U.S. patent number 3,894,214 [Application Number 05/470,724] was granted by the patent office on 1975-07-08 for door-locking apparatus for a cooking oven.
This patent grant is currently assigned to General Electric Company. Invention is credited to Paul R. Staples.
United States Patent |
3,894,214 |
Staples |
July 8, 1975 |
Door-locking apparatus for a cooking oven
Abstract
A cooking oven having an access door and a safety-locking
apparatus for a latching mechanism of said door, said
safety-locking mechanism including a solenoid operated locking
member requiring an independent manual operation to unlock the
latching mechanism in order to move the latch from the unlatched to
the latched position and vice versa. A high-current switch is
included operable by an actuating member responsive to operation of
the door latching mechanism such that an appliance, such as a
pyrolytic type of self-cleaning oven, may not be operable in the
heat cleaning process unless and until the door latching mechanism,
and thereby the door, are in the latched and locked-closed
position. A cam surface on the switch actuating member serves to
operate the high-current switch and also provides mechanical
advantage for the forced breaking of the switch contacts should
they become welded together.
Inventors: |
Staples; Paul R. (Louisville,
KY) |
Assignee: |
General Electric Company
(Louisville, KY)
|
Family
ID: |
23868774 |
Appl.
No.: |
05/470,724 |
Filed: |
May 17, 1974 |
Current U.S.
Class: |
219/394; 219/393;
219/396; 292/DIG.69; 126/197; 219/413 |
Current CPC
Class: |
F24C
7/08 (20130101); F24C 15/022 (20130101); Y10S
292/69 (20130101) |
Current International
Class: |
F24C
7/08 (20060101); F24C 15/02 (20060101); F27d
001/02 () |
Field of
Search: |
;219/393,396,397,412,413
;126/197 ;292/113,DIG.69 ;337/319 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mayewsky; Volodymyr Y.
Claims
What is claimed is:
1. A cooking appliance comprising an oven cooking cavity formed by
a box-like oven liner and an access door, heating means for
supplying heat energy into the oven cooking cavity, means for
latching the door in the closed position, safety locking apparatus
requiring an intentional and independent operation for locking the
door latching means in the latched and unlatched modes,
respectively, said safety locking apparatus comprising
a support member secured within the appliance and having the
latching means secured thereto;
a high-current electrical switch having a set of contacts, the
switch being mounted on the support member and serving as a
latch-logic device for preventing predetermined phases of operation
of the appliance until the access door is in the latched and
locked-closed position;
switch-actuating means associated with the support member and
movable in response to operation of the door latching means for
actuating the switch;
said switch-actuating means including at least one cam-ramp surface
for mechanically engaging the switch to effect operation thereof
and for providing mechanical advantage to break possibly welded
contacts in the switch; and
a locking member associated with the support member for preventing
operation of the switch-actuating means until intentionally and
independently operated both when the door is latched and when
unlatched and for preventing predetermined phases of operation of
the appliance until the locking member is in the locked
position.
2. A cooking appliance as recited in claim 1 further including an
electroresponsive device responsive to operation of an independent
manual control to become energized for unlocking the locking
member.
3. A cooking appliance as recited in claim 2 wherein the support
member is an elongated, generally U-shaped channel and the
switch-actuating means is a movable bar nested within the channel
and arranged such that operation of the door latching means serves
to effect longitudinal motion thereof.
4. A cooking appliance as recited in claim 3 wherein the switch is
of the normally-closed type and is in the contacts-closed state
when the latching means and thereby the door is latched and locked
closed, and upon unlocking and unlatching the door, the cam-ramp
surface engages the switch to plate it in the contacts-open state
thereby preventing predetermined phases of operation of the
appliance.
5. A cooking appliance as recited in claim 4 wherein the locking
member is a locking bar vertically pivotable about the channel and
having a movable portion engageable in a locked position in either
of two sets of notches in the movable bar, the two sets of notches
corresponding to the latched and the unlatched positions,
respectively, of the safety latching apparatus.
6. A cooking appliance as recited in claim 1 wherein said oven
cooking cavity is of the pyrolytic, self-cleaning type and the
phase of operation to be prevented until the access door is latched
and locked-closed is the pyrolytic, self-cleaning oven process.
7. A cooking appliance as recited in claim 6 wherein the oven
cooking cavity includes a second oven cooking cavity of the
pyrolytic, self-cleaning type, the appliance further including a
second, high-current electrical switch associated with the support
member and a second cam-ramp surface associated with the
switch-actuating means for mechanically engaging the second switch
and arranged such that when the latching means is in the
latched-locked mode, the first switch will be in the
contacts-closed state while the second switch will be in the
contacts-open state, and when the latching means is in the
unlatched-locked mode, the first switch will be in the
contacts-open state and the second switch will be in the
contacts-closed state, thereby providing an interlock such that
both ovens may not be placed simultaneously into the pyrolytic
self-cleaning oven process.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention:
The present invention relates to locking apparatus for an appliance
door latching mechanism and more particularly, to safety locking
apparatus requiring an independent operation for locking an
appliance door latching mechanism and for preventing predetermined
phases of operation of the appliance until the access door is in
the latched and locked closed position.
2. Description of the Prior Art:
Safety dictates that certain appliances be provided with means for
preventing at least certain phases of the operation of the
appliance unless and until the access door associated therewith is
in its closed and locked position, this requiring a definite step
independent of the closing of the access door. A pyrolytic type of
self-clean oven, such as that disclosed in U.S. Pat. No.
3,121,158--Hurko and assigned to the same assignee as the present
invention, is one such appliance requiring such a safety-locking
mechanism. Such an oven would, in the self-cleaning process, reach
temperatures about 900.degree. F and it is certainly desirable, if
not absolutely necessary, that this self-clean process not be
started inadvertently and further that the access door to the oven
not be openable once the temperature within the oven reaches a
predetermined level.
An oven door latching system useful in accomplishing this result is
disclosed in U.S. Pat. No. RE 26,944--Getman, assigned to the same
assignee as the present invention. Therein is disclosed apparatus
for insuring that the oven door be both closed and locked before
the self-cleaning process can be initiated as well as for insuring
that the oven door cannot be unlocked as long as the oven
temperature is above a predetermined level. Disclosed therein is a
locking means for the door locking mechanism, a portion of which is
included in a low voltage circuit working in conjunction with a low
voltage relay type of thermostatic control device. However, in that
arrangement, a cumulation of tolerances problem arises with regard
to the operation of the latch-logic switch actuated by the door
latch mechanism. Furthermore, this hot-wire relay type of
thermostatic controller is slow to respond and thereby produces a
difficult and expensive calibration process during the
manufacturing operation. An evolution process results in the
replacement of the hot-wire relay controller device by a
solid-state temperature controller and ultimately, by a hydraulic,
thermostatic controller (such as the dual range hydraulic
thermostatic control device disclosed in allowed application, Ser.
No. 368,275 -- Staples et al, filed June 8, 1973, now U.S. Pat. No.
3,821,681, and assigned to the same assignee as the present
invention) wherein the full line current for the heating elements
of the oven passes through and is switched by the thermostatic
control device. This then obviates the need for the low voltage
circuit as disclosed in the Getman patent but at the same time
brings about a need for a safety-locking device making use of a
high-current switch therein which can handle the current load for
the heating elements.
Another problem arises, however, that of contact welding in the
high-current, latch-logic switch of the door-latch, locking
mechanism, this resulting from the slow make and break of the
switch contacts. Of course, the immediate thought is to use a
snap-acting type of switch. However, if a switch of this type were
to have its contacts become welded, there would be no mechanical
coupling of sufficient force to break the weld.
A reliable safety locking apparatus is needed therefore for use in
locking an appliance access door latching means and which is
capable of switching line voltage and the corresponding currents
needed for operating such elements as the electric resistance
heaters in a domestic self-cleaning oven.
By the present invention, there is provided an improved safety
locking apparatus for an appliance door latching means, which
apparatus is rather simple of construction, highly reliable, and of
relatively low cost and which is useful for preventing
predetermined phases of operation of the appliance until the access
door thereof is in the latched and locked-closed position and which
solves the problem of contact welding of the latch-logic switch
therein.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided in an
appliance having an access door and means for latching the door in
the closed position, safety locking apparatus requiring an
intentional and independent operation for locking the latching
means in the latched and unlatched modes, respectively. A support
member is secured within the appliance and has the latching means
secured thereto. A high-current electrical switch, having a set of
contacts, is mechanically associated with the support member and
serves as a latch-logic device for preventing predetermined phases
of operation of the appliance until the access door is in the
latched and locked-closed position. Movable means are provided
associated with the support member and responsive to operation of
the latching means for actuating the switch, the movable means
being provided with at least one camramp surface for mechanically
engaging the switch to effect operation thereof and for providing
mechanical advantage to break possibly welded contacts in the
switch. A locking member is provided associated with the support
member for preventing operation of the switch actuating means until
intentionally and independently operated, both when the door is
latched and when unlatched, and for preventing predetermined phases
of operation of the appliance until the locking member is in the
locked position.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a side elevational view, broken away, of a domestic range
including an oven of the pyrolytic, self-cleaning type, broken away
to show the relationship thereto of the preferred embodiment of the
present invention;
FIG. 2 is an enlarged view taken generally along the lines 2--2 of
FIG. 1;
FIG. 3 is an exploded, perspective view of the preferred embodiment
of the present invention, arranged to better show individual
components thereof in relation to each other;
FIG. 4 is a cross-sectional view taken generally along the lines
4--4 of FIG. 2 and enlarged to more clearly show the operating
relationship of certain components; and
FIG. 5 is a schematic representation of a power and control circuit
useful in a pyrolytic, self-cleaning type of electric oven
embodying the safety-locking apparatus of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, there is shown an appliance such as
free-standing electric range 10 which includes a caabinet 12 having
an access door 14 for gaining access to an oven 16 (only a portion
of which is shown by phantom lines) located therein. Access door 14
is of the drop-down type and is arranged to seal the oven 16 by
appropriate means (not shown). A control panel 18 is provided, only
a portion of which is shown, upon which are located the various
controls and switches needed for the proper operation of such a
range.
Oven 16 is of the pyrolytic, self-clean type such as that described
in the aforementioned Hurko U.S. Pat. No. 3,121,158. With such an
arrangement, it has been found necessary to provide means such as
door latch mechanism 20 for latching the door 14 in the closed
position. Door latch mechanism 20 may be of the type disclosed in
U.S. Pat. No. 3,367,697--Fox, assigned to the same assignee as the
present invention. There is also provided safety-locking apparatus
30 for locking the door latch 20 both in the latched and unlatched
modes.
As shown in FIG. 2, door latch 20 includes a manually-operable
handle lever 32 extending through an elongated slot (not shown) on
the front edge of the upper portion of cabinet 12 in a position
just above and parallel to the top edge of the oven door 14. Handle
lever 32 is pivotally secured within a bracket member 34 about an
axis pin 36. Handle lever 32 is shown in the unlatched position and
rotation thereof through an angle of about 60.degree. in a
horizontal plane serves to actuate a latching bolt 38 which is
pivotally actuated by several pin and slot connections between a
recessed position as shown in FIG. 2 to a latching position wherein
the bolt 38 is generally perpendicular to the front wall of the
oven and in mating engagement with a slot 39 partially within the
oven door 14. Further description of the operation of door latch 20
is not necessary to this disclosure but may be had by reference to
the aforementioned Fox patent.
In accordance with the present invention, and referring generally
to FIGS. 2 and 3, safety-locking apparatus 30 is provided requiring
an intentional and independent operation for locking the door latch
20 in both the latched and unlatched modes. Safety-locking
apparatus 30 includes a support member such as an elongated,
generally U-shaped channel 40 suitably secured to the latch bracket
34 which is suitably secured to the cabinet 12. Also forming a part
of the support member is a cover 42 arranged to be suitably secured
to U-channel 40. A high-current electrical switch 44 is
mechanically secured to the cover 42 and is responsive to a
switching actuating means such as movable bar 46 for actuation.
Movable bar 46 is nested within U-channel 40 and is pivotally
connected to door latch 20 as at pin 48. Bar 46 then is free to
travel in a longitudinal direction in response to operation of
handle lever 32 of door latch 20. In actual operation, bar 46 is
free to travel approximately 1 inch as handle-lever 32 is rotated
from the unlatched position through the approximately 60.degree. to
the latched position. The operation of switch 44 by switch
actuating bar 46 will be discussed more thoroughly hereinafter.
Also forming a part of safety-locking apparatus 30 is a locking
member such as locking bar 50 provided with a pivoting surface 51
and a pair of tabs 52 for location and engagement in a pair of
slots 54 located on stationary U-channel 40. Locking bar 50 then is
vertically pivotable about the U-channel 40 and is further provided
with a second pair of tabs 56 arranged for engagement with two sets
of notches located on the movable bar 46. Notch set 58 corresponds
to the unlatched position of the door latch and notch set 60
corresponds to the latched position thereof. By this arrangement
then, movable bar 46 and thereby handle-lever 32 are not free to
move if locking bar 50 is in its locked position, that is, if the
locking bar is downward in locking engagement with movable bar 46.
In other words, if door latch 20 is in its unlatched position, an
intentional and independent operation must be performed to lift
locking bar 50 from its locked position in locking engagement with
movable bar 46 in order to place the door latch mechanism into the
latched mode or position. To facilitate the operation of locking
bar 50, there is provided an electroresponsive device such as
solenoid 62 having an armature 64 coupled mechanically with locking
bar 50, such that energization of solenoid 62 causes armature 64 to
be drawn upwardly thereby effecting the lifting of tabs 56 of
locking bar 50 from engagement with the respective notches of
movable bar 46 thereby allowing the operation of the door latch
mechanism. Upon the de-energization of solenoid 62, armature 64
falls back downward, partially in response to a compression spring
66 which serves to force locking bar 50 back into locking
engagement with movable bar 46. Locking bar 50 in the up or
unlocked position, engages switch 44, a normally closed device as
will be hereinafter described to open the switch contacts to
prevent actuation of certain portions of a circuit, to be described
later. If for any reason, the locking bar 50 is in the unlocked
position, the switch 44 will be in the contacts-open state. An
independent manual control may be provided on the control panel 18
for closing a control circuit for effecting momentary energization
of solenoid 62.
Returning now to operation of the high-current switch 44, it can be
seen in FIG. 3 that movable bar 46 is provided with a cam-ramp
surface 68 for mechanically engaging switch 44 to effect operation
thereof. Referring also to FIG. 4, switch 44, which for purposes of
this embodiment of the invention has been chosen to be of the
normally closed type, and functions with a slow make and break of
the contacts, is shown in the contacts-open position. Switch 44 is
provided with a plunger 70 for engagement with cam-ramp surface 68
for effecting operation of the switch. As shown in this view, door
latch mechanism 20 is in the unlatched position where it is desired
that switch 44 be in the open state. Plunger 70 normally travels
through a distance vertically of about one quarter inch and here is
shown in its uppermost position. As can be envisioned then, when
door latch 20 is in its latched and locked position, cam ramp
surface 68 will have moved to the left (as viewed in FIG. 4) by
approximately 1 inch thereby allowing plunger 70 to clear cam ramp
surface 68 thereby resting in its full down position which
corresponds to the switch normally closed state. Since switch 44 is
of the high-current type and for such an application in a pyrolytic
type of self-clean oven, it carries the line voltage and full
current for the electrical resistance heating elements of the oven,
the switch contacts are prone to welding. This problem has been
obviated by the mechanical advantage of the cam ramp surface 68
making forced mechanical contact with plunger 70 thereby causing
the breaking of the contacts of switch 44 should they become
welded.
Turning now to FIG. 5, there is shown, by schematic representation,
a circuit useful for the operation of a pyrolytic type of
self-cleaning oven and wherein the present invention is
incorporated. FIG. 5 then will give a better understanding of how
switch 44 serves as a latch-logic device for preventing
predetermined phases of operation such as the pyrolytic self-clean
process until the access door 14 is in the closed and
latched-locked position. The oven is furnished with an electrical
service of three wire Edison source of power; nominally 240 volts,
single phase, 60 Hz AC, usually available in the average residence
having adequate wiring. This voltage source is fed to the oven
through a three wire cable having a pair of line wires L1 and L2
with a voltage of 240 volts therebetween and grounded neutral
conductor N for supplying the electrical load of the oven. This
electrical load is characterized by three heating elements; the
baking element 100, a broiling element 102 and a mullion heater
104. The bake element 100 is usually located adjacent the bottom
wall of the oven, the broil element 102 is usually located adjacent
the top wall of the oven and the mullion heater 104 is usually
located wrapped around the outside of the oven liner adjacent the
front opening for replenishing the heat loss through and around the
door opening during a high temperature, pyrolytic, heat cleaning
operation. These heating elements 100, 102 and 104 are arranged in
circuits in combination with an oven select switch 106 for setting
up varied combinations of heating elements at different voltages to
obtain a variety of heating rates. A manually settable oven
temperature controller 108 including a logic switch is also
provided for controlling the temperature within the oven at
preselected temperatures during baking operations and a maximum
temperature during oven cleaning operations. Such a temperature
controller 108 is arranged serially with the heating elements 100,
102 and 104 for opening and closing the power circuit to the
heating elements as a function of oven temperature with relation to
the temperature predetermined or preset by the temperature
controller 108.
The oven select switch 106 is provided with a series of line input
terminals denoted as L1, N, L.sub.1 and L2, as well as a series of
load terminals denoted as K, J, and P. Switch 106 is provided with
a plurality of switch contacts 112 through 126. These switch
contacts are labeled with the particular cooking or cleaning
operation that is involved when such contacts are closed. For
example, during a baking or a time baking operation, the contacts
112 and 113, 118 and 119, and 124 and 125 are closed. During a
broiling operation, contacts 116 and 117, and 124 and 125 are
closed. During a cleaning cycle, contacts 113 and 114, 115 and 116,
119 and 120, 121 and 122, and 125 and 126 are closed.
Should there be a component failure during an operation of baking,
time baking or broiling and should the oven temperature rise above
the preset temperature of the oven temperature controller 108 and
reach a temperature of say 600.degree. - 650.degree. F, the first
switch 130 of double-point thermal switch 132 would be caused to
open thereby opening the circuits and de-energizing the heating
elements to prevent a runaway temperature condition. Thus, first
switch 130 of the thermal switch serves as an over-temperature,
limit control when the oven is in a normal cooking operation.
Second switch 134 of thermal switch 132 is arranged to be in an
operating circuit only during the pyrolytic heat cleaning mode of
operation. At temperatures below about 540.degree. F, the switch
contacts 136 and 136' are in their normally closed state to allow
actuation of door interlock solenoid 62. At temperatures above
approximately 540.degree. F, contacts 138 and 138' are closed to
provide power for cooling fan 140 which causes air to be circulated
between the oven inner wall and the oven outer wall so as to keep
the outer walls cooled. After a temperature dwell of approximately
10.degree. F, or somewhere near approximately 550.degree. F,
normally closed contacts 136 and 136' are opened cutting power from
the circuit feeding solenoid 62 and a momentary switch 142 thus
preventing the electrical circuit for the door latch locking
apparatus from being actuated. Contacts 138 and 138' remain closed
until the interior temperature of the oven drops below
approximately 540.degree. F.
In order to set up the self-cleaning process and the electrical
circuit therefor, there are several preliminary operations that
must first be performed. It is imperative that the oven access door
14 first be closed and then latched and locked before the self
cleaning process can be initiated, and also that the door remain
closed and incapable of being operated or opened while the oven
temperatures are above normal cooking temperatures. In other words,
the safety-locking apparatus of the present invention must be
actuated before the handle lever 32 may be shifted. This is
accomplished by coupling solenoid 62 across line L1 and neutral
conductor N through momentary switch 142. Thus at temperatures
below the operating temperature of second switch 134, that is below
approximately 540.degree. F, it is possible to shift handle lever
32 by manually closing momentary switch 142 thereby energizing
solenoid 62 which in turn picks up locking bar 50 allowing the
operation of door latch mechanism 20. However at temperatures above
normal cooking temperatures, that is above approximately
550.degree. F, contacts 136 and 136' of second switch 134 will be
opened thereby disabling energizing circuit for solenoid 62 thus
preventing access to the oven during the heat cleaning cycle. Of
course oven selector switch 106 and temperature controller 108 must
be arranged by the operator to call for the self-cleaning process
thereby closing the necessary contacts as hereinbefore
described.
To facilitate an understanding of the operation of latch-logic
switch 44, it is felt that it would be useful at this time to trace
the circuit of operation for the self-clean process. Since such a
self-cleaning process would normally be a timed operation, a switch
144 responsive to operation of a timer mechanism (not shown) is
closed thereby coupling line L2 into a portion of oven selector
switch 106. Since contacts 125 and 126 are closed, you may further
trace the circuit to switch 44, the latch-logic device. As has been
described, switch 44 will be in the closed state when the access
door 14 is in the closed and latched-locked position. Contacts 162
and 164 of the logic switch of temperature controller 108 are
closed to apply power to neon lamp 166 to indicate that the
self-clean process is under way. Then trace the circuit through to
the temperature controller 108 and thence to the parallel
combination of bake heating element 100, broiling element 102 and
mullion heater 104. These are then coupled into oven select switch
106 through load terminals K and J, thence through the appropriate
contacts to terminal N and the circuit is thence completed by
continuing to neutral conductor N. The three heating elements 100,
102 and 104 are therefore connected in parallel at half-voltage
across line L2 and neutral conductor N in order to obtain a heating
rate somewhat lower than the heating rate of the normal baking
operation. Since contacts 162 and 164 are closed, it is readily
seen that heating elements 100, 102 and 104 cannot be energized
unless switch 44 is closed and this only occurs when the access
door is in the closed and latched-locked position and further when
locking bar 50 is down in the locked position.
It is not felt necessary at this point to go into any further
detail of the power and control circuit since the present invention
is centered around a safety-locking apparatus useful in an oven
during a pyrolytic self-cleaning process. It should be mentioned
however that certain ranges are provided including a second oven of
the pyrolytic self-clean type. With such an arrangement, it is
desirable that only one of these ovens be operated in the pyrolytic
self-cleaning process at any one time due mainly to the amount of
heat generated in the process. Referring generally then to FIGS. 2,
3 and 4, it can be seen that for such an operation there may be
provided a second high-current electrical switch 148 also
responsive to operation of movable bar 46 for its operation. There
has also been provided located on movable bar 46 a second camramp
surface 150 for engaging this second high-current switch 148. With
such an arrangement then, when the door latch 20 and thereby access
door 14 is in its closed and latched-locked position, first switch
44 will be in its closed state while second switch 148 will be in
the open state. Likewise when the door latch 20 and thereby the
door 14 is in the unlatched mode, and the safety-locking apparatus
30 is in the locked position, first switch 44 will be in the open
state and second switch 148 will be in the closed state. This then
provides an interlock such that both ovens cannot be placed
simultaneously into the pyrolytic self-clean process.
It should be apparent to those skilled in the art that the
embodiment described heretofore is considered to be the presently
preferred form of this invention. In accordance with the Patent
Statutes, changes may be made in the disclosed apparatus and the
manner in which it is used without actually departing from the true
spirit and scope of this invention.
* * * * *