Abstract:
An electrical appliance includes a housing carrying a drive motor, a temperature sensor and a controller. The temperature sensor monitors the operating temperature of the drive motor. The controller is responsive to the temperature sensor. The controller adjusts the current applied to the drive motor in response to a high temperature condition detected by the temperature sensor.

Description:
[0001]     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/565,329 filed on Apr. 26, 2004. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates generally to the electrical appliance field and, more particularly, to a thermal protection system for electrical appliances in general and, more particularly, to an electrical appliance incorporating such a system.  
       BACKGROUND OF THE INVENTION  
       [0003]     Substantially any electrical appliance may at one time or another be subjected to operating extremes which may cause the operating temperatures of the appliance to rise to a sufficiently high temperature so as to potentially cause damage to the mechanical workings of the device or even its housing or enclosure. The present invention relates to an apparatus and method for (1) sensing when the operating temperature of an electrical appliance rises above a predetermined high temperature condition and (2) adjusting the current flow to at least a portion of the device in response to sensing such a condition.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention broadly relates to any electrical appliance comprising a housing and a drive motor, temperature sensor and controller all carried on the housing. The temperature sensor monitors an operating temperature of the drive motor. The controller is responsive to the temperature sensor and adjusts current applied to the drive motor in response to a high temperature condition detected by the temperature sensor.  
         [0005]     More particularly, the present invention relates to an electrical appliance such as a vacuum cleaner including a porous filter bag or a dirt cup carried on the housing. Further the electrical appliance includes a rotary agitator carried on the housing. The electrical appliance may comprise a canister type vacuum cleaner or an upright type vacuum cleaner.  
         [0006]     In addition the electrical appliance may include a restart actuator connected to the controller. Upon the temperature sensor detecting the high temperature condition, the controller maintains the current applied to the drive motor in an adjusted condition until both the motor cools below the high temperature condition and the restart actuator is engaged.  
         [0007]     The electrical appliance may also include a position sensor connected to the controller. Upon the temperature sensor detecting the high temperature condition, the controller maintains current applied to the drive motor in an adjusted condition until both the motor cools below the high temperature condition and the position sensor detects the electrical appliance in a restart position. The position sensor may, for example, comprise an accelerometer or a mercury switch.  
         [0008]     Still further the electrical appliance may include an indicator for indicating when the high temperature condition has been detected. The indicator may, for example, be selected from a light source and/or a sound source.  
         [0009]     The present invention may also be defined as a vacuum cleaner comprising a housing and a suction generator, temperature sensor, rotary agitator and controller all carried on the housing. The suction generator includes a drive motor. The temperature sensor monitors the operating temperature of that drive motor. The controller is responsive to the temperature sensor and adjusts current applied to the drive motor in response to a high temperature condition detected by the temperature sensor.  
         [0010]     The vacuum cleaner may include a porous filter bag or a dirt cup carried on the housing. The vacuum cleaner may be of the canister type or an upright type. Further, the drive motor may also drive the rotary agitator in addition to the suction generator.  
         [0011]     The present invention may also be defined as a vacuum cleaner comprising a housing and a dirt collector carried on the housing. The vacuum cleaner also includes a suction generator having a first drive motor. Additionally, the vacuum cleaner includes a first temperature sensor for monitoring an operating temperature of the first drive motor. Further the vacuum cleaner includes a rotary agitator and a second drive motor for driving that rotary agitator. Additionally, the vacuum cleaner includes a second temperature sensor for monitoring the operating temperature of the second drive motor. A controller carried on the housing is responsive (a) to the first temperature sensor and adjusts current applied to the first drive motor in response to a high temperature condition detected by the first temperature sensor and (b) to the second temperature sensor and adjusts current applied to the drive motor in response to a high temperature condition detected by the second temperature sensor.  
         [0012]     Still further describing the invention, the vacuum cleaner includes a restart actuator connected to the controller. Upon one of the two temperature sensors detecting a high temperature condition, the controller maintains current applied to the first or second drive motor in an adjusted condition until the first or second drive motor cools below the high temperature condition and the restart actuator is engaged.  
         [0013]     The vacuum cleaner may also include a position sensor connected to the controller. Upon the first or second temperature sensor detecting a high temperature condition, the controller maintains current applied to either drive motor operating at a high temperature in an adjusted condition until the drive motor cools below the high temperature condition and the position sensor detects the vacuum cleaner in a restart position. The position sensor is typically an accelerometer or a mercury switch.  
         [0014]     In accordance with yet another aspect of the present invention, a method is provided for thermally protecting an electrical device. The method comprises equipping the electrical device with a temperature sensor and a controller responsive to the temperature sensor. Further the method includes the step of adjusting the current applied to at least a portion of the electrical device in response to the temperature sensor sensing a high temperature condition. In addition the method includes the step of maintaining the current applied to at least a portion of the electrical device in the adjusted condition until both the high temperature operating portion of the electrical device cools below the high temperature condition and an additional predetermined restart condition is met. The method of the present invention may be more specifically defined as a method of thermally protecting a vacuum cleaner.  
         [0015]     In accordance with yet another aspect of the present invention an electrical device is provided. The electrical device comprises an electric motor, a temperature sensor monitoring an operating temperature of the electric motor and a controller responsive to the temperature sensor. The controller adjusts the current applied to the electric motor in response to a high temperature condition detected by the temperature sensor. The device may further include a restart actuator connected to the controller. Upon the temperature sensor detecting a high temperature condition, the controller maintains an adjusted condition until both the motor cools below the high temperature condition and the restart actuator is engaged. The device may also include a position sensor connected to the controller. Upon the temperature sensor detecting the high temperature condition, the controller maintains the adjusted condition until both the motor cools below the high temperature condition and the position sensor detects the electrical device in a restart position.  
         [0016]     In the following description there is shown and described multiple embodiments of this invention simply by way of illustration of several modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawing and descriptions will be regarded as illustrative in nature and not as restrictive. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention, and together with the description serve to explain certain principles of the invention. In the drawings:  
         [0018]      FIG. 1  is a perspective view of an upright vacuum cleaner illustrating just one possible embodiment of the present invention;  
         [0019]      FIG. 2  is a schematical view of one possible system for sensing a high temperature condition in an electrical appliance such as the vacuum cleaner shown in  FIG. 1 ; and  
         [0020]      FIG. 3  is a schematical view of another embodiment for sensing a high temperature condition in an electrical appliance such as the upright vacuum cleaner of  FIG. 1 . 
     
    
       [0021]     Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     Reference is now made to  FIG. 1  illustrating a vacuum cleaner  10  equipped with the thermal protection system  12  of the present invention as illustrated by alternative embodiments in  FIGS. 2 and 3 . The vacuum cleaner  10  in the illustrated embodiment is an upright vacuum cleaner including a handle or canister assembly  14  pivotally connected to a nozzle assembly  16 . The nozzle assembly  16  includes a suction inlet  18 . A rotary agitator  20  is mounted in the suction inlet  18 . The rotary agitator  20  includes brushes, wipers, beater bars, bristle tufts or the like and is rotated relative to the nozzle assembly  16  to beat dirt and debris from an underlying carpet or rug being cleaned.  
         [0023]     The canister or handle assembly  14  includes a dirt collector  22 , which may take the form of a porous filter bag or dirt cup, and a suction generator  24 . Typically the suction generator  24  comprises a fan driven by a motor  26 . In some vacuum cleaners  10 , the motor  26  that drives the suction fan also drives the rotary agitator  20 . In other vacuum cleaners  10 , a second, separate motor  28  is provided for driving the rotary agitator  20 .  
         [0024]     In use, the rotary agitator  20  beats dirt and debris from the nap of an underlying rug or carpet being cleaned. That dirt and debris is then drawn into the dirt collector  22  through the suction inlet  18  by means of the negative pressure generated by the suction generator  24 . The dirt and debris is trapped in the dirt collector  22  while the now clean air is directed over the motor  26  of the suction generator  24  to provide cooling before being exhausted into the environment.  
         [0025]     Under certain operating conditions the motor  26  of the suction generator and the motor  28  of the rotary agitator (if present), may become overheated. In extreme cases this has the potential to result in damage to the motor  26  or  28  or even the housing of the nozzle assembly  16  or canister assembly  14  containing the motor. Advantageously, the thermal protection system  12  of the present invention eliminates this cause for concern.  
         [0026]     As illustrated in the embodiment shown in  FIG. 2 , the thermal protection system  12  of the present invention includes a first temperature sensor in the form of a thermocouple  30  connected to the suction generator motor  26 , a second temperature sensor in the form of a thermocouple  32  connected to the rotary agitator motor  28  and a controller  34 , such as a dedicated microprocessor, connected to the thermocouples  30 ,  32  by lead wires  36 ,  38  respectively. As should be further appreciated the illustrated embodiment also discloses a restart actuator  40  in the form of a push button switch and a high temperature indicator in the form of a light source  42 .  
         [0027]     During normal vacuum cleaner operation, the first thermocouple  30  monitors the operating temperature of the suction generator motor  26  and the second thermocouple  32  monitors the operating temperature of the rotary agitator motor  28 . More specifically, each thermocouple  30 ,  32  sends an electrical control signal along the respective lead lines  36 ,  38  to the controller  34  representative of the sensed operating temperature. So long as the operating temperature of both motors  26 ,  28  stays below a predetermined temperature, normal vacuum cleaner operation is maintained. In contrast, when either thermocouple  30 ,  32  senses that either motor  26 ,  28  is operating above the predetermined temperature (that is, detects a high temperature condition) such a condition is indicated by the signal sent along the appropriate lead lines  36 ,  38 . The controller  34  responds to the high temperature condition signal by adjusting the electrical current applied to the motor  26 ,  28  for which the high temperature condition has been detected. For most applications that means the controller  34  will interrupt the application of current to the motor  26 ,  28  in question. For certain applications, however, this may simply mean decreasing the current being applied.  
         [0028]     For those vacuum cleaners  10  equipped with an indicator  42 , the controller  34  also energizes the indicator in response to the detected high temperature condition. In the embodiment illustrated in  FIG. 2  the indicator  42  is a light source (e.g. incandescent bulb, LED) that is illuminated. It should be appreciated, however, that the indicator  42  could just as easily be a sound source such as a buzzer or a combination of the two.  
         [0029]     When current application to the motor  26 ,  28  in question is interrupted by operation of the controller  34 , that motor begins to cool. Once it cools below the predetermined temperature that establishes the high temperature condition, the motor  26 ,  28  in question is not immediately re-energized. Instead, the current adjustment, in this case an interruption of the application of current, is maintained until the operator also engages the restart actuator or switch  40 . Accordingly, it should be appreciated that once a motor  26  or  28  has been detected as operating above the predetermined temperature or in a high temperature condition, it is not re-energized until two conditions are met. The first is the motor  26  or  28  has cooled below the predetermined temperature. The second is the operator has engaged the restart actuator  40  and closed the circuit or lead lines  43  leading to the controller  34 .  
         [0030]     An alternative embodiment of the thermal protection system  12  of the present invention is illustrated in  FIG. 3 . In this embodiment the temperature sensors are first and second bimetallic switches  44 ,  46  instead of first and second thermocouples  30 ,  32 . The operation of the thermal protection system  12  is, however, similar to the operation described above with respect to the first embodiment. More particularly, if the suction generator motor  26  or the rotary agitator motor  28  operates above the predetermined temperature, the contacts of the bimetallic switch  44 ,  46  associated with that motor separate thereby interrupting power to the motor in question. This interruption of power is detected by the controller  34  which then energizes the indicator  42  to indicate the high temperature condition. Full operating current is not reapplied to the motor  26  or  28  in question until two conditions are met. The first is that the motor  26  or  28  has cooled sufficiently so that the contacts of the bimetallic switch  44  or  46  again engage. This alone is, however, not sufficient to reestablish the full current supply to the motor. In addition the operator must engage the restart actuator  40  and close the circuit or lead lines  43  leading to the controller  34 .  
         [0031]     While a restart actuator  40  is illustrated in the  FIG. 2  and  3  embodiments, it should be appreciated that other structures could be substituted for the restart actuator. For example, a position sensor could be provided in the circuit  43  in place of the restart actuator. The controller  34 , operating in response to the position sensor, in the form of, for example, an accelerometer or a mercury switch could prevent the re-energization of the motor  26  or  28  unless the vacuum cleaner  10  is returned to and oriented in a proper starting position. Such a position could, for example, be the storage position with the canister or handle assembly  14  in the upright position relative to the nozzle assembly  16  as illustrated in  FIG. 1 . In this situation if the vacuum cleaner  10  is in any other position, such as, for example, lying down on the floor, the controller  34  will prevent restarting of the motor even if the motor has cooled below the predetermined temperature.  
         [0032]     In still another alternative embodiment the restart actuator  40  could be simply deleted from the circuit. In this situation restarting of the motor  26  or  28  would be possible only after the controller  34  has been de-energized by switching off the vacuum cleaner and/or disconnection of the vacuum cleaner from a power source: that is, unplugging the vacuum cleaner from a utility power outlet.  
         [0033]     The foregoing description of several alternative embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings.  
         [0034]     For example, while an upright vacuum cleaner  10  has been illustrated in the drawing figures, the invention is equally applicable to other types of vacuum cleaners such as canister vacuum cleaners and handheld vacuum cleaners. Further, it is also applicable to battery powered vacuum cleaners of any type. In addition, the device is applicable to any form of vacuum cleaner whether it includes no agitators or more than one agitator, whether it is cyclonic or non-cyclonic design and whether it is a clean or dirty air system. Similarly, it applies to vacuum cleaners where the rotary agitator is driven by the suction generator motor or by its own, separate motor.  
         [0035]     Still further, the present invention is also not limited to utilization in vacuum cleaners. It is also equally applicable to other electrical devices and appliances equipped with electric motors and for which overheating is a concern.  
         [0036]     The embodiments were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled. The drawings and preferred embodiment do not and are not intended to limit the ordinary meaning of the claims and their fair and broad interpretation in any way.