US3722304A

US3722304A - Step-by-step drive for timer

Info

Publication number: US3722304A
Application number: US00185527A
Authority: US
Inventors: G Obermann
Original assignee: Controls Company of America
Current assignee: Eaton Corp
Priority date: 1971-10-01
Filing date: 1971-10-01
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27
Also published as: CA945395A

Abstract

The continuously driven drive disc carries a drive pawl and a retracting lever on the same pivot. The pawl is biased against the lever by a compressed spring. The lever is held in retractive position by a tension spring. The lever includes a cam which engages a tab (projecting from the timer end plate) to move the lever to an inactive position against the bias of the tension spring while the drive pawl is restrained from following by reason of engagement of a depending finger with a second tab. Continued rotation of the disc clears the finger from the second tab allowing the compressed spring to drive the pawl into engagement with the internal teeth on the timer cam drum thus driving the drum until the lever clears its tab and is retracted by the second (tension) spring. As the lever is retracted it picks up the pawl and retracts the pawl and the drive step is completed. The drive is more economical than the usual stored energy step drive but is more expensive than a creep-type drive. It makes possible variations in steps (degrees and frequency) and even continuous (rapid) drive.

Description

United States Patent [191 Obermann 5] Mar. 27, 1973 STEP-BY-STEP DRIVE FOR TIIVIER [57] ABSTRACT [75] Inventor: George Obermann, Niles, Ill. The continuously driven drive disc carries a drive pawl and a retracting lever on the same pivot. The pawl is [73] Asslgnee' glz z fi of Amenca M biased against the lever by a compressed spring. The at lever is held in retractive position by a tension spring. [22] Filed: Oct. 1, 1971 The lever includes a cam which engages a tab (projecting from the timer end plate) to move the lever to [21] 185527 an inactive position against the bias of the tension spring while the drive pawl is restrained from follow- 52] U.S. Cl ..74/112, 74/577 R, 74/575, ing y reason of engagement of a depending finger 74/577 SF with a second tab. Continued rotation of the (118C 51 Int. cl. ..G05g 1/00 elem the finger from the eeeehd ehewhg the 58 Field of Search ..74/568, 577,575, 142, 112, e f e ephhg hive the R engagement 7 4/1 16 with the internal teeth on the timer cam drum thus driving the drum until the lever clears its tab and is retracted by the second (tension) spring. As the lever [56] References cued is retracted it picks up the pawl and retracts the pawl UNITED STATES PATENTS and the drive step is completed. The drive is more economical than the usual stored energy step drive but n. is more expensive than a creep type driver It makes 3,678,769 7/1972 Holzer ....74/568 possible variations in Steps (degrees and frequency) g f and even continuous (rapid) drive. ems

Primary Examiner-Charles J. Myhr e Assistant Examiner-Wesley S. Ratliff, Jr. Attorney-John W. Michael et al.

3 Claims, 7 Drawing Figures STEP-BY-STEP DRIVE FOR BACKGROUND OF THE INVENTION In the interval timing art there are essentially two types of timers, the simplest being the creep-type timer where the timing cam is driven continuously. A drawback to this type of timer is the relatively long switching time encountered which can cause arcing and burning of the contacts. Furthermore, it is difficult, to say the least, to achieve sequenced actuation of various switches within a relatively short period of time. The step-type timer can achieve short switching time and within the actual step can achieve sequencing of switches. Of course, the longer the step the easier the sequencing problem. The step-type timer usually is a stored energy arrangement which is appreciably more expensive than the creep-type drive.

SUMMARY OF THE INVENTION The construction described in the Abstract makes possible a step drive which lies between the creep-type drive and the stored energy type drive in cost. The present drive makes possible variation of the time between impulses without changing the motor speed and without changing the switching time simply by changing the number of stationary tabs which can be engaged by the drive pawl and lever during one revolution of the disc. The step size can be varied with the controlling factors being the angular degrees between the teeth and the cam bank, the stationary tabs permitting angular engagement of the teeth and governed by the fact that the largest step size must be smaller than any two consecutive small steps. Thus the present drive, while more economical than the stored energy type drive, offers a considerable degree of design freedom.

DESCRIPTION OF THE DRAWINGS FIG. I is a schematicized plan view showing the general orientation of the basic parts.

FIG. 2 is a fragmentary, enlarged plan view showing a portion of the disc, the pawl, positioning lever, and the tabs on the end plate of the timer.

FIG. 3 is an exploded partial perspective showing the shape of the pawl and retracting lever more clearly and illustrating the orientation of these parts to an actuating tab.

FIG. 4 is a plan view with parts broken away showing the orientation of the parts at the start of a driving step with the retracting lever moved into inoperative position and the drive pawl retained in the inactive position.

FIG. 5 is comparable to FIG. 4 but shows the parts when the drive pawl has moved into engagement with the ratchet teeth on the inside of the timing cam drum, three of such teeth being shown.

FIG. 6 is a fragmentary section taken on line 6--6 in FIG. 5.

FIG. 7 is a section taken as indicated by line 7-7 on FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENT The timer drive motor 10 is mounted on the timer end plate 112 with its output gear 114 driving drive disc 16 through idler gear 18. The drive disc is rotated continuously but the timing cam drum 20 is driven intermittently. The cam drum is illustrated in a schematic manner showing one cam actuating switches 22, 24. Obviously in practice a plurality of cams actuate a plurality of switches according to a programmed sequence to control the washing machine components in the prescribed sequence.

Continuously rotating drive disc 16 is provided with a drive pawl 26 and a retracting lever 28 on a common pivot 29 as may be seen' in FIGS. 3 and 6. The pawl member has an upstanding pawl 30 and a depending finger 32. The pawl is designed to engage ratchet teeth 34 on the inside of the end of the timing cam drum as may be seen particularly in FIGS. 5 and 6. The depending finger is designed to be controlled by the positioning or control tab 38 bent upwardly from the end plate 12 of the timer. In FIGS. 2, 4, and 5 the pawl member 26 is biased by spring 40 compressed between the pawl member and abutment 42 on the retracting lever so as to urge the pawl in a counterclockwise direction about pivot 29 to a point when finger 32 butts against the edge of retracting lever 28. The retracting lever 28 includes a spring anchor 44 on one end permitting the tensioned spring 46 to urge the lever, pawl and spring assembly in a clockwise direction as viewed in FIGS. 2, 4, and 5. The other end of the spring is anchored on post 48 carried on the drive disc. Finger 32 depends from the pawl member 26 between the long arm of lever 28 and the edge of aperture 50 in the drive disc. The bottom of the lever is provided with a ramp-like projection or cam 52 which depends through the aperture 50 to engage the second tab 54 bent up from the end plate 12.

As the disc rotates from the position shown in FIG. 2, the depending pawl finger 32 arrives at a position inside tab 38 to prevent movement of the pawl and then cam 52 strikes tab 54 to cam the lever in a counterclockwise direction against the bias of tension spring 46 and compression spring 40. The pawl member is prevented from following so long as the depending finger 32 engages tab 38. As soon as the finger clears tab 38, however, the

compressed spring 40 drives the pawl in a counterclockwise direction to drive pawl 30 into engagement with the ratchet 34 and thus pick up the ratchet and start turning the cam bank 20. At this time the position ing lever is held in its counterclockwise position so as to not interfere with the pawl movement. As soon as the ramp 52 clears tab 54 the tensioned spring 46 is free to pull the lever in a clockwise direction to pick up pawl finger 32 to withdraw the pawl 30 from the ratchet teeth. This completes the step (the length of the step is determined by degrees of angular rotation between the time of engagement of a pawl with the ratchet and the time the pawl is withdrawn). The spacing between the teeth 34 may be varied so as to vary the angular step imparted. The limiting factor is that the largest step must be less than any two consecutive small steps.

If desired, additional pairs of stationary tabs may be located on the end plate so the cam bank may be advanced more than once per revolution of the drive disc to change the time between impulses without changing motor speed or switching time.

An additional feature should be pointed out. On the side of the drive disc adjacent the end plate there may be a peripherally facing cam configuration such as 56 I claim: l. A timer including a motor continuously'driving a drive disc,

a pawl pivotally supported on the disc and urged into driving position,

a retracting lever biased to a position in which it engages said pawl and prevents movement of the pawl into driving position while being movable to a position in which the pawl can move to its driving position if not restrained from such movement,

a timing cam including ratchetteeth,

said pawl being engageable with the ratchet teeth in its driving position,

first fixed actuating means positioned to be engaged by said lever as the disc rotates whereby the lever is moved to a position in which it no longer restrains movement of the drive pawl,

second actuating means initially engaged by the drive pawl to prevent the drive pawl moving to operating position while the positioning lever is moved to a position in which it does not restrain the drive pawl and then acting to release the drive pawl for movement under its bias into the driving position, said lever being subsequently disengaged from said first actuating means whereby the bias acting on the lever acts to retract the lever and retract the drive pawl from engagement with the ratchet 35 thereby terminatingthe drive step which was initiated by engagement of the pawl with said ratchet.

2. In a timer drive mechanism for imparting step-bystep movement to a timing cam, 1

a ratchet on the timing cam, a continuously driven drive disc,

a pawl pivotally supported on the disc for movement into and out of engagement with the ratchet and movable only in the direction of advance of the adjacent ratchet teeth and the associated timing cam,

means "normally retracting the pawl to an inoperative position in which it'is disengaged from the ratchet,

means for cyclically actuating the pawl into operative engagement with the ratchet to advance the timingcam a discreet distance comprising a step of the timing cam,

said retracting means being operative at the end of the discreet step to retract the pawl to said inoperative position.

3. A structure according to claim 2 in which said retracting means comprises a lever which is operative to engage the pawl and move the pawl to its inoperative position,

spring means biasing the lever to its retracted position, stationary means engageable with the lever as it rotates with the disc to move the lever to an inoperative position in which it is unable to restrain movement of the pawl, springmeans acting on the pawl in a direction to ena e the awl with said ratchet, me a s for r estraining movement of the pawl while said lever is being moved to its inoperative position and operative to release the pawl for rapid movement to its operative position, said lever being released from its inoperative position for retum' movement to its operative position under influence of its spring bias a discreet number of degrees of rotation of the disc after the pawl has been moved to its operative position.

Claims

1. A timer including a motor continuously driving a drive disc, a pawl pivotally supported on the disc and urged into driving position, a retracting lever biased to a position in which it engages said pawl and prevents movement of the pawl into driving position while being movable to a position in which the pawl can move to its driving position if not restrained from such movement, a timing cam including ratchet teeth, said pawl being engageable with the ratchet teeth in its driving position, first fixed actuating means positioned to be engaged by said lever as the disc rotates whereby the lever is moved to a position in which it no longer restrains movement of the drive pawl, second actuating means initially engaged by the drive pawl to prevent the drive pawl moving to operating position while the positioning lever is moved to a position in which it does not restrain the drive pawl and then acting to release the drive pawl for movement under its bias into the driving position, said lever being subsequently disengaged from said first actuating means whereby the bias acting on the lever acts to retract the lever and retract the drive pawl from engagement with the ratchet thereby terminating the drive step which was initiated by engagement of the pawl with said ratchet.

2. In a timer drive mechanism for imparting step-by-step movement to a timing cam, a ratchet on the timing cam, a continuously driven drive disc, a pawl pivotally supported on the disc for movement into and out of engagement with the ratchet and movable only in the direction of advance of the adjacent ratchet teeth and the associated timing cam, means normally retracting the pawl to an inoperative position in which it is disengaged from the ratchet, means for cyclically actuating the pawl into operative engagement with the ratchet to advance the timing cam a discreet distance comprising a step of the timing cam, said retracting means being operative at the end of the discreet step to retract the pawl to said inoperative position.

3. A structure according to claim 2 in which said retracting means comprises a lever which is operative to engage the pawl and move the pawl to its inoperative position, spring means biasing the lever to its retracted position, stationary means engageable with the lever as it rotates with the disc to move the lever to an inoperative position in which it is unable to restrain movement of the pawl, spring means acting on the pawl in a direction to engage the pawl with said ratchet, means for restraining movement of the pawl while said lever is being moved to its inoperative position and operative to release the pawl for rapid movement to its operative position, said lever being released from its inoperative position for return movement to its operative position under influence of its spring bias a discreet number of degrees of rotation of the disc after the pawl has been moved to its operative position.