IE49509B1 - Switched electrical connector - Google Patents

Description

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 whenever 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 or the like is again connected.

Accordingly, the present invention broadly resides in a switched electrical connector including a housing, ' a switch-dc-tuating member manually movable in the housing, between oii and off positions selectively, spring means biasing the switch actuating member towards the off position and further spring means engageable by - a load member connected to the output of the connector ' and providing a spring force on the actuating member such that when a load member is present the further spring means produces a relatively high force on the actuating member sufficient to prevent movement of the actuating member by the first-mentioned spring means, whereas when no load member is present the further spring means produces a relatively low force on the actuating member which enables said first-mentioned spring means to move the actuating member to the off position.

Xn 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? and means electrically interconnecting the conductive member and the output contact? the 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 outputcontact away from the switch actuating member;and 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 means is thus compressed.

In the preferred form of the invention, the 509 - 4 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 a lampholder forming one embodiment? Figure 2 is a side view partly in section of the lampholder of Figure 1 in its on condition; Figure 3 is similar to Figure 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 Figure 6.

Referring to Figures 1 to 3, the lampholder shown 25 comprises a housing 10 suitably of moulded plastics· construction. The housing 10 is generally 49508 - 5 cylindrical and is provided with transverse partitions 12 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 12 is formed with bores in which output contacts 16 are slidable. The output contacts 16 are hollow cup-shaped members, suitably of brass. In normal use as shown in the drawings, the output contacts 16 bear against contacts 18 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 14. 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 flanks. The switch actuating - 6 member 24 has an integral upstanding round-nosed pin 34 which acts as a cam follower in cooperation with the cam surface 32.

It will be seen that if the switch actuating5 member 24 is pushed to the left as seen in Figure 2, it will move downwardly and to the left until the pin 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 Figure 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 16. Secondly they provide a mechanical bias which both urges the output contacts 16 outwardly of' the housing and urges the actuating member 24 towards the cam surface 32. It will be appreciated 2o that if the lamp is removed from the lampholder, the output contacts 16 are free to extend to the position shown dotted in Figure 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 49508 further spring 38 is chosen to be such that when the lampholder is on and a lamp is in position, as seen in Figure 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 Figures 1 to 3, the actuating member 24 in its on position is lower in the housing than in its off 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 - 8 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 10 Μ < Μ ς M where P is the force exerted by the further spring on the actuator, and R^ and R^ 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 R^ 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 2o appropriately stiffer. R^ can be minimised by ensuring that when the output contacts 16 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 * 49508 - 9 length o£ 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 Figure 4. In Figure 4, similar parts to those of the embodiment of Figures 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 16 and a metallic housing member 42 which is slidable in the bore of the transverse partition 12. 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 16 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 actuator 24. This is provided by modifying the contact member 30 - 10 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 opposing 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 Figure 5 is similar to that of Figure 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 in 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 Figures 1 to 3.

A further embodiment is illustrated in Figures and 7. Again, like parts are denoted by like 25 reference numerals. In this embodiment, each output contact 16 is connectable to its associated input contact 48508 '15 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 16.

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 10. 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 16 extend in the absence of a light bulb the resisting component R^ is substantially lower, the springs being chosen to conform to the condition: - 12 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 reduce tipping of the actuator member as it moves sideways.

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

Claims (16)

CLAIMS :

1. A switched electrical connector including a housing, a switch actuating member manually movable in the housing, between on” and off positions selectively, spring means biasing the switch actuating member towards the off position, and further spring means engageable by a load member connected to the output of the connector and providing a spring force on the actuating member such that when a load member is present the further spring means produces a relatively high force on the actuating member sufficient to prevent movement of the actuating member by the first-mentioned spring means, whereas when no load member is present the further spring means produces a relatively low force on the actuating member which enables said first-mentioned spring means to move the actuating member to the off position.

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 in which the further spring means is positioned between the output contacts(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 first-mentioned spring means, whereas when the output contact(s) are extended the further spring means produce a lower opposing force which is overcome by said firstmentioned spring means.

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

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; and means electrically interconnecting the conductive member and the output contact; the 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 - 15 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 - 16 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 5 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 10 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; and 15 a cam follower slidably received on the bridging member; the 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 . 20 follower against the cam face to produce a camming force opposing the first-mentioned spring means.

12. A connector according to claim 11, having two electrical poles, each pole having a respective input contact, output contact, bridging member and 25 further spring means, the actuating member and cam follower being common to both poles. 49508

13. 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 5 the first-mentioned spring means is a compression spring trapped between the switch actuating member and a grub screw threaded in the housing.

15. A switched electrical connector substantially as herein described with reference to and as illustrated 10 in Figs. 1 to 3 or Fig. 4 or Fig. 5 or Figs. 6 and 7 of the drawings.

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