GB2226190A

GB2226190A - Protected lampholder

Info

Publication number: GB2226190A
Application number: GB8922157A
Authority: GB
Inventors: Alan Cooke; Hugh Jonathan Gearing
Original assignee: Ranton & Co Ltd
Current assignee: Ranton & Co Ltd
Priority date: 1988-10-08
Filing date: 1989-10-02
Publication date: 1990-06-20
Anticipated expiration: 2009-10-02
Also published as: GB8823666D0; GB2226190B; GB8922157D0

Abstract

A protected lampholder for receiving a bayonet lamp comprises a body (101, Figure 1) having an open end for receiving the lamp end and including lamp engaging contacts (125) secured with respect to the body and power supply terminals (109) for electrical connection to the lampholder. Means are operable upon rotatable insertion and removal of the lamp to control making and breaking of electrical contacts between respective associatable ones of the lamp engaging contacts and power supply terminals. The means comprises a rotatable member (133) having limbs (121) actuable by lamp bayonet pins. In a preferred embodiment the rotatable member includes cams (172) that control tipping of respective pivotable switch members 166 to control make and break of electrical connections. The switch members (166) is resiliently fulcrumed on one end of their associated lamp engaging contacts (125). Alternatively, the switch members (31, Figure 3) are constituted by resilient ends of the lamp engaging contacts (26) and are pivoted by a cam surface (42) on rotatable member (33) to make or break with terminals (9). <IMAGE>

Description

Title: Protected Lampholder DESCRIPTION The present invention relates to a protected lampholder for receiving a bayonet type lamp.

Various types of protected/safety lampholder have been proposed with the aim of interrupting electrical supply to lamp contact terminals when the lamp is removed from the holder. W087/04867 and GB 1598903 are examples of two such attempts.

W087/04867 has lamp contacts accommodated in a carrier which is rotatable in the body of the lamp holder. The carrier and hence the contacts are rotated on installation and/or removal of a lamp by cooperating engagement with bayonet prongs of the lamp. Providing adequate location of the rotatable contact carrier complicates the construction.

GB 1598903 has lamp engaging contacts which are axially removable and subjected to spring bias. A rotatable shutter acts directly between the ends of the lamp engaging contacts and the lamp. This dictates large axial movement of the contacts between their extended and retracted positions which increases axial length of the lamp holder whilst posing considerable difficulties to the spring designer to ensure adequate contact force whilst not inhibiting retraction.

According to the invention then there is provided a protected lampholder for receiving a bayonet lamp, the lamp holder comprising a body having an open end for receiving the end of the lamp and carrying lamp engaging contacts secured with respect thereto, and power supply terminals for electrical connection to the lampholder, and means operable upon rotatable insertion and removal of a lamp to control making and breaking of electrical contact between respective associatable ones of the lamp engaging contacts and power supply terminals.

It will be apparent from the above that the lamp contacts are carried non-rotatably in the lampholder body. The means is movable between a first position in which electrical contact is broken between the power supply terminals and the lamp engaging contacts, and a second position in which electrical connection is made between those connections. Said means has limbs extending through arcuate slots in the contact carrying part of the lampholder to the lamp side of the contacts preferably lying flush to boundary walling of the lampholder, preferably internally thereof. The limbs are engageable by bayonet prongs of the lamp whereby said means is rotatable on rotation of the lamp.

Permitted movement of the lamp is controlled by J-shaped cut-outs in the body into which the bayonet prongs of the lamp are received in conventional manner affording 23 degrees rotational movement according to BS 5042. The limbs are engaged by the prongs on insertion into the cut-outs and permitted arcuate/rotational movement of the prongs in the cut-outs rotates said means.

Cooperation of the limbs with the bayonet prongs of the lamp is such that movement of the lamp either for installation or removal always gives desired rotation of said means to achieve make or break. That is done without the need for springs to ensure rotation of the shutter in the isolation direction.

In one embodiment, the aforesaid means comprises a rotatable shutter interposed between the contacts and the terminals to control making and breaking of electrical contact therebetween in dependence upon rotational position of the shutter. The shutter has ramped apertures controlling movement of respective aforesaid connections into and out of electrical conductance. Preferably in that embodiment the lamp engaging contacts are movable relative to the power supply terminals. A particularly effective and yet economical construction is provided where the contact is formed by a strip like electrical conductor whose resilience provides desired electrical contact force with the power supply terminals to one end on movement of the shutter to its second position, and with the lamp contacts at the other.This permits the lamp contact pressure to be controlled separately of the power supply terminal contact pressure even when one strip of conductive material provides the contact surfaces to opposite ends thereof. Such a strip is easily located in an appropriately moulded contact carrying part of the body and such strip-like configuration is particularly easy to assemble.

In a preferred embodiment, the aforesaid means comprises a rotatable plate carrying actuating means for a respective movable contact to control making and breaking of electrical connection between respective ones of the lamp engaging contacts and the power supply terminals. The respective movable contact is conveniently a separate member mounted to perform a controlled rocking movement on either the power supply terminal or the lamp engaging contact, preferably the latter, to provide controlled making and breaking with the other said connections in the manner of a switch.

An alternative is for the movable contact to be a movable part of the power supply terminal or lamp engaging contact, say as a resilient strip-like part.

Thus it is preferred that the lamp engaging contact provide a pivot location for such separate movable contact member, for which appropriate interconnecting lugs may be provided to ensure retention irrespective of lamp holder orientation, or such retention can be provided by cooperating engagement with said actuating means.

More especially then, said actuating means comprises for each movable contact a lug or cam-like part which engages the movable contact member to hold it in one of two tipped positions about its pivot abutment corresponding to a contacts made position and a contacts broken position and corresponding to the rotatable position of said means first mentioned above.

It will be understood that the lug or cam-like part moves arcuately and that this movement is employed to control rocking movement of the contact member as the lug or cam-like part moves across the fulcrum point of the movable contact member so that force is first applied to one side of the fulcrum point and then to the other. The lug or cam-like part may itself comprise a spring-biased plunger as in known electrical switches such as of rocker type or have resilience in its carrier to permit deflection past a fixed fulcrum point.More preferably however, the pivot abutment is resiliently mounted (in contrast to being fixed as in known rocking type switch action), such resilience being conveniently provided by use of a lamp engaging contact or power supply terminal, as appropriate depending on whether the movable contact is pivoted to the former or the latter, which is of resilient strip like form, thereby catering for deflection of the pivot abutment on passage past of the actuating lug or cam-like part then to spring back. The movable contact member carries a contact to one end to mate with a contact part of say the power supply terminal. The rotatable member is usefully positioned to the underside of the fixed contact, i.e. that with which the movable contact is made or taken to provide a back up surface. Accordingly such fixed contact is tracked through aperturing in the rotatable member.

The aforedescribed resilient pivot abutment, by dispensing with the need for a spring loaded operating plunger makes possible a more economical construction of switch which has application other than in a safety lampholder, indeed that could be applied to any switched electrical accessory, especially to the well-known so called rocker switches.

The present invention will now be described further, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a sectional side view on line VI-VI of Figure 2 of a preferred embodiment of protected lampholder; Figure 2 is a plan view of the embodiment of Figure 1; Figure 3 is a cross-section through another embodiment of lampholder taken on line X-X of Figure 4; Figure 4 is a plan view of the body of the lampholder of Figure 3 viewed in the direction of arrow A; J Figure 5 is an inverted plan view of the body of the lampholder of Figure 3; Figure 6 is a cross-section on the centre line of the body of the lampholder of Figure 3; and Figure 7 is an inverted plan of the shutter of the embodiment of Figure 3.

Referring now to Figures 1 and 2 there is illustrated a preferred embodiment of protected lampholder having a body 101 formed as a plastics moulding from a suitable electrical insulating material. The body is generally cylindrical, open to one end 115 and has a cross moulded wall part 102, 104, with part 102 providing location for a pair of lamp engaging contacts 125 and parted and 104 providing location for power supply terminals 109. The housing has J-slots 117 in from its end face for receiving a bayonet type lamp in usual manner. Accommodated within the body and rotatable about the lampholder axis is an actuating plate 133 having a pair of limbs 155 depending therefrom in the direction of the open end and disposed to pass through aperturing 121 in wall 102 and to lie close to the cylindrical wall of the body 101 substantially as previously described.

Shoulder 158 with chamfer 156 provides for insertion and location of the plate in the body.

Each lamp engaging contact 125 is a strip-like element which is restrained in the wall part 102 by ledging along portion 162 which is bent and returned at opposite ends to provide one free end 126 for lamp engagement and at its other end a pivot abutment 164 receiving pivotably a movable contact member 166 in electrical connection therewith. One end of the movable contact member carries a contact 168 for making and breaking engagement with a bent over part 170 of the power supply terminal actually presented above the plate 133 by suitable aperturing.

Making and breaking of the contact is by rocking of the contact member 166 about its pivot abutment 164 and that rocking movement is controlled by a lug or cam-part 172 carried by the rotatable actuating plate 133 by which the contact member is engaged.

Rotation of the actuating plate 133 controlled by engagement with the bayonet prongs of the lamp on insertion and removal, causes the lug to move along the movable contact member from one side of the pivot abutment point to the other thereby giving rise to a tipping movement of the contact member between its on and off position. In the illustrated embodiment to accommodate movement of the lug past the pivot abutment, the pivot abutment is resiliently mounted actually accommodated by resilient deflection of the return arm 174 of the lamp engaging contact.

Reference to Figure 2 shows the general cylindrical nature of the lampholder, the two movable contact members 166 spaced side by side, location of pivot abutments 164 set into recesses 174 in opposite sides of the contact member, contact position 168 and bent terminal provision 170, 111 for input from mains wiring, actually snap/push fitting onto ribbing 180 of wall 104. The lampholder is shown with a skirt 190 and cap 192 in outline only.

Use of the rocking action has the advantage that it easily provides desired gap at the contact 168 on break (at least 3mm) so meeting required electrical performance.

Referring to the drawings of Figures 3 to 7, there is illustrated another embodiment of a protected lampholder having a body 1 formed as a plastics moulding from suitable electrical insulating material and has apertures 3, 5 to receive push fittingly power supply terminals 9 for live and neutral, which terminals are barbed at 11 for retention in the respective apertures. Provision for crimping wire to the power supply terminals are shown at 13. The body is open to one end as at 15 to receive a bayonet type lamp, and has diametrically opposed J-shaped cut-outs 17 open to the end face 19 for entry of bayonet prongs of a lamp (not illustrated). The body has arcuate apertures 21 whose purpose will be apparent further hereinafter.

As seen best in Figure 3 a pair of lamp engaging contacts 25 (only one visible) (of strip-like form generally S or Z shape) are received securely in the body. An end 26 of the contact projects from the carrier part of the body and is generally ramped for cooperating engagement with respective contacts of a lamp when installed into the lampholder. The length of the end 26 form where it enters the carrier is such as to provide necessary resilience to give desired electrical contact pressure with the lamp contacts.

The other end 30 of each contact is shaped to provide satisfactory electrical conducting engagement with the respective power supply terminal 9, actually shown in contact in Figure 3. The resilience of the arm like portion 31 provides sufficient electrical contact force.

A shutter 33 is mounted rotatably in the body actually journalled on it such as at end faces 35, with terminals 9 providing location against axial movement.

The shutter conveniently has a central opening 37 which fits onto a corresponding pivot part 38 of the body, and diametrically opposite apertures 39 with ramped surfaces 41 for controlling movement of the contact part 30 upon rotation of the shutter. Each ramp has an indent or recess 42 in which the contact end 30 is retained when in the isolated position. The shutter has two diametrically opposed limbs 55 located at the periphery thereof and which extend away from the disc like body of the shutter in a direction towards the open end of the lampholder. Actually those limbs extend through the aforementioned arcuate apertures 21 in the body of the carrier. Those arcute apertures allow for arcuate movement of the shutter limbs about the central axis of the lampholder the limbs extend substantially to the end 19 of the lampholder and each have a straight slot open to the free end of the limb and arranged to align with entry to the J-shaped slots in the body. The straight slots of the limbs extend inwardly so that they are entered by the bayonet prongs on entry of same into the opening of the J-slot and permit movement axially towards the bottom thereof.

Thereafter rotation of the lamp to give movement of the prongs round the J-slot into the resting position at the end 31 of the J gives simultaneous rotation of the shutter from its first position to its second position in which contact is made between the lamp contact end part 30 and the power supply terminal 9.

The 23 degrees of rotation required under the provisions of BS 5042 is sufficient to produce the switching action. Where deemed necessary inclination of the slots in the limbs can be used to increase the angle of rotation of the shutter.

Rotation of the lamp in the opposite direction for removal turns the shutter in the opposite direction so as to disengage the contact end 30 from the terminal 9 bringing it to rest in the recess 42.

It will be apparent from the above that when the lamp is removed the lamp contact are electrically isolated. The presence of the limbs is readily advantageous indicating to the user that the lampholder is a protected type.

Claims

1. A protected lampholder for receiving a bayonet lamp, the lampholder comprising a body having an open end for receiving the end of the lamp and carrying lamp engaging contacts secured with respect thereto, and power supply terminals for electrical connection to the lampholder, and means operable upon rotatable insertion and removal of a lamp to control making and breaking of electrical contact between respective associatable ones of the lamp engaging contacts and power supply terminals, wherein said means comprises a movable actuating means for a respective movable contact to control making and breaking of electrical connection between respective ones of the lamp engaging contacts and the power supply terminals and wherein the respective movable contact is mounted to perform a controlled rocking movement about a pivot abutment to provide controlled making and breaking between the respective associated power supply terminal and lamp engaging contact in the manner of a switch.

2. A protected lampholder as claimed in claim 1 in which said means is movable between a first position in which electrical contact is broken between the power supply terminals and the lamp engaging contacts, and a second position in which electrical connection is made between those connections.

3. A protected lampholder as claimed in claims 1 or 2 in which permitted movement of the lamp is controlled by J-shaped cut-outs in the body into which the bayonet prongs of the lamp are received.

4. A protected lampholder as claimed in claim 1, 2, or 3 in which said means has limbs extending through arcuate slots in the contact carrying part of the lampholder to the lamp side of the contacts for engagement by bayonet prongs of the lamp whereby said means is rotatable on rotation of the lamp.

5. A protected lampholder as claimed in claim 4 in which the limbs lie flush to boundary walling of the lampholder.

6. A protected lampholder as claimed in claims 4 or 5 in which the limbs are internally of boundary walling of the lampholder.

7. A protected lampholder as claimed in claim 4, 5 or 6 in which cooperation of the lamp bayonet prongs with said limbs either for installation or removal of the lamp gives desired rotation of said means to achieve make or break.

8. A protected lampholder as claimed in any one of the preceding claims in which each movable contact is a separate member mounted to perform its controlled rocking movement on either the power supply terminal or the lamp engaging contact.

9. A protected lampholder as claimed in any one of claims 1 to 7 in which the movable contact is a movable part of the power supply terminal or lamp engaging contact, say as a resilient strip-like part.

10. A protected lampholder as claimed in any one of claims 1 to 8 in which the lamp engaging contact provides a pivot location for such a separate movable contact member.

11. A protected lampholder as claimed in claim 10 in which interconnecting lugs ensure retention of the movable contact member irrespective of lampholder orientation, either with pivot location or by cooperating engagement with said actuating means.

12. A protected lampholder as claimed in any one of the preceding claims in which said actuating means comprises for each movable contact a lug or cam-like part which engages the movable contact member to hold it in one of two tipped positions about its pivot abutment corresponding to a contacts made position and a contacts broken position and corresponding to the rotatable position of said means first mentioned above.

13. A protected lampholder as claimed in claim 12 in which said lug or cam-like part moves arcuately and that this movement is employed to control rocking movement of the contact member as the lug or cam-like part moves across the point of pivotting of the movable contact member so that force is first applied to one side of the pivot point and then to the other.

14. A protected lampholder as claimed in claim 12 or 13 in which the lug or cam-like part comprises a spring biassed plunger or has resilience in its carrier to permit deflection part or fixed pivot point.

15. A protected lampholder as claimed in claim 12 or 13 in which, the pivot abutment is resiliently mounted.

16. A protected lampholder as claimed in claim 15 in which the resilience is provided by use of a lamp engaging contact or power supply terminal, as appropriate depending on whether the movable contact is pivoted to the former or the latter, which is of resilient strip like form, thereby catering for deflection of the pivot abutment on passage past of the actuating lug or cam-like part then to spring back.

17. A protected lampholder as claimed in any one of the preceding claims in which the movable contact member carries a contact to one end to mate with a contact part of the power supply terminal.

18. A protected lampholder as claimed in any one of the preceding claims in which the actuating means is rotatable and is positioned to the underside of the fixed contact and such fixed contact is tracked through aperturing in the actuating member.

19. A protected lampholder constructed and arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings of Figures 1 and 2.