Note: Descriptions are shown in the official language in which they were submitted.
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BAC~ ROIll~ OF ~IE IMVE~TIO~
Generally speaking, the present invention pertains to a drive means
of a timing mechan~sm which comprises ~irst ratchet teeth of a first
major d;ameter 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 inter~ittently rotate the same, and a single one of
said first, second and third ratchet teeth to intermittently rotate same.
LO 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 per;ods so as ta 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 ~iming 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 i5 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 c~mplicated, difficult to fabricate, and
costly to produce.
FEATURES OR OBJECTS OF THE INVENTION
It is, there~ore9 a feature of the present invention to provide
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a timing mPcha3l;snl having a means to delay initiation of the program
provided by the timing mechanismO Qnother 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
mechanisln wherein such means is simple and easy to produce. Another
~eature of the invention is to provide such a timing mechanism which
utilizes cooperating sets of ratchet teeth of different major diameters.
Still another ~eature 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.
DESCRIPTION OF THE DRAWINGS
Figure l is an exploded view of a tlming mechanism employing
the features of the invention.
Figure 2 is a view of a typical ratchet illustrating major and
minor diameters.
Figures 3-5 are similar views illus~rating three modes of operation
of the drive means of the present invention.
Figllre 6 i5 a view of alternate ratchet teeth.
Figures 7A through 7C are plan views showing the relationship
between the alte~nate ratchet teeth and the drive pawls of the
timing mechanism.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to Figure 1, there is shown a timing mechanism lO
which, ;n general, includes a cam means 12 which upon rotation selectively
opens and closes electrical switch means 14 that engages the cam
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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
intecgrally 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 synchr~nous 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 accôrdance 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 clescribed, are well known
in the art and form no part of the present invenion.
The present invention is concerned with the drive portion 18' of
drive means 18 ~Jhich provides a means to delay the operation of electrical
switch means 14 even though electric power has been applied to the
device, Drive means 1~' 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 i5
independently ~otatably earried 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 Figure 2. Referring to Figure 2, a major diameter
B is the distance to the outermost point of the teeth while a minor
ciiameter A is a distance to the base of the teeth. Ratchet teeth 46
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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 c.larity, ratchet teeth 48 are
not shown in Figure 29 bu~ they have a major diameter which is less
than the major diameter of ratchet teeth 44 but greater than the
major diameter o~ ratchet teeth 46. Such teeth relationship is shown
with reference to Figures 3-5.
Returning to Figure 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 ;ts 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 fralne 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 cou1d represent an
hour. The location of the teeth and cam means 12 with respect to a
2ero 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 Figures 3-5~ it be;ng understood that drive pawl 40 and stop pawl 42
are operated through motor drive means 16 and eccentric 38. In Figure
3, drive pawl 40 is engaging the teeth of ratchet 48 only to drive it
alone. Both ratchets 46 and 44 are stationary.
In Figure 4, drive pawl 40 has engaged slot 50 of ratchet 48.
Since, as noted previously3 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 l4. More
specifically, and as previously noted, the number of teeth in ratchet
teeth 46 corresponds to the delay time. Therefore, a portion l5
(Figure l) of the perimeter of cam means 12 that is in line with and
approximtely e~ual to the arc length of ratchet teeth 46 will be free
of coded indicia l3 which control functions of the appliance so that
corresponding switches of switch means l4 cannot be activated.
In Figure 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 l4.
Referring now to Figures 6 and 7A through 7C, another embodiment
of the invention can now be described. This embodiment allows a
variab1e range of time ;ntervals in a single given timer program.
Prior art interval timers have -fixed interval periods throughout
their respect;ve cycles. The variable range of time intervals is
accomplished primarily by providing ratchet teeth 44'3 46' and 48' in
place of the previously described ratchets 44, 46 and 48. As in the
case of the embodiment of Figures l- 5, ratchet teeth 44' and 46' are
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integral with cam means 12, while ratchet teeth 48' are independently
rotatably carried on shaft 22.
Ratchet teeth 44' are the same as ~hose of ratchet teeth 44 of
the embodiment of Figures 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 d;ameter 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 Figures 7A-7C, the operation of the present
embodiment may be described. In Figure 7A, main drive pawl 40 is in
engagement with both ratchet teeth 102 and 104 while secondary drive
pawl 42 ensages teeth 102. Thus both cam means 12 and ratchet teeth
48' are incremently moved. In Figure 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 ;s substantially stationary since
there is only a slight movement oF secondary drive pawl 42. In Figure
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
no~ch 50'.
There is thus provided in the embodiment of Figures 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.
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