US2933589A - Electrical resistors - Google Patents
Electrical resistors Download PDFInfo
- Publication number
- US2933589A US2933589A US505758A US50575855A US2933589A US 2933589 A US2933589 A US 2933589A US 505758 A US505758 A US 505758A US 50575855 A US50575855 A US 50575855A US 2933589 A US2933589 A US 2933589A
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- United States
- Prior art keywords
- cap
- recess
- tail
- end cap
- head
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C1/00—Details
- H01C1/14—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors
- H01C1/148—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors the terminals embracing or surrounding the resistive element
Definitions
- the invention is particularly, concerned with precision resistors for use in electronic aircraft and radio apparatus of the kind comprising a ceramic or other electrically non-conducting cylindrical core with a conductingfilm thereon, for example a metal or carbon film, theelectrical connections to this film being made through the medium of metal end caps furnished with wire leads or tails and provided on the ends of the non-conducting core.
- An accepted method of making resistors of the aforementioned kind comprises placing the film-provided comes into an automatic machine which feeds them forwardly one after another into a cutting machine which, cuts through the film in a spiral path of predetermined form and pitch to give the required resistance.
- metal end caps of cup-like nature are fitted one on each end of the element, the end cap having an integral tail or having a tail soldered or welded thereto prior to the end cap being placed on the resistor.
- a method of manufacturing electrical resistors of the type having wire tails comprising taking an element of rod form; fitting to each end of the said element a metal end cap having in its end surface an inward recess; forming, between the two end caps, an electrical connection of the desired resistance; applying a head formed on the wire tail to the recess in one of said end caps so as to position said tail with respect to said end cap; and then welding the head of said tail into the recess in the end cap.
- a method of manufacturing electrical resistors comprising taking an element of rod form furnished with a conducting film; fitting to each end of the said element a metal end cap having in its end surface an inward recess; cutting the film of the element to provide the desired resistive path; forming tails with a head at one end to be connected to the end cap; engaging the head of one of said tails in the recess in the end cap to which such tail is to be attached so as to posiof the resistor.
- the tail with respect to the end cap; and then welding the tail to such end cap with the head of the tail pressed against the base of the recess in the end cap, which latter is supported on the opposite side by the core
- the said recess in each of the end caps is ofa part-spherical form and the head of the tail is of a corresponding shape so as to be capable of making a close fit with the recess over a substantial area to ensure adequate metallic and electrical contact between the tail and the end cap.
- the radius of curvature of the said part-spherical recess in the end cap is preferably approximately the same as the radius of curvature of the part-spherical head of the tail, although it may, in some cases, be desirable to producethese parts with initially slightly different radii of curvature.
- the recess in the end cap will preferably be centrally located and it will be understood that in any case the inner surface of the end cap (at the base of the said recess) will bear upon the adjacent end of the core of the resistor and give a firm support for the end cap whilst the tail is being secured thereto.
- This firm support of the cap permits a reliable weld to be made without the usual arrangement of a welding electrode on the inside of the cap which is precluded when the tail is being welded to the cap after the fitting of the latter to the resistance core. If no recess were provided and even were the end cap pressed fully home, the end cap would be slightly resilient and would preclude the obtaining of a reliable electrical connection between the end cap and the tail prior to welding; the Weld might therefore be defective.
- the welding takes place in a fraction of a second and generates heat only locally and causes no disturbance to the resistance element.
- drawing shows a generally cylindrical core 1 made such as of metal or porcelain and having a thin film 2 of carbon deposited on the peripheral surface thereof.
- An end cap 3 formed as a brass pressing with a wall thickness of about .011" has been applied to the end of the core'linsuch a manner as to be in electrical contact with the car-. bon film 2.
- the end cap 3 is provided with a substantially central recess 4, the inner surface of which bears on the end face 5 of the core 1.
- a tail 6 formed of S.W.G. copper wire is shown coaxially aligned with the recess 4, this tail having a substantial head 7 formed thereon by an upsetting operation such as that employed in the formation of heads on pins and other similar metallic objects.
- the radii of curvature of the recess 4 and head 7 are substantially the same.
- An annular electrode 8 is coaxially engaged with the outer end surface of the cap 3 and a further electrode (not shown) is engaged with the tail 6, the head 7 of the tail being located within (but out of contact with) the annular electrode 8.
- a further electrode (not shown) is engaged with the tail 6, the head 7 of the tail being located within (but out of contact with) the annular electrode 8.
- the recess 4 in the end cap 3 provides means for adequately positioning the tail 6 with respect to the end cap whilst the securement of these two parts co-axially together is being eifected and, by forming a substantial head 7 on the tail, an adequate electrical contact over a substantial area is provided between the cap and the tail and the danger of forming an imperfect or high-resistance joint is greatly reduced.
- annular electrode 8 above described may be replaced by clamping the second electrical lead to the outside periphery of the end cap 3.
- end caps can be secured to the cores prior to the cutting of the films of the latter so that this cutting operation can be effected to a very close tolerance and that the tails can subsequently satisfactorily be attached without affecting the resistance of the resistor.
- Such resistance element may, for example, be resistance wire or metalised glass fibre and may be Wound spirally upon the rod.
- the rod may, for example, be made of arceramic material such as porcelain or it may alternatively be made of sintcred alumina, e.g. that sold under the registered trademark Sintox.
- a method of welding an electrical lead to a metallic end cap for an insulating core carrying an electric resistive element which comprises the steps of forming an exterior recess on the end of said cap, fitting an end of said core within said cap until it abuts the inner wall surface of said recess, forming a protruding head on said electrical lead adapted to engage said recess, electrically connecting one of the electrodes of a welding apparatus to said lead, electrically connecting another electrode of said apparatus to a portion of the outer surface of said cap spaced from said recess, and then pressing said head into said recess bearing against said core to electrically weld said lead to said cap.
- a method of welding an electric lead to a metallic end cap including positioning said electrically connected lead in axial alignment with the recess in said cap, electrically connecting said other electrode to the periphery of said cap in spaced parallel relationship to said axially positioned lead and then moving said lead toward said cap, pressing said head into said core-bearing recess to undeformingly spot-weld said head therein.
- a method of welding an electric lead to a metallic end cap for an insulating core carrying an electric resistive element which comprises the steps of forming a centrally positioned concave recess on the end of said cap, fitting said cap onto said core with the raised inner wall of said recess in abutting engagement with said core, forming a convex head on said electric lead complementary to said concave end, electrically connecting an electrode of a welding apparatus to said lead, electrically connecting another electrode of said apparatus to a portion of the outer surface of said cap spaced from said recess, and then pressing said convex head within said core-supported concave recess to undeformingly spot-weld said lead to said cap.
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- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Details Of Resistors (AREA)
- Apparatuses And Processes For Manufacturing Resistors (AREA)
Description
April 19, 1960 G. PEARCE 2,933,599
ELECTRICAL RESISTORS Filed May 3, 1955 E Invepnlor A Home y United States Patent 2,933,589 ELECTRICAL RESISTORS Graham Pearce, Crick, near Rugby, England,
to Painton and Company Limited, Northampton, England, a British company Application May 3, 1955, Serial No. 505,758 7 Claims priority, application Great Britain May 3, 1954 4 Claims. (Cl. 219-107 This invention concerns improvements in or relating to rod-type electrical elements having end caps and electrical connection leads or tails, and more particularly relates to electrical resistors of rod form having a metal end cap and a lead wire or tail connected to such cap to provide for the necessary electrical connections when the element is in use. 7 When the term rod-type is used it should be understood that usually an element of cylindrical form is referred to, but that cases may arise where other crosssectional forms are of interest and it should be understood that this invention is applicable thereto and need not be limited to elements of circular cross-sectional form.
-The invention is particularly, concerned with precision resistors for use in electronic aircraft and radio apparatus of the kind comprising a ceramic or other electrically non-conducting cylindrical core with a conductingfilm thereon, for example a metal or carbon film, theelectrical connections to this film being made through the medium of metal end caps furnished with wire leads or tails and provided on the ends of the non-conducting core.
An accepted method of making resistors of the aforementioned kind comprises placing the film-provided comes into an automatic machine which feeds them forwardly one after another into a cutting machine which, cuts through the film in a spiral path of predetermined form and pitch to give the required resistance. After the film has been cut in this way to give the required resistance, metal end caps of cup-like nature are fitted one on each end of the element, the end cap having an integral tail or having a tail soldered or welded thereto prior to the end cap being placed on the resistor.
In practice it is found that the resistance value of the element after capping is in many cases different from the value when held in the spiralling machine and this makes it almost impossible to produce close tolerance resistors (within 1% of nominal resistance) by this method. Although it is usual to apply a layer of material of low electrical resistance at the ends of the resistance element before it is placed in the automatic spiralling machine, this does not completely avoid the change of resistance referred to.
In prior attempts to cut the film of the resistor after the end caps have been applied and before the tails are attached to these end caps, applicant has experienced great ditficulty in subsequently attaching the tails to the end caps in such manner as to give a mechanically and electrically sound joint without damaging the resistor or changing its resistance value. The heating involved in attaching the lead by means of high temperature solder (300 C. melting point or higher) is liable to change the resistance value and also loosen the grip of the cap on the core, and the use of such solder also leaves troublesome flux residues. On the other hand, the automatic machines available cannot handle the cutting of the films on resistors after end caps fitted with tails have been applied thereto.
It is therefore an object of this invention to provide 6 assignor a satisfactory method and means for attaching the tails to the end caps, whereby resistors can have their conducting films cut to the required form after the end caps have been applied to the cores, but before the tails have been connected to the end caps.
According to this invention, there is provided a method of manufacturing electrical resistors of the type having wire tails, such method comprising taking an element of rod form; fitting to each end of the said element a metal end cap having in its end surface an inward recess; forming, between the two end caps, an electrical connection of the desired resistance; applying a head formed on the wire tail to the recess in one of said end caps so as to position said tail with respect to said end cap; and then welding the head of said tail into the recess in the end cap.
According to a further aspect of this invention, there is provided a method of manufacturing electrical resistors, such method comprising taking an element of rod form furnished with a conducting film; fitting to each end of the said element a metal end cap having in its end surface an inward recess; cutting the film of the element to provide the desired resistive path; forming tails with a head at one end to be connected to the end cap; engaging the head of one of said tails in the recess in the end cap to which such tail is to be attached so as to posiof the resistor.
tion the tail with respect to the end cap; and then welding the tail to such end cap with the head of the tail pressed against the base of the recess in the end cap, which latter is supported on the opposite side by the core Preferably the said recess in each of the end caps is ofa part-spherical form and the head of the tail is of a corresponding shape so as to be capable of making a close fit with the recess over a substantial area to ensure adequate metallic and electrical contact between the tail and the end cap. p
The radius of curvature of the said part-spherical recess in the end cap is preferably approximately the same as the radius of curvature of the part-spherical head of the tail, although it may, in some cases, be desirable to producethese parts with initially slightly different radii of curvature.
The recess in the end cap will preferably be centrally located and it will be understood that in any case the inner surface of the end cap (at the base of the said recess) will bear upon the adjacent end of the core of the resistor and give a firm support for the end cap whilst the tail is being secured thereto. This firm support of the cap permits a reliable weld to be made without the usual arrangement of a welding electrode on the inside of the cap which is precluded when the tail is being welded to the cap after the fitting of the latter to the resistance core. If no recess were provided and even were the end cap pressed fully home, the end cap would be slightly resilient and would preclude the obtaining of a reliable electrical connection between the end cap and the tail prior to welding; the Weld might therefore be defective.
With this method as distinct from a soldering or brazing method, the welding takes place in a fraction of a second and generates heat only locally and causes no disturbance to the resistance element.
In order that the invention may more readily be understood, one method of carrying the same into effect is illustrated in the accompanying drawing which shows, in longitudinal section, the application of a tail to the end cap of a resistor.
In the drawing, the securement of the tail to the end cap is shown as being effected by the welding technique recently developed by the General Electric Co. Ltd. The
drawing shows a generally cylindrical core 1 made such as of metal or porcelain and having a thin film 2 of carbon deposited on the peripheral surface thereof. An end cap 3 formed as a brass pressing with a wall thickness of about .011" has been applied to the end of the core'linsuch a manner as to be in electrical contact with the car-. bon film 2. The end cap 3 is provided with a substantially central recess 4, the inner surface of which bears on the end face 5 of the core 1.
A tail 6 formed of S.W.G. copper wire is shown coaxially aligned with the recess 4, this tail having a substantial head 7 formed thereon by an upsetting operation such as that employed in the formation of heads on pins and other similar metallic objects. The radii of curvature of the recess 4 and head 7 are substantially the same.
An annular electrode 8 is coaxially engaged with the outer end surface of the cap 3 and a further electrode (not shown) is engaged with the tail 6, the head 7 of the tail being located within (but out of contact with) the annular electrode 8. On pressing the head 7 into engagement with the recess 4 (by advancing the tail in the direction of arrow A), current flows and a weld is efiected between the tail 6 and the end cap 3.
The recess 4 in the end cap 3 provides means for adequately positioning the tail 6 with respect to the end cap whilst the securement of these two parts co-axially together is being eifected and, by forming a substantial head 7 on the tail, an adequate electrical contact over a substantial area is provided between the cap and the tail and the danger of forming an imperfect or high-resistance joint is greatly reduced.
Alternatively, however, the annular electrode 8 above described may be replaced by clamping the second electrical lead to the outside periphery of the end cap 3.
It will be appreciated that by this invention the end caps can be secured to the cores prior to the cutting of the films of the latter so that this cutting operation can be effected to a very close tolerance and that the tails can subsequently satisfactorily be attached without affecting the resistance of the resistor.
It will be obvious that the present invention is also applicable to resistors in which a resistance element is wound upon an insulating rod. Such resistance element may, for example, be resistance wire or metalised glass fibre and may be Wound spirally upon the rod.
The rod, may, for example, be made of arceramic material such as porcelain or it may alternatively be made of sintcred alumina, e.g. that sold under the registered trademark Sintox.
I claim:
1. A method of welding an electrical lead to a metallic end cap for an insulating core carrying an electric resistive element which comprises the steps of forming an exterior recess on the end of said cap, fitting an end of said core within said cap until it abuts the inner wall surface of said recess, forming a protruding head on said electrical lead adapted to engage said recess, electrically connecting one of the electrodes of a welding apparatus to said lead, electrically connecting another electrode of said apparatus to a portion of the outer surface of said cap spaced from said recess, and then pressing said head into said recess bearing against said core to electrically weld said lead to said cap.
2. A method of welding an electric lead to a metallic end cap according to claim 1, including positioning said electrically connected lead in axial alignment with the recess in said cap, electrically connecting said other electrode to the periphery of said cap in spaced parallel relationship to said axially positioned lead and then moving said lead toward said cap, pressing said head into said core-bearing recess to undeformingly spot-weld said head therein.
3. A method of welding an electric lead to a metallic end cap according to claim 2, including surrounding said axially positioned lead with an annular electrode to coaxially engage the periphery of said cap.
4. A method of welding an electric lead to a metallic end cap for an insulating core carrying an electric resistive element which comprises the steps of forming a centrally positioned concave recess on the end of said cap, fitting said cap onto said core with the raised inner wall of said recess in abutting engagement with said core, forming a convex head on said electric lead complementary to said concave end, electrically connecting an electrode of a welding apparatus to said lead, electrically connecting another electrode of said apparatus to a portion of the outer surface of said cap spaced from said recess, and then pressing said convex head within said core-supported concave recess to undeformingly spot-weld said lead to said cap.
References Cited in the file of this patent UNITED STATES PATENTS
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB12862/54A GB783093A (en) | 1954-05-03 | 1954-05-03 | Improvements in or relating to rod-type electrical resistor elements having end capsand electrical wire tail connection leads |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2933589A true US2933589A (en) | 1960-04-19 |
Family
ID=10012506
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US505758A Expired - Lifetime US2933589A (en) | 1954-05-03 | 1955-05-03 | Electrical resistors |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US2933589A (en) |
| GB (1) | GB783093A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3173122A (en) * | 1962-06-18 | 1965-03-09 | Robert O Murry | Hermetically sealed resistor |
| US3173121A (en) * | 1962-06-18 | 1965-03-09 | Robert O Murry | Hermetically sealed resistor |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1701843A (en) * | 1924-12-31 | 1929-02-12 | Ford Henry | Method of welding wire wheels |
| US2003625A (en) * | 1932-03-04 | 1935-06-04 | Globar Corp | Terminal connection for electric heating elements |
| US2141932A (en) * | 1936-04-28 | 1938-12-27 | Gen Electric | Process for sealing receptacles |
| US2741687A (en) * | 1953-08-21 | 1956-04-10 | Erie Resistor Corp | Pyrolytic carbon resistors |
-
1954
- 1954-05-03 GB GB12862/54A patent/GB783093A/en not_active Expired
-
1955
- 1955-05-03 US US505758A patent/US2933589A/en not_active Expired - Lifetime
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1701843A (en) * | 1924-12-31 | 1929-02-12 | Ford Henry | Method of welding wire wheels |
| US2003625A (en) * | 1932-03-04 | 1935-06-04 | Globar Corp | Terminal connection for electric heating elements |
| US2141932A (en) * | 1936-04-28 | 1938-12-27 | Gen Electric | Process for sealing receptacles |
| US2741687A (en) * | 1953-08-21 | 1956-04-10 | Erie Resistor Corp | Pyrolytic carbon resistors |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3173122A (en) * | 1962-06-18 | 1965-03-09 | Robert O Murry | Hermetically sealed resistor |
| US3173121A (en) * | 1962-06-18 | 1965-03-09 | Robert O Murry | Hermetically sealed resistor |
Also Published As
| Publication number | Publication date |
|---|---|
| GB783093A (en) | 1957-09-18 |
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