US1902508A

US1902508A - Time switch

Info

Publication number: US1902508A
Application number: US495193A
Authority: US
Inventors: William K Kearsley
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1930-11-12
Filing date: 1930-11-12
Publication date: 1933-03-21
Anticipated expiration: 1950-03-21

Description

' March 21, 1933. w. KEARSLEY TIME SWITCH Filed Nov. 12, 1930 2 Sheets-Sheet l Inventor.

March 21, 1933.

W. K. KEARSLEY TIME SWITCH Filed Nov. 12, 193.0 2 Sheets-Sheet 2 Patented Mar. 21, 1933 UNITED STATES PATENT OFFICE WILLIAI K. OF SGHENECTLDY, NEW YORK, ASSIGNOB '10 G ELECTRIC CODA, A CORPORATION 01 NEW YORK rnmswmcn Application fled November 1a, 1000. Serial Io. 495,193.

of, my invention is to provide a time switch of small physical-proportions having a reasonably large timing range with a very hi h degree of accuracy in the setting of t e time switch during a predetermined portion of the timing range and a moderate degree of accuracy in the setting 16 of the time switch during the remainder of the timin range. A further object of my invention is to provide a time switch that may be operated for a time interval that is only slightly longer than that required by the 20 timing function of the switch without interfering with the accuracy of the timing function. Additional objects of my invention will be mentioned during the progress of this specification.

B5 The usualform of time switch has its contacts operated by a mechanism which moves at a substantially constant velocity. The switch is usually provided with an arm for varying the time interval involved in the timing function of the switch and is also provided with a scale cooperating with the arm to indicate the time interval, the scale having uniformly spaced markings because the contacts are operated by a mechanism having a substantially constant velocity. It

is obvious that the greater the separation between the markings the more accurately can the adjustable arm be set to obtain a predetermined time interval for the timing func- 10 tion of the switch and the accuracy of the setting is substantially the same during the entire timing range because of the uniformly spaced markings on the scale.

It is frequently desirable to have a time switch of small proportions having a reasonably large timing range with a very high degree of accuracy in the setting of the switch during a predetermined portion of the timing range and a moderate degree of accuracy in the setting of the switch for the remainder of the timing range. One example where such a time switch is particularly desirable, which example I prefer to subsequently utilize in describing the operation of my invention, consists of the timing of the period 5 of energization of X-ray photo aph apparatus. Modern X-ray practice emands hi h speed in the taking of X-ray photograp s of many parts of the human body having natural movement of organs, and to obtain photographs susceptibleof correct diagnosis it is desirable to combine the high speed with a very high degree of accuracy in the setting of the switch to give a predetermined time of exposure even if such exposure is to last a very small fraction of a second. The takmg of X-ray (photographs of other parts of the human bo y may, however, require comparatively long exposures, for example 25 seconds, these exposures usually requiring 7 only a moderate degree of accuracy; If the usual form of time switch is employed with its scale markings spaced sufiiciently far apart to give a very high degree of accuracy for the .very short exposures, it results in a very small timing range for a given size of switch, whereas if the markings are sufliciently close to give a reasonably large timing range it results in a correspon-di decrease of accuracy in the setting the switch. In the usual form of time switch a reasonably'large timing ran and a very high degree of accuracy may obtained by making the switch of very large proportions for its timing range or by providing a speed changing device between the time switch motor and the mechanism operating the contacts for driving the mechanism at different speeds. An example of the latter type of switch is described in United States Patent 90 No. 1,820,808, issued to me on August 25,

1931, and assigned to the same assignees as I the present invention.

It is desirable, however, to provide a time switch of small proportions for areasonably large timing range with a very high degree of accuracy in setting during a predetermined portion of the timing range without resorting to speed changing devices or other mechanical complications; My invention 0 considered in connection with the accom-- panying drawings while those features of my invention which are believed to be novel and patentable are pointed out in the appended claims.

In my copending application Serial No. 426,427, filed February 6, 1930, assigned to the assignees of the present invention, I have described the advantages of having a rectifying device control the operation of X-ray apparatus. In my patent referred to above,

I have described a time switch for controlling the above rectifying device to thereby control the operation of X-ray apparatus and in my present invention I prefer to describe the operation of my time switch for a similar purpose. 7

Fig. 1 represents a perspective view of the time switch and a known form of X-ray apparatus whose period of energization is controlled by the time switch; Fig. 2 represents a plan view taken on line 2-2 of Fig. 1 and shows the means employed for permitting the driving motor of the switch to start movement of the switch only at a predetermined point in the wave of the alternating current source operating the X-ray apparatus; Fig. 3 represents a perspective view of the parts shown in Fig. 2; and Fig. 4 represents a plan view of the time switch.

A brief description of the X-ray apparatus follows. In

Fi

1, 10 represents a well known form of -ray tube which comprises a highly evacuated bulb 11' in which are sealed a cathode filament 12 and an anode target 13. A transformer 14 has its secondary 15 connected to the filament 12 and its primary 16 connected to an alternating

current source

17 and 18 in series with an adjustable resistance 19. The source'17 and 18 has an assumed frequency of 60 cycles. A three-element thermionic valve 20 comprises a cathode filament 21, an anode plate 22 and a grid 23, all sealed in a highly evacuated bulb 24. A transformer 25 supplies current to the filament 21. The negative polarity of a battery 26 is connected to the grid 23 and the positive polarity is connected in series with a resistance 27 to the filament 21. A. transformer 28 has its secondary 29 connected across 13'and one end of 12 and its primary 30 has one end connected to the line 17 and the other end connected to the plate 22. One end of the filament 21 is connected to the line 18. One end of the primary 30 may be connected in series with a resistance 31 to the grid 23 by closing three pairs of contacts on the switch, these contacts being described later. When'any of the contacts are open, the grid 23 is of negative polarity with respect to the filament 21 and the X-ray tube 10 will notbe energized.- When all of these contacts are closed the grid 23 is of positive polarity with respect to the filament 21 during each half wave that the line 17'is positive and the X-ray tube 10 will be energized during those half waves of the

source

17 and 18.

The time switch in Fig. 1 comprises a self-starting synchronous motor 32 driving a Worm 33 meshing with a worm gear 34 which rotates a gear 35. The

gears

34 and 35 rotate around a shaft 36 secured to a bracket 37 which is pivoted on stationary collars 38. The bracket 37' is normally held by a spring 39 against an adjustable stop 40.- One pair of contacts consists of a stationary contact 41 and a movable contact 42 carried by the bracket 37. An electromagnet 43 has a movable core 44 secured to the bracket 37. The motor 32 and the electromagnet 43 may be simultaneously energized from the

source

17 and 18 by closing a switch 45 which is normally held open by a spring 46. A circular gear 47 is free to rotate around a stationary shaft 48 secured to the time switch base represented by 49, Fig. 4. The teeth of the gear '47 are adapted to mesh with the teeth of the gear 35 but when the electromagnet 43 is not energized the spring 39 pulls the gear 35 away from the gear 47 and prevents them from meshing. Closing the switch 45 starts the motor 32 and energizes 43, thus pulling the bracket 37 downward against the tension of the spring 39 and tending to move the gear 35 toward the gear 47. The gear 35 can not move the necessary amount to bring it into mesh with the gear 47 until a projection on an adjustable bracket 50 lines up with one of the spaces between the teeth of the gear 35. This arrangement ofthe projection in-relation to the gear 35 is shown in Figs. 2 and 3.

In Fig. 3 the

gears

35 and 47 are shown as not meshing and in their relative positions when the coil 43 (Fig. 1) is not energized. The position of the bracket 50 is adjusted by the screws 51 so that the'bracket has its projection 52 under the teeth of the gear 35 with a slight clearance between them. When the switch 45, Fig. 1, is closed the gear 35 is brought into motion and also pulled toward the gear 47. Assuming that 52 does not happen to line up with one of the spaces between the teeth of 35, the latter will rotate with the bottom side of one of its teeth rubbing on 52 till the next space between the teeth lines up with 52, thus permitting the gear 35 to move toward the gear 47, and by suitably adjusting 50 the teeth of the gears 35- and 47 will mesh when this occurs. In Fig. 2 is shown the projection 52 lined up with one of the spaces between the teeth of the gear 35, thus permitting the latter to move into mesh wit the gear 47.

- Referring again to Fig. 1, the gear 47 has a small section of its periphe without teeth, this section being represente by 53. A ear 54 has its teeth out so that what is calle the pitch circle of a gear will form a logarithmic pitch curve, thus producing what is known as a logarithmic spiral gear. The gear 54 engages a similar gear 55. The gear 54 is secured to the gear 47 by screws 56. A gear 58 has its teeth, out so as to produce a logarithmic spiral gear and engages a similar gear 59. The pair of

ears

54 and 55 may be similar to or dissimilar from the pair of

gears

58 and 59. The gear. 58 is secured to the near 55 by screws 60. The

gears

54 and 59 are Tree to rotate around the

gears

55 and 58 are free to rotate around the stationary shaft 57. A helical spring 61 is placed between 57 and 58 to oppose movement of the latter in a counter clockwise direction. The gear 59has two elements secured to it, each element controlling a pair of contacts, these elements being represented by the

arms

62 and 63. A second pair of contacts .consists of a contact 64 carried by a pivoted movable member 65 and a stationary contact 66 adjustable as to position by a screw 67. A spring 68 pulls member 65 downward, thus tending to effect closing of contacts 64 and 66. In its normal stationary position the arm 62 engages the member 65 to keep the contacts 64 and 66 normally open. A third pair of contacts consists of a contact 69 carried by a metallic member 70 which is free to move around the shaft 48 and another movable contact 71 carried by ametallic stem 72 securedto a metallic member 73 also free to move around the shaft 48. The stem 72 is insulated from member 73 by suitable means (not shown) that are well known to those skilled in the art. A helical spring 74 is placed between 48 and 70 for keeping the contacts 69 and 71 normally closed. The arm 63 is adapted to engage during its movement with the member 70 to effect the opening of the contacts 69 and 71. The three pairs of contacts are connected in series in the following manner. Assume 5 and 76 to represent terminal posts on the time switch. A lead 77 connects post to contact 41.- A lead 78 connects contact 42 to a stationary copper plate 79 on which slides a copper plate 80 secured to the member 73 .but in sulated therefrom by suitable means (not shown) that are well known to those skilled in the art. A lead 81 connects the plate 80 to the stem 72. The metallic member 70 slides on a stationary copper plate 82 and a lead 83 connects 82 to the contact 66. A lead 84 connects contact 64 to the post 76. The indicating arm 85 is secured to the member 73. A scale plate 86 having stop pins 87 and 88 coshaft 48 and the operates with the arm 85. The plate 86 has non-uniforml s aced apart numbers forming a logarit mic scale best represented in Fig 4.

' n the particular switch illustrated I have preferred to represent a maximum time interval of 25 seconds for the timing function of the switch, as represented by the numeral 25 adjacent to the stop pin 88. The numbers on the scale plate 86 in Fi 4 indicate the time interval involved in e timing function of the switch when the arm 85 points to that number. For equal difierences in time the greatest spacings between numbers occur at the beginnin of theti'ming range and the smallest spacings between'numbers variations in numbers are arranged to form a logarithmic scale because in this particular form of my invention I have preferred to use logarithmic gears.

'45 simultaneously starts the motor 32 and energizes the electromagnet 43 which closes the

contacts

41 and 42. The motor is connected to rotate gear 47 clockwise. The bracket 50, Fig. 2, is adjusted so that the projection 52 lines'up with one of the spaces between the teeth of the gear 35 at substantially zero voltage on the alternating wave of 17 and 18 and the meshing of the

gears

35 and 47 starts rotation of

the'arms

62 and 63 in a clockwise direction. The contact 66 is adjusted b screw 67 so that the necessary movement 0 the arm 62 to permit closing of the contacts 64 and 66 will be such that they close at substantially zero voltage on the alternating wave. It is obvious that the energization of the tube 10 will be started at substantially zero voltage on the alternating wave irrespective of the position of the contacts 69 and 71 as determined by the position of arm 85 since these'conta'cts' are always normally closed. Assume that the switch 45 was closed with the indicating arm 85 at the O'mark as shown. This 0 mark is so placed that when the arm 62 has moved occur at the end of the timing range. The

spring 61 returns the

gears

47, 54, 55, 58 and 59 to their normal positions, the contacts 64 and 66 are back to their normally open condition and the contacts 69 and 71 are back to their normally closed condition. No harm can result if the switch 45 is not opened because when the gear 47 has rotated one revolution the section 53, (without teeth) comes adjacent to the gear 35, thus preventing further rotation of gear 47, and in this position the

gears

54 and 55 remain in mesh and the same is true of the

gears

58 and 59. When the switch 45 is eventually opened the gears and contacts return to their normal positions.

Energization of the tube 10 is obtained by closing the.switch 45 after the arm 85 has been moved clockwise from the 0 mark, thus moving the. contacts 69 and 71 clockwise which causes the arm 63 to open these contacts at some desired time interval after the contacts 64 and 66 are closed. It is obvious that the distance the arm 85 is moved from the 0 mark to obtain a desired time interval between the closing of the contacts 64 and 66 and the opening of the contacts 69 and 71 will depend on the velocity of the arm 63 during the time interval. In accordance with my invention I cause the arm 63 to move at a constantly varying velocity with the maximum velocity at the beginning of the timing range so as to obtain large movements of the arm 85 from the 0 mark for small time intervals. I obtain this result as follows: The gear 47 rotates at a substantially constant velocity but there is a constantly changing ratio of speeds between the gears 54 and '55 and between the gears '58 and 59. To give a specific example, assume that the maximum and minimum distances from the pitch lines of the teeth of the

gears

54, 55, 58 and 59 to the centers of the shafts about which they respectivelyrevolve are 3" and 1" respectively. For convenience, the distance from the pitch line of any of these gears to the center of the shaft about which the gear revolves is termed pitch radius. In the position shown in Fig. 1, the

gears

54 and 55 mesh with the gear 54 having a pitch radius of 3 and the gear 55 having a pitch radius of 1" at their axis of engagement and the same is true with respect to the

gears

58 and 59. At this position the gears 55 and '54 have a speed ratio of 3 to 1 and the same is true with respect to

gears

59 and 58, thus giving a 9 to 1 ratio between the'speeds of the

gears

59 and 54. Rotation of the gear 47 from the position shown causes a reduction in the pitch radius of the gear 54 and an increase of the pitch radius of the gear 55 at their axis of engagement and the same is true with respect to the

gears

58 and 59. This dep from the 9 to 1 ratio. When the gear 47 has determined in the following manner.

made one revolution the

gears

54 and 55 mesh with the gear 54 having a pitch radius of 1" and the gear 55 having a pitch radius of 3" at their axis of engagement and the same is true with respect to the

gears

58 and 59, thus giving a 1 to 9 ratio between the speeds of the

gears

59 and 54. It is clear that the arm 63 will move at a constantly varying velocity with its maximum velocity at the eginning of its travel and its minimum velocity at the end of its travel. It is also clear that since in this preferred embodiment of my invention I employ logarithmic spiral gears, therefore the arm 63 will move at a constantly varying velocity with a constant change in velocity per unit of time. By choosing suitable values of'maximum and minimum pitch radii of the

gears

54, 55, 58 and 59 and a suitable diameter of scale plate 86, it is possible to have a scale plate over which the arm 85 is moved a considerable distance to obtain a very small time interval between the closing of the contacts 64 and 66 and the opening of the contacts 69 and 71, and with the arm. 85 moved continually decreasing amounts to obtain equal increments in the time interval. A scale of this type is partly shown in Fig. 1 and fully shown in Fig. 4. It is seen that this scale permits a very high degree of accuracy in the setting of the switch for small time intervals and a moderate degree of accuracy for reasonably large time intervals.

Assume that the arm 85 (Fig. 1) is set on the .05 mark and the switch 45 is closed. The

motor 32 and the coil 43 are energized, the contacts 64 and 66 close at substantially zero voltage in the alternating wave of the

source

17 and 18, the contacts 69 and 71 open .05 second after the contacts 64 and 66 closed and the tube 10 is energized during half the alternations corresponding to .05 second which in the assumed case equals 3 alternations. When theswitch 45 is opened the contacts 41' and 42 are opened before the arm 63 has moved back far enough to permit the contacts 69 and 71 to close, thus preventing the tube from being energized during the interval elapsing between the closing of the contacts 69 and 71 and the opening of the contacts 64 and 66 as the parts are returning to their normal positions. Any time interval Within the capacity of the time switch may be obtained by moving the arm 85 to indicate the number corresponding to the time interval desired. The switch can be easily arranged to give highly accurate indications of smaller time intervals than .05 second with timing ranges of any desired value. The accuracy of any setting mayAbe sume the arm 85 set at the .05 second mark. This corresponds to a determinable number of revolutions of the motor shaft since its synchronous speed is known. It is only necessary to turn the motor shaft by hand and count its number ofrevolutions between the closing of the contacts 64 and 66 and the o of the contacts 69 and 71 and if the count turns agree .with the predetermined turns, the accuracy is 100%. It is obvious that this method can be used for initially determining the spacings of the numbers on 86.

The starting of the motor with the gears 47 'and 35 out of mesh permits the motor to accelerate rapidly and by suitably adjusting 67 the motor 32 is up to synchronous speed before the contacts 64 and 66 close and at the same time these contacts close at substantially zero voltage of

source

17 and 18. These results are obtained without interfering with the accuracy of the time switch and at the same time the time switch is operated for only a slightly longer period than that necessary to accomplish its timing function, thus greatly reducing wear on the parts 7 gave very satisfactory results.

and simplifying lubrication problems. I have actually constructed a time switch as illustrated and have tested it in connection with the control of electric circuits and it I have illustrated my time switch with the arm 63 driven at a constantly varying velocity during its entire travel but it is obvious that in some cases it maybe desirable to arrange the motion transmitting means between the motor and the arm 63 to drive the latter at a constantly varying velocity during a ortion of its travel and at a constant velocity during the remainder of its travel. For mechanical convenience I have provided two

separate arms

62 and 63, but obviously they may be combined into one arm by suitably spacing the two pairs of contacts operated by these arms or if desired, the arm 62 and the contacts 64 and 66 may be arranged otherwise than as shown since it is not necessary to drive the arm 62 at a constantly varying. velocity to obtain the results of my invention. I have illustrated my time switch with logarithmic gearsand certain normal contact relations at each pair of contacts, which relations are changed to accomplish a specific purpose, but obviously other motion transmitting means than those shown may be employed to accomplish my invention'and other normal contact relations at the contacts may be desired for another of the many uses for which time switches are employed. If desired the engagement of the stationary and movable arms on the switch may be used otherwise than for controlling an electrical circuit. I, therefore, wish it understood that the embodiment represented is merely illustrative of the principles of'my invention as applied for a specific use and that all modifications falling within the true spirit and scope of my invention are intended to'be included within the scope of the appended claims.

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

1. A time switch comprising driving means having a substantially constant velocity, two pairs of cooperating contacts, means operated by said driving means for efiecting a change in the normal contact relationship of one pair of contacts, a movable element for efiecting a change in the normal contact relationship of the second pair of contacts at'a desired time interval after the change in normal contact relationship of the first pair of contacts, and motion transmitting means between the driving means and the movable element for driving the latter at a constantly varying velocity.

2. The combination with a source of alternating current and a circuit to be connected thereto, of a time switch comprising driving means having a substantially constant velocity, two pairs of cooperating contacts for connecting said circuit to the source of alternating current, means operated by said driving means for effecting a changelin the normal contact relationship of one pair of contacts, means for effecting said change at a desired point in the alternating wave of said source, a movable element for efiecting a change in the normal contact relationship of the second pair of contacts at a desired time interval after the chan e in the normal contact relationship of the rst pair of contacts, and motion transmitting means between the driving means and the movable element for driving the latter at a constantly varying velocity.

3. A time switch comprising driving means having a substantially constant velocity, a pair of cooperating contacts, means operated by said driving means for efl'ecting a change in the normal contact relationship of said pair of contacts, a second pair of cooperating contacts, a movable element for effecting a change in the normal contact relationship of the second pair of contacts at a desired time interval after the change in the normal contact relationship of the first pair of contacts, motion transmitting means between the driving means and the movable element for driving the latter at a constantly varying velocity, adjusting means for changing the distance traveled by the movable ele-* ment from the instant of the chan e in the normal contact relationship of the rstpair of contacts to the instant of the change in normal contact relationship of the second pair of contacts, an indicating arm secured to the adjusting means, and a scale having nonuniformly spaced markings cooperating with the indicating arm to indicate the time interval between the above mentioned instants.

4. A time switch comprising driving means havingla substantially constant velocity, two pairs of cooperating contacts, means ;ting means between the driving means and the movable element, the saidmotion transmitting means containing at least two rotatable bodies having non-circular peripheral contact surfaces in engagement with each other.

5. A time switch comprising driving means having a substantially constant velocity, two pairs of cooperating contacts, means operated by said driving means for eifecting a change in the normal conta'ct relationship of one pair of contacts, a movable element for efiecting a change in the normal contact relationship of the second pair of contacts at a desired time interval after the change in the normal contact relationship of the first pair of contacts, and motion transmitting means between the driving means and the movable element, the said motion transmitting means containing at least two rotatable gears engaging each other with a constantly varying ratio of pitch radii at their axis of engagement during rotation of said gears.

6. A time switch comprising driving means having a substantially constant velocity, two pairs of cooperating contacts, means operated by said driving means for effecting a change in the normal contact relationship of one pair of contacts, a.- movable element for effecting a change in the normal contact relationship of the second pair of contacts at a desired time interval after the change in the normal contact relationship of the first pair of contacts, and motion transmitting means between the driving means and the movable element, the said motion transmitting means containing at least two rotatable engaging gears having similar logarithmic pitch curves.

7. A time switch comprising driving means having a substantially constant velocity, a pair of cooperating contacts, means operated by said driving means for effecting a change in the normal contact relationship of said pair of contacts, a second pair of cooperating contacts, a movable element for.

effecting a change in the normal contact relationship of the second pair of'contacts at a desired time interval after the change in the normal contact relationship of the first pair of contacts, motion transmitting means between the driving means and the movable element for driving the latter at a constantly varying velocity, the said motion transmitting means containing at least two rotatable engaging gears having similar logarithmic pitch. curves, adjusting means for means having a substantially constant velocity, two spaced apart pairs of cooperating contacts, biasing means to produce the normal contact relationship of each pair of contacts, two movable elements normally maintained in a stationary position one of said elements being adapted to eflect during its movement a change in the normal contact relationship of one pair of contacts and the other element being adapted to effect dur- ,ing its movement a change in the normal contact relationship of the second pair of contacts, means for adjusting the spacing between said two pairs of contacts so that the change in contact relationship of said pairs of contacts occurs at diflerent time instants, and motion transmitting means between the driving means and the movable elements for driving the latter at a constantly varying velocity.

9. A time switch comprising driving means having a substantially constant velocity, a pair of cooperating contacts, a movable arm normally held in a stationary position to keep said contacts normally open, biasing means to close said contacts after a predetermined movement of said arm, a sec ond movable arm normally held in a stationary position, a second pair of contacts normally held closed and adapted to be opened by the movement of the second movable arm at a desired time interval after the closing of the first pair of contacts, and motion transmitting means between the driving means and the movable arms for driving the latter at a constantly varying velocity.

10. A time switch comprising driving means having a substantially constant velocity, a pair of cooperating contacts, a movable arm normally held in astationary position to keep said contacts normally open,

biasing means to close said contacts after a predetermined movement of said'arm, a second movable arm normally held in a stationary position, a second pair of contacts normally held closed and adapted to be openedby the movement of the second movable arm at a desired time interval after the closing of the first pair of contacts, motion transmitting means between the driving means and the movable arms for driving the latter at a constantly varying velocity, adjusting means for-changing the spacing between the two pairs of contacts, an indicating arm secured to said ad'usting means, and a scale havin non-uni ormly spaced markings cooperating with the indicating arm for indicating the time interval between the closing of the normally 0 11 pair of contacts and the opening of tii: normally closed pair of contacts.

11. A time switch comprising drivin means having a substantially constant velocity, apair of cooperating contacts, a movable arm normally held in a stationary position to keep said contacts normally open, biasing means to close said contacts after a predetermined movement of said arm, a second movable arm normally held in a stationar position, a second pair of contacts norma y held closed and adapted to be 0 ned by the movement of the second movabl arm at a desired time interval after the closing of the first pair of contacts, a circular gear rotated by said driving means, a pair of engaging gears having similar logarithmic pitch curves, one of said pair of gears being secured to the circular gear, a second pair of engaging gears having similar logarithmic pitch curves, one of said second pair of gears being secured to the other of the first mentioned pair of gears and the other of the second mentioned pair of gears carrying said movable arms, the engaging relationship of said pairs of gears being such that the movable arms are driven at a constantly varying velocity.

12. The combination with a source of current, of a time switch comprising an electric motor, two spaced apart pairs of cooperating contacts, biasing means toproduce the normal contact relationship of each pair of contacts, movable means normally maintained in a stationary position, said movable means being adapted to effect during its movement a change in the normal contact relationship of one pair of contacts at one instant and the second pair of contacts at a later instant, means for connecting said motor to-said source, a gear rotated by said motor, a second gear adapted to engage with the first mentioned gear, means for normally keeping said gears disengaged, motion transmitting means between the second mentioned gear and the movable means for driving the latter at a'constantly varying velocity, means for causing engagement of said gears after said motor is connected to said source, means for delaying the change in the normal contact relationship of the first pair of contacts until after said motor is running at its normal speed, and means for returning said-movable means to its normal. stationary position when said motor is deenergized.

13. The combination with a source of alternating current and a circuit to be connected thereto, of a time switch comprising a syn.- chronous motor, two spaced apart pairs of cooperating contacts, biasing means to promentioned gear, means for normally keeping said gears disengaged, means to cause en agement of said gears at a predetermined point in the alternating wave of said source, motion transmitting means between the second-mentioned gear and the movable means for driving the latter at a constantly varying velocity, means for adjusting the distance traveled by the movable means prior to its efiectin the chan e in the normal contact relationshlp of the rst pair of contacts whereby the lastmentioned change occurs at said predetermined point in the alternating wave of said source, and means for returning said movable means to its normal stationary position when said motor is deenergized 14. The combination with a source of alternating current and-a circuit to be connected thereto, of a. time switch comprising a synchronous motor, two spaced apart pairs of cooperating contacts, biasing means to produce the normal contact relationship of each pair of contacts, movable means normally maintained in a stationary position, said movable means being adapted to efiect during its movement a change in the normal contact relationship of one pair of contacts at one instant and the second-pair of con- Vtacts at a later instant, means for connecting said circuit to said source through said two pairs of contacts, means for connecting the motor to said source, a gear rotated by said motor, a second gear adapted to engage with the first-mentioned gear, means for normally keeping said gears disengaged, a stationary projection capable of fitting into any of the spaces between the teeth of the first-mentioned gear, said projection being placed adjacent to and underneath the first-mentioned gear to permit the latter to move into en-' gagement with the second-mentioned gear only when the projection lines up with any of said spaces, means for adjusting the position of the projection to permit engagement of said gears at a predetermined point in the alternating wave of said source, an electromagnet for moving the first-mentioned gear into engagement with the second-mentioned gear, connecting means for energizing said electromagnet from said source, motion transmitting means between the second-mentioned gear and the movable means for driving the latter at a constantly varying velocity, means for adjusting the distance traveled by the movable means prior to its effecting the change in the normal contact relationship of the first pair of contacts where- 5 by the last-mentioned change occurs at said predetermined point in the alternating wave of said source, and means for returning said movable means to its normal stationary position when said electromagnet is deenergized. I

15. Apparatus for controlling the time interval between two operationson an external mechanism, said apparatus comprising driving means having a substantially constant velocity, two adjustably spaced apart normally stationary members, movable means normally maintained in a stationary position, said movable means being adapted to engage at one instant during its travel with 9 one of the stationary members to efiect one of said operations and to engage at a later instant with the second stationary member to effect the other of said operations, and motion transmitting means between the driving means and the movable means for driving the latter at a constantly varying ve locity. I 16. The combination with a source of current, of a. time switch comprising an electric motor, two spaced apart pairs of cooperating contacts, biasing means to produce the normal contact relationship of each pair of contacts, movable means for effecting a change in the normal contact relationship of one pair of contacts at one instant and of the other pair of contacts at a later instant, a third pair of contacts, biasing means to produce the normal contact relationship of the third pair of contacts, an electromagnet having a movable core for effecting a change in the normal contact relationship of the third pair of contacts when the electromagnet is energized, motion transmitting means between the motor and the movable means for driving the latter at a constantly varying velocity, and means for connecting the motor and electromagnet to said source and for simultaneously disconnecting the motor and electromagnet from said source.

In witness whereof, I have hereunto set my hand this 11th day of November, 1930.

. WILLIAM K. KEARSLEY.