Drive means for a timing mechanism

Rotation of a cam means of a timing mechanism is provided by three sets of axially aligned ratchet teeth having different major and minor diameters and a drive pawl selectively engaging the three sets of teeth. The arrangement provides a means to delay the actuation of switches which control the functions of an appliance. In one embodiment, the relationship between the three sets of ratchet teeth allows a variable range of interval times in a single timer program. That is, the arrangement provides variable dwell times versus cam advance times.

Generally speaking, the present invention pertains to a drive means of a 
timing mechanism which comprises first ratchet teeth of a first major 
diameter coupled to a cam means; second ratchet teeth of a second major 
diameter in working relationship with the first ratchet teeth; third 
ratchet teeth of a third major diameter in working relation with the first 
and second ratchet teeth; and a drive pawl selectively engaging two of the 
first, second and third ratchet teeth at a first predetermined period of 
time to intermittently rotate the same, and a single one of said first, 
second and third ratchet teeth to intermittently rotate same. 
The present invention relates to a timing mechanism and, more particularly, 
to a timing mechanism having a means to delay the operational program of 
the timing mechanism and to provide variable interval time periods so as 
to provide variable dwell (delay) times versus cam advance times. 
Timing mechanisms have been used in the appliance industry for many years 
to control the sequential operation of an appliance such as a washer, 
dryer, dishwasher and of recent years, microwave ovens. In such 
applications, it has sometimes been found necessary to apply electrical 
power to the timing mechanism while at the same time delay the initiation 
of the program provided by the timing mechanism until a desired starting 
time. In addition, depending on the desired programs, it is also highly 
desirable to provide variable interval or delay times between advance 
times. For the most part, the mechanisms used to provide such delay have 
been complicated, difficult to fabricate, and costly to produce. 
FEATURES OR OBJECTS OF THE INVENTION 
It is, therefore, a feature of the present invention to provide a timing 
mechanism having a means to delay initiation of the program provided by 
the timing mechanism. Another feature of the invention is to provide a 
means to provide variable interval or delay times between advance times. 
Another feature of the invention is to provide a timing mechanism wherein 
such means is simple and easy to produce. Another feature of the invention 
is to provide such a timing mechanism which utilizes cooperating sets of 
ratchet teeth of different major diameters. Still another feature of the 
invention is to provide such a timing mechanism wherein a single drive 
pawl selectively engages two of the three sets of ratchet teeth during a 
first predetermined period of time and a single one of the first, second 
and third ratchet teeth during a second predetermined period of time. 
These and other features of the invention will become apparent from the 
following description taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
Referring now to FIG. 1, there is shown a timing mechanism 10 which, in 
general, includes a cam means 12 which upon rotation selectively opens and 
closes electrical switch means 14 that engages the cam means, and a motor 
drive means 16 which applies power driven rotation to the cam means 12 
through drive means 18. Cam means 12 includes a plurality of cams 12' 
having coded indicia 13 thereon and that are integrally formed on a hub 
portion 20 and a shaft 22, shaft 22 being rotatably journalled in base 
plate 24 through aperture 26. Motor drive means 16 is carried on a plate 
28 which is secured to base plate 24. Motor drive means 16 may be of any 
suitable type known in the industry such as a synchronous motor. 
Drive means 18 includes a motor output pinion 30 which extends through 
plate 28 and engages a drive gear 32, the drive gear 32 having a major 
axis defined by hub and shaft 36 which is rotatably journalled in base 
plate 24 through aperture 34. Gear 32 also includes an eccentric 38 which 
is slightly off center of the major axis. A drive pawl 40 and a stop pawl 
or a secondary drive pawl 42 are carried by eccentric 38 to be rotated in 
accordance with the movement of the eccentric. The portion of the drive 
means 18 described thus far, as well as the other elements of the timing 
mechanism previously described, are well known in the art and form no part 
of the present invention. 
The present invention is concerned with the drive portion 18' of drive 
means 18 which provides a means to delay the operation of electrical 
switch means 14 even though electric power has been applied to the device. 
Drive means 18' includes first ratchet teeth 44 which are integral with 
cam means 12, second ratchet teeth 46 which are also integral with cam 
means 12, and third ratchet teeth 48 which is independently rotatably 
carried on shaft 22. Each of the ratchet teeth has a major and minor 
diameter. For the purposes of the present invention the meaning of the 
terms major and minor diameters are illustrated in FIG. 2. Referring to 
FIG. 2, a major diameter B is the distance to the outermost point of the 
teeth while a minor diameter A is a distance to the base of the teeth. 
Ratchet teeth 46 has a major diameter B which is less than the major 
diameter of ratchet teeth 44 and a minor diameter A which is also less 
than the minor diameter of teeth 44. For the sake of clarity, ratchet 
teeth 48 are not shown in FIG. 2, but they have a major diameter which is 
less than the major diameter of ratchet teeth 44 but greater than the 
major diameter of ratchet teeth 46. Such teeth relationship is shown with 
reference to FIGS. 3-5. 
Returning to FIG. 1, and as will be hereinafter explained, drive pawl 40 
selectively engages ratchet teeth 48 and ratchet teeth 46 during a 
predetermined period of time and further engages only ratchet teeth 44 
during another period of time. Ratchet 48 includes a notch 50 that is of 
sufficient depth to provide a minor diameter at least as small as the 
minor diameter of ratchet teeth 46. Stop pawl or secondary drive pawl 42 
engages ratchet teeth 44 to prevent backlash of cam means 12 during its 
intermittent rotation while slider 52, which is slidably carried in slot 
54 of base member 24, engages ratchet teeth 48 to prevent its backlash. 
Pawls 40 and 42 are spring biased through coil springs 40' and 42' to 
insure engagement of the pawls with ratchet teeth 44 while slider 52 is 
spring biased through spring 52' (which engages another frame member of 
the timing mechanism, not shown) to insure engagement of the slider with 
ratchet teeth 48 all in a manner well known in the art. 
The number of teeth of ratchet teeth 46 corresponds to the amount of delay 
time desired. For example, each tooth could represent an hour. The 
location of the teeth and cam means 12 with respect to a zero start time 
as to the number of delay hours desired can then be manually set by 
manually rotating an extension of shaft 22 (not shown) through a clutch in 
a manner well known in the art. 
The operation of drive means 18' can now be described with reference to 
FIGS. 3-5, it being understood that drive pawl 40 and stop pawl 42 are 
operated through motor drive means 16 and eccentric 38. In FIG. 3, drive 
pawl 40 is engaging the teeth of ratchet 48 only to drive it alone. Both 
ratchets 46 and 44 are stationary. 
In FIG. 4, drive pawl 40 has engaged slot 50 of ratchet 48. Since, as noted 
previously, the depth of knotch 50 is of sufficient depth to provide a 
minor diameter at least as small as the minor diameter of ratchet 46, 
drive pawl 40 will also engage ratchet 46. Since, in the present 
embodiment, both ratchet teeth 44 and 46 are integral with cam means 12, 
the cam means will advance one step in accordance with the teeth of 
ratchet teeth 46. However, it should be understood that during this time, 
cam means 12 will not be in a position to activate any of the switches of 
electrical switch means 14. More specifically, and as previously noted, 
the number of teeth in ratchet teeth 46 corresponds to the delay time. 
Therefore, a portion 15 (FIG. 1) of the perimeter of cam means 12 that is 
in line with and approximtely equal to the arc length of ratchet teeth 46 
will be free of coded indicia 13 which control functions of the appliance 
so that corresponding switches of switch means 14 cannot be activated. 
In FIG. 5, drive pawl 40 has passed through ratchet teeth 46 and now 
engages ratchet teeth 44 for continued intermittent rotation of cam means 
12 to start the normal program of the timing mechanism and activate 
electrical switch means 14. 
Referring now to FIGS. 6 and 7A through 7C, another embodiment of the 
invention can now be described. This embodiment allows a variable range of 
time intervals in a single given timer program. Prior art interval timers 
have fixed interval periods throughout their respective cycles. The 
variable range of time intervals is accomplished primarily by providing 
ratchet teeth 44', 46' and 48' in place of the previously described 
ratchets 44, 46 and 48. As in the case of the embodiment of FIGS. 1-5, 
ratchet teeth 44' and 46' are integral with cam means 12, while ratchet 
teeth 48' are independently rotatably carried on shaft 22. 
Ratchet teeth 44' are the same as those of ratchet teeth 44 of the 
embodiment of FIGS. 1-5. Ratchet teeth 46' have a major diameter E which 
is less than the major diameter F of ratchet teeth 44' while teeth 102 
have the same major diameter as teeth 44' and are integral therewith. 
Ratchet teeth 48' has a major diameter which is the same as major diameter 
F of teeth 102 and 44'. As shown, there is a plurality of notches 50' 
which have a minor diameter G which is at least as small as a minor 
diameter of ratchet 46'. 
It is to be understood that the number of teeth in any one ratchet and the 
spacing between the teeth is dependent upon the particular program 
including the amount of interval time desired. 
Referring now to FIGS. 7A-7C, the operation of the present embodiment may 
be described. In FIG. 7A, main drive pawl 40 is in engagement with both 
ratchet teeth 102 and 104 while secondary drive pawl 42 engages teeth 102. 
Thus both cam means 12 and ratchet teeth 48' are incremently moved. In 
FIG. 7B main drive pawl 40 is engaging ratchet teeth 104 only while 
secondary drive pawl 42 engages teeth 102. In this mode, cam means 12 is 
substantially stationary since there is only a slight movement of 
secondary drive pawl 42. In FIG. 7C drive pawl 40 has engaged one of the 
notches 50' of ratchet 48' to engage teeth 46' while secondary drive pawl 
42 continues to engage teeth 102. In this mode, cam means 12 advances for 
one interval of notch 50'. 
There is thus provided in the embodiment of FIGS. 6 through 7C a means of 
varying the time between advances of cam means 12, the time intervals 
being programmed by selection of the spacing of notches 50', major 
diameter ratchet teeth spacing and intervals between the strokes of pawls 
40 and 42.