US3436975A

US3436975A - Sequential timer

Info

Publication number: US3436975A
Application number: US614081A
Authority: US
Inventors: Lee A Woolley
Original assignee: Scott and Fetzer Co
Current assignee: France Scott Fetzer Co
Priority date: 1967-02-06
Filing date: 1967-02-06
Publication date: 1969-04-08
Anticipated expiration: 1986-04-08

Description

April 8, 1969 A. WOQLLEY SEQUENTIAL TIMER Sheet Filed Feb. 6. 1967 INVENTOR.

Lee 4 /%o//ey l. ATTORNEYS April 8, 1969 A. WOOLLEY SEQUENTIAL TIMER Sheet Filed Feb. 6, 1967 R. L ee 4 /Va0//e United States Patent @fice 3,436,975 Patented Apr. 8, 1969 3,436,975 SEQUENTIAL TIMER Lee A. Woolley, Kokomo, Ind., assignor, by mesne assignments, to The Scott 81 Fetzer Company, Lakewood, Ohio, a corporation of Ohio Filed Feb. 6, 1967, Ser. No. 614,081 Int. Cl. F16h 29/04 US. Cl. 74-116 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention deals with a sequential timer wherein the main timing cam is moved at a creep rate in a stepby-step manner.

Prior art It is known to use a mechanism between a timer motor and a main timing cam whereby the motor moves the cam in a step-by-step manner. Such stepping mechanisms are characterized by a considerable amount of mechanical complexity, and the manufacture thereof thus entails a relatively high degree of cost as to labor and parts. In order to obtain good synchronization of actuation of all of the switches which are to be simultaneously actuated under the control of the main timing cam, and in order to provide maximum electrical contact life, the use of stepping mechanisms in such devices has been considered as being commercially indispensable, particularly in the laundry machine field. Creep type of timers have been known which structurally simply involve a stepdown gear train between the motor rotor and the main timing cam. In this type of structure, the main timing cam moves continually, but slowly, and hence its designation as a creeptype of timer. These have a cost advantage, but have been considered as not being commercially acceptable as control devices for laundry machines.

SUMMARY In accordance with the present invention, I have eliminated the conventional complicated stepping mechanism between the output member of the motor and the main timing cam, and have provided in place thereof, only two parts, arranged in the nature of a drive pawl and a stop pawl which moves the main timing cam in a stepby-step manner, wherein the movement is at a creep rate. The two pawls mentioned can be molded, and thus a great simplification is achieved in cost, thus obtaining the mechanical and electrical advantages of a step-by-step mechanism, and the economic advantages of a creeptype of timer.

Accordingly, it is an object of the present invention to provide a sequential timer wherein the motor drives the main timing cam in a step-by-step manner at a creep rate for each step.

A further object of the present invention is to provide a drive mechanism between a timer motor and a main timing cam such that the motor can be mounted on either side of a housing, to thereby adapt a particular timer for installations in positions which otherwise would be precluded by presence of adjacent obstacles.

A further object of the present invention is to provide a drive mechanism between a timer motor and a timing cam which includes only two parts that preferably are molded.

A still further object of the present invention is to provide a sequential timer which is even simpler and hence cheaper than a creep-type of timer.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which preferred structural embodiments incorporating the principles of the present invention is shown by way of illustrative example.

On the drawings:

FIG. 1 is a side view of a sequential timer provided in accordance with the principles of the present invention wherein its motor is mounted on one side thereof;

FIG. 2 is a fragmentary view corresponding to FIG. 1 wherein such motor is mounted on the opposite side thereof;

FIG. 3 is an enlarged fragmentary cross-sectional view taken along III-III of FIG. 1 showing the drive mechanism between the motor and the main timing cam;

FIG. 4 is a view corresponding to FIG. 3 illustrating the position of the components at a different point in a stepping cycle; and

FIG. 5 is a view corresponding to FIG. 4 showing a modified form of this invention.

As shown on the drawings:

The principles of this invention are particularly useful when embodied in a sequential timer of the stepping type, such as is illustrated in FIG. 1, generally indicated by the numeral 10. The timer 10 includes a housing 11 having pairs of oppositely directed

mounting pads

12, 13. Within the housing 11, there is disposed a conventional main timing cam 14 which is rotatably supported and connected to a conventional control shaft 15. The timing cam 14 has a series of circularly arranged teeth 16 on its periphery (FIG. 3), and is disposed centrally in the housing 11 equidistantly between a first motor mounting surface 17 and a second oppositely facing motor mounting surface 18. The timing cam 14 has conventional cam tracks which coact with conventional switches for regulating electric circuits in accordance with a predetermined program, all of which is known and therefore not illustrated.

A motor 19 is secured to a motor mounting plate 20 which comprises mounting means between the motor 19 and the housing 11 by which the motor 19 may be mounted on either side of the housing 11 as shown in FIG. 2, thereby creating a clearance at the selected one of the unused motor mounting positions.

The motor 19 is conventional except that in place of having the conventional output pinion, it includes a rotatable output member 21 which has an eccentric drive portion 22 extending in the nature of a pin on which there is disposed a drive pawl 23. In response to rotation of the rotatable output member 21, the eccentric drive portion 22 moves in a small circle as shown in dashed lines in FIG. 3 to effect both reciprocation and rocking of the drive pawl 23. The drive pawl 23 has a distal end portion 24 which is drivingly engageable with successive teeth 16 to rotate the main timing cam 14 in one direc tion by an angle corresponding to the spacing occupied by each tooth to. The drive pawl 23 has a further portion 25 described further below.

The housing 11 carries a stop pawl 26 which has a distal end or portion which is engageable with successive teeth 16 to preclude rotation of the main timing cam 14 in the reverse or opposite direction.

The mounting means is of such construction that the eccentric drive portion 22 lies substantially in the plane of the teeth 16 so that the motor 19 supports the drive pawl 23 in the same position with respect to the teeth 16 no matter which side of the housing 11 supports the motor 19.

As viewed in FIG. 3 it is preferable that the eccentric drive portion 22 rotate in a clockwise direction. If the motor 19 be mounted on the opposite side of the housing 11, such mounting would have the efiect of reversing the direction of rotation of the eccentric: portion. While reverse rotation still provides an operative structure, the preferred direction of rotation can be restored by selection of a conventional motor 19 which can be selectively operated in a selected direction.

Means are provided to resiliently urge both of the

pawls

23, 26 toward the teeth 16, or toward the periphery of the main timing cam 14. In this embodiment, such means comprise an elongated finger 27 which is integral with the stop pawl 26 which preferably comprises molded plastic, such as of the type sold under the trademark Delrin. The elongated finger 27 extends in the direc tion of the pawl 26 for engagement with the housing at a convenient point, such as at the edge of an aperture 28 in the housing 11 through which the drive pawl 23 extends. Preferably, there is a slight preload on the resilient finger 27 for any position of the eccentric portion 22 whereby a positive biasing force is assured for the stop pawl 26. The finger 27 could engage the housing at some other point, but it is important that the engagement be remote and in addition to that provided by the housing at the point of support. For convenience, the pivotal support of the stop pawl may be provided by integral pin-like projections received in suitable recesses in the housing 11. At least one of the pawls, in this instance the stop pawl 26, has the resilient elongated finger formed integrally therewith at such a point that the finger 27 has an arcuate portion 29 which extends in a direction generally concentric with the pivotal axis of the stop pawl 26.

As shown in FIG. 3, the rotatable output member 21 preferably rotates in a clockwise direction as indicated by the broken arrow, thereby moving the eccentric drive portion 22 in a small circle as mentioned above. As shown in solid lines in FIG. 3, the drive pawl 23 is in its fully retracted position. As the motor rotates, the portion 25 of the drive pawl 23 engages the distal end of the resilient spring finger 27 so as to increase the biasing force on the top pawl 26, and so as to be positively pivoted about the axis of the eccentric drive portion 22 in a counterclockwise direction, thereby to urge the portion 24 positively against the periphery of the adjacent tooth, thereby insuring that the portion 24 drives positively into the bottom end of the gap between teeth. This motion continues until the portion 24 engages the next tooth, and then for about 100 degrees of rotation of the output member 21, the main timing cam 14 is caused to move by a step, such movement continuing until the eccentric drive portion 22 is in its opposite extreme position as shown in broken lines in FIG. 3, thereby placing the drive pawl 23 in its extreme position as also shown in broken lines which determines the limit of movement for that one step. Shortly before that limiting position is reached, the distal end of the stop pawl 26 drops off the tooth on which it is riding, thereby leaving a small gap as shown in FIG. 3 at the end of the driving stroke of the drive pawl, such gap being held dimensionally as small as is practicable.

As soon as the eccentric drive portion 22 rotates further from the position shown in dashed lines in FIG. 3, retraction begins and during such retraction, and again for approximately 80 of advancement, the main timing cam 14 is provided with a stationary dwell. During this retractive movement, the biasing force provided by the spring finger 27 insures that the stop pawl 26 will remain engaged for its intended purpose. Such retractive movement is illustrated in FIG. 4 which shows the drive pawl 23 just an instant before its drive portion 24 drops off the stationary tooth beneath it. Such drop otf occurs before the eccentric portion 22 reaches the position shown in solid lines in FIG. 3, and as the drop off point is reached, the resilient finger 27 pivots the drive pawl 23 into a tooth engaging position and holds it there as explained before.

A typical rotational speed for the output member 21 is one revolution per minute.

The length of the arcuate portion 29 is a factor that controls the spring rate of the resilient finger 27, and by having such arcuate portion, less space is required for a particular spring rate. With the structure of FIG. 4, the spring force applied against the teeth 16 by the drive pawl 23 during retraction decreases, there being no real need for any force under such circumstance, thereby promoting longer life and placing less load on the motor.

FIG. 5 illustrates another advantageous form of practicing the broader aspects of the present invention wherein the motor 19 has been provided with a drive pawl 30 and a stop pawl 31. In this embodiment, both of the

pawls

30, 31 have been provided with means for resiliently urging the pawl against the cam 14, such means comprising

elongated fingers

32, 33 of resilient plastic such as Delrin which are integral with the

respective pawls

30, 31 and which extend in the direction of such pawls and which engage the housing 11 remotely from the point of support. In the instance of the finger 32, the housing thus includes a pin or screw 34 which forms functionally a sta tionary component of the housing 11. FIG. 5 illustrates the components at the end of a stroke, and under this arrangement, there is approximately one-eighth inch deflection at the distal end of the spring finger 32. With the arrangement of FIG. 5, it is not necessary to provide the portion 25 or the portion 35 as shown in FIG. 4, and instead the distal end of the resilient finger 33 continually engages the housing 11 as shown in FIG. 5.

Although various minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon, all such embodiments as reasonbly and properly come within the scope of my contribution to the art.

I claim as my invention:

1. A sequential timer for controlling a number of electric circuits in accordance with a predetermined program, comprising in combination:

(a) ahousing;

(b) a timing cam rotatably supported by said housing and having a series of circularly arranged teeth, said cam being adapted to control the circuits in response to its angular position;

(c) a motor secured to said housing;

(d) a rotatable output member driven by said motor and having a drive portion eccentric to the rotational axis of said output member and disposed in radially spaced relation to said teeth;

(e) a substantially rigid drive pawl having an aperture receiving said eccentric drive portion for being recip rocated thereby into direct driving engagement with a succession of said teeth for incrementally rotating said timing cam in one direction; and

(f) a substantially rigid stop pawl movably supported on said housing in a position to engage said teeth for precluding rotation of said timing cam in an opposite direction.

2. A timer according to claim 1, which includes resilient means integral with said one of said rigid pawls for resiliently urging at least one of said pawls toward said teeth.

3. A timer according to claim 1, which includes resilient means integral with said rigid drive pawl for resiliently urging at least one of said pawls toward said teeth.

4. A timer according to claim 1, which includes resilient means integral with said rigid stop pawl for resiliently urging at least one of said pawls toward said teeth.

5. A timer according to claim 1, which includes resilient means integral with said rigid stop pawl for resiliently urging at least one of said pawls toward said teeth, said rigid drive pawl having a portion engageable remotely from said teeth with said resilient means for urging said rigid drive pawl toward said teeth.

6. A timer according to claim 1 in which said timing cam teeth lie centrally in said housing, and which includes mounting means between said motor and said hous ing which position said eccentric drive portion of said output member substantially in the plane of said timing cam teeth, said mounting means being securable selectably to either one of opposite sides of said housing.

7. A timer according to claim 2, in which said one of said pawls is plastic, and said resilient means comprises an elongated finger extending generally in the direction of said one of said pawls for engagement with said housing remotely from where it is supported.

8. A timer according to claim 2, in which said one of said pawls is plastic, and said resilient means comprises an elongated finger having an arcuate portion integrally joined to said one pawl, said finger being engageable with said housing remotely from said arcuate portion.

9. A timer according to claim 8, in which said one of said pawls is supported pivotably, and said arcuate portion is substantially concentric with the pivotal axis of said one of said pawls.

10. A timer according to claim 1, in which said eccentric drive portion is disposed outside of said housing, said drive pawl extending through an aperture in said housing to engage the teeth of said timing cam within said housing.

References Cited UNITED STATES PATENTS 1,735,923 11/1929 Helgeby 74' 116 2,834,223 5/1958 Strnad 74-417 2,384,110 9/1945 Malmquist 741 16 2,868,026 1/1959 Finehout et a1. 74125 3,104,687 9/1963 Field 143-61 20 FRED c. MATTERN, 1a., Primary Examiner.

W. S. RATLIFF, 111., Assistant Examiner.

U.S. Cl. X.R.