GB1598903A - Bayonet lampholders - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO BAYONET LAMPHOLDERS (71) We, CARLO LUCINI of Via Einaudi, 26 25100-Brescia, Italy and VIA RIO WALTER S.p.A. of Via IV Novembre 36063-Marostica (Vicenza) Italy, an Italian Citizen, and an Italian company, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to improvements in or relating to bayonet lampholders or similar type of electrical supports.

Bayonet lampholders suffer from the serious disadvantages of lighting the lamp as soon as the latter is inserted and not yet at its steady operating position, unlike other types of lampholders. Thus, in threaded types of lampholders a lamp has to be thoroughly screwed down before lighting; also in lampholders for tubular fluorescent lamps, a lamp has to be rotated before lighting.

On the other hand, in bayonet lampholders, a lamp is immediately lit when the user, due to negligence, inattention or ignorance, does not cut off the voltage to the lampholder before setting about to change a lamp. This may cause serious disadvantages because of creating in a user a feeling of uneasiness due to the sudden dazzling and rapid increase in temperature in the glass bulb he is handling. Moreover, at this stage arcs and sparking damaging the contacts may be produced.

A further disadvantage of conventional type of bayonet lampholder is due to the fact that lamp connection is provided by an angular rotation only in clockwise direction and an unwarned user will not always rotate the lamp in such a direction. This contributes to increase his state of discomfort.

Should the common bayonet lampholder be then examined from a protection standpoint, it would be seen that it has the serious disadvantage of its contacts being exposed and accessible upon lamp removal and accordingly dangerous for persons casually touching them.

Therefore, it is a further object of the present invention to provide also a bayonet lampholder having protected contacts for those cases where it is necessary that its degree of protection is at least of IP 2X (standard test finger inaccessability) of live parts according to IEC international classification), equal to that of other electrical fittings, such as socket-outlets and switches, for domestic and similar purposes.

The present invention provides a bayonet lampholder comprising a housing body for holding the base of a lamp bulb, the housing carrying electrical contacts for cooperation with contacts on the base of the lamp when it is inserted in the housing, the housing having an annular rim defining a reduced diameter inlet at its open end in which opposed slits are provided for insertion of the bulb pins, resting points for the pins being provided on the undersurface of the rim at a separation of 90" from the inner ends of the inlet slits, such that a lamp base, when inserted through the slits, can be rotated in either a clockwise or counterclockwise direction until the pins are located in the resting points, at which position the lamp contacts cooperate with the lampholder contacts. The lamp therefore has to be fitted and then rotated for lighting.

The lamp connection can be obtained either by a clockwise or by a counterclockwise rotation, as desired by a user, who therefore will not feel any discomfort during the operation that he will be able to perform in a full calm because he is not handling a bulb which, in case of his ignorance or negligence, may dazzle and scald or burn, neither will he be obliged to a rotation in a predetermined single direction.

When the lamp is fitted, the lampholder contacts coincide with the insulating surface of the lamp cap, and only after the successive rotation do they coincide with those of the lamp. Therefore, upon lamp fitting, the latter remains switched off.

Moreover, the connection system comprises slits and resting points that are spaced apart from one another and such that the lamp can be clockwise and counterclockwise rotated through the whole angle of 360" around the periphery of the annular rim. This could not be obtained in the prior art type of lampholder where the pins were inserted through contoured slits in a cylindrical plate sleeve. Such sleeves form easily deformable cantilevered elements.

For a bayonet lampholder having protected contacts, the present invention also provides the general application to the above described lampholder of a cupshaped protecting device, having a fixed or movable bottom, rotatable between a noneuse position, in which the contacts are shielded, and a use position, in which the contacts project from holes or other openings in the bottom of the rotatable cup.

The rotation control to the rotable cup between an inoperative position and an operative position is imparted by the same electric member, such as a lamp, which is inserted in a bayonet fashion in the support or by a suitable implement. Thus, no access can be made to the electrical contacts when a lampholder is empty or inoperative, thereby assuring the user not only a protection degree of at least IP 2X (standard test finger inaccessibility of live parts according to IEC international classification), but also the lamp insertion without any risk of immediate lighting. The arrangement is such that the rotable cup cannot be manually rotated by an unwarned user, but only means of the object which is to be supported by the lampholder.

Prior art bayonet lampholders having protected or shielded contacts use a protection device provided with auxiliary contacts, fixed or inserted in a rotatable element, designed to connect with the lamp insertion movement the lampholder terminals with the contacts on the lamp cap.

However, such auxiliary contacts cause a detrimental increase in operating temperature and detrimental arcs and sparkings for the lamp and lampholder contacts.

A lampholder according to the present invention offers the following advantages: lamp lighting only after rotation, ensured both in the improved common lampholder and in the protected lampholder; possibility of rotation in clockwise and counterclockwise direction; possibility of full rotations; connecting members which are sturdy and free of cantilevered elements readily deformable even with a rotation of lamp connection to the lampholder extended to 90"; possibility of manufacture in plastics or ceramics material and also in metal sheet; and overall sizes comparable to those of lampholder as used at present.

A lampholder with contact protection, having the electric contacts concealed and inaccessible on lamp removal, can be touched without any damage or injury by unwarned persons and children. It additionally offers the advantage of being easily distinguishable from a common lampholders having exposed and accessible contacts. The same is not generally true of hitherto known protected or shielded lampholder which, by using auxiliary contacts of metal parts exposed and accessible on lamp removal, does not differ from the outside, from a common lampholder. Thus the user is not sure whether or not there are exposed live parts.

The lampholder with contact protection also has the further advantage of using a protective device, comprising a rotatable cup, which is simple, sturdy, readily manufactured and of easy operation.

Some preferred embodiments of the present invention will now be described by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows the cap of a bayonet lamp as seenfrom the side of the contacts; Fig. 2 is a longitudinal sectional view of an embodiment of an improved common lampholder according to the present invention; Fig. 3 is a fragmentary longitudinal sectional view as Fig. 2, but rotated through 90"; Fig. 4 is a view taken along line 11 of Fig. 2 looking in the direction of the arrows; Fig. 5 is a longitudinal sectional view of a general type of lampholder with contact protection at inoperative condition; Fig. 6 is a sectional view taken along line 66 of Fig. 5, looking in the direction of the arrows; Fig. 7 is a fragmentary longitudinal sectional view as Fig. 5, but at operative condition; Fig. 8 is a sectional view taken along line 8-8 of Fig. 7, looking in the direction of the arrows; Fig. 9a is a longitudinal sectional view as Fig. 5, fragmentary and of a modified embodiment; Fig. 9h is a view of Fig. 9a, looking in the direction of arrows b-b of Fig. 9a; Fig. 9c is a sectional view of the cup shown in Fig. 9b, looking in the direction of arrows c-c; Fig. 10 is a fragmentary longitudinal sectional view as Fig. 5, of a further modified embodiment of the lampholder: Fig. 11 is a fragmentary longitudinal sectional view as Fig. 7, but with the cup having been modified, that is uncapable of axially moving; Fig. 12 is a fragmentary longitudinal sectional view of a lampholder provided with protected contacts in an embodiment with movable bottom cup, at inoperative condition; and Fig. 13 is a sectional view taken along line 13-13 of Fig. 12, looking in the direction of the arrows.

To designate the same or like parts, the same reference numerals have been used in the various figures of the drawings. An improved common lampholder, as shown in Figs. 2, 3 and 4, comprise a dome 1 and a body 5 connected by means of screws (not shown) inserted in the respective lugs or tabs, or by a resilient connection requiring the use of a tool for disconnection operation.

Said body 5 has accommodated therein a contact holder insulating plate 3 which is similar to that of the lampholder type at present used, with terminals 7 on one of the faces or sides and contacts 4 having inner coil springs 41 on the opposite face or side.

At the open end said body 5 has an annular, inwardly projecting rim 52, in which slits 521 are provided for the insertion therein of pins 811 (see Fig. 1) of the lamp cap and resting points 522, therein accomodating said pins when the lamp is at active lighting position. The shifting angle cr between fit location E corresponding to slits 521 and resting points V corresponding to resting points 522 is substantially an angle of 90" (Fig. 4), so that fit locations E, that is slits 521, are aligned with the axis on which said contacts 4 are located. The shifting angle fi between the resting points V and axis on which the contacts are located is also an angle of substantially 900. When looking at Fig. 1 of the lamp cap, it will be readily appreciated that when the lamp is inserted, the lampholder contacts get in touch with the insulating area of the cap and the lamp is not switched on. Fit location E corresponding to slits 521 and resting points V corresponding to resting points 522 are not connected by slot guide contours with cantilevered tabs, as in present lamp sockets, but are free and not contained within a contour. Therefore, the mutual shifting angle may be extended to 90" without giving rise to readily deformable cantilevered elements. In addition, the arrangement is such that the lamp can be connected by rotation in clockwise or counterclockwise direction, and connection and disconnection can be as well effected by full rotations in either direction.

The lampholder operates just as that at present used. On inserting the lamp cap, pins 811 enter said slits 521 until the cap bottom comes with its insulating area in contact with contact 4, whereupon linear insertion is continued overcoming the resistance of the contact springs 41, until said bottom gets in touch with said contact holder insulating plate 3. At this stage, the lamp cannot be lit, since its contacts are not coinciding with those of the lampholder. At the end of the linear movement, an angular rotation of 90" brings the cap contacts 812 to coincide with the lampholder contacts 4 and the lamp cap pins 811 to insert in resting points 522 under the action of said contact springs 41. The lamp is now firmly retained in place in operating condition. The path for pins 811 is indicated by a dash and two dots line in Figs. 2 and 4.

For lamp removal, a reverse operation may be followed by a counterclockwise rotation, as in a conventional lampholder, or clockwise rotation can be continued, as in insertion operation, until pins 811 reach slits 521. However, it can be readily appreciated from Figs. 2 and 4 that the routine of on-off lamp can be obtained by successive rotations of 90" each in clockwise or counterclockwise direction. Should it be deemed more convenient to limit the lamp rotation in forward and backward direction within 90" the round projection on the open end of body 5 could be limited to only two opposite sectors of 90 .

In the following Figs. 5 through 13, the application is shown of a general type of contact protecting device to the improved common lampholder above described.

The lampholder provided with protecting device, shown in Figs. 5 through 11, has a cup 6 accommodated between plate base 3 and rim 52 of body 5. Circular imprints 62 are formed on the cup bottom and at inoperative position receive therein said contacts 4, which are accordingly shielded and inaccessible.

The action of springs 41, pressing contacts 4 in the seat or housing comprising said prints 62 and simultaneously pressing the cup brim against the undersurface of the projection 52, as well as the projection insured to the cup brim by the annular projection 52, prevents said cup from being manually rotated since no gripping point can be reached by fingers.

On the bottom, said cup has two holes of conical or tapered section 63, from which contacts 4 surface when the cup is rotated to active position. Said holes are located at 90" relative to imprints 62, wherein contacts 4 are received at rest position, thus insuring inaccessibility of contacts to a standard test finger. Said conical or tapered section, along with that of the contact end, is intended to facilitate the retraction or reenter of the latter when the cup is brought back to inoperative position with the shielded contacts.

From Fig. 7 it will be readily appreciated that the minimum diameter of surfacing hold 63 is less than that of contact 4 to prevent the latter from coming completely out of the cup bottom, in which case the retraction or back movement of the contact would be hindered or prevented. In order to further exclude such a detrimental possibility, contact 4 could be provided with a collar 42 (Fig. 12).

Two slits 61 are provided on the cup brim and coincide with slits 521 of round projection 52 of said body 5 when the lampholder is at inoperative position.

The profile of the sliding surface between the brim of rotable cup 6 and round projection 52 of the body preferably has a zone comprising a flange 67 covering a corresponding zone of said annular projection, as shown in Figs. 5 and 7. This flange 67 gives said cup 6 the possibility of some axial movement, as required by the allowed tolerances to the length of the lamp cap, while maintaining pins 811 of said cap constantly in engagement simultaneously with cup 6 and body 5 and thereby avoiding that said pins can penetrate into the interstice between the two elements 5 and 6.

Such a detrimental possibility can be avoided in various other ways such as, for example, those shown in Figs. 9a, 9b, 9c, 10, 11, 12 and 13.

In Figs. 9a, 9b and 9c said flange 67 is replaced by two metal fork inserts 671.

In Fig. 10, this flange instead of being fast or integral with cup 6 is part of round projection 52 of body 5 and is designated at 524.

In Fig. 1I, said cup 6 has higher walls and entirely occupies the space between round projection 52 of body 5 and plate 3, whereby axial movements are not allowed. The interstices between the parts are only those as required for allowing rotational movement between the parts, and accordingly said pins 811 cannot penetrate thereinto. The cup further has on the bottom a pin 621 which is inserted in a proper plate 3 in order to promote a quite balanced rotation.

In Figs. 12 and 13, cup 6 also entirely occupies the space between round projection 52 of body 5 and plate 3, but has a movable bottom 68, which is axially slidable and accommodates the changes in length due to the admitted tolerances of the lamp cap. Also in this case the interstices between the parts are minimized and pins 811 are prevented from penetrating thereinto.

Plate 3 is similar to that of the conventional bayonet lampholders, with the terminals 7 on one of its faces or sides and contacts 4 and relative inner springs 41 projecting from the opposite face or side.

However, at inoperative position, contacts 4 have the end thereof accommodated under pressure in the circular impressions 62 of cup 6.

The operation ol the lampholder provided with a contact protecting device as above described is as follows.

At rest position, Figs. 5, 6, 9a, 9b, 9c, 10, 12 and 13, contacts 4, as accommodated in said round prints 62 are shielded and inaccessible, the surfacing holes 63 on the bottom of cup 6 are remote from the contacts, and may be displaced by 90" relative to said round prints 62. At the same time, on lampholder fit, slits 61 of cup 6 and slits 521 of round projection 52 of body 5 are coincident and located on the same plane of the axes of contacts 4. In turn, resting points 522 may be positioned at 900 relative to said slits and are on the axes of surfacing holes 63 of the cup bottom. When the lamp is inserted by axial movement, as in conventional bayonet lampholders, the cap pins 811 are forced to the bottom of slits 61 of cup 6. Under such situation, contacts 812 of lamp cap 81 coincide with surfacing holes 63 of the cup bottom, but are displaced by 90" relative to lampholder contacts 4 which, however, are shielded. Therefore, no possibility of lighting exists as the lamp is linearly inserted. When the lamp is rotated in clockwise or counterclockwise direction, pins 811 draw said cup 6 until contact 4 are coincident with surfacing holes 63 (Figs. 7, 8 and 11). Under the pushing action of springs 41, contacts 4 extend from the bottom of cup 6 until contacting with the required pressure said lamp cap contacts 812, which were previously registered with the surfacing holes of the cup bottom. At the same time, pins 811 are urged into resting points 522 and the lamp remains firmly secured in the lampholder at active operating position. The lamp operated in exactly the same way as if it were connected to the prior art type of lampholder, and the cup has a sufficient clearance not to interfere with the contact pressure.

The return to inoperative position is provided by a successive rotation of the lamp, in the same direction of the former or in opposite direction, which causes contacts to retract or move back to the rest position, the movement being aided by the tapering of the holes and that of the contact end.

When the contacts 4 reach the rest seats 62 thereof on the cup bottom, said slits 61 of the cup and slits 521 in the round projection of the body are again coincident and the lamp can be removed from the lampholder.

Claims (15)

WHAT WE CLAIM IS:

1. A bayonet lampholder comprising a housing body for holding the base of a lamp bulb, the housing carrying electrical contacts for cooperation with contacts on the base of the lamp when it is inserted in the housing, the housing having an annular rim defining a reduced diameter inlet at its open end in which opposed slits are provided for insertion of the bulb pins, resting points for the pins being provided on the undersurface of the rim at a separation of 90" from the inner ends of the inlet slits, such that a lamp base, when inserted through the slits, can be rotated in either a clockwise or counterclockwise direction until the pins are located in the resting points, at which position the lamp contacts cooperate with the lampholder contacts.

2. A lampholder according to claim 1, in which a protective device is provided comprising a cup of insulating material with its bottom having two holes, and its cylindrical portion facing outwardly having slits corresponding to the slits in the annular rim, insertion of the lamp pins and rotation of the lamp causing said cup to rotate relative to the lampholder contacts between an inoperative position, in which the current carrying contacts are shielded and inaccessible beneath the cup bottom, and an active or operating position, in which said contacts extend from said holes to cooperate with the lamp contacts.

3. A lampholder according to claim 2, wherein the contacts are urged outwardly through the holes in the operative position by a spring located therein and tend to be urged back to retracted position when the cup is rotated from the operative position by engagement of tapered ends of the contacts with corresponding tapered walls of the holes.

4. A lampholder according to claim 3, wherein the minimum diameter of said holes on the cup bottom is less than the maximum diameter of the contacts which, while enabling surfacing of the tapered contact ends, does not allow a complete extension of said contacts out of said holes

5. A lampholder according to any claims 2 to 4, in which the lampholder contacts are provided with a collar to prevent their full extension out of the cup holes.

6. A lampholder according to any of claims 2 to 5 in which the cup bottom acting as a shield has two circular imprints at the inoperative position of said cup with respect to the contact, these imprints accommodating therein said contacts under pressure, thus establishing a definite angular positioning at inoperative position and preventing said cup from being rotated by the fingers.

7. A lampholder according to claim 6, wherein the shielding element or cup is held in place at inoperative position by the resilient pressure of the contacts pressing the cup brim against the undersurface of the annular rim at the lampholder body inlet, or the bottom flange of said cup against the square ridge of the body, the angular position of the cup being determined by the contacts accommodated under pressure in said imprints, which avoids any possibility of rotating said cup by the use of fingers.

8. A lampholder according to any of claims 2 to 7 wherein means are also provided for taking up the clearances in said operating or controlling member, according to the tolerances allowed for example between the pins and the side of the contacts of the cap of a lamp.

9. A lampholder according to Claim 8, wherein the means for taking up the clearances comprise a flange which is part of the cup or body.

10. A lampholder according to Claim 8, wherein the means for taking up the clearances comprise two metal fork inserts.

11. A lampholder according to Claim 8 wherein the means for taking up the clearance comprise a cup having a movable bottom, the walls of which completely occupy the space between the annular rim of the body and the contact holder plate, the movable bottom of said cup being suitable to compensate for the allowed tolerances.

12. A lampholder according to Claim 8, wherein the means for taking up said clearances comprises a pin cup having high walls entirely occupying the space between said annular rim of the body and contact holder plate, the changes allowed in the length of the lamp connection being directly compensated for by the changes in extension of the contacts from the cup bottom.

13. A lampholder according to any of claims 2 to 12 wherein said annular rim of the body encloses the cup brim which accordingly cannot be reached by the fingers, this contributing to the stability of the cup at inoperative position, preventing any tampering thereof.

14. A lampholder according to any of claims 2 to 12 wherein in a lampholder provided with contact shielding the rotation of the cup between inoperative and operative positions is limited by stops within predetermined angular sectors, for example by providing recessing sectors in the cup and respective ridges in the body, or vice versa.

15. A lampholder substantially as hereinbefore described with reference to the accompanying drawings.