US1739942A

US1739942A - Rheostat

Info

Publication number: US1739942A
Application number: US80402A
Authority: US
Inventors: Ernest A Bohlman
Original assignee: Kellogg Switchboard and Supply Co
Current assignee: Kellogg Switchboard and Supply Co
Priority date: 1926-01-11
Filing date: 1926-01-11
Publication date: 1929-12-17
Anticipated expiration: 1946-12-17

Description

y tegrally formed means, which in addition tol Patented Dec. 17'1'929 ERNEST' -A.'Bo1=ILMAN, or'oIIIoAGo, ILLINoIs, AssIGNon 'ro IIELLoGGsWIfrcHBoAnn AND SUPPLY coMrANYyoF CHICAGO. ILLINOIS, aV CORPORATION or ILLINOIS RIInosrA'r Application ledl'an'uary 11, 1926. Serial 110.186,402. n

My invention relates to rheostats for varying theresistance 'in an electricalciri cuit and [is adaptedparticularly for use in controlling the current in the filament cir-.-k

cuits of electrontubes. Anobject of my invention is to provide a rheostat that `is simple in constructionbut very durable and reliable in is operation. y A feature of my invention is the provision of a novel wiper arrangement in which the wiper, which engages the convolutions ofthe resistance unit, is provided with inf providing yi'rictional means for maintaining the wiper in any of its adjusted positions, forms a wiping contact, positive in itsoper-y ation, between. the wiper and the conducting member VVwhich electrically connects the wiper with one terminal of the rheostat. This construction provides a positive connection betweenfthe Wiper and the conducting member and assuresa positive electrical wiping contact.

l The above and other features will be Amore vparticularly pointed out in the ensuing specifcation'and the appended claims. For

a more complete understandingof'the same reference may behad to the accompanying drawing Vin which like reference characters denote like parts and` in which; Y Fig.v 1 is a. front view of the rheostat of my invention.

Fig. 2 isa right side view of Fig. `1. Fig 3 is a rear view of the rheostatof my invention, illustrating it in one of its actuated positions.

, Fig. 4 is a sectional view 4 4. of Fig. 3.. Y Referring now more in detail `to my invention, as illustrated in the accompanying 'along the line drawing, it comprises aresistance unit or4 coil 2,l `which may be :of any predetermined ohmic resistance,"woundpby a suitableA machineup'on a flatwstrip of insulating matef rial The ends of the resistance unit `f2 are held in place by being passedthrough suitable orifices in the strip 3. After Vthe coil 2 has beenvwound upon the insulating material 3, theV Whole isformed into a substantially ring shaped member R by means of a suitable forming operation. o f

The bakelite or porcelain basel is providedk with a peripheral'rim 23 which forms 6 and 7l toclamp thev parts in position.` The terminals 2O .and 21 are for the usual solderedconnections and the

nuts

16 and 17 provide' means for clamping conductors to the screws. 6 and 7 ywhenl the terminals 2O yand 21 vare not used. One endl 22 of the` resistance coil 2 islsecured to the screw 6 other end 22 of coil 2 is secured to the strip 3 by passing the same through an orifice .provided for this purpose inthe end 8 of theA insulating strip 3. v

4.The screw7'passes throughy the base of yan arm 24 Aof conducting materialwhich terminates `at itsopposite end in ay circular plate 25. Plate25 has acentral orifice of a size to fit loosely around a shaft 31 which,

extends through a ferrule 26 which rests in The ferrule 26 has'itsl opposite ends upset The part of the shaft 31 which` extends through the `ierrule 26 is reduced to provide a shoulder which restsagainst the turned up end 30 of the ferrule 26 and prevents inward longitudinal movement of the shaft 31. A

knob K is attached tothe end of the shaft" '311,:rotatingthe shaft and its' associatedparts.v

For a detailed description `of the method `used to support the knoblK reference may be had to Patent N o. 1,678,524, issued to Emil `lrNielsen, July 24, 1928. The other end ot the shaft 31V extends beyond the face 10 of the yto which is joined the Vterminal 20." The `a suitable orifice in the vhub 1 formed in-` i x 'teg'rally with base 1.

V" against the face 10 oftheintegrally formed Ahuh 1. and the facek 12 of the base 1 as shown int grally formed hub for purposes hereinportion 33 which has its edges a and b slightly turned up so as to facilitate its movement across the turns of wire which comprise the resistance unit 2. The Wiper 32 is so formed. as to provide a spring effect for gripping the convolutions of the coil 2, to assure a good contactual engagement 'between the end 33 .ofv the wiper 32 and the convolutions of the coil 2. An arm 34 a suitable size and material is secured to wiper 32 by the two depending legs c and E which are so spaced as to snugly receive the wiper 32 therebetween.

The wiper 32 is also provided with Yan integrally formed dished semi-circular portion 3,. the portion 32 and the arm 34 having suitable orifices of a size to lit over the reduced end portion 31 of the shaft 31, which is then spun over firmly to secure the wiper 32 and the arm 34 on the reduced end portion 3l.

The dished semi-circular portion 32 is split into sections e which are bent down in order to provide a better Contact with the circular plate 25ct the arm 24; thus providing' trictional means to hold the wiper 32 in any of its adjusted positions. The arm 24 is so formed that it has a tendency7 to spring away from the face 10 of hub 1'.; thus maintaining the circular portion 25 in good contactual engagement with the legs e of the wiper 32. The arm '2-1 electrically joins the Wiper 32 to the ter ninal 21 of the rheostat.

The porcelain or lbakelite base 1 is also provided with an integrally formed lug 40 which engages the panel to which it is mounted. An orilice 36 is provided as a means for `mounting the rlieostat and a mounting screw is inserted in the orifice 3G and a suitable orilice provided in the panel. A nut is then threaded on the screw and this serves to hold the rheostat in its proper posi'- tion upon the panel. An integrally formed lug 37 is provided on the porcelain base 1.to ac3 as a stop for the wiper. end 33 when in its normal or extreme advanced position. An insulating washer 38 is mounted between the end 8 o the strip R and the turned over portion of the connecting strip 24 to prevent the strip 2-l from contacting with the end of the winding on the strip R, and also to serve as a normal resting place for the Ywiper end 33.

Having described the apparatus which coniprises the rheostat, l will next give a description of its operation. When the Wiper end 33 rests on the insulating washer 38 the rheostat is in its normal or olf position and no current passes through the resistance coil 2. Vhen the linob K isturned the shaft 31 `rotates and with it the wiper arm 32, and the member 34, the flared end vof the Wiper arm 32 passing into engagement with the peripheral face of the resistance coil 2. This completes an electrical circuit from terminal 20 to terminal 2l by the way of screw 7, arm 24, circular plate 25, depending legs e, wiper 32, flared wiper end 33, resistance coil 2, screw 6 to terminal 20. As the wiper 32 is rotated the amount of resistance in the circuit is lessened by the wiper l32 reducing `the number of turns of wire on the resistance coil 2 between brush 33 and terminal 20 and consequently a larger amount et' current is allowed to pass through the circuit. The wiper 32 maybe rotated unti it reaches the end 22 ot the resistance coilv 2 where it comes in contact with the integrally formed shoulder 37 of the base 1. lVhen the wiper is in such a position practically none of the convolutions ot wire are in the circuit and the maximum amount of current is passing through the circuit.

W'hile I have described a particular embodiment of my invention it 1s to be understood that I, do not wish to be limited to the exact structure illustrated and described, but intend to cover all changes and modifications which come within the spirit and scope of the appended claims.

Having described my invention what I claim as new and desire to secure by Letters Patent is:

l. In a rheostat, a supporting base, a resistance element mounted on said base, a hub integral with said base, a shaft rotatably supported by said hub in said base, a wiper secured to said shaft by an upsetting operation and arranged to traverse said resist-ance element upon rotation of said shaft, said wiper having an enlarged portion comprising a plurality of dependinfr legs adjacent said shaft, a terminal on said base and a resilient arm having one end iXed to said base, the opposite end. of said arm being held {irmly in engagement with lthe depending legs of said wiper, said engaging portions of said arm and wiper being located on the same side of said hub, said arm electrically joining said wiper to said terminal and Preventing longitudinal movement of said shaft and also operating frictionally to retain said wiper in adjusted position due to the resiliency of said arm.

2. In a rheostat, a supporting base, a resistance element mounted on said base, a shaft rotatably supported by said base, a wiper secured to said shaft by an upsetting operation and arranged to traverse said resistance element upon rotation of said shaft, said wiper having an enlarged portion comprising a plurality of depending legs, a terminal on said base and a spring arm having one end `fixed to said base, the opposite end ot said arm being held by its resiliency firmly in engagement with the depending legs ofsaid wiper to prevent longitudinal movement of said shaft, said'arm and said wiper engaging each other on the same side ofsaid supporting base.

3; In a rlieostat, a supporting base` re-V sistance element mounted on said base, a shaft rotatably suppoited by said. base, a

Wiper fixed to said shaft by an upsetting operation and arranged to traverse said resistance element upon rotation of said shaft, said Wiper having an integrally formedenlarged portion comprising a plurality of depending legs,`a terminal on said base and an arm having one, end iXed to said base, the opposite end of said arm being held vresiliently in engagement with the depending legs of, said Wiper, said arin and said Wiper engaging each other on thesaine side of said supporting base, said arm ele'ctricallyvjoinf ing said Wiper to said terminal and also acting frictionally to holdsaid Wiper and shaft in their various adjustedvpositions, and serving as means to prevent V longitudinal movement of said shaft. y l 4 Y v,LIn a rheostata supporting base, are* sistance' element mounted on said base',a

kshaft rotatably supported by saidbase, a

Wiper secured to said shaft by an upsetting operation andarranged to traverse said resistance element upon rotation of said shaft, an offset portion on said wiper adjacent to said shaft comprising a plurality of depending legs, a terminal on said base and a spring arm having one end fixedV to saidbase, the

opposite end of said arm being held by its resiliency firmly in immediatel electrical engagement with said depending legs of said Wiper, said engaging portions of said Wiper and said arm being located on the saine side of said base'and said arm cooperating With said depending legs to prevent longitudinal movement of said shaft.

5. In a rlieostat, a supporting base, aresistance element mountedon said base, a shaft rotatably supported by 'said base, a Wiper secured to said shaft by an upsetting operation and arranged to traverse said resistance` acting frictionally to retain said Wiper Yin* its adjusted positions, said arm andwiper cooperating to prevent longitudinal movement of said shaft; v j' 5 i 6. In a rlieostat, a supporting base, a ring shapedA resistance elementv secured to said base, a terminal secured to said base, a hub integral with the base, a shaft rotatably mounted in said hub, a resilient conducting member having one end secured to said terminal and its other end loosely v4fitted on the said vsaidshaft having vareduced end portion, av

Wiper supportedvon said reduced portion by upsetting theend of 'said reduced portion,

said Wiper arranged to'traverse said resist-i ance elementl on rotationof said shaft, said `Wiper having an enlarged portion comprising a plurality of depending legs, said conducting member being resilientlyr held in immediate electrical engagement with the said Wiper,

said engaging portions of said armand Wiper being located on the same side ofV said hub ,l member and serving as means' to prevent longitudinal movement of said shaft.

, 7. In a rheostat, a supportingl base, av ring shaped resistance Velement secured at its ends to said base, a terminalsecured to said base, a hub integral WithA said bas`e,a shaft having a reduced end port-ion rotatably 'mounted in said hub, ,aresilient arm of conducting inaterial, one end of whichis secured to' said terminal and they other end of'which is loosely fitted about said shaft, a Wiper lhaving an en* ylarged portion comprising a plurality ofde-y `pending legs, said reduced end of said shaft beingspun over to secure said Wiper to said shaft, one end of said Wiper engaging said resistance coil, an arm secured to said reduced Aend of said shaft having depending legs which engage the said Wiper on opposite sides to assure the rotation of said Wiper, said re-r silient 'arm having an enlarged portion adapted to engage the said plurality of depending legs on said Wiper, said engaging portions of said resilient arm and Wiper being located. on the saine side of said hub.

8. Ina rheostat, a supporting base, a`ring shaped resistance element secured to said base, a'terininal secured to said base, a hub integral with said base,a sleeve extending through said hub and being self-sustained therein, a rotatable shaft having a reduced Wiper adapted to engage said resistance element and having an enlarged'portion comprising a plurality of split portions, said ref duced end of said shaft being upset to secure 'said Wiper to said shaft, and cause the saineV to rotate, an arm secured to said shaft having depending legs which engage said Wiper on opposite edges thereof to assure the rotation of said Wiper, said resilient arm and said split portions of said Wiper adapted to engage each other, said resiliency of said conducting inember maintaining contactual `engagement of l.said Wiper and saidv conducting member.

k9,' A deviceof the character described in-v end portion extending through saidy sleeve, a i resilientfconducting member having one of 'its ends secured to said terminal, and its i iic other end looselyy fitted around said shaft, a v

cluding a supporting base, a ring shaped resistance element secured to said hase, a terminal secured to said base, a hub integral With said base, a sleeve extending throughsaid hub and being self sustaining therein, a rotatable sha-ft extending through said Sleeve and having a reduced end portion, a spring arm of conducting material, one end ofwhich is fixed to Said base and the other end of which is enlarged and loosely fitted about said Shaft, a Wiper adapted to engage said resistance element, said reduced end of said shaft being Spun over to rigidly secure said wiper to said shaft, depending legs integrally formed with Said Wiper adapted to be engaged by the enlarged end of said arm which is interposed between Said depending legs of said Wiper and the hub portion of said base, said arm ovuerating electrically to join said Wiper to said terminal and also provide friction means Jfor n'aintztining said Wiper in any of its adj usted positions and for preventing longitudinal movement oi Said shaft.

In testimony whereof I have Signed this Speciieation.

ERNEST A. BOHLMAN.