US1234149A - Electric unit. - Google Patents

Description

F. M. FURBER.

ELECTRIC UNIT. APPLICATION men MAR. 27, 1917.

1,234, 1 49. Patented July 24, 1917.

S85 the sharp curvature there causes the wire to this disorganizing tend- UNITED STATES PATENT FREDERICK I. FUBBEB. OF REVERE, MASSACHUSETTS, ASSIGNOR TO UNITED SHOE IAGHINEBY COMPANY, OF PATEBSON, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ELECTRIC UNIT.

To all whom it may concern:

Be it known that I, FREDERICK M.' F UR- man, a citizen of the United States, residing at Revere, in the county of Suffolk and State of Massachusetts, have invented certain Improvements in Electric Units, of which the following description, in connection with the accompanying drawings, is a ecification, like reference characters on t e drawings indicating like parts in the several figures.

This invention relates to electric heating units of general utilitly.

Heretofore when e ectric units have been used in situations where'they are subjected to severe shocks or vibrations it has been reason of the breaking of the resistance wire found that they deteriorate rapidly and that the repeated stress to which they are thus subjected leads to their destruction in a short time.

Great difliculty has been experienced by where itsends are fastened: This wire is in a manner involvin themselves,

to produce disorganization of molecular ,ar

' to yield rapidly often very small, and in units asheretofore.

constructed, has been fastened at its ends some form of more or less sharp bend. his, of course, puts one side of the wire in tension and the other side under compression, and when such units are used in situations where they are subject to rapidly recurring shocks, which, in as is well known, tend strongly rangement, the non-homogeneity of intermolecular stress at the bend produced by ency, with the result that it soon breaks.

Another cause of damage at this point is corrosion at thecjunction ofthe resistance wire and the terminal member to which it is fastened. The cause of this corrosion is somewhat obscure, but may be connected with thermo-electric effects due to the heatin of the junction of two dissimilar metals. Ttesistance wire is selected solely with'regard to its qualities as a durable resistance,

and its composition is therefore determined largely without regard to any possible relation it may have to other parts of the unit. Terminal members have been heretofore selected with re ard to mechanical considerations alone. have found that by properly selecting the material of which the terminal member is made, with regard to Specification of Letters Patent. Patented July 24, 1917,

Application filed larch 27, 1917. Serial K0. 157,782.

the material of which the resistance wire is constructed, (or vice versa), the corrosion of the parts at the junction of the wire and terminal members, and consequently the destruction of the unit, can be avoided.

The unit shown in the accompanying drawings is designed particularly for use in shoe machiner where the space for it is extremely limite and where it is subjected to swiftly recurring jars and shocks. The limitation as to space enforces the use of very small wire, less than 0.01 inch in diameter, and the violent treatment which the unit'undergoes makes imperative the preservation of the wire from any corrosion, since a very small degree of deterioration will destroy it.

I have found that corrosion at the junction of the wire and terminal block can be obviated by avoiding too great a chemical dissimilarity in the elements composing the joint. I conceive that the presence in these elements of elements belonging)to the same belonging to the same chemica group in its composition. In the unit described this group is the iron'group, and the specific elements are iron and nickel.

This and other features of the invention will be understood from the following description of a preferred embodiment of the invention, selected for purposes of illustration and shown in the accompanying drawings, in which; a

Figure 1 is a section of the head of a burnishing machine showing the unit in elevation; Fig. 2 is an enlarged elevation of the unit partly in section on the line 2--2 of Fig. 1; and

Figs. 3, 4 and 5 are details showing the manner of fastening the ends of the resistance wire.

The shaft 10 is oscillated'rapidly in suitable bearings not shown. It carries the head 11 upon which is-mounted the tool carrier 12, which supports the burnishing tools 13. The tool carrier 12 has a bore 14 in which is mounted the unit and which has a mica floor 14. Slots 15 in the walls of the upper end of the bore 14 permit the egress of the lead wires.

The unit is built up on a nickel steel rod 16, having a head 17 at one end. To this head is brazed one of the flexible lead wires 18, which carries a lava bead 19, a number of glass beads 20 and the terminal 21. The lava head 19 rests in the slot 15 and resists, better than a glass bead, the intense heat at this point.

Next to the head .17 on the rod 16, is mounted a mica washer 22, which is of larger diameter than the head 17 and just fits the bore 14. Next to the mica washer 22 24 and is helically threaded throughout its I length. Next to the core is mounted in electrical contact with the rod 16, a nickel steel terminal 26 of the same diameter as the core, and next to the terminal 26 is mounted another mica washer 27, indentical with the washer 22. Below this is mounted a steel washer 28 upon which the rod 16 is upset at 29.

i The resistance wire 30 is wound in the helical thread,'and fastened to its terminal elements 24, 26 in the manner shown in' Figs. 3, 4 and 5. A slot 31 is cut in each]. of the elements 24, 26, the ends of the wire lf? 30 are placed in h Sl an a h of t i jciently elastic to take up the relative expansion, necessarily minute, as shown, of the lips 32 is then upset overthe wire by a punchstroke, clamping itfirmly in position.

Of the numerous kinds of resistancelwire obtainable on the market, I have found the Driver-Harris Wire Companys nichrome wire the most satisfactory. This wirecon- :tains or more of nickel andasma'ller percentage of chromium. ifThoughtheL- performance and durability-of this wirefasiare sistance were found adequate, and theterininal fastenmg'means prevented mechanical destruction at the joint, considerable difficulty was at first experienced with corrosion at this point, the terminal rings 24 and 26 being of copper in the first units made. I found that by replacing the copper with a material having a closer relation to the wire 1n regard to chemical composition, the corrosion difliculty could be avoided. A convenient material for this purpose was found to be nickel steel, no appreciable corrosion appearing 1n the units in which it was used for terminals. I regard this freedom fromcorrosion as due to the presence of .chemi-f amount of material belonging to the same chemical members.

The current flows through the wire 18, head 17, rod 16, terminal 26, wire 30, rmg 24, to the wire 25. The washers 22, 27 project beyond the outer cylindrical portions of the unit, and insulate it from the wall of the bore 14. The floor 14' insulates the end of the rod 16. The necessity of a cover or case for the unit is thereby avoided, and the heat is more easily and directly conveyed to the tools.

The lava used in the core 25 has a mean thermal coefiicient of expansion between F. and 935 F., (just visible red) of 0000,0070 per 1 F., which is substantially that of steel. The nickel steel rod 16 used in the unit described has a mean thermal coelficient of expansion between the same limits of 0000,00? 6 per 1 F. The relative coefficient of expansion between these limits per 1 F., is, therefore, 0000,0006. The

group in both of the joint forming unit itself is about 21: inches long. The I ,ed on the rod 16, and will safely take stresses Ifdue to the heading up of the rod 16, which might crush a more unyielding structure.

At the same time the washers are suffinickel steel rod 16 and the lava core 25', when heated in use. The materialsof the unit supported on the rod 16 are thus bonded togetherin a compact mass, always under a substantial compression. I have found that the'layagcore is very resistant to shocks and that when'it' does break, it breaks crosswise. and-.not lengthwise. The longitudinal compression exerted by the rod 16 upon the core'efiectively precludes danger of breakage of this sort.

The-means adopted for fastening theends I of the resistance wire avoids the heretofore experlenced breakage of the wire at these points. Theslot 31 is substantially in the is wound on the unit, and the wire enters it without substantial bending; The upsetting prolongation of the helix in which the wire of the sides of the slot on'the wire applies a pressure to the wire which is substantiallyincreases from zero to a maximum longiuniform circumferentially and progressively,

'tudinally, from the ends of the slot to-"its middle so that sharp variations in molecular stress are avoided. It will be seen that in the unit shown, all the resistance wire is open to inspection and manipulation and that aburnedput wire can be readily replaced by the operator, by merely spreading the slots 31 and upsetting them again.

I do not claim broadly the use of nickel in a'terminal member herein, as I have claimed it in my co-pending application Serial No. 36,721, filed June 28, 1915.

Having described the invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric unit having resistance wire, and a terminal member to which it is fastened, the wire and member each containing a substantial quantity ofmaterial belonging to the same chemical group.

2. An electric unit having resistance wire, and a terminal member to which it is fastened, the wire and member each containing a substantial quantity of material belonging to the iron group.

3. An electric unit having resistance wire and a terminal member to which it is fastened, the wire and member containing substantial amounts respectively, of different materials belonging to the same chemical group.

4. An electric unit having resistance wire with nickel in its composition, and a terminal member for said wire having nickel in its composition.

5. An electric unit having resistance wire with nickel and chromium in its composition, and a terminal member of nickel steel for said wire.

In testimony whereof I have signed my name to this specification.

FREDERICK M. FURBER.

copies of this patent may be obtained for five cents each, by addressing the Commissioner of Iatents,

Washington, I). G.

Images