Patent Publication Number: US-6992258-B2

Title: Switching device for gas operated appliance

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to control apparatus for a device, such as an appliance, having a control knob rotatable between an “OFF” and an “ON” position. 
   It is commonly known to control an appliance such as an oven by means of one or more manually operated controls, including control knobs that can be rotated between “OFF” and “ON” positions. Stoves and ovens that employ natural gas as a heating fuel are commonly used both at home and commercially. One such form of oven that can employ gas as a fuel is a pizza oven and, in particular, such ovens that are large enough and suitable for commercial operators and commercial outlets for pizzas. 
   A known difficulty that is commonly encountered by the operators of pizza ovens, particularly those at commercial establishments, is that such ovens can require a significant amount of time to heat up to the required temperature. Accordingly, if the oven must be turned on manually by its operator, it is often necessary for the operator to attend at the commercial premises where the oven is located early, that is prior to the establishment opening for business, in order to turn the oven on so that it will reach the required temperature for pizza making when this becomes necessary. This can be a substantial inconvenience to and expense for the operator of the pizza oven. Other types of ovens may also need to be turned on by their operators at a time well in advance of the time at which they will actually be used for cooking or baking. 
   Although timing devices are common in home baking devices such as ovens, microwave ovens or slow cooking pots, the use of timing devices to turn on large commercial ovens such as pizza ovens is not common at the present time. However, one known timing apparatus for a commercial pizza oven is taught in U.S. Pat. No. 5,464,953 issued Nov. 7, 1995. This U.S. patent teaches a device capable of turning on a pizza oven that has a timer, a solenoid, a toggle switch and a special adaptor plate for mounting next to the control knob which operates the gas valve of the oven. The control knob is spring biased in a rotational direction toward the “ON” position of the knob. The timer is provided to energize the solenoid at a preset time duration, with the solenoid rod being coupled to a pivotable actuating arm, the free end of which is positioned for engagement with a detent formed in the adaptor plate. The toggle switch is in an electrical circuit with the timer and the toggle is physically positioned to be operated by a member projecting from the actuating arm. 
   More recent U.S. Pat. No. 6,041,768 issued Mar. 28, 2000, describes an oven with an electrical timer for saving and controlling gas. The clock timer is electrically connected to an on/off pilot and gas valve for automatically turning on or off the gas flow to the oven burner. The pilot and gas valve is a known form of electromechanical valve such as that sold by the White-Rodgers Division of Emerson Electric Co. 
   It is an object of the present invention to provide a reliable control apparatus having a timer which can be used to control a device such as an appliance having a control knob rotatable between an “OFF” and an “ON” position. This apparatus is able to turn on the device or appliance at a selected time and in a reliable manner. 
   It is another object of the invention to provide a novel control apparatus for a device such as an appliance having a control knob, which can be made at a reasonable cost and using known, readily available components and parts. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the invention, a control apparatus for a device having a control knob rotatable between an “OFF” and an “ON” position includes a timer that can be preset to a selected time at which the control knob is to be turned from the “OFF” position to the “ON” position. The apparatus further includes an actuator motor for turning the control knob to the “ON” position, the operation of this motor being controlled by the timer whereby the motor is turned on by the timer at the selected time during use of the control apparatus. The motor has a rotatable output shaft and also means for mounting the motor at a suitable location for turning the control knob. There are also means for operatively connecting the output shaft of the motor to the control knob so that the control knob is turned to the “ON” position when the motor is turned on. The control apparatus also has a mechanism for automatically returning the control knob to the “OFF” position when the motor is turned off. 
   Preferably, the mechanism for automatically returning the control knob is a spring attached to the connecting means and, in a particularly preferred embodiment, this spring is a coil spring that extends around a shaft on which the control knob is mounted. 
   According to another aspect of the invention, a combination timer and controller for a gas operated appliance includes a rotatable control shaft having a first end connectable to a gas valve of the appliance in order to operate same and a control knob attachable to a second end of the control shaft located opposite the first end. The combination also has a timer that can be preset to a selected time at which the control shaft is to be turned from a first position corresponding to an “OFF” position of the control knob during use thereof to a second position corresponding to an “ON” position of the control knob during use thereof. An actuator motor is provided to turn the control shaft to the second position and the operation of this motor is controlled by the timer so that the motor is turned on by the timer at the selected time when the timer is used. The combination further includes means for mounting the motor at a suitable location for turning the control shaft and a mechanism for operatively connecting the motor to the control shaft so that the motor is capable of rotating the control shaft to the second position. There is also a mechanism for rotating the control shaft to the first position and the control knob to the “OFF” position when the motor is turned off. 
   The preferred rotating mechanism comprises a coil spring and the connecting mechanism between the motor and the control shaft includes a driven gear fixedly mounted on the control shaft with one end of the coil spring being attached to this driven gear. 
   According to another aspect of the invention, a combination timer and controller for operating a valve of an appliance includes a manually rotatable control device including a control knob and a control shaft connected to the knob, this control shaft being connectable to the valve for operation of the latter. There is also provided a timer for timing the operation of the valve and an electric actuator motor for rotating the control device from an “OFF” position to an “ON” position. The motor in use is controlled by the timer which is operatively connected thereto. The motor is turned on by the timer at a selected time during use of the combination. The combination also includes means for mounting the motor in a suitable position for operation and a mechanism for operatively connecting the motor to the control device so that the control device is rotated to the “ON” position when the motor is turned on and operates. A spring mechanism returns the control device to the “OFF” position when the motor is turned off. 
   The preferred combination includes an electrical control circuit operatively connected to the timer and the actuator motor. This circuit includes an electrical switch for manually controlling operation of the control circuit. 
   Further features and advantages will become apparent from the following detailed description taken in conjunction with the accompanying drawings. 

   
     DETAILED DESCRIPTION OF DRAWINGS 
       FIG. 1  is a partial front view of a gas-heated oven equipped with the control apparatus of the invention; 
       FIG. 2  is a cross-sectional view taken along the line II—II of  FIG. 1  showing the control apparatus of the invention; and 
       FIG. 3  is a circuit diagram illustrating a preferred electrical circuit for the control apparatus. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     FIG. 1  shows a right side portion of an oven  10  such as a pizza oven. Except for the control apparatus of the invention which is indicated generally at  12 , the oven  10  can be of standard construction and, accordingly, a detailed description herein is deemed unnecessary. A control knob  14  can be used to manually turn OFF or turn ON the flow of gas fuel to the oven. The control knob  14  is rotatable between an “OFF” and an “ON” position. The control knob  14  is mounted on an outer end of a rotatable control shaft  16  having an inner end connectible to a standard gas valve  18  for the oven in order to operate same. It will be appreciated that although the present invention is described in the context of an oven, the control apparatus of the invention can be used in other appliances for which there may be a desire to turn on the appliance at a preselected time using a timer. The gas controlled by the valve  18  can be natural gas or propane or another type of gas suitable for heating an oven. 
   The outer or second end of the control shaft  16  can be formed with a flat side at  20  and the flat sided end section of the shaft extends into a hole formed in the knob of the same cross-sectional shape. Thus, the knob is non-rotatably connected to the end of the shaft and rotates with same. The shaft  16  is rotatably mounted in an upper bearing  22  and a lower bearing  24 . Extending between these two bearings is a spacer sleeve  26 . The upper bearing  22  is mounted in a front wall  27  of a control housing  28 . The lower bearing  24  can be mounted in internal support wall  30  of the housing, this wall also forming a back for the housing so that the major components of the control apparatus are enclosed. Extending between the front wall  27  and the wall  30  are sidewalls including sidewalls  32  and  34 . The wall  30  can be secured to the sidewalls by means of integral, downwardly extending flanges  34 . The control housing itself can be connected to an external wall of the oven, such as front wall  36 , by means of outwardly projecting connecting flanges  38  and  40 . The control apparatus  12  includes a timer  42 , the front of which can be located in and aligned with the front wall  27  of the housing. This timer, which per se can be of standard construction and operated electrically, can be preset to a selected time at which the control knob  14  is to be turned from the “OFF” position to the “ON” position. The timer is preferably of the type having a dial  44  (see  FIG. 1 ) which can be set to a particular time of day, for example, 9:00 a.m. at which the control knob will be turned to the “ON” position. It is also possible to use a timer which is designed simply to rotate the control knob to the “ON” position after a certain time has elapsed, for example, eight hours. Both types of timers are within the scope of the present invention. The illustrated timer  42  is mounted on the wall  30  by means of a plurality of machine screws  46  secured in place by nuts  48 . Although only two machine screws  46  are shown in  FIG. 2 , there can, for example, be four of these screws, one screw being located at each corner of the timer housing. In order to properly position the timer in the housing, spacer sleeves  50  can extend around the screws and extend between the wall  30  and the back of the timer. 
   Another component of the control apparatus is an actuator motor  52  and this motor can also be of standard construction for a small, electric motor. This motor is capable of turning the control knob  14  via the shaft  16  to the “ON” position with the operation of the motor being controlled by the timer  42 . Thus, the motor is turned on by the timer at the selected time during use of the control apparatus. As usual, the motor  52  is provided with a rotatable output shaft  54  indicated in dashed lines in  FIG. 2 . It will be appreciated that the motor  52  can be rigidly mounted in the control housing in a variety of ways. The mounting mechanism for the motor mounts the motor at a suitable location for turning the control knob  14  via the shaft  16 . As illustrated, the motor is supported by means of machine screws  56 , only one of which is shown for ease of illustration. These screws are connected to the wall  30  by means of nuts  58 . The motor  52  is suitably located in the housing by the use of spacers  60  through which these screws  56  extend. The spacer extends between the wall  30  and a connecting flange  62  for the motor. 
   There is a drive mechanism or drive means for operatively connecting the output shaft of the motor to the control knob so that the control knob is turned to the “ON” position when the motor is turned on. The aforementioned control shaft  16  can be considered part of this drive mechanism or separate therefrom. The preferred drive mechanism includes a driven gear  65  which is mounted fixedly to the control shaft  16 , and a drive gear  66  rotatable by rotation of the output shaft  54  of the motor and in engagement with the driven gear  65 . As illustrated, the drive gear  66  is substantially smaller than the driven gear. In order to operatively connect the shaft  54  with the drive gear  66 , a suitable gear arrangement or system can be provided in gear enclosure  70  located directly below the motor  52  and connected thereto. As such gear systems are well known and as a variety of such systems could be used, a detailed description herein is deemed unnecessary. The gear system should be set up to take into account the size or power of the motor  52  and a suitable speed of rotation for the knob  14  when the motor is turned on. Arranged next to the gear  65  is a thrust washer  72 . 
   The control shaft  16  can be connected by means of a standard shaft coupling  74  to a gas valve stem  76 . It will be understood that the rotation of the stem  76  operates the gas valve  18 . The direction of gas flow through the valve is indicated by the arrow A but it will be understood that the gas flow could be in the opposite direction. The aforementioned valve stem  76  extends through a hole  80  formed in the front wall  36  of the oven. 
   Another component of the control apparatus  12  is a mechanism or means for automatically returning the control knob  14  to the “OFF” position when the motor is turned off. In the illustrated preferred embodiment, this returning mechanism is a coil spring  82  which is attached to the connecting mechanism that connects the output shaft of the motor to the control knob. As illustrated, the preferred coil spring  82  extends around the shaft  16  and it has one end  86  which is connected to the driven gear  65 . The opposite end  88  of the spring can be connected to any suitable rigid support to prevent movement of this end, for example, it can be connected to a sidewall of the housing  28 . Alternatively, the end  88  can simply be arranged in the housing so that it prevents rotation of the coil spring about the central axis of the shaft  16  when the driven gear  65  is turned by the motor. It will be appreciated that the spring  82  must be sufficiently strong that it is capable of returning the control knob to the “OFF” position when the motor  52  is turned off. 
   It will be seen that the preferred control housing  28  as illustrated is able to contain all of the major components of the control apparatus, although it does not contain the control knob  14 , which can be arranged on the front thereof. Thus, the control housing contains the timer  42 , the actuator motor  52 , the gear system for connecting the output shaft of the motor to the control knob, and the spring mechanism for automatically returning the control knob to the “OFF” position. 
   Turning now to  FIG. 3  of the drawings which illustrates a preferred form of electrical control circuit  90 , the control circuit is operatively connected to the timer  42  and the actuator motor  52 . The circuit is provided with electrical power through the usual power line  92  which can be protected by a standard fuse  94 . The control circuit includes an electrical switch  96  which preferably is a three position switch as shown. The switch  96  can be used to manually control operation of the control circuit  90 . The three positions of the switch are indicated at S 1 , S 2  and S 3 . In the first position S 1  of the switch, the motor  52  is provided with power from the main power line and turns the control knob  14  to the “ON” position. The second position S 2  is used when the timer is used or has been used to preset the selected time for turning on the oven. The third position S 3  is used when the motor is turned off. 
   The preferred illustrated circuit also includes indicator lights  98 ,  100  and  102  which preferably are of different colours. For example, the light  98  can be amber, the light  100  can be red when lit, and the light  102  can be green. Located between the contact point S 2  of the switch and each of the indicator lights  100  and  102  are contact timers  104  and  106  respectively. The lights indicate the current operational status of the control apparatus during use thereof. It will also be seen that the lights  98 ,  100  and  102  correspond respectively to the three positions of the switch  96 . Although not shown in  FIGS. 1 and 2 , the indicator lights can be mounted either on the control housing  28  where they will be visible or possibly on the front of the oven or appliance itself. The amber light is simply to indicate that electrical power is available to the oven but the oven is turned off and the timer has not been set. The green light indicates the power is being provided to the motor  52  and, as a result, the oven is turned on. 
   The timer  42  is set when the switch  96  is moved from position S 3  to S 2 , at which time the red lamp  100  is turned on. When the timer has ticked down to the required time for turning on the oven, power is then provided by closure of the contacts at  106 , this closure causing the green lamp  102  to come on. The position S 1  of the switch is simply the manual “ON” position for the oven which can be turned on manually by simply turning the control knob  14  to this position. 
   An illustrated preferred feature of the control circuit  90  is a high limit thermostat  110  that is located in the circuit between switch contact S 1  and the motor  52 . This is a safety feature designed to shut off the oven if it reaches a certain, predetermined maximum temperature. 
   Another preferred feature illustrated in  FIG. 2  is a manual interlock or locking device  125 . This can be mounted on the front wall  27  adjacent to the control knob  14  by means of screw  126 . The interlock  125  can be moved manually into or out of a suitably sized cavity or recess  128  formed in one side of the knob  14 . The interlock can be used to manually set the knob  14  is the “ON” position when required. Thus, with this device, the control knob can be held in the “ON” position even though the motor  52  is not operating. It will be understood that the mounting screw  126  is slidable back and forth in a slot formed in the wall  27  (but not shown). 
   It will be understood that the control knob  14  and the control shaft  16  can be formed as an integral, one-piece part, if desired, rather than two separate parts. Also, these two parts can together be considered a manually rotatable control device and the actuator motor  52  serves the purpose of rotating this control device from an “OFF” position to a “ON” position. Furthermore, although the illustrated preferred embodiment uses a gear system to connect the output of the motor to the control shaft  16 , it will be appreciated by those skilled in the art that it is also possible to construct a control apparatus wherein the motor  52  is connected by a suitable drive unit to the knob  14  itself, rather than the shaft  16 . 
   It will also be appreciated that the manual switch  96  can be replaced by an electrically operated digital switch, if desired. Such digital switches are well known for electronic and electrical controls and therefore a detailed description herein is deemed unnecessary. 
   It will be appreciated by those skilled in the art of controls for equipment and appliances that various modifications and changes can be made to the above described control apparatus without departing from the spirit and scope of this invention. Accordingly, all such modifications and changes as fall within the scope of the appended claims are to be considered as within the scope of this invention.