GB2044556A

GB2044556A - Switched electrical connectors

Info

Publication number: GB2044556A
Application number: GB8002997A
Authority: GB
Original assignee: Langner C F; Langner J B
Current assignee: Langner C F; Langner J B
Priority date: 1979-02-09
Filing date: 1980-01-29
Publication date: 1980-10-15
Also published as: GB2044556B

Abstract

A switched electrical connector, preferably a lampholder, which switches off when a connected member such as a light bulb is removed includes a switch actuator 24 and a spring 38 biasing the actuator to the "off" position. Output contacts 16 are slidable in the connector housing 10 and extend in the absence of a light bulb 20 or the like. Additional springs, springs 36 in the embodiment shown, are positioned between the output contacts 16 and the actuator 24 and when the bulb etc. is coupled to the connector provide a component of force which is greater than that provided by the spring 38. However, when the output contacts extend on removal of the bulb or the like said component of force is reduced and the spring 38 moves the actuator "off". <IMAGE>

Description

SPECIFICATION Switched electrical connector This invention relates to switched electrical connectors and is particularly, but not exclusively, of use with switched lampholders as used in table lamps and the like.

Switched lampholders of known type have their output terminals rendered live when ever the actuator is in the "on" position. If a bulb is not present, anyone inadvertently introducing his finger into the lampholder will receive a shock, This is especially dangerous because of the fact that it cannot readily be seen whether the actuator is "on" or "off".

An object of the present invention is to provide an electrical connector, e.g. a lampholder, which switches "off" when a connected member, e.g. a light bulb, is removed; and which cannot thereafter be permanently switched on until a light bulb of the like is again connected.

Accordingly, the present invention broadly resides in a switched electrical connector including a housing and a switch actuating member movable in a generally linear manner in the housing between "on" and "off" positions, and in which the switch actuating member is biased towards the "off" position by spring means, the arrangement being such that the force of said spring means is overcome when the connector has a member (e.g.

a lamp) connected to its output.

In a preferred form, the connector has one or more poles and comprises: an input contact mounted in the housing; cam means formed between the switch actuating member and the housing; an output contact mounted in the housing for movement along an axis between extended and retracted positions; a conductive member secured to the switch actuating member at a location such that the conductive member engages the input contact when the switch actuating member is in its "on" position; means electrically interconnecting the conductive member and the output contact; and further spring means interconnecting the output contact and the switch actuating member to bias the switch actuating member against the cam means and to bias the output contact away from the switch actuating member; the first-mentioned spring means having a strength sufficient to move the switch actuating member across the cam means to the "off" position against the camming force exerted by the further spring means when the output contact is extended but not sufficient to do so when the output contact is extended but not sufficient to do so when the output contact is retracted and the further spring means is thus compressed.

In the preferred form of the invention, the connector is a lampholder with two poles, the output contacts of which are arranged for contact with the base contacts of a bayonet cap lamp. Each pole has a respective input contact, output contact, conductive member, electrically interconnecting means and further spring means, whereas the switch actuating member, cam means and first-mentioned spring means are common to both poles.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an end view partly in section of lampholder forming one embodiment; Figure 2 is a side view partly in section of the lampholder of Fig. 1 in its "on" condition; Figure 3 is similar to Fig. 2 but shows the lampholder "off"; Figure 4 is a partial sectional side view of a second embodiment; Figure 5 is a sectional side view of another embodiment; Figure 6 is a sectional end view of a further embodiment; and Figure 7 is a sectional side view corresponding to Fig. 6.

Referring to Figs. 1 to 3, the lampholder shown comprises a housing 10 suitably of moulded plastics construction. The housing 10 is generally cylindrical and is provided with transverse partitions 1 2 and 14. It will be understood that in practice the housing 10 would normally be formed from two or more members secured together but for simplicity this feature, which is well known, is not shown in the drawings.

The lower transverse partition 1 2 is formed with bores in which output contacts 1 6 are slidable. The output contacts 1 6 are hollow cup-shaped members, suitably of brass. In normal use as shown in the drawings, the output contacts 1 6 bear against contacts 1 8 on the base 20 of a lamp secured in the housing 10 by the usual bayonet cap fitting (not shown).

Input contacts 22 are carried by and extend through the upper transverse partition 1 4.

The input contacts 22 are in the form of rectangular posts, and are provided at their upper ends with means (not shown) such as screws for fastening thereto the conductors of a cable.

A switch actuating member generally designated at 24 extends through slots 26 in the side wall of the housing 10 and is slidable therein. The switch actuating member 24 is cruciform in plan with side arms 28 in which contact members 30 are mounted. The contact members 30 are suitably formed of bent metal strip. A cam surface 32 is formed on the underside of the partition 14. In this embodiment the cam surface 32 is of "V" shape with plane fianks. The switch actuating member 24 has an integral upstanding roundnosed pin 34 which acts as a cam follower in cooperation with the cam surface 32.

it will be seen that if the switch actuating member 24 is pushed to the left as seen in Fig. 2, it will move downwardly and to the left until the pin 34 passes across the point of the cam surface 32; the reverse flank of the cam surface will then urge the actuating member 24 in an over centre manner into the "off" position of Fig. 3. The action from "off" to "on" is similar, and brings the contact members 30 into engagement with the input contacts 22.

Coil compression springs 36 are provided to fulfil two functions. First they provide an electrical interconnection between each contact member 30 and the respective output contact 1 6. Secondly they provide a mechanical bias which both urges the output contacts 1 6 outwardly of the housing and urges the actuating member 24 towards the cam surface 32. It will be appreciated that if the lamp is removed from the lampholder, the output contacts 1 6 are free to extend to the position shown dotted in Fig. 2, and that the springs 36 are thus extended.

A further compression spring 38 is arranged to bear between the pin 34 and the housing 10 via a grub screw 40. The further spring 38 thus tends to move the switch actuating member 24 into the off position.

The strength of the further spring 38 is chosen to be such that when the lampholder is "on" and a lamp is in position, as seen in Fig. 2, the further spring 38 is unable to overcome the reactive force between the pin 34 and the cam surface 32 (plus friction, if significant). However, when a lamp is not present the output contacts extend, the springs 36 elongate, and the force between the pin 34 and the cam surface 32 caused by the springs 36 is thus reduced. The force exerted by the further spring 38 is such that in these circumstances it pulls the actuating member 24 across the cam surface 32 and the lampholder snaps "off". The grub screw 40 is threaded in a bore in the housing 10, and permits adjustment of the force tending to return the actuator to the "off" position.

This is preferably optimised during manufacture and the screw 40 may then if necessary be fixed in position by adhesive.

It will be noted that in the embodiment shown in Figs. 1 to 3, the actuating member 24 in its "on" position is lower in the housing than in its "on" position. It has been found that this assists in making approximately equal the forces which must be exerted on the switch actuating member to turn the lamp on and off.

In a modification, a similar equalisation of the operating forces may be achieved by forming the cam surface such that its flank on the 'on" side is steeper than on the "off" side. In this case the switch actuating member in the "on" position may be level with or higher than its "off" position.

The double function of the springs 36 could be removed, the mechanical biasing being performed by one or more springs bearing on an insulated part of the actuating member, and the electrical connection by separate leads.

In general terms, it can be stated that the invention relies on satisfying the condition IR21 < IPI < lR1l where P is the force exerted by the further spring on the actuator, and R, and R2 are the components of force opposing return to the "off" position when the bulb is respectively in and out of the lampholder.

In order to increase reliability R, and R2 should differ as widely as practicable. Accordingly R, can be maximised by making the actuating member's cam surface flank on the "on" side appropriately steeper than the flank on the "off" side, or by making springs 36 appropriately stiffer. R2 can be minimised by ensuring that when the output contacts 1 6 are fully extended, the follower 34 of the actuating member is free to drop below the level of the cam surface 32: in this case the fully relaxed length of the springs 36 will have to be carefully defined.As this could result in costly springs 36, it would be preferable to constrain the fully extended length of these springs to an accurately defined maximum length, such constraint being imposed for each spring 36 by a flexible wire, chain, or interengaged rigid links contained within the spring and connected to its ends (this modification is not shown). Such constraint means permit compression of the springs 36 and also lateral movement as necessary to permit operation of the actuating member between "on" and "off" positions.

A similar effect is obtained in the embodiment illustrated in Fig. 4. In Fig. 4, similar parts to those of the embodiment of Figs. 1 to 3 are denoted by similar reference numerals.

In this embodiment the springs 36 are each constrained in maximum length by being contained in a housing formed by the output contact 1 6 and a metallic housing member 42 which is slidable in the bore of the transverse partition 1 2. The member 42 is of generally inverted cup shape, and it is bent over at 42a at its lower periphery to engage the upper end of the contact 1 6 to define a maximum length on removal of the light bulb.

The electrical path is via the contact 16, spring 36, and top face 42b of the member 42. Since in this embodiment, the springs 36 are also confined to axial extension and retraction, it is necessary to use other means to accommodate sideways movement of the ac tuator 24. This is provided by modifying the contact member 30 for each spring to have an extension 30a which makes a sliding contact with the top face 42b of the member 42.

It will be appreciated that, when the light bulb is in position, the springs 36 are in compression and exert an upward force on the actuator 24 giving a resultant force R, oppos ing movement of the actuator 24 to the "off" position under the force P of spring 38. In this embodiment, the spring 38 is a simple extension spring connected directly between the actuator and the housing 10.

The embodiment illustrated in Fig. 5 is similar to that of Fig. 4. In this embodiment, however, the actuating member 24 carries a V-shaped section cam face 30a bearing on the member 42, the top face 42b of which is arcuate in section. The cam face 30a in this embodiment is conductive and is integral with the contact member 30 the upper part of which is the "on" position shown is held against the input contact by the camming action. This arrangement constrains the actuating member 24 to a strictly linear movement along a defined axis X-X. This embodiment obviates the need for cam 32 and follower 34 of Figs. 1 to 3.

A further embodiment is illustrated in Figs.

6 and 7. Again, like parts are denoted by like reference numerals. In this embodiment, each output contact 1 6 is connectibel to its associated input contact 22 by means of a respective swinging metal rod 44. Both rods 44 pass through bores in a common cylindrical member 46 which acts as a cam follower and is urged into contact with a V-shaped cam face 48 on the actuator member by compression springs 50 around the rods 44. The rods 44 are pivotally seated on their respective output contacts 1 6.

Thus, when the actuator 24 is pushed to the left from the "on" position shown, the cam follower 46 is forced down one flank of the cam face 48 until it passes over the apex of the "V" and the rods 44 move with a snap action to the right to an "off" position.

Once again, a further spring 38 is provided to produce a force P biasing the actuator 24 towards the "off" position. In this embodiment, the spring 38 is a compression spring housed in a bore in the actuator 24 and bearing on the end of the bore and on the inner face of the housing 1 0. The bore may optionally contain a grub screw (not shown) for adjusting force P. When the main springs 50 are compressed by the presence of a light bulb they exert a higher force with a component R, resisting the force P, and when the contacts 1 6 extend in the absence of a light bulb the resisting component R2 is substantially lower, the springs being chosen to conform to the condition: IR2I < IPI < IR11 It is of course possible to depart from the details of the above embodiments within the scope of the present invention. For example, the cam arrangement of Figs. 1 to 3 can be replaced by two spaced cam surfaces and two corresponding cam followers to avoid or re duce tipping of the actuator member as it moves sideways.

Although described above with reference to a switched lampholder, the invention may be applied to the other electrical connectors, e.g.

socket outlet adaptors.

Claims

1. A switched electrical connector including a housing, a switch actuating member movable in a generally linear manner in the housing between "on" and "off" positions, and spring means biasing the switch actuating member towards the "off" position, the arrangement being such that the force of said spring means is overcome when the connector has a load member connected to its output.

2. A connector according to claim 1, including one or more output contacts movable in the housing transversely to the axis of movement of the actuating member, the output contact(s) being retracted when said load member is connected and being extended when it is not, and further spring means positioned between the output contact(s) and the actuating member to exert a force on the output contact(s) tending to extend them and to exert a force on the actuating member opposing the force exerted thereon by the first-mentioned spring means; the several springs being so dimensioned that when the output contact(s) are retracted the further spring means produce a higher opposing force sufficient to overcome the force of the firstmentioned spring means, whereas when the output contact(s) are extended the further spring means produce a lower opposing force which is overcome by said first-mentioned spring means.

3. A connector according to claim 2, in which the further spring means comprises on or more coil compression springs each of which is provided with means limiting its maximum extension, whereby said lower force is accurately defined and minimized.

4. A connector according to claim 1, comprising: an input contact mounted in the housing; cam means formed between the switch actuating member and the housing; an output contact mounted in the housing for movement along an axis between extended and retracted positions; a conductive member secured to the switch actuating member at a location such that the conductive member engages the input contact when the actuating member is in its "on" position; means electrically interconnecting the conductive member and the output contact; and further spring means interconnecting the output contact and the switch actuating member to bias the switch actuating means against the cam means and to bias the output contact towards its extended position; the first-mentioned spring means having a strength sufficient to move the switch actuating member across the cam means to the "off" position against the camming force exerted by the further spring means when the output contact is extended, but not sufficient to do so when the output contact is retracted and the further spring means is thus compressed.

5. A connector according to claim 4, in which there are two electrical poles each having a respective input contact, output contact, conductive member, electrically interconnecting means and further spring means, whereas the switch actuating member, cam means, and first-mentioned spring means are common to both poles.

6. A connector according to claim 5, in which the further spring means and the electrically interconnecting means are both constituted by a compression spring for each pole.

7. A connector according to claim 6, in which each compression spring is constrained to a given maximum length by constraint means, whereby the compression springs exert a given minimised force on the switch actuating member when the output contacts are extended.

8. A connector according to claim 7, in which each said constraint means comprises a wire, chain or other flexible non-extensible member housed within the spring and attached to its ends.

9. A connector according to claim 7, in which each constraint means comprises interengaged rigid links connected to the ends of the spring.

10. A connector according to claim 7, in which each constraint means comprises an extensible housing formed by the respective output contact and a metallic cylindrical member in which said contact slides, the output contact and cylindrical member having engageable end flanges.

11. A connector according to claim 2, comprising: an input contact mounted in the housing; an output contact mounted in the housing for movement along an axis between an extended and a retracted position; a bridging member mounted on the output contact for pivotal movement with respect to said axis into and out of engagement with the input contact; a cam face formed on the actuating member; a cam follower slidably received on the bridging member; and further spring means trapped between the output contact and the cam follower to bias the output contact towards its extended position and to bias the cam follower against the cam face to produce a camming force opposing the first mentioned spring means.

1 2. A connector according to claim 11, having two electrical poles, each pole having a respective input contact, output contact, bridging member and further spring means, the actuating member and cam follower being common to both poles.

1 3. A connector according to any preceding claim in which the first-mentioned spring means is adjustably connected to the housing.

14. A connector according to claim 14, in which the first-mentioned spring means is a compression spring trapped between the switch actuating member and a grub screw threaded in the housing.

1 5. A switched electrical connector substantially as herein described with reference to and as illustrated in Figs. 1 to 3 or Fig. 4 or Fig. 5 or Figs. 6 and 7 of the drawings.

1 6. The connector of any preceding claim, being a bayonet-type lampholder.

CLAIMS (13Jun 1980)

1. A switched electrical connector including a housing, a switch actuating member movable in the housing between "on" and "off" positions, and spring means biasing the switch actuating member towards the "off" position, the arrangement being such that the force of said spring means is overcome when the connector has a load member connected to its output.