US543855A

US543855A - Francis napier denison

Info

Publication number: US543855A
Authority: US
Publication date: 1895-08-06
Anticipated expiration: 1912-08-06

Description

(No Model.)

F. N. DENISON. SHORT OIROUITING DEVICE FOR STOPPING DENTAL MOTORS.

No. 543,855. Patented Aug.6,1895.

UNITED STATES PATENT OFFICE.

FRANCIS NAPIER DENISON, OF TORONTO, CANADA.

SHORT-CIRCUITING DEVICE FOR STOPPING DENTAL MOTORS.

SPECIFICATION forming part of Letters Patent No. 543,855, dated August 6, 1895.

7 Application filed October 9, 1894. Serial No. 625,326. (No model.)

To aZZ whom it may concern:

Be it known that I, FRANCIS NAPIER DENI- SON, of the city of Toronto, in the county of York, in the Province of Ontario, Canada, have invented certain new and useful Improvements in short Oircuiting Devices for Stopping Dental Motors, of which the following is a specification.

My invention relates to a short-circuiting device for the instantaneous stoppage of an electric motor more particularly adapted for running a dental engine, and referring particularly to a former application of mine for improvements in dental-motor outfits, filed on the 26th day of May, 1894., under Serial No. 512,537, in which a peculiar construction 0 foot-switch is used.

The object of the invention is to provide means for short-circuiting the armature of the motor no matter at what rate of. speed the motor armature-shaft may be rotating, so as to thereby stop the shaft instantaneously without the necessity of employing any means to decrease the speed of rotation of the armature; and it consists essentially of two contact-plates, preferably arc-shaped in form, insulated from the base-plate of the switch and each connected to the armature of the motor, but separated from each other, and a spring contact-plate connected to the bottom of the toe-plug of the pedal of the foot-switch, which plug is of insulating material, this contactplate being arranged, when the heel of the pedal of the foot-switch is depressed, to bridge the contact-plates and thus short-circuit the armature no matter into what position the toe may be swung for the purpose of speeding the shaft of the motor, the foot-switch being otherwise constructed as described in my former application above referred to, with the exception that there is no provision made for operating the brake therein provided, which brake, by my present device, is entirely dispensed with.

Figure 1 represents a view, partially in perspective and partially diagrammatic, showing the footswitch, wiring, motor, hand-switch, shunt-field, and connections, the foot-switch being shown in an enlarged perspective view, a portion of the plate or frame of the switch being broken away. Fig. 2 is a plan View of the rheostat inverted.

For the purpose of clearly illustrating my invention I shall first describe the major portion of the foot-switch in detail, as in my former applioatiomand in so doing will point out the difference in construction necessary to accomplish the present object I have in view.

U is the base plate of the foot-switch, which is made hollow, as shown,andV is the pedal, which is stiffly pivoted, swiveled, and arranged as described in my former application.

U U are hollow stop-pins attached to or forming part of the base-plate U.

W is a bar of insulating material secured to the bottom of thebase-plate U. A great deal of the bar W is broken away, so as to exhibit details of construction.

X is a bar of insulating material pivoted at the center by the screw-pin m to the bar V.

0a m are pins which are secured on the ends of the bar X. The pins as 00 extend rearwardly into the slots m 00 formed at the bottom of the plungers X X The plungers X X are preferably provided with convex pushing-caps 00 as".

V is a downwardly-extending plug of insulating material secured to the forward end of, the pedal. The plug V is surrounded at the top by a ring V of insulating material, which is designed to limit the downward movement of the plug.

0 is a boss formed underneath the heel portion of the pedal V. The boss 0 is provided with a rubber cushion V which is designed to limit the downward movement of the heel portion of the pedal.

Y Y are contact-plates, preferably areshaped, which are secured to the bottom of the base-plate U and are insulated from it and eachother by the plate Y.

V is a spring contact-plate secured on thereduced lower end of the plug V by a nut 11 of insulating material. V is a spring contact-plate rigidly secured at the bottom of the insulating-plug V by the screw o It will be seen that the plates V and V are insulated from one another.

The spring-plate V is normally held in contact with the plates Y Y when the motor is at rest, and the plate V is held out of contact with one of the plates Z of the fiat rheostat Z, which is situated beneath the base-plate U,

except when the foot-switch is pressed at the toe to throwin the motor. The plates Z are separated from each other and are insulated from the rheostat by the plate Z".

Z are the bindingposts of the rheostat, which extend through the insulating-plate into the rheostat. There is one bindingpost for each plate, and the posts are connected to the plates by the wires 2 'w w are contact-blocks secured at one end of the bar l/V, and 10 10 to are bars flush with the inner side of the bar.

X X are contact-plates secured to the front side of the pivoted bar X. The plates X K have at one end the spring ends X, which are continuously held in contact with the contact-blocks w w secured to the bar NV, and at the other spring ends X X, which are designed to be respectively brought in contact with the bars 10 10 or w 10 this depending upon which of the plungers X or X is pressed down. The rheostat above mentioned, in this instance, as indicated in Fig. 2, has the greatest amount of resistance at the right-hand side, and the resistance decreases from right to left, the left-hand binding-post having no resistance at all.

The left-hand binding-post Z is connected by the wire 2 to the contact-bar w". The bar 10 is connected to the bar to by the wire 2 \V \V \V are binding-posts of the 1notor and switchboard circuits which are secured in the bottom of the bar WV.

2 2 are wires connecting the contact-plate Y with the binding-post \V and W 3 is a wire connecting the wire 2 and contact-plate w with the binding-post W.

4 is a wire connecting the contact-block to with the binding-post WV.

5 is a Wire connecting the contact-block to with the binding-post W 6 is a wire connected at one end to the screw and consequently to the contact-plate V and extending up through the insulating-pin V, underneath the pedal, through the opening 11 down through the hollow pin V, as indicated by dotted lines, forward to the bindingpost WV? 7 is the positive wire through which the curreutpasses ordinarily when the foot-switch is not thrown in, through the wire 9, shunt-lield 10, wire 11, and back by the negative wire 12.

\Vhen the forward end of the pedal of the switch is pressed down the circuit is completed and passes through the positive wire 7 into the binding-post V thence by the wire (3 to and through the insulating-plug v, contactplate V one of the plates .2 of the rheostat, through the rheostat finally on the Wire to the binding-post Z at the left-hand side of the rheostat, the wire ,2" to the contact-bar w, thence by the contact-plate X to the contactblock to, thence by the wire 4 to the bindingpost XV, thence by the wire 13 to the motor, through the motor, and by the Wire 1 1 back to the binding-post W from the binding-post W by the wire 5, to the contact-block w,

thence by the contact-plate X to the contactbar to, thence by the wire 3 to the bindingpost W, thence by the wire 12 back to, through, and to the switchboard J. The course above described is that shown when the plunger X is pressed down and the bar X in the position shown.

It will of course be understood that the direction of rotation of armatureshaft will be reversed, as in my former application, and that the nearer the pedal is swung to the left- ,hand side of the figure, so as to bring the contact-plate V upon the plates nearer the left-hand side, the less the resistance will he (see Fig. 2) and consequently the greater the speed of the motor.

It will now be seen that in order to produce a short circuit through the armature ot' the motor and stop the rotation of the armatureshaft, the heel of the pedal V may be pressed down so as to bring the contact-plate V upwardly out of contact with the plates Z, thereby throwing the current entirely out of the foot-switch. The spring contact-plate V howeveryis brought against the contact-plates Y Y, so as to bridge them, and an induced current will be produced in the armature shortcircuit through the wires l i, binding-post W wire 2, plate Y, contact-plate V plate Y, wire 2, binding-post \V, and wire 13. It will thus be seen that the motor will be really acting as a dynamo for the time being and that an instant stoppage of the armatureshaft will be effected.

By means of the short-circuiting device above described the instant stoppage of armature-shaft can be eileeted in the same time at the highest speed as well as at the slowest speed. In my device it will also be seen that owing to the slow speed of armature when running at its maximum the short-circuiting of armature can be effected with the fully-mag netized field, as the induced current in the armature has not time to rise to dangerouspio portions on account of the armature coming to rest instantaneously.

That I claim as my invention is 1. The combination with a motor having a shunt field and circuit completed through a foot switch as specified and the foot switch pedal pivoted and swiveled as specified and having a plug of insulating material extending downwardly from the toe portion through which runs the main circuit wire to the spring contact plate designed to be movable upon the plates of a resistance coil, so as to vary the amount of current through the main circuit and consequently the rate of speed of the 1uotor, of two arc-shaped contact plates insulated from each other and each connected to the poles of the armature and a spring contact plate secured near the bottom of the toe plug of the pedal, insulated from the spring contact plate movable upon the plates of the resistance coil, and so arranged that when the heel of the pedal is pressed down such contact spring will be brought into sliding contact with the arc-shaped plates so as to bridge them as and for the purpose specified.

2. In combination with the motor havinga shunt field and a circuit, a foot switch interposed in said circuit and comprising a hollow base plate having a rheostat beneath the same, the series of contacts connecting therewith, the are shaped contact plates connected with the poles of the armature, and the foot lever 10 pivoted to swing both vertically and laterally,

and having a contact arm for engaging the said series of contacts as the pedal is swung laterally, and a second contact arm for connecting the two arc shaped plates as the pedal is swung vertically, substantially as de- 15 scribed.

FRANCIS NAPIER DENISON.

Witnesses:

B. BOYD, II. H. YOUNG.