole or terminal of the power source). The~ switch 10 is now in its "on" condition and the bulb lights up.

An advantage of the above-described switch arrangement is that the movable roller 90 does not form part of the electrical circuit and so can be of any convenient dense material. The contact members of the switch are of conventional type and may be inexpensively manufactured, and there is no danger of them burning out. A good electrical contact is maintained at all times in the "on" condition, so that flickering of the lamp is avoided.

The injection moulded housing 12 serves a number of functions simultaneously: it supports and retains the electrical connectors and the operating mechanism; the moving parts are retained so that they cannot be dislodged during manufacture or transit; it incorporates means for attaching the lamp; and its properties permit a snap-fitting with the terminal cap 13 rather than heat sealing which is more time consuming and expensive.

Various modifications can be made to the abovedescribed switch. For example the roller can be of a dense insulating material -if required. The cylindrical roller can be replaced by a sphere; alternatively it may be replaced by a mass which slides rather than rolls, e.g. a cubic block. The lampholder 11 may be omitted if desired and the switch may be used to perform any desired switching function, including simply making or breaking an electrical connection between the two terminals 70 and 80.

Instead- of snap-fitting, the terminal cap 13 can be heat-sealed to the housing. If desired the terminal cap can be replaced by a flat cover corresponding to wall 35 only, which simply retains the moving parts in position leaving terminal tabs 71, 81 exposed.

Claims

1. A tilt switch comprising a housing and, within the housing, a fixed contact, a rocking movable contact and a movable mass, the movable mass being actuated by tilting of the housing to rock the movable contact between a first position in engagement with the fixed contact and a second position out of engagement with the fixed contact.

2. A switch according to claim 1 comprising constraining means which define a path for the movement of the movable mass, one end of the path defining the position of the mass when the movable contact is in its first position and the other end of the path defining the position of the mass when the movable contact is in its second position.

3. A switch according to claim 1 or 2 wherein the movable mass rolls along its path.

4. A switch according to any preceding. claim comprising a first terminal projecting from the housing and electrically connected to the fixed contact, a second terminaily projecting from the housing and arranged to be electrically connected to the movable contact, and a terminal cap which is arranged to be snap-fitted to the housing whereby to shroud said first and second terminals.

5. A tilt switch substantially as herein described with reference to the accompanying drawings.

6. An electrical device comprising a tilt switch as claimed in any preceding claim integrally connected to.

a lampholder apparatus having two terminals.

7. A device according to claim 6 wherein the movable contact has a conductive pivot constituted by a first portion of a conductive member, another portion of which constitutes one of the terminals of the lampholder apparatus.

8. A device according to claim 7 wherein the switch is as claimed in claim 4, and the electrical connection between the second switch terminal and the movable contact is via the conductive pivot and the lampholder apparatus.

9. An electrical device substantially as herein described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows Claims 1. A tilt switch comprising a housing and, within the housing, a fixed contact, a rocking movable contact and a movable mass, the movable mass being actuated by tilting of the housing to move relative to the movable contact so as to rock the movable contact between a first position in engagement with the fixed contact and a second position out of engagement with the fixed contact, and the housing comprising fixed constraining means which define a path for the movement of the movable mass, one end of the path defining the position of the mass when the movable contact is in its first position and the other end of the path defining the position of the mass when the movable contact is in its second position.

2. A switch according to Claim 1, wherein the constraining means comprises internal partitions of the housing.

3. A switch according to Claim 1 or 2, wherein the housing including its internal partitions is constituted by an injection moulding.

4. A switch according to any preceding claim, wherein the movable mass rolls along its path.

5. A switch according to any preceding claim comprising a first terminal projecting from the housing and electrically connected to the fixed contact, a second terminal projecting from the housing and arranged to be electrically connected to the movable contact, and a terminal cap which is arranged to be snap-fitted to the housing whereby to shroud said first and second terminals.

6. A switch according to claim 5, wherein the terminal cap is constituted by an injection moulding.

7. A tilt switch substantially as herein described with reference to the accompanying drawings.

8. An electrical device comprising a tilt switch as claimed in any preceding claim integrally connected to a lampholder apparatus having two terminals, wherein the movable contact has a conductive pivot constituted by a first portion of a conductive member, another portion of which constitutes one of the terminals of the lampholder apparatus.

9. A device according to claim 8 wherein the switch is as claimed in claim 5, and the electrical connection between the second switch terminal and the movable contact is via the conductive pivot and the lampholder apparatus.

10. An electrical device substantially as herein described with reference to the accompanying drawings.