GB2042701A

GB2042701A - Electric Cigarette Lighter

Info

Publication number: GB2042701A
Application number: GB8000884A
Authority: GB
Original assignee: IAO Industrie Riunite SpA
Current assignee: IAO Industrie Riunite SpA
Priority date: 1979-01-16
Filing date: 1980-01-10
Publication date: 1980-09-24
Also published as: GB2042701B; FR2446741A2; FR2446741B2; DE3000966C2; IT7967085A0; DE3000966A1; IT1165612B

Abstract

The electric cigarette lighter of patent specification no. 1564037 is modified in that the electrically conducting, fusible, annular body 40 is arranged externally in relation to the metal tubular body 10 so that spring 26 effects compression of the fusible annular body when it is softened through the heat produced by the lighter plug. <IMAGE>

Description

SPECIFICATION Electric Cigarette Lighter This invention relates to a cigarette lighter for motor vehicles.

In our co-pending application 50961/76 (Serial No. 1,564,037) an electric cigarette lighter for motor vehicles is described, of the type comprising a tubular metal body connectible to one pole of an electrical supply and having an aperture in an end wall, a contact unit connectible to the other pole of the electrical supply, said unit having a spring in the form of a bimetallic element for making and breaking an electrical contact (bimetallic gripper), the spring being supported by a conductive part such as a bolt traversing said aperture axially, and a support of electrically insulating and substantially refractory material fixed to the said end wall and axially traversed by said bolt, said bimetallic pincer being supported by the said wall without electrical contact with the latter.

For preventing damage which could be caused by accidental overheating of the cigarette lighter, it is proposed in the above patent application to arrange around the bolt an electrically conducting, fusible, annular body, having a melting point within the range 1200 to 3000 centigrade, the fusible body being normally out of electrical contact with the bolt and/or the end wall but having sufficient volume to make such a contact after melting. In the event of overheating, when the bolt and the wall are short-circuited, the fuse (normally included in the feeding circuit of the cigarette lighter) blows and interrupts the supply current.

An object of the present invention is to provide an improved structure in which, at least when the hot-plate of the cigarette lighter is in the heating position (that is, gripped by the bimetallic pincer), a resilient axial pressure is applied to the fusible annular body in order to compress the said body when the latter softens or melts through the effects the heat, in such a way as to produce, forciby, a flow of a softened or molten conductive mass into a position which short-circuits the part or bolt and the end wall.

According to the present invention there is provided an electric cigarette lighter for motor vehicles, comprising a tubular metal body housing a removal cigarette lighter plug, the body being connectible to one pole of an electrical supply and having an aperture in an end wall, a contact unit connectible to the other pole of the electrical supply, said unit having a spring in the form of a bimetallic element for making and breaking an electrical contact, the spring being supported by a conductive part such as a bolt traversing said aperture axially, a support of electrically insulating and substantially refractory material fixed to the said end wall and axially traversed by said part, said bimetallic element being supported by the said wall without electrical contact with the latter, and an electrically conducting, fusible, annular body arranged externally in relation to the end wall of the metal tubular body of the lighter, the lighter having resilient means which apply a pressure to the fusible annular body at least in the heating position of the lighter plug, said pressure being adapted in such manner as to effect compression of said fusible annular body only when the latter is softened through the heat produced by the lighter plug.

According to one embodiment, the resilient means comprise the return spring of the hotplate, normally present in cigarette lighters of the type referred to in the introduction. According to another embodiment, the resilient means comprise a compression spring acting between the fusible annular body and the external end of the axial part of the contact unit. The two embodiments may be combined if so desired.

For preference, the fusible annular body is housed in a recess of a metal cap which is in permanent electrical contact with the end wall or the axial bolt.

Preferably, the resilient means also act on the fusible annular body with the inter-positioning of an emergency contact member which is in permanent electrical contact with the axial bolt and is arranged in such a way as to short-circuit the bolt with the end wall in a final phase of the compression of the fusible annular body. Thus, if the melting of the fusible annular body does not lead, accidentally, to the desired short-circuiting, the latter can be produced in another way, to be precise, at the moment when the emergency contact member, compelled by the resilient means, comes into contact with the end wall or a component electrically connected to said wall.

Reference will now be made to the accompanying drawings, wherein:- Figure 1 is an axial section of a cigarette lighter according to an embodiment of the invention; Figure 2 is a fragmentary axial section of a variant of the Figure 1 embodiment.

As shown in Figure 1, the cigarette lighter 10 comprises a tubular cylindrical body, stamped in sheet metal and having an end wall 1 OA. Axially slidable in the body 10 of the lighter is a "lighter plug" (or extractable part) 12 which comprises a sheet metal sleeve 14 on the front end of which is fixed a knob 16. The rear end of the sleeve 14 has a peripheral bead 1 4A forming a stop which engages, in known manner, with resilient tongues 1 OB stamped with the body 10. A push button 18 is axially slidable in the sleeve 14, the front end of the push button 18 normally being within the axial limits of the knob 1 6 and the rear end being formed by a hot-plate 20 comprising a spiral resistive heating element.In the proximity of the hot-plate 20, the button 18 has a collar 22, whilst in the proximity of the front end a peripheral shoulder 24 is provided. A helical compression spring 26, coaxial with the button, abuts on one side against the shoulder 24 so as to react at the other end against an end of an annular sheet metal cap 28 slidable telescopically within the sleeve 14. The latter has an internal peripheral stop 1 4B against which the cap 28 bears. The spring 26 resiliently returns the button 1 8 towards the right of the Figure, to a rest position in which the collar 22 abuts the cap 28, as shown.The button 1 8 can be withdrawn outside of the plug 12 (together with the return spring 26 and the cap 28) for a short axial distance defined by tongues 14C pushed inwardly by the sleeve 14, against which the cap 28 bears during this withdrawal. An insulating refractory support 30 is fixed to the inside of the end wall 1 OA of the body 10, the support 30 having an axial bore and a cylindrical hub which engages in a central aperture 100 of the end wall 1 OA.The insulating support 30 is traversed axially by a conductive part in the form of a locking bolt 32, the head of which is inside the tubular body 10 and carries, in known manner, a bimetallic resilient gripper on pincer 34 which grips and retains the hot-plate 20 when the button 1 8 is pressed inwards against the action of the return spring 26.

The structure described above and its operation are known in the art and are described in the above mentioned patent application.

In the embodiment of the present invention, an annular sheet metal cap 36 is fixed to the outside of the body end wall 1 OA being centrally located on a hub of the insulating support 30, the rim of the cap 36 being turned outwardly to form a cylindrical wall to define a recess. The cap 36 has a tongue 36A, by means of which (through the cap 36) the tubular body 10 is connected to a negative pole of a motor vehicle battery 38. The cylindrical wall of cap 36 serves to locate substantially centrally an electrically conductive, fusible, annular body 40 which is in the form of a flat annular disc, the central aperture of which is sufficiently wide as to not produce an electrical contact between the annular body 40 and the bolt 32, whilst, on the other hand, the body 40 rests against the end of the cap 36 and is thus in permanent electrical contact with the latter.A washer 42 of refractory insulating material is threaded onto the bolt 32 to abut the external face of the fusible annular body 40, the washer being at least partially in the recess of the cap 36 and having an external diameter which is, preferably, at least equal to that of the fusible annular body 40 (without, however, being forcibly engaged in the cap 36). A metal washer 44 is threaded onto the bolt 32 so as to abut the external face of the insulating washer 44, all the parts traversed by the bolt being tightened by means of a nut 32B. It must be emphasised, at this point, that the fit of the bolt 32 within the insulating support 30 is sufficiently slack as to avoid the locking of the bolt in the support through the effect of friction.The metal washer 44 has a tongue 44A for the electrical connection of the bolt (and thence the bimetallic pincer 34) with a positive pole of the battery 38 through a conventional fuse 46 already provided in the motor vehicle for this purpose.

During operation, when the button 1 8 is forced to the end, the knob 1 6 is halted against a flange 1 OD of the tubular body 1 0, the return spring 26 is compressed, and the hot-plate 20 is gripped and retained by the bimetallic pincer 34 against the action of a resilient force F (see Figure 2) developed by spring 26. This resilient force F is transmitted through the bolt 32 to the metallic washer 44 and thence to the insulating washer 42, which applies an axial pressure to the fusible annular body 40 tending to compress the said body 40.When the heating element in the hotplate 20 becomes red hot through the effect of the current passing through it, the heat derived thereby produces (in normal operation) a retraction of the bimetallic pincer 34, at which the return spring 26 causes the hot-plate and the button 1 8 to be released in the direction of the arrow F to a 'ready' position in which the annular cap 28 is halted against the tongues 14C and the button 1 8 projects axially from the knob 1 6, as shown in the broken line 18'. In this instance, the fusible body 40 does not undergo modification through the effect of the temperature reached in hot-plate 20.

In the case of faulty operation, however, that is, when the hot-plate 20 is not released from the bimetallic pincer 34 because of jamming, the heat from the hot-plate 20 at first produces softening and thence melting of the fusible body 40 whilst the latter is being compressed by the spring 26.

When the thermoplasticity of the body 40 is no longer capable of withstanding the force F of spring 26, the bolt 32 begins to move to the right, in Figure 1, under the traction effect which spring 26 exercises on the bimetallic gripper 34 through the hot-plate 20. This causes the insulating washer 42 to produce, by compression, a flow of metallic material from the body 40 which is directed radially towards the bolt until there is physical contact with the bolt by this flow at the same time the material of the body 40 is always in contact with the cap 36 which surrounds it.

This results in a short circuit which causes the fuse 46 to blow.

For additional safety, the metallic washer 44 may have a radial tab 44B which forms, in an axial direction, a small gap 50 in relation to the edge of the metallic cap 36, the width of the gap 50 being less than the thickness of the fusible body 40. If, in spite of the compression by the insulating washer 42, the flow of softened or molten metallic material from the body 40 does not reach the bolt 32 to produce the short-circuit, as described above, then, at a certain moment, the tab 44B touches the edge of the cap 36 thereby giving rise to a short-circuit between these two parts which by-passes the fusible body 40 and produces, on its own account, the blowing of the fuse 46.

In the variant shown in Figure 2 the parts corresponding to those already described above are shown with the same reference numerals. In this variant the cap 36, of Figure 1, is replaced by a flat washer 52 with a tab 52' for electrical connection, and the fusible body 40 is in permanent electrical contact with the end wall 10A through the washer 52. In addition, a metallic cap 54 is interposed between the metallic washer 44 and the insulating washer 42.

The cylindrical skirt of this cap 54 surrounds, with small radial play, the insulating washer 42 and the fusible body 40. The free edge of this cap in relation to the metallic washer 52 forms a gap 50', equivalent to that shown in Figure 1, in such a way that in the final phase of the axial compression of the fusible body 40 the said edge may establish, with the washer 52, the emergency short-circuit contact already described above. Moreover, between the tightening nut 32B and the metallic washer 44 there is interposed a sheet metal spring 56 which, when the nut is tightened, applies a resilient compressional force to the fusible body 40 through the washer 44 and the cap 54, indpendently of the force F which is applied to the bolt 32 by the helical return spring 26 (Figure 1).This structure takes account of the possibility that the force F of the return spring 26 may be absent as a result, for example, of a breakage or overheating of the spring; or as in a particular design of cigarette lighter, the force of the return spring normally provided may be insufficient for the purposes of the present invention. In the structure shown in Figure 2, the sheet metal spring 56 acts continuously, so that if, intentionally or accidentally, the bolt 32 should not have any freedom of axial displacement in the central hole of the insulating support 30, the metallic washer 44, the cap 54 and the insulating washer 42 can slide along the bolt 32 under the force of the spring 56 to produce the compression of the fusible body 40 when the latter is sufficiently softened or molten.

It will be understood that the invention is not limited to the sole embodiments given above, by way of example; numerous modifications being easily conceived without departing from the spirit of the claims which follow.

Claims

1. An electric cigarette lighter for motor vehicles, comprising a tubular metal body housing a removable cigarette lighter plug, the body being connectible to one pole of an electrical supply and having an aperture in an end wall, a contact unit connectible to the other pole of the electrical supply, said unit having a spring in the form of a bimetallic element for making and breaking an electrical contact, the spring being supported by a conductive part such as a bolt traversing said aperture axially, a support of electrically insulating and substantially refractory material fixed to the said end wall and axially traversed by said part, said bimetallic element being supported by the said wall without electrical contact with the latter, and an electrically conducting, fusible, annular body arranged externally in relation to the end wall of the metal tubular body of the lighter, the lighter having resilient means which apply a pressure to the fusible annular body at least in the heating position of the lighter plug, said pressure being adapted in such manner as to effect compression of said fusible annular body only when the latter is softened through the heat produced by the lighter plug.

2. A lighter according to claim 1, in which the said resilient means comprise the return spring of the lighter plug.

3. A lighter according to claim 1 or claim 2, in which said resilient means comprise a compression spring acting between the fusible annular body and the external end of said part in the contact unit.

4. A lighter according to any of the preceding claims, in which a recess housing the fusible annular body is formed by a metal cap which is in permanent electrical contact with the end wall or said part.

5. A lighter according to any of the preceding claims, comprising an emergency non-fusible contact member which is in permanent electrical contact with said part and is arranged in such a way as to short circuit the part with the end wall in a final phase of the compression of the fusible annular body.

6. A lighter substantially as herein described and as illustrated in Figure 1 or Figure 2 of the accompanying drawings.