US2394130A - Resistor and method of making - Google Patents

Description

Patented Feb. 5, 1946 RESISTOR AND METHOD OF MAKING Kenneth L. Woodman. Mansfield, Ohio, assig'nor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 27, 1943, Serial No. 480,732

13 Claims.

My invention relates, generally, to resistors and it has reference in particular to a'construction for, and a method of making, resistors of the type wherein the resistance element and terminals are secured to a support by a cementitious insulating material.

Generally stated, it is an object of my invention to provide a multiple terminal imbedded type resistor which is simple and inexpensive to manufacture and is durable in service.

More specifically, it is an object of my invention to provide for forming a plurality of resistor terminals with an integral connecting portion which serves to space the terminals relative to each other and relative to the resistor support during assembly.

It is also an object of my invention to provide for protecting the insulating material by which the resistor element is secured to the support.

Still another object of my invention is to provide for imbedding a protective screen in the insulating material covering a resistance element mounted on a metal base.

A further object of my invention is to provide for maintaining a predetermined spacing between a plurality of terminals during the manufacture thereof, and for supporting the terminals in predetermined relation to a support by means of a severable common connecting portion.

A further object of my invention is to provide for farming a plurality of terminals from a com-- mon strip of conducting material and leaving them connected by an integral connecting portion which may be removed therefrom after the terminals have been properly secured.

Other objects will in part be obvious, and will in part be explained hereinafter.

In practicing my invention a plurality of terminals for a resistance element which is to be secured to a metal support by a cenientitious insulating material are formed from a common sheet of material. The normally free ends of the terminals are left connected to a common ment and the portions of the terminals connected thereto. A protective metal screen positioned over the element is bonded to the support by the insulating material. When the insulating material hardens, the common connecting portion of the terminals may be removed therefrom, leaving the terminals properly spaced and firmly secured.

For a more complete understanding of the nature and scope of my invention, reference may be had to the following detailed description which may be read in connection with the accompanying drawing, in which:

Figure 1 is a partially broken out plan view of a resistor embodying the principal features of the invention:

Fig. 2 is a sectional view taken along the line 11-11 before the common connecting portion of the terminals is removed;

Fig. 3 is a plan view of the terminal assembly before the common connecting portion is removed;

Fig. 4 is an end elevational view of the terminal assembly of Fig. 3; and

Fig. 5 is a side elevational view of the terminal assembly of Fig. 3.

Referring to Fig. 1 the reference numeral l0 may denote, generally, a resistor of the. type wherein one or more resistance elements Il may be secured to a metal support i2 by means of a cementi'tious insulating material i3 and provided with one er more sets of terminals (4 for effecting connection thereto at spaced intervals. A protective screen i5 may be provided for protecting the resistor against damage from shock.

Referring to Figs. 1 and 2 it will be seen that the support l2 may comprise a substantially recvided on the end portions for a purpose which 4 will be explained hereinafter.

Since the resistance element I l is to be secured to the support II by means of the cementitious insulating material [3 and provided with a plurality of relatively closely spaced terminals it, it is necessary to insure the proper spacing of these terminals during assembly, and before they are firmly secured to the base by the insulating material.

Accordingly, as shown in Figs. 2 through 5, the terminals H may be formed in any suitable manner such as by punching or forming them from a common strip of conducting material. Instead of forming the terminals (4 separately, they may be formed with a common connecting strip 28 joining the normally free ends. Openings 30 may be provided in the terminals adjacent the connecting strip for eifecting the connection of a conductor thereto when the resistor is completed, and means such as the upstanding lugs or ears 3'2 may be provided adjacent the other ends of the terminals for efiecting a connection to the resistance element.

The terminals may be of any desired shape ha ing, as shonh, in the present instance, somewhat of a Z-shape with a substantially ho Zzontal portion adiacent the common connectin strip a substantially vertical intermedia portion adjacent the end to be connected to the resistance element. The end to connected to the resistance e ement may be "bstantially pa ailel connection cement as J- bElo generally may have various of the invention.

the

el. are relative ng the m....iufac tu"e oi the us may be provi 6. such as For example, the 23 may be formed ed to engage the are of the ears as no" i i in predetermined relation The feet 2'! may be arranged ncnn eing, for example, connected 1G proiectm is of the common connecting by means of dependent intermediate ns -16, so as to be positioned in a plane stantially parallel to the ends of the termina s to be connected to the resistance element 5 i at pre etermined distance below said ends. As shown in 2 this enables the lower ends of the terminals 5 to be positioned a predetermined distance above the relatively flat back portion E8 of the support, so as to insure adequate insulation being provided between the terminals and support.

After the cementitious insulating material l3 has been applied about the resistance element and. the lower ends of the terminals, the connecting portion and the projecting end portions may be severed from the terminals leaving them accurately positioned and ready for use. Where a relatively light material is used for forming the terminals i4 it may not be necessary to make any particular provision for the severance of the connecting portion therefrom, since this may be easily done by means 01' shears or punching after the resistor is assembled. If it is desirable, however, the terminals may be partially severed from the connecting strip during the origina1 forming operation either by partially shearing the terminals H from the connecting strip 28 along the dotted lines ll or by providing suitable holes at th junction of the terminals and the connecting strip to weaken the union therebetween sufliciently to enable the connecting strip to be readily detached after the resistor is assembled.

In order to protect the completed resistor against damage from shock, which may crack the insulating material l3 or even rupture the bond thereof with the support H, the resistor may be provided with a protective screen IS. The screen l5 may be of any suitable design, comprising a perforated plate of metal or any suitable material having sufilcient mechanical strength, or a screen, wire mesh or the like. As shown the shield l5 comprises a screen of cross wires 42 and 43. It may be secured in any suitable manner being, for example, initially positioned relative to the support I! by means of projections 44 of the cross wires 42 which may be retained either by merely bending the ears 26 at the ends oi th support thereover or by passing them through openings in the cars 26. When the insulating material 13 is flowed over the resistance element and support, the screen i5 1:" cross imbedded therein and may be bonded L0 so as to substantially reinforce the insulating material and protect the resistance element from damage.

The resistance element may be a se led in any suitable manner, such as by first cing a mery layer of insulating material 5 o er the oe or the support 52, bend rminals l4 ment ii -th the er of material s -i as in appiied around stance element ay then be placel on "eccndary r1153 projecting 34 in th" 0 26 and bending the cars 25 or tertiary layer of then be applied over the protective S01 If the insulating material i3 is of th.

-nings in the ears ,5; further weirdly.

' type the difierent layers may either be fused or partially ifused as they are applied or they may be left in the uniused state and all fused simultaneously in a single heating operation. Likewise, if the insulating material is of a hydraulic type, the different layers may be allowed to set before the subsequent layer is applied or they may be applied one after the other and set in a single operation. Where insulating materials of the synthetic type are used for hardening by polymerization it may be desirable to use a single treatment for curing the different layers in order to permit them to fuse into a substantially homogeneous mass such as may be secured with the other types of insulating materials in either the step by step or the simultaneous operation.

When the resistance element and terminals are applied to the support, the terminals are accurately positioned relative to one another and to the support by inserting the bosses 38 on the feet of the projection and portions of the common connecting strip in the openings 2| in the ears 20 at the ends of the support 12. I! desired, screws or other suitable means may be used to further insure the positioning of the feet 31 relative to the cars 20. After the insulating material I! has flowed around and between the turns of the resistance element the ends of the terminal members and the cross wires of the screen l5 bonding them inseparably together, the common conend secured to the element and the other end necting portion 20 of the terminals, together with the projecting end portions 28 and the feet Il may be severed from the terminals, leaving them accurately spaced relative to each other and to the support l2.

From the foregoing description and the accompanying drawing it will be apparent that I have provided in a simple and effective manner for assembling a, plurality of terminals on a resistor of the imbedded type. Accurate positioning of the terminals relative to the resistor support and to each other is positively assured and removal of the positioning means may be easily effected. By protecting the resistance element through the use of a protective shield or screen imbedded in the insulating material the durability of the imbedded type resistor is greatly increased. The effective bonding power of the insulating material is also increased so that the bonding of the terminals themselves to the support is thereby improved since cracks in the insulating material which may develop at points more or less remote from the terminals are prevented from separating into the region where the terminals are located.

Since different embodiments of the invention may be made other than those illustrated, without departing from the spirit and scope of the invention as defined, it is intended that all the matter contained in the accompanying description and shown in the'drawing shall be considered as illustrative and not in a limiting sense.

I claim as my invention:

1. A resistor comprising, a relatively flat support, a resistance element mounted on said support, a plurality of terminal members having feet portions substantially parallel to the support connected to the elementand portions projecting at substantially right angles to the support, a cementitious insulating material substantially surrounding the resistance element and feed portions and securing them to the support.

2. A resistor comprising, a metal base, a resistance element positioned on the base, a plurality of contact members having portions in substantially the plane of the element secured thereto at projecting therefrom in a plane parallel to but spaced from the plane of the end secured to the element, and a fusible cementitious insulatin material positioned about the element and the ends of the terminals secured thereto fusibly bonding them to the base.

.6. A resistor comprising, a substantially flat metal tray having upstanding edges, a resistance element positioned in the tray, a plurality of elongated sheet metal terminals arranged in spaced relation adjacent one edge of the tray and having terminal portions projecting at an angle to the tray and feet portion in substantially parallel relation to the tray secured to the resistance element at spaced intervals.

7. A multiple terminal assembly comprising, a

. plurality of spaced terminal members formed spaced intervals and angularly related portions projecting away from the base, a cementitious insulating material surrounding the resistance element and the first mentioned portions of the contact members to secure them to and insulate them from the base.

3. A resistor comprising, a resistance element having projecting terminals, 9. metal support positioned on one side of the element and in spaced relation thereto, a metal screen positioned on the other side of the element in spaced relation, and a fusible cementitious insulating material substantially surrounding the -element fusibly bonded to the screen and support.

4. A resistor comprising, a relatively flat metal support having upstanding edge portions, a resistance element positioned in predetermined spaced relation to the support, a shield positioned on -the side of the element remote from the support and operatively connected to the edge portions of the support, and a vitreous insulating material substantially surrounding the element and fusibly bonding it to the support and shield.

5. A resistor comprising, a substantially rectangular base having supporting ears at each end and upturned side portions, a resistance element supported on the base having a. plurality of elongated terminal members positioned at spaced intervals adjacent one edge of the base having one from sheet metal, removable connecting means integrally formed with the terminal members to maintain a predetermined spacing thereof during assembly, and positioning means projecting from the connecting means adjacent the ends integral with the connecting means having a portion thereof in predetermined relation to portions of the terminals for positioning them in predetermined relation to a support during assembly.

8. A terminal structure for a resistance elemen mounted on a support comprising, a plurality of elongated sheet metal terminal members having means at one end for connection to a conductor, and a severable connecting strip connecting the other ends to maintaining the terminal members in predetermined alinement and spaced relation during assembly and having integral depending end portions projecting from the connecting strip for positioning the terminal members relative to the support during assembly.

9. The method of making a resistor having a plurality of terminals connected to a resistance element which comprises, forming the plurality of terminal members from a single piece of conducting material having a severable connecting. portion along one end, securing the other ends to the resistance element and applying the resistance element and terminals to a support, applying a cementitious insulating material over the element. and at least a portion of the terminals to bond them to the support, and removing the common connecting portion from the free ends of the terminals.

10. The method of making a multiple terminal resistor which comprises, forming a plurality of spaced terminals from a piece of conducting material having means at one end to make connection to a resistance element and having an integral' connecting strip at the other, connecting the first-mentioned ends to the resistance element applying the terminals and element to a support, surrounding the element and the first-mentioned end portions of the terminals with a cementitious insulating material, and severing the connecting portion from the other ends of the terminals when the insulating materialhardens.

11. The method of alining a plurality of spaced terminals for connection to a conductor which comprises forming the terminals from a common piece of conducting material in predetermined spaced relation with means for effecting connection to the conductor at one end and a severable spacing and connecting strip integral therewith at the other, connecting the terminals to the conductor and securing them in the desired relation thereto, and then severing the connecting strip therefrom.

12. The method of making a resistor having a plurality of spaced terminals connected to a resistance element imbedded in a vitreous enamel on a metalsupport which comprises, forming the terminals in the desired spaced relation from a common sheet of conducting material with spaced ears at one end to grip the resistance element and a common connecting portion at the other with projecting end portions positioned in predetermined relation to the ends having the spaced ears, applying the terminals to the element, applying the element and terminals to the support with the projecting end portions supporting the terminals relative to the support, applying a oementitious insulating material about the element and the portions of the terminals secured thereto, and removing the connecting portion and projecting end portions from the terminal portions. 2

13. The method of makinga multiple terminal resistor which comprises, forming a plurality of spaced terminals from a common sheet of conducting material with a common connecting portion at one end and projecting ears at the other end for gripping a resistance element, securing the terminals to the resistance element while spaced by the common connecting portion, positioning the element and terminals on a metal base having a layer of cementitious insulating material thereon, covering the element and the ends of the terminals secured thereto with additional cementitious insulating material, placing a protective screen over the element and securing it to the base, treating the cementitious material to bond with the base, resistance element and protective screen, and subsequently removing the common connecting portion.

KENNETH L. WOODMAN.

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