US2685045A

US2685045A - Filament tensioning device

Info

Publication number: US2685045A
Application number: US325256A
Authority: US
Inventors: Robert J Black; Paul L Corbell
Original assignee: Collins Radio Co
Current assignee: Collins Radio Co
Priority date: 1951-07-09
Filing date: 1952-12-11
Publication date: 1954-07-27
Anticipated expiration: 1971-07-27

Description

y 1954 R. J. BLACK ETIAL FILAMENT TENSIONING DEVICE Original Filed July 9, 1951 INVENTOR. P4112 (04949121 /P0019 7 1/. 8146A Patented July 27, 1954 2,685,045 FILAMENT TENSIONING DEVICE Robert J. Black, Marion, Iowa, and Paul I. Corbell, Palo Alto, Calif., assignors to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Original application July 9, 1951, Serial No.

235,816, now Patent No. 2,656,480, dated October 20, 1953. Divided and this application December 11, 1952, Serial No. 325,256

2 Claims.

This invention relates in general to filament tensioning devices and in particular to means for maintaining a filament in a predetermined position and shape. This is a divisional case of application Serial Number 235,816, filed July 9, 1951 which matured as U. S. Patent No. 2,656,480 on ously to maintain a filament under tension by. attaching a coil or leaf spring to it, but in very .high power tubes such arrangements are not satisfactory for the reason that a filament becomes so hot that the spring becomes overheated and loses its flexibility.

It is an object of this invention therefore, to provide a filament which has one end integrally formed into a spring to maintain a filament under tension.

Another object of this invention is to provide a filament tensioning device wherein the filament is spring loaded by applying a spring bias to a relatively cool portion of the filament.

Yet another object of the invention is to provide a filament tensioning device which allows thermal expansion of the filament but maintains the filament in a predetermined special rela tionship.

A feature of this invention is found in the provision of a filament mounted between two fixed members with one end of the filament formed into a coil spring and with a flexible contact enageable with the filament adjacent the coil spring. A heating potential is applied between one supporting means and the flexible contact.

Another feature of this invention is found in the provision of a filament connected between a fixed point and the periphery of a rotatable cam which has a lever arm spring biased so as to tension the filament. A heating potential is applied between the fixed end of the filament and an intermediate point adjacent the cam.

Further objects, features and advantages of this invention will become apparent from the following description and claims when read in View of the drawings, in which;

Figure 1 is a side View of the filament tensioning device of this invention;

Figure 2 is a modification of the filament tensioning device of this invention; and,

Figure 3 is a detailed top view of the coilspring of Figure 2.

With reference to Figure 1, a filament I0 which might be a ribbon of tungsten for example, has its upper end ll clamped to a supporting means I2 by the screw l3 and plate [4. The lower end l6 of the filament I0 is connected by a set screw I! to the periphery of a cam l8.

The cam I8 is rotatably supported by a shaft I9 on a stand-01f 2|, and. the stand-off 2! is in turn connected to a supporting member 22. The cam I8 is formed with a lever arm 23 which has an opening 24 formed therethrough.

A shaft 26 is connected to member 22 and extends through the opening 24.. A washer 27 is mounted over the shaft 26 adjacent the lever arm 23. A coil spring 28 is mounted over the shaft 26 and between the Washer 21 and a second washer 29. A suitable'holding means, as for example, a nut 3| is threadedly received on the shaft 26 and the assembly forms a spring bias against the lever arm 23. It is to be noted that the opening 24 is substantially larger than the shaft 26 and thus the lever l8 may pivot about the shaft IS.

A feed-in conductor 32 is connected tothe stand-off 2| and is electrically connected to the filament ID by clamping means 33. The clamp 33 comprises clamping plates 34 and 36 and nut and bolt means 31. The lead 32 is flexible so that it will conform to the expansion of the filament It.

The heating potential is applied between the supporting member I2 and the supporting member 22, and substantially all of the heating current flows through the lead 32 to the supporting means 22. The lead 32 has a relatively low resistance and thus the path from the filament ID to the supporting member 22 will have less resistance than the path through the remainder of the filament l6 and the cam [8.

This allows the lower end I 6- of the filament to remain relatively cool and, thus the tensioning apparatus comprising the cam- I8 and spring 28 are not subjected to excessive temperatures. The spring holds the filament under tension and thus no sagging or bowing is allowed.

Figure 2 illustrates a modification of the invention. The filament ID has its upper end ll clamped to supporting member l2 and the lower end I6 is integrally formed into a coil spring 46.

The spring 40 is rigidly fastened to a shaft 4| which is mounted to a stand-off 42. The shaft 4! is non-rotatably mounted in the stand-off 42 and the tension of the spring 40 is maintained so as to hold the filament ID in tension. The stand-ofi 42 is attached to an extension 43 of the member 22 and as best seen in Figure 3, a slot 45 is formed in the extension 43 to receive the spring therein.

Adjacent the lower end 16, a clamping means 46 is attached to the filament 10. The clamping means comprises the

clamping plates

41 and 48 which are held to the filament by a set screw 50. The clamping plate 48 is connected to a pair of flexible members 49 and 5|, respectively, which have their opposite ends connected to a projection 52 of the member 22.

A heating potential is connected between the members l2 and 22 and the current flows through the filament l and through the members 49 and to the member 22. The

members

49 and 51 are made of low resistance material and, thus substantially all of the current flows tothe member 22 through them. The spring 40 receives very little current due to the higher resistance of the filament.

As expansion of the filament I0 occurs, due to an increasing temperature, the spring 40 takes up the slack and the flexible members 49 and 5| deflect to maintain the filament under tension. The filament II] will be maintained substantially fixed relative to the members l2 and 22 and there will be no bowing.

It is seen that this invention relates to filament tensioning means and although it has been described with respect to particular embodiments thereof, it is not to be so limited as changes and modifications may be made therein which are within the full intended scope of the invention as defined by the appended claims.

We claim: 1. Means for maintaining a filament under tension and in a predetermined spatial relationship between a pair of supporting members comprising, one end of said filament integrally formed into a coil spring, said coil spring nonrotatable attached to one of the supporting members, the other end of said filament attached to the other supporting member, a projection attached to the one supporting member adjacent the coil spring, clamping means attached to the filament adjacent the coil spring, a pair of flexible members connecting said projection with said clamping means, and said flexible members having a relatively low electrical resistance so that they carry substantially all of the heating current.

2. Means for maintaining a filament under tension and in a predetermined spatial relationship with a pair of supporting members comprising, first clamping means attaching one end of said filament to one of said supporting members, the other end of said filament integrally formed into a coil spring, said coil spring nonrotatably attached to the other supporting member, a pair of flexible electrical conducting means extending from said other supporting member to- Ward said filament, second clamping means attached to said filament adjacent said coil spring and with opposite sides thereof attached to, the free ends of said flexible members toform a pantograph assembly.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,402,797 Wood June 25, 1946 2,546,184 Garner Mar. 27, 1951