U.S. patent number 3,751,939 [Application Number 05/302,743] was granted by the patent office on 1973-08-14 for weigh bar switch arrangement for automatic ice maker.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to James A. Bright.
United States Patent |
3,751,939 |
Bright |
August 14, 1973 |
WEIGH BAR SWITCH ARRANGEMENT FOR AUTOMATIC ICE MAKER
Abstract
A weigh switch to stop production of an automatic ice maker
whenever the ice collecting bin is either filled with ice pieces or
removed from its carrier means. An electrically conductive bin
weigh bar is pivoted on a terminal post to provide a first lever
arm loaded by the carrier means and a second counterbalancing lever
arm which pivots the bin weigh bar from a first open circuit
position to a second ice maker energizing position electrically
contacting an overlying conductive pivoted ice weigh bar when the
bin is inserted in the carrier means and the combined weight of the
bin and its contents is below a predetermined amount. In response
to the weight of a filled bin, the bin and ice weigh bars are
pivoted in unison to a third open circuit position thereby
terminating the production of ice pieces.
Inventors: |
Bright; James A. (Dayton,
OH) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
23169024 |
Appl.
No.: |
05/302,743 |
Filed: |
November 1, 1972 |
Current U.S.
Class: |
62/137;
222/58 |
Current CPC
Class: |
F25C
1/24 (20130101); F25C 2305/022 (20130101) |
Current International
Class: |
F25C
1/22 (20060101); F25C 1/24 (20060101); F25c
005/18 () |
Field of
Search: |
;62/137,344 ;222/58 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3540227 |
November 1970 |
Eyman, Jr. et al. |
3601145 |
August 1971 |
Eyman, Jr. |
|
Primary Examiner: Wayner; William E.
Claims
I claim:
1. An automatic ice maker including a support frame, a mold
pivotally supported thereon, means for supplying liquid to said
mold, means for freezing the liquid in said mold, a drive motor, a
circuit for controlling said drive motor, means operated by said
drive motor for ejecting frozen ice pieces from said mold, a
collecting bin, carrier means pivotally supported on said frame
adapted to removably support said bin in a position for collecting
the ice pieces ejected from said mold wherein the improvement
comprises, a weigh switch in said control circuit, said weigh
switch including an electrically conducting bin weigh bar pivotally
supported intermediate its ends on an electrical terminal post,
said bin weigh bar having a first relatively short lever arm at one
side of said terminal post and a second relatively long bin
counterbalancing lever arm at the opposite side of said terminal
post, a weigh rod connected to the free end of said first lever arm
and extending downwardly therefrom, said weigh rod having its lower
end connected to said carrier means, said bin weigh bar being
unbalanced such that said second lever arm tends to gravitate into
contact with lower stop means supporting said bin weigh bar in a
first substantially horizontally disposed weigh opening position
when said bin is removed from said carrier means, an electrically
conducting ice weigh bar pivotally supported adjacent its one end
in spaced overlying relation to said bin weigh bar, said ice weigh
bar pivotal support positioned outboard of said second lever arm's
free end, said ice weigh bar being unbalanced such that its free
end tends to gravitate into electrical contact with terminal stop
means, said bin upon being inserted in said carrier means operative
by means of exerting a weight on said first lever arm for pivoting
said second lever arm from its first open circuit position to a
second weigh switch closed position electrically contacting said
ice weigh bar, the weight of said ice weigh bar operative to
maintain said second closed circuit position of said weigh bars
until a predetermined number of mold ice piece harvests have been
received in said bin, said bin weigh bar and said ice weigh bar
being responsive to the weight of a final ice piece harvest to
pivot said bars in unison to a third weigh switch open position,
whereby said ice weigh bar is moved out of electrical contact with
said electrical terminal stop means and into engagement with upper
stop means such that said drive motor is deenergized to thereby
stop operation of said ice maker until a sufficient quantity of ice
pieces have been removed from said bin.
2. An automatic ice maker including a support frame, a mold
pivotally supported thereon, means for supplying liquid to said
mold, means for freezing the liquid in said mold, a drive motor, a
circuit for controlling said drive motor, means operated by said
drive motor for ejecting frozen liquid from said mold, a collecting
bin, a carrier adapted to removably support said bin in a position
within the path of movement of the frozen liquid discharged by said
ice maker, means on said frame pivotally supporting said carrier
for movement about a substantially horizontal axis wherein the
improvement comprises, a weigh switch in said control circuit, said
weigh switch including an electrically conducting bin weigh bar
pivotally supported intermediate its ends on an electrical terminal
post, said bin weigh bar having a first relatively short lever arm
at one side of said terminal post and a second relatively long bin
counterbalancing lever arm at the opposite side of said terminal
post, said short lever arm having a knife-edge at its free end, a
weigh rod supported on said knife-edge at its upper end and
extending downwardly into supporting engagement with said carrier,
lower stop means supporting said second lever arm in a first
substantially horizontally disposed open circuit position when said
bin is removed from said carrier, an electrically conducting ice
weigh bar pivotally supported adjacent its one end in spaced
overlying relation to said bin weigh bar for movement in a common
vertical plane with said bin weigh bar, said ice weigh bar pivotal
support positioned outboard of said second lever arm's free end,
terminal stop means supporting in electrical conducting fashion the
free end of said ice weigh bar in spaced substantially parallel
relation to said bin weigh bar, said bin upon being inserted in
said carrier operative by means of exerting a downward force on
said knife-edge for pivoting said second counterbalancing lever arm
from its first open circuit position to a second closed circuit
position electrically contacting said ice weigh bar, the weight of
said ice weigh bar operative to maintain said second closed circuit
contacting position of said weigh bars until a predetermined number
of mold frozen liquid harvests have been received in said bin, said
bin weigh bar and said ice weigh bar being responsive to the weight
of a final frozen liquid harvest to pivot said bars in unison to a
third open circuit position, whereby said ice weigh bar is moved
out of electrical contact with said electrical terminal stop means
and into engagement with upper stop means to deenergize said drive
motor and thereby stop operation of said ice maker until a
sufficient quantity of frozen liquid has been removed from said
bin.
3. An automatic ice maker including a support frame, a mold
pivotally supported thereon, means for supplying liquid to said
mold, means for freezing the liquid in said mold, a drive motor, a
circuit for controlling said drive motor, means operated by said
drive motor for ejecting frozen liquid from said mold, a collecting
bin, a carrier adapted to removably support said bin in a position
within the path of movement of the frozen liquid discharged by said
ice maker, said carrier pivotally supported on said frame for
movement about a substantially horizontal axis, said carrier being
unbalanced with its forward end tending to gravitate in a downward
direction, wherein the improvement comprises, a weigh switch in
said control circuit, said weigh switch including an electrically
conducting bin weigh bar supported intermediate its ends on an
electrical terminal post for pivotal movement in a vertical plane,
said bin weigh bar having a first relatively short lever arm at one
side of said terminal post and a second relatively long lever arm
at the opposite side of said terminal post, said bin weigh bar
being unbalanced such that said second lever arm tends to gravitate
in a first direction, said short lever arm having an upwardly and
outwardly tapered knife-edge at its free end, a weigh rod having a
notched portion on its upper end forming a horizontally disposed
upper undercut surface supported on said knife-edge, said weigh rod
extending downwardly into supporting engagement with the forward
end of said carrier, lower stop means supporting said bin weigh bar
second lever arm in a first substantially horizontally disposed
open circuit position when said bin is removed from said carrier,
an electrically conducting ice weigh bar pivotally supported
adjacent its one end in spaced overlying relation to said bin weigh
bar for movement in the vertical plane of said bin weigh bar, said
ice weigh bar pivotal support positioned outboard of said second
lever arm's free end such that said ice weigh bar tends to
gravitate in a second direction, terminal stop means positioned
outboard of said knife-edge supporting in electrical conducting
fashion the free end of said ice weigh bar in spaced substantially
parallel relation with said bin weigh bar, said bin upon being
inserted in said carrier operative by means of exerting a weight on
said knife-edge for pivoting said second counterbalancing lever arm
in said second direction from its first open circuit position to a
second closed circuit position electrically contacting said ice
weigh bar, the weight of said ice weigh bar operative to maintain
said second closed circuit contacting position of said weigh bars
until a predetermined number of mold frozen liquid harvests have
been received in said bin, said bin weigh bar and said ice weigh
bar being responsive to the weight of a final frozen liquid harvest
being discharged into said bin to pivot said bars in unison to a
third open circuit position, whereby said ice weigh bar is moved
out of electrical contact with said electrical terminal stop means
and into engagement with upper stop means to deenergize said drive
motor and thereby stop operation of said ice maker until a
sufficient quantity of frozen liquid has been removed from said
bin.
4. The automatic ice maker as claimed in claim 1 wherein the
effective length of said relatively long lever arm is of the order
of fifteen times the effective length of said relatively short
lever arm.
Description
This invention relates to automatic ice makers for domestic
refrigerators and in particular to a counterbalanced weigh bar
electric switching system for automatically stopping the production
of ice pieces whenever the collecting bin is either filled with ice
pieces to a preselected load or the bin is dislodged from the ice
maker.
In one form of improved automatic ice maker disclosed in the Eyman,
Jr., et al. U. S. Pat. No. 3,540,227, owned by the assignee of the
instant invention, a mold is provided with an ejecting means for
transferring formed ice pieces to a subjacent collecting bin. In
the Eyman patent a commutator timing gear is provided together with
a mold temperature sensing thermostat which have cooperating spring
contacts for controlling the filling, freezing and ejecting cycles
of the ice maker. One of the commutator contacts is actuated by a
pivotal ice collecting bin supporting carrier by means of a
cooperating weak and strong coil springs arrangement stopping the
production of ice pieces whenever the bin is disloged or removed
from its inserted position or when the bin is loaded with ice
pieces to a preselected weight. Such an arrangement requires the
individual calibration of each ice maker because of the inherent
variability of coil springs, thus materially increasing the cost of
manufacture of each ice maker unit.
It is an object of the present invention to provide an automatic
ice maker having an improved means for sensing the load condition
of an ice piece collecting bin pivotally supported from a first
lever arm of an electrically conductive pivoted bin weigh bar by
knife edge means wherein the bin weigh bar is rotated about its
fulcrummed support to a first open circuit position by a
counterbalancing second lever arm when the bin is dislodged from
the ice maker, and wherein the bin weigh bar is rotated to a second
circuit closing position with the second lever arm in electrical
contact with an overlying ice weigh bar under the load of a
positioned empty or partially filled ice collecting bin and wherein
the second lever arm pivots the ice weigh bar in unison therewith
to a third open circuit position in response to the weight of a
predetermined load of ice pieces in the bin thus automatically
stopping the operation of the ice maker.
Further objects and advantages of the present invention will be
apparent from the following description, reference being had to the
accompanying drawings, wherein a preferred embodiment of the
present invention is clearly shown.
In the drawings:
FIG. 1 is an irregular vertical sectional view through a
refrigerator embodying an air cooled automatic ice maker
illustrating the invention;
FIG. 2 is an enlarged fragmentary vertical sectional view of the
ice maker of FIG. 1 showing the drive and control mechanism;
FIG. 3 is a sectional view taken along line 3--3 of FIG. 1;
FIG. 4 is an enlarged partial horizontal sectional view taken along
line 4--4 of FIG. 1;
FIG. 5 is a fragmentary vertical elevational view partly in section
taken along line 5--5 of FIG. 3;
FIG. 6 is a view of the balance beam weigh bar showing dimensional
ratio of its lever arms;
FIG. 7 is a schematic wiring diagram.
Referring now to the drawings and more particularly to FIG. 1,
there is shown the upper portion of a frost-free type of household
refrigerator 20 with an upper below-freezing compartment 22
enclosed by an insulated door 24 and a lower above-freezing
compartment 26 enclosed by a lower insulated door 28. These
compartments are surrounded by the insulated side, top, bottom and
rear walls 30 separated by horizontal insulated wall 32 containing
an evaporator compartment 34 provided with finned evaporator 36
having vertical fins extending from the front to the rear of the
compartment 34. Evaporator compartment 34 is provided with an inlet
38 at the front communicating with the front of the below-freezing
compartment 22 and additional inlets (not shown) communicating with
the top of the above-freezing compartment 26. At the rear, the
compartment 34 connects with a shroud 40 communicating with the
entrance of a centrifugal fan 42 which is driven by an electric
motor 44 housed in a rear wall 30 of the cabinet. The cooling
arrangement for the compartments may be similar to that shown in
U.S. Pat. No. 3,359,750 issued Dec. 26, 1967, or U.S. Pat. No.
3,310,957 issued Mar. 28, 1967, owned by the asignee of the present
application and which may be referred to for further details of
construction of the refrigerator.
The fan 42 is provided with an upwardly extending discharge duct 46
having a distributor 48 at the top which distributes the discharge
of air through the below-freezing compartment 22. Evaporator 36 is
maintained at suitable below-freezing temperatures such as
-5.degree. to -15.degree. F. to maintain the compartment 22 at the
temperature of 0.degree. F. or below.
For providing special cooling for the automatic freezer the
distributor 48 is provided with a laterally extending discharge
duct 50 extending along the intersection of the rear and top walls.
Behind automatic ice maker 52 the laterally extending duct 50 is
provided with wide discharge nozzle 54 which discharges the cold
air directly onto the top of the ice maker 52 and particularly onto
the top of its ice piece forming mold 56.
As seen in FIGS. 1 and 2 the mold 56 is provided with two rows of
pockets 58 containing four pockets in each row and has an upwardly
flanged rim 60 extending around the short and long sides thereof.
The mold 56 of the ice maker is supplied with water or any other
liquid to be frozen from a pressure water system or other liquid
under pressure to a solenoid control valve 62 which controls the
flow of water through pipe 64 extending through the insulation of
the top wall to a suitable discharge device 66 in the top wall of
the below-freezing compartment 22 above the front pockets 58 of the
mold 56. The ice maker 52 is provided with a wide U-shaped frame 68
which surrounds the mold 56 and is fastened to the adjacent side
wall of the freezing compartment 22 by suitable screws. Below the
frame 68 is a rectangular bin carrier 70 having, adjacent the rear,
a pair of upwardly extending projections 72 positioned respectively
adjacent the inner surfaces of the frame side walls and having
outwardly directed pivot pins 74 extending through aligned
apertures in the side walls such that the carrier 70 is pivoted
about a horizontal axis. By virtue of this arrangement the weight
of the bin and carrier biases the forward end of the carrier in a
downward direction about the pivotal axis of pins 74.
As a result it will be appreciated that the rear portion of the
carrier 70 together with an inserted bin 78 is supported by the
pivotal pins 74 for movement about a substantially horizontal axis
that is displaced rearwardly from the center of gravity of the
carrier and bin while the forward portion of the carrier and bin is
supported by suspension means in the form of a weigh shaft or rod
243 displaced forwardly from the center of gravity of the carrier
and bin. In the disclosed form of the invention the axis of the
support pins 74 is located approximately one and three-quarters
inches closer to the center of gravity of the combined carrier and
bin than the vertical axis of weigh rod 243. Thus, for example, if
the combined weight of the bin and carrier is about 1.80 pounds the
weight will be distributed so that a downward pull or force of
about 0.70 pounds will be applied to the weigh rod 243 and a
slightly larger force of about 1.10 pounds will be applied to the
pivotal pins 74. By virtue of this arrangement the carrier and
fully inserted bin create an unbalance or moment such that the
front end of the carrier tends always to gravitate or pivot in a
downward direction about the axis of pins 74.
In the disclosed form of the invention the mold delivers eight ice
pieces into the bin, having a total weight of about one-third
pound, during each harvest of the ice maker. Consequently, the bin
load on weigh rod 243 is proportionally increased in stepped
increments. A weigh bar electrical switch arrangement to be
described is designed to sense a percentage of the total weight of
the carrier and filled bin applied thereto by means of the downward
pull on weigh rod 243 proportional to a predetermined number of ice
harvesting cycles. In a manner to be explained the final harvest of
ice pieces discharged into the bin 78 creates a cumulative load
which overshoots the neutral balance condition of the weigh switch
by a predetermined amount to produce a triggering downward pull on
weigh rod 243 to insure that the automatic ice maker control
circuit is immediately opened.
It will be noted that the bin carrier 70 is provided with
supporting ledges 76 on its inner sides for slidably supporting the
laterally extending flanges 80 of the box-shaped bin 78 while the
bin 78 is provided with a double flange 82 at the front to serve as
a handle.
A description of the ejection and control systems of the ice maker
is unnecessary herein since they are described in the
above-mentioned U.S. Pat. No. 3,540,227, the disclosure of which is
incorporated herein by reference.
For accessibility all the mechanism and controls are located at the
front of the freezer with the tray rotating and twisting mechansim
disclosed in U.S. Pat. No. 3,540,227, and the control system being
located in the housing 127 while an electric driving motor 129 and
the wiring are located on the front face of wall or mounting plate
133. The housing 127 and plate 133 are preferably formed from
suitable plastic material. Substantially the entire operating and
control mechanism are mounted upon the irregular plastic upright
plate 133 which closes the housing 127 to form compartment 135. The
front face of plate 133 supports the drive motor 129 having its
final drive shaft extending through the dividing wall or electrical
control plate 133 and provided with a drive pinion 139 on the
opposite side which continuously meshes with a large driven gear
141. The large gear 141 has an apertured hub 191 (FIG. 5) rotatably
mounted in a removable manner by a suitable snap retainer 192 on
the inner shaft end of hexgon collar bolt 143. The outer threaded
end of bolt 143 extends through opening 144 in boss 145 on wall 133
and is fixedly secured thereto by lock nut 147 and its collar
148.
The large gear 141 is recessed to receive and hold in position the
thin brass nickel plated commutator 193 which is shown bonded to
the face of the gear 141 nearest the wall 133. As seen in FIG. 3
the commutator 193 includes a fill projection or segment 195
cooperating with a spring contact and terminal member 197 to
measure the fill period by the time period required for the fill
projection or segment 195 to move past the upper end of the spring
contact 197. The commutator 193 also includes a delay projection or
segment 199 which cooperates with the delay or stop switch arm 221
having a ball type spring contact end which normally engages the
delay and fill segments 199 and 195 of the commutator 193 and
during the remainder of the time contacts the plastic surface of
the gear 141. The stop switch arm 221 is in electrical continuity
with threaded terminal post B which is in turn electrically
connected to terminal "I" of thermostatic relay 283 via lead
222.
As seen in FIG. 4 the weigh rod 243 is vertically slidably mounted
through the aperture 249 in the bottom of the upright dividing wall
133 and projects through the bottom thereof and through a slot 245
in the front cross member 248 of the bin carrier 70. The bottom of
the weigh rod 243 is provided with a C-shaped disc retainer 247
which is keyed thereto and which supports the front cross member
248 of the bin carrier 70.
The weigh rod 243 has an enlarged cylindrical upper head portion
250 integrally molded on the upper end thereof formed with a
transversely extending notched portion 251 having horizontally
disposed opposed upper and lower surfaces in vertically spaced
dimension to receive therein the relatively short lever arm 252 of
an electrically conducting balance beam or bin weigh bar 254
fulcrummed on wall 133 by pivot terminal post A below pivoted ice
weigh bar 256. The bin weigh bar 254 which is in electrical
continuity with terminal post "A" is pivoted in a vertical plane to
extend perpendicular to the axis of the post "A" such that the bin
weigh bar 254 is counterbalanced to its horizontal position.
As best seen in FIG. 6 the bin weigh bar is shown diagrammatically
in its counterbalanced horizontal position such that its relatively
short lever arm 252, formed with an upwardly and outwardly tapered
surface knife edge contact 255, designed to engage with a planar
metal surface provided by a U-shaped clip 258 which may be snapped
into the weigh rod notch 251. The weigh bar 254 has a relatively
long lever arm 260 functioning as a counterbalance whereby the beam
254 is unbalanced and tends to gravitate the long lever arm in a
clockwise direction to a first generally horizontal open circuit
position in engagement with a first stop boss 262. The distance
L.sub.1 shown in FIG. 6, between the upper marginal edge 257 of the
lever arm 260 and the fulcrummed pivot post "A" is of the order of
15 times the relatively short lever arm 252 distance X.sub.1
between the knife-edge 255 and pivot post "A." Thus, in the
disclosed form the weigh bar 254 develops a ratio of about 15:1 for
transmitting the weight of the inserted bin vertically therethrough
so as to be multiplied thereby. For example, in the present
embodiment the distance L.sub.1 is of the order of 1.875 inches and
the distance X.sub.1 is of the order of 0.125 inches.
An elongated electrically conductive ice weigh bar 256 is pivoted
on pivot pin 263 whose threaded end as seen in FIG. 5 is secured by
nuts 264 to wall 133. The pivot pin 263 of the ice weigh bar 256 is
positioned outboard of the bin weigh bar contact edge 257 and
extends lengthwise in a direction opposite to the direction of the
relatively long lever arm 260.
The ice weigh bar 256 is of a length such that its free end 265
extends outboard of the knife edge 255 a sufficient distance such
that the ice weigh bar 256 tends to gravitate in a downward
counterclockwise direction (FIG. 6) toward a horizontal closed
circuit position spaced above and generally parallel to the first
or counterbalanced open circuit position of the underlying bin
weigh bar 254. In its closed circuit position the ice weigh bar
free end 265 is supported on a fixed electrical contact in the form
of threaded terminal post H having a pair of securing contact nuts
267 and 268 thereon between which spring switch arm 225 is retained
in electrical continuity with post H.
In operation the bin weigh bar 254 is designed so that with the bin
78 outwardly displaced or removed from the freezer the bar 254 is
in its generally horizontal dashed-line first open circuit position
(FIG. 3) engaging first stop boss 262 such that its marginal edge
257 of long lever arm 260 is spaced in parallel fashion from the
underside of the generally horizontal ice weigh bar 256. When the
bin 78 is fully inserted in carrier 70 the short lever arm 252 is
rotated slightly in a counterclockwise direction from its
overbalanced position (as viewed in FIG. 4) and the downward
pivoting force on lever arm 252 will effect an upward pivotal
movement of lever arm 260 a proportionately greater distance to a
second closed circuit position operative to provide an electrical
path between marginal edge 257 and the underside of the ice weigh
bar 256 and as a result electrical continuity is established
between post A, fixed contact post H and spring switch contact arm
225 having a rounded-nose contact 270 in continuous contact with
the commutator 193.
The circuit for the ice maker, partially shown in the FIG. 7
schematic, is carried on the mounting plate 133 covering the
housing 127. After the mold has been filled with water the
thermostatic switch 283 has a movable contact 302 which closes to
its fixed terminal contact "I" on a rising predetermined
temperature, sensed by tube 285 at temperatures of about 19.degree.
F .+-. 1.degree. F., which means that there is no continuity via
line 284 from thermostat terminal contact "III" to post A through
the weigh switch assembly, to post H, arm 225, commutator 193, arm
279 of post D connected to power line 290 via fixed spring contact
arm 225 and commutator 193 rendering the motor circuit incomplete.
The ice bin 78 is empty and in position in the carrier 70. When the
ice pieces are frozen and the sensing tube 285 temperature drops to
a predetermined temperature, which in the disclosed form is about
16.degree. F. .+-. 1.degree.F., the thermostat movable contact 302
closes to fixed terminal contact "III" completing a circuit to post
A, through the weigh switch bars, terminal post H and fixed spring
contact 225, to post D connected to power line 290 completing a
circuit to the motor 129 and the other side of the line 291. This
begins the harvest cycle. As commutator 193 is attached to the
large gear 141, which is driven directly off of the motor pinion
gear 139, whenever the unidirectional motor 129 runs, the
commutator 193 must also rotate in a clockwise direction as viewed
in FIG. 3.
As the commutator continues to advance until the holding switch 267
connected to terminal post C is closed by moving past notch 269
which completes the motor 129 circuit directly to the commutator
193. It is at this point that the mold 56 begins its first
clockwise twist and the circuit cannot be interrupted by the weigh
switch bars until the first twist has been completed and the tray
has been returned to a normal horizontal position and on past to a
position just before the ice pieces fall from the mold 78.
Before the holding switch 267 opens the delay switch 221 will
close. When the holding switch 267 has opened the only way the
motor 129 can be energized to complete the ice making cycle is for
the thermostat sensing tube 285 to warm up to the predetermined
19.degree. F. temperature causing movable contact 302 to close to
terminal contact "I." The holding switch 267 opens when the mold
has been rotated through approximately a 45.degree. angle, with the
notch 271 beneath the adjacent end of the spring contact 267 to
stop the ice maker at a desirable time and not when the mold is
under a twist.
Terminal F of the fill switch 197 is closed when its end engages
fill projection 195, completing the circuit from the commutator 193
to the solenoid 306 (FIG. 7) of the fill valve 62. The holding
switch 267 of post C is closed via line 289 from terminal II to
prevent interruption of the motor circuit during the "Fill"
interval which is about a 12 second period.
A positive temperature coefficient thermistor heater 307 is
positioned adjacent the bellows 284 of the thermostatic switch 283
and provides a small amount of heat to insure the operating
temperatures of the thermostat are controlled by the temperature of
the thermostat sensing tube or bulb 285 rather than being
controlled by the temperature of the casing of the bellows 284. The
heater 307 is connected by line 294 to spring contact 279 of line
post D continuously closed to the commutator 193 and line 295 to
line post E.
Reference is now made to FIG. 6 which diagrammatically illustrates
the weigh bar assembly system which comprises the bin weigh bar 254
supported on the fixed pivot pin A for pivotal movement or
displacement in response to the ice storage bin forces acting on
the bar 254. In the disclosed form the forces include the variable
force f.sub.1 which includes the force of the bin carrier 70
(F.sub.c) and the force of an empty or partially full ice
collecting bin 78 (F.sub.b) while the force of the carrier and a
full bin of ice pieces if F.sub.t. With the relationships states
the following force conditions exist.
1. For f.sub.1 < F.sub.c + F.sub.b no electrical continuity
between A and H.
2. for F.sub.c + F.sub.b .ltoreq. f.sub.1 < F.sub.t electrical
continuity exists between A and H.
3. for f.sub.1 .gtoreq. F.sub.t no electrical continuity exists
between A and H.
Relationship (1) demonstrates that when the bin 78 is removed from
the carrier 70 the weight of the carrier alone producing variable
force f.sub.1 is insufficient to pivot bin weigh bar 254 in a
counterclockwise direction (as viewed in FIG. 6) from its
horizontal overbalanced position engaging stop boss 262. In the
disclosed form the effective counterclockwise moment acting on the
bin weigh bar 254 because of the variable force f.sub.1 is exerted
at knife edge 255 on the relatively short first lever arm 252,
whose length X.sub.1 is of the order of 0.125 inches.
The weight W.sub.1 of the bin weigh bar 254 acts as a counterweight
through its center of gravity (c.g.) with an effective moment arm
Y.sub.1 of about 1.051 inches to create a total effective clockwise
unbalanced moment on the bin weigh bar 254 in opposition to the
counterclockwise moment created by the bin carrier 70 with the bin
78 removed to prevent pivotal movement of the bin weigh bar 254
from its horizontal static equilibrium position engaging limit stop
262.
Relationship (2) demonstrates that when the bin 78 is inserted in
the carrier 70 the variable force f.sub.1 is equal to or greater
than a predetermined load, which is about 0.7 pounds in the form
shown, and will create a moment sufficient to overcome the constant
load W.sub.1 to pivot the bin weigh bar 254 in a counterclockwise
direction causing edge 257 to come to a second static position in
contact with the underside of beam lever 256 and establish
electrical continuity between terminals A and H. In this statically
balanced or neutral position, shown in solid lines FIG. 3, the bin
weigh bar 254 and ice weigh bar 256 act as a compound weigh bar
lever system with variable equal and opposite force f.sub.2 being
exerted on the bin weigh bar 254 through a moment arm L.sub.1 and
the ice weigh bar 256 through moment arm X.sub.2.
The relationship (3) demonstrates that when the total moment
produced on the bin weigh bar 254 by two variable forces f.sub.1
and f.sub.2 acting on the bin weigh bar 254 on opposite sides of
its fulcrum pivot and in opposite directions about the fulcrum
pivot A do not cause the bin and ice weigh bars to pivot from their
neutral position of FIG. 3 until the moment of the constant loads
W.sub.1 and W.sub.2 is overcome by the moments of the variable
forces f.sub.1 and f.sub.2 acting through their lever arms X.sub.1
and X.sub.2 respectively. This occurs when the variable force
f.sub.1 equals or exceeds a predetermined balanced load, which for
the form shown is about 4.20 pounds, or the equivalent of nineteen
harvests of ice-pieces wherein each harvest weighs about one-third
of a pound. Thus within the range of about 0.70 pounds to 4.20
pounds the weigh bars maintain a condition of balance and thereby
maintain the weigh switch in an electrically closed state. As
successive harvests of ice pieces are deposited in the bin the
variable force f.sub.1 increases in stepped increments and is
designed such that the eighteenth harvest creates a force f.sub.1
of about 4.10 pounds or a load just below the critical unbalancing
weight of 4.20 pounds with the result that the nineteenth harvest
creates a force of about 4.25 pounds on the weigh rod to exceed the
4.20 pounds by a weight sufficient to cause a condition of
unbalance pivoting the bin and ice weigh bars 254 and 256 in unison
to theIr position shown in FIG. 4 wherein ice weigh bar 256 engages
stop means 270 to quickly break the electrical continuity between
post H and the ice weigh bar 256 and open the weigh switch between
terminal posts A and H. The weigh switch will remain in its open
position of FIG. 4 and thus prevent further ice harvests being
deposited in the bin until a portion or all of the ice pieces are
removed therefrom and the bin returned to its inserted
position.
While the embodiment of the present invention herein disclosed
constitutes a preferred form, it is to be understood that other
forms might be adopted.
* * * * *