GB2089957A

GB2089957A - Headlamp for motor vehicles

Info

Publication number: GB2089957A
Application number: GB8138036A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1980-12-24
Filing date: 1981-12-17
Publication date: 1982-06-30
Also published as: FR2496839A1; DE3048969C2; GB2089957B; FR2496839B1; DE3048969A1

Abstract

A headlamp housing for motor vehicles has a cap (10) having a perpendicular passage (16) whose top opening extends upwardly so that in use it lies in the path of air moving over the cap and is chamfered such that suction is produced in the passage during forward travel of the vehicle. In order to prevent condensation from settling in the cap, a tubular member (21) interconnects the passage (16) and the interior (14) of the cap (10), the cap (10) having an annular passage (12) communicating at its lower end with the atmosphere via slots (13) at its upper end and with the interior space (14) via grooves 15. Movement of air between the interior space (14) and the atmosphere takes place when the headlamp is switched on and off. When the vehicle is travelling, air flows through the interior space (14) as a result of atmospheric air flowing into the slots (13) and air flowing out of the interior space through the upper opening (17) of the passage (16). <IMAGE>

Description

SPECIFICATION Headlamp for motor vehicles The present invention is concerned with motor vehicle headlamps.

A motor vehicle headlamp is already known having a vertically disposed passage which is fixed relative to the headlamp housing and which has a rearwardly sloping upper opening whose front edge is arranged to lie in the path of air over the housing so that when the headlamp moves forwardly through such air a partial vacuum is established in the passage, at least one inlet for atmospheric air being located at the bottom of the housing and an outlet being provided for air to flow from the interior space within the housing into the vertically disposed passage.

The advantage of such a headlamp is that condensation on the interior surfaces of the headlamp is prevented by continuously drawing fresh air through the housing by means of the partial vacuum established in the housing interior as a result of the air movement over the upper opening of the vertical passage during forward travel and by the chimney effect or updraught in the passage when the vehicle is stationary.

It is an object of the present invention to improve the efficiency of such a headlamp in preventing condensation.

In accordance with the present invention there is provided a motor vehicle headlamp comprising a housing, a substantially vertically disposed passage which is fixed relative to the housing and which has a rearwardly sloping upper opening whose front edge is arranged to lie, in use, in the path of air over the housing so that when the headlamp moves forwardly through such air a partial vacuum is established in the passage, an outlet enabling air to flow from the interior space within the housing into said vertically disposed passage, an annular passage disposed around the housing, an inlet in the lower part of the annular passage for allowing atmospheric air to enter and an opening in the upper part of the annular passage providing communication between said annular passage and said interior space of the housing.

The construction in accordance with the invention has the advantage that it can prevent condensation forming within the headlamp housing in a greater number of adverse environmental conditions than the known headlamp.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a vertical section through one embodiment of a headlamp housing cap in accordance with the present invention with the section taken through the vertical passage on the line I-I of Fig. 2; Figure 2 is a partial vertical section through the passage and contiguous portions of the cap, taken on the line Il-Il of Figure 1; and Figure 3 is a vertical diametral section through the cap.

The plastics cover or cap 10 shown in the Figures is adapted to close an opening at the rear of a motor vehicle headlamp housing (not illustrated) by way of an annular seal 11. A groove closable by the annular seal 11 forms an annular passage 1 2 which communicates with the outer atmosphere by way of three slots 1 3 at the bottom of the cap 10, and with the interior 14 of the cap 10, and consequently with the housing (not illustrated), by way of two grooves 1 5 at the top of the cap.

A perpendicular passage 1 6 of substantially rectangular cross-sectional shape is integrally formed on the rear of the cap 10 and has an upper, rearwardly sloping opening 1 7 whose front edge 1 8 is positioned so as to extend into the wind path 19 caused when the vehicle travels in the direction of the arrow 20. The interior 14 of the cap 10 communicates with the passage 1 6 by way of a tubular member 21 having a chamfered end portion 22 whose upper projecting edge extends almost to the oppositely located wall 24 of the passage.A water deflector 25 of saddle-like configuration is mounted on the tubular member 21 such that water entering the opening 1 7 at the top of the passage 16, for example in a car wash, cannot enter the interior 14 of the cap 1 0 and consequently cannot enter the headlamp housing.

The passage 1 6 has a substantially rectangular cross section which is larger below the tubular member 21 than above it.

The circulation of air in the headlamp is as follows: When the motor vehicle is travelling in the direction 20, air movement (arrow 19) causes suction at the top opening 17, so that the air in the passage 1 6 is entrained and atmospheric air correspondingly flows into the bottom opening 29. This flow of air in the passage 16 causes suction at the tubular member 21, so that air is sucked out of the interior 14 of the cap 10 and is entrained by the air in the passage 1 6. The resultant partial vacuum in the interior space 1 4 causes atmospheric air to flow through the grooves 15, the annular passage 12 and the slots 13.

When the vehicle is stationary, a pressure difference, even though it is a very small pressure difference is caused at the two openings 1 7 and 29 by virtue of the height of the chimney formed by the passage 1 6 and, together with the movement of the atmospheric air at the opening 17, ensures a constant flow of air in the passage 1 6. Thus, air is removed from the interior of the headlamp by way of the tubular member 21 in the same manner as when the vehicle is travelling. Air compensation is effected by way of the annular passage 12.

1. A motor vehicle headlamp comprising a housing, a substantially vertically disposed passage which is fixed relative to the housing and which has a rearwardly sloping upper opening

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Headlamp for motor vehicles The present invention is concerned with motor vehicle headlamps. A motor vehicle headlamp is already known having a vertically disposed passage which is fixed relative to the headlamp housing and which has a rearwardly sloping upper opening whose front edge is arranged to lie in the path of air over the housing so that when the headlamp moves forwardly through such air a partial vacuum is established in the passage, at least one inlet for atmospheric air being located at the bottom of the housing and an outlet being provided for air to flow from the interior space within the housing into the vertically disposed passage. The advantage of such a headlamp is that condensation on the interior surfaces of the headlamp is prevented by continuously drawing fresh air through the housing by means of the partial vacuum established in the housing interior as a result of the air movement over the upper opening of the vertical passage during forward travel and by the chimney effect or updraught in the passage when the vehicle is stationary. It is an object of the present invention to improve the efficiency of such a headlamp in preventing condensation. In accordance with the present invention there is provided a motor vehicle headlamp comprising a housing, a substantially vertically disposed passage which is fixed relative to the housing and which has a rearwardly sloping upper opening whose front edge is arranged to lie, in use, in the path of air over the housing so that when the headlamp moves forwardly through such air a partial vacuum is established in the passage, an outlet enabling air to flow from the interior space within the housing into said vertically disposed passage, an annular passage disposed around the housing, an inlet in the lower part of the annular passage for allowing atmospheric air to enter and an opening in the upper part of the annular passage providing communication between said annular passage and said interior space of the housing. The construction in accordance with the invention has the advantage that it can prevent condensation forming within the headlamp housing in a greater number of adverse environmental conditions than the known headlamp. The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a vertical section through one embodiment of a headlamp housing cap in accordance with the present invention with the section taken through the vertical passage on the line I-I of Fig. 2; Figure 2 is a partial vertical section through the passage and contiguous portions of the cap, taken on the line Il-Il of Figure 1; and Figure 3 is a vertical diametral section through the cap. The plastics cover or cap 10 shown in the Figures is adapted to close an opening at the rear of a motor vehicle headlamp housing (not illustrated) by way of an annular seal 11. A groove closable by the annular seal 11 forms an annular passage 1 2 which communicates with the outer atmosphere by way of three slots 1 3 at the bottom of the cap 10, and with the interior 14 of the cap 10, and consequently with the housing (not illustrated), by way of two grooves 1 5 at the top of the cap. A perpendicular passage 1 6 of substantially rectangular cross-sectional shape is integrally formed on the rear of the cap 10 and has an upper, rearwardly sloping opening 1 7 whose front edge 1 8 is positioned so as to extend into the wind path 19 caused when the vehicle travels in the direction of the arrow 20. The interior 14 of the cap 10 communicates with the passage 1 6 by way of a tubular member 21 having a chamfered end portion 22 whose upper projecting edge extends almost to the oppositely located wall 24 of the passage.A water deflector 25 of saddle-like configuration is mounted on the tubular member 21 such that water entering the opening 1 7 at the top of the passage 16, for example in a car wash, cannot enter the interior 14 of the cap 1 0 and consequently cannot enter the headlamp housing. The passage 1 6 has a substantially rectangular cross section which is larger below the tubular member 21 than above it. The circulation of air in the headlamp is as follows: When the motor vehicle is travelling in the direction 20, air movement (arrow 19) causes suction at the top opening 17, so that the air in the passage 1 6 is entrained and atmospheric air correspondingly flows into the bottom opening 29. This flow of air in the passage 16 causes suction at the tubular member 21, so that air is sucked out of the interior 14 of the cap 10 and is entrained by the air in the passage 1 6. The resultant partial vacuum in the interior space 1 4 causes atmospheric air to flow through the grooves 15, the annular passage 12 and the slots 13. When the vehicle is stationary, a pressure difference, even though it is a very small pressure difference is caused at the two openings 1 7 and 29 by virtue of the height of the chimney formed by the passage 1 6 and, together with the movement of the atmospheric air at the opening 17, ensures a constant flow of air in the passage 1 6. Thus, air is removed from the interior of the headlamp by way of the tubular member 21 in the same manner as when the vehicle is travelling. Air compensation is effected by way of the annular passage 12. CLAIMS

1. A motor vehicle headlamp comprising a housing, a substantially vertically disposed passage which is fixed relative to the housing and which has a rearwardly sloping upper opening whose front edge is arranged to lie, in use, in the path of air over the housing so that when the headlamp moves forwardly through such air a partial vacuum is established in the passage, an outlet enabling air to flow from the interior space within the housing into said vertically disposed passage, an annular passage disposed around the housing, an inlet in the lower part of the annular passage for allowing atmospheric air to enter and an opening in the upper part of the annular passage providing communication between said annular passage and said interior space of the housing.

2. A headlamp as claimed in claim 1, wherein the housing includes a generally cup-shaped cap portion, said vertically disposed passage and said annular passage being carried by said cap portion.

3. A headlamp as claimed in claim 1 or 2, wherein said outlet is a tubular member which extends into the vertically disposed passage and whose configuration is such that water entering the upper opening of the passage does ndt enter the interior space of the headlamp housing.

4. A headlamp as claimed in claim 3, wherein the tubular member has a chamfered end piece whose upper projecting edge extends almost up to the oppositely located wail of the passage, and wherein a water deflector is disposed on the tubular member.

5. A headlamp as claimed in claim 4, wherein the water deflector is of saddle-like configuration.

6. A headlamp as claimed in claim 3, 4 or 5, wherein the cross-sectional area of the vertically disposed passage is greater below the tubular member than above it.

7. A headlamp as claimed in claim 5, wherein the vertically disposed passage is of substantially rectangular cross-section, and wherein the width of the passage fiom the tip of the saddle shaped water deflector downwardly is greater than that of the portion of the passage above said tip of the water deflector.

8. A headlamp as claimed in any of claims 2 to 7, whose cap is made from plastics material and wherein the passage and the cap are made in one piece.

9. A headlamp as claimed in any of claims 2 to 8, wherein the cap is formed with a plurality of slots which provide said inlet to the annular passage for atmospheric air and that a plurality of grooves connect the annular passage and the interior space of the cap.

10. A motor vehicle headlamp substantially as hereinbefore described with reference to the accompanying drawings.