US278353A - Electric switch-board - Google Patents

Description

2 Sheets-Sheet 1.'y

(No Model.)

W. J. MGBLROY. EVLEUTRIG SWITCH BOARD.-

Patented May 29,1883.

llll L l x L (No Model.) Z'Sheets-Sheet 2.

W. J. MOBLROY. ELEGTRIG SWITCH BOARD.

' wah-7 UNITED STATES WILLIAM J. MCELROY, OF PITTSBURG, PENNSYLVANIA.

ELECTRIC SWITCH-BOARD.

SPECIFICATION forming part of Letters Patent No. 273,353, dated May 29, 1833.

Application filed February 5, 1883. (No model.)

To all whom it may concern Be it known that I, WILLIAM J. MCELROY, of Pittsburg, county of Allegheny, State of Pennsylvania, have invented or discovered a newandusefulmprovementinSwitch-Boards; and I do hereby declare the following to be a -full,clear, concise, and exact description thereof, reference being had to the accompanying drawings, making a part ot this specification, in whichlike letters indicating like parts- Figure 1, Sheet Il, is a view in elevation of my improved switch-board. Figs. 2, 3, and 4 are views in elevation, to an enlarged scale, of plugs adapted for use in making switch or circuit connection-011 the board. Figs. 5 and 6, Sheet 2, are views in side and edge elevation of the induction-screen employed in the board. Fig. 7 is an edge vieW, partly broken away, of the switchboard; and Fig. Sis a plan view of one corner of the board, a portion of the plates constituting the frame being broken away.

Myinvention relates to certain improvementsin switch-boards; and, in general terms, it consists ot' certain combinations of an open frame, of conducting-bars secured by their ends across the centralopening in the frame, and metal induction-plates between and separate from the bars, with means for securing the plates and bars and for making connection between different bars, as hereinafter more fully described and claimed.

In the useof switch-boards as ordinarily constructed, interference arises or exists to a considerable degree from two different sourcesnamely, conduction, sometimes called leakage77 or escape from one conductor to another throughb the body or substance ot' the board, and induction, due to the presence of one conductor wit-hin the field or lines of force of another electrically excited. The interference due to these causes is especially troublesome in telephone service owing to exceeding sensitiveness of these instruments to electric impulse.

rlhe purpose of my invention is to provide a switch-board so constructed as to be free or practically free from disturbance due to these causes, thereby adapting it especially for use on telephone-lines, though it maybe used with equally good results for ordinary telegraphic purposes.

In the drawings l have represented an open rectangular frame, A, the bars or sides of which are made up ot' three layers of plates, au' a2,

fastened together by screws a3 in any desired number, whereby the parts or plates of the frame may be separated'and replaced at pleasure. The bars of the frame may be secured together at the angles bylap-joints, or by tenori and mortise, or in any other convenient way. The material of the frame is by preference hard rubber or vulcanite, though other Inaterial which is anon'conductor of electricity may be employed.

The conducting=bars c e are passed across the frame from side to side, one set, e, being horizontal, and the other set, o, being vertical. The bars of each set are separated from each other a sufficient space to permit of the insertion between themvof a plug, R, or S, (shown in Figs. 2, 3, and 4, enlarged or full size,) and also the separate sets of bars are separatedin depth suflicient to prevent conduction of elec tricity from bar to bar through atmosphere under usual conditions of moisture and pressure. This separation in depth I have shown about equal to one-'third the full thickness ot' the frame-say the full thickness of the middle plate, a'. to the frame theirends are passed intoits sides, say, one-halt' their width (more or less) or suiiciently to give a firmk support. (See Figs. 7 and 8, also dotted lines, Fig. I.) In doing this recesses t', ot proper size and form to receive the ends of the front or vertical bars, c, are made in `the inner face of the front or face plate, a, (see Fig. 7,) and similar recesses, fi', are made for the ends of the horizontal bars c in the inner face of the back plate, a2. (See Fig. 8.) In order to make electrical connection with the bars, one end is looped, as at c c', forming eyes, through which are passed the fastening bolts or screws u ot` binding-posts N, and to secure certain metallic contact the barrel n of these posts is letinto the plates ofthe frame, (see Fig. 7,) so that the inner shoulder, n, presses firmly upon the side face ofthe eye. Instead of screw bolts n, equivalent wood 'screws or gimlet-pointed screws may be formed yon the end of the barrel and screwed into the plate or plates below the eye. I prefer the bolts, however, as affording greater security' and assistance in holding the plates of the frame together. The bars maybe either rect- (See Fig. 7.) In securing the bars` IOO angular in section, as represented in Fig. l, or round, as in Figs. 7 and 8. I prefer the former on account of affording increased surface-contact with the switch-plu gs presently described. They. are, by preference,made of steelor other good electric conducting metal or alloy capable of being hardened by tempering, so as to possess elasticity or spring action sufficient to prevent permanent bending or distortion of the bars. Bars of soft or untempered metal may be used, however, if made of sufficient size or area in section to retain a straight form under the conditions of use. In this construction of the frame and bars there is no solid connecting substance between the bars of any kind, except at their ends, air only being in contact with them over the greater part of their surface. Consequently conduction between wires will be limited to such end contact and be reduced practically to minimum or nothing. In this respect decided advantage is gained over boards employing a body or back in contact with the whole or greater part ofthe length of the switeh-bars, as commonly practiced. Itis well known that air is among the best of insulators, and by providing` for air-contact along with the whole surface ofthe bars, except their ends, I secure to a corresponding extent the greatest attainable degree of insulation, and consequent protection against conduction or escape of electric force from wire to wire. In

l order to make the desired electric connection between the bars ot' the two sets, I make use of a plug, R, Fig. 2, having a head, 9, of hard rubber or other suitable non-conductor, and a fourpronged metal body, r', the space r2 between prongs corresponding in width to the thickness ofthe bars, so that the prongs may straddle the bars at the crossing-points, with their fiat inner faces pressing closely upon the flat side faces of the bars. Other than ilat faces may be used, either on the hars or prongs, or both, and still secure electrical contact or connection. I prefer the fiat forms, however, on account of the increased contactsurfaee secured thereby.

In Figs. 3 and 4 I have shown a modified form of plug, S, more especially adapted to straddle around bars, as in Figs 7 and 8, consisting of non-conducting head s, short and long prongs s s2, forming a hook for engaging a portion ot' the surface of the front bar, the longer prong, s?, beingsplit, as at s, and having a seat or recess, s, in such split, at or near the point adapted to receive the rear bar, the two parts of the split prong separating to receive the bar, and then pressing it with spring action to insure good contact. In this form of plug the distance between the seats should correspond accurately with the distance between bars, so as to press them firmly. This calls for accuracy of fitting, and for this reason, as well as for its adaptation to the pre ferred form of bars, Fig. 1, I prefer the form of plug shown in Fic". 2. Both, however, em-

brace substantially the saine features of fourpronged construction, the short and long prongs s s forming two for the front bar, and the split in prong s2 forming, in effect, two prongs for the rear bar. I therefore consider both these forms as coming within my invention, in the sense of being four-pronged, and adapted to embrace two sides of the bars and thereby obtain the requisite support and im! part the desired pressurecontact.

` In providing against conduction of electric force in the construction ofthe board, as above described, one material and important source of interference is practically removed.

In order to provide against induction, two sets or series of plates or bars, d b, are einployed, one set, as b, being arranged parallel with and midway between thefront bars, c, or between pairs of such bars, and the other set, d, being arranged in like manner between the rear bars, c. These plates b d are made of some soft conducting metal, by preference soft iron, and may be nickel-plated or otherwise coated to prevent oxidation. Also, if desired, the bars c c may be protected in like manner.

As represented in Figs. 5 and G, the plates b cl are arranged across each other, edge to edge, and they may be rigidly secured together in such relationship by screw-bolts or by soldering, or in other convenient way, forming what Iterin an induction-screen,77 I3, which is supported in position within the opening in the main frame A by corner-stays h on the back, secured by screws or in other convenient way. The combined width of bars b d is, by preference, about equal to the thickness of frame A, bringing their outer-edge faces and the side faces of the frame in or near the saine planes. As before described, the two sets of bars c e are let into the inner faces ofthe outer pieces ,a aofthefraine. Consequently each set of such bars will be nearly in central plane of their respective sets of induction-plates Z; d, as represented in Fig. 7, so that thelatter will extend in depth both in front and rear of the plane of the conducting-bars. rJhus the induction-plates, so far as they extend, intercept all lines of force between conducting-bars, and if made ot' appreciable body or thickness-say about equal to the thickness ot' the conductingbars-they will arrest the force exerted in such lines, thereby protecting or shielding the conducting-bars. Also, by making the inductionplates to overreach or exceed the conductors in depth, bothforward and backward,they cover or subtend a greater arc of radiation than the conductors,andwill shield them not only from direct radial lines of force, but also from diffusion of force, the conductors lying, as it were, withina deep shadowin the field efforce, which shadow is formed or projected by the overreaching induction-plates. By projecting the conductors in this manner induction will be so far reduced as to give :no trouble and for all practical purposes to be absent. The ends of the conductors alone are unprotected, and the exposure thus made is so small as to produce IOO ICIS

IIO

irq

no troublesome interference. It' desired, the induction-plates may be carried closer to the inner edge of the frame than shown, or they may be passed into the frame, say, the full depth of the conducting-bars. I prefer, however, to stop them a little short of the frame,

as shown, in order better -to prevent conduc tion.

If desired, the induction-screen may have ground connection of any suitable kind to carry oi' any electric currents that may be excited therein by reason of its position in the eld of force of the electrically-excited conductors.

I have shown the bars c ein each set grouped in pairs, forming loops for incoming and outgoing lines, and the induction-plates b d placed between successive pairs instead of between individual successivebars. ,This form of board is designed more especially' for wayoftices. For a terminal office all the bars would be separated by such induction-plates, as each bar might form part `of a separate line. In both cases the bars forming parts of separate lines are separated by intermediate induction-plates. Theforces which cause the interferences above described are, relatively speaking, small but dit'ticult to control, and capable of causing serious trouble, especially in telephonie service.

The -features of improvementI herein described by which such troubles are materially reduced .or practically removed are, therefore, of great utility and advantage.

1 claim herein as my invention- 1. In a switch-board', the combination of two sets ot conducting-bars crossing the board in different planes and directions for line-connec tions, with induction -plates of metal interposed between the conducting-bars in each set, substantially as and for the purposes set forth.

2. In a switch -board, the combination of frame A, with open interior, two sets of conducting-bars, c e, crossing the open space within the frame in different planes and directions, and induction-plates b d, interposed between the conducting-bars in each set, the conductors and plates being unconnected within the frame by solid substance, substantially as set forth.-

8. The combination ot' frame A, conductingbars c e, crossing the open space in the frame in diierent planes and directions, and induction-plates b d, interposed between the conducting-bars, and overreaching -the bars in depth, both in front and rear, substantially as and for the purposes set forth.

4. Theinduction-screen B, composed of metal plates b cl in di'erent planes, crossing each other edge to edge, in combination with conducting-bars c e, interposed between the plates in or near their central planes and surrounding frame A, substantially as set forth.

5. A switchboard having a frame with open inner space and conducting-bars crossing such open space .in different planes and directions, in combination with a switch-plug havin g separate prongs adapted to straddle the conducting-bars and press their side faces, substantially as and for the purposes set forth.

6. A switch-plug having a non-conducting `head and a four-pronged metallicbody, substantially as and for the purposes set forth.

In testimony whereof I have hereunto set my hand.

WILLIAM J. MGELROY.

Witnesses:

R. H. WHITTLESEY, C. L. PARKER.

Images