US2931997A

US2931997A - Mounting for tubular resistors

Info

Publication number: US2931997A
Application number: US704670A
Authority: US
Inventors: Scribner Arthur Clayton
Original assignee: Ward Leonard Electric Co
Current assignee: Ward Leonard Electric Co
Priority date: 1957-12-23
Filing date: 1957-12-23
Publication date: 1960-04-05
Anticipated expiration: 1977-04-05

Description

APril 1960 A. c. SCRIBNER 2,931,997

MOUNTING FOR TUBULAR RESISTORS Filed Dec. 23, 1957 I NV EN T OR. Jen/0e (array 'ce/ade'e ,iJ/ATTORNEY 2,931,991 MOUNTING FOR TUBULAR RESISTORS Arthur Clayton Scribner, Rowayton,

Ward Leonard Electric Co., corporation of New York Conn., assignor to Mount Vernon, N.Y., a

This invention relates to tubular resistor mountings and the mounting of a plurality of resistors in compact relation.

An object of this invention is to mount tubular electrical resistor units with high heat dissipation from the resistors.

Another object of the invention is to increase the flow of the cooling medium passing through and over a number of closely mounted tubular resistors.

J Another object of the invention is to provide a mounting for tubular resistors that does not obstruct the flow of air around and through the resistors.

Another object of the invention is to increase the wattage dissipation of heat from a bank of resistors while maintaining resistors within the operative temperatures.

Another object of the invention is to provide a mounting for tubular resistors that is inexpensive and on which it is easy to mount resistors.

Another object of the invention is to provide for thermal changes in the dimensions of the mounting and resistor and to maintain the stress on the tubular resistor at a minimum. 7

*Other and further objects will become apparent from the following description taken in connection with the drawings, in which- Fig. 1 is a fragmentary view of a bank of tubular resistors mounted in accordance with the invention.

Fig. 2 is a fragmentary top view of a plurality of rows of tubular resistors.

Fig. 3 is a sectional view of the tubular resistor and the mounting taken along lines 3--3 of Fig. 1. 1

Figs. 4 and 5 illustrate the spring mounting brackets. Fig. 6 illustrates a portable rheostat utilizing the invention.

Fig. 7 is a fragmentary sectional view of the mounting of the supporting strip to the frame; and

'Figs. 8 and 9 are fragmentary views of another embodiment of the mounting.

In Fig. 6 a rheostat unit is illustrated in which a plurality of rows of resistors is provided which may be connected in and out of the circuit to vary the resistance of the circuit for various purposes. A frame 10 is provided for supporting the units of the rheostat and has cross members 11 spaced on opposite sides of the frame for supporting the cross supporting strips 12 upon which the resistors are mounted in rows. Each resistor row comprises a plurality of individual resistors 13, each separately mounted on the cross supporting strips 12 by clips 14. The cross strips 12 are thin, flat steel pieces with the plane of the strip extending parallel to the axes of the resistors so as to present a minimum resistance to the flow of air. The strips 12 are secured at each end to the cross members 11 by means of angles 12b welded to the strips 12 and bolted to the cross pieces 11 (Fig. 7).

The strips 12 are arranged to support a plurality of rows of resistors as illustrated in Figs. 1, 2 and 7. The resistors are solely secured to the strips 12 by means of tend in a plane parallel to the axis of the 2,931,997 l atented Apr. 5, v1960 the spring mounting brackets 14. The resistors 13 are spaced to provide room for the radiation and dissipation of heat by convection current passing around and between the resistors.

The brackets 14 (Figs. 4 and 5) are formed from a resilient steel wire formed with

legs

15 and 16 connected at one end by a U-shaped member 17 and at the other end by a clip 18. The

legs

15 and 16 are preferably spot welded to the clip 18 on opposite sides of the mounting opening 19 to secure the end of the

legs

15 and 16 together and to provide a mounting for the bracket 14. The legs of the bracket are parallel and formed in a generally U-shape with the

legs

15 and 16 extending generally parallel to the plane through the clip 18 along the

portions

15a and 16a and then having portions 15b and 16b at an angle thereto connected by the U-shaped portions and 160. The mounting bracket 14 is resilient and the leg portions 15b and 16b may be pressed towards the

leg portions

15a and 16a under pressure.

The brackets 14 are mounted in opposite ends of the tubular member 13 with the bracket in a compressed condition to fit in the end of the tube. Under the compresssive force applied to the bracket 14, the legs 15a,. 16a and 15b, 16b engage the inner wall 13a of the tubu-- lar member along a substantial portion of their respec tive lengths. The expansive force of the bracket fric 17 is bent at an angle to the legs 15!) and 16b to provide:

a means for preventing the tubular resistor from sliding:

off the end of the brackets and engaging the strips 12.. As indicated in Fig. 7, the bracket is fastened to the strip 12 so that the member 17 is positioned between the strip- 12 and the end of the tubular resistor. Normally the frictional force of the legs of the bracket is suflicient tw hold the resistor in place, however, under extreme vibration slippage may occur. The U-shaped portion 17 connecting the other ends of the

wires

15 and 16 engages the end of the tubular resistor so that the resistor is held against axial movement by the U-shaped portion 17.

With the clip 18 in a plane parallel to the

legs

15 and 16, the clip extends parallel to the axis of the tubular resistor, so that the clip is extending in the direction of the air flow through and over the tubular resistor. The clip 18 is secured to the strips 12 by means of machine screws 20 fitting snugly in the openings 19 and threaded into openings in the strips 12. The strips extubular resistor so that each of the mounting members presents the portion of the member having the smallest dimension to the air flow, and thereby reduces the resistance to the air flow to a minimum. The wire brackets 14

form openings

22, 23 and 24 in the bore 21 of the tubular members through which air may readily fiow, thus permitting substantial quantities of air to flow up through the center of the tubular resistor to remove heat from the inner walls.

The supporting strip has its narrow dimensions across the air flow and the brackets are mounted on the channel so that as each strip crosses the end ceramic portion of the resistor it does not cross the bore 21. Thus, the obstruction to the air flow through the center of the resistor and around the outer surface is reduced to a minimum permitting a more rapid flow of air past the resistor and reducing the effect of pocketing or stagnant areas adjacent to the resistor which would create local overheating due to the non-convection of air currents past the heated portions of the resistor.

The bracket 14 is made of a resilient spring steel or suitable resilient material and provides a resilient mounting for the tubular resistor, isolating the resistor from shocks and vibrations that may be applied to the frame of the rheostat. The bracket forms a firm attachment so that the resistor does not vibrate or move on the mounting. Also, the mounting provides for readjustment to the variations in temperature of the frame members and mounting brackets without applying strain to the resistors. Thus, the "resistors are isolated from vibrational and thermal changes, thereby reducing the susceptability of the resistors to break down from physical forces applied to the frame.

The topv framework of the cross .strip portions 12 and the brackets 14 forms

air spaces

26 and 27 between the resistors to permit the easy flow of cooling air in a direction parallel to the

inner spaces

22, 23 and, 24 within the tubular resistors. This increased airflow increases the heat; dissipation from each resistor and from the resistors assembled in a group in'accordance. with the teachings of this invention. In the previously described, embodiment the rows of resistors are parallel. However, the invention provides for the arrangement of the rows with. theresistors end to end. With the strip 12 parallel to the. air flow, the spaces 27 between the resistors areunob structed and the air can flow smoothly past one resistor and on to the next, resistor to remove the heat dissipated. Also, the. air can ..l1ow through and out of. the

, end of the bore to impinge on the, succeeding resistor.

This increase in heat dissipation permits a reduction in the number of resistors or an increase in the Wattage of a given bank of resistors, Thus, a higher load capacity and a structurally superiorrheostat may be provided without an increase in cost. Themounting, in addition to increasing the heat dissipation, also reduces thefailure of resistors due to physical forces applied thereto, and thus reduces the maintenancev and replacement of parts in the rheostat.

Although the formof the. clip shown .inFigs. 4 and is the preferred embodiment, the invention may .bepracticed in other forms. In FigsQ'S and, 9 a clip 30 is formed from resilient sheet materiahsuch as steel-,-' and is bent in a V-shaped

toform portions

31 and, 3,2. These portions have a common edge .33 and end edges 34 and35, re-

spectively, which press against the inner bore 13a of they resistor under the resilient compression of, the clip, The portion 31 is extended to form a mounting means 36 with a hole 37 for a fastening bolt. The, portion 32 has an angularextension 38. similar to the portion 17 of the clip 14. to prevent, thev resistor .from slipping against the mounting strip under undue vibration. Also, types of resistors other than ceramic resistors may be mounted in this manner. 7

Although in the foregoing description, of the apparatus the resistors have been'described as being cooled by air,

it is understood that any suitable cooling medium may assess? of the bore of the resistor at opposite sides thereof under compression to frictionally support the resistor, and narrow strip-like. means positioned adjacent the end of the resistor and extending in a plane parallel to the tubular resistor, said wire members secured to said strip-like means to support said resistor with the strip-like means overlapping the resistor along the edge of the wall of the resistor to minimize the obstruction of the flow of air around and through the resistor.

'2. Mounting means for a tubular resistor having a central bore extending therethrough'comprising a singlepiece resilient Wire member having a U-shape and forming two legs and a connecting portion, each leg bent in a U-shape to form leg portions, said member fitting in the end of the bore with the leg portions in engagement with the wall of the tubular resistor and supporting said resistor under resilient pressure, strip-like means I extending; parallel to the axis of the tubular member, fastening means on the other end of said wire member to secure said resistor with the narrow edge passing the end of the wall ofsaid' tubular member to facilitate the airflow through and around the resistor.

3. A supporting means for a resistive member comprising'a tubular member supporting said resistive member and having a central axial bore formed by a generally tubular shaped wall with an outer surface, strip-like means for supporting said tubular member at each end thereof, two resilient substantially V-shaped plate members fitting in a respective end of said tubular member, each plate member having two thin plate portions extending longitudinally in said bore parallel to the axis and wall of said bore and secured along a common longitudinally extending edge, said plate portions having longitudinally extending side edges generally parallel to the common edge, said common and sideedges engaging the wall of said bor'e'along spaced contact lines under the resilient pressure of said plate member to frictionally support said tubular member, and fastening means. 011. j said plate member for securing saidtubular rne'mbe'r on saidstrip-like means with said strip-like means extending across said tubular member between the bore and the outer surface to permit the ready flow of air through and around the tubular member supporting the resistive member to remove the heat therefrom.

4.. Mounting means as set forth in claim 2 in which said connecting portion is U-shaped and at an angle to I said, leg portions and positioned inrelation to said striplike means so as to prevent said resistor from engagin said'strip-like means.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain Oct. 15, 193 1