US1713304A - Reversing switch - Google Patents

Description

May 14, 1929. o. F. SHEPARD REVERSING SWITCH Filed Dec. 13,

Patented May 14, 1929.

UNITED STATES OSCAR F. SHEPARD, 0F CINCINNATI, OHIO.

. REVERSING SWITCH.

Application filed December 13, 1923. Serial No. 680,568.

An object of my invention is to provide a simple and eliicient reversing switch.

Another object of my invention is to provide a reversing switch wherein polarity of a line or a shunt across the switches may remain constant regardless of the change in direction of flow of the main line current through the operating switch mechanism.

Another object of this invention is to provide a device for starting, stopping and reversing an electric motor, wherein, when the motor is disconnected from the source of electrical supply in oreer to stop same, the field circuit of the motor remains complete and is not disrupted.

These and other objects are attained by the means described herein, and disclosed in the accompanying drawings, in which:

I Fig. 1 is a diagrammatic view of a wiring circuit having embodied within it a revers ing switch embodying my invention.

Figs. 2, 3, 4, 5 and 6 represent schematically the electrical connections and relation of the parts during torward rotation,

. open circuit, 011, transition and reverse posltions.

' mechanism 16 and the contacts 8 and 13 constitute a pair of contacts of a switch mechanism 17. The contacts 7 and 12 are adapted to be engaged by contacts 18 and 19 respectively of the switch mechanism'16. The contacts 8 and 13 are adapted to be engaged by contacts 21 and 22 of the switch mechanism 17. carried by a suitable insulating plate 23, and contacts 21 and 22 of the switch mechanism 17 are carried by a similar nonconducting plate 24. The plates 23 and 24 are carried by stems 25 and 26 respectively of the armatures 27 and 28'respectively of the switch mechanisms 16 and '17 respectively. Coils 29 and 30 control the movement of the armatures 27'a1id 28 respectively. Each of the annatnres has associated with it, a secto one brush 55 of the motor 51.

The contacts 18 and 19 are 0nd stem 31 and 32 carrying non-conducting plates 33 and 34 and carrying contacts 35, 36 and 37 and the contacts 38, 39 and 40. he contacts 19 and are connected, as are 18 and 37; 21 and 38; and 22 and 40. It should be noted that the coil 29 of the switch mechanism 16 has its one end electrically connected with the contact 39 associated with the switch mechanism 17 and that the second end of the coil 30 is connected with the contact 36 associated with the switch mechanism 16. Fixed contacts 41, 42 and 43 are provided for engagement by the contacts 35, 36 and 37 respectively of the switch mechanism 16 and switch mechanism 17 is provided with the contacts 38, 39 and 40 for engagement with contacts 44, and 46 respectively. Normally the contacts 35, 36 and 37 engage the contacts 41, 42 and 43 respectively, and contacts 38, 39 and 40 engage contacts 44, 45 and 46 respectively. This may be accomplished in any suitable manner such as by mounting the switch mechanisms in a vertical plane so that gravity will normally return the parts to their normal positions or else suitable yielding means such as 47 may be employed for yieldingly retaining the parts in said relationship. Contacts 43 and 44 are electrically connected by'means of the resistance element 48 that, together. with the resistance element 49, constitutes a dynamic braking resistance. The contacts 41 and 46 are electrically connected by way of the resistance element 49. The contacts 43 and. 46 are connected through the field 50 of the motor 51. The conductor 52 connecting the contacts 18 and 37 of the switch mechanism 16 is connected by means of the conductor 53 with the conductor 54 connectingcontacts22 and 40 of the switch mechanism 17. The conductor 53 extends The second. brush 56 of the motor 51 is electrically connected by means of the conductor 57 with the conductor 58 connecting contacts 21 and 38 of the switch mechanism 17 and with conductor 59 electrically connecting the contacts 19 and 35 of the switch mechanism 16. The conductors 3 and 4 leading from the control device 2 are electrically connected with the contacts 42 and 45 respectively of the switch mechanisms 16 and 17, respectively. In the embodiment of my invention as shown herein it is essential to provide a means that will permit closing of the shunt eirciiits through the electremagnets of respectiveswitch mechanisms 16 and 17 with the movement of the lever 60. This may be accomplished in any suitable manner such as by directly connecting the'conductor 62 with the conductor 11 as shown at 63. e i As is known to those skilled in the art, a field after being built up by a flow of current, will die down gradually when the current is shut off. This is in reality a short time interval. However without the . resistances 18 and 49 there would be what is commonly known as dynamic shock upon the armature, The resistances 48 and 49 however are in circuit during this interval and efi'ect a momentary dynamic braking action upon the armature during the in-I terval of field discharge Thus these members 48 and49 constitute dynamic braking resistances.

' actuated for bringing the contacts 18 and 19.

The operation of my device is as follows: Assuming that the lever or handle 60 of the control device 2 is actuated for completing a circuit through shunt wire 61, through conductor 3, contacts v415, 39, coil 29 and conductors 62, 63 and 11, the armature 27 is i into en a ement with the contacts 7 and 12 respectively, thereby completing the main circuit as follows: positive conductor 1, the contact 7, contact 18, conductor 52, conductor 53, brush 55, motor51, brush 56,c onduc tor 57, conductor 59, contact 19, contact 12, conductor 11 toconductor .9. The field circuit established is as tollowsqconductor 1,,

contact 7 contact 18, conductor 52, conductor 53, conductor 54, contact .elO, contact 416,

r the shunt, including conductors 61. and 3, *and for establishing a circuit throughlthe j field 50, cont-act 4C3, resistance a8, contact 44,

contact 38, conductor 58, conductor'57, cone ductor 59, contact 19, contact 12, conductor illto conductor 9. Should-the lever now be moved for breaking the circuitthrough conductor 4, the armature 27 would be returned to its'normal position andthe armature 28 would be actuated for bringing the contacts 21 and 22 into engagement with the contacts 8 and 13 respectively. The motor circuit would then be as follows conductor 1, conductor 6, contact 8, contact 21, conduc- :tor 58, conductor 57, brush56, motor v51,

brush 55, conductor 53, conductor 5st,- contact 22, contact lS, conductor'lO to conductor 9. It will be observed that the flow of current through the motor 51 has been reversed.

a The field circuit is as follows: conductor 1, 7 contact 8, contact 21, conductor 58, conduc tor 57, conductor 59, contact 35, contact 41,

' resistance 49, contact 46, field50, contact 43,

contact 37, conductor 52, conductor 53, conductor 54, contact 22, contact'18, conductor 10 to conductor 9. It shouldbe noted that thefiow of current through the field 50 is 1 the same as when the switch 16 was first actuated.

The contacts 36, 42 and 39, 4:5 constitute an electrical interlock that prevents both, main switches being operated at the same time. A mechanical interlock, manually operated could be employed if desired, in lieu of the electrically operated interlock shown.

-What I claim is:

1. A reversing switch for a motor comprising two double throw double pole switches, each switch comprising two pairs of fixed contacts and, a movable member fixed contacts of each switch, an electrical circuit including .a motor, the motor being adapted to be operated in reverse directions carrying contacts adapted to engage the s by the switches, the motor armature being connected with the contacts carried by the movable member of each switch, the motor field being connected with the one pair of fixed contacts of each switch, and dynamic braking resistances connecting the last mentioned pairs of fixed contacts, such that on the running of the motor one section of the resistance is in series with the field circuit and on stopping of the motor the, field circuit is shunted upon itself and the armature isshorted through the resistances in parallel, 7

whereby the field circuit remains complete upon actuation of the switches for reversing the motor. i

.2. In a device of the class described the combination of a pair of switch mechanisms each comprising two sets of relatively fixed contacts, a relatively movable sw1tcl1 ele-.

'thevarious contacts, a dynamic braking re sistance interposed between the second mentioned sets of relatively fixed contacts of said pair of switch mechanisms,"a pairbt conductors connected with the relatively movable contacts of both switchmechanisms,

the switchniechanisms and contacts thereof being arranged to reverse the flow of current over said pair'of conductors, means for '12s selectively energizing the electro-magnetic. control means and a conductor connected namic braking resistance into electrical communication with said last mentioned conductor without changing the direction of flow of current through said conductor.

3. A reversing switch for a motor comprising two double throw double pole switches, each switch comprising two pairs of fixed contacts and a movable member adapted to engage each pair of fixed contacts, a motor comprising an armature winding electrically connected with the movable member of each switch and adapted to have current directed therethrough in reversed directions by said switches, a source of electrical supply electrically connected to one pair of fixed contacts of each switch, the motor having a field connected with the other pair of fixed contacts of each switch, and a dynamic braking resistance connecting the last mentioned fixed contacts whereby reversing of the motor will not disrupt the field.

4. In combination a source of electric supply, a motor comprising an armature winding and a field winding, a switch mechanism including dynamic braking resistance and adapted for directing current through the armature winding in opposite directions and through the field winding in one direction only and further adapted, when the motor is disconnected from the source of electric supply, to include said braking resistance in a closed armature circuit and to short circuit the field winding upon itself.

5. In a. device of the class described the combination of a source of electrical supply, a motor comprising an armature winding and a field winding, a switch mechanism electrically connecting the motor and the source of electric supply for reversing the flow of current to the armature winding and providing a uni-directional flow of current to the field winding, a starting resistance connected with the armature winding and means comprising dynamic braking resistance associated with the switch mechanism and field winding for completing a closed field circuit at all times and serving to short braking resistance, and switch means whereby the resistance is simultaneously disconnected from the armature winding and included in the field winding and providing for alternate connection in a source of electrical supply to effect at one time a flow of current through the armature and field windings in one direction and at other times to reverse the direction of current flow through one of the windings, the direction of current flow through the other of said windings remaining unchanged.

7. In a device of the class described the combination of a motor comprising a field winding and an armature winding, a source of electrical supply, a pair of electromag netic switches, a pair of resistance elements, means responsive to the energization of one of the switches to connect said field winding and one of said resistance elements in series therewith across the armature winding and across the source of electrical supply for providing forward rotation of the motor, means responsive to the energization of the other of said switches to connect the field winding and the other of said resistance elements across said armature winding and across said source of electrical supply for reverse rotation of the motor, and means responsive to the deenergization of both of the said switches to short circuit the field winding and to connect both of the said resistance elements across the armature for dynamic braking.

In testimony whereof, I have hereunto subscribed my name this 7th day of December, 1923.

OSCAR F. SHEPARD.

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