US771968A - Electrostatic instrument. - Google Patents

Description

PATENTED OCT. 11, 1904.

F. H. BOWMAN. ELECTROSTATIC INSTRUMENT.

APPLICATION FILED NOV.25,1903.

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UNITED STATES Patented October 11, 1904.

PATENT Error...

FRANCIS H. BOWMAN, OF LYNN, MASSACHUSETTS, ASSIGNOR TO GEN- ERAL ELECTRIC COMPANY, A CORPORATION OF NEIV YORK.

ELECTROSTATIC INSTRUMENT.

SPECIFICATION forming part of Letters Patent No. 771,968, dated October 11, 1904. Application filed November 25, 1903. Serial No. 182,624. (No model.)

To all whom it may concern.-

Be it known that I, FEANoIs H. BOWMAN, a citizen of the United States, residing at Lynn, county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Electrostatic Instruments, of which the following is a specification.

This invention relates to an electrostatic ground-detector, an instrument for indicating the occurrence of a ground and the line which is grounded, though the invention is applicable to other electrostatic instruments, such as voltmeters.

The object of the invention is to provide an instrument which can readily be adapted for use on circuits differing widely in voltage and which shall be more compact than those now in use.

Electrostatic instruments have been commonly constructed with a pivoted vane mounted to rotate between pairs of stationary conducting plates or quadrantsf the quadrants of each pair being connected to one of the several lines or to ground and mounted with one quadrant above and one below the moving vane. In these instruments the force exerted on the movable vane tending to turn it on its pivot depends on the distance between the vane and the stationary quadrants and the potential of the quadrants. As an electrostatic ground detector is not required to give an indication to an exact scale, it may be used without change on circuits differing in voltage over a considerable range; but when an instrument of this type has been constructed for use on a comparatively high-voltage circuit it cannot be used on a low-voltage circuit, as the distance between the quadrants of any pair, or, more correctly, between each quadrant and the moving vane, is so great that the torque developed in the moving element is insufiieient to give a positive indication. I have therefore provided an electrostatic instrument having auxiliary quadrants in addition to the pairsof stationary quadrants which may be readily mounted between the main quadrants and electrically connected thereto to increase the area of active surface and reduce the air-space between the parts rod of resistance material, in the connectionsbetween the several quadrants and the lines and ground, so that only a small current would pass if a connection from one pair of quadrants to another were closed by a breakage or the formation of an are. I effect a further improvement in the construction of the instrument by mounting these resistancerods within the studs by which connection is made to the quadrants and arranging the rods to be'readily removable from the studs. By this construction the instrument occupies less space, presents a neater appearance, and the resistances may be quickly removed and new ones inserted.

My invention therefore comprises an electrostatic instrument having auxiliary conducting surfaces or quadrants removably mounted in cooperative relation to the-movable vane to increase the sensitiveness of the instrument.

It also comprises an electrostatic instrument having resistances removably mounted in the studs by which connection is made to the instrument.

It further comprises other novel features which will be more fully described hereinafter and definitely indicated in the appended claims.

In the accompanyingdrawings, which illustrate one embodiment of my invention, Figure 1 is a top view, broken away in part, of an electrostatic grounddetector. Fig. 2 is a section'on line 2 2 of Fig. 1, one of the studs being shown in section. Fig. 3 is a perspective view of a pair of the auxiliary quadrants, and Fig. 4: is a diagrammatic view of the electrical connections.

The instrument is inclosed in a metallic casing 1, having a glass front 2 and mounted on 6, carrying a vane 7 is pivotally mounted at that center on a frame 8, supported from the back of the casing. Shaft 6 carries a needle or indicator 9, mounted to sweep over a scale 10, supported from the back of the casing by a post 11, to indicate by its deflection the condition of the electrostatic surfaces which control the moving vane 7 An adjustable counterweight may be provided on shaft 6 to normally center the indicator with relation to the dial, and two light springs 12 12 may also be provided, as shown in Figs. 1 and 2, to prevent excessive Vibration of the indicator. A more detailed description of these parts is not considered necessary, as they form no part of my invention.

The electrical connection to the quadrants is made through the studs or posts 4, by which they are supported. As shown in Fig. 2, the two quadrants of each pair are securely held on the ends of a metallic rod 13, having a threaded extension 14, which screws into a metallic block 15. This block fits within a bushing 16, of wood, rubber, or other insulating material, which extends through an opening in the back of the casing and is provided with a flange which engages the casing. The portion 'of bushing 16 within the casing is covered with a cap 17, also of wood or rubber, corrugated to increase its surface. The stud 4 is also corrugated, as shown, and its end fits into the v bushing 16. This stud is provided with a central opening in the end of which a metallic rod 18 is secured by a setscrew or in any other suitable manner. The end of rod 18 is threaded and screws into the opening in block 15 to secure the post in position. At its other end stud 4 is provided with a cap 19, interiorly threaded to receive a plug 20, which has a threaded extension carrying nuts 21, between which the connectingwire is held. Within the opening in stud 4 is a spring 22, soldered at one end to plug 20 and at the other end to a metallic button 23. Also within this casing is a high-resistance rod 24, preferably carbon. Spring 22 presses the metallic button 23 into firm engagement with one end of the rod 24 and holds the other end of the rod tightly against the metallic rod 18, insuring good electrical connection between the plug 20 and the quadrants 5, supported on the stud. To remove the resistance-rod 24 in order to replace it with a rod differing in resistance, the plug 20 is withdrawn from cap 19, carrying with it spring 22 and button 23. The resistance rod will then drop by gravity through the opening in stud 4, or the stud itself may be withdrawn by unscrewing rod 18 from block 15.

A ground-detector as thus constructed can be used on circuits varying in voltage over a considerable range; but to adapt the instrument for use on a circuit of much lower voltage I provide auxiliary quadrants 25, which are mounted between the quadrants 5 and electrically connected thereto to increase the area of active surface and decrease the distance between the conducting-surfaces connected to line and ground and the moving vane. As shown in Fig. 3, this adapter consists of a pair of quadrants 25, corresponding in shape to the quadrants 5 and rigidly mounted on a curved piece 26, which fits on post 13 and is tapped to receive a screw 27, by which the adapter is mounted in place on post 13 and electrically connected thereto. The distance between the electrically-charged parts and the moving vane 7 being thus decreased and the area of these parts increased, the instrument is rendered more sensitive, and the construction permits removing the auxiliary quadrants quickly in case it is again desired to use the instrument on the high-voltage system.

The electrical connections to the instrument are shown diagrammatically in Fig. 4. The upper pairs of quadrants are connected to the lines, as shown, and the lower pairs are connected together by the strip 28 and to ground, all connections being made through the studs or posts 4.

I have described herein a ground-detector for use on single-phase circuits; but it is obvious that the improvements are equally applicable to polyphase electrostatic ground-dedectors and to other electrostatic instruments.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. An electrostatic instrument having conducting-surfaces, a pivoted vane, and auxiliary conducting-surfaces removably mounted in cooperative relation to the moving vane.

2. An electrostatic instrument comprising two confronting conducting-surfaces forming the fixed and movable members of the instrument, and means for varying the area of active surface.

3. An electrostatic instrument having conducting-surfaces, a pivoted vane, and auxiliary conducting-surfaces removably mounted between said conducting-surfaces and the moving vane.

4. An electrostatic instrument having conducting-surfaces arranged in pairs, a pivoted vane, and auxiliary conducting-surfaces removably mounted in cooperative relation to the moving vane and in electrical connection with a pair of said conducting-surfaces.

5. An electrostatic instrument having conducting-surfaces arranged in pairs, a pivoted vane, and pairs of auxiliary conducting-surfaces, each pair removably mounted between the conducting-surfaces of one of said pairs and electrically connected therewith.

6. An electrostatic instrument having conducting-surfaces arranged in pairs, a metallic post supporting each pair of surfaces and electrically connecting them, a pivoted vane, and auxiliary conductings-urfaces removably mounted on said posts.

7 An electrostatic instrument having conducting-surfaces arranged in pairs, a metallic post supporting each pair of surfaces and electrically connecting them, a pivoted vane, and a pair of auxiliary conducting-surfaces removably mounted on each post between the conducting-surfaces supported thereon.

8. In an electrostatic instrument, a pair of conducting-surfaces, a metallic post to which said surfaces are secured and by which they are electrically connected, a pair of auxiliary conducting-surfaces, and a metallic supporting member carrying said auxiliary surfaces and removably mounted on said posts.

9. Inan electrical instrument, a stud through which electrical connection is made to the instrument, and a resistance in said connection plurality of conducting-surfaces, studs of insulating material supporting said surfaces, each stud having a longitudinal opening therein,and a removable resistance in the opening in each of said studs in electrical connection with the conducting-surface supported thereon.

13. In an electrostatic instrument, a conducting-surface, astud of insulating material supporting the same, having an opening therein, a metallic piece held in said opening at one end in electrical connection with said conductingsurface, a resistance in said opening, and a spring arranged to press the resistance against said metallic piece.

14:- In an electrostatic instrument, a conducting-surface, a stud of insulating material supporting the same, having an opening therein, a metallic piece held in said opening at one end in electrical connection with said conductingsurface, a resistance in said opening, and a spring in electrical connection with said resistance and arranged to press it against said metallic piece.

15. In an electrostatic instrument, a stud of insulating material, a conducting surface mounted thereon, an auxiliary conductingsurface removably mounted in electrical connection with said surface, and aresistance inclosed within said stud and electrically connected with said conducting-surfaces.

In witness whereof I have hereunto set my hand this 23d day of November, 1903.

FRANCIS H. BOWVMAN.

Witnesses:

DUGALD McK. McKILLor, JOHN J. WALKER.

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