GB2031576A

GB2031576A - Improvements in or relating to sealing caps for headlamps

Info

Publication number: GB2031576A
Application number: GB7931945A
Authority: GB
Original assignee: Cibie Projecteurs SA
Current assignee: Cibie Projecteurs SA
Priority date: 1978-09-15
Filing date: 1979-09-14
Publication date: 1980-04-23
Also published as: GB2031576B; JPS5541695A; FR2436334B1; BE878801A; FR2436334A1

Abstract

A sealing cap for the rear of a headlamp has an outer sealing lip 310 which bears against the rear of the headlamp reflector R, and an inner sealing lip 320 which also bears against the rear of the reflector, but which is elastically deformable and less rigid than the lip 310, so that it adapts to the shape of the reflector R and provides an effective seal, protected by the outer lip 310. A passage may be provided to connect the interior of the cap to the external atmosphere. <IMAGE>

Description

SPECIFICATION Improvements in or relating to sealing caps for headlamps This invention relates to sealing caps for fitting to the rear of vehicle headlamps, to protect the region in which the headlamp bulb is mounted. It is particularly but not exclusively applicable to sealing caps intended for fitting to headlamps incorporating pre-focus light units, consisting of a front lens and a reflector hermetically connected together.

Such sealing caps normally have a rim which bears against the rear of the reflector of the headlamp, and thereby provides a seal against the ingress of water, such as rain water. The present invention is concerned with the seal between the cap and the reflector.

Thus, according to one aspect of the invention, a protective cap for fitting to the rear of a vehicle headlamp has a peripheral annular sealing lip portion, which lip portion has an outer lip and an inner lip, the inner lip being thin and elastically deformable, to lie snugly against the rear of the headlamp, while the outer lip is, in comparison with the inner lip, relatively rigid, and projects beyond the inner lip.

With such an arrangement, the sealing lip portion should provide a good resistance to penetration by water jets, such as may be encountered in car washing operations or in heavy rainfall. The outer lip absorbs the main force of the water jets, while the inner lip provides a good seal to prevent further penetration of any water which may penetrate past the outer lip.

In the preferred embodiment, the inner and outer lips are circumferentially continuous, and the sealing cap includes a vent leading from the interior of the cap to the external atmosphere.

The invention may be carried into practice in various ways, but one specific embodiment will now be described by way of example, with reference to the accompanying drawings, of which: Figure lisa front view of a sealing cap embodying the invention and intended to be fitted to the rear of the reflector of a vehicle headlamp; Figure2 is a section on the line A-A in Figure 1; Figure 3 is a section through part of the sealing cap, taken on the line B in Figure 2; Figure 4 is a side view, half in section, showing the sealing cap fitted to the rear of a headlamp reflector; and Figure 4a is a view, corresponding to part of Figure 4, enlarged to show certain details of the sealing cap.

The sealing cap shown in the drawings is a one piece moulding; a typical material would be a synthetic elastomer with a Shore A hardness of between 50 and 70. The sealing cap has the general shape of a body of revolution about the axis A-A (Figure 2); it has a generally cylindrical central socket 101, which fits over the base of a headlamp bulb (not shown), a slightly dished wall 100 which extends outwards, approximately radially, around the socket 101, a short cylindrical portion 200 which is, in effect, a forward continuation of the wall 100 at its outer periphery, and a circular lip portion 300 which is attached to the forward end of the cylindrical portion 200.

The inner surface of the socket 101 has vee-shaped ribs 102, in order that the socket should fit firmly around the base of the headlamp bulb. The rear of the socket 101 is closed by a thin wall 103. The electrical connections to the headlamp bulb are in the form of three flat pins, and slots 103a are provided in the wall 103 to allow the passage of these pins; the size of the slots 103a is such that a water-tight seal between the wall 103 and the pins results. The seal between the ribs 102 and the lamp base is also water-tight.

The lip portion 300 includes an outer lip 310, and an inner lip 320 which lies within the outer lip 310, the free edge of the inner lip being set back from the free edge of the outer lip. The outer lip 310 is relatively thick and rigid. Its inner surface is, in this example, formed by the revolution about the axis A-A of an arc of radius Ri (see Figure 2); that is, the inner surface is part-spherical or part-toroidal. The inner lip 320 is much thinner and more flexible than the outer lip 310.

The sealing cap is fitted to the rear of a headlamp after the headlamp bulb has been fitted to the reflector of the headlamp. Figures 4 and 4a illustrate the reflector at R, fitted with the sealing cap, but omitting the headlamp bulb. The cap is held in place by its engagement with the base of the bulb, with the outer lip 310 in contact with the rear surface of the reflector R. In this position, the inner lip 320 has been elastically deflected by its contact with the reflector R, so that it contacts the reflector around an annular band, S (shown by a heavy line in Figure 4a), broader in radial extent than the contact between the outer lip 310 and the reflector R. The breadth of this contact band helps tp provide good sealing between the inner lip 320 and the reflector.At the same time, the outer lip 310 protects the inner lip 320, which, because of its thinness, is relatively delicate.

If the rear of the headlamp should be subjected to a jet of water, the relatively stiff outer lip 310 will prevent the full force of the jet being applied to the inner lip 320. Any water which does manage to pass the outer lip 310 should therefore be unable to pass the seal between the inner lip and the reflector.

As mentioned above, the outer lip 310 may be part-spherical in shape. The stress tin the wall of a complete hollow sphere of radius Ri and thickness e, subjected to an external pressure P, is given by the formula: t= P.Ri 2e Thus, if P is 3 bars, Riis 20 mm, and e is 2 mm, t will be 0.15 kgf/mm2. A typical elastomer would be capable of withstanding a stress of 0.85 kgf/mm2 without damage.

The seals provided by the lips 310 and 320 are unbroken annuli. A vent passage 350 is formed in a protrusion 360 on the rear of the lip portion 300, at the bottom of the sealing cap, to provide a limited communication between the interior of the cap and the atmosphere. The passage 350 communicates with the interior of the cap through a very narrow slot 351. The sealing cap is intended primarily for use with headlamps having pre-focus light units, in which a front lens is hermetically secured to the front opening of the reflector, and in this case, the passage 350 also vents the interior of the light unit.

The position of the passage 350 makes it almost impossible for water to reach the interior of the sealing cap through this passage. Also, the presence of the protrusion 360 does not affect the mechanical behaviour of the lips 310 and 320; as can be seen from Figure 2, the free edge 312 of the lip 310 is free of the protrusion 360.

It will be appreciated that the sealing cap could be held in place by other methods than being fitted around the base of the headlamp bulb.

Claims

1. A protective cap for fitting to the rear of a vehicle headlamp and having a peripheral annular sealing lip portion, which lip portion has an outer lip and an inner lip, the inner lip being thin and elastically deformable, to lie snugly against the rear of the headlamp, while the outer lip is, in comparison with the inner lip, relatively rigid, and projects beyond the inner lip.

2. A cap as claimed in Claim 1, in which the inner surface of the outer lip is the surface swept out by the revolution of a circular arc.

3. A cap as claimed in Claim 1 or Claim 2, which has an end wall with a socket for fitting around the base of a headlamp bulb.

4. A cap as claimed in Claim 3 in which the interior of the socket is ribbed.

5. A cap as claimed in Claim 3 or Claim 4, which includes a wall closing the rear end of the socket, and provided with one or more openings for electrical connections to the headlamp bulb.

6. A cap as claimed in any of the preceding Claims, in which the inner and outer lips are circumferentially continuous, and which includes a vent leading from the interior of the cap to the external atmosphere.

7. A cap as claimed in any of the preceding Claims, which is a one-piece moulding of a synthetic elastomer.

8. A protective cap for fitting to the rear of a headlamp, the cap being substantially as herein described, with reference to the accompanying drawings.

9. An assembly of a vehicle headlamp and a protective cap as claimed in any of the preceding Claims.

10. An assembly as claimed in Claim 9, in which the headlamp incorporates a pre-focus light unit of lens and reflector, the sealing lip portion sealing against the rear of the reflector.