GB2052224A - Electrical window heater - Google Patents

Abstract

A heater for attachment to the interior of the rear window of a vehicle comprises a flexible backing sheet 11 carrying a plurality of heater elements 12 adhesively secured to a first face of the backing sleet 11 and having an adhesive coating on the outwardly presented faces thereof, whereby in use the elements 12 can be secured to a window, and spacer means 15 in the form of compressable, foamed synthetic resin strips projecting from the first face of the backing sheet 11 to a height in excess of the height of the adhesive coating on the elements 12 so that the backing sheet 11 together with the elements 12 and the spacer strips 15 can be rolled lengthwise to form a scroll wherein the undersurface of one convolution of the backing sheet 11 overlies the adhesive coating on the elements 12 of the next adjacent convolution of the backing sheet 11, but is held out of contact with the adhesive coating on the elements 12 by the strips 15. <IMAGE>

Description

SPECIFICATION Furry heater This invention relates to heaters, particularly but not exclusively heaters intended to be fitted by a vehicle owner to the interior of the rear window of a vehicle.

In a known form of heater for attachment to a vehicle rear window a plurality of heater elements in the form of thin metal strip are provided on one face with an adhesive whereby the elements can be attached to the window. The elements are supported in a predetermined space relationship by a backing sheet to which they are adhesively secured. The backing sheet is conventionally of paper, and the adhesive connection between the elements and the backing sheet is such that after the elements have been applied to the window, and have adhered thereto by virtue of the adhesive on the elements, the backing sheet can be peeled away from the elements leaving the elements attached to the window.It has previously been proposed to protect the adhesive surface of the elements by means of a cover sheet which overlies the protective surface of the elements and which is peeled from the adhesive surface of the elements prior to offering the elements to the window. In a known form of such a heater the cover sheet is a separate entity from the backing sheet, but in our co-pending British Patent Application number 19659/78 Serial No.

1 581207 we have proposed that the covering sheet is defined by the undersurface of the backing sheet, the backing sheet together with the elements carried thereon being rolled to form a scroll wherein the undersurface of the backing sheet of one convolution of the scroll constitutes the cover sheet for the elements on the next adjacent convolution of the scroll.

The arrangement proposed in our co-pending application 19659/79 Serial No.1581207 is satisfactory for many applications, but it is found that in certain circumstances the arrangement is disadvantageous in that dust, or similar detritus likely adhering to the underside of the backing sheet, for example because of the charge of static electricity on the sheet, can become transferred to the adhesive carried by the elements to the detriment of this adhesive. Furthermore, the adhesive on the elements lightly adheres to the undersurface of the backing sheet, and although the adhesion is relatively slight, by virtue of siliconising of the undersurface of the sheet, the action of peeling the undersurface of the backing sheet away from the adhesive on the elements can reduce the subsequent adhesive efficiency of the adhesive on the elements.It is an object of the present invention to provide a heater wherein these disadvantages are minimised.

A heater according to the invention includes a flexible backing sheet, at least one heater element adhesively secured to a first face of the backing sheet and having an adhesive coating on the outwardly presented face thereof, whereby in use the element can be secured to a window, and, spacer means projecting from said first face of the backing sheet to a height in excess of the height of the adhesive coating on the element whereby, in use, the backing sheet together with the element can be rolled along its length to form a scroll wherein the second, undersurface of one convolution of the backing sheet overlies the adhesive surface of the element of the next adjacent convolution of the backing sheet but is held out of contact with the adhesive surface of the element by said spacer means.

Preferably the backing sheet carries a plurality of elements arranged in a predetermined pattern.

Conveniently the spacer means comprises one or more strip of flexible material secured to the first face of the backing sheet and extending parallel to the heater element or elements.

Desirably said spacer strip or strips are formed from foamed rubber or the like.

Conveniently the backing sheet carries nine equidistantly spaced parallel heater elements and spacing means is arranged along the length of the elements between the first and second elements and the eighth and ninth elements.

One example of the present invention is illustrated in the accompanying drawings wherein Figure 1 is a diagrammatic plan view of part of a heater, Figure 2 is an enlarged sectional view on the line 2-2 in Figure 1, Figure 3 is a diagrammatic side elevational view of the heater component shown in Figure 1 rolled, and Figure 4 is a diagrammatic cross sectional view of part of the rolled component shown in Figure 3.

Referring to the drawings, the heater, for application to a vehicle rear window, comprises a paper backing sheet 11 approximately 60 inches in length, and having arranged thereon nine heater elements 12, the elements 12 being equidistantly spaced from one another and extending parallel to one another along the length of the backing sheet 11. Each element 12 is conveniently formed from nichrome tape. Each of the elements 12 is secured to the first face of the backing sheet 11 by means of a line of adhesive so that the first surface of the backing sheet 11 between the elements 12 is free of adhesive.On its outwardly presented face each of the elements 12 carries a coating of a strong adhesive, conveniently a time/temperature crosslinking adhesive for example that made by National Adhesives Limited of England under their code number A80-1 008 or 130-1219. In Figure 2 the adhesive securing the elements 12 to the backing sheet 11 is indicated at 13, and the adhesive coating the outer face of the elements 1 2 is indicated at 14. Also secured to the first face of the backing sheet 11 are three elongate strips 1 5 of flexible, foamed synthetic rubber or synthetic resin material. The strips 1 5 extend parallel to the elements 12, and are positioned respectively between the first and second elements, the fifth and sixth elements, and the eighth and ninth elements.The strips 1 5 are secured by respective lines of adhesive 1 6 to the sheet 11. The strips 1 5 are compressible owing to their foamed construction, but in their rest state have a height above the surface of the sheet 11 which is considerably in excess of the height of the surface of the adhesive coating 14 of each of the elements 12 above the surface of the sheet 11.

The heater will be supplied to the fitter in kit form, the kit including the component illustrated in Figure 1 and described above. Since the backing sheet is intended to be in the region of 60 inches in length then in order to avoid the need for a packaging box of equivalent length it is intended that the backing sheet 12 should be rolled along its length to produce a scroll formation of the kind shown in Figure 3. The provision of the strips 1 5 ensure that in the rolled form the adhesive 14 on the elements 12 is maintained spaced from the undersurface of the backing sheet 11.It will be recognised that without the strips 1 5 then during the rolling of the backing sheet 11 along its length the undersurface of one convolution of the backing sheet 11 would contact and adhered to the adhesive 14 on the elements 12 of the next adjacent convolution. However, such contact is prevented by the strips 15 which act as spacers.

While the arrangement has been described as having three spacer strips 1 5 the exact number of spacer strips will depend upon the width of the backing sheet 11, and its inherent strength. For example, when rolled to cylindrical form it may be found that the centre one of the three strips described can be dispensed with, or alternatively in a wide arrangement it may be found that an additional strip 1 5 would be useful.

The fitter receiving his kit with the backing sheet 11 in rolled form first applies a connector arrangement provided in the kit to the opposite edges of the previous cleaned surface of the window. The connector arrangement includes a synthetic resin channel member for adhesive attachment to each side of the window, together with a metallic bus-bar capable of being received as a snap fit in each channel. After fitting the channel parts of the connector arrangements to both sides of the window the fitter unrolls the backing sheet 11 and presents the central region of the backing sheet 11 to the central region of the window with the elements 12 extending generally horizontally, with their adhesive coatings 14 presented to the window surface.The fitter then progressively applies force to the backing sheet to urge it towards the window thus causing the strip or strips 15 to collapse and allowing the strong adhesive 14 to engage and adhered to the clean window surface. This operation is performed starting from the centre of the sheet progressively along the length of the sheet until the elements 12 are adhered to the window along their length. The end regions of the elenents 12 will overlap the channels of the connector arrangements, and the fitter will next trim the end regions of the elements 12 and the backing sheet. The fitter will then carefully peel the backing sheet away from the elements 12, preferably starting from the central region of the backing sheet, leaving the elements 12 adhering to the window.Lastly, the fitter will snap the bus-bars into the two channels and in so doing will deform the end regions of the elements 1 2 into the channel so that a good electrical connection is achieved between each of the elements 12 and the two bus-bars, the two busbars thus connecting the elements 12 electrically in parallel. If a switched electrical supply is already provided to the appropriate location in the vehicle the fitter will make a power connection to one of the bus-bars and an earth connection to the other bus-bar, but obviously in the event that there is no such power supply then the fitter will need to provide one and since most vehicles are not equipped with such power supply the kit will conveniently include a switch with a warning light, appropriate electrical connectors, and a sufficient length of electrical lead.

It will be recognised that since, in the rolled form, the adhesive coatings 14 are held clear of contact with the undersurface of the backing sheet then any dust or similar detritus clinging to the backing sheet will not be transferred to the adhesive coating 14, and the first surface to which the adhesive coatings 14 will adhere will be the window, and not the undersurface of the backing sheet.

While the use of spacer strips 1 5 is described above in relation to a kit form heater which is assembled onto the window, it is to be understood that the same principle can be applied to preformed heaters carried similarly on a backing sheet. Such heaters are usually known as "fixed width" heaters and comprise heater strips already interconnected by bus bars to form the heater, the strips and bus bars being transferred to the window as described above in relation to the elements 12.

Claims (1)

1. CLAIM

   A heater including flexible backing sheet, at least one heater element adhesively secured to a first face of the backing sheet and having an adhesive coating on the outwardly presented face thereof, whereby, in use, the element can be secured to a window, and, spacer means projecting from said first face of the backing sheet to a height in excess of the height of the adhesive coating on the element whereby, in use, the backing sheet together with the element can be rolled along its length to form a scroll wherein the second, undersurface of one convolution of the backing sheet overlies the adhesive surface of the element of the next adjacent convolution of the backing sheet but is held out of contact with the adhesive surface of the element by said spacer means.