US2386065A

US2386065A - Electric resistance grid

Info

Publication number: US2386065A
Application number: US490566A
Authority: US
Inventors: Satchwell Leonard
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-06-27
Filing date: 1943-06-12
Publication date: 1945-10-02
Anticipated expiration: 1962-10-02

Description

Oct. 2, 1945 L. SATCHWELL ELECTRIC RESISTANCE GRID Filed June 12, 1943 2 Sheets-Sheet l ow Mz, M

L SATCHWELL 2,386,065

Oct. 2, 1945.

' ELECTRIC RESISTANCE GRID Filed June 12, 1943 2 Sheets-Sheet 2 [Lfi rfn Patented Oct. 2, 1945 UNITED STATES PATENT OFFICE ELECTRIC RESISTANCE GRID Leonard Satchwell, Marlow, England Application June 12, 1943, Serial No. 490,566 In Great Britain June 27, 1942 20 Claims.

The present invention relates to electric resistance grids.

Due to the inherently low specific resistance of common metals it has always been necessary to construct resistances by dividing or rolling metals into long paths and finally bending such long paths of metal into a series of coils or convolutions known as grids in such manner that a sufficient length of metal is contained within a compact cubic form while preserving air spaces between parallel lying portions of the path so that heat produced in the resistance may be dissipated by convection.

It is well known that mechanical weakness results from the form of construction referred to and determines the minimum spacing of the turns or convolutions of the metal if touching together of such turns or convolutions is to be avoided.

To overcome this disadvantage and to produce rigidity in such resistance grids it has been proposed to pass insulated supports through all the turns or every few turns or bars of the grids so as to clamp each bar or every few bars of the grid rigidly to prevent swagging and touching of adjacent turns or grids.

These methods of adding to the rigidity of the structure, apart from being costly, usually result in some part of the current carrying circuit being enclosed by the insulated supporting or stiffening means adversely afiecting dissipation of heat from the part so enclosed.

One object of the present invention is to provide a construction of electric resistance grids whereby rigidity may be added to grids in such manner that no part of the resistance grid itself is affected thermally by the stiiTening means. A further object of the invention is to provide means whereby terminals can be provided on the grids Which terminals are anchored to positions which are sufiiciently rigid to permit bolted connections to be made with safety.

In accordance with the present invention some of the bars of the electric resistance grid are provided with struts formed thereon or secured r thereto and extending beyond the grid proper for atttachment to stifiening or supporting members. Some of such struts are suitably formed to provide for tapping connections or to act as terminals at the ends of the grids. In resistance grids formed of a pair of spaced grid elements the struts suitably extend into the space between the grid elements and are anchored to a common stifiening or supporting member in such space.

The invention is illustrated in the accompanying drawings in which Fig. 1 is a perspective view of a resistance grid showing the invention applied to an arrangement of a pair of oppositely disposed grid elements each comprising a plurality of individual flat metal grid bar-s formed by stamping with oppositely extended bosses at the ends of the bars with the adjacent bosses of successive bars welded, brazed or soldered together to form a grid of substantially zigzag form somewhat as described in my copending application for patent, Serial No. 487,142.

Figs. 2, 3, 4 and 5 are views of different integers of a grid such as shown in Fig. 1 while Fig. 6 is a plan view of a typical arrangement of a number of resistance grids constructed as shown in Fig. 1 mounted on a supporting framework.

In the arrangement shown in Fig. l, the resistance grid is made up of a pair of grid elements some of the bars A of each of which are provided in accordance with the invention with struts b which extend outside the boundaries of the grid proper from about midway of the length of the bar. These struts b are anchored to stiffening or supporting members constituted by tie rods a which are in the form of insulated rods or tubes, the struts extending from the grids having pierced holes suitably arranged for assembly on such tie rods. Fig. 2 shows one bar of a grid such as is shown in Fig. 1 and shows two pierced holes b for the passage of thetwo tie rods :1, a of Fig. 1.

As shown in ,Fig. 1 some of the struts b are provided with extending portions 0 serving as tapping connections as shown in Fig. 3 also while in others the grid bar are provided with lugs e which serve as terminal connections as shown also in Fig. 4. In order to avoid the necessity of coverin the supporting rods with insulating material where such rods receive the struts threaded upon them the struts themselves may carry insulating means and a preferred form is shown in Fig. 5 wherein the metal around the holes I) of the struts is provided with embossments b" which form seatings for mica or like washers m, the internal diameter of which is less than that of the holes b. The mica or like washers m are aligned by the embossments b" and serve to position metal bushes or ferrules o secured thereon which serve to support the tie rods. As will be seen the mica or like washers m being of smaller internal diameter than the holes I) provide an air gap between the bushes or ferrules o and the struts. The tie rods in such circumstances do not require to be insulated as the strut carries its own insulation.

The number of struts provided for each grid will depend upon the lack of rigidity in a particular section of grid. If the grid bar is of large current carrying capacity and therefore of relatively large section it will not require as many struts as a grid used for weaker currents which will have a smaller section of metaland therefore less rigidity.

A number of electric resistance grids, such as shown in Fig. 1, are shown in Fig. 6 mounted in a supporting framework (1 and the strut formation is indicated in a representative case. The electric resistance grids are provided with brackets h secured to the tie rods (1, the brackets it being adapted for fixing on insulated support rods 70 which rods normally carry a number of resistance rids. The grids are shown as connected into continuous circuit by connection of the terminals 6.

I claim:

1. An electric resistance grid of zigzag form with parallel bars, stiffening members, some of said bars formed with integral projections extending from the grid proper transversely of the plane thereof for attachment to the stiffening members whereby to improve rigidity, and some of said projections having extended portions arranged to provide tapping connections.

2. An electric resistance grid of zigzag form with parallel bars, stiffening members, some of said bars having integral projections secured thereto and extending from the grid proper transversely of the plane thereof for attachment to the stiffening members whereby to improve rigidity, and some of said projections naving extended portions arranged to provide tappin con nections.

3. An electric resistance grid of zigzag form with parallel bars, stiifening members, some of said bars formed with integral projections extending from the grid proper transversely of the plane thereof for attachment to the stiffening members whereby to improve rigidity, and some of said projections having lugs extending therefrom and servin as terminal connections.

4. An electric resistance grid of zigzag form with parallel bars, stiffening, members, some of said bars having integral projections secured thereto and extending from the grid proper transversely of the plane thereof for attachment to the stiffening members whereby to improve rigidity, and some of said projections having lugs extending therefrom and serving as terminal connections.

5. An electric resistance grid of zigzag form with parallel bars, stiffening members, some of said bars formed with projections, said projections extending transversely of the plane of the grid proper for attachment to the stiffening members, said projections being formed with holes and with embossments around the holes, a pair of insulating Washers for each hole of smaller internal diameter than the holes, at least one of which about each hole seating in and retained by said embossments, and ferrules extending through the holes and washers and insulated from the projections by said washers, the stiffening members extending through the ferrules and the washers presenting an air gap between the projections and the ferrules whereby non-insulated stiffening members may be used.

6. An electric resistance grid of zigzag form having parallel bars, stiffening members, some of said bars having projections secured thereto, said projections extending transversely of the plane of the grid for attachment to the stiffening members said projections being formed with holes and with embossments around the holes, a pair of insulating washers for each hole of smaller internal diameter than the holes, at least one of which about each hole seatin in and retained by said embossments, ferrules extending through the holes and washers and insulated from the projections by said washers, the stiffening members extending through the ferrules and the washers presenting an air gap between the projections and the ferrules, and tapping connections integral with the projections and commonly insulated from the stiffening members, whereby non-insulated stiffening members may be used.

'7. An electric resistance grid formed of individual flat grid bars having integral projections extending from their faces adjacent their ends and welded to adjacent bars to provide a substantially zigzag form, stiffening members, some of said bars provided with struts extending from the grid proper for attachment to the stiffening members whereby to improve rigidity.

8. An electric resistance grid formed of individual fiat grid bars having integral projections extending from their faces adjacent their ends and brazed to adjacent bars to provide a substantially zigzag form, stiffening members, some of said bars provided with struts extending from the grid proper for attachment to the stiffening members whereby to improve rigidity.

9. An electric resistance grid formed of individual flat grid bars having integral projections extending from their faces adjacent their ends and soldered to adjacent bars to provide a substantially zigzag form, stiffenin members, some of said bars provided with struts extending from the grid proper for attachment to the stiffening members whereby to improve rigidity.

10. An electric resistance grid formed of a pair of spaced flat grid elements of zigzag form each comprising individual metal bars having integral projections extending from their faces adjacent their ends and welded to adjacent bars, stiffenin members, said bars having struts integral with some of the grid bars extending into the space between the grid elements, said struts adapted to be anchored to a common stiffening member.

11. An electric resistance grid formed of a pair of spaced fiat grid elements of zigzag form eacn comprising individual metal bars having integral projections extending from their faces adjacent their ends and brazed to adjacent bars, stiff ening members, said bars having struts integral with some of the grid bars extending into the space between the grid elements, said struts adapted to be anchored to a common stiffening member.

12. An electric resistance grid formed of a pair of spaced flat grid elements of zigzag form each comprising individual metal bars having integral projections extending from their faces adjacent their ends and soldered to adjacent bars, stiffening members, said bars having struts integral with some of the grid bars extending into the space between the grid elements, said struts adapted to be anchored to a common stiffening member.

13. An electric resistance grid formed of individual grid bars welded to ether adjacent their ends to provide a substantially zigzag form, stiffening members,.sorne of said bars provided with struts extending from about midway of the length of the grid bars for? attachment to Stifi-r ening members whereby to improve rigidity.

14. An electric resistance grid formed of individual grid bars brazed together adjacent their ends to provide a substantially zigzag form, stiff ening members, some of said bars provided with struts extending from about midway of the length of the grid bars for attachment to stiffening members whereby to improve rigidity.

15. An electric resistance grid formed of individual grid bars soldered together adjacent their ends to provide a substantially zigzag form, stiffening members, some of said bars provided with struts extending from about midway of the length of the grid bars for attachment to stiiT- ening members whereby to improve rigidity.

16. An electric resistance grid formed of a pair of spaced grid elements of zigzag form each comprising individual metal bars welded together adjacent their ends, stiffening members, some of said bars having struts integral therewith extending from about midway of the length of the grid bars into the space between the grid elements, said struts being adapted to be anchored to a common stiffening member.

17. An electric resistance grid formed of a pair of spaced grid elements of zigzag form each comprisin individual metal bars brazed together adjacent their ends, stiffening members, some of said bars having struts integral therewith extending from about midway of the length of the grid bars into the space between the grid elements, said struts being adapted to be anchored to a common stiffening member.

18. An electric resistance grid formed of a pair of spaced grid elements of zigzag form each comprising individual metal bars soldered together adjacent their ends, stiifening members, some of said bars having struts integral therewith extending from about midway of the length of the grid bars into the space between the grid elements, said struts being adapted to be anchored to a common stiffening member.

19. An electric resistance grid formed of individual grid bars welded together adjacent their ends to provide a substantially zigza form, stiffening members, some of said bars provided with struts provided with attached insulation and extending from about midway of the length of the grid bars for attachment to stiiTening members whereby to improve rigidity.

20. An electric resistance grid formed of a. pair of spaced grid elements of Zigzag form each comprising individual metal bars welded together adjacent their ends, stiffening members, some of said bars havin struts integral therewith with attached insulation and extending from about midway of the length of the grid bars into the space between the grid elements, said struts being adapted to be anchored to a common stifiening member.

LEONARD SATCHWELL.