EP0139510A2

EP0139510A2 - Bulb holder

Info

Publication number: EP0139510A2
Application number: EP84306948A
Authority: EP
Inventors: John Nigel Madeley
Original assignee: TRW Connectors Ltd
Current assignee: TRW Connectors Ltd
Priority date: 1983-10-11
Filing date: 1984-10-11
Publication date: 1985-05-02
Also published as: EP0139510A3; GB8327162D0; GB2147985A

Abstract

A bulb holder for a wedge base miniature bulb having a recess in a side surface of the base, the holder comprising a housing having a cavity for receiving the base of a bulb, electrical contact means in the cavity and for contacting the bulb, retaining means provided in the cavity comprising at least one substantially inflexible tongue engagable in the recess and resilient retaining means arranged to cooperate with the tongue to allow easy insertion of the bulb into the housing but to restrict subsequent removal of the bulb from the housing.

Description

The present invention relates to a bulb holder for a miniature bulb, for example, as used on facia panels of motor vehicles. Such bulbs are constructed with a "wedge base" that is, they comprise a base which is a flattened glass wedge which can fit in a holder by push fitting, with wedging engagement of the wedge base of the bulb and the cavity of the holder.
The bulbs have a capsule containing a filament and a base in the form of a stem. Electrical contact wires are fused in the stem and lead to the filament. There are exposed portions of the electrical contact wires on the stem for making electrical contact with conducting portions in the bulb holder.
Many known wedge base bulb holders are designed so that a bulb is easily insertable into the holder and can be removed relatively easily for replacement.
In known practice, the bulb is configured to be retained in a bulb holder between two similar facing contact elements. The contact elements have resilient portions which deform to permit insertion of the bulb into the bulb holder and which grip the wedge base of the bulb to retain it in the bulb holder, e.g. by extending into recesses in side surfaces of the bulb base.
UK Patent No. 1464598 discloses a wedge base bulb holder comprising a housing having a cavity for accommodating a bulb and two similar facing sheet metal contact elements engaged in the housing. Each of the contact elements has an inwardly projecting U-shaped portion which is open upwardly. The U-shaped portions deform and grip the wedge base of a bulb inserted into the housing. Arcuate free ends of each of the U-shaped members engage in recesses in the bulb base to resist removal of the bulb. However, by firmly gripping the bulb capsule and pulling, the bulb base can be freed from the U-shaped portions and the bulb removed from the holder.
US Patent No. 3206708 discloses a bulb holder in which a bulb stem is held between two similar facing contact elements in a cavity in a housing. The bulb stem has diagonally opposed studs which ride over resilient fingers on the contact members -during insertion. The stpds latch underneath the fingers to prevent the bulb being pulled out of the housing. The studs can be freed from the contact elements simply by rotating the bulb to disengage the studs from the contact elements and the bulb can then easily be removed from the housing.
In practice, it has been found that vibrations for example in a motor vehicle body, adversely affect the quality of the electrical connections between the bulb and the bulb holder. To counteract this problem, it has been the practice to solder the electrical connections between the bulb and the bulb holder. However, as this method involves welding, it is relatively costly and complicated from a manufacturing point of view.
According to the present invention, there is provided a bulb holder for a wedge base miniature bulb having a recess in a side surface of the base, the holder comprising a housing having a cavity for receiving the base of a bulb, electrical contact means in the cavity for contacting the bulb, characterised by retaining means provided in the cavity comprising at least one substantially inflexible tongue engagable in the recess and resilient retaining means arranged to co-operate with the tongue to allow easy insertion of the bulb into the housing but to restrict subsequent removal of the bulb from the housing.
An advantage of the present invention is that it provides a bulb holder into which a bulb can quickly and easily be inserted and positively retained thereby ensuring reliable electrical connection of the bulb and being suitable for use in situations where a bulb is subject to vibration.
Preferably, the or each tongue has an upper angled lead-in edge portion to facilitate insertion of the bulb into the holder and a bottom edge sufficiently extensive to restrict removal of the bulb.
The retaining means may comprise a pair of similar contact elements formed from sheet metal, each having a substantially inflexible tongue,and a resilient leg forming the resilient retaining means, extending within the cavity, the legs being deformable during insertion of the bulb to permit passage of the base of the bulb, with the tongue latching into a pair of similar recesses provided in the base of the bulb.
Alternatively, the retaining means may comprise a contact element formed from sheet metal and having a substantially inflexible tongue, and a resilient leg, providing the resilient retaining means, extending within the cavity, the leg being deformable during insertion of the bulb to permit passage of the base of the bulb, with the tongue latching into the recess in the base of the bulb.
Optionally, the housing is of moulded plastics material and includes one or more formations which are resiliently deformable to permit some twisting of the bulb during insertion, and to resist twisting of the bulb in the housing after insertion.
Particular embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which; -

Figure 1 is a front view of a bulb for use with a bulb holder according to the present invention;
Figure 2 is an underneath plan view of the bulb shown in Figure 1;
Figure 3 is a front view of a contact element of a i bulb holder'accordina to the present invention;
Figure 4 is a side view of the contact element of Figure 3;
Figure 5 is a plan view taken from above of the contact element shown in Figure 3;
Figure 6 is a front view of the housing of a bulb holder according to the present invention;
Figure 7 is a side view in cross section along the line VII - VII of the housing shown in Figure 6 with a contact element positioned for insertion into the housing;
Figure 8 is a plan view of the housing in which two contact elements are positioned;
Figure 9 is a view corresponding to Figure 8 with the position of the bulb shown in dotted lines;
Figure 10 is a front view of the housing in cross section and comprising two contact elements and showing the bulb positioned for insertion into the housing;
Figure 11 is a view corresponding to Figure 10 showing the bulb after insertion;
Figure 12 is a front view of a modified contact element for use in a bulb holder according to the present invention;
Figure 13 is a plan view from above of the contact element of Figure 12;
Figure 14 is a plan view of a housing in which two of the contact element shown in Figures 12 and 13 are positioned;
Figure 15 is a side view in cross section along the line XV - XV of Figure 14.

Referring to Figure 1 and Figure 2, a glass bulb, indicated generally at 10, has a wedge base 12 of width a approximately equal to 5mm. The base 12 comprises a stem 14 and a rounded tip 16. The bulb 10 comprises a capsule 18 containing a filament (not shown).
Figure 2 shows that the stem 14 has a generally cylindrical middle portion 20 contiguous with squared off side portions 22 and 24. Two contact wires 26 and 28 are fused into the stem 14 and have their free ends bent upwardly along the side portions 22 and 24 respectively. Each of the side portions 22 and 24 is provided with a generally cuboid recess 30, 32 (shown dotted in Figure 21 The recesses 30 and 32 are diagonally opposed on the bulb stem 14 and each lies on an opposite face of the stem 14 to the exposed part of one of the contact wires 26, 28.
Referring to Figures 3-5, a sheet metal contact element 34 e.g. of nickel plated carbon steel has a generally flat body portion 35 having a resilient lea 36, a substantially inflexible tongue 38 and a stiff resilient finger 40 stamped therefrom. The resilient leg 36 extends outwardly from the body 35 and has a free end 42 which is bent back towards the body 35 to form a V-shape providing a rounded contact portion 44.
The tongue 38 is partly rectangular with an angled edge 46, a vertical edge 47 and a bottom edge 47a. The tongue 38 is bent out of the plane of the body 35 and extends perpendicularly thereto. The tongue 38 extends from the opposite side of the body 35 to the resilient leg 36.
The rectangular finger 40 which is longitudinally slightly off-centre in the body,35, (as viewed in Figure 3), is cut out from the body 35 and bent away therefrom on the opposite side and in the opposite direction to the resilient leg 36. The uppermost part of the body 35 comprises two rectangular side arms 48 and 49 and terminates in a rounded tab 50 having a hemispherical contact head 51 thereon.' The tab 50 extends upwardly away from the body 35 at an obtuse angle and In the opposite direction to the resilient leg 36.
Referring-to Figures 6-11, a generally square cylindrical plastics housing is indicated at 52. The housing 52 is hollow and comprises a base wall 53 which is integral with four upstanding side walls 54, 55, 56 and 57. The side walls 55 and 57 terminate in two part circular diametrically opposed generally arcuate flanges 58 and 59. Each of the flanges 58, 59 comprises a channelled lateral protrusion 60, 61. There is also an upwardly extending ramp 62, 63 disposed on each flange 58, 59 in diametrically opposed relationship.
The side walls 54 and 56 of the housing 52 terminate in two upstanding, arcuate walls 64, 65 each provided with a laterally extending wedge shaped member 66, 67 each of which overlies a gap between the ends of the flanges 58 and 59. In plan view, the walls 64, 65 each comprise a segment 68 of a circle contiguous with a generally triangular ridge 69 (see Figure 8).
The side walls 55 and 57 are each formed with a slot 70, 71 extending upwardly from the base wall 58. The slots 70, 71 are partially offset from one another both being positioned off-centre in the walls 55 and 57 respectively. A thickened lip 72, 73 is provided in the walls 55 and 57 adjacent the top of each of the slots 70, 71 (see Figure 10).
There is a rib 74, 75 provided in each wall 55, 57, the ribs 74, 75 being offset, each extending from one side of the top of each slot 70, 71 up to the channelled protrusions 60, 61.
The walls 55, 57 have offset thickened lower portions 76, 77 alongside one side of each of the slots 70, 71 contiguous with relatively thin upper portions 78, 79.
The interior of the housing 52 has symmetry and is arranged to receive and retain two of the contact elements 34 in facing relationship so that each contact element 34 faces inwardly in the housing 52.
The interior of the hollow housing 52 comprises → two opposed resilient members 80, 81 which extend upwardly from the base wall 53 of the housing. The members 80, 81 have arcuate facing surfaces 82, 83 and each partially overlies one of the slots 70, 71 formed in the walls 55 and 57 of the housing 52.
The side walls 54 and 56 provide two opposed, slightly offset semi-resilient vertical ribs 84, 85 having chamferred uppermost ends 86, 87. The ribs 84, 85 extend to approximately the same height as the members 80, 81.
On the side walls 54 and 56 respectively, there are two diametrically opposed full length ribs 88, 89 extending parallel to the ribs 84 and 85 and joined at their lower ends 88 and 89 to the members 80, 81 by webs 90, 91 respectively. The ribs 88 and 89 each define a longitudinal groove not shown with the triangular ridges 69 of the arcuate walls 64 and 65. There is also a short, thick rib 92, 93 at the base of each, wall 54, 56 aligned with the members 80 and 81 respectively.
A contact element 34 is inserted into the housing 52, as indicated by the arrow in Figure 7, by sliding the body 35 of the contact element 34 between one of the resilient members 80 in the interior of the housing and the slot 70 adjacent that member. As the stiff resilient finger 40 is slid downwardly so that it clears the top of the slot 70 it springs outwardly into the slot 71 to abut the lip 72 in the side wall 55 of the housing 52 to prevent removal of contact element 34 from the housing 52 (see Figure 10).
The tab 50 of the contact element'34 lies in the channel in the protrusion 60 in the flange 58 when the contact element 34 is fully inserted into the housing 52. The side arm 48 of the contact element 34 nests in the recess provided between the rib 88 and the triangular ridge 69 on the wall 64. The resilient leg 36 and the tongue 38 of the contact element 34 extend toward the centre of the housing 52 on either side of the member 80. The body 35 of the contact member 34 abuts the thickened portion 76 of the wall 55 of the housing and is firmly held in position between the wall 55 and the member 80.
A second contact member 34 can be positioned adjacent the side wall 57 in a similar manner to face inwardly in the housing 52.
The housing 52 can be mounted on a conductive support surface, such as a printed circuit board, by inserting the top of the housing 52 through an aperture in the board and rotating the housing so that the board is progressively wedged more tightly between the two pairs 66, 62 and 67,'63 of a wedge shaped member and a ramp respectively. This rotation brings the hemispherical contact head 51 on the tab 50 of the contact element 34 into pressing engagement with the appropriate circuit pad on the printed circuit board or with the relevant conductive area on the conductive support surface as appropriate.
Referring to Figure 8-11, the bulb 10 is inserted into the housing 52 along an axis of insertion indicated by the arrow in Figure 10 so that the recesses 30 and 32 are aligned with the tongue 38 on each of the contact elements 34 and the exposed contact wires 26 and 28 are aligned with the resilient leg 36 on the facing contact elements 34. During insertion, the bulb 10 needs to be rotated slightly abut the axis of insertion to enable the lower part of the stem 14 of the bulb 10 to pass by the tongues 38. This rotation is permitted by flexing of the resilient legs 36 and is guided by the angled lead-in edge 46. The tongue 38 on one of the contact elements 34 thereby effectively co-operates with the resilient leg on the other contact element 34 during insertion of the bulb 10. The lower part of the bulb.stem 14 rides over the lead-in edges 46 of each of the tongues 38 and the tongues 38 then latch into the recesses 30 and 32 in mating engagement therewith. The vertical edge 47 of each tongue 38 abuts a vertical surface of the recesses 30, 32 and upward movement of the bulb 10 out of the housing 52 is prevented by bottom edge 47a of the tongue 38. The rounded contact portions 44 on the resilient legs 36 abut the electrical contact wires 26 and 28 on the bulb stem 14.
Due to the inflexible nature of the pair of tongues 38 and the absence of any angled surface or chamfer in the bottom edge 47a of the contact elements 34, any removal of the bulb 10, would necessitate the bulb being rotated anticlockwise about the axis of insertion sufficiently for the lower part of the stem 14 to clear the bottom edge 47a of each of the tongues 38. The distance between the ribs 84, 85 on the side walls 54 and 56 is approximately equal to the width a of the bulb stem 14 so that the ribs 84, 85 resist rotation of the bulb stem 14 once insertion is complete. The ribs 84, 85, being of semi-resilient material, do deform slightly to permit rotation of the bulb stem 14 during insertion of the bulb 10 into the housing 52, but then resile to create sufficient pressure to resist rotation of the bulb stem 14 once insertion is complete. After insertion, it is much more difficult to obtain a good grip on the bulb 10 as only a part of the bulb capsule 18 then protudes from the housing 52.
Therefore, by means of engagement of the two tongues 38 in the diagonally opposed recesses 30 and 32 in the bulb stem 14 and the interaction of the ribs 84, 85 with the bulb stem 14, the bulb 10 is positively retained in the housing 52 thus ensuring good electrical connection between the contact wires 26 and 28 and the contact elements 34. The bulb 10 thus retained cannot be dislodged from the housing 52 by means of vibration or by any person endeavouring to remove the bulb 10.
Figures 12 and 13 show a modified contact element 100 having a sheet metal, generally rectangular body 102 and a rounded tab 104 angled relative to the body 102 and having an hemispherical contact head 106 extending from the uppermost part of the body 102. The contact element 100 comprises a resilient leg 108 contiguous with the base of the body 102 and which is a similar shape to the resilient leg 26 of the contact / element 34 previously described but which is bent into a V-shape orientated to extend sideways across the body 102 rather than away from it. Resilient leg 108 has a rounded contact portion 110 which faces a substantially inflexible tongue 112 which is bent from one side of the body 102 to overlie the body 102 and extend parallel therewith. The tongue 112 is the same shape as the tongue 38 described in connection with the contact element 34. The contact element 100 also has a stiff resilient finger 113 located off-centre in the lower part of the body 102.
Figures 14 and 15 show two of the contact elements 100 in position in a housing 114 with the base of a hulb 10 shown dotted in Figure 14, the contact wires 26 and 28 on the bulb base also being shown. The external features of the housing 114 are similar to those of the housing 52 previously described except that the housing 114 has two upper arcuate walls 116 and 118 which terminate in triangular ridges 120, 121, 122 and 123 at both ends to provide a cavity for a bulb which is generally square in plan view. The internal configuration within the bulb cavity differs from that of the housing 52.
A contact element 100 is inserted into the housing 114 in the same manner as described for the contact element 34 being inserted into the housing 52 and will not be redescribed. There are two offset upstanding blocks 124, 125 disposed in the housing 114 which are positioned to locate between a resilient leg 108 of one of the contact elements 100 and the tongue 112 of the other of the contact elements 100 in the housing 114 so as to maintain the contact elements 100 in facing relationship in the housing 114. The blocks 124, 125 extend from the base of the housing 114 upwardly along approximately half the total height of the housing 114 and are bevelled at their uppermost ends 124a and 125a.
_. It is envisaged optionally to provide the contact elements 100 with a rib 101 press formed in the body 102 and positioned between the resilient leg 108 and the tongue 112. The rib 101 is not shown in Figure 12 or Figure 13 but is indicated in Figure 14 and Figure 15 only.
The bulb 10 is inserted into the housing 114 by aligning the side portions 22 and 24 on the bulb stem 14 with the tabs 104 of the contact elements 100 (that is, turning the bulb through 90° compared to its position relative to the housing 52 as shown in Figure 10). The recesses 30 and 32 in the bulb stem 14 are then aligned with the tongues 112 on the contact elements 100 and the contact wires 26, 28 are aligned with the contact portions 110 of the resilient legs 108 of the contact elements 100.
The bulb 10 is inserted into the housing 114 in a manner similar to that described with respect to the housing 52. Namely, the bulb 10 is rotated anticlockwise slightly to allow the lower portion of the stem 14 to pass downwardly past the tongues 112. The rotation is permitted by flexing of the resilient legs 108. In this embodiment, the resilient legs 108 on each of the contact elements 100 co-operate with the tongue 112 on the same contact element 100 during insertion of the bulbs. As insertion is continued, the tongues 112 latch into the recesses 30 and 32 in the bulb stem 14 positively to retain the bulb 10 in the housing 114 against upward movement.
Once the bulb 10 has been fully inserted into the housing 114, it is very difficult to grip the portion of the capsule of the bulb 10 which protrudes from the housing 114 firmly enough to rotate a bulb 10 sufficiently to remove the bulb 10 from the housing 114.
In the case where the ribs 101 are provided, some rotation of the bulb 10 during insertion is permitted by flexing of the body 102 of each of the contact elements 100 as the base of the bulb 10 pushes against the ribs 101. After insertion is complete, the ribs 101 abut the base of the bulb (see Figure 14) and help prevent rotation of the bulb 10 in the housing 114.
A single contact element of the type shown in Figures 12 and 13 may be used in a bulb holder of the present invention since the resilient leg and the tongue on the same contact element co-operate to retain a bulb. In this case, further formations in the cavity to resist twisting of the bulb after insertion would be desirable.
It is envisaged to extend the uppermost part of the housing of a bulb holder of the present invention as a skirt so that even less of the bulb capsule 18 protrudes from the housing to reduce even further the grippable length of the bulb when it is in position in the housing. The skirt would be configured so as not to provide a noticable shielding effect of the light from the bulb 10.
The particular bulb holder previously described may be used in the facia panel of a motor vehicle for the purpose of instrument illumination. The secure retention of the bulb will ensure that vibration in the vehicle body does not dislodge the bulb from the housing. In the event that the bulb needs replacing, the housing of the bulb holder is rotated to detach it from its support panel and is replaced by another housing with a new bulb.

Claims

1. A bulb holder for a wedge base miniature bulb (10) having a recess (30, 32) in a side surface of the base (12), the holder comprising a housing (52) having a cavity for receiving the base (12) of a bulb (10) and electrical contact means (34) in the cavity for contacting the bulb (10) characterised by retaining means provided in the cavity comprising at least one substantially inflexible tongue (38) engagable in the recess (30, 32) and resilient retaining means (36) arranged to co-operate with the tongue (38) to allow easy insertion of the bulb (10) into the housing (52) but to restrict subsequent removal of the bulb (10) from the housing (52).

2. A bulb holder as claimed in claim 1 characterised in that the or each tonuge (38) has an upper angled lead-in edge (46) to facilitate insertion of the bulb (10) into the housing (52) and a bottom edge (47a) sufficiently extensive to restrict removal of'the bulb (10).

3. A bulb holder as claimed in claim 1 or claim 2 characterised in that the retaining means comprises a pair of similar contact elements (34) formed from sheet metal, each having a substantially inflexible tongue (38) and a resilient leg (36), forming the resilient retaining means, extending within the cavity, the legs (36) being deformable during insertion of the bulb (10) to permit passage of the base (12) of the bulb (10), with the tongue (38) latching into a pair of similar recesses (30,32) provided in the base (12) of the bulb (10).

4. A bulb holder as claimed in claim 1 or claim 2 characterised in that the retaining means comprises a contact element (34) formed from sheet metal and having a substantially inflexible tongue (38) and a resilient leg (36), providing the resilient retaining means, extending within the cavity, the leg (36) being deformable during insertion of the bulb (10) to permit passage of the base (12) of the bulb (10), with the tongue (38) latching into the recess (30,32) in the base (12) of the bulb (10).

5. A bulb holder as claimed in claim 3 or claim 4 characterised in that the or each contact element (34) has a generally flat body portion (35), the resilient leg (36) extending from one surface of the body portion (35) which faces the cavity, adjacent one side edge, and the tongue (38) extending from the same surface of the body (35) adjacent the opposite side edge.

6. A bulb holder as claimed in claim 5 characterised in that the tongue (38) extends perpendicularly from the body portion (35) and the leg (36) is bent into a V-shape with the point of the V remote from the body portion (35).

7. A bulb holder as claimed in claim 5 characterised in that the tongue (38) is bent round to extend parallel to the body portion (35) and the leg (36) is bent into a V-shape extending alongside the body portion (35) with the point of the V facing the free end of the tongue (38).

8. A bulb holder as claimed in any of claims 5-7 characterised in that the generally flat body (35) of the or each contact element (34) comprises a formation (101) configured to resist twisting of the bulb (10) in the housing (52) after insertion.

9. A bulb holder as claimed in any preceding claim characterised in that the housing (52) is of moulded plastics material and includes one or more formations (84,85) which are resiliently deformable to permit some twisting of the bulb (10) during insertion, and to resist twisting of the bulb (10) in the housing (52) after insertion.

10. A bulb holder as claimed in any preceding claim positioned in a facia panel of a motor vehicle.