US2277411A - Step-up switch - Google Patents

Description

` March 24, 1942. T. oBszARNY 2,277,411

STEP-UP swITcH Filed Dec. 22, 1938 4 sheets-sheetv 1 March 24, 1942. T. oBszARNY 2,277,411

' STEP-UP swITcH Filed Dec. 22, 193s 4 sheets-sheet 2 aj. fa

MM szozzzgy T. oBszARNY 2,277,411

STEP-UP SWITCH Filed Dc. 22:, 195s March 24, 1 942.

4 sheets-sheet 3 March 24, 1942. T OBSZRNY 2,277,411

ySTEP-UP SWITCH Filed Deo. 22, 1958 4 Sheets-Sheet 4 Z4 a f2/96. 5. if A v 6 g l .1,4 ff- 'IL 9 7 Patented Mar. 24, 1942 STEP-UP SWITCH Thedore Obszarny, Chicago, Ill., assignor to Mfg. Co., Chicago, Ill., a cor- Guardian Electric poration of Illinois Application December 22, 1938, Serial No. 247,207

8 Claims.

vber of different types of apparatus, such as in signs, signal systems, control systems, communication systems, games and other types of equipment. One of the objects of thisl invention is to provide a novel, simple, compact step-up switch which is ecient andpositive in operation, and rela- `tively inexpensive to manufacture.

Another object is to provide an improved switch of the character indicated, having spring means for returning the contact arm to starting position, under control of mechanical timing means, which permits step-by-step advancement of the contact arm only as long as the means for moving the arm is actuated successively Within predetermined periodic intervals of time.

A further object is to provide an improved switch of the character indicated, having a plurality of series of contacts and separate contact arms for each series, arranged for step-by-step registration with the respective series of contacts, and driving means including separately actuated elements for moving said arms sequentially and independently of each other.

Still another object of the invention is to provide an improved switch of the character indicated, having two series of contacts and separate contact arms therefor, arranged for stepby-step registration with said contacts, separately actuated elements for moving said arms sequentially and independently of each other, together with driving means for moving said elements in step-by-step fashion, said elements being formed for causing said driving means to rst operate upon one for a predetermined number of actuations and then upon the other of said elements.

Other objects and advantages of the present invention will appear from the following descrip-l tion, taken in connection with the accompanying Fig. 1 is a plan view of the step-up switch bodying the present invention.

Fig. 2 is a plan view of the switch looking from the opposite side with respect to Fig. 1.

Fig. 3'is a side elevation of the switch.

Fig. 4 is a view similar to Fig. 1, on an enlarged scale, with parts broken away and omitted, showing the mechanism in a position of adjustment in which the primary contact arm has beenI 'moved to its anal position of adjustment and the driving pawl is shown in position ready to coinmence actuation upon the secondary ratchet wheel for moving the secondary contact arm in step-by-step fashion.

Fig. 5 is a fragmentary view similar to Fig. 4, with portions broken away to show details of -shaft Il.

construction, with the parts in position of adjustment showing the driving pawl operating upon the secondary ratchet wheel in the process of adjusting the secondary l,contact arm in stepby-step fashion. l

Fig. 6 is an enlarged View similar to Fig. 4, with certain parts omitted for clarity, showing the parts in position of adjustment at which the driving pawl is engaging the secondary check pawl to release the secondary ratchet wheel for returning same, together with the secondary contact arm, to starting position.

Fig. 7 is a top view of the switch mechanism.

Fig. 8 is a vertical section through the switch, taken as indicated at line 8--8 on Fig. 4.

Fig. 9 is a perspective view of the primary and secondary ratchet wheels.

Fig. 10 is a sectional view through the me chanical timing mechanism, taken as indicated at line III-I0 on Fig. 4.

As illustrative of one specific application or use of the step-up switch embodying the present invention, attention is directed to the disclosure on pages 11, 12 and 43y of October 1938 issue of.

Service Radio, published by Bryan Davis Publishing Company, New York city, New York, wherein an equivalent type of stepper unit is Yemployed for remotely controlling the operation journaled at right angles thereto a shaft or arbor II. Supported on the rear side of the panel, asl

may be seen in Figs. l, 4 and 5, is a primary set of contacts, indicated at I2, I2, I2b, I2c and I2d, which are carried on a panel of insulating material, indicated at I3, rigidly attached to said mounting member by screws I4. Cooperating with said set of primary contacts is a rotatable contact arm I5, for convenience hereinafter designated as the primary contact arm, which is staked to a bushing I6 loosely journaled on the Staked on the opposite end of said bushing is a primary ratchet wheel I8, and by virtue of which connection said ratchet wheel, bushing and primary contact arm are rotatable as a unit, in step-by-step fashion.

Mounted on the outer face of the mounting panel I0, by means of studs I9, is a disk 20 of insulatng material, on which is mounted a secondary series of contacts, indicated at 2I, 2|, 2lb, ZIC, 2Id, '2|e, 2|I and 2I8. It is to be understood that the outer ends of said contacts of both the primary and secondary groups are connected in a suitable manner, such as by soldering, to conductor wires, for completing portions of various electrical circuits to be controlled by the step-up switch, A secondary, rotata'ble contact arm 23 is staked to a bushing 24, which is rigidly attached by set screw 24a to the outer end of the shaft II for rotation therewith. The secondary contact arm 23 is controlled by, and movable as a unit with, a secondary ratchet wheel 26, in step-by-step fashion; said ratchet mounting plate I0, in spaced-apart relation, as

seen in the drawings.

The primary and secondary ratchet wheels I8 and 26 are herein designated as such merely for convenience, but, as may be-seen in Fig. 9 of the drawings, these elements are in the form of .segments and have only a portion of their periphery formed with teeth. More particularly, in the primary ratchet wheel I8 there are three main teeth, as indicated at I8a, and one special tooth, as indicated at I8b. Therefore, when the driving pawl, which will hereinafter be described, engages with said teeth I8 sequentially, the ratchet wheel is moved, step-by-step, simultaneously moving the primary contact arm I over the corresponding contacts I2, I2b and I2C, and when the driving pawl engages the special tooth I8b the primary contact arm is moved into engagement or registration with the last of the contacts of the primary series, as indicated at I2d. The lower portion of the primary ratchet wheel is formed with a notch, as indicated at I8, to form a hook for the closed loop of a tension spring 32, the other end of which spring is secured to a stud 33, carried on a bracket 33a which, in turn, is secured to the mounting plate I0. The spring 32, when the ratchet wheel I8 is free, returns said ratchet wheel, together with the primary contact arm I5, to the starting position, such as indicated in Fig. 1. To arrest the ratchet wheel and primary contact arm in proper position, the ratchet wheel is formed with an abutment shoulder I8, which` engages a stop member 34 carried by the bracket member 33a.

It will be observed that the secondary ratchet wheel is formed with a multiplicity of teeth, indicated at 26, which, desirably, should correspond in number to at least the number of contacts comprising the secondary series of contact members. Said secondary ratchet wheel is also provided at its lower portion with an abutment shoulder 26b adapted to engage the stop 34 to arrest the ratchet wheel, together with the secondary contact arm 23, in an initial or starting position, as indicated in Figs. 2 and 4. It may be understood that said stop is formed of fibrous or like material, to reduce noise. The secondary ratchet wheel 26 is, when free, caused to be returned, together with the secondary contact arn, to a starting position bymeans of a coil spring 38, circumscribing the end of the shaft II, projecting rearwardly beyond the clamp plate 30, and having one end extending intoK a slot II8l formed in the end of the shaft, the vother end of said spring being fixedly secured to the clamp plate 30. It will now be apparent thatA as the shaft II is rotated, incident to the step-by-step primary and secondarymovement of the secondary ratchet wheel, said 'I6 spring becomes tensioned, so that upon disengagement of the secondarv ratchet wheel, by the holding means hereinafter to be described, said shaft, together with the secondary ratchet wheel 26, and secondary contact arm 23, is causen' to return to starting position. It will be noted from the drawings, particularly Fig. 4, that the radius defining the teeth of the secondary ratchet wheel is substantially less than the radius of 'the root of the teeth I8a of the primary ratchet wheel. The purpose of this constructional difference will be apparent in connection with the description of the action of the driving pawl, to be hereinafter described.

The driving means for moving the primary and secondary ratchet wheels in step-by-step fashion includes an electro-magnet 40 mounted in a bracket 4I which, in turn, is secured to the mounting plate I0. Said electro-magnet includes a core 42, with which cooperates an oscillatable armature 43, pivotally mounted at its lower end in the bracket 4I and yieldingly urged to its outermost position, as seen in Fig. 4, by means of a spring 44 having one end connected to the lower end of the armature, and the opposite end to a lug 4IEL of said bracket 4I. The upper endv of the armature is provided with a bracket 46 in the form of a hook, engaging a flange of the end of the electro-magnet for limiting the -outward movement of the armature with respect to the core 42. Rigidly connected to, and extending upwardly from, said armature is a carrier bracket 43, which is formed with a pair of spaced-apart ears 48a, in the upper ends of which are journaled the ends of a U-shaped bale or driving pawl 5U which, for convenience, is formed of a piece of relatively rigid wire. Said driving pawl is yieldingly urged downwardly with the closed end thereof in position for engaging the teeth of either the primary or secondary ratchet wheels by means of a coil spring 5I having one end connected to and seated in a notch 5I)1 formed in one of the legs of the bale-like driving pawl, the opposite end of said spring being connected to the carrier bracket 48. It will now be apparent that as the' electro-magnet is energized the attraction of the armature 43 to the core 42 moves the closed end of the bale-like driving pawl into engagement with the teeth of the ratchet wheels. To insure maintaining the driving pawl in position for properly engaging said teeth of the ratchet wheels I provide a stop plate 52 rigidly attached by astud 53 to the mounting plate, in a plane intermediate the two ratchet wheels, as may be seen in Fig. 3. The outer end of said member 52 is formed as a finger-grip to permit convenient adjustment of said member 52 in the Initial assembly of the switch unit.

It will now be apparent that said driving pawl 50, upon being successively reciprocated by energization of the electro-magnet, advances the primary ratchet wheel I8, together with the primary contact arm I5, in step-by-step fashion, by engagement with the ratchet wheel teeth I8BL and the special tooth I8b and, after movement of theratchet wheel I8 by the driving pawl engaging the special tooth I8", said ratchet wheel is positioned, as seen in Fig. 4, so that in the next actuation of the driving pawl the closed end thereof rides beneath said special tooth and engages the teeth 26a of the secondary ratchet pawl 26, for advancing same, together with the secondary contact arm 23, in step-by-step adjustment. It is to be understood, of course, that during the reciprocating action of the driving Co-axially mounted on a stud 55 secured to the rear side of the mounting plate I are transaxially .spaced apart, primary and secondary check pawls 56 and 51, each having laterally extending lugs 56a and 518, respectively, for engagement in the teeth of the corresponding primary and secondary ratchet wheels I6 and 25, as may be seen in Fig. 8. The primary'check pawl is of bell crank type, including a rearwardly extending lever arm 56h, the end of which is formed with a hook 56 for engaging the loop end of a coil spring 58, the opposite end of which spring is secured by a pin 58 to the mounting plate. It will be apparent that normally the spring 58 tends to urge the lug 56 of the check pawl 55 into engagement with the teeth of the primary ratchet wheel. The extreme end portion ofthe arm 55b is formed with a laterally extending lug 56dwith which engages the end of a spring-pressed sectorrack 59 of a mechanical timing mechanism, to be hereinafter described. At this time it may suillce to say that usaid segment is normally spring-pressed downwardly on said lug 56d to overcome the action of the coil spring 56, and normally maintains the lug 56a of the check pawl out of engagement with the teeth of the ratchet wheel. The secondary check pawl 51 is formed at its rear lower portion with a hook 51b for engagement by the closed end of aspring 66', the opposite end of which is connected to said lug 56d of the lever arm 55h of said primarycheck pawl. By virtue of such Aarrangement the spring 60 normally maintains the check pawl 51 in engage ment with the teeth of the'secondary ratchet wheel 26 for maintainingsame, together with its secondary contact arm 25, in the last position of step-by-step adjustment. The forward end or nose of the secondary check pawl 51 is formed as a cam 51 disposed in the path of travel of the closed end of the bale-like driving pawl 50 during the movement of said pawl ,into engagement with the special tooth IBI of the primary ratchet ,wheell IE which, it will be apparent, and as seen in Fig. 6, raises the driving pawl slightly above its normal path of movement so that it engages cam-wise with said cam end 51 of the check pawl, lifting the lug 51li out of engagement with the teeth 2lia of the secondary ratchet wheel, thereby permitting said secondary ratchet wheel, together with the secondary contact arm 23. to be returned to starting position under iniiuence of spring 36. It will be noted that this action takes place when the primary contact arm I5 and primary ratchet wheel I6 arrive at their nal position of adjustment, at which said arm engages the last contact member, indicated at I2d, of the primary series It will now be clear, as above stated, that during the rst four continuous reciprocations of the driving pawl 50, said pawl first engages the three teeth I6a and then the special tooth I8b of the primary ratchet wheel I6, advancing said ratchet wheel step-by-step for disposing the primary contact arm I5 in registration with contact I 2d of the primary contact series; and during the last actuation of the driving pawl infengag- King the special tooth I8" of the primary ratchet wheel. said driving pawl acts cam-wise against the end of the secondaryJ check pawl 51., lifting same 'out of engagement with the teeth `of the secondary ratchet wheel 26', permitting same, together with the secondary contact arm 23, to be returned' to starting position. In the next successive actuation of the driving pawl 5U, said pawl passes beneath the special tooth Illb of the primary ratchet wheel, and engages in thel rst tooth 26 of the secondary ratchet wheeLthereby advancing said ratchet wheel 26 simultaneously with the secondary contact arm 23. And any number of successive actuations thereafter of the driving pawl causes stepby-step advancement of the secondary ratchet wheel with the secondary contact arm to a desired position of adjustment for completing a portion of some predetermined electrical circuit through a corresponding contact with which the secondary contact larm is per` mitted to register. There may be occasions when 1t is desiredto complete merely a portion of some predetermined electrical circuit, including one of the respective contacts I2, I2h; I2c or I2, of the primary set of contacts, in which case the driving pawl 1s actuated a corresponding number of times to position the primary contact arm I5 in registration with the proper contact of said series. It is to be understood that the positioning of the respective contact arms in engagement Qwith a predetermined contact of either of the respective series of contacts is determined by the number of successive actuations of the driving pawl caused by magnetization of the' electro-magnet 46 and any convenient, wellknown means may be employed for imparting electrical current impulses u to the electro-magnet in a predetermined `number of uniformly timed intervals. For proper control of the primary check pawl 56 by the timer mechanism hereinafter to be described, it has been found that the rate of impulses of electric. current imparted to the electro-magnet for satisfactory and proper functioning of t-he mechanism, should be between five and ten pulsations per second. It will be manifest that the rate of pulsations will also be the rate of actuation of the contact arm in moving from contactv to contact. Therefore, it is apparent that such .a relatively short period of time of completion of the electrical circuit by the contact arm moving from contact to contact is insuicient generally speaking, to cau'se operation of the mechanism actuated by the electrical circuit thus completed. '.Ihe reason for this relatively rapid rate of pulsations will be apparent from the description of the timing action employed for control- 1mg the primary check pawl.

The timing mechanism herein disclosed is of a mechanical nature, and includes a frame member 6I mounted on studs 62 for supporting same in spaced relation to the mounting plate I0.

` Supported from this frame member by means of studs 63 is an auxiliary frame or support 64, between which frame members is Journaled a shaft 65 on which is loosely mounted a pinion 66, meshed with the sector rack 59. Surrounding said shaft 65 is a coil spring 61 having one end secured in said pinion, as seen in-Fig. 10, and the opposite end of which frictionally engages the hub of an escapement gear 68 journaled on the opposite end of the shaft 65. Journaled in said frame members 6I, 6I is another shaft 69, on which is rigidly mounted a disk 10 carrying a pair of diametrically, oppositely disposed, laterally extending pins 1|- positioned in close proximity to the toothed periphery of the gear 68. It will be understood that the escapement gear 68, together with the pins 1 I, acts somewhat as a brake to maintain a uniform speed of rotation of the pinion 66 when 'actuated bythe segment rack 59. By virtue of the construction described, the spring B'I constitutes a one way friction drive for the escapement gear 68, which is prevented from rotating in counterclockwise direction (as seen in Figure 4) by the pins 1I of the oscillatable disk 1I), during rotation of pinion 66 incident to the upward rocking movement of the segment gear 59. As the escapement gear 68 rotates, the disk 'I0 oscillates, first projecting one of the pins 'I0 into engagement with the teeth of the escapement wheel 68 and which pin is then cammed out of engagement due to the shape of the teeth of said wheel, causing the opposite pin to be Y the segmental rack 5S is rocked upwardly about the pivot 'I2 in the end of the frame 6I, thereby rotating the pinion 66, and due to the action of pins 1I of disk 10, the spring 6l cannot frictionally rotate the escapement wheel 68. Upon the return movement of the segment rack 59 the spring B1 is permitted to frictionally drive the escapement wheel 68, which is controlled by the action of pins II of the oscillatable disk 10, and thereby causes said wheel 68 to rotate at a uniform rate of speed. Such rotation of the wheel 1 68 tends to maintain -a uniform speed of return movement of the segment rack, and which thereby provides a definite timing action for the period of time that said primary check pawl 56 is permitted to function to retain the primary ratchet wheel I8 in thelast position of adjustment attained by actuation of the driving p-awl 50.

Said segment rack, as shown, is a two-piece construction, including a supporting body 14, to which the rack proper is pivoted at 15. Said body portion 'I4 includes a vleg portion projecting downwardly from the mainV pivot 'I2 in position to be engaged by the carrier bracket 48 when the armature 43 is attracted to the core 42 of the electro-magnet, which action rocks the segment rack 59 in an upward direction, and which, as above described, disengages the end of the rack with the lug 56d of the primary check pawl, permitting the primary check pawl 56 to retain the primary ratchet wheel I8, together with the primary contact arm I5, in the last position of adjustment effected by actuation of the driving pawl 50. The segment rack 59 is held in proper position tothe pinion 66 by a coil spring 'I8 connected to lugs 59a and 14a of the respective parts of the rack unit. The rack unit, including the operating armV 16, is yieldingly urged to the position seen in Fig. 4 by means of a coil spring 8l), connecting a lug Hb of said body portion of the segment rack unit, and -a lug 6Ia of the frame member 6I of the timer mechanism.

The step-up switch constituting the present invention is positive in operation and is relatively simple in construction as compared to equivalent step-up switches for performing similar functions; in fact, the number of parts utilized are substantially less, and the cost of manufacture is greatly reduced as compared with the equivalent type units that are now commercially available.

Although I have herein shown and described a preferred embodiment of my invention, manifestly it is capable of considerable modification and re-arrangement of parts without departing from the spirit and scope thereof. I do not,

therefore, wish to be understood as limiting this invention to the precise embodiment herein disclosed, except as I may be so limited in the appended claims.

I claim:

1. In a step-by-step positioning device, a primary ratchet wheel and a secondary ratchet wheel, said ratchet wheels being mounted for rotation independently of each other, a reciprocating pawl for driving said ratchet. wheels and adapted upon one or more of a predetermined number of actuations for rotating the primary ratchet wheel in step-by-step adjustment, and means associated with and movable by the primary ratchet whefel into the path of travel of the driving pawl after said predetermined number of actuations to preclude further movement of the primary ratchet wheel by said pawl, Whereby further actuation of said driving pawl rotates the secondary ratchet wheel in step-by-step adjustment.

2. In a step-by-step positioning device, a shaft, a primary ratchet wheel and a secondary ratchet wheel, said ratchet wheels being mounted on said shaft for rotation independently of each other, a reciprocating pawl for driving said ratchet wheels and adapted upon one or more of a predetermined number of actuations for rotating the primary ratchet wheel in step-by-stepadjustment, means associated with and movable by the primary ratchet wheel into the path of travel of the driving ypawl after said predetermn-ed number of actuations, to preclude further movement of the primary ratchet wheel by said pawl, whereby further actuation of said driving pawl rotates the secondary ratchet Wheel in stepby-step adjustment, one of said ratchet wheels being iixed on the shaft and the other free on said shaft, `spring means tending to rotate said shaft in opposition to operating direction of rotation of said fixed ratchet wheel, and spring means opposing movement of the loose ratchet Wheel in operating direction.

3. In a step-by-step positioning device, a primary ratchet wheel and a secondary ratchet wheel, said ratchet wheels being mounted for rotation independently .of each other, a reciprocating pawl for driving said ratchet wheels and adapted upon one or more of a predetermined number of actuations for rotating the primary ratchet wheel in step-by-step adjustment, means associated with and movable by the primary ratchet wheel into the path of travel of the driving pawl after said predetermined number of actuations to preclude further movement of the primary ratchet wheel by said pawl, whereby further actuation of said driving pawl rotates the secondary ratchet wheel in step-by-step adjustment, separate spring-pressed check pawls for the respective ratchet wheels, said last mentioned means comprising the last operating tooth of the primary ratchet wheel, formed as a cam for raising said driving pawl during its actuating stroke, and spring means for resetting said ratchet wheels to starting position, upon disengagement of said check pawls.

4. In a step-by-step positioning device, a primary ratchet Wheel and a secondary ratchet wheel, said ratchet wheels being mounted for rotation independently of each other, a reciproeating pawl for driving said ratchet wheels and adapted upon one or more of a predetermined number of actuations for rotating the primary ratchet wheel in step-by-step adjustment, and means comprising the last operating tooth of the primary ratchet wheel formed as a cam for raising said driving pawl after said predetermined number of actuations to preclude further movement ofthe primary ratchet wheel by said pawl, whereby further actuation of said driving pawl rotates the secondary ratchet wheel in step-bystep adjustment, the teeth of the primary ratchet wheel, comprising the angular range of movement of said wheel, being formed about a radius greater than the radius of the teeth of the secondary ratchet wheel, and the peripheral portion of said -primary ratchet wheel, beyond the last tooth thereof, and within the range of angular movement of the secondary ratchet wheel, being less than the radius of the teeth of said secondary ratchet wheel.

5. In a step-by-step positioning device, a primary ratchet Wheel and a secondary ratchet wheel, said ratchet wheels being mounted for rotation independently of each other, a recipro-4 cating pawl for driving said ratchet wheels and adapted upon one or more of a predetermined number of actuations for rotating the primary ratchet wheel in step-by-step adjustment, means associated with and movable by the primary ratchet Wheel into the path of travel of the driving pawl after said predetermined number of actuations to preclude further movement of the primary ratchet Wheel by said pawl, whereby further actuation of said drivingl pawl rotates the secondary ratchet wheel in step-by-step adjustment, separate spring-pressed check pawls for the respective ratchet Wheels, said last mentioned means comprising the last operating tooth of the primary ratchet Wheel, formed as a cam for raising said drivingpawl during its actuating stroke, and spring means for resetting said ratchet Wheels to starting position, upon disengagement of said check pawls, the end of the secondary check pawl being formed as a cam and disposed adjacent the path of travel of the driving pawl, for engagement by said driving pawl when the latter engages the cam tooth of the primary ratchet Wheel for disengaging said secondary'check pawl to permit return of the secondary ratchet wheel to starting position, preparatory to step-by-step adjustment thereof, upon continued actuation of the driving pawl.

6. In a step-by step device, a primary ratchet Wheel and a secondary ratchet wheel, said ratchet wheels being mounted for rotation independently of each other, a reciprocating pawl for driving said ratchet Wheels and adapted upon one or more of a predetermined number of actuations for rotating the primary ratchet Wheel in stepby-step adjustment, means comprising the last operating tooth of the primary ratchet Wheel formed as a cam for raising said driving pawl after said predetermined number of actuations to preclude further movement of the primary ratchet Wheel by said pawl, whereby further actuation of said driving pawl 'rotates the secondary ratchet Wheel in step-by-step adjustment, the teeth of the primary ratchet Wheel comprising the angular range of movement oi said wheel being formed about a radius greater than the radius of the teeth of the secondary ratchet Wheel, and the peripheral portion of said primary ratchet wheel, beyond the last tooth thereof, and within the range of angular movement of the secondary ratchet wheel, being less than the radius of the teeth of said secondary ratchet wheel, separate spring-pressed check pawls for the respective ratchetwheels, and spring means for resetting said ratchet Wheels to starting position, upon disengagement of said check pawls, the end of the-secondary check pawl being formed as a cam and disposed adjacent. the path of travel of the driving pawl for engagement by saidl driving pawl when the latter engages the cam tooth of the primary ratchet wheel for disengaging said secondary check pawl to permit return of the secondary ratchet wheel to starting position, preparatory to step-by-step adjustment thereof,

upon continued actuation of the driving pawl.

7. In a step-by-step positioning device, a primary ratchet wheel and a secondary ratchet Wheel, said ratchet Wheels being mounted for rotation independently of each other, a reciprocating pawl for driving said ratchet wheels and adapted upon one or more of a predetermined number of actuations for rotating the primary ratchet wheel in step-by-step adjustment, means associated with and movable by the primary ratchet wheel into the path of travel of the driving pawl after said predetermined number of actuations to preclude further movement of the primary ratchet Wheel by said pawl, whereby further actuation f said driving pawl rotates the secondary ratchet wheel in step-by-step adjustment, separate spring-pressed check pawls for the respective ratchet wheels, said last mentioned means comprising the last operating tooth of the primary ratchet wheel, formed as a cam for rais- .ing said driving pawl during its actuating stroke, spring means for resetting said ratchet wheels to starting position, upon disengagement of said check pawls, the end of the secondary check pawl being formed as a cam and disposed adjacent the path of travel of the driving pawl for engagement by said driving pawl when the latter-engages the cam tooth of the primary ratchet Wheel for disengaging said secondary check pawl to permit return of the secondary ratchet wheel to starting position, preparatory to step-by-step adjustment thereof, upon continued. actuation of the driving pawl, means for actuating said driving pawl including an electro-magnet, adapted to be energized at periodic intervals of time, and

7 having an oscillatable armature pivotally connected to said driving pawl, and spring means acting on said driving pawl to permit pivotal movement thereof upon encounter with said cam tooth of the primary ratchet wheel.

8. In a step-by-step positioning device, a ratchet wheel, a reciprocating pawlfor driving said ratchet wheel and adapted upon one or more of a predetermined number of actuations for rotating said Wheel in step-by-step adjustment, electro-magnetic means adapted to be energized at periodic intervals of time and having an armature operably connected to said driving pawl, a spring-pressed check pawl for said ratchet wheel, spring means for resetting said ratchet Wheel to starting position upon disengagement of the check pawl, and gear and pinion type timing mechanism for controlling said check pawl for preceluding resetting of said ratchet Wheel to starting position during the time that said driving pawl is being successively actuated by said electro-magnetic means within periodic intervals of time, said timing mechanism including a segment gear having an operating arm positioned for engagement by the armature ofl the electro-magnetic means for energizing said mechanism, and an abutment shoulder adapted to engage an arm of the check pawl for holding it out of engagement with said ratchet Wheel while said mechanism is deenergized.

THEDORE OBSZARNY.

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