HEATING ROD WITH SLOTTED CONTACT SHEET

Abstract

Disclosed is a heating rod comprising a ceramic heating element, a strip shaped contact sheet electrically contacting the heating element, and a housing in which the contact sheet and the ceramic heating element are arranged. The contact sheet is provided with slits originating from a longitudinal edge of the contact sheet.

Claims

1. A heating rod, comprising: a ceramic heating element; a strip-shaped contact sheet electrically contacting the heating element; and a housing in which the contact sheet and the ceramic heating element are arranged; wherein the contact sheet has slits originating from a first longitudinal edge of the contact sheet.

2. The heating rod according to claim 1, further comprising additional slits that originate from a second longitudinal edge of the contact sheet.

3. The heating rod according to claim 2, wherein the slits and the additional slits originate alternately from the first longitudinal edge and the second longitudinal edge of the contact sheet.

4. The heating rod according to claim 2, wherein one the slits and one of the additional slits are arranged between a first section of the contact sheet covering a first one of the heating elements and a second section of the contact sheet covering a second heating element neighboring the first heating element.

5. The heating rod according to claim 1, wherein the slits narrow from their origin to their end.

6. The heating rod according to claim 1, wherein the contact sheet covers a plurality of ceramic heating elements, wherein one of the slits is disposed between a first section of the contact sheet that covers a first heating element and a second section of the contact sheet that covers a second heating element.

7. The heating rod according to claim 1, wherein the slits each extend over at least two thirds of the width of the contact sheet.

8. The heating rod according to claim 7, wherein the slits extend over at least over three quarters of the width of the contact sheet.

9. The heating rod according to claim 1, wherein the slits each extend at most over nine tenths of the width of the contact sheet.

10. The heating rod according to claim 1, wherein the contact sheet is made of copper.

11. The heating rod according to claim 1, wherein the contact sheet is nickel-plated.

12. The heating rod according to claim 1, comprising a second contact sheet provided with slits, wherein the ceramic heating element is arranged between the contact sheets and is electrically contacted by both.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0016] FIG. 1 shows schematically an embodiment of a heating rod in an exploded view; and

[0017] FIG. 2 shows an embodiment of a slotted contact sheet of a heating rod.

DESCRIPTION

[0018] The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

[0019] The heating rod shown in the attached FIG. 1 comprises several ceramic heating elements 1 although the heating rod might also be configured with only a single ceramic heating element 1. The ceramic heating elements 1 are resistive heating elements which may be PTC heating elements, for example on the basis of barium titanate.

[0020] The heating elements 1 are held in a plastic frame 2 and electrically contacted by a first strip-shaped contact sheet 3 as well as by a second strip-shaped contact sheet 3. As can be seen in the figure, the heating elements 1 are arranged between the strip-shaped contact sheets 3. The contact sheets are electrically isolated from the housing 6 by insulations layers 4a, 4b, e.g. a ceramic plate 4a and a polymer film 4b.

[0021] The ceramic heating elements 1, the plastic frame 2, and the contact sheets 3 are arranged in a housing. The housing is a metal tube formed by a first and a second housing part 6. The first and the second housing part 6 are profiles which have an open cross section, e.g. a U-shaped cross section. The open cross section of each profile is closed by the other profile when the heating rod is assembled. The housing 6 might also be provided as a single piece.

[0022] The heating rod shown schematically in FIG. 1 comprises two contact sheet 3 contacting the heating elements 1. Instead of a second contact sheet 3, the heating elements 1 might also be connected to ground by the housing 6.

[0023] FIG. 2 shows the contact sheet 3 of the heating rod shown in FIG. 1. The strip-shaped contact sheet 3 is provided with slits 5, which may also be called cuts or notches. As can be seen in FIG. 2, the slits 5 go from a front surface of the contact sheet 3 all the way through to its back side. The slits 5 originate from a longitudinal edge of the contact sheet 3 and run traverse to the longitudinal direction of the contact sheet 3. The slits 5 can be oriented perpendicular to the longitudinal direction of the contact sheet 3 or be slanted.

[0024] The slits 5 alleviate thermal stresses caused by differences in thermal expansion of the various parts of the heating rod. The slits 5 allow the contact sheet 3 to easily extend or contract in its longitudinal direction thereby alleviating stresses caused by thermal extension.

[0025] The slits 5 originate alternatingly from opposite longitudinal edges of the contact sheet 5. For example, a pair of slits 5 originating from opposite longitudinal edges of the contact sheet 3 are arranged between a section of the contact sheet contacting one of the heating elements 2 and another section of the contact sheet 3 contacting a neighboring heating element 2.

[0026] Each slit 5 should extend over at least two thirds of the width of the contact sheet 3, for example over at least over three quarters of the width of the contact sheet 3. In the embodiment shown, each slit 5 extends over at least four fifths of the width of the contact sheet 5, although shorter slits 5 may suffice.

[0027] The slits 5 should not be too long as that would increase the electrical resistance of the contact sheet 3. In the embodiment shown, the slits 5 each extend over less than nine tenths of the width of the contact sheet 3. The slits 5 may be cuts of a constant width. In the embodiment shown, the width of the slits 5 decreases from their origin to their end.

[0028] The contact sheet 3 may be made of any metal, e.g. aluminum or copper. In the embodiment shown, the contact sheet 3 is made of copper. The contact sheet 3 may bear a coating to protect it from corrosion and to improve contact, e.g. a tin coating or a nickel coating. In the embodiment shown, the contact sheet 3 is nickel plated.

[0029] While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

LIST OF REFERENCE SIGNS

[0030] 1 housing [0031] 2 heating element [0032] 3 contact sheet [0033] 4 isolation layer [0034] 5 slit