GB2326978A

GB2326978A - A switch

Info

Publication number: GB2326978A
Application number: GB9713957A
Authority: GB
Inventors: Matthew J Knox
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 1997-07-01
Filing date: 1997-07-01
Publication date: 1999-01-06
Also published as: GB9713957D0

Description

DESCRIPTION OF INVENTION "INPROVEMENTS IN OR RELATING TO A SWITCH" THE PRESENT INVENTION relates to a switch, and more particularly relates to a switch that may be of use in a vehicle safety belt buckle.

It is often necessary to incorporate a switch in a vehicle safety belt buckle, the switch being capable of indicating when the buckle is latched.

Such a switch may be located at a position within a safety belt buckle where the switch will be activated by a latch present in the buckle when the latch is in the position that it occupies when the latch is retaining a tongue within the buckle.

Such a switch must provide reliable operation, over a large number of cycles of operation. Also, the switch must be tolerant to excess movements of the latch. Thus, as the latch is moved to the latching position, the latch might move slightly beyond the normal latching position, and the switch must be capable of accommodating excess movements of this type.

The present invention seeks to provide an improved switch.

According to this invention there is provided a switch, the switch comprising a base, a first resilient element mounted on the base, and being connected to the base at spaced apart positions, the part of the resilient element between the spaced apart positions being arched above the base, a second resilient element mounted above the first resilient element, the second resilient element also being mounted in position at spaced apart positions, and having the part of the resilient element between the spaced apart positions arched to extend above the arched portion of the first resilient element, each resilient element carrying electrically conductive means on the surface thereof directed towards the other of said resilient elements, so that on the application of pressure to the second resilient element, the second resilient element moves so that the electrically conductive means thereon come into contact with the electrically conductive means on the first resilient element, thus closing the switch.

Preferably the first resilient element and the second resilient element are substantially circular in configuration, the first resilient element being mounted on the base at positions spaced about the periphery thereof, the second resilient element being connected to the first resilient element about the periphery thereof.

Conveniently the second resilient element is sealed to the first resilient element about the periphery of the second resilient element so that a space between the first resilient element and the second resilient element is hermetically sealed.

In one embodiment the space is connected to a resilient bladder.

Conveniently a substrate is provided located between the first resilient element and the base, the substrate carrying electrically conductive means, and wherein the under-surface of the first resilient element also carries electrically conductive means, so that on the application of sufficient pressure to the second resilient element, the first resilient element is deformed and the electrically conductive means on the under-surface of the first resilient element is brought into contact with the electrically conductive means on the substrate, thus closing a second switch.

Advantageously the electrically conductive means on one resilient element comprises two spaced apart conductive pads, each with an associated signal track, the pads being located to be brought into contact with a conductive pad on another resilient element aligned with the conductive pads to establish electrical connection between said pads.

The switch may be mounted in a buckle adapted to receive a tongue of a safety belt, the switch being adapted to be closed when the tongue is latched in position within the buckle.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: FIGURE 1 is a diagrammatic cross-sectional view of one embodiment of the invention, FIGURE 2 is a corresponding diagrammatic sectional view of an alternative embodiment of the invention, FIGURE 3 is a diagrammatic view of conductive elements printed on a flexible element forming part of a switch in accordance with the invention, FIGURE 4 is a sectional view through a seat belt buckle illustrating a switch in accordance with the invention mounted in the buckle, and FIGURE 5 is a sectional view of a modified switch.

Referring initially to Figure 1 of the accompanying drawings, a switch in accordance with the present invention comprises a rigid base 1. The base may form part of a larger component, such as a cover for a safety belt buckle.

Integrally formed with the base are two up-standing mounting posts 2,3. A first, lower resilient element 4 is provided. The resilient element 4 is formed of an appropriate resilient material which may, for example, comprise a plastics material. The resilient element 4 is provided with two apertures 5,6 which accommodate the mounting posts 2,3 so that the resilient element 4 is mounted in position at two spaced apart points.

The resilient element 4 is of arched configuration, and thus a central region of the resilient element 4 is spaced above the base 1. The upper surface of the resilient element 4 carries an electric conductor pad 7.

A second, upper resilient element 8 is provided, again formed of an appropriate resilient plastics material.

The upper resilient element 8 is again of arched configuration, and is mounted above the first resilient element 4. The second resilient element 8, in the illustrated embodiment, is secured to the lower resilient element 4 at spaced apart positions 9,10. It is envisaged that the upper resilient element 8 may be adhered or welded to the lower resilient element at the spaced apart positions 9,10.

The upper resilient element 8 is arched and the central region of the upper resilient elements is spaced above the central region of the lower resilient element 4.

The under-surface of the central region of the upper resilient element 8 carries an electric conductor pad 11, which is aligned with the conductor pad 7.

The lower resilient element 4 and the upper resilient element 8 could each, in a simple embodiment, comprise an elongate strip of resilient material, with each strip effectively being mounted in position by mounting means provided adjacent each end of the strip. In a possible alternative embodiment of the invention, each resilient element could be of cruciform configuration, each element having four arms, with the element being mounted in position provided adjacent the ends of the four arms.

However, in the most preferred embodiment of the invention, each resilient element 4,8 is a sheet of substantially circular form, with each resilient element being mounted in position by mounting means provided about the periphery of the upper resilient element. It is thus envisaged that there would be a plurality of mounting posts, such as the posts 2,3 located at evenly spaced positions about the periphery of the lower resilient element 4, and it is also envisaged that the upper resilient element 8 will be secured to the lower resilient element 4 about the total periphery of the resilient element 8. As a consequence of this, the space between the upper resilient element 8 and the lower resilient element 4, will be hermetically sealed.

Whilst, in the described embodiment, the upper resilient element 8 is actually secured to the lower resilient element 4, it is to be understood that in a modified embodiment of the invention, the upper resilient element 8 could also, or alternatively, be connected to the mounting posts 2,3 on which the lower resilient element 4 is mounted.

Each electric conductor pad 7,11 can be in the form of a metallic film or foil, such as a film or foil of silver which is present on the appropriate surface of the resilient plastic element 4 or 8. Appropriate signal tracks may be formed on the appropriate surface of one or both of the resilient elements which enable the conductor pads to form part of an electric circuit, so that when the two conductor pads 7 and 11 touch each other, the switch is closed and the electric circuit is completed.

The switch illustrated in Figure 1 is adapted to respond to downward movement of an element 12 which may, for example, comprise part of a latch in a buckle adapted to receive a tongue present on a motor vehicle safety belt.

If the element 12 moves downwardly, as indicated by the arrow 13, the upper resilient element 8 will be deformed slightly, thus bringing the electric conductor pad 11 into contact with the electric conductor pad 7, thus closing the switch. If the element 12 continues to move downwardly, the upper resilient element 8 and the lower resilient element 4 will both deform, thus accommodating any excess downward movement of the element 12. When the element 12 moves upwardly, the various components of the buckle will return to the condition illustrated in Figure 1.

In the embodiment where the lower and upper resilient elements 4 and 8 are of substantially circular form, with the upper resilient element 8 being bonded to the lower resilient element 4 about its entire periphery, the contact pads 7 and 11 are maintained within a sealed environment, with a consequence that there is only a very minimal risk of the contact pads being damaged by pollutants.

Figure 2 illustrates a modified embodiment of the invention. A large proportion of the features of the embodiment of Figure 2 correspond directly with features of the embodiment of Figure 1, and are identified with the same reference numerals and will not be re-described.

In the embodiment shown in Figure 2, the first flexible element is provided not only with an electric conductor pad 7 on its upper surface, but also with a further electric conductor pad 20 on its lower surface. A substrate 21 is provided located above the base 1 at a position between the base 1 and the resilient element 4.

The substrate 21 may be mounted to lie flat on the base 1 and thus need not be resilient. The substrate 21 carries a further electrically conductive pad 22. Pads 20 and 22 are associated with electrically conductive signal tracks provided so that an electric circuit can be completed when the pad 20 touches the pad 22. It is to be understood that in a modified embodiment the substrate 21 may be formed of the same material as the resilient elements 4 and 8 and may also be arched in the same way that the resilient elements 4 and 8 are arched, again to enable the switch to accommodate excess downward movement of the element 12.

It is to be appreciated that in operation of the switch illustrated in Figure 2, as the element 12 moves downwardly, initially the electric conductor pads 11 and 7 are brought into contact with each other, as in the manner described with reference to Figure 1, but continued downward movement of the element 12 will cause the electric conductor pad 20 to contact the electric conductor pad 22, thus completing a second circuit.

Figure 3 is a diagrammatic view illustrating the electric conductor pad 7 as provided on the resilient element 4. As can be seen in Figure 3, the pad 7 is formed of two separate semi-circular pad elements 25,26, and each pad element is associated with a respective signal track 27,28. This means that both the pad elements and both of the respective signal tracks are present on the resilient element 4. The conductor pad 11 provided on the resilient element 8 is of circular form, and is aligned to extend over both of the two semi-circular pad elements 25,26. Thus, when the resilient element 8 is deformed, the electric conductor pad 11 is brought into contact with both of the pad elements 25 and 26, thus establishing electrical contact between the two pad elements. It is to be appreciated that the electric conductor pad 20, (or the pad 22) may also have the configuration illustrated in Figure 3.

In alternative embodiments of the invention the electric conductor pad elements 7 and 11 may be of any convenient configuration, with each pad element being provided with a respective signal track associated with the respective flexible element.

Figure 4 is a cross-sectional view of a conventional safety belt buckle 30. The safety belt buckle 30, as is well known to those skilled in the art, defines a mouth 31 which has received a tongue 32 provided on a safety belt. The tongue 32 has been engaged by a latch 33 which is mounted within the buckle for movement between a tongue-engaging position (as shown) and a tonguerelease position. The latch 33 is actually retained in the tongue-engaging position by means of a transverse locking bar 34.

As can be seen, a portion 35 of the latch 33, which is substantially vertical in the orientation of the buckle as shown, passes through an aperture 36 formed in the tongue 32. A switch 37 of the type discussed above is mounted at such a position that the tip of the vertical portion 35 of the latch 33 touches the switch to close the switch when the latch is locked in the latching position.

Referring now to Figure 5 of the accompanying drawings, a modified switch is illustrated. The switch has a lower resilient element 4 and an upper resilient 8 as described with reference to Figure 1, with the lower resilient element 4 carrying a electric conductor pad 7 and the upper resilient element 8 carrying an electric conductor pad 11. The space 40 defined between the parts of the resilient elements 4 and 8 carrying the conductor pads is connected, by means of a channel 41, to a reservoir or bladder 42 which is formed in a region of the resilient elements 4 and 8 which is remote from the conductor pads 7 and 11.

It is to be appreciated that when the upper resilient element 8 is deformed, in the region of the conductor pad 11, to bring the conductor pad 11 into contact with the conductor pad 7, gas originally present within the space 40 will tend to become compressed. This gas passes through the duct 41 to the bladder 42 which swells. The arrangement of the bladder 42 is such that when the switch is activated, the pressure that is present within the space 40 is not sufficient to damage the bond between the upper resilient element 8 and the lower resilient element 4.

Claims

CLAIMS:

1. A switch, the switch comprising a base, a first resilient element mounted on the base, and being connected to the base at spaced apart positions, the part of the resilient element between the spaced apart positions being arched above the base, a second resilient element mounted above the first resilient element, the second resilient element also being mounted in position at spaced apart positions, and having the part of the resilient element between the spaced apart positions arched to extend above the arched portion of the first resilient element, each resilient element carrying electrically conductive means on the surface thereof directed towards the other of said resilient elements, so that on the application of pressure to the second resilient element, the second resilient element moves so that the electrically conductive means thereon come into contact with the electrically conductive means on the first resilient element, thus closing the switch.

2. A switch according to Claim 1 wherein the first resilient element and the second resilient element are substantially circular in configuration, the first resilient element being mounted on the base at positions spaced about the periphery thereof, the second resilient element being connected to the first resilient element about the periphery thereof.

3. A switch according to Claim 2 wherein the second resilient element is sealed to the first resilient element about the periphery of the second resilient element so that a space between the first resilient element and the second resilient element is hermetically sealed.

4. A switch according to Claim 4 wherein the space is connected to a resilient bladder.

5. A switch according to any one of the preceding Claims wherein a substrate is provided located between the first resilient element and the base, the substrate carrying electrically conductive means, and wherein the under-surface of the first resilient element also carries electrically conductive means, so that on the application of sufficient pressure to the second resilient element, the first resilient element is deformed and the electrically conductive means on the under-surface of the first resilient element is brought into contact with the electrically conductive means on the substrate, thus closing a second switch.

6. A switch according to any one of the preceding Claims wherein the electrically conductive means on one resilient element comprises two spaced apart conductive pads, each with an associated signal track, the pads being located to be brought into contact with a conductive pad, on another resilient element aligned with the conductive pads to establish electrical connection between said pads.

7. A switch according to any one of the preceding Claims mounted in a buckle adapted to receive a tongue of a safety belt, the switch being adapted to be closed when the tongue is latched in position within the buckle.

8. A safety belt buckle incorporating a switch according to any one of Claims 1 to 6.

9. A switch substantially as herein described with reference to and as shown in Figure 1 and 3 of the accompanying drawings.

10. A switch substantially as herein described with reference to and as shown in Figures 2 and 3 of the accompanying drawings.

11. A safety belt buckle provided with a switch substantially as herein described with reference to and as shown in Figure 4 of the accompanying drawings.

12. Any novel feature or combination of features disclosed herein.

12. A switch substantially as herein described with reference to and as shown in Figure 5 of the accompanying drawings.