Patent Publication Number: US-4647731-A

Title: Transformer crankshaft load selector

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a load selector for step transformers. 
     2. Related Art 
     In this type of apparatus, the different loads comprising the fixed contacts are electrically connected to the outputs of the steps of the transformer. These different loads are arranged, at a sufficient dielectric distance from one another, on the internal wall of an insulating cylinder, acting as an oil receptacle, on the interior of which are arranged movable contacts. In accordance with the voltage of the steps, there corresponds a dielectric distance between adjacent fixed contacts. As a result, for one type of apparatus, the number of fixed contacts arranged on the insulating cylinder is proportional to the diameter of the cylinder. In these apparatuses, increasing the number of fixed contacts necessarily leads to an increase in the diameter of the insulating tube. Generally, these diameter variations entail important modifications of the elements comprising the apparatus and increasing the number of different pieces which must be maintained in stock. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     An object of the present invention is to use a maximum number of identical elements to cover different classes of apparatus and thus reduce the costs of fabrication and maintenance of stock. This goal is attained by judiciously modifying the geometry of a limited number of elements. 
     The invention essentially comprises utilizing, at the level of the selector, on one hand, a crankshaft permitting keeping the same commutator modules, and on the other hand adaptor rings for connecting the oil sump and housing of the drive mechanism to an insulating cylinder of greater diameter. 
     A load selector has an insulating cylinder, provided with fixed seletor contacts and common point rings, in the interior of which is displaced a drive crankshaft on which are supported commutator modules. The drive crankshaft includes a male coupling element, a female coupling element associated with an upper crank, an off-center tube and a lower crank. A rolling mechanism serves as a lower bearing, and a rolling mechanism serves as the upper bearing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other objects of the invention will be greater appreciated from the following description and accompanying drawing wherein: 
     The FIGURE is a sectional view of the assembly of a load selector. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the FIGURE, the load selector comprises an insulating cylinder 1 having on the periphery of its interior wall a plurality of fixed selector contacts 2 and common point rings 3 which connect with the steps of the three phases of the transformer. The fixed contacts of an inverter 4 are shown in the upper part of the insulating cylinder 1. 
     The fixed contacts of the selector 2 and the common point rings 3 cooperate for each phase with a respective selector commutator module 5. 
     The commutator selector modules 5 are supported on an insulating tube 6 comprising the offset part of a crankshaft 7. 
     This drive crankshaft 7 comprises a male coupling element 8, a female coupling element 9 associated with an upper crank 10, an insulating tube 6, hereinafter termed the off-center insulating tube, and a lower crank 11 joined at a conical extremity 12 through a lower bearing 13. 
     The drive crankshaft 17 is centered and driven at its upper part by the male coupling element 8 turning in an upper bearing 14, and supported by a side plate 15 of a drive housing 16 enclosing a drive mechanism 17 (driven by gearing mechanism 171 and a pair of shafts 172 and 173) which actuates the male coupling element 8. The cross-section of the male coupling element 8 is of a non-circular form and is engaged in a recess of the same configuration in the female coupling element 9. The conical extremity 12 is centered by the interposition of a socket 18 on a solid bearing support 19 of the sump 20 which serves to receive oil. This sump 20, designed for an insulating tube of smaller diameter, is joined with the insulating cylinder 1 by a lower connecting ring 21. 
     A siphon conduit may be provided traversing the crankshaft 7 and permitting the aspiration of oil from the receptacle. This conduit is accessible from the exterior by a connection tube 22 which extends across the drive mechanism 17 and terminating in a drain tube 23 arranged vertically in an axial bore, of greater diameter, in the male coupling element 8 and maintained centered by a fluid-tight seal 24 placed in the female coupling element 9. With the exception of the friction exerted by the seal 24, the drain tube 23 is supported with no mechanical effort. The drain tube 23 leads to a crank or angled conduit 25, internal to the female coupling element 9 and in the upper crank 10. The crank conduit 25 may thus be connected to a siphon tube 26 maintained on an axis 27 of the off-center insulating tube 6 by the upper crank 10 and the lower crank 11. The lower extremity of the siphon tube 26 empties into a hole formed in the lower crank 11 along the axis 27 to be used as an adjustment 28. 
     A pair of joint seals 29 are provided on the two extremities of the siphon tube 26. 
     The housing 16, designed for an insulating tube of smaller diameter, is joined to the insulating cylinder 1 by an upper connecting ring 30. The housing 16 has around its periphery a shoulder 31 which connects to the tranformer tank. 
     The female coupling 9 supports at its base a bearing 32 which is fitted on a plate 33 fixedly connected to an inverted insulating tube 34 on which are mounted the movable inverter contacts 35. The plate 33 is provided with an opening 36 in which is engaged a driving lug 37 actuated by the drive mechanism 17. The drive mechanism 17 actuates, in an independent manner, the inverter by the intermediary of the driving lug 37 and the selector by the intermediary of the male coupling 8. 
     The insulating cylinder 1, together with the cup 20, the lower connecting ring 21, the housing 16 provided with a cover 38 and the upper connecting ring 30, serves as the oil receptacle for the assembly of the apparatus. 
     The fluid-tightness of this oil receptacle is assured by a plurality of joints 39, 40, 41, 42, 43 arranged in the grooves made respectively in the lower connecting ring 21, the upper connecting ring 30 and the cover 38. 
     The insulating tube 1, carrying the fixed inverter contacts 4, the fixed selector contacts 2 and the common point ring 3, are concentric around the same axis 44, termed the axis of the apparatus 44. 
     The off-center insulating tube 6, carrying the selector control modules 5 has an axis of symmetry of revolution, termed the axis of the crank part 27. This off-center insulating tube constitutes the angled part of the crankshaft 7 which rests on the lower bearing 13 and on the upper bearing and is concentric with the axis of the apparatus 44. 
     The upper part of the off-center insulating tube 6 is displaced to the interior of the inverter insulating tube 34. According to the class of apparatus, the overlapping part of the off-center insulating tube 6 and of the inverted insulating tube 34 is more or less important accordng to the distance to be arranged between the fixed contacts of the inverter and the plate 33. 
     The commutator modules of the selector 5 are normally mounted on the off-center insulating tube 6 according to the generatrix contained in the plane formed by the axis of the apparatus 44 and the axis of the crank part 27 at right angles with the fixed selector contacts 2. Nevertheless, to adapt the same commutator modules of the selector 5 to a greater range of diameters of the insulating tube 1, these modules may be mounted in a position deviating more or less from the previously defined normal position. The same result would therefore be obtained by the circular form of the cross-section of the off-center insulating cylinder 6 by an elliptical form and while arranging the adjustable steps in rotation on the lower crank 11 and the upper crank 10. The lower connecting ring 21 and the upper connecting ring 30 are preferably identical and of an appropriate form for being easily placed on the desired exterior diameter. 
     In this illustrated example the resistances of the passage, not shown, are arranged around the off-center insulating tube 6 in a molded passageway, extending in the free space situated on the lower part of each commutator module of selector 5, and shaped to support the movable contact being displaced opposite each common point ring 3. 
     When the commutator modules of the selector 5 are at the potential of a neutral point, the off-center insulating tube 6 may be replaced over a part of its length by a metallic tube. 
     While one embodiment of the invention has been described, it will be understood that is capable of further modificaton, and this application is intended to cover any variations, uses, or adaptations of the invention, following in general the principles of the invention and including such departures from the present disclosure as to come within knowledge or customary practice in the art to which the invention pertains, and as may be applied to the essential features hereinbefore set forth and falling within the scope of the invention or the limits of the appended claims.