US 3427712 A
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Description (OCR text may contain errors)
1969 A. N. R. Wl TDOECKT 3,427,712
METHOD OF MAKING AN ELECTRICAL RESISTOR Filed June 25, 1964 Mam m? 41 6527 A4 W/mascxr United States Patent METHOD OF MAKING AN ELECTRICAL RESISTOR Albert Norbert Robert Witdoeckt, 9a Witte Nonnenstraat,
Oostende, Belgium Filed June 25, 1964, Ser. No. 377,809 Claims priority, application Belgium, July 9, 1963,
634,716; May 6, 1964, 647,596
US. Cl. 29-611 3 Claims Int. Cl. H01c 7/04, 3/00 ABSTRACT OF THE DISCLOSURE Electrical resistors are made by applying to an insulating backing a thin aluminum sheet having a thickness less than 0.010 mm., and then cutting the aluminum sheet but not its insulating backing by means of knives that rotate about axes perpendicular to the line of cut, thereby to form in the aluminum sheet a multiplicity of cuts that extend in from alternately opposite edges of the sheet and that provide a greatly elongated zigzag path of electrical resistance.
The present invention relates to an electrical resistor in particular for use as heating element, constituted of a rolled, conductive metallic sheet adhering by one of its faces to an insulating support or a support covered with insulating material, having gaps extending so as to form an electrical circuit at the ends of which are disposed connecting terminals.
In known electrical resistors of this type, the conductive sheet is a copper sheet of minimum thickness 0.025 mm., having a single gap extending spirally or with some similar broken outline from its central part to its marginal part.
In order to be able to facilitate manufacture of the resistor and to reduce its cost price, use is made in the invention of an aluminum sheet less than 0.010 mm. thick.
In an embodiment of the invention the new resistor has gaps which are parallel to each other and which extend alternatingly from. one edge of the conductive sheet to the vicinity of the opposite edge of the sheet, and from thereto the vicinity of the first-mentioned edge, this arrangement of the gaps being simple, quick and economical to carry out.
The invention further concerns a process for manufacturing the new resistor, in accordance with which a conductive sheet of rolled metal, constituting the resistor, is caused to adhere to an insulating support or a support covered with insulating material, whereupon gaps are made in the conductive sheet so as to form an electrical circuit therein, and finally, terminals are attached to the ends of the circuit thus constituted.
In accordance with an important feature of the said process, a continuous strip of rolled metal, constituting the resistor, is caused to adhere to an insulating strip or strip covered with insulating material, this strip being continuous and flexible and constituting the support. Thereupon the above-mentioned gaps are made in the sheet, to produce electrical circuits; the strips connected to each are cut, so as to separate the circuits and the above-mentioned terminals are attached to each of them. This feature makes it possible to manufacture the resistor from a roll of the metallic strip and a roll of the insulating strip, to stick the unwound strips together, to mark out continuously the gaps required, to wind up the resistors thus obtained and to cut them off as need arises, the connecting terminals then being attached, whereupon they are ready for use.
3,427,712 Patented Feb. 18, 1969 However, in accordance with another embodiment of the invention, it is also possible to manufacture the new resistor by causing a conductive sheet of rolled metal, constituting the resistor, to adhere to an insulating support or a support which is covered with insulating material and which may for example be rigid, having dimensions generally speaking greater than those of the conductive sheet, whereupon the above-mentioned gaps are made and the connecting terminals are attached.
The making or marking of the parallel gaps extending alternately from one edge of the conductive sheet to the vicinity of the opposite edge of the sheet, and from there to the vicinity of the first-mentioned edge, is obviously a simple and practicable matter, and can be carried out by one related movement of the working tools and the conductive sheet. It is possible to make gaps going from one edge to the other of the conductive sheet, and, by reversing the tools or the conductive sheet, to make the return gaps.
The gaps are made in accordance with the invention by mechanically taking out material from the conductive sheet.
The invention will now be described with the aid of the attached drawing, which show diagrammatically and by way of example only two embodiments of the present invention.
FIGURE 1 is a perspective view of an embodiment of the resistor of the invention.
FIGURE 2 is a diagram illustrating a process for making the resistor of the invention.
FIGURE 3 is a diagram illustrating a second embodiment of the resistor of the invention.
In the various figures like numbers are used to designate like parts.
The resistor of the invention is constituted of a conductive sheet 1, of thin, rolled aluminum sheet less than 0.010 mm. thick in particular, of thicknesses between 0.003 mm. and 0.010 mm.
The conductive sheet 1 adhers by one of its faces to an insulating support 2 or a support covered with insulating material. The dimensions, that is to say the length and width, of the support are restricted and are generally greater than those of the conductive sheet 1.
The insulating support sheet 2 can be flexible or rigid, and is somewhat thick, in relation to the conductive sheet 1. The support sheet can be constituted of a sheet of paper, cardboard, synthetic material, tissue, or it may be a plate consisting of plaster, compressed asbestos cement, glass, mica; further it may be a metallic plate covered with insulating material, such as vitrified enamel, or a concrete plate covered with insulating material, the above list of examples not being intended to be restrictive.
The conductive sheet 1 has parallel gaps, as for example the longitudinal gaps 3 and 4 which define an electrical circuit, formed in the example chosen of a conductor in the form of a strip folded in zag-zag. Electrical terminals 5 are attached atthe ends of the circuit for the supply of current. It should be understood that the longitudinal gaps 3 and 4 can be replaced by similar transverse gaps.
The gaps 3 extend from a transverse edge 6 of the conductive sheet 1 to the vicinity of the opposite transverse edge 7 of the said sheet in such a way that they do not reach the edge 7 and are spaced therefrom by the distance marked a in the drawings.
The gaps 4 extend between the gaps 3, from the edge 7 to the vicinity of the edge 6, without however actually reaching this, and are spaced from the edge 6 by the distance marked b in the drawings, generally speaking equal to the distance a.
1 The gaps '3 and 4 extend side by side fora-length marked 0, found between a and b.
To manufacture the electrical resistor described above, the conductive sheet 1 is caused to adhere, for example by glueing, to the support 2, whereupon, by cutting, gaps 3 and 4 are made simultaneously or successively in the sheet 1 and connecting terminals 5 are attached to the sheet 1.
To cut out simultaneously the gaps 3 and 4, rotary knives are applied at the length 12 against the conductive sheet 1 at the localities of the gaps 3. Thereupon, along the length c, the knives are continously applied against the sheet 1 at the localities of the gaps 3, whereas or other knives are applied against the sheet 1 at the localities of the gaps 4. Finally, at the length a the knives cutting the gaps 3 cease to be applied against the sheet 1, whereas the other knixes concerned with the gaps 4 are applied right up to the edge 7. Accordingly, the gaps 3 and 4 are cut in one movement of the said working tools,
from the edge 6 of sheet 1 to the edge 7 of the said sheet.
To cut the gaps 3 and 4 simultaneously, accordingly two sets of working tools can be used. The set of tools concerned with the gaps 3 are moved from the edge 6 toward the edge 7, applying against the sheet 1 on the paths b and 0, whereas at the same time the set of tools concerned with the gaps 4 are moved from the edge 7 towards the edge 6, applying against the sheet 1 on the paths a and c.
To cut the gaps 3 and 4 alternately, use is preferably made of sets of rotary knives, which are applied along the length b and 0 against the conductive sheet 1, but are removed from contact with this at the length a. Thereupon the knives are lifted off, perpendicular to the gaps, i.e., following the arrow X, to be reapplied at a distance equal to the spacing of the gaps 3 and 4. The knives are then applied along the lengths a and c against the conductive sheet 1, and are removed from contact with this at the length b. Accordingly, the gaps 3 are cut by one movement of the cutting tools from the edge 6 toward the edge 7, whereupon the gaps 4 are cut by the reverse or return movement of these cutting tools.
In the processes described above it is the knives which are moved, but the invention is also concerned with the case in which the knives remain stationary and act on the conductive sheet which moves.
When a flexible continuous strip is used as conductive sheet and as insulating support, it is preferable to manufacture the resistors of the invention from a roll of the conductive strip and a roll of the insulating strip, said rolls are unwound and stuck together, the gaps being made simultaneously as described above, to make the successive electrical circuits. The strips with the marked gaps can be wound up and subsequently cut in accordance =with"the'-said circuitsflto obtain individual resistors to which are attached the connecting terminals.
It is obvious that the invention is not exclusively restricted to the two embodiments shown, and that numerous modifications can be made in the shape, thearrangement and the construction of some of the elements used in the carrying out of these embodiments, provided that these modifications do not contradict the aim of any of the following claims.
What I claim is:
1. A process for manufacturing an electrical resistor, comprising feeding an aluminum sheet having a thickness less than 0.010 mm. onto an insulating support and adhering said sheet to said support, cutting through said aluminum sheet but not through said insulating support by means of rotating knives to form parallel gaps extending alternately from opposite edges of the aluminum sheet by causing movement of said support and the axes of said knives relative to eachother in a direction parallel to the length of said gaps, and adding electrical terminals to the ends of the resistor constituted by the cut aluminum sheet. 1
2. A process as claimed in claim 1, and thereafter imparting to said knives and said insulating support relative movement in a direction transverse to the length of said gaps to position said sheet and said knives relative to each other for the formation of further said gaps.
3. A process as claimed in either of claims 1 and 2, in which said cutting is performed by use of two series of rotating knives with one said series cutting the said gaps that open through one said edge of the sheet and the other said series forming the gaps that open through i the other said edge of the sheet.
References Cited UNITED STATES PATENTS 2,680,184 6/1954 Cox 219-383 x 2,719,213 9/1955 Johnson 338212 3,149,406 9/1964 Eisler 29-155.5 3,172,074 3/1965 Drewes et a1. 338-308 2,622,178 12/1952 Glynn 29-620 X 3,031,745 5/ 1962 Dzialo. 3,119,919 1/1964 Pratt. 3,162,076 12/ 1964 Emerson et a1 83--678 X FOREIGN PATENTS 584,588 10/1959 Canada.
JOHN F. CAMPBELL, Primary Examiner.
J. L. CLINE, Assistant Examiner.
US. Cl. X.R.