US761459A - System for operation of magnetic clutches. - Google Patents

Description

'No. 761,459. PATENTED MAY 31, 1904.

A. 0. EASTWOOD.

SYSTEM FOR OPERATION OF MAGNETIC GLUTOHES. I

APPLICATION rum) JAN. 14. 1904.

N0 MODEL. 3 SHEETS-SKEET 1 Ma -W006i m: non ms Pznzns co. mmo-umo. msumm'nu. u. c.

N0- 761,459. PATENTED MAY 31, 1904.

A. G. EASTWOOD.

SYSTEM FOR OPERATION OF MAGNETIC GLUTOHES.

' APPLICATION rum) JAN. 14, 1904. no MODEL. s snnnrs-snnm 2.

Wzmdw Jwmzm PATENTED MAY 31', 1904 4 A. a EASTWOOD. SYSTEM FOR OPERATION OF MAGNETIC GLUTGHES.

APPLIOATION rum) JAN. 14, 1904.

3 SHEETS-SHEET 3.

N0 M ODEL.

z o o 015mm mus co INOTO-LIYNQ. msmuaron. D. c.

UNIT D ST TE ARTHUR 0.. EASTWOOD,

Patented May 31, 1904.

or CLEVELAND, OHIO.

SYSTEM FOR OPERATION OF MAGNETIC. CLUTCHES.

SPECIFICATIONforming part of Letters Patent NOW/61,459, dated May 3 1, 1904.

Application filed January 14, 1904.

' To all whom; it may concern: Be itknown that LARTHUR (J. EASTWOOD,

a citizen of the United States, residing in Cleveland, Ohio, have invented certain Im-' provements in Systems for Operation of Magnetic"Clutches,,-of which the following is a specification. f

My, invention consists in a novel combination of apparatus for use in connection'with the operation and control of magnetic clutches,

one object of the invention being to so arrange.

, ment of apparatus such that the clutch-magnets shall be strongest at the time of completing circuit through them and while the load driven by the clutches is being accelerated. Consequently a further object is to economizev current and to avoid overheating of the clutch.

An additional object is to provide a system including a magnetic clutch in. which after a given load has been started the current holding together the two parts of the clutch is reduced to such an extent that said members will slip in the event of'an unusual or injurious load being applied to thedriven'machine.

or system.

These objects, together with other advantageous results, I attain as hereinafter set forth, reference being had to the accompanying drawings, in which Figure 1 is a View, largely diagrammatic, illustrating the apparatus and connections preferably employed in my system. Fig. 2 is a diagrammatic view illustrating a slightlymodified arrangement of the apparatus of my system. 1 Fig. 3 is a front elevation, partly in section, illustrating the construction of an improved auxiliary switch employed in the system. Fig. 4: is a side elevation of the switch shown 1n Fig. 3; and Flg. 5 is a plan v1ew, to some extent diagrammatic, illustrating 'the means by which certain of the clutch members may be driven in opposite directions.

My invention is particularly applicable to .erated by an electric or other motor. ftwen the-two magnetsand keyed to the supporting-shaft is mounted an armature-plate,= :which, while necessarily revolving with said shaft, is freeto move to a limited extentalong the same. If current be passed through the magnetizing-coil of one of the clutch-magnets, this will attract the armature and drive it by frictional contact,- so that since the clutch- Serial No. 189,028. (No model.)

. a systeminvolving. magnetic clutches which are automatically operated and particularly designed to be used for driving the reciprocating parts of such machines as metal-planers. In general such a system includes clutches;

having a pair of annular electromagnets so mounted as to revolve upon, but lndependent of, a common shaft, the magnets being driven in opposite directions by suitable gearing opmagnets are driven in opposite directions the reciprocating member of the machine may be connected to said armature, so as to be driven ineither direction, according as one or the other of the magnets is energized, and, further, the directlon of motion of said member may be reversed by switching the magnetizing-current from one clutch-magnet to the other.

In machines, such as metal-planers, the re- .versal of the movement of the platen is accomplished bymeans of dogs adjustably mounted on said platen and placed to engage a suitable switching device at each end of the stroke. magnets are usually wound with such a num-' fber of turns of wire of a certain size that they The magnetizing-coils of the clutchshall be capable of doingthework required without overheating, and in general this ne., cessitates a very large number of turns of wire.

When such a coil encircles a portion of a magnetic circuit of small reluctance, the current which will flow through the coil will not at-' ,tain its maximum. for an appreciable time after the circuit is closed on account of the self- ;induction of said coil, which, as is well known, varies as the square of the number of turns of wire in the coil.

In certain tests which I have made as much as nine seconds have elapsed before the current in the coil attained .its full value, and it will be readily understood that for such uses as those above noted this action is most objectionable.

To secure ideal operation of a clutch, the magnet should be most powerful at the instant of reversal of the direction of motion of the driven reciprocating device, both because the magnet must act throughan air-gap to move its armature along the shaft and because the friction of motion is less than that of rest. For this reason said magnet should act very powerfully on the armature until this has been caused to revolve at the same speed as said magnet. After the magnet has once gripped the armature its strength maybe very materially reduced without in any way interfering with its ability to drive the load, since the power required to be transmitted through the clutch is greatest at the instant when the movement of the reciprocating element of the driven machine is reversed, because the energy in the platen, with its load, due to their velocity, must be absorbed and the mass rapidly accelerated in a reverse direction.

By my invention the current in the magnetiZing-coil of the clutch reaches its maximum value almost simultaneously with the closing of the circuit in which it is included, and this maximum value is maintained until the platen and its load have been reversed, after which the current is automatically reduced to a minimum value. When the circuit of the magnetizing-coil is opened at the other end of the stroke of the reciprocating part, such opening occurs when a minimum current is flowing, so that there is very little, if any, arcing at the switch-contacts. My invention has a further advantage that the current in the magnetizing-coil may be so reduced after the act of reversing of the moving parts that the clutch will slip in the event of an overload on the driven machine, such as would be caused, for

example, by a tool striking a shoulder or-leading into the work. With present systems such. operation is impossible, as the clutch is necessarily designed to reverse the load be fore the current has reached half of its maximum value and as the power which must be delivered at the instant of reversal is from three to live times that required to drive the platen the power which the clutch will transmit may amount to seven to ten times that required for the actual cutting operation. It Will therefore be. seen that the clutch has the ability to transmit sufiicient power to permit of the machine being seriously damaged before slipping of the clutch would occur.

My invention contemplates the use of a comparatively small number of turns of wire in the magnetizing-coil of the clutch, such that the eifects of self-induction will be practically eliminated, and also includes a pair of auxiliary switches in addition to the usual reversing-switch, one of these switches being included 1n the circuit of the magnetizing-coil of each clutch and so constructed that the act of opening it cuts a body of resistance into circuit with the coil. When the switch is closed, this resistance is short-circuited.

The auxiliary switches preferably employed consist of electromagnets having movable cores which will be drawn into the magnetizing-eoil when suflieient current is passed through the same. In entering said coil the core strikes a plunger, and this in turn moves a switch-blade, which causes resistance to be thrown into the clutch-circuit. When the magnet-coil is dcenergized, the core will drop under the action of gravity and the switch-blade will be moved to its closed position, preferably by a spring.

Means are provided for adjusting the airgap through which the solenoid acts on the movable plunger or core, and it will be understood that there is thereby provided means for adj usting the strength of current at which said plunger will be drawn into the coil and the resistance-controlling switch actuated.

In the above drawings, A and A represent, respectively, the revolving magnets of a pair of clutches, having a longitudinally-movable armature-plate A which is keyed to the shaft a, it being understood that the gear (1/, fixed to the magnet A, is continuously driven in in one direction from any desired source of power, while the gear (4 connected to the magnet A, similarly is driven in the opposite direction. A gear a, fixed to the shaft (1, serves to transmit power to any machine or system to be operated. Current is supplied to the clutches through rings a and a in electrical connection with the windings of the clutches in the well-known manner.

One pole of the controlling-switch B is connected to one of the current-supply mains 7; and also to the segment 0 of a reversingswitch C, while a second segment, 0, of this switch is connected to the resistance-controlling switch D. Said latter switch may be broadly described as consisting of a movable blade (Z, so mounted as to be capable of bridging or electrically connecting two terminals d and (F.

A body of resistance E is connected in shunt to the blade (Z, and the terminal (l is also connected to the segment 0 of the switch (I. The terminal d of the switch 1) is connected, through the solenoid F, to the brushes (not shown) bearing on one of the rings a", and hence to the winding of the clutch-magnet A. The said solenoid is provided with a movable core f, and there is interposed between said core and the switch-blade (Z a movable bolt f, which is so proportioned as to engage and cause motion of said blade (Z under the action of the core f when this latter is drawn into the solenoid F. A spring (11 is preferably employed to retain the blade (Z in good contact with the terminal at, it being noted that in the present instance said blade is pivotally mounted upon the terminal d My preferred construction of the switch D is shown in Figs. 3 and 4, in which a frame 5 D, mounted upon the base d, of insulating,

material, servesas a support for the solenoid F. It will be seenthat the bolt f is carried by theframe D, so that as the core f is drawn into the solenoid it will strike and raise said pivot. This core is adjustably supported, so as to project into the solenoid for variable distances,by' means of a screw f which passes through a suitable opening in an extension of the frame D so that itwill be understood that the core may be set so as to be moved into the solenoid when this latter has been energized by a current of predetermined strength. 7 7

As shown in Figs. 1 .and-3, a switch D in every Way similar tothe switch D, is connected to the clutch-magnet A and to athird segment of the reversing-switch C, it being noted, however, that the solenoid in both casesis in series with the magnet-winding of one of the clutches and also in series witha re-- sistance E or E when the switches with which said bodies of resistance are in shunt are opened. I

Underoperating conditions when the switch D is closed the second supply main b is in electrical connection with the two rings (0 through which the clutch-magnets A and A c are supplied with current, and when the op- 3 5 as to connect the segments sand 0 'currentwill flow to these through the low-resistance switchblade 0?, of the switch D, through the solenoid F, the clutch-magnet A, and back, to theswitchB and the second supp1y-main. Such flow of current. will at onceresult in the ar' mature A being clutched to the magnet A practically simultaneously with the move-.

ment ofthe reversing-switch bar 0 owing to the small amount of self-induction of the Wind: ing of the clutch-magnet. The initial flow of current will be determined by the self-induction and resistance of the circuit,and the current itself Will increase very rapidly to apredetermined value, at which the bolt f of the switch D will be struck by the core f as this latter is drawn into the solenoid, thus opening the circuit between the terminals d and (F, and consequently causing the resistance E to be put in series with the solenoid and the clutch-winding. In the meantime the clutch member carrying the coil will have gripped the armature and accelerated the driven mechanism under the influence of the initial heavy current, continuing to drive said mechanism with the current reduced to such a value by the cutting in of said resistance E that the clutch will slip should any undue overload occur.

For example, under practical operation in one case the reduction of current was from a 5 maximum of ..1.5 amperes to .3of an ampere. 1

bolt, and therebyturn the blade d on its erating-lever '0 of the switch C is thrown so If, as shown in Fig.2, itlis desired to employmy improved mechanism to operate a planer, I: provide, in addition to the apparatus above noted, a pair of stop-switches g and g, placed: adjacent to the planer-table G, and also extend the handle of the reversing-switch, C, so that this will be engaged by suitably-placed dogsupon said table. As the arm 0 0i thereversing-switch is thrown over so as tobe in a po I sition midwaybetween the segments 0 and c the clutch-circuit will be opened, so that the armature A is released and the core f allowed. to drop, thereby permitting the blade 01 to be: brought in contact with the terminal at under the action of thespring 0Z so as to again cut-8o:- sthe resistance E out of the clutch-circuit; It:-

will be noted that said circuit is opened witln .minimum current flowing, and consequently; :there will be practically no arcing at the con. ,tacts of the reversing-switch. By moving the 8 5: handle of this switch so that it connects the segments 0 and c the shaft a will be operatively. coupled to the mechanismdriving the gear (0 and will consequently be turned in a direction. opposite to that in which it was turnedv under the action of the gear a, the cycle of operations passed through by the various pieces ofapparatusbeing similar to that described inthe case of the switch D and the resistance E. In Fig. 2 the reversing-switch is shown as provided with an extra pair of contacts 0*, to. which is connected one terminal of a magnetic brake H'of any desired construction, whose. second terminal, with the conductor from the rings a of the two clutches, is connected, rpp

through the stop-switches g, and g, to the main switch B. As long as the movable arm of the reversing-switch C is in any other than its central position the winding of the; magnetic brake will be energized so as to hold a weight 165 actuated bandout of engagement with a brak-, ing-surface, and it will be seen that as soon.

as current is cut off from the brake as, for. 'example, by the operation of the reversing: swit'chthe weight will operate upon the band to apply said brake, and thereby prevent fur-Y ther operation of the device. When the; clutches are driven by a direct-current shunt or, compound wound motor, the current for operating the clutch-magnets may be obtained '1 15 through conductors connected to the armatureterminals of said motor. Thus in Fig. 2 the live side of the switch B instead of being connected directly to the supply-mains will be connected to the armature-terminals of the driving-motor Z, all of the other connections of the system remaining as before described.- Some trouble has been experienced in the application of magnetic clutches to the transmission of power for operating a reciprocating device on account ot a sudden iallure of the current from such a cause as the opening of a circuit-breaker. If the machine operated .be a planer and the platen be near the end of a strokewhenthis accident occurs, the clutch 13 &

will be deenergized, and there will be no means of reversing the direction of motion of the platen when it reaches the end of its stroke. It will therefore continue to drift forward and is apt to cause considerable damage to the machine, as well as serious loss of time.

While it is possible to prevent such an accident by the use of a magnetic brake, 1 have found that by the improved arrangement indicated above and illustrated in Fig. 1 such brake is unnecessary, since should the current fail the armature of the motor will continue to revolve by virtue of its own inertia, as well as the inertia of the clutch-magnets and their attached gearing, so that the motor becomes a self-excited shunt-wound generator and will supply current for the clutch-magnets as long as the armature continues to revolve. The movement of the platen will therefore be reversed in the customary manner as long as such movement continues without danger of damage either to the machines or to the work operated upon.

I claim as my invention 1. A clutch having a winding, means for controlling the flow of current thereto and a device mechanically independent of the clutch mechanism for reducing the amount of such current after the said controlling means has been operated, substantially as described.

2. A clutch having a winding, means for controlling the flow of current thereto, and

automatically-acting means for reducing the amount of such current after the said controlling means has been operated, substantially as described.

3. The combination of a magnetic clutch, a switch for controlling the flow of current thereto, a body of resistance, and means for automatically throwing the resistance into circuit with the winding of the clutch after said circuithas been closed, substantially as described. v

4. The combination of a magnetic clutch, a body of resistance, and automatically-acting means for placing said resistance in circuit with the winding of the clutch when said clutch is energized, substantially as described.

5. The combination of a clutch having driving and driven members, means for causing said members to be held together with acertain definite force and means independent of the clutchoperating mechanism for automatically reducing said force after the two members of the clutch have been coupled, substantially as described.

6. The combination of a magnetic clutch, a controlling-switch, a body of resistance, and an auxiliary switch in shunt thereto, with a solenoid having a movable core placed to cause said auxiliary switch to be opened when the solenoid is energized, substantially as described.

7. The combination in a system for the control of magnetic clutches, of a plurality of clutches, each having an auxiliary switch, a body of resistance, and means for automatically throwing said resistance into circuit after the clutch has been energized, with means for causing either of the clutches to be supplied with current, substantially as described.

8. The combination of two electrical clutches having members driven in opposite directions, a member attached to mechanism to be driven and common to both of said driven members, a switch for controlling the flow of current to the clutches, and a device for automatically reducing the amount of current after the switch has been closed, substantially as described.

9. The combination of a magnetic clutch, a body of resistance and an automatically-acting electrical device in shunt to said body of resistance, with means for adjusting said device to operate under predetermined conditions, substantially as described.

10. The combination of an electrically-operated mechanism with a switch, a body of resistance, and a solenoid in circuit with said mechanism, said solenoid having an adjustable core placed to operate upon said switch, substantially as described.

11. The combination ofamagnetic clutch, a body of resistance and a switch in circuit with the clutch, a solenoid, a core placed to cause action of said switch, with an adjustable device for varying the distance of the core from the solenoid, substantially as described.

12. A system including a motor, magnetic clutches, each having one member revolubly connected to the motor and having their windings connected in shunt to the armature of said motor, with a reversing-switch for throwing either of the clutches into action, substantially as described.

13. A system including amiagnetic brake, a magnetic clutch electrically connected to the brake, a switch and a solenoid in circuit with tially as described.

. 14. A system including a reversing-switch, a pair of magnetic clutches each having a wind ing connected to said switch, a magnetic brake having its windings in shunt with said clutchwindings and connected to the said switch, with means in circuit with each clutch for reducing the current flowing therethrough after the reversing-switch has been operated, substantially as described.

15. A magnetic clutch having a winding of relatively low self-induction, a switch, an electrical device for reducing the flow of current through said clutch and means for operating said switch for cutting said device into and out of action, substantially as described.

16. A magnetic clutch having a magnetizing-coil of relatively low self-induction, a

switch, a body of resistance in shunt thereto,

a solenoid in circuit with the clutch-coil and means actuated by the solenoid for operating the switch, substantially as described.

17. The combination of an electric clutch, means for controlling the flow of current thereto and a device mechanically independent of the clutch mechanism for automatically varying the amount of said current after said controlling means has been operated, substantially as described.

In testimony WhereofI have signed my name to this specification in the presence of two subscribing Witnesses.

I ARTHUR C. EASTWOOD.

Witnesses:

O. W. GOM'STOOK, R. I. WRIGHT.

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