US2904731A - Double current collector for dry disc rectifiers - Google Patents

Description

Sept. 15, 1959 s. E. BRAYSHAW 2,904,731

DOUBLE CURRENT COLLECTQR FOR DRY DISC RECTIFIERS Filed March 20, 1958 2 Sheets-Sheet 1 HlllllI IN VEN TOR. 5 TAN/E2 6'. 52A YSHA w p 1959 s. E. BRAYSHAW 2,904,731

DOUBLE CURRENT COLLECTOR FOR DRY DISC RECTIFIERS Filed Mar ch 20, 1958 4 2 Sheets$heet 2 Fig. .5

' I v INVENTOR. E 9. I W STAN/E2 E. BEA YSHAW H15 A rrozus Y Y United States Patent DOUBLE CURRENT COLLECTOR FOR DRY DISC RECTIFIERS Stanier E. Brayshaw, Indiana, Pa., assignor to Syntron Company, Homer City, Pa., a corporation of Delaware Application March 20, 1958, Serial No. 722,804

Claims. (Cl. 317-234) This invention relates generally to current collectors for dry disc rectifiers and more particularly to frusto conically shaped spring washer type current collectors.

The principal object of this invention is the provision of a dual spring washer current collector for dry disc rectificrs that engage the metallic electrode surface of the rectifier to collect the current therefrom. Dry disc rectifiers rely solely upon the metallic electrode to carry the current to the contact member or current collector. These current collectors provide only minimum surface contact which may be in annularly spaced points made by a sine wave type spring washer or annular concentric contacts made by a terraced frusto conical current collector. The latter provides two concentric annular line contacts which provides less contact area than when used as a single annular contact and the improvement is in the use of this single annular contact of a terraced Washer in combination with a smaller washer that provides substantially more contact area and is completely enclosed by the larger or outer washer.

Other objects and advantages appear hereinafter in the following description and claims.

The accompanying drawing show for the purpose of exemplification without limiting the invention or claims thereto certain practical embodiments of the invention wherein:

Fig. 1 is a sectional view showing a double spring current collecting washer engaging the dry disc rectifier stack.

Fig. 2 is a sectional view of the large washer when free.

Fig. 3 is a plan view of the large washer.

Fig. 4 is a sectional View of the small washer when free.

Fig. 5 is a plan view of the small washer.

Referring to the drawings, the rectifier comprises the stack as shown in Fig. 1 that is made up of a series of rectifier discs 1 which are preferably a metal base 2 with a selenium and alloy coating 3 on one side thereof. The rectifier coating is finished with a metallic electrode surface against which the current collector washers 4 and 5 engage. The washer 4 as shown in Figs. 2 and 3 is approximately .008 of an inch thick and is provided with a series of annular shoulders 6 and 7 which define the annular terraced sections 8 and 9 to form the annular land sections 10, 11 and 12. The land sections 10 and 11 are preferably disposed in parallel planes, whereas the land section 12 is preferably disposed at an angle of 82 from the axis of the hole indicated at 13 in the center of the washer. The washer 4 is substantially the same as the washer shown in the Smith Patent No. 2,656,495. The washer 5 as shown in Figs. 4 and 5 is provided with a shoulder 14 forming the terrace 15 that provides the annular land sections 16 and 17. The land section 16 is fiat and being normal to the axis of the washer passing through the hole 18. As shown in Fig. 4 the annular land section 17 is approximately 74 from the 2,904,731 Patented Sept. 15, 1959 axis of the hole 18 which is concentric to the'shoulder and land sections.

The land section 17 may be slotted as indicated by the radially disposed slots 20, making independent pressure segments 21.

The rectifier stack of Fig. 1 comprises the center mounting bolt 22 with the nut 23 that passes through the insulating sleeve 24 and is provided with the metal washers 25 at either end and the lock washer 26 under the nut.

At each end of the stack two insulating washers 27 and 28 fit over the insulating tube 24 and form the ends of the stack. A small insulating spacer washer 30 is placed inwardly of each of the large washers 28 after which is set the terminal members 31 which are spaced from the rectifier discs 1 by means of the metallic washer 32 which engages the under or base metal side of the first rectifier 1 and a similar washer 33 engages between the current collecting washers 4 and 5 at the opposite end of the stack and its corresponding terminal 31. Intermediate the semiconducting material 3 and the first annular surfaces 10 and 16 of the Washers 4 and 5 lies an insulating annular washer 34. Since there are three rectifier discs shown in this stack the under side of the second and third rectifiers is engaged by the large metallic washer 35, the opposite end of which engages the top of the annular surface 10 of the washers 4 of the first and second rectifier discs 1.

When the nut 23 is drawn tight to hold the assembly together the washers 4 and 5 are flexed as indicated in Fig. 1 from their normal position as shown in Figs. 2 and 4. It will be seen that the outer or covering washer 4 is spaced from the inner or smaller washer 5 and also protects the same when the rectifier is dipped after assembly in a paint which aids in closing and sealing the rectifier.

The relative size of the insulating spacer washers 34 determines the extent of the compression and flexing of the current collecting washers 4 and 5 and the length of the spacing Washers 35 determines the clearance between adjacent rectifier discs for the purpose of cooling the same.

When the inner and small washer 5 is provided with the radial slots 20 forming the sections 21 the ambient air within the chamber illustrated at 36 may be circulated to and from inner chamber 37 formed under the small washer 5.

This dual washer current collecting device provides a materially increased conducting surface that prevents current concentration on the metallic conductor coating of the rectifier, which materially reduces the failure due to current concentration and also provides for more uniform operating characteristics of the rectifier under comparative heavy loads without sacrificing the heat radiating quality of the rectifier and the current collector due to its resistance drop.

Other forms of mounting devices may be employed such as tubular eyelets in place of the bolt 22.

I claim:

1. A rectifier comprising a dry disc rectifier having a mounting opening, an insulated mounting member passing through the mounting opening of said dry disc rectifier, independent large and small frusto conically shaped spring washers, said washers having central openings surrounded by annular surfaces that mate in contact with each other when mounted in nested relation on said insulated mounting member, means for clamping said washers in contact with said dry disc rectifier for passing current therethrough, the rectifier surface contacting perimeter of the smaller washer being inwardly spaced from the rectifier surface contacting perimeter of the large washer when said clamping means holds said dry disc rectifier and washers in clamped relation.

2. The current .collector of claim 1 characterized in that the larger washer is solid and encloses over the that the conical angle of the large washer is greater than smaller washer. that of the small washer.

3. The current collector of claim 1 characterized in References Clted the file of thls Pawnt that the greatest diameter of the small Washer is approxi- 6 UNITED STATES PATENTS mately one-half that of the large Washer. 2 473 419 Fletcher at aL June 14 1949 4. The current collector of claim 1 characterized in 2'780667 Cataldo a Feb 1957 that the small washer has radial slots dividing the perirn- 2:852:723 Escofiery Sept 1&6, 11958 eter into segments.

5. The current collector of claim 4 characterized in 10

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