US2857498A - Wall mounted resistor - Google Patents

Description

United States Patent O WALL MOUNTED RESISTOR George Risk, Columbus, Nehru, assignor to Dale Products, Inc, Columbus, Nebr.

Application March 21, 1955, Serial No. 495,726

6 Claims. (Cl. 201-63) This invention relates to resistors for electronic circuits and more particularly it is an object of the invention to provide a resistor adapted to be mounted through a wall of the chassis of such a circuit, the resistor being of miniature size for the conservation of space.

It has heretofore been recognized as desirable to construct a resistor in a way adapted to be mounted through a hole in a wall of a chassis. However, it has been thought impossible to construct a resistor for such mounting and which would further be of miniature form to conserve space without sacrificing the power rating of the resistor. This has been because resistors have been constructed heretofore with their heating elements in the shape of small cylinders with terminal wires extending outwardly from each end.

In a wall-mounted resistor it is necessary for both terminals or leads to extend outwardly from only one end of the resistor. Obviously this would necessitate causing one of the leads to be doubled back alon the outside of the resistor. In such a construction the lead would have to be insulated from the remainder of the resistor and would also have to be spaced from it a considerable distance in order to prevent dielectric breakdown of the insulation between the two leads.

An objective and concept of my invention is to make it possible for the resistor to be made of small size through attaching one of the leads to the inner side of its cap, rather than the outer side as is customary, and extending this lead down through the center of the hollow cylindrical resistor coil supporting member.

A particular object is to provide a resistor as described the housing of which is adapted to be drawn tightly against a wall of a chassis for contact therewith over a substantial and large area for the use of the wall to dissipate heat from the resistor, further making practical the use of a very miniature size of resistor without sacrificing the power rating thereof.

Still another object is to provide an aperture in that end of the housing which is opposite the leads for permitting the escape of fluid insulating material therethrough during insertion of the resistor core, the fluid insulating material then filling the space between the core and resistor housing as is common in the prior art.

Still further objects of the invention are to provide a resistor as described constructed in a fashion for maintaining the leads in positions sufficiently spaced apart as to prevent dielectric breakdown of insulation disposed between the leads.

In the drawings:

Figure 1 is a cross sectional view taken diametrically through a wall-mounted resistor of this invention, a portion of a wall being also shown in cross section in Figure 1.

Figure 2 is an exploded view of the wall mounted resistor of this invention.

The wall mounted resistor of this invention has an outer housing generally indicated at which latter is provided with a larger portion 12 adapted to be disposed 2,857,498 Patented Oct. 21, 1958 on one side of a wall 14 having an opening 16 therethrough. The resistor 10 has an end portion 20 of smaller diameter than the larger end portion 12, the end portion 20 being of cylindrical shape on its exterior, its exterior being threaded to receive a nut 24 best seen in Figure 1. The nut 24 is preferably of a heat ond ctive material such as metal and is adapted to engage one side of the wall 14 around the opening 16, the inner end of 1 the portion 12 of the resistor overlapping the opening 16 on the other side of the wall 14 whereby the nut 24 holds the resistor housing 10 securely to the wall 14.

The wall 14 shown in Figure 1 represents a section a of a wall forming a part of the chassis of an electronic device of any kind, such walls being ordinarily of metal and being therefore highly heat conductive. For this reason the mounting of the resistor 10 on the wall 14 causes a dissipation of heat from the resistor through the wall 14 which has advantages in maintaining the housing of the resistor at cooler temperatures whereby the resistor 10 can be made of a more miniature size than would be otherwise possible, for the same resistor power rating.

The larger housing portion 12 is provided with a plurality of circumferentially extending spaced apart ribs 30. The larger housing portion 12 and the smaller housing portion 20 of the resistor are preferably integral and the smaller housing portion 20 has a hollow interior wall of a cylindrical shape and indicated at 40, the cylindrically shaped wall 40 extending through an open outer end of the smaller portion 21 of the resistor and inwardly through the housing portion 20 and into the housing portion 12 to a point spaced only a short distance from the outer end 42 of the housing portion 10, terminating in an end wall 44.

The hollow interior of the resistor is for the purpose of receiving a coil of resistance wire 50 best seen in Figure 2 and wound about the outer side of a resistor core 52 formed of an electrically insulating material such as ceramic material commonly used in the manufacture of resistors. The core 52 is preferably of approximately cylindrical shape on its outer circumference and has a hollow interior, being open at each end. On the outer end of the resistor core 52 a metal band 56 is provided extending circumferentially around the core 52 between the outer end of the core and the wire coil 50 which latter is disposed spaced inwardly from the outer end of the core. The band 56 is formed of an electrically conductive material and the outer end 70 of the coil of wire 50 is electrically connected to the band 56.

At the inner end of the core 52 the coil of resistance wire 50 terminates a short distance from the inner end and a cap 72 is disposed over the inner end of the core 52, the cap 72 having a concave side receiving the adjacent end of the core 52. The cap 72 is preferably formed of electrically conductive material and the adjacent end 74 of the resistance wire coil 50 is electrically secured to the cap 72. A first lead or terminal of the resistor is disposed adjacent one side of the inner wall 40 of the hollow interior of the housing portion 20 as seen in the upper left hand corner of Figure 1. The lead 80 has an opening therethrough at 82 as is common. The lead 36) extends inwardly parallel to the axis of the resistor housing portions 12 and 20 and is attached by means of a collar to the band 56. The collar 90 is preferably of cylindrical shape open at its center and is adapted to tightly fit around the band 56 for good electrical connection therewith and a portion 94 extends outwardly from the collar 96) and is offset inwardly therefrom receiving on its outer side the inner end of the lead 80 which latter is attached thereto securely for good electrical connection.

Another or second lead 100 of the wall mounted resistor is disposed adjacent an opposite side of the inner 3 wall 40 of the housing portion Ztl. The lead 100 is disposed in parallelism with the lead 80 and with the wall 40 and has at its outer end an opening 102 similar to the opening 82 transversely through the lead Stl.

The lead ltltl extends inwardly to a point closely spaced from the outer end of the core 52 and has an inwardly inclining transverse portion 103 which latter extends inwardly to a point spaced slightly inwardly from the inner wall of the hollow core 52 there adjoining an innermost offset portion 105 of the lead 1%, the portion MP extending inwardly in parallelism with the inner wall of the core 52 and in parallelism with the axis of the resistor inwardly to a point adjacent the cap 72. The inner end of the offset portion 1'95 of the lead 1% terminates in a portion 107 set at a right angle to the portion 105 and suitably secured to the adjacent side of the cap 72 for good electrical contact therewith.

As the resistor is intended to be made on a very miniature size it is very important that the leads Bill and tilt) are not disposed close to one another at any point. This is the chief reason for the unusual expedient of placing the lead 100 in the position extending through the center of the core 52. To further hold the lead 86 and lltltl apart, a header 121i) is provided. The header 120 is formed of an electrically insulating material, preferably ceramic, and has a cylindrical outer surface for snugly fitting the cylindrical wall 46 of the portion 2% of the resistor housing 10. The ceramic header 129 has two parallel openings therethrough indicated at 122 which are for the purpose of receiving the leads fill and Hill. The openings 122 are disposed on opposite sides of the header 120.

At the inner end of the resistor, a plug 13% is provided, the plug 13%) being formed of electrically insulating material and can preferably be formed of ceramic material. The plug 130 is of a cylindrical shape although it is thin and has apertures 132 extending therethrough on opposite sides thereof for receiving the leads 8t and 1130. The outer circumference of the plug 130 is similar to the inner circumference of the wall 40 for a snug fit.

In assembling the resistor the lead 1% can first be mounted upon the cap 72 whereupon the cap 72 is placed upon the core 52 containing the wire resistor coil 59 thereon. The adjacent end 74 of the wire Etl is then connected to the cap '72 and the band 56, and the collar 90 is placed thereon, a connection being made between the latter and the adjacent end "ill of the coil 50. The lead 89 can then be attached to the portion 94 of the collar 90 following which a Piberglas" sleeve 150 is slipped over the coil 5a. A suitable insulating material 162 such as silastic, which is liquid when first applied, is worked into the Fiberglas sleeve 15% filling the pores therein and binding it to the coil 5i Next, a spacer washer 169 of cylindrical shape and having an open center is placed in the hollow interior of the resistor housing portion 12 and against the inner end thereof.

The hollow interior of the housing of the resistor is at least partially filled with more of the electrically in sulating material 162, preferably Silastic, which is liquid when it is put on, then later gets solid and has a capacity to withstand heat, retaining its electrically insulating qualities after long periods of use.

Next, the resistor coil portion Stl with its sleeve 150 mounted thereover is inserted into the hollow interior of the main or larger portion 12 of the resistor, the space between the sleeve T154 and the inner wall it of the resistor housing being filled with the somewhat liquid insulating material 162 which had been placed in the housing as described before.

in order to insure that all of the interior of the resistor will be filled and leaving no air spaces, the outer end of the resistor housing portion 12 is provided with an opening 170 therethrough which permits escape of the silastic material 162 as the coil portion 50 of the resistor is inserted into the hollow interior of the housing. The opening 170 is of cylindrical shape in an outer portion and the opening 170 has an inner portion which is outwardly flared as best seen at 172. As thus described, the silastic material 162 is free to flow through the opening 17d and to ooze outwardly of that side of the resistor and because the silastic material 162 is capable of flowing and yet is nearly solid, it is very satisfactory for filling the interior of the resistor.

Following this, further silastic is placed in the interior of the core and sufiiciently to fill a space between the core 52 and the header 12%, this space being relatively thin but of a sufficient thickness for receiving therein the portion 163 of the lead ltlt) and the portion $4 of the collar 9%.

Next, the header 120 is placed over the terminals and liltl and is inserted in the housing portion 2% being then followed by the plug 13% to close the inner open end of the resistor housing. Lastly, the resistor is baked, as is usual.

it will be seen that during use the area on both sides of the Wall 14 is in contact with air in the area substantially around said opening whereby the wall 14 dissipates heat to the air.

Likewise it will be seen that during use the resistor housing it? is in contact with the air substantially on all outer surfaces thereof except adjacent to the wall 14 whereby it cannot dissipate heat in any other way as easily as it can to the wall 14 because the wall 14 is formed of metal which is a material more heat conductive than air.

As thus described, it will be seen that this invention has provided a resistor adapted to be mounted in a wall of a chassis of an electronic circuit, the resistor being miniature in form in relation to its power rating and fulfilling the above described objects of the invention.

From the foregoing description, it is thought to be obvious that a wall mounted resistor constructed in accordance with my invention is particularly well adapted for use, by reason of the convenience and facility with which it may be assembled and operated, and it will also be obvious that my invention is susceptible of some change and modification without departing from the principles and spirit thereof, and for this reason I do not wish to be understood as limiting myself to the precise arrangement and formation of the several parts herein shown in carrying out my invention in practice, except as claimed.

I claim:

1. In combination: a resistor having an outer housing having a portion adapted to be disposed through an opening in a wall of a chassis of an electrical circuit, said housing having a hollow interior open at one end, a hollow resistor core disposed in said interior, said core being open at two opposite ends thereof, a resistor coil disposed around said resistor core, a cap disposed extending over an inner end of said resistor core, said cap being electrically connected to the adjacent end of said resistor coil, a first lead attached to the inner side of said cap and extending through the hollow interior of said resistor core and outwardly through the other end of said resistor core and outwardly through the open end of said housing, a band of electrically conductive material disposed around the opposite end of said resistor core from said cap, means connecting the adjacent end of said coil to said band, a second lead disposed extending through said open end of said housing and into the hollow interior of said housing, means connecting said second lead to said band, insulating means filling the interior of said housing in the space between said coil and the interior wall of said hollow housing, said insulating means being of a type capable of holding its insulating properties operably during operation of the resistor.

2. The combination described in claim 1 in which said insulating means comprises a material which is before curing a liquid of low viscosity which is of an electrically non-conductive nature during operation of the resistor, said housing having an outlet opening through the end thereof opposite the said open end, said opening being for the purpose of permitting outward oozing of said low viscosity insulating material whereby said core can be inserted into said resistor at a time when some of said low viscosity insulating material is disposed in the hollow interior of said resistor because of the possibility of the oozng outwardly of said high viscosity insulating material through said outlet opening.

3. A resistor as claimed in claim 2 in which a header is provided and disposed near the open end of said housing, said header being of an electrically insulating nature and being partially disposed between said leads and having openings therethrough for receiving said leads therethrough.

4. The combination claimed in claim 2 in which a filler cap is disposed in the inner open end of said resistor, said filler cap being formed of electrically insulating material and having two openings therethrough receiving said two leads therethrough.

5. The resistor described in claim 2 in which said first lead extends through said core along one side of said core and has an outwardly extending portion adjacent the opposite end of said core from said cap, said first lead having a portion oflset inwardly from that portion thereof which is disposed in said core, said portion extending outwardly through the opening in said resistor having on that side of said resistor housing which is opposite said second lead.

6. The resistor described in claim 1 in which said first lead has an inner end portion extending through said core closer to the respective side of said core than to the other side and said first lead having an outwardly extending central portion connected to said inner end portion and disposed adjacent the opposite end of said core from said cap, and said first lead having an outer end portion ofiset to the side with respect to said core from that portion thereof which is disposed in said core, said outer end portion of said first lead extending outwardly through the open end of said resistor housing on that side of said resistor housing which is opposite said second lead.

References Cited in the file of this patent UNITED STATES PATENTS Burgun Oct. 31, 1950

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