US1535898A - Rheostat - Google Patents

Description

L Patented A131128, 1925.

UNITED STATES PATENT OFFICE.

RAY MONTAGUE CAMP, OF DAYTON'A, FLORIDA.

RHEosTA'r.

Application filed June 23, 1923. Serial No. 647,360.

T o all whom t may concern:

ABe it known that I, RAY M. CAMP, a citi-l zen of the United States, and a resident of Daytona, in the county of Volusia and State of Florida, have invented a new and Improved Rheostat, of whichthe following is a full, clear, and exact description.

This invention relates to a rheostat, and has for an object the provision of a rheostat in which very line adjustments are easily effected.

Another object concerns the provision of a rheostat which is an improvement over the form of rheostat shown in my copending application, Serial No. 640267, filed May 19, 1923, entitled Rheostat A further object concerns the provision of means whereby a minimum number of simply constructed parts are used so that the strength and durability are increased and the liability to get out of repair is reduced to a minimum.

The invention is illustrated in the drawin s, of which l 4igure 1 is a side elevation of the device;

Fig. 2 is a section taken on the line 2 2 of Fig. 1;

Fig. 3 is a section taken on the line 3-3 of Fig. 2; and

Fig. 4 is a perspective of the contact shoe.

The form of the invention shown in the drawings is a preferred form, although it is understood that modiiications in the construction 'and arrangement of the parts and in thel character of the materials used may be adopted without departing from the spirit of the invention.

The invention in general includes preferably a cylindrical or rotatable support of insulating material, preferably provided with a spiral groove in its surface, 'said groove having preferably a rectangular cross section in which is laid a resistance wire, preferably of ribbon form and continuous. Over this support and ribbon is placed a conducting nut, preferably threaded andy held thereon, which as the support is rotated will move therealong in contact with the ribbon in either direction, depending upon the direc-tion of rotation of the support.l f

This nut isprovided with a connection which makes contact with the outside circuit, and also affords means for guiding the nut to hold it from rotation. The support is held in a frame from which it may be easily di'smounted. Connected with the nut but easily removable therefrom is a contact shoe formed of resilient material adapted to extend into the groove or thread on either or both' sides of the nut to make a more perfect contact with the ribbon.

The invention as illustrated in the drawings includes a frame having a front plate 1 and a rear spring plate 2 connected by a cylindrical portion 3 containing a body of insulating material 4a. This cylindrical portion is cut away throughout most of its length on the upper side thereof, and the insulating body portion 4 is provided with a groove 4 along the bottom of which a contact strip or track 5 is disposed. This track at one end, nearthe front wall, is provided with a connection 6 leading to a binding post 7 mounted on the plate 1 but separated therefrom electrically by insulation 8.

Mounted also on the front wall or plate 1 is a second binding post 9 which, however, is in electrical contact with the plate 1 and through the cylindricalfportion 3 and the rear spring plate 2 connects with the other parts in circuit, as hereinafter to be described. The rear plate 2 is provided with a depressed portion 12 in which fits 'a tapered or inclined nut or screw 13 which 1s embedded in the end of an insulating body portion 14, preferably cylindrical. This body portion is provided on its surface with a spiral thread or groove of rectangular cross section in which is held a preferably continuous resistance ribbon 15, one end of which is embedded in the body portion and the other end of which is connected to the screw 13.

The other end of the support or cylindrical body portion 14 is provided with al stem 16 passlng through the front plate 1, and on its other end carries a knob 17. Surrounding the cylindrical body portion is a metallic conducting nut 18, preferably split at 19 and held together by a spring 20: This nut is adapted to surround the ribbon and the support and travel along the ribbon in one direction or another as the stem 16 is rotated in one direction or another. Dependent from the lower portion of the nut is a contact finger 21. The contact linger 21 bears on the track 5 acting as a means for conducting the current to said track and also to prevent rotation of the nut 18 which naturally tends to rotate whenever the body portion 14 is rotated.

Therefore, the slightest rotation of the knob 17 will vary the amount of wire which is in contact between the end 18 andthe screw 13.. A plug 22 is mounted in a suitable groove or aperture between the split end of the nut 18, and to this plug is connected a strip of flexible material 23, preferably resilient or spring metal in the form of a shoe extendig laterally from said plug and depending downwardly to lie in a groove or thread in thesupport 14 and contacting with the ribbon therein. The upper surface of the plug is provided with a groove 24 in which the spring 20 lies, this spring tending, therefore, to hold the plug in place. B removing the spring from bearing on t e`plug, the plug can be removed and with it the contact shoe 23. The

. nut on its lower .portion is provided with a stop arm 25 so that as the nut travels Y towards the rear of the support 14 the stop arm 25 will engage the rear plate 2 to prevent or make more diflicult further rearward movement .of the nut.

By using the ribbon the warping, caused by expansion, is up and down, so that distortion of one coil cannot affect the other. The coil spring on the nut now performs three distinct functions: lirst, holding the expanding nut on the insulated body portion 14; second, making contact on the plug 24; also forcing the plug and contact shoe down, making sure contact with the ribbon. The shoe is adapted to travel just ahead of the nut so that in case of expansion of the ribbon a final adjustment can be o btained, since, should the ribbon come in contact with the nut' it will have no efect. It is also to be noted that as the nut travels to the end of the support 14 the stop arm 25 will engage the spring plate 2 and if pushed too far will break the circuit between the plate 2 and the screw 13 and thereby act as(A a switch.

The electrical circuit through the apparatus is as follows: From the binding post 9 to the front plate 1, cylinder 3, rear platel 2, screw 13, wire 15 to the shoe 23, plug 22, spring 20, nut 18, contact finger 21, track 5, connection 6, and binding post 7. The ends. of the spring 20l maybe hooked over ears such as 2Oa formed on the sides of the nut 18. That portion of the wire 15 which lies between the nut and the screw 13 is the portion of the resistance which is in circuit.

It will be apparent from the description of the operation that very small quantities of wire can be drawn into or out of the circuit by a simple manipulation of the invention. Because of the fact that the pitch of the thread or groove in the body portion 14 is generally very fine this sensitiveness and line adjustment can be easily achieved. A firm and sure contact with the ribbon is at all times insured regardless of any expansion of the ribbon which vlmay take place. Furthermore, too greatmovement of the nut toward the rear will automatically causeA the breaking of the circuit. The contact shoe is easily removable for repair and adjustment, the entire apparatus, including the relatively small number of simple parts making the simplicity of the entire device a matter of fact.

What I claim is l. A rheostat including an insulating sup- Y port having a spiral groove in itssurface, a threaded conducting nut embracing4 said support, a conductor in said groove, a spring plate supporting and connected to the rear end of the support, and a stop on the nut to engage said plate when the nut has'traveled a delinite distance to the rear of the support whereby further movement of the nut will move the spring plate away fromt-he support to break the connection therebetween.

2. A rheostat which includes an insulating support portion having a spira-l groove in its surface, a threaded conducting' nut embracto hold it in the aperture, a contact shoe connected to said plug and dependent therefrom into the groove adjacent the traveler nut, and a conductor in said groove withvwhiclisaid shoe makes contact.

RAY MONTAGUE CAMP.

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