Potentiometer
FIELD OF THE INVENTION 
     This is a continuation application from application Ser. No. 587,170 filed Mar. 7, 1984, now abandoned. 
    
    
     The present invention relates to a potentiometer which can be used for measurement of angles, and so forth. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to provide a potentiometer which is made up of a small number of components, easy to assemble, and economical from an overall point of view. 
     This object is accomplished in accordance with the teachings of the present invention by providing a potentiometer which comprises an enclosure made of insulating material, a positioning portion in the enclosure for receiving and positioning a resistance base plate, a recess formed in the enclosure near the positioning portion for receiving the shaft portion of a sliding member, the recess extending perpendicular to the contact surface of the base plate, and a slider formed on the sliding member and brought into contact with the contact surface of the base plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of a potentiometer according to the present invention. 
     FIG. 2 is a cross-sectional view taken on the line B--B of FIG. 1; 
     FIG. 3 is a cross-sectional view taken on the line C--C of FIG. 1; 
     FIG. 4 (a) is a side elevation of the resistance base plate of the potentiometer shown in FIG. 1; 
     FIG. 4 (b) is a front elevation of the base plate shown in FIG. 4 (a); 
     FIG. 5 is a side elevation of the potentiometer of FIG. 1 as viewed in the direction indicated by arrows A; 
     FIG. 6 is a perspective view of the sliding member of the potentiometer shown in FIG. 1; and 
     FIGS. 7 (a)-7 (d) are views for illustrating the manner in which the potentiometer of FIG. 1 is assembled. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to FIGS. 1 and 2, a embodying the concept of the present invention has a disklike cover 1 and an enclosure 4 below the cover 1. The cover 1 and the enclosure 4 are integrally produced from insulating synthetic resin by molding. A bulge 1b is formed on the top of the cover 1 and is provided with a recess 1d having a bottom 1f, in which a rectangular hole 1e is formed to receive a resistance base plate 5 (described later). Two pairs of projections 1c are formed on the bulge 1b so as to surround the recess 1d, each pair of the projections being disposed in opposed relation to each other. The top surface of each projection 1c has a tapered portion 1g. The projections 1c and the tapered portions 1g act to facilitate anchoring of a harness 2 which ensheathes lead wires 3 connected to the resistance base plate (described later) 5. According to the purposes for which the present rheostat is used, it is possible to bend and insert the lead wires 3 between those of the projections 1c which lie in a desired direction to ensure that the wires 3 extend in the desired direction. 
     The substantially boxlike enclosure 4 integral with the cover 1 has a flat upper surface 4a, which is provided with projections 4b and 4c substantially at the center and the left lower end thereof, respectively. The ends 4l and 4m of the protrusions 4b and 4c, respectively, are inclined in reverse directions. A projection 4d extending parallel to the projection 4c is a reinforcing rib. As shown in FIG. 3, the enclosure 4 is centrally provided with a cavity 4e which is in communication with the aforementioned rectangular hole 1e in the cover 1. The lowermost portion of the enclosure 4 opens to the outside through the cavity 4e. A side portion 4f is disposed on the opposite and lower side of the cavity 4e from the upper surface 4a of the enclosure 4. The side portion 4f has an end portion provided with a portion 4g which sinks and tapers off outwardly as shown in FIG. 5. The enclosure further has a bottom portion 4h and another side portion 4i. The opposed inner walls of the side portions 4f and 4i are each provided with a groove 4j to guide the resistance base plate 5 (described later) into the enclosure 4 and to determines the position at which the plate 5 is inserted. 
     The aforementioned resistance base plate 5 is fabricated from ceramic and has a plate portion 5a that has a contact surface 5g at its upper surface. A resistance member 5d and a pair of electrodes 5e, on which a slider (described later) making a sliding movement, are formed on the contact surface 5g by a known process. The lead wires 3 which are connected to the resistance member 5d and to the electrodes 5e, 5f by means of soldering as indicated by numeral 8 are attached to a terminal 5b. the base plate 5 is formed with a notch 5c which distinguishes the terminal 5b from the plate portion 5a that is different in dimension from the terminal 5b. In particular, the width of the terminal 5b is made larger than that of the plate portion 5a, and the width of the rectangular hole 1e in the cover 1, in which the plate 5 is inserted, is so large as to allow insertion of the plate portion 5a of the base plate 5 but small enough to inhibit insertion of the terminal 5b. 
     A sliding member 6 is rotatably mounted in the cavity 4e in the enclosure 4 in the manner as described later. The member 6 has a slider support 6a and a driver portion 6b. A lever 7 made of an aluminum rod has a curved end portion 7a which comes into contact with the driver portion 6b of the sliding member 6. The other end portion 7b is coupled to an object (not shown) whose angular displacement is to be measured. 
     The manner in which the foregoing components are assembled and their operation are hereinafter described. First, the resistance base plate 5 to which the harness is attached as shown in FIG. 4 is inserted into the cavity 4e in the enclosure 4 through the rectangular hole 1e formed in the bottom portion 1f of the cover 1 as shown in FIG. 2 and through the guide groove 4j. Then, as shown in FIG. 5, the harness 2 is fitly inserted between one pair of the protrusions 1c and is brought ut. Thereafter, the recess 1d in the cover 1 is sealed off together with the harness 2 with adhesive 9, and the base plate 5 is mounted to the enclosure 4. As shown in FIG. 6, the sliding member 6 comprises the slider support 6a shaped like a sector, the driver portion 6b protruding upwards from the support 6a, and a hollow shaft portion 6c, all of which are formed integrally from lead by die casting. A slider 10 has a contact element 10a which is curved so that it may readily ride over the tapering portion 4g, and the slider 10 is firmly secured to the support 6a by crimping or similar means. The driver portion 6b has an opening 6d, a hole 6f, and a tapering portion 6e which sinks toward the hole 6f. As shown in FIG. 7 (a), the side portion 4f of the enclosure 4 is provided with a recess 4k that extends perpendicular to the plane of the base plate 5. The sliding member 6 is mounted to the enclosure 4 such that the shaft portion 6c is rotatably inserted in the recess 4k. Subsequently, the support 6a is pressed into the cavity 4e in the enclosure 4 while rotating the sliding member 6 in the direction indicated by the arrow A as shown in FIG. 7 (b). Thus, the protrusion 6g and the curved contact element 10a of the sliding member 6 ride over the tapering portion 4g formed at the end of the side portion 4f of the enclosure, and then they are received in the cavity 4e in the enclosure 4 without introducing any problems. As a result, as shown in FIG. 7 (c), the contact element 10a of the slider 10 mounted to the underside of the sliding member 6 comes into resilient contact with the electrodes 5e and 5f on the base plate 5. Then, the bent end portion 7a of the lever 7 is inserted into the hole 6f in the driver portion 6b of the sliding member 6 while guided by the tapering portion 6e. An anchoring ring 11 is then anchored to the front end of the bent end portion 7a so that the lever 7 may interlock with the sliding member 6, thus completing the assemblying operation. 
     The potentiometer constructed as described above is operated as follows. The device is coupled to an object whose angular displacement, for example, is to be measured. Rotation of this object turns the lever 7 together with the sliding member 6 about the shaft portion 6c in the cavity 4e in the enclosure. This causes the slider 11 to slide on the electrodes 5e and 5f on the base plate 5, resulting in a change in the resistance value of the resistance member 5d. This change can be detected by an electrical means to measure the angular displacement of the object. In this case, the lever 7 extending over the sliding member 6 rotates between the inclines 4l and 4m of the ends of the projections 4c and 4b, respectively. Thus, the angle through which the sliding member 6 can rotate is limited. 
     As thus far described, the novel potentiometer according to the invention is made up of a small number of components, easy to assemble, and hence economical from an overall point of view. 
     While the described embodiment represents the preferred form of the present invention, it is to be understood that various modifications and changes will occur to those skilled in the art without departing from the spirit of the invention. The scope of the invention is therefore to be determined solely by the appended claims.