US2465332A - Reversing switch control of press machine motors - Google Patents

Description

March 22, 1949. P. WITTE 2,465,332

REVERSING SWITCH CONTROL OF PRESS MACHINE MOTORS Filed March 16, 1946 A TTL RNE Y Patented Mar. 22, 1949 A[TED -REVERSING SWITCH CONTROL OF PRESS MACHINE MOTORS `Paul VWitte, Philadelphia, Pa.,v assignor to 'The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Application March .16, 1946; Serial No. 654,853

2 claims. 1

...This-:invention relates to a switch-and associ- ;z-ated lcircuit, having specialv applicability to power repress machines wherein the moving parts have f substantial-.mass and consequently considerable imomentum when vin use.

,.fOne of thegprimary objects of the invention is .'toiprovide a switch which is usable in connection 'withcheavy machinery to permit reversal without breakage of the associated gear or pulley :drive: in the mechanical power circuit.

f Another-object of the invention is to provide a l'zswitch by means `of which it is possible in conlnnectionwith circuits used in the operation of -cpowerfpresses `and .the like to slow down the movement of the mechanism in a'given direction -ffand reinstate the power for movement in the esame direction without interference with auto- .imaticcontrols of the reversing mechanism.

Still .another object is to provide a switch for l' power presses and the like which in a single unit 1 is :provided with contacts centrifugally controlled,

-insuringv practical stoppage of the machine be- 'fore powercan be applied in the reverse direci; tion.

An object also is to provide a circuit usable in,

Other objects ofthe invention relate to the @novel circuit larrangement by which the switch is madeLeffective, and features of the switch strucsature, such as will appear on consideration of the .following description rand the accompanying f. drawings:` in which:

,'.Figure 1 is a view of the switch structure in association with the wiring circuit;

Figure 2 is a detail taken along lines 2--2 of w Figure 1 showing the reverse position of the cen- ...trifugal element of the switch; and

Figure 3 is a detail showing the forward posi- :'tion of the centrifugal element.

Referring to Figure 1, I have indicated an elecftric': motor I provided with a power gear 2 with mechanical -connection to the press 3. The mo- Atoris supplied .from a power source 4 through a Umanual switch 5 and automatic switches Il'lb and 16.431); rvswitch Mb controlling the forward motor Idirection andlIBb the reverse motor direction.

fThe motor also has direct mechanical connecltion, to a shaft 9 of the centrifugal switch, genwerally indicated by the numeral I0. This switch aicomprises twoxmain sections, a centrifugal ele- Mment" II and acontact element sl2.y The centrif-.

ugal element is of a common form consisting,..of a collar I3 xed to the shaft 9 having supporting arms I4 and I5 on which are pivotally mounted the weights I6 and I'I. The power ends of these pivoted weights are pivotally connected to the shaft slide I8 through connecting bars I9 and 20 so that on rotation of the shaft the masses I6 and Il pass through a pivotal rotation, moving rthe slide I8 toward the collar support I3. This movement of the centrifugal masses and the slide I8 is against the spring action of the coil spring 2Ia inserted on the shaft 9 between the fixed collar I3 and the slide I8. The contact element I2 is formed of a drum 2l and a contact plate slidable movement relative to the shaft. A friction clutch or bearing secures a controlled rotational slip between the drum and the slide. Diametrically oppositely located rods 23 project rearwardly from the drum parallel to the shaft and contact plate 22 is mounted for sliding movement on these rods. Springs 2i normally urge this plate against the drum.

The plate 22 is of insulation material and is adapted to support metal contacts at, and extending through, either end thereof, there being one contact 25 at one end and another contact 26 at the other end of the bar. These contacts are electrically joined by conductor 26a, Coacting stationary contacts are positioned on either side of the bar contacts 25 and 26. Opposite the contact 25 is contact 2'I on the rear side and contact 2B on the fore side, the contact 28 having electrical connection to plate contact 25. Opposite contact 2B is contact 29 on the rear side and contacts 30 and SI on the front side. These latter two contacts 3c and 3I are electrically insulated and superimposed one above the other so that the movable contact 26 may engage them separately and alternatively dependent uponthe rotational position of the plate 22. To this end the contact 26 is limited in cross-section so that it will make engagement with only one of the contacts 30, 3! at a time.

The plate 22 is subject to a limited rotational movement with the friction drum 2| in accordance with thedirection of rotation of the shaft 9. This may be accomplished by utilizing the insulationbar ends as stops against a section. 32 of the supporting structure. At one limit of rotation, as in the forward direction indicated -by the arrow 33, the contact -26 will be in position to engage the contact 30, and in the reverse d1- rection, as indicated by the arrow 34, the contact 26 will be in position to engage the contact 3|. In both of these positions of the plate 22 contact at the other end of the plate connects with the contact 28. Also in both positions of the plate the contacts 25 and 26 are in engagement with the rear contacts 21 and 29 at zero rotation of the shaft 9.

The operation of the switch will now be apparent. Assuming a forward rotation as indicated by the arrow 33 of the shaft 9, the action of the drum 2| will be to shift the contact plate 22 to the forward position with the Contact 26 adapted to make engagement with the contact 30. As the speed increases the contacts 21 and 29 are broken and the plate moves forwardly until the contacts 25 and 26 are in electrical engagement with the contacts 28 and 39. This will be the normal forward position of the press operation and it will be maintained for the required operating time. On stoppage of the motor and press, rotation of shaft 9 drops to zero and the spring 2|a moves plate 22 back to the rear position.

the motor or the connecting gearing, the slip drum 2| will rotate to bring the contact 26 in position to engage the contact 3|, and on action of the centrifugal unit such engagement will be made, contacts 21 and 29 being simultaneously broken.

Having in mind the action of the switch as above described, the circuit arrangement will now be examined. A source of power 4i! is indicated applicable to the control circuit. From this source current leads through the conductor 4| to a manual stop switch 42, the reverse relay coil 43 and relay switch 43a controlled by relay 43, back to the source 40. From the circuit at point 45 between the stop switch 42 and relay 43 a conductor 46 leads through the forward relay coil 41 and the relay switch 41al operated thereby, back to the source 40, thus cornpleting a parallel circuit around the relay coil 43. At point 49 between the forward relay 41 and the relay switch 41a a conductor leads through the manual starting switch 50 to rear contact 21 at the switch and to the forward contact 3|). Also, from point 5| between the reverse relay 43 and the relay switch 43a connection is made to the reverse contact 3| and the rear contact 29 through the reversing manual switch 52.

When energized, relay coil 41 functions to close switch 41h and relay coil 43, when energized, functions to close switch 4317.

With the switch unit and circuit as above described and the switches 5 and 42 closed the operation in application to press machines, for example, is as follows: The operator to start the motor for operating the press 3 manually closes the starting switch 59 assuming that a forward direction of the press is desired. It will appear, therefore, that immediately on closure of the manual switch 5|) a circuit is established across the main terminals 4U of the power supply through switch contacts 28, 21, manual switch 5|) and relay coil 41. Energization of the coil 41 closes relay switch 41a which locks in the relay independently of the subsequent opening of the manual switch 5B. At the same time relay switch 41h in the motor circuit is closed thus energizing the motor for rotation in a forward direction and thereby causing forward movement of the press mechanism.

Should the direction of rotation of the shaft 9 be reversed due to a reversal of u During the movement of the press under the full forward speed, the centrifugal switch unit functions to retract the slide I8, permitting the springs 24 to open the switch contacts 25, 21 and 26, 29 respectively and close the connection vbetween forward contact 30 and contacts 26. Accordingly there is established at the manual switch 5U the voltage of the source, which may be made effective merely by the closure of switch 50. This is a conditioning operation which is useful in the situation which will now be described.

Should the operator desire after full forward speed of the press has been established to slow down the press action and then re-establish the same without reversal, this is accomplished by opening the stop switch 42 thereby de-energizing the relay coil 41 and thus opening the relay switches 41a and 41h. With the motor current cut off, the press speed decelerates to the desired point when the operator may again close switch 42 and the starting switch 5U, and since the voltage of the source is across the terminals of switch 50 by virtue of the centrifugally operated movement of the Contact plate 22, relay 41 is re-energized through conductor 46, relay switches 41a and 41o are closed, and the motor is again energized to pick up the full speed forward.

Should the operator desire to reverse the direction of the press, this is accomplished from the condition of full forward speed by opening the stop switch 42. This opens the motor relay switch 41b and brings about a gradual slowing down of the press and motor until the centrifugal action of the switch I0 brings about a disconnection of the forward contacts 30 and 28 Iwith the switch plate 22 and a re-establishment of the plate with the contacts 21 and 29. If the operator should attempt to reverse the mechanism prior to the closure of switch contacts 21 and 29, there will be no result on closure of reverse switch 52 since contact 26 is out of engagement with all stationary contacts. The reverse position of this plate cannot be accomplished until there is an actual change in the rotation of the shaft 9, in other words, until there is an actual reversal of the press mechanism. This reversal is accomplished by the operator closing switches 42 and 52 after the closure of the rear contacts 21 and 2S by the plate 22. Such action energizes relay coil 43 which is locked in by switch 43a thereby closing the reverse relay switch 43b to bring about reverse rotation of the motor I and a reversal of the press mechanism. As soon as this has been accomplished the contact plate 22 of the switch assumes the reverse position, and as the speed increases the plate moves axially to bring about engagement with the contact 26 on the plate and the reverse forward contact 3|, thus conditioning the switch 52 for re-energization of the motor in the reverse direction after opening of the stop switch 42 for an intermittent period.

It thus appears from the description of the circuit and switches as made hereinabove that in either the forward or reverse direction of movement of the press the operator may interrupt the movement temporarily and re-establish it. It also is evident that if a reversal is intended, this is accomplished only after the press mechanism and motor with the interconnecting gearing is slowed down to approximate Zero rotation, that is, to the point where the contact plate 22 makes engagement with the rear contacts 21 and 29. Accordingly, it is impossible for the operator to destroy the gearing or belt connections between the motor and the press by bringing about a reversal of the mechanism before the momentum of mass movement has arrived at approximately zero.

It is pointed out that the purpose of the slidc connection between contact plate 22 and drum 2i is to insure firm engagement of the electrical contacts when in the fore position. This develops from the fact that the drum rods 23 are longer than the distance between fore and rear contacts, so that when the centrifugal weights operate, the fore contacts close before the drum has moved to the fore limit of the slide movement. Consequently pressure is exerted by the rod springs 24 against the plate to insure a firm and effective electrical contact between the plate contacts 25 and 26 and the corresponding fore contacts 28 and 3l) or 3|.

It is apparent that the details of the switch unit as well as of the circuit are exemplary and susceptible to such modification as may come within the scope of the claims hereto appended.

What is claimed is:

l, in a control circuit for intermittently operated and reversible mechanism, an electric motor, driving connections between the motor and mechanism, a supply circuit for said motor, forward and reverse relay switches for said circuit, forward and reverse relay coils for said switches, a shaft operably connected with said motor, a friction drum mounted on said shaft for limited rotational and slidable movement, a contact plate secured to said drum, stationary forward and reverse contacts positioned adjacent the plate and engageable at one extreme of slidable movement and either extreme of rotational movement of said drum, said forward and reverse contacts having electrical connections respectively to the forward and reverse relays, centrifugal means for sliding the switch plate intocontact engagement, manual means for initially energizing said coils, said forward and reverse contacts being made alternately in accordance with the direction of the shaft rotation, and other stationary contacts at the other extreme position of slidable movement of said drum which engage the contacts on said drum in either rotated position thereof.

2. In a control circuit for intermittently operated and reversible mechanism, in combination, an electric motor, driving connections between said motor and said mechanism, a supply circuit for said motor, forward and reverse switch means in said circuit for said motor, a speed-responsive control device operated by said motor, a contact plate mounted and connected to be moved axially by said speed-responsive device, axially spaced sets of xed contacts adapted to be engaged by contacts on said contact plate, one set of contacts also being spaced circumferentially and said plate and its contacts having limited circumferential movement caused by rotation of said speed-responsive device in forward or reverse direction to engage different circumferentially spaced contacts, the second fixed set of contacts being located for engagement in either rotated position of said contact plate and said plate contacts engaging the other fixed set when the motor and speed-responsive device have stopped rotation, circuit means including selective forward and reverse manual start switch means connected with said second xed set of contacts which are effective when the contact plate is in the stopped position where it engages the second stop plate for starting the motor in either forward or reverse direction selectively, and circuit means associated with the first xed set of contacts and the contact plate and the manual start switch means for restarting the motor only in the direction in which it was last started whereby the motor may be started in either direction from a stopped position and may be restarted but not reversed when having any substantial rotational speed in either direction.

PAUL WITTE.

REFERENCES CITED UNITED STATES PATENTS Name Date Rasmussen Oct. 15, 1940 Number

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