US2053143A

US2053143A - Timing apparatus

Info

Publication number: US2053143A
Application number: US681700A
Authority: US
Inventors: Oscar C Frederick
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1933-07-22
Filing date: 1933-07-22
Publication date: 1936-09-01
Anticipated expiration: 1953-09-01

Description

Sept. 1, 1936. o. c. FREDERICK TIMING APPARATUS Filed July 22, 1933 Invefitor: Oscar C. Frederick,

[*atented Sept. 1, 1936 UNITED STATES PATENT OFFICE 2,053,143 TIMING APPARATUS v New York Application July 22, 1933, Serial No. 681,700

6 Claims.

My invention relates to apparatus for timing industrial operations which must be repeatedly performed in a predetermined interval of time.

My invention is particularly suited for timing resistance welding operations such as are encountered in spot welding or flash weldin Ac curate time control of the welding current, particularly for such metals as stainless steel, aluminum and the like, is highly important. It be- 10 comes more essential with these metals than ordinary steels. It has been found that it is necessary to have the time extremely short and the current values relatively high. This is especially necessary in the welding of stainless steel, as it 315 prevents the combination of carbon and chromium which destroys the stainless qualities of the steel and permits corrosion.

It is an object of my invention to provide an im proved apparatus for accurately timing a welding operation independently of the operator who is free to initiate the operation but cannot thereafter interrupt it until a predetermined welding time has elapsed.

it is a further object of my invention to provide apparatus of the character described which will be small in size and cheap enough to warrant its use with small sized equipments such as are used for performing certain spot welding or stud welding operations. 7

Further objects of my invention will become apparent from a consideration of the following description of one embodiment thereof which has been diagrammatically illustrated in Fig. l of i the accompanying drawing and a modification as thereof shown in Fig. 2 of this drawing,

in this drawing the circuit to be controlled i, extends from a source alternating current surply 3, i to the primary of a welding transformer t. This circuit is completed by an electromagnetlc switch l whose operating coil 2 is connected to the source or" supply l through the following circuit: From supply conductor through con ductor 9, control switch it, which is normally biased to an open position, conductor ll, con= l5 ductor l2, switch iii of a timing relay i conductor 35, safety switch l8, and a conductor ii to supply conductor l. When the electromagnetic switch closes, an auxiliary switch in shunt to the control switch ill is also closed completing a holding iii? circuit for the electromagnetic switch through the following circuit: From supply conductor through conductor is, auxiliary switch it, conductor l2, switch ill of timing relay it, conductor l5, safety switch It and conductor ill to supply conductor 4. The safety switch it may be a hand-operated switch which is latched in the closed position until opened. upon an overload through the agency of its tripping coil 20. This switch is provided to protect the control circuits which may be damaged by the flow of abnormal 5 currents therein such as might occur upon the short circuiting of exposed conductors by a careless operator while adjusting the timing relay.

The movable contact of switch 13 is normally biased into engagement with the fixed contact of 10 the switch by means of an operating member 2|. The end of this operating member extends between and in the path of movement of arms 22 and 253 of the timing relay M. The arm 22 is permanently fixed to the shaft 2d of the relay and the arm 23 is adjustahly supported thereon and held in adjusted position relative to the arm 22 by means 0; a clamping nut 25. Arm 22 is pro vided with a dial plate upon the surface of which there are graduations by means of which 20 the adjustment of the

arms

22 and 23 may be facilitated. The movement of the operating member 25 is limited by adjusting screws 2i and 22 which through the agency oi the operating member 2t constitute stops for the arms 22 and The ad 25 justing screw 22 also supports the fixed contact of the switch l3.

Forward and reverse rotation is imparted to the

arms

22 and 23 of relay i by means of self-start ing synchronous motors 29 and forming U or" the relay. Ihese motors maybe oi"; the con struction more fully illustrated and desricecl in United States Letters Patent No. 5 Warren, July 14, 1925. They are pole faces of motor 29 are counterclockwise or forward rotation 22 and whereas the shading coils pole faces of the motor are arranged t a clockwise or backward rotation of hes means of which th common to the shaft upon which the a are supported. It is to he noted that the rotors of these motors are permanently connected arm 22. The arrangement of rotating on closed within the casing and lid he such as illustrated in United States Le ters No. 1,459,936, H. E. Warren, granted May 27, 192 5. For timing operations of short duration the gearing is suitable to impart a complete rotation to

arms

22 and 23 in. one second of time. a

- plate 26 of arm 22 may then be marked to indicate timing periods in cycles.

Motor 29 being a synchronous motor inherently operates in step with the frequency of the source of

supply

3, 4 and the arm 22 is preferably fixed on the shaft 24 so as to break the operating circuit of the electromagnet switch 'I at switch i3 at the proper time to cause the electromagnetic switch I to open at the zero or on the declining part of the voltage wave of the source of supply. This greatly relieves the duty on the contacts of the electromagnetic switch and facilitatesthe operation of the control apparatus. This adjustment will, of course, depend on the characteristics of the switch used in the control circuit. I have successfully employed an electromagnetic switch having the construction disclosed and claimed in the application of Ludwig S. Walle, Serial No. 667,856, filed April 25, 1933, and assigned to the same assignee as the present application. In such a switch the contacts are sealed within a closed chamber and the arc drawn-between the separating contacts generates a gas pressure within the chamber which rapidly increases and quickly extinguishes the arc. When using a switch of this description to interrupt the circuit of 10 and 25 Kva. transformers, I have found that it is necessary to open the circuit through switch I3 at approximately the peak of the voltage wave for oscillographs indicate that the operation of the pressure switch lags the operation of switch i3 by approximately a quarter of a cycle. With this adjustment the pressure switch opens the welding circuit on the declining part of the voltage wave.

The field coil 35 of motor 29 is initially connected to the source of

supply

3, 4 through the following circuit: From supply conductor 3, conductor 9, control switch It,

conductors

31, 38, 39,,

tor l9, auxiliary switch l8 of electromagnetic switch I, conductors ll, 31, 38, 39 and i5, safety switch It and conductor H to the source of supply 4. It is to be noted that motor 30 is normally energized and is only deenergized during the operation of timing motor 29.

The field coil 36 of motor 30 is connected to the source of

supply

3, 4 through the following circuit: From supplyconductor 3 through conductors 9 and 40, contacts 4| of relay 42,

conductors

43, 44, 39 and I5, safety switch It and conductor I! to supply conductor 4. When relay 42 is energized this circuit is interrupted at contacts 4|. The operating coil 45 of relay 42 isinitially connected to the source of

supply

3, 4 through the following circuit: From supply conductor 3 through conductor 9, control switch It],

conductors

31 and 46, safety switch l6 and conductor I! to the .to the source of

supply

3, 4 through the following circuit: From supply conductor 3 through con- 'ductor l9, auxiliary switch I8 of the electromagelectromagnetic switch 1 and energizes the selfstarting synchronous motor 29 and simultaneously deenergizes the self-starting synchronous motor 30 through the agency of relay 42. As soon as the electromagnetic switch closes the auxiliary switch |8 associated therewith is also closed.

This switch is connected in shunt to the control.

switch i6 which is normally biased to an open position and opens as soon as the operator releases it. Once started the welding operation will continue until the arm 22 of the timing relay i 4 engages the switch operating member 2| and opens switch IS in the operating circuit of the electromagnetic switch I. The opening of switch l3 deenergizes the electromagnet 8 of this switch as well as motor 29 and relay 42. The deenergization of relay 42 connects the motor 30 to the source of

supply

3, 4 as pointed out above and this motor will then return the parts to their initial positions illustrated in the drawing. These positions will be determined by the adjustment of set screw 28 which in conjunction with the switch operating member 2| constitutes a stop for the backward movement of arm 23 which on stopping stalls the normally energized motor 30. The set screw 21 in conjunction with the operating member 2| of the switch |3 constitutes a stop for the forward movement of arm 22. The provision of such a stop'is not necessary but is effective in preventing forward travel of the arms 22 after the motor 29 has been deenergized. This shortens the time required by motor 30 to reset the timing relay. Set screw 21 may in some applications of my timing relay support a fixed contact which is suitably connected in the control circuit.

It will be noted that once the welding operation has been initiated by the operator closing the control switch ill, the duration of the welding operation is no longer under his control, but is determined by the operation of the timing relay I4. However, unless the operator releases the switch I!) so that it may be returned to its normal open position, the timing relay M will not reset itself due to the disconnection of motor 30 from the source of

supply

3, 4 at contacts 4| of relay 42 which is maintained energized so long as control switch Ill is held in its closed position.

With a timing relay of the construction illustrated in Fig. 1, it is possible for the operator toobtain a faulty timing operation if the control button Ill is closed before the resetting motor 30 has had an opportunity to fully reset the relay. This result will follow by reason of the fact that if the control button is depressed the system will be set into operation soon as the contacts of the timing relay are closed, and these contacts will be closed as soon as the arm 22 of the relay which has openedthem has been moved in a resetting direction a very short distance. By modifying the construction of the relay M as illustrated, in Fig. 2 of the drawing, this possibility of faulty operation of the system may be completely avoided. By referring to this figure it will be noted that the operating member 2| of the switch I3 is pivotally supported at "and provided with a toggle 48 by means of which it is held in engagement with the set screw 26 until arm 22 forcefully moves it therefrom and in engagement with set screw 21 until arm 23 forcefully moves it from engagement therewith. This toggle comprises a notched plunger 49 inserted in a support 56 and provided with a spring 5| inserted between the head of the plunger and the support 50. The notch in the plunger furnishes a bearing for in ele the pointed end 52 of the operating member 2|. With a construction such as illustrated in Fig. 2 it will be noted that the operating circuit through switch ill will not be completed until the operating member 2| for the switch has been moved to the position illustrated by a backward movement of the arm 23. It will thus not be possible for the operator to initiate an operation until the timing relay has been fully reset and, consequently, the timing operation will be of a predetermined duration irrespective of the activity of the operator.

The welding time is determined by the relative adjustment of the

arms

22 and 23. Depending upon the gear reduction employed in the trans-. mission between'the

arms

22 and 23 and the

motors

29 and 30 the duration of the weldingperiod may be greatly varied. In one embodiment of my invention in which the

arms

22 and 23 are given one complete revolution in one second, timing operations from 2 to cycles have been obtained with a cycle source of supply by suitably adjusting the

arms

22 and 23 relatively to one another. Oscillographic records have proved that the timing period once established may be repeated with very little error. The contacts of the switch l3 should be made of some wear-resisting material so that repeated opera tion of the switch i3 will not change the duration of the timing period once the apparatus has been set.

7 It is apparent that the switch operating mem her 2! may be the control element of any device which it is desired to operate after the lapse of a predetermined period of time. It is also apparent that other means than the arm 23 in conjunction with the switch operating member it may be used for limiting the resetting movement of arm 22. Thus, while I have described but one embodiment of my invention, it is to be understood that other embodiments thereof rnay be made without departing from my invention.

What 1 claim as new and'desire to secu-e by Letters Patent of the United States is:

l. Apparatus comprising a movable arm, a control element located in the path of movement of said arm, a self-starting synchronous motor connectedto move said arn'i into engagement with said control element, a second normally energized motor connected to move said arin away from said control element, means for stalling said sec-- ond normally energized motor after a predetermined separation of said arm from said control element, source oi alternating current, and means tor deenergizing said second motor and for connecting said first-mentioned motor to said source alternating current until arm open ates said control element.

2. Apparatus comprising a plurality oi arms, a on which said arms are supported, means or adjusting the separation of said arms, timing p cans for rotating said sha t in one direction at 3 will! a re eterznined speed, reset g means operative said timing means is inoperative for rotatg said the reverse direction, a control ment located between and in the path of mo /e rnent of said arms, stops on each side said control element which limit the movement therewhen actuated by said arms, means for initiating the operation of said timing means, and means operated by movement of said control element for interrupting the operation of said timing means.

3. Apparatus comprising a plurality oi arms, a shaft on which said arms are supported, means for adjusting the separation of said arms, timing means for rotating said shaft in one direction at a predetermined speed, resetting means operative when said timing means is inoperative for rotating said shaft in a reverse direction, a switch 5 biased to either one of two positions and having an operating member located between and in the path of movement of said arms, means including said switch for initiating the operation of said timing means after said switch has been moved to one of said positions by said resetting means, and means including said switch for interrupting the operation of said timing means when said switch is moved from said one position to said other position.

4. Apparatus comprising a plurality of arms, a control element located between and in the path of movement of said arms, means for adjusting the separation of said arms, timing means for imparting a forward movement to said arms, resetting means operative when said timing means is inoperative for imparting a backward movement to said arms, means for stalling said resetting means and limiting the backward movement of said control element and said arms, means for simultaneously rendering said timing means operative and said resetting means inoperative, and means responsive to the forward movement of said control element for rendering said timing means inoperative and said resetting means operative.

5. Apparatus comprising a plurality of arms, a switch having an operating member located between and in the path or" movement of said arms, the backward movement of said member being limited by said switch in its closed position, means for adjusting the separation of said arms, a self-starting synchronous motor connected to impart a forward movement to said arms, a second normally energized self-starting synchronous rnotor connected to impart a backward movement to said arms until one of said arms engages and is brought to rest by said operating member of said switch, a source of alternating current supply, and means including said switch in its closed position for connecting said first-=mentioned motor to and for discon-= nesting said second motor from said source of supply until the other of said arms on its forwa d movement opens said switch by engaging its saio. operating member.

Appar oompris'ng a plurality of arms, a 5i Itch having an operatmg member located be" ven in the path of movement of said arms, th ward inovern said member being ts ts closed position, means r supported, self-start to rotate said '1 lard direction, a sec normally energized self-starting synchrono arms engages operating m alternating cu trolled, means switcli for co hiding electromagnetic lg said circuit to and for dis rcuit from said source of supply,

a starting swit ing post ,on, an auxiliary switch connected in shunt to said starting switch and closed and opened by the olosing'and opening of said electromagnetic switch, means including said starting member and deenergizes and opens said electromagnetic switch, and means including said starting switch and said auxiliary switch for connect in: said first-mentioned motor to and for dis- 1 connecting said second-mentioned motor from said source of supply.

OSCAR C. FREDERICK.