GB2094565A - Bayonet type lampholder - Google Patents

Abstract

A bayonet cap type lampholder has a lampholder body part (10) to which a pair of spaced plunger contacts (20) are mounted to be displaceable relative to the body part axially against return bias (16) on fitting and releasing a lamp cap or adaptor (28). The mounting of the plunger contacts (or holders therefor) in the body part further permits other displacement (Figure 3) by lamp cap or adaptor contact of tips of the plunger contacts in the direction of movement of such lamp cap or adaptor as it is twisted for release purposes. <IMAGE>

Description

SPECIFICATION Bayonet type lampholder This invention relates to lampholders of the bayonet type which include two spring-loaded retractable plunger output contacts and in which a bayonet lamp cap, or adaptor, has outwardly directed pins by which it is inserted in a lampholder by the usual pushing and twisting action so that the pins follow and are retained by slots in a skirt portion of the lampholder about its plunger contacts.

Such lampholders are well known, at least in this country, for mains lighting purposes when they are required to have spaced off-centre plunger output contacts to bear on spaced end-contacts of lamp caps, and should be of a robust construction capable of ready lamp replacement over a long working life.

A disadvantage of existing bayonet lam pholders is that over a period of time the plungers sometimes become embedded in the contacts of a lamp cap, which are usually of solder, and the lamp becomes difficult to remove so that efforts to effect removal can result in the destruction of the lampholder or the lamp itself This difficulty arises out of the limited nature of any freedom of the plungers to move in the direction of the paths taken by the lamp cap contacts when the lamp cap is depressed and twisted for removal. The plungers are in guides that restrict such freedom to be within manufacturing tolerances for its components and thus the lamp cap can become trapped in the lampholder.

An object of the present invention therefore is to provide a means by which the plungers are free to move from normal upright positions so that their tips can follow the path described by the cap contacts when the lamp is twisted for removal. Once the lamp cap is withdrawn the plungers are restored to their normal upright position preferably automatically or at least on next lamp cap or adaptor insertion.

Accordingly, in one specific aspect, this invention provides a bayonet cap lampholder comprising a housing, a pair of input terminals, a pair of guides; a pair of plungers being output contacts appropriately electrically connected or connectable to the input terminals and connectable at their outermost ends to a bayonet cap type lamp or adaptor, said plungers being each movable within one of said guides between retracted and extended positions, and pivotable about an axis in the region of its innermost end such that it can be tilted from its normal upright position in order that its outermost end can follow the path of a contact on the lamp cap or adaptor with which it is engaged and in which it may become embedded, such tilt being to an extent adequate for the lamp cap or adaptor to be twisted and withdrawn from the lampholder; each said guide being slotted or recessed on one side to afford the tilt required by the plunger; said plungers being urged outwards of the lampholder by spring means which are housed at least partially in the guides, said plungers being urged to restore themselves to normal upright position by the same spring means; and the degree of travel of the plungers in their motion as aforesaid being limited by suitable end stops included in the spring means or guides or both, excessive motion of the plungers other than aforesaid being discouraged by the guides.

In a preferred form of this aspect each spring means comprises a helical compression spring, and a piston-like member which is slidable within each plunger guide and is interposed between the outermost end of the spring and the innermost end of the plunger. The piston-like member transmits the spring force which urges the plunger outwards of the lampholder and to its upright position while allowing the spring to act within the guide substantially along its longitudinal axis only.

In another preferred form of this aspect, the said piston-like member in each plunger guide may have attached to or formed on the surface which engages the innermost end of the plunger a protuberance which is accommodated in a recess formed in the innermost end of the plunger, a purpose of said protuberance being to provide an end stop to limit the extent of tilt attainable by the plunger from its normal upright position. The limit occurs when the protuberance firmlyengagesthe inner wall of the recess.

Each said plunger guide may be formed as an integral part of the lampholder body which may be of moulded plastics, or be part of a separate unit which additionally houses the plunger, spring, piston-like member if included and the associated input terminal if required, or each said plunger guide may be formed as a composite of both said alternative methods of fabrication.

The spring and, if included, the interposed pistonlike member may form the whole or part of the conductive path between the plunger and associated input terminal.

We have also considered other specific aspects of achieving satisfactory tilting of the lampholder plunger contacts. Thus, slotting or recessing of the plunger guides may be avoided or reduced in extent by alternatively or additionally locally reducing the section or transverse extent of each plunger itself at a position that becomes opposite or level with guide means, say a hole edge or apertured flange, only on depression of the plungers for lamp removal purposes. Then, the axes of tilt for the plungers may well be substantially spaced from their inner ends.

Suitable such reductions of each plunger may be by way of a simple taper or by a cut-out.

Another approach, preferably using spring engaged pips or other protuberances on inner ends of the plungers (also preferred for the abovementioned aspects), is to have elongated guide holesforthe plungers, the plungers normally being aligned against one end edge of such elongated holes.

Again, each plunger may be of a type forming a spring loaded telescopic unit with a guide barrel, The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

when the guide barrel may be permitted tilting movement as above, preferably with side pins or the like of the barrel engaging complementary formations of the body of the lampholderto define specific fixed axes of tilting of the units.

The above-mentioned aspects of this invention are clearly applicable to conventional circular cylindrical section plungers. Other sections of plungers may aid or predispose tilting motions. However, substantially flat plungers may, in fact, be tiltable about axes transversely of and in their main extents, say with pivot defining shoulders, or, if returned on themselves, rely upon resilience of their free ends engaging on edges of guide holes.

Perhaps more generally, we have also directed attention to the required effect of the desired tilting movement of the plungers, which is to escape any indentation of the lamp cap contacts and/or break or facilitate breaking any light bond formed therebetween. Two points result. One is that the extents to which plunger tilting should be required to follow the lamp cap contacts, can usually be substantially less than the full twist of the lamp cap. Also, the provision of rounded plunger ends aids their release from lamp cap contacts, especially for plunger end travels substantially less in extents than twisting travel of the lamp cap contacts.

A particular preferred embodiment hereof has upstanding plunger, bias spring, and connector block housings with headed plungers retained therein and clearances forthe tilting of the plungers.

Embodiments of the invention are now specifically described by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic cross-sectional front view of a bayonet cap lampholder embodying the invention, with a bayonet cap type lamp in situ; Figures 2 and 3 are side views on section X - X of Figure 1, viewed on A (Figure 1); Figure 4 is a side view on section X - X of Figure 1 with the bayonet cap, type lamp removed; Figure 5 is an external plan view on B of Figure 4; Figure 6a is an enlarged plan view of one of the guides in Figure 5; Figure 6b is an enlarged plan view of the plunger which fits in the guide of Figure 6a; Figure 7a is a diagrammatic cross-sectional side view of a bayonet lampholder forming a second embodiment of the invention;; Figure 7b is a plan view of one of the guide and plunger assemblies of Figure 7a; Figure 8a is a part diagrammatic cross-sectional side view of a bayonet lampholder forming a third embodiment of the invention; Figure 8b is an external view in direction of Figure 8a; Figure 9 is a part diagrammatic cross-sectional view of a fourth embodiment of the invention; Figure 10 shows a fifth embodiment; Figures 11 and 12 show embodiments where plungers are modified; Figures 13 and 14 show embodiments using flat plungers; and Figure 15 shows an embodiment using a telescopic plunger/housing unit.

Referring to Figures 1 and 2, a bayonet lampholder has a moulded plastic housing 10 which includes guides 12 which are bores with circular cross sections. Input terminals 14 are fixedly mounted at the top ends of the guides by means not shown. Within each guide 12 is a helical compression spring 16 conductive to electricity, a hollow piston-like member 18 of circular cross section and slidable within guide 12, and an output plunger contact 20.

Spring 16 bears with a force against the lower surface of input terminal 14 and an internal surface of the piston 18. Plungers 20 have at their innermost ends a flange 22 which bear against the lower surfaces of pistons 18, a purpose of the flanges being to retain the plungers 20 in their guides 12 by engagement with flanges 24 of the housing 10.

Guides 12 have a recess 26 (Figure 2) formed on one side to permit passage of the plunger body 20 when this is tilted along the arcuate path shown by the arrow and to put a limit on the amount oftilt permissible. Figures 1 and 2 show normal positions of the members defined (note the upright position of the plungers) when a bayonet cap lamp 28 has been inserted and is held secure by the 'J' slots 30, only one such slot being visible in Figure 1. The other is at the other side of the lampholder in the direction of view. Figures 1 and 2 show the outermost ends of plungers 20 embedded in the solder of the lamp cap contacts 32.

Figure 3 shows the conditions pertaining when the lamp cap is twisted for withdrawal from the lampholder. Plunger bodies 20 are tilted in the directions dictated by the lamp cap contacts, the furthermost plunger 20 and associated cap contact 32 shown in dotted lines to be moving rightwards relative to the direction of view. Pistons 18 are forced upwards into further retraction in the guides 12 by flanges 22 and further compress the springs 16. The tilting action of the plungers 20 enable the lamp/cap to be twisted sufficiently for removal from the lampholder. Figure 4 shows the condition afterthe lamp/cap has been removed; force of the springs 16 push the plungers 20 outwards to the point at which the flanges 22 and 24 engage and preclude further extension of the plungers 20.

Figure 5 shows what in the main is an external plan view in direction B of Figure 4, and the upper guide and recess refer to those visible in Figure 4.

The lower guide and recess refer to those associated with the plunger as in dotted line Figure 3. For clarity the plungers are not shown and the internal profiles of the guides are shown circular and mostly in dotted line. The external profiles of the guides are seen in plan to resemble ovals, and part of these are in fact the flanges 24 of Figures 1,2,3 and 4.

Figures 6a and Sb are respectively enlarged plan views of the upper guide parts of Figure 5 and the plunger 20 and flange 22. Examination of Figure 6a shows that movement of the plungers 20 in other modes than those described are discouraged by the contours of the various members shown.

Figures 7a and7h showthe second embodiment of the invention in which the guide 12, input terminal 14, spring 16, piston 18, plunger 20, flanges 22 and 24 are housed in an integral unit separate from the lampholder housing 10. No recess 26 (Figure 2) is present in this embodiment, but instead, a slot 34 (also shown in Figure 7b) is substituted. The function of this second embodiment is the same as that of the first described.

Figures 8a and 8b refer to a third embodiment in which piston 18 and plunger 20 are modified, piston 18 having added a protuberance 36. This is accommodated in a recess 38 formed in the plunger 20. The object of this modification is to limit the degree of permissible tilt of the plunger 20 by interference between protuberance 36 and recess 38. In the first and second embodiments the limitation of tilt is imposed by the recesses 26 and slot 34 respectively.

In the Figure 8 embodiment, however, the slot 34 may be lengthened in the direction parallel to the longitudinal axis of the guide so that the degree of tilt possible of the plungers 20 is unaffected by the plungers position measured along the longitudinal axis of the guide 12. Figure 8b shows the external profile of the Figure 8a assembly viewed in direction C. The function otherwise of this embodiment is the same as those of the first and second embodiments described.

Figure 9 illustrates a fourth embodiment in which the piston-like member common to the other embodiments described is omitted. Reliance for restoring the plunger 20 to its upright position after the lamp/cap is withdrawn is placed on the lateral resilience of the spring 16 and its longitudinal resilience jointly. Action is otherwise the same as the first and second embodiments described.

Other embodiments of the invention are, of course, possible, for example the protuberance 36 may instead be attached to the plunger 20 and the recess 38 may instead be formed in the piston 18.

In Figure 10, plunger 101 fits through aperture 102 in bottom 103 of an upstanding housing 104 also accommodating compression spring 105 and connector block (not shown) in the general manner of our copending application no. 81/09546 to which reference is directed for further details. The plunger 101 is shown flanged at 111 for retention purposes and has a pip 112 entrant into the interior of the spring 105 for location purposes. The plunger 101 is preferably, but not necessarily, of generally circular section matching the interior boundary of aperture 102. To one side and in the direction of desired tilt of the plunger 101,the aperture 102 progressively flares at 113 to accommodate, indeed limit, tilting of the plunger 101. Inside the housing 104 and opposite to the aperture flaring 113, the housing is relieved at 114, shown above a location step 115 to assist entry of the flange 111.Depression of the plunger 101 for lamp removal purposes causes the flange 111 to clear the step 115. Then, the relieved clearance 114 allows tilting of the plunger 101 and bending of the spring 105. Clearly, once a lamp is removed, the spring 105 and step 115 will ensure automatic restoration of the plunger 101 to its normal untilted attitude more or less against the unflared portion 116 of the aperture 102.

It will be appreciated that, in practice, the entire aperture 102 could be elongated somewhat as at its flared end, i.e. with the slope flare 113 omitted.

In Figure 11, equivalent references to those of Figure 10 are advanced by twenty. Plunger 121 fits in an aperture 122. However, the aperture 122 corresponds (with tolerance) to an upper parallel-sided shank part 126 of the plunger 121 above a reduced section portion 127 tapering at 128 and 129 to the shank part 126 and to a plunger contact head 130.

When the plunger 121 is depressed for lamp cap removal purposes its shank part 126 will clear the walls of the aperture 122 and the plunger can tilt as desired due to clearance between the aperture 122 and the reduced medial plunger portion 127. After removal of a lamp cap the taper 128 and shank part 126 ensure restoration and location of the plunger 121 to and in its normal untiling attitude.

In Figure 12 a plunger 141 differs from that 121 of Figure 11 virtually only by reason of its part 147 below its shank part 146 being simply tapered for tilting after depression of the plunger 141 so that its shank part 146 clears the aperture 142. It will be noted that, compared to Figure 10, equivalent references in Figure 12 are advanced by forty. A step 155 and clearance relief 154 are shown equivalent to those 115 and 114 of Figure 10. Clearly, the same provision could be made in Figure 11.

Concerning Figure 12, it will be appreciated that, if the plunger 141 has antirotation provision, such as a groove in the aperture 142 and a key on and beyond the shank 146 at its right hand side as viewed, the plunge 141 need be tapered only on its left hand side as viewed.

In Figure 13, where equivalent references are advanced by sixty compared to Figure 10, plunger 161 is of flat or flattened section with shoulders 176, 177 affording a tilt axis at their contact with the bottom 163 of the housing 164 to each side of the aperture 162 that is flared to one side 173 for the desired tilting of the plunger. The pip-equivalent top 172 of the plunger 161 is preferably of a length and width sufficient to ensure that tilting of the plunger cause bending of the spring 165, and thus restoration of the plunger 161 from tilting.

In Figure 14, references are advanced by eighty relative to Figure 10, and plunger 181 is of flat pressed form but this time turned back on it;elf at 198 from its lamp cap contact region into the aperture 182. For this embodiment tilting of the plunger will be permitted by inward displacement of the free end 198, which conveniently also provides a, or a component of, plunger righting force after lamp cap removal.

In Figure 15, a skirted lampholder portion 200 has a telescopic plunger/housing unit 201, 202 entrant via an asymmetrically flared aperture 203 generally similartothat 102 of Figure 10. The plunger/housing unit has diametrically opposed projecting pins, such as 204, whereby it can tilt by swivelling of the pins 204 in appropriate grooves or other formations of the base of the skirted lampholder portion 200, a stop 205 being integrally formed on the underside of the base to define the normal plunger attitude with a lamp cap fitted. Bias of the unit 201,202 to the latter position is desirable rather than rely only on a lamp cap to pick up the plungers and pull them to the correct position on insertion.

It will be noted that, in all of the embodiments of Figures 10 to 15, the plungers have tilt axes spaced substantially from their inner end regions.

It will also be noted that the embodiments of Fig ures 11,12, and 15 offer rounded plunger ends for engaging lamp contacts, a feature that we find materially aids lamp cap removal with less permitted tilt than is required fully to follow the twist of the lamp cap on its removal. Tilts of about 8" have been found to be adequate to break any light bond between the plungers and the lamp contacts, and rounded plunger ends can facilitate cam-action by any indentations of the lamp contacts in moving the plungers back against their springs after only a small tilting movement In summary, the invention may be viewed as a bayonet cap type lampholdercomprising a lampholder body part relative to which a pair of spaced plunger contacts are mounted to be displaceable relative to the body part axially against return bias on fitting and releasing a lamp cap or adaptor, wherein the mounting of the plunger contacts or holders therefor in the body part further permits other displacement by lamp cap or adaptor contact of tips of the plunger contacts in the direction of movement of such lamp cap or adaptor as it is twisted for release purposes.

Claims (25)

1. A bayonet cap type lampholder comprising a lampholder body part relative to which a pair of spaced plunger contacts are mounted to be displaceable relative to the body part axially against return bias on fitting and releasing a lamp cap or adaptor, wherein the mounting of the plunger contacts or holders therefor in the body part further permits other displacement by lamp cap or adaptor contact of tips of the plunger contacts in the direc tion of movement of such lamp cap or adaptor as it is twisted for release purposes.

2. A bayonet cap type lampholder according to claim 1, wherein the other permitted displacement is less than the full extent of the twist required to release the lamp cap or adaptor.

3. A bayonet cap type lampholder according to claim 1 or aim 2, wherein free ends of said plungers are rounded.

4. A bayonet cap type lampholder according to claim 1 or 2 or 3, wherein the full extent of the permitted other displacement is available only after depression of the plunger contacts from their normal lamp cap or adaptor contact positions.

5. A bayonet cap type lampholder according to claim 4, wherein each plunger contact is locally reduced in section or transverse extent at a position that becomes opposite or level with guide means of the body part with clearance for said other dis placement only on depression of the plungers for lamp cap or adaptor removal purposes.

6. A bayonet cap type lampholder according to any preceding claim, wherein the plungers are guided in elongated holes in the body part, normal positions of the plungers being aligned against one end edge of each of the elongated holes.

7. A bayonet cap type lampholder according to any preceding claim, wherein each plunger is of a type forming a spring loaded telescopic unit with a guide barrel capable of movement to afford said other displacement of the plungers.

8. A bayonet cap type lampholder according to claim 7, wherein each guide barrel is tiltable for said other displacement via side pins thereof cooperating with complementary formations of the body part.

9. A bayonet cap type lampholder according to claim 1 or claim 2, wherein each plunger is of substantially flat form tiltable for said other displacement on shoulders thereof.

10. A bayonet cap type lampholder according to claim 1 or claim 2, wherein each plunger is of substantially flat material that is returned on itself towards a guide hole of the body part.

11. A bayonet cap type lampholder according to claim 10, wherein each return is into a said guide hole so that plunger tilting for said other displacement is permitted but opposed by resilience of said flat material.

12. A bayonet cap type lampholder according to any preceding claim, wherein the body part has two spaced upstanding housings each for a plunger and associated bias spring and connection block, said plungers being headed for retention in guide holes at ends of the housings.

13. A bayonet cap type lampholder according to claim 12, wherein each housing is interiorly relieved so as to afford clearances for tilting of the plungers.

14. Abayonetcaptype lampholder according to any one of claims 1 to 6 and 9 to 13, wherein spring means acting on said plunger contacts to afford said return bias also serves in returning said plunger contacts from their said outer displacement after removal of a lamp cap or adaptor.

15. A bayonet cap type lampholder having tilting contact plungers substantially as herein described with reference to and as shown in Figures 10 to 15 of the accompanying drawings.

16. A bayonet cap type lampholder comprising a housing, a pair of input terminals, a pair of guides; a pair of plungers being output contacts appropriately electrically connected or connectable to the input terminals and connectable at their outermost ends to a bayonet lamp cap or adaptor said plungers being each movable within one of said guides between retracted and extended positions, and pivotable about an axis in the region of its innermost end such that it can be tilted from its normal upright position in order that its outermost end can follow the path of a contact onthe lamp cap or adaptor with which it is engaged and in which it may become embedded, such tilt being to an extent adequate for the lamp cap or adaptor to be twisted and withdrawn from the lampholder; said plungers being urged outwards of the lampholder by spring means which are housed at least partially in the guides, said plungers being urged to restore themselves to normal upright positions by the same spring means; and the degree of travel of the plungers in their motion as aforesaid being limited by suitable end stops included in the spring means or guides or both, excessive motion of the plungers other than aforesaid being discouraged by the guides.

17. A bayonet cap type lampholder according to claim 16, wherein each spring means comprises a helical compression spring arranged to act on a piston-like memberwhich isslidablewithin each plunger guide and is interposed between the outermost end of the spring and the innermost end of the plunger.

18. A bayonet cap type lampholder according to claim 17, wherein each spring forms at least part of a conductive path between its associated plunger and input terminal.

19. A bayonet cap type lampholder according to claim 17 or 18, wherein each piston-like member has attached or formed on its surface which engages the innermost end of the plunger a protuberance which is accommodated in a recess in the innermost end of the plunger, so that the protuberance acts as an end stop to limit the extent of tilting by the plunger from its normal upright position by engagement of the protuberance with an inner wall of the recess.

20. A bayonet cap type lampholder according to claim 19, wherein each piston-like member forms part of a or said conductive path between its associated plunger and inputterminal.

21. A bayonet cap type lampholder according to any one of claims 16 to 20, wherein each plunger guide is an integral part of a lampholder body.

22. A bayonet cap type lampholder according to any preceding claim, wherein the lampholder body is of moulded plastics.

23. A bayonet cap type lampholder according to claim 17 or any one of claims 18 to 22 as apendant to claim 17, wherein each plunger guide is part of a unit separate from a lampholder body which unit also houses said plunger, said spring and any said piston-like member.

24. A bayonet cap type lampholder according to claim 22, wherein said unit further houses an associated input terminal.

25. A bayonet cap type lampholder substantially as herein described with reference to and as shown in Figures 1 to 9 of the accompanying drawings.