US2736783A

US2736783A - Terminal construction for variable resistors

Info

Publication number: US2736783A
Application number: US379912A
Authority: US
Inventors: Arthur M Daily
Original assignee: CHICAGO TELEPHONE SUPPLY CORP
Current assignee: CHICAGO TELEPHONE SUPPLY Corp
Priority date: 1953-09-14
Filing date: 1953-09-14
Publication date: 1956-02-28
Anticipated expiration: 1973-02-28

Description

Feb. 28, 1956 A. M. DAILY 3 3 TERMINAL CONSTRUCTION FOR VARIABLE RESISTORS Filed Sept. 14, 1955 2 Sheets-Sheet l Feb. 28, 1956 A. M. DAILY 5 1 TERMINAL CONSTRUCTION FOR VARIABLE RESISTORS Filed Sept. 14, 1953 2 Sheets-Sheet 2 THICKNESS OF CONDUCTIVE LAYER EXAGGERATED.

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United States 2,736,783 l e-iterated Feb. 28, 1956 2,736,7ss TERMINAL coNsTnucrro-N .ron vnnranm Rust Chicago Tele- Arthur M. Daily, Elkhart, Ind, assignor to sea -es 4 Claims. (35.

This invention relates to variable resistors of the type used in radio and television apparatus and refers more particularly to the manner in which the resistance element which is in the form of a flat split-ring is secured to the base of the instrument and provided with end terminals.

This invention, therefore, is directed to the same general problem which motivated the invention covered by Patent No. 2,632,832, issued March 24-, 1953, but has as its purpose to improve upon the structure covered in sadi patent. As in the Patent No. 2,632,832, the present invention obviates the need for rivets which are usually employed to secure the terminals to the ends of the resistance element and to hold the resistance element in place on the base. The use of such rivets has many disadvantages among which might nentioned the fact that during the tightening thereof rivets frequently expand and burst the base.

Though the structure covered by the aforesaid patent obviates the need for rivets and is generally satisfactory, it does have a disadvantage whtich can be quite troublesome in production, and this difriculty flows from the very essence of concept upon which that patent rests. Since the object there was to have flat surface-to-surface engagement between the terminal tab of the resistance element and the stamped sheet metal terminal unit, the fastening of the terminal unit had to be effected in a manner which would not interfere with or destroy this desired flat surface-to-surface engagement. Accordingly, the attaching ears were staked in place, but to secure good results the staking pressure had to be held closely within rather critical limits. Obviously this is not easily done in mass production.

The present invention overcomes this disadvantage and for the first time makes possible the use of what might be considered the natural way of fastening the stamped terminal unit in place. in other Words, the present invention enables the securement of the terminal unit by the simple expedient of clinching ever a pair of attaching ears provided by the legs of a U-shaped attaching portion. Heretofore, this simple method of fastening could not be used since the act of clinching over the ears causes the contact portion or bight of the stamped terminal unit which overlies the contact surface of the resistance element tab to be bowed away from this surface, and this, of course, results in a poor and unstable contact.

The present invention overcomes this objectionable consequence. Hence, it might be said that the object of this invention is to provide a stamped terminal unit for securing a resistance element to its base which is so designed and constructed that it permits the securement thereof by the ordinary expedient of clinching over a pair of opposed attaching ears and at the same time assures a good stable electrical contact between the terminal unit and the resistance element despite the fact that the portion of the unit between is attaching ears is inevitably bowed away from the terminal tab it overlies as the ears are clinched over.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiments of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure l is a perspective view showing the inside aspect of the stationary element or assembly of a variable resistor embodying this invention;

Figure 2 is a plan view of the front or outer face thereof;

Figure 3 is a perspective view of only the base and resistance element thereon viewed from the inner face thereof but minus the center terminal and its collector ring and with one of the end terminals removed from the assembly but shown alongside thereof;

Figure 4 is a detail sectional view through Figure 2 on the plane of the line 44; and

is an enlarged detail sectional view through Figure J Figure 4 on the plane of the line 5-5, and illustrating the mounting ears in broken lines the disposition of before they are clinched over.

Referring now particularly to the accompanying drawin s, the numeral designates the base of a variable resistor which, as is customary, is die-cut from suitable insulating material to provide a generally circular body portion 5 and a radially extended terminal supporting segment 6.

Mounted upon the inner face of the base is a resistance element 7 which is generally circular but more spec iically is in the form of a split ring having outwardly projecting terminal tabs 8 on the ends thereof. The movable contactor (not shown) of the resistor sweeps across the face of the element '7 during adjustment of the instrument which adjustment is brought about by rotation of a shaft (also not shown) rotatably received in a bearing bushin. 9 fixed to the base by having a part thereof entering and rolled over the edge of a hole it in the base.

The movable contactor or arm of the instrument has resilient collector brushes thereon which ride upon a collector ring 11 overlying the inner face of the base concentrically within the resistance element 7. Supporting

feet

12 and 13 project from the collector ring 11 to space the collector ring from the base, and a radially projecting terminal strip indicated generally by the numeral 14 extends from the foot F12.

The portion 15 of the terminal strip which joins with the foot 12 is on a level beneath the bottom of the foot 12 so that it extends down into a hole 16 in the base to provide electrical clearance between the resistance element and the collector ring terminal strip. Outwardly of its portion 15 the terminal strip is offset as at 17 to embrace the land between the hole 36 and a notch 18 in the outer edge of the segment 6. These interengaging portions of the terminal strip and base plus two ears 19 which project from opposite side edges of the terminal strip close to the outer end of its offset 17 and engage over the outer face of the base as shown in Figure 2, locate the collector ring and its terminal upon the base.

The resistance element '7 is secured to the base 4 by a stamped sheet metal terminal unit indicated generally by the numeral 21 embracing each terminal tab 8 and clamping it to the base. This stamped sheet metal terminal unit has a U-shaped attaching end providing a contact portion 21 flanked by a pair of identical parallel attaching ears 22 and a terminal strip 23 which projects from the contact portion 21. The terminal strip may be straight as shown or bent to dispose its outer extremity 24 in any position required for soldered connection with the conductors (not shown) of the circuit in which the instrument is to be connected.

As will be readily understood the U-shaped attaching end of the terminal unit straddles its respective tab 8, and its ears 22 pass through rectangular holes 25 in the base and have the ends thereof clinched over at the underside of the base as at 26.

As best shown in Figure the terminal units embrace the tabs 8 very snugly so that when the ends of the cars 22 are clinched over, the side edges of the tabs will be crowded down into the corners of the terminal units between the ears and the contact portion 21. This results in a good electrical connection between the terminal unit and the active surface 8 of the resistance element but as pointed out hereinbefore, the clinching over of the attaching cars has a tendency to how the contact portion 21 outwardly and away from the active contact surface 8' of the tabs.

To preclude the objectionable consequences of such outward displacement of the contact portion a pimple 2'7 is formed therein, which, upon application of the terminal unit to the assembled resistance element and base, enters a hole 23 in the tab. The diameter of this hole is less than the base or maximum diameter of the pimple, and the pimple is generally conical and has an altitude sufficient to insure its entry into the hole a substantial distance but not far enough to penetrate all the way through the terminal tab. Hence, the conical side of the pimple is drawn firmly against the rim of the hole as the attaching ears are clinched over, and since the rim of the hole thus engaged by the side of the pimple is defined by the active contact surface material 8 a good stable low resistance electrical connection is established at this point. This connection along with the connections at the side edges of the tabs assures the desired low resistance junction between the terminal units and the resistance element, especially since the engagement of the sides of the pimple with the rim of the hole places the bight or contact portion 21 under tension. 1

Also, since the conical pimple is drawn into the hole during the clinching of the ears there is a slight crowding of the active contact surface of the tab between the pimple and the inner faces of the attaching ears which further assures a good stable connection between the terminal and the tab 8.

The entry of the pimples into the holes 28 has another important function. it locates the resistance element on the base. To this end the ears 22 are of a width to closely fit the length of the holes and the distance between the ears is the same as between the holes. Consequently, upon insertion of the cars into the holes 25 the terminal units are fixed against shifting laterally upon the base and the pimples 27, upon entering their respective holes in the tabs draw the tabs radially in or out as required to properly locate the resistance element upon the base.

From the foregoing description taken in connection with the accompanying drawings it will be readily apparcut to those skilled in the art that this invention provides an extremely simple but very efiective-manner of simultaneously securing the resistance element to the mounting base and providing solder terminals for the resistance element; and that its unprecedented simplicity flows from the fact that the invention makes possible for the first time using what might be considered the normal way of fastening a terminal such as this in place since it not only eliminates the possibility of having the contact portion of the terminal bowed away from and out of contact with the contact surface of the tab but actually improves the electrical connection between the terminal and the contact surface of the tab.

What i claim as my invention is:

1. In a variable resistor having a base and a fiat, split ring-shaped resistance element with a fiat terminal tab projecting from each end thereof flatwise overlying the base, common means for securing the resistance element to the base and for providing terminals for the ends of the resistance element, comprising: a sheet metal stamping clamping each terminal tab to the base, said stamping having a Ll-shaped attaching end, the bight of which provides a contact portion and the legs of which provide a pair of opposed attaching ears, said U-shaped attaching end straddling the terminal tab with its contact portion contiguous to the top face of the terminal tab and its attaching ears passing through holes in the base, the ends of said attaching ears being clinched over the underside of the base; each terminal tab having a hole opening to its top face; and a pimple-like protrusion on the contact portion provided by the bight of theattaching end of the stamping projecting into and pressing against the rim of said hole in the terminal tab.

2. in a variable resistor, the structure set forth in claim 1 further characterized by the fact that the pimplelike protrusion is substantially conical and has an altitude suliicient to penetrate a substantial distance into hte hole but not all the way therethrough, and wherein the base diameter of the pimple-like protrusion is sufiiciently larger than the hole to assure that the rim of the hole engages the side of the pimple-like protrusion at an elevation sufiicient to place the bight of the U- shaped attaching end under tension.

3. In a variable resistor of the type set forth in claim 1, the structure defined therein further characterized by the fact that the attaching cars so fit the holes in the base that the stamping is firmly held against shifting laterally on the base, and that except for the engagement of the pimple-like protrusions with the rims of the holes in the terminal tabs said tabs would be movable radially of the resistance element so that the pimple-like protrusions serve to locate theiresistance element on the base.

4. A combination terminal and anchoring unit for variable resistors in which a fiat split ring-shaped resistance element fiatwise overlies the base of the resistor,

comprising: a sheet metal stamping having a U-shaped attaching portion and a terminal portion extending from the bight of the attaching portion, the legs of said U- shaped attaching portion providing attaching ears by which the unit may be clinched to the base of the resister with the attaching portion straddling a terminal tab on the resistance element; and a pimple-like protrusion on the bight of the attaching portion facing inwardly to press against a portion of the terminal tab.

References Cited in the tile of this patent UNITED STATES PATENTS 1,587,696 Carter June 8, 1926 2,138,210 Schellenger Nov. 29, 1938 2,570,968 Muller Oct. 9, 1951