US1770723A - Electrical apparatus - Google Patents

Description

July 15, 1930. c. w. wYMAN ELECTRICAL APPARATUS Filed May 16, 1919 Patented July 15, 1930 UNITED STATES PATENT OFFICE CHARLES W. WYMAN, OF CLAREMONT, NEW HAMPSHIRE, ASSIGNOR TO SULLIVAN MACHINERY COMPANY, A CORPORATION OF MASSACHUSETTS I ELECTRICAL APPARATUS Application filed Kay 16,

This invention relates to electrical appara tus and more especially to a controlling mechanism therefor.

One object of the present invention is to provide an improved controlling mechanism. A further object of my invention is to provide an improved reversing means for reversing a current flow in an electrical system. Another object of the present invention is to provide an improved reversing mechanism for reversing a current in a motor, and for preventing the changing of the direction of current flow until the rotor thereof has practical- 1y stopped moving, thereby preventing a blowing or burning out of any part of the device due to the throwing of a reverse switch while the rotor is rotating at a relatively high speed. Still another object of the present invention is to provide a simple and inexpensive reversing mechanism which may be easily manufactured and installed on controllers now commonly used. These and other objects and advantages of my improved construction will, however, hereinafter more fully appear.

In the accompanying drawing, I have shown for purposes of illustration one embodiment which my invention may assume in practice.

In this drawing,

Fig. 1 is a side elevation of my improved device, part thereof being shown in section.

Fig. 2 is a sectional plan view thereof taken substantially on the line 2-2.

Fig. 3 is a wiring diagram of the controlling system.

In this illustrative construction, I have shown my invention applied to a common form of reversing switch which has a back plate 1, and a front plate 2 preferably carried by the back plate in spaced relation thereto by a pipe separator 3 and a bolt 4 passing therethrough, as shown in Fig. 1. Mounted on the front plate 2 is a controlling handle 5 which controls the reversing switch through a short shaft 6 rotatably mounted on the front late and extending there-through to a tang preferably rigidly mounted on the shaft 6. This tang enters a transverse slot 8 formed in the combined cover and movable switch member 9 of a reverse box 10, which com- 1919. Serial No. 297,532.

prises the fixed and movable contacts, not necessary to show herein. A spring 11 mounted between a .part of the tank 7 and the member 9 keeps the latter and the usual movable contacts thereof in proper relative position to the usual fixed contacts within the switch box 10. The handle 5, as is common in devices of this type, has a throw of 90 to reverse the current of the electrical apparatus, the limiting positions of the handle being determined by stops 12 and 13 which abut alternately against a fixed stop shown at 14 (Fig. 2), which may, if desired, be carriedon the underside of the face plate 2. In this usual form of reversing mechanism, when the handle 5 is in the position shown in Fig. 1 with the movable stop 12 in contact with the fixed stop 14, the current is flowing in one direction through an electrical apparatus such as a motor. When it is desired to re verse the current, the handle 5 is moved through an angle of 90 to bring the stop 13 against the abutment 14 and change the relative position of the movable contacts in the switch box 10 with relation to the fixed contacts carried therein.

In the use of heavy currents for driving electrical apparatus, such as motors, it is a common practice when reversing a motor to throw off the current by manipulation of a controlling arm shown diagrammatically at 15 in Fig. 3, reverse the circuit through a reversing mechanism, such as has just been described, and then throw the current on again as by moving the controlling arm 15 to the left. The usual means for controlling electrical apparatus is open to the serious objection that the rotor of a motor does not stop immediately after the current is thrown off but continues to revolve and to generate a current in the motor windings, proportional to the speed of rotation. If while the rotor is still revolving, the reverse switch is thrown in the reverse direction, the rotor or armature is short circuited and the contacts or wiring in the reversing switch or parts of the motor may be burned out, rendering the apparatus useless until these parts are renewed. This burning out of parts of the motor occurs very often in the use of mining machinery where currents of relatively high ampera and voltage are used, and where unskille operators are employed to operate the electrically driven mining apparatus. To overcome this difiiculty, I preferably provide means herein shown as mounted adjacent the reversing mechanism for preventing the operation of the latter until the rotation of the motor armature has completely stopped or the armature is rotating so slowly that the current developed thereby is relatively small. For this purpose, I preferably provide a shunt circuit 16 having a shunt field winding 17 wound wlth the series field 18 of a motor having an armature or rotor 18', in such a manner that when a current is sent through the series winding 18, a current is also sent in the same direction through the shunt field, this current in the shunt field energizing an electro-responsive device herein the form of a magnet 19 which acts on one end of a lever 20 preferably pivoted intermediate the ends thereof as shown at 21. This lever or pawl 20 has an upturned end 22 adapted to contact with either side of a stop 23 carried by the shaft 6. Since the magnet 19 is energized as long as a current is flowing in the shunt circuit 16, the pawl 20 will be held in operative position to engage the upturned end 22 thereof with the stop 23 and thereby prevent the operation of the reverse switch to reverse the current while the current is on. When the controller arm 15 is thrown to its ofi'positiomthe reverse switch will be retained in the position in which it has been operating during the flow of the current until the current flow in the shunt circuit 16 ceases entirely or reaches a predetermined minimum at which no harm can be done the apparatus, for the armature of the rotor will generate a current in the shunt winding and magnet due to its momentum and to the fact that the reverse switch completes the circuit of the shunt winding. I also provide a pawl releasing means herein shown as a resilient spring 24 preferably mounted coaxially with the electrical magnet. this spring normally pressing upward against one end of the lever 20 to depress the other end from engaging position with the stop 23. The residual magnetism of the magnet will tend to hold the lever 20 in look ing position after the current has stopped flowing in the shunt field 17 and to overcome this, I preferably mount at the under side of the right end of the pawl 20 (see Figs. 1 and 2) a copper or other nonmagnetic means which holds the pivoted pawl in spaced relation to the magnet to render the relatively weak lines of force of the residual magnetism ineffective to resist the action of the spring. If desired, the retaining means or the spring or both may be done away with and the left end of the arm may be weighted sufiiciently to cause the arm to swing to an inoperative position as shown in dotted lines in Fig. 1.

But since time is lost in waiting for the residual magnetism in the magnet to die out and since it is preferable to provide a positive and easily calibrated means for moving the pawl to inoperative (position, I preferably provide the spring an retaining means as shown in order that the switch may be thrown to reverse the current as soon as the armature movement has slowed down to a speed at which the current generated thereby will not cause disastrous effects to the apparatus; when the reverse switch is thrown.

It is thus seen that I have provided a simple and inexpensive means for preventing the disastrous results which occur in electrical apparatus when a reverse switch is thrown before certain parts of the electrical apparatus have stopped their previous direction of motion. It is further seen that I have provided an improved means which is easily applicable to controllers now commonly used for positively locking the reversing mechanism thereof against movement to reversed position until the current has been thrown 011?. It will further be seen that this apparatus is very easily and cheaply constructed, is not liable to get out of repair, and may be easily adjusted to vary its time of operation relative to the currents generated or to the speed of the moving parts.

While I have in this application specifically described one embodiment which my invention may assume in practice, it is to be understood that this form is shown for illustrative purposes only and that the invention may be modified and embodied in other forms without departing from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In an electrical apparatus, a reverse switch, manual operating means therefor, and electro-responsive means for preventing operation of the reverse switch operating means at any time during current flow.

2. In an electrical apparatus comprising a motor, a manually operable reverse switch, and automatic means 'for preventing any movement of the reverse switch while the motor has motion above a predetermined speed 3. In an electrical controlling apparatus for a motor provided with a shunt field, a current controller, a manually operable reversing mechanism therein, and means for mechanically preventing the operation of the reversing mechanism when current is flowing in said apparatus.

4. In an electrical apparatus, a motor having a rotor and a shunt field winding, a reverse switch for said motor, and mechanical means controlled by the current flow in said shunt field for controlling operation of said reverse switch, said current flow producing only a single effect upon said mechanical means.

5. An electrical apparatus comprising a motor having a series winding, a shunt winding and a rotor, a reverse switch whose movements in opposite directions effect. reversing, said shunt. and series windings being connected in a mutual relation not affected by the reverse switch, and electro-responsive means controlled by current flow in the shunt winding for preventing operation of the reverse switch while the rotor is in motion.

6. An electrical apparatus comprising a motor having a series winding, a shunt winding and a rotor, said shunt and series windings being always connected in the same relation with respect to each other, magnetic means controlled by current in the shunt winding, a reverse switch whose movements in opposite directions effect reversing, and means controlled by said magnet for preventing operation of said reverse switch while the rotor is in motion.

7. An electrical apparatus comprising a motor having a series winding, a shunt winding and a rotor, electro-responsive means in circuit with the shunt winding, a reverse switch having a stop thereon, and means controlled by the electro-responsive means and cooperating with the stop on the reverse switch to prevent operation of the reverse switch while a predetermined current is flowing in the shunt winding.

8. An electrical apparatus comprising a motor having a series winding, a shunt winding and a rotor, an eleetro-responsivemeans in circuit with the shunt winding, a ])l"0t6d member cont-rolled by said means, means for normally retaining said member in an inoperative position, and means controlled by said member for reversing a current through the rotor.

9. An electrical apparatus comprising a motor having a series winding, a shunt winding and a rotor, a magnet in circuit with the shunt winding, a pivoted member controlled by said magnet, a non-magnetic member between the pivoted member and. the magnet, means for normally retaining saidpivoted member in an inoperative position, and means controlled by said member for reversing a current through the rotor.

10. In an electrical apparatus comprising a motor having a shunt field, a reverse switch CHARLES W. VVYMAN.

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