US2927294A

US2927294A - Variable resistor

Info

Publication number: US2927294A
Application number: US626847A
Authority: US
Inventors: Marlan E Bourns
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-01-12
Filing date: 1956-12-07
Publication date: 1960-03-01
Anticipated expiration: 1977-03-01

Description

March 1, 1960 M. E. BoURNs VARIABLE RESISTOR Original Filed Jan. l2, 1953 INVENToR. MH/P/.H/Y E BOU/EWS United States Patent O VARIABLE RESISTOR Marlan E. Bourns, Riverside, Calif;

1o Claims. (Cl. ass-iso) The present invention relates to variable resistors or potentiometer-s, and is a divisio'n of my pending application, Serial No. 330,642, tiled January 12, 1953, now Patent No. 2,777,926, entitled Variable Resistor. This invention is primarily concerned with high precision instruments of the type used in guided missiles, aircraft, and other complex electronic equipment, and the primary object of the invention is to provide a variable resisto'r or potentiometer which is extremel-y compact, yet designed for extremely precise adjustment, and capable of giving accurately reproducible results. i

Another object of the invention is to` provide a variable resistor which will withstand acceleration, vibration, and

. extreme ranges of temperature such as an instrument of this type may be exposed to in aircraft or in guided missile use.

These and other objects and advantages of the invention will become apparent to those skilled in the art upon consideration of the following `detailed description or" the preferred forms thereof, reference being had to the accompanying drawings, wherein: t

Figure 1 is a longitudinal section through one embodiment of the invention taken at the planeindicated by the line 1--1 of Figure 2; v

Figure 2 is a transverse sectio'n through the same, taken at 2-2 in Figure 1;

Figure 3 is a perspective elevation of the mandrel member employed in this embodiment;

Figure 4 is a perspective view of the contact member employed with this embodiment;

Figure 5 is a plan view of the device vshown in Figure 3, with the resistance and conductor elements in place;

Figure 6 is a longitudinal section through another ernbodiment of the invention, taken alo'ng the line 6-6 of Figure 7;

`Figure 7 is a transverse section, taken at 7-7 of Figure 6;

Figure 8 is a perspective view of the screw element of this embodiment; and

Figure 9 is a partially sectioned perspective view of the outer case employed with this last embodiment.

Attention is directed first to Figures l to 5, inclusive, wherein an instrument embodying the invention is designated in its entirety by the reference numeral 10, and is seen to co'mprise a tubular case 11, which may be of plastic, as shown, having a mandrel 12 rotatably connected therewith. The case 11 is internally threaded at 13 to form a helix, and is closed at one end by an end wall 14, having a central socket 15 that receives a journal 16 on the end of the mandrel.

The mandrel 12 comprises an end plate 20, having a` portion 21 of reduced diameter, which projects into the open end of the case 11. An annular groove 22 is provided in the reduced diameter portion 21, and seating in Y with an annular groove 71, which receives the end Of au,

Patented Mar. 1, 1960 portion 24, of rectangular cross section, projects lengthwise throughthe center of the tubular case 11 fro'm the portion 21, and is provided on its inner end with the journal 16 that is seated in the bearing socket 15 in the end wall 14.

The main body portion 24 of the mandrel has longitudinally extending

channels

25 and 26 formed inthe top and bottom surfaces thereof, and seated within the top channel 25 is a wire wound resistance element 30. The ends of the wire windings are attached to rivets 31, and joined to these rivets are

terminal wires

32 and 33. It will be noted that terminal wire 33 returns from the outer end of the element 30 to the end plate 20 alongside the element on a shelf 34.

Slidably mounted upon the mandrel 12 is a slider, or carrier 35 having a rectangular opening 36 extending there through to receive the main body po'rtion 24 of the mandrel. The outer portion of the carrier 35 is generally cylindrical, and is provided with a male thread 40 which is adapted to engage the threads 13 on the inside of the case 11. An end plate 41 is attached to one end of the carrier 35, and projecting axially therefrom is a spring Contact arm 42, the outer end of which wipes o'n the top edge of the resistance element 30.

Also projecting upwardly from the bottom portion of the end plate 41 into the bottom channel 26 of the mandrel is a tab 43, which is connected to one end'of `a flexible, extensible coil spring 44, which serves as an electrical return means from the contact arm 42 to an external terminal. The other end of the spring 44 is attached to a third terminal Wire 45 extending through a hole in the end plate 2t).v

Thus, when the case 11 is turned with respect to the mandrel, the carrier 35 is caused to move lengthwise along the resistance element ,30 by the

threads

13, 40; the said carrier being held against turning by the sliding engage'rnent of the flat sides of the' opening 36 with the therein, through which terminal wires 54, 55 and 56l Formed in the inside surface of the cylindrical pass. case is a longitudinally extending groove 60, which serves to guide the slider, or carrier 61 and prevent the ysame from rotating. l

Projecting from the inner side of the yend wall 52 con centric with the inside surface of the cylindrical case 50 is a semi-cylindrical supporting member 62 having two parallel, longitudinally extending

grooves

63 and 64 formed in the at top surface thereof. Seated within groove 63 is a wire-Wound resistance element 65; while groove 64 has a U-shaped conductor strip 66 seatedl therein, which serves as an electrical return means. Terminal Wires 54 and 56 are connected to the windings of the resistance element 65 at opposite ends thereof, while wire 55 is connected to the conducto'r strip 66.

The tubular screw element 51 is inserted into the open end of the cylindrical case 50, and is sized to tit loosely.

within the space between the inner wall of the case and the cylindrical outer surface of the supporting member 62. The outer end of the screw element 51 projects beyond the end of the case 50, and this projecting portion is enlarged in diameter to provide a knob 70. Closely adjacent the knob 70, the tubular element 51 is provided pin 72 projecting inwardly from the case 50, so as to hold the members 59, 51 against endwise separation, While permitting free rotatio'n relative to one another.

Thetubular element 51 has a helical groove or slot 73 formed therein, which extends `for the greater part of the length of the element. A pin 74 projecting upwardly from the top vof the carrier 6l, passes through the helical slot 73 of the tubular element 5l, and its end is slidably received within the longitudinally extending groove 60 in the cylindrical case 50.

The slider, or carrier 61 may have the form shown in Figure 7, wherein its cross sectional shape is the segment of a circle, with the cylindrical top surface thereof fitted to the inside surface of the-tubular element 51. Attached to the at bottom surface of the carrier is a U- shaped spring contact 75, one arm 76 of which wipes on the resistance element 65, while the other arm 77 wipes on the conductor strip 66.

From the foregoing description, it will be understood by thoseskilled in the art that rotation of the tubular screw element 51 relative to the cylindrical case 56 causes the carrier 61 to be shifted lengthwise of the resistance element 65 and conductor strip 66, owing to camming effect of the helical slot 73 on the pin 74. The carrier `61 is, of coulse, kept from turningwith vthe screw element 50 bythe slidingengagement of the Vpin 74 in the groove 60.

While I have shown and described in considerable-detail two selectedembodiments .of the invention, it will be understood by those skilledin the art that these are merely illustrative of the principles of the invention, and various changes maybe made in the shape and arrangement or disposition of the several parts without departing from the broad scope of the invention, as dened in the following claims.

I claim:

l. A variable resistor comprising: a tubular case; a female thread in said case; a slider having a male thread engaging saidfemale thread; a non-round opening in said slider; a mounting member insaid case and having a matching non-round cross section; said slider being slidably mounted on said mounting; a resistance element secured on said mounting on one side thereof; contact means carried by said slider having a contact arm engaging said resistance element and means carriedrby said case and said mounting preventing relative longitudinal movement thereof .but permittingrrelative rotation `thereof whereby said spring contact arm is carried to travel over `said element.

2. .A variable resistor, comprising a body made up of two relativelyrotatable parts, one of said parts being hollow and having a helicalfthread formed thereon, and the other-part having a projecting kportionextending -into the hollow lcenter ofsaidone part, parallel to the longitudinal axis thereof, a resistance element mounted on said projecting portion, and a slider movable along the lengthlof said projecting -portion and having a `contact wiping on .said resistance element, said sliderbeing engaged-by saidhelical thread .and beingmovablethereby whensaid body .parts are rotated with respect to' one another.

3. A var iable resistor comprising a body made up of a stationarymember. and Va `rotatable sleeve member vhaving aninternal thread formed thereon; a projection on said stationary member extendingparallel to the axis of'said rotatablesleevememben said projection having a nonround cross section, a resistance element mounted'on said projection, a sliderslidably mounted on said projectionand restrained thereby against rotation, said slider havingan external thread coacting with said internal thread onsaid sleevememben'whereby the slider is moved lengthwise of -said projection when said sleeve member is rotated,` and a contact on said slider engaging said resistance element. Y

4.1 Avariable resistor comprising a generally cylindrical member having ahelixformed thereon, aresistance element mounted within said cylindrical member generally parallel to the axis thereof, a carrier mounted within said cylindrical member and having a contact wiping on said resistance element, means on said carrier engaging said helix whereby rotation of said cylindrical member with respect to said resistance element causes said carrier t0 be moved lengthwise along said element, said carrier being restrained against rotation with said cylindrical member, and electrical return means from said contact to an external terminal means.

5. A variable resistor comprising a body made up of two relatively rotatable members, one of said members having a helix formed thereon, a resistance element mounted on the other of said members generally parallel to the longitudinal axis thereof, a carrier movable lengthwise of said resistance element and having a contact wiping thereon, means restraining said carrier against rotation while permitting free movement thereof along the length-of said resistance element, means on said carrier engaging saidhelix'whereby rotation of said one member with respect to Vsaid other member causes said carrier tomove along said element,and electrical return means from said contact to an external terminal means.

6. A variable resistor comprising a body made up of two relatively rotatable members, one of said members havingga helix formed thereon, a resistance element mounted onthe other of said members generally parallel to the longitudinal 'axis thereof, a carrier movable lengthwise of said resistance element and having a contact wiping thereon, said carrier having apart slidably engaging said other member-so as to restrain it from turning while permitting free movement thereof along the length of Said resistance element, said carrier being operatively engaged by said helix whereby rotation of said one -member with respect to said other member causes said carrier to move along said element, and electrical return means from said contact to an external terminal means.

7. A` variable resistor comprising, in combination, a body member having a resistance element mounted thereon, a slidable carrier having a contact wiping on said resistance element, a tubular member rotatably mounted on said body member and enclosing said carrier and said resistance element, said carrier being restrained against rotation relative to said body member vwhile permitted free sliding movement with respect thereto, and means operatively connecting saidcarrier with said rotatable tubular member to shift the carrier lengthwise along said resistance element as saidtubular member is rotated with respect to said body member.

V8. A variable resistor as recited in claim 5 lwherein said one member comprises a hollow cylinder,lthe helix formed onrsaid one of said members comprises a helical slot through the walls of said hollow cylinder, said means 0n said carrierengaging-said helix comprises a pin extending through said helical slot, said other of said relativelyrotatable memberscomprises ahollow cylinder having an end wall, a projecting portion extendingfrom said end wallinto ythe cavity ofrsaid cylinder-and being spaced sufficiently from-the sideszthereof to-enable said one member to be linserted therein, said resistance .winding being mounted yonsaid projection, said means restraining said carrier against rotation while permitting free movement thereof lalong'the length of said .resistance element comprises a .longitudinal groove in .said other of said relatively rotatable members into which said pin extends, and said electrical return means from saidcontact-to an external terminal means includes anelongated conductor mounted parallel to said resistance winding on said projection, and-a second contact carried by said carrier and wipingron,saidconducton said second contact being `electrically connected .to said Contact wiping on said resistance.

9. A variable resistor as recited in claim 6 wherein said one of lsaid members having a helix formed thereon comprises ahollow cylinder with said helix being in the form Qf'a slot, said other of said two relatively rotatable members also comprises a hollow cylinder within which said tirst hollow member lits, said other of said two relatively rotatable members including means for supporting said resistance element within said one of said members, said other of said two relatively rotatable members including a slot extending parallel to its longitudinal axis, and said part of said carrier slidably engaging said other member so as to restrain itvfrom turning While permitting free movement thereof along the length of said resistance element comprises a post on said carrier extending through said helical slot into said groove.

l0. A variable resistor as recited in claim'6 wherein said electrical return means includes an elongated conduc- 6 tor means for mounting said elongated conductor on the other of said members parallel to said resistance element, a second contact carrier by said carrier for wiping on said conductor, said second contact being electrically connected to said contact wiping on said resistance.

References Cited in the file of this patent UNITED STATES PATENTS 2,523,896 Bartolomei Sept. 26, 1950 2,704,860 Graybeal et al May 22, 1955 2,714,147 Reid -1. July 26, 1955 2,769,073 Gintovt 4.---., Oct. 30, 1956