US1820808A

US1820808A - Time switch

Info

Publication number: US1820808A
Application number: US463207A
Authority: US
Inventors: William K Kearsley
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1930-06-23
Filing date: 1930-06-23
Publication date: 1931-08-25
Anticipated expiration: 1948-08-25
Also published as: GB357439A

Description

A 931. w. K. KEARSLEY 1,820,808

. TIME SWITCH 1 Filed June 25, 1930 (a lllllllbllll l llIII IHHIIIHHIHlllllllllllllllllllllllllllllllll O.

Inventor-z William K- Keafsle His Attorney.

Patented Aug. 25, 1931 UNITED STATES PATENT OFFICE 'WILLILH K. KELBSLEY, OI SGKENEGTADY, NEW YORK, ASSIGNOR '1'0 GENERAL ELEG- TBIC COMPANY. A C RPORATION OF NEW YORK TIME SWITCH Application fled June 28, 1930. Serial No. 488,207.

My invention relates to time switches and is particularly adapted for timing the period of energization of X-ray apparatus where it is essential that the time of exposures be accurately determined in order that the patient shall not be overexposed and to prevent underexposures. The time switch of my 1nvention enables a circuit to be controlled very accurately as to duration of closure and such periods may be varied by half cycle steps of an alternating current circuit from one-half cycle upward and when used with alternating current this device is preferably arranged to make and break the circuit at the zero portion of current wave.

The features of my invention which are believed to be novel and patentable will be ointed out in the claims appended hereto. l or a better understanding of my invention, reference is made in the following description to the accompanying drawings in which Fig. 1 represents a perspective View of the time switch mechanism as a whole. Fig.

2 is a sectional view taken through the sli ing contact carriage and its support. Fig. 4 is a detail view of a portion of the rotary switch drum showing the notches in the conducting ortion thereof arranged to break the circuit at the zero point of an alternating current wave. Fig. 3 is a %i cture representing the notched surface of i 4 as 'laid out fiat. Fig. 5 is a detail view 0 an adjustable coupling employed for adjusting the phase relation at which t heswitchingoperation will take place; and Fi 6 shows-a portion of a timing scale emp oyed for adjusting the duration of switch closure.

Referring first to Fig. 1, 10 is an alternating current synchronous motor supplied from the alternating currentsource 10' which I will assume for thepurpose of description as being a 60 cycle circuit. The motor 10 is assumed to,be a 4-pole motor and therefore will drive the shaft 11 at 1800 R. P. M. if

15 and a central conducting part 16. Also mounted on shaft 12 is a screw thread 17. In

directly connected thereto. Shaft 11 is con-' the apparatus which I have built I have employed 4 threads per inch in the screw 17.

The shafts 11 and 12 are supported in suitable bearings and shaft 11 may be connected to the motor 10 either directly or through speed changing gears contained in a casin 18 by means of a lever 19 arranged so as to s ift the gears and change the speed relation between the synchronous motor 10 and shaft 11. As represented, three such speeds are provided for and an indicator 20 attached to the lever 19 indicates the speed setting of this portion of the mechanism.

Parallel with shafts 11 and 12 is a shaft 21 which is arranged to berotated through a '05 small angle by an electromagnet the coil of. which is shown at 22 and the armature of which is shown at 23. The armature 23 issecured to an arm 24 fastened to shaft 21 in such a manner that, when the electromagnet is energized the shaft 21 rotates through a small angle in a counter-clockwise direction as viewed from the left-hand end of the shaft. Compression spring 25 serves to turn shaft 21 in the opposite direction when the electromagnet is. deenergized. The circuit of the electromagnet may be controlled by a push button 26 or any other remote circuit control device, either manually or automatically.

Slidably mounted on shaft 21 is a supporting tube or carriage 27 which carries at one end an arm 28 overhanging the screw thread 17 and the outer end of which is adapted to engage between the threads when the electromagnet 22 is energized. The tube 27 is preventedfrom turning on shaft 21 by means of a slot 29 in which rides a pin 30 secured in shaft 21. The slot 29 in the tubular part 27 extends lengthwise of the tube a suflicient distance to allow tube 27 and the parts carried thereby to be moved back and forth along shaft 21 a distance corresponding to the length of the screw thread 17. Secured to the central portion of the tube 27 is a 8 contact arm 31 and adjustably mounted along 05 the tube 27 is a second contact arm 32. These contact arms overhang the contact cylinder and are adapted to engage therewith when the electromagnet 22 is energized. It will thus be apparent that when the electromagnet 1 screw thread 17. An arm 33 extends from the tube 27 and between the stationary posts 34 andthe endof this arm 33 is a sprin 35 the purpose of which is to returnv the tube 27 to the left when the electromagnet is deenergized.

It will be noted that the contact fingers 31 and 32 are'connected in series relation with an electric circuit suitably arranged to control the energization of apparatus indicated at 36. This apparatus may be an X-ray tube as indicated and hook-ups other than the one represented may be employed. It will thus be seen that when the contacts 31 and 32 are on the conducting portion 16 of the contact drum the X-ray apparatus will be energized. When the tube 27 is in its left-hand position the contact finger 31 is over the non-conducting portion 14 of the contact drum so that when the electromagnet 22 is first energized and the carriage rendered active, the circuit controlled by the device is not closed until the worm 17 has carried the tube 27 a short distance to the right where the contact finger 31 moves on to the conducting portion 16 on the contact cylinder. The line of junction between the adjoining conducting and nonconducting surfaces 1416 forms a spiral about the drum having the same pitch as the screw thread and there is preferably provided a step or notch 37 in the spiral, which step isparallel with the axis of rotation and this stepped part may be rotatably adjusted by means of the coupling 13 so that contact finger ,31 moves onto conducting portion 16 at some predetermined selected portion of an alternating current wave as for instance that portion of the alternating current wave when the current is passed through zero. Thus the coupling is provided to properly adjust the phase relation between the synchronous motor and the contact drum.

' As mentioned previously the contact ,fin%ar 32 is adjustable along the sleeve 27 y means of a suitable latch 38 cooperating with a toothed rack 39 the exact position of the contact finger 32 along sleeve 27 ma be determined. I prefer to provide this ad usting device with a sufficient number of adjustable positions so that the distance between each such position is one-quarter the distance the arm would move for one complete rotation of the screw 17.

The right hand end of the conducting portion 16 is provided with four steps connected by spiral lines between. its end and the insulating portion 15, one'of such steps being in alinement with the step 37 and the remaining three steps bein equally spaced around the periphery as in icated in Figs. 3 and 4. The Y purpose of this arrangement is to permit the contact finger 32 to move off of the conducting portion onto the insulating portion of the contact cylinder at any half cycle of the alternating' current wave when the current is passed through zero. It is seen that the motor 10 and the circuit supplying the alp-v from the relation that when the drum is rotating at 1800 R. P. M. and the frequency of the source is 60 cycles the alternating current wave will pass through zero four times per drum revolution. Thus the circuit controlling the X-ray or other apparatus is made and broken when the current in such circuit is a minimum and by such an arrangement the switch mechanism can be employed to handle alternating current of very large amperes without danger of burning the contacts by arcing. However, aside from this advantage these features are desirable in the operation of X-ray and similar apparatus from the standpoint of accurate energy control. prevention of surges, etc., particularly when the period of energization is very short.

If the contact fingers 31 and 32 are spaced apart the distance of the length of the conducting portion 16 opposite point 37 and the synchronous motor 10 is set into operation and the control switch 26 closed, the circuit through contact finger 31 will be made at the same instant that the contact finger 32 moves onto the insulating portion 15 as these contact fingers move to the right and this represents a zero time setting of the switch mechanism. If the contact finger 32 is now moved one notch to the left and the operation repeated the contact finger 31 will ride onto the conducting portion 16 one-half of a cycle before the contact finger 32 passes onto the insulating portion 15. Under these conditions the time setting of the switch is one-half of a cycle assuming the shaft 12 to be rotating notches from the zero time point the apparatus'will be adjusted to energize the apparatus 36 for '0.1 second.

A suitable scale plate 40 is provided on the tubular carria e 27 to facilitate such adj ustment and since have indicated three different speed adjustments of the contact cylinder by means of the gear changlng devlce 18the scale plate is provided with three

scales

41, 42 and 43, corresponding to the three speeds of the contact cylinder. Scale 41 is used when the contact drum is driven at the same speed as the motor, or 1800 R. P. M., and this scale is marked '1/120S, indicatmg the time value in seconds of each graduation thereon. The graduations on

scales

42 and 43 are for contact drum speeds of 150 and 30 R. P. M. respectively and the time value for each graduation of such scales are there fore 1/10 and 1/2 seconds respectively. This relation between the scales works out advantageously since the same notches on the rack 39 are used for all scales and the relation gives a wide range of accurate time adjustment of the switch setting in appropriate steps. The speed ratios obtainable by means of the speed change mechanism 18 should therefore be 1 to 1, 1 to 12, and 1 to 60 with this arrangement.

I have provided a catch 44 which is adapted to engage with arm 33 when the latter is moved to the extreme right with the electromagnet 22 energized. The purpose of this catch is to prevent chattering of the finger 28 on the right hand end of the screw thread 17 should the electromagnet 22 remain energized after the switch mechanism has reached the end of its travel. Arm 33 is released from the catch when the electromagnet 22 is deenergized by reason of the fact that arm 33 49 then moves away from the catch with the rotational movement of the shaft 21 and the tubular switch carriage 27.

I do not wish to limit my invention to the exact details of construction shown and described but seek to cover in the appended claims such other modifications as fall fairly within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

. 1. A time switch comprising an electric motor, a drum rotated by said motor, said drum being provided with a cylindrical conducting surface between its ends, contacts spaced apart lengthwise of and adjacent to said drum, the spacing of said contacts belng less than the length of the conducting sur' face of said drum, means driven bv said motor for moving said contacts lengthwise of said drum, and means for rendering the last means active and moving said contacts onto the surface of said drum, whereby a-circuit is momentarily completed through said contacts and conducting surface, said circuit being completed at one contact at one end of drum, an

the conducting surface and broken at the cfither contact at the other end of said sur-.

ace.

2. A time switch comprising an electric motor, a shaft driven thereby, a contact 7 drum and screw thread on different portions of said shaft and rotated thereby, a contact carriage movable parallel 'with said drum, spaced contacts on said carriage extending towards said drum, an arm on said carriage 7 extending toward said screw thread, means for causin the spaced contacts to engage the said arm toengage the screw thread whereby the contacts are moved lengthwise along said drum in contact thereso with at a'rate proportional to the speed of rotation of said drum.

3. A time switch comprising a synchronous electric motor, an alternating current supply therefor, a contact drum rotated by said 5 motor, said drum having conducting and non conducting adjoining surfaces, the line of junction between said surfaces forming a stepped spiral about said drum, a contact adapted to engage the surface of said drum, means for moving said contact parallel to the axis of rotation of the drum as the drum is rotated so that the contact will trace a spiral path on the drum surface parallel to the spiral line of junction and cross a step therein from one of said surfaces to the other, and means for adjusting the rotative position of said drum with respect to the synchronous motor so that said contact will pass from one surface to the other at a predetermined point in the wave of the alternating current supplied to said motor.

4. A time switch, a synchronous electric motor, a shaft driven synchronously with said motor, a contact drum and a spiral thread on different portions of said shaft, said contact drum having conducting and nonconducting adjoining surfaces, the line of junction between said surfaces forming a stepped spiral about said drum of the same pitch as said screw thread, a contact carriage having a finger adapted to engage the spiral thread and to be moved thereby parallel to said contact drum when the shaft is rotated, a contact on said carriage engaging with said drum so as to trace a spiral path on said drum when the latter is rotated, said path being parallel with the spiral line of junction between said surfaces and crossing from one to the other at the step therein, and means for adjusting the rotative position of said drum with respect to the synchronous motor.

5. A time switch comprising a contact drum having a central conducting portion and two non-conducting end portions, a pair of contacts spaced along said drum, a synchronous motor for rotating said drum and moving said contacts lengthwise on the surface of said drum to consecutively move one contact from one non-conducting portion to the conducting portion while the other contact is on the conductin portion and thereafter moving the said ot er contact onto the other non-conducting portion while the first mentioned contact is on the conducting'portion, means for adjusting the spacing between said contacts, and means for determining the rotative positions of said drum at which said contacts will move onto and off the conducting portion thereof.

6. A time switch comprising a contact drum having a central conducting surface portion and two end non-conducting surface portions, a pair of contacts spaced along said drum, a circuit adapted to be closed through said contacts when bothare on the conducting portion, a synchronous motor for rotating sa1d drum and moving said contacts lengthwise therein from an initial position to close the circuit when one contact is moved from a non-conducting to the conducting portion at one end of the drum and thereafter to open the circuit when the other contact is moved from the conducting to the non-conducting portion at the other end of said drum, means for adjusting the spacing between said contacts to determine the duration of closure of the circuit, means for causing the circuit to be'closed and opened at predetermined rotative positions of said drum, and means for automatically removing said contacts from said drum and returning them to said initial position.

7. A time switch comprising a switch mech anism having relatively movable contacts for openin and closing a circuit, a synchronous motor for operating said switch mechanism, a speed changing device between said switch mechanism and motor, common means for adjusting the contact mechanism for different circuit closure periods for all speeds of 'said mechanism, and a scale plate relative to which said adjusting means is moved having a scale for each speed adjustment of said mechanism to indicate the circuit closure period for which said mechanism'is set.

8. A time switch comprising a four-pole synchronous motor, a contact drum having a central conducting portion and non-conducting end portions driven at the same speedas the motor, contacts spaced apart along said drum adapted when engaged with the conducting portion thereof to close a circuit therethrough, means for moving saidcontacts parallel to the axis of rotation of said drum at a rate proportional to the speed of the motor to close and open said circuit, and means for adjusting the spacing between said contacts so as to obtain circuit closure periods varying in steps corresponding to 1/4 revolution of said drum.

In witness whereof, I have hereunto set my hand this 20th day of June, 1930.

WILLIAM K. KEARSLEY.