US746772A - Electrical switch-box apparatus. - Google Patents

Description

No. 746,772. PATENTED 13110.15, 190s.

- G. L. ADDBNBROOKB.

ELECTRICAL SWITGH'BOX APPARATUS.

APPLICATION FILED MAY 17, 1902.

N0 MODEL. 3 SHEETS-BEBE! 1- PATBNTED D3015, 1903..

No, 746;772. v

j G. L. ADDENBROOKB.

ELEGTRIGAL SWITCH BOX APPARATUS. no HGDEL. APBLIOATION FILED MA? 17, 190B. 3 SHEETS SHEET- 1m". bums Firms cm, mom-Limo" msnmsmu. n, :24

Eatented. ijecember 15, 1903.

GEORGE LEONARD ADDENBROOKE, 'o' WESTMINSTER, ENGLAND.

ELECTRICAL SWlTCH-BOX APPARATUS.

SPECIFICATION forming part of Letters Patent No. 746,772, dated December 15, 1903.

: Applicatiou filed May 17, 1902. fierial No. 167,846 (No modelJ To all whom it may concern:

Be it known that I, GEORGE LEONARD AD- DENBROOKE,a snbjectof the King of the British Doininicns, whose post-oflice address is 53 Victoria street, Westminster, in the county of London, England, have invented certain new and useful Improvements in Electrical Switch-Box Apparat us,of which the following is a specification.

This invention relates to the switch-box apparatus used for testing, standardizing, or calibrating electrostatic instruments. It is adapted to facilitate not only the said operations in connections with such instruments, but also to introduce and reproduce all the practical conditions found in circuits in which electrical energy is employed and in combination with the said instruments to ascertain the values of those conditions.

The present invention is an improvement on my former invention for whichBritish Letters Patent were granted to me dated October 18, 1889, No. 20,862.

In the further description of this invention reference is made to the accompanying drawings, in which- Figure l is a diagram showing the connections of the switches, resistances,circuits, and terminals as arranged in the switch-box apparatus. Fig. 2 is a plan of the switchbox with the outer cover removed; and Fig. 3 is a longitudinal sectional elevation on the line ,2 z of Fig. 2, several of the switch-handles and contact-points, however, and all the wire connections being omitted for the sake of clearness. Figs. 4 and 5 are two diagrams respectively indicating connections made in testing.

In the drawings the base and other required parts are to be understood as being made of ebonite, wood, or other suitable insulating material without especial mention. On the base a suitable side and end pieces a are erected and secured together to form a box, each of the two ends being set in ashort distance from the base a to receive a hinged piece or cover 0, and leave a space E) between, within which space several insulated wire connections or leads are brought and their bare ends placed insmall horizontal holes and contact securedby-terminal set-screws c, as shown on the left side of Fig. 3.

An ebonite cap-piece aP-is secured to the hinged and end cover a so as to cover over the whole of the countersunk terminal screws c at each end, the said screws being indicated by dotted lines in Fig. 2. The space 6 is blocked on the side of the box on which the operator stands, (corresponding to the lower side of Fig. 2,) but it is open at the other or farther end for the passage of the inso lated wire leads into the said space. A cover a is fitted upon the sideand end pieces on which the switches and resistances are mounted. A rabbeted bead b is secured upon the sides and end parts of the cover a and adapted to receive a thick glass plate b to form an upper covering inclosing the contact and bridge pieces of the switches and resistances within the horizontal space 5 so as to efifectually safeguard the operator from. accidentally touching any metallic points and to shield them fromldust. Holes are made in the glass for the passage of the working spindles of the switch and resistance-handles, the said handles being of ebonite or otherwise suitably insulated and for the most part removable from the lower part of their respective spindles. An out-er cover (indicated by dotted lines) is fitted over the outside of the bead b to protect the glass when not in use,

and in putting it on it is adapted to push down the handle and spindle d of the battery plug-switch, which is thus arranged to prevent it being left in circuit with either of its connections and possible danger and also to prevent the battery from running down when not in use.

- The switch-box apparatus is so arranged that the standardizing or calibrating operations can be carried on separately and free from contact with the main circuit-'that is,

the circuit in which the current is to be tested 2 and 3.

of the two circular switch es g and h and called the pressure ratio. The current-ratio resistance, collectively amounting to one hundred thousand ohms, is placed between the terminals of a battery in the proportion of ninety-seven per cent. in the bobbin indicated by i in the diagram Fig. 1, two per cent. divided between the contact-points of the switch 2', and the remaining one per cent. divided between the contact points and switches e andfin the proportion of one-tenth of one per cent. to the switch e and ninetenths of one per cent. to the switchf.

The switch 6 is constructed as two separate semicircular halves, though worked in unison simultaneously. This is accomplished by making an insulated switch-handle 9 (conveniently formed as a milled-edge knob of ebonite) and connecting it to separate and insulated metal switch-arms e e, oppositely placed as a bridge, one of them resting on and making contact with a semicircular metal strip a and a contiguous contact-point on the upper half of the semicircle 2, while the other arm e similarly makes contact on the lower half of the semicircle 6 all as shown in Figs. The contact-point of each half of the circle begins with 0, the next is 1, and so on up to 10. There are, therefore, in the complete circle of the switch 6 twenty ten-ohm coils; but owing to the insulation between the arms 6 when turning them by the ebonite knob e in order tov insert ten ohms in the circuit of the upper semicircle ten ohms are concurrently cut out of the lower semicircular circuit by the simultaneous movement of the opposite insulated arm 6 in moving from 10 to 9, and so on with each further movement from point to point. Consequently the predetermined total resistance across the circuit between the battery-terminals is always the same,'any ratio of resistance, however, being obtainable in steps of ten on either the upper or lower semicircular circuit, according to the direction in which the knob e is turned. The switch f, with its two switch-arms f f, forming the bridge between the semicircularstrips f f and their respective contact-points of the upper and lower circuits, is constructed and operates precisely in the same manner as the switch 6; but whereas the latter indicates tens between contiguous contact-points the switch f similarly indicates hundreds. The'switch o} is of the ordinary type. Its three contact-points respectively indicate zero, or ninety-seven thousand ohms, on the right-hand point, (being directly connected to the resistance 2 the center point having one thousand ohms between it and the zero or right-hand point and the left-hand point having also one thousand ohms between it and the center contact-point. Consequently in operating switch i for testing or calibration work it-acts as a coarse adjustment, the switch fas a fine adjustment of the resistance in the circuit, while the switch e operates as the finest adjustment, and the arrangement therefore facilitates the work of testing, or calibrating very greatly. Any number of such dials or switches may be added, according to the degree of accuracy required.

The pressure-ratio switches g and h are constructed and operate in the same manner as the switches e and f, each switch g and 71. being divided into an upper anda lower half, respectively insulated from each other, with their switch-arms g g h h, semicircular metal strips 9 g g 71 W, as before described for the switches e and f. On the switch g, however, there are ten contact-points and a zero-point on each semicircular circuit, and the circuits of the upper halves are arranged and putin series by the switch-arms or bridges in the order of the top semicircular circuit of g with the top half of h, then the bottom half of h,and the bottom half of g, as shown in the diagram of Fig. 1.

From the above description it will be seen that my object has been to split or subdivide the current ratio (comprising the resistances controlled by the switches e,f, and i) and the pressure ratio, (comprising the resistances controlled by the switches g and h,) each ratio in the switch-box apparatus under notice having a resistance of one hundred thousand ohms; but it will be evident that'any other predetermined amount of resistance may be employed and subdivided in a similar manner and applied to the same purpose. This purpose is to enable the operator to select or ascertain any particular amount of resistance of either ratio and apply the pressure to the needle of the wattmeter and the current to the quadrants at the same time, either for the purpose of calibration or for measurement or for reproducing any desired conditions, and thereby ascertaining their values.

Any required degree of voltage or current selected from either ratio resistance can be applied through the series resistance switches j andj', the pressure being conducted to the needle of the wattmeter W and the current to its quadrants simultaneously for the purpose above stated. The series resistance is arranged in two circles, the first, j, having ten one-hundred-ohm coils, with their contact-points placed on the circular path traced by its pivoted switch-arm. The other switch, 3', has ten one-thousand-ohm coils similarly placed in series with its pivoted switch-arm, and the latter is centrally connected to the battery-reversing key It, as shown in the diagram Fig. 1, from which connections are made to the battery positive pole and the battery common point, both the latter being shown on the left-hand side of the switch-box in Fig. 2.

Assuming a point to be taken on the dial hof the pressure ratio, by moving the switcharm h from the zero 0 to any point chosen, the upper and lower semicircles being joined by the switch-arm, as before described, the switch-arm m is then placed on the ratio contact-point r of the voltmeter and the switcharm 0 of the wattmeter-needle also on its ratio contact-point r, as shown in Fig. 2. The point taken on the dial h would then indicate the potential difference between the bat-c or accuracy of readings be desired-such as tens, units, tenths, and hundredths-and in all such cases the first dial can be arranged as a single dial, as already described in respect to the dial it.

With regard to the current ratio the two double dials fand c act as described previously for the dials 72- andg, while the small single dial i is made thus, it being the first of the series, in conformity with the above statement. As these three dials i, f, and e relate only to three per cent. of the whole resistance of the current ratio, the-remainder of the resistance may be done up or arranged in the form of one or more bobbins, The resistancecoils of several parts of the current ratio are connected in-series in the order following: the upper half orsemicircle of the diale with the upper half of the dial f, then the resistance r? of ninety-seven thousand ohms, then through the single dial 2' to the lower half of the dial f, and thence through the lower half of the dial (2, all as shown in the diagram Fig. 1. V

The battery-switch dis a plug-switch adapted to be pulled upward when in use, but necessarily pushed down in pnttingon the cover when out of use to avoid dangerous connections, as before mentioned. A metallic ring 61 is mounted on a round block of insulating material attached to the spindle of the knob 11, the said ring being adapted to make contact with three springs when pulled up as shown in Fig. 3. One of the springs, 61?, is in electrical connection with the common point on the omnibus-bar ot' a standard (or Glarkes) cell. A second one, (1 leads tothe battery-reverser 1c, and the third spring, d, is connected to the instrument-bar or common point Z.

Four switches are arranged along the side of the box conveniently next to the operator for working. The switch in is intended for use with the voltmeter, the switch it for the ammeter, the double set of switches o and p are for the wattmeter, 0 being connected up to theneedle and p to the quadrant or sector plates of the instrument. Contact-points are arranged in a semicircular manner around each of the four switches,

the bridge being actuated by a milled-edge knob of ebonite or othersuitable insulating material. A twenty-thousand-ohm coil is placed in circuit between the instrument common oar land the contact-points q of each switch. The ratio contact-points are indicated by r, the battery-contacts by s, the standard or Glarkes cell by t, the short-circuit contacts by u, and the circuit contactpoints by 1).

With my present invention I am enabled to connect the wattmeter-needle to the battery andthe quadrants to a suitable portion of the ratio resistances, and on reversing the switch it the potential is simultaneously reversed on the needle and quadrants, as would be the caseif connected to an alternating circuit, so that the action of a reversing or alternate-current can be exactly seen and read direct from the dials. Similarly this applies likewise to the voltmeter and ammeter, respectively, wheneitherof them is connected to therequired appropriate ratio.

Further, by means of the double set of ratios any voltage within the range of the switch-box apparatus can be connected to the needle of the wattmeter and any required voltage connected to the wattmeter-quadrants simultaneously, so that these two voltages may be read off the ratios exactly, and, still further-,both voltages can be simultaneously reversed by the reversing-switch it.

As the voltage of any alternating current can be read from the voltmeter,the conditions of an alternating current both as regards pressure and current can be simultaneously reproduced by known constant voltages. Thus the wattmeter can be exactly calibrated under all conditions, and the value of any reading be exactly ascertained without reference to any scale other than a scale of marked points, reading directly, and such reproduced readings can be taken withoutletting the needle return to zero, thus securing the most exact results.

In using the apparatus let it be assumed that an alternating current is operating in the circuit in which self-inductance or capacity predominates, so that there is a power factor, in which case thediagram Fig. 4 indicates the circuit connections. In this G is the generator; V, a voltmeter; A, an am-- meter, and W a wattmeter, these three being electrostatic instruments. 0 is the connection to the needle, and p p are connections to the quadrants of the wattmeter from the ends of the resistance 0, which must have a known value and be non-inductive. pended in the circuit can thus be measured through the switch m, connected to the voltmeter V, the switch it, connected to the ammeter A, and the double set of switches oand '19, connected to the watlmeter W. If the circuit has a high pressure, a suitable non-inductive resistance P is inserted across the circuit and connections made, as in the diagram Fig.- 5, a multiplying factor being used.

The operation consists of turning the instrument switches to zero or short circuit in The watts exi each case and by the adjustment of the instruments so as to read zero on their respective scales. Then the wattmeter and voltmeter switch or switches (if separate) are so turned as to apply the pressure of the battery to the needle of the wattmeter, which is again adjusted to read zero on its scale. Next the switch is turned to apply the electromotive force of the standard cell to the quadrants of the wattmeter, causing a deflection, the amount of which is noted. The switch in the current ratio is then set at a point corresponding to the electromotive force of the standard cell, supposing, for example, one hundred volts to be across the ends of the current ratio. The quadrantswitchp is next turned so that this voltage is applied between the quadrants of the watttneter instead of that of the standard cell. If the voltage-drop across the current ratio is not one hundred volts, then the difference will be noted in the deflection of the wattmeter-needle, which requires an alteration of the resistance in series with the battery until on moving the quadrant switch from the standard cell to the current-ratio point there is no difference of deflection, when we know that the assumed one hundred volts are being applied to the wattmeter-needle and the electromotive force of the standard cell applied between the quadrants in accordance with the usual formula. The wattmeter is then calibrated at one point, and by reference to the current-ratio points in the switch-box apparatus operating by the quadrant-switch p the wattmeter can be calibrated at an equivalent number of points or its readings reproduced.

The ammeter A is shown in the diagrams Figs. etand 5 as shunted across the resistance 0 or by the instrument itself in a series of operations similar to those above described by testing the battery and obtaining an electromotive force of, say, exactly one hundred volts between the ends of the current ratio and the pressure ratio. Having in either of these two ways obtained one hundred volts across the circuit connected to a point on the voltmeter-switch 'm, Figs. 1 and 2, the voltmeter can also be calibrated throughout its scale. The three electrostatic instruments being thus calibrated, the switches in the switch-box apparatus can then be turned to the points which connect the instruments with a circuit whereon it is desired to make observations.

What I claim, and desire to secure by United States Patent, is-

1. The herein-described improved switchbox apparatus, consisting of a pressure-ratio and a current-ratio set of resistances, controlled by switches, combined with means for connecting them to a battery resistance, voltmeter, ainmeter, and wattmeter circuits, and to a standard cell, together with a reversingkey, arranged in a safety-case, substantially as described and illustrated in the drawings.

2. The herein-described improved switchboX apparatus, consisting of a pressure-ratio, and a current-ratio set of resistances, one or both of said ratios being subdivided and controlled by switches arranged and operating simultaneously upontwo portions of a resistance, substantially in the manner and for the purpose specified and shown in the drawings.

3. In a switch-box apparatus a current-ratio set of resistance-coils arranged in series, but having a diverse proportion of the whole resistance assigned to and controlled in further subdivisions by each of two or more switches, one, at least, of said switches having its apportioned resistance further divided into two equal parts and adapted to have equal portions thereof simultaneously inserted in and cut out of the circuit by the single movement of the switch-arm, substantially as and for the purpose specified and shown in the drawings.

4.'In an electric switch-box apparatus a current-ratio resistance subdivided into three unequal divisions respectively controlled by switches e, f, and 4; combined with switches and circuits respectively indicated by m, 7L, 0 and p, and a battery resistance controlled by switches t and j, substantially in'the manner and for the purpose specified and shown in the drawings.

5. In an electric switch-box apparatus, a current-ratio resistance subdivided into unequal divisions, each division controlled by a I switch, combined with a pressure ratio also controlled by one or more switches, an adjustable battery resistance, electrostatic instrument circuits and a reversing-switch,

substantially in the manner and for the purpose specified.

6. In an electric switch-box apparatus, a current-ratio resistance subdivided into unequal divisions, each controlled by a switch, combined with a wattmeter-circuit controlled by the switches 0 and 1), and a battery and standard-cell circuit, substantially as and for the purpose specified and shown in the drawings.

7. In an electric switch-box apparatus, a currentratio resistance,com bined with a pressure-ratio resistance, and a wattmeter-circuit having switches respectively controlling the needle and quadrants, substantially as and for the purpose specified and shown in the drawings.

In testimony whereof I have signed this specification in the presence of two subscribing witnesses.

GEORGE LEONARD ADDENBROOKE.

Witnesses:

WVALTER E. ROCHE, JOHN D. VENN.

Images