Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND 01- THE INYENTION
Generally speaking, the present inventlon relates to a timing
mechanisnl having a clutch means permitting manual rotation of a cam
means independent of a motor drive means, the clutch means comprising a
rotating member fabricated of a material having a first coefficient oF
friction and an aperture therein and a shaft extending through the aperture
and including discs of a materiai of a second material having a different
coefficient of friction cooperating with the rotating member.
The present invention relates to timing mechanisms and more
particularly to a timing mechanism which is neat and compact, and which
utilizes a clutch means which through its individual compactness and
neatness aids in maintaining the overall compactness of the timer.
Timing mechanisms are used in appliances such as washers, dryers,
hair dryers, etc. to sequentially operate the appliance in accordance
~ith a programmed sequence. In such mechanisms, cam programming means
including cams carried by a shaft actuate electrical switches to provide
the program sequence. The cam program means are usually driven through
a motor drive means which usually includes a speed reduction means such
as a gear train. In some instances, the cam programming means can be
manually rotated so that a desired starting point of the program can
be manually set. In such instances, clutching means need to be provided
so that the cam programming means can be rotated independent of the
motor drive.
In applications such as for hair dryers, the timing mechanism
needs to be neat and compact with as little protrusions extending from
the body of the timers as possible.
OBJECTS OR FEATURES OF THE INVENTION
The present invention is concerned with timing mechanisms and has
as one of its objects the provision of a timer which is neat and
-30 compact.
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~ nother object of the inventiol~ is the provision of a timer ~Jhicil
utilizes a c'lutch means so that the cam programming means may be manually
rotated independent of the timer motor drive means.
Still another object of the invention is the provision of a clutch
means which includes a rotating member fabricated of a material having a
first coefficient of friction and an aperture therein and a shaft extending
through the aperture and having clutch discs fabricated of a second
material having a different coefficient of friction.
These and other objects of the invention will become'apparent
from the following description taken in conjunction with the accompanying
drawings.
DESCRIPTION OF THE DRAWINGS
FIGURE 1 is an exploded view of a timing mechanism; and
FIGURE 2 is an enlarged view showing the cooperating elements of
a clutch means used in the timer.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIGURE 1, there is shown a timing device'10
incorporating the novel features-of the present invention. The timer
is composed of two sub-assemblies, the motor assembly 11 and the switch
timing mechanism 12. The motor assembly includes a synchronous motor
9 and an appropriate gear train 8 which includes an output pinion (not shown)
which engages gear 7 to drive the switch timing mechansim 12 through
shaft 13. Gear 7 is independently rotatably carried on shaft 13 through
an aperture 13' in the gear. The housing or cover for the switch timin
mechanism includes a cup shaped member 14 and a cover plate 15 adapted to
close the same. Cover plate 15 is securely fastened to a base plate
of the housing for the gear train assembly through a plurality of
screws 16 which engage internally threaded posts 16' extending through
oblong shaped apertures 17. The cup shaped member 14 and the cover plate
15 are preferably fabricated of an electrically insulating material such
as a phenolic plastic, for example.
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'rhe essential parts of the switch timing mechanisn1, in general,
comprise the switch contact blades 18 and 19 having electrical termin~ls
18' and 19' integrally formed as part or the blades, cam programming
mealls 29, and contact blade retaining means 32 and 32' formed as an
integral part of the cover 15, and cup shaped member 14. Cam programming
means 29 includes at least one cam 29' rotatably carried about shaft 13.
Shaft 13 is journalled in the base of cup shaped member 14 and in cover
plate 15. For illustrative purposes, there is shown a step 30 provided
in the cam, the step being formed in size and contour according to the
desired program. As will be hereinafter described, such programming
means will, with the proper selection of'contact blades 18 and 19, and
blade retaining means 32 and 32', allow various switching circuits to be
readily obtained, the operation of such circuits being controlled by
the timing of the cam programming means 29.
Contact blade 18 is responsive to the cam progamming means through
the wedge shaped cam follower 33, the follower being formed as an
integral part of the blade. Blade 18, being responsive to the cam
programming means, is the actuator blade. Movement of the blade 18
causes electrical contact 34 to engage contact 35. Suitable materials
for the contact include an electrically conductive material such as
copper, for example.
As illustrated in FIGURE 1, the timing device'of the present
invention is adapted to give a single pole, single throw switching circuit
arrangement. Cam programming means 29 forces blade 18 to rise when the
wedge shaped cam follower 33 rides up an'd over the discrete arcuate step
30 thus closing contacts 34 and 35. Because of the contact blade retain-
ing means 32 and 32' the blades readily return to their original position
when cam fol~wer 33 again reaches arcuate step 30. Blade retaining
means 32 includes a stepped blade seating member 36 integrally formed
with and extending from cover 15, notches 37 and 38 formed in cup shaped
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membelA 14, and L-shaped seating mel~ er ~9 integrally formed with and
extending from cup shaped member 1~. E~lade retaining means 32' includes
an L-shaped seat melllber 40 and substantially rectangular shaped
retailling melllber 41 both of which are integrally formed with and extend-
iny from cover 15, and L-shaped seat 42 and notches 43, 44 and 45
formed in cup shaped member 14.
When the various components of the retaining means are placed in
their proper relationship by placing cover 15 over the opening of cup
shaped-member~14, and when contact blades are inserted in slots formed
by the inter-relationship of the parts, the contact blades will be
cantilevered at one end with their other ends being fee to bend in
accordance with the actuation induced by cam programming means 29. When
the arcuate step 30 of the cam programming means again reaches the carn
follower 33, blade 18 will return to the position shown, with blade
19 being stopped at the step 36' of stepped support member 36, thus
breaking the electrical contact between contacts 34 and 35. Contact
blades 18 and 19 preferably include elongated apertures 18" and 19"
which extend beyond the bend of the blades so that the blades can be
more easily deflected for a given thickness of blade.
Shaft 13 can be either motor driven or can be manaully rotated
through a knob 31 so that a desired setting, such as the program starting
point, may be manually set. In order that the manual rotation may be
independent of the motor drive means, a clutch means 50 is provided.
Referring to FIGURE 1 and 2, clutch means 50 includes gear 7 and a
pair of clutch discs 52 and 54. Extending from discs 54 is a pair of
oppositely disposed flanges 56 and 58 which engage corresponding slots
60 and 62 provided in hub 64 of cam programming means 29 to couple the
discs thereto.
As will become apparent hereinafter, the clutching action arises
from the difference in coefficient of friction between gear 7 and discs
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52 and 54. That is, there must be sufficient friction between the gear
and the discs so that the discs will rotate in accordance with the rotation
of the gear when power driven rotation is applied to the gear and yet
permit the discs to be manually rotated independent of the gear. For
the timer iust described, it has been Found that a difference of friction
sufficient to require about 15 inch - oz of torque to override the gear
is satisfactory. In the present embodiment, this has been achieved by
fabricating gear 7 of steel and the discs of a thermoplastic acetal
copolymer plastic, each with a relatively smooth finish. The discs
are insert molded with the gear and as a single piece with shaft 13
and flanges 56 and 58. This assures tight fit between the gear and the
discs.
In operation, when power driven rotation is applied to gear 7, the
Friction between the gear and discs 52 and 54 will cause the discs and
shaft 13 to rotate and cam 29' will be driven through flanges 56 and
58 engaging notches 60 and 62 of the cam. When it is desired to manually
set the cam, shaft 13 is manually rotated to rotate the cam through
flanges 56 and 58 engaging slots 60 and 62 while discs 52 and 54 overcome
the friction between them and gear 7 to override the gear.
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