Patent Publication Number: US-7909273-B2

Title: Shredder with gas detection system

Description:
FIELD 
     This application generally relates to shredders for destroying articles, such as paper documents, compact disks, etc, and in particular, having a gas detecting system. 
     BACKGROUND 
     Shredders are well-known devices for destroying articles, such as documents, CDs, floppy disks, etc. Further, users purchase shredders to destroy sensitive articles, such as credit card statements with account information, documents containing company trade secrets, etc. 
     Contrary to warnings labels and instruction manuals, some users spray aerosols, such as WD-40® spray, into the cutting mechanism to lubricate the cutters. In addition, users may spray compressed gas into the shredder to remove debris from the cutters or optical sensor. However, the propellants and/or solvents in many aerosols and sprays may include combustible or flammable gases (or volatile compounds) which could be ignited by the normal electrical activity of the paper shredder. This poses a safety hazard for the user and may cause damage to the shredder. 
     SUMMARY 
     According to one embodiment, a shredder is provided comprising: a housing including a shredder mechanism configured to shred an article, the shredder mechanism comprising an electrically powered motor; a combustible gas detection system positioned inside the housing and configured to detect a combustible gas within the housing; and a controller coupled to the combustible detection system and configured to deactivate the motor of the shredder mechanism in response to the combustible gas detection system detecting the combustible gas within the housing. 
     According to another embodiment, a method for shredding is provided comprising: shredding an article using a shredder mechanism having an electrically powered motor; detecting, with a gas sensor, a combustible gas in the vicinity of the shredder mechanism; and deactivating the motor of the shredder mechanism upon detecting the combustible gas. 
     Other features of one or more embodiments of this disclosure will seem apparent from the following detailed description, and accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure will now be disclosed, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, in which: 
         FIG. 1  shows an exploded view of a shredder constructed in accordance with an embodiment; 
         FIG. 2  shows a cross-sectional view of the top portion of the shredder shown in  FIG. 1 ; 
         FIG. 3  shows an exemplary gas detection system architecture, in accordance with an embodiment; 
         FIG. 4  shows an exemplary circuit schematic of a gas detection system for a shredder, in accordance with an embodiment. 
         FIG. 5  shows another exemplary circuit schematic of a gas detection system for a shredder, in accordance with an embodiment; and 
         FIG. 6  shows yet another exemplary circuit schematic of a gas detection system for a shredder, in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one aspect of the application, a shredder including a gas detection system may be provided. The gas detection system may include one or more sensors placed inside the housing of the shredder to detect the presence of gas, and in particular, flammable and/or combustible gases. If a gas is sprayed into the shredder, the sensor(s) will detect the gas and the shredder motor may be deactivated. In addition, a fan may also be activated to exhaust gas from the housing and/or to draw in ambient air to dilute gas within the housing. Further, an indicator may be provided to alert the user that the sensor has detected a gas. For example, a visible indication and/or audible sound may be generated to alert to the user that the sensor has detected a flammable or combustible gas. 
     For the purposes of this application, the term “gas” includes, not only conventional gases, but also aerosols (i.e., aerosolized liquids or solids suspended in air or another gas), sprays, mists, vapors, fumes, and other volatile compounds. This is because these substances behave more like a gas in terms of flow and distribution within a shredder. 
       FIG. 1  shows an exploded view of a shredder constructed in accordance with an embodiment. The shredder is generally indicated at  10 . The shredder includes a housing  20  having a throat  22  for receiving at least one article to be shredded, a shredder mechanism  17  received in the housing  20 . The shredder mechanism  17  includes the motor  13  and cutter elements. The shredder mechanism  17  enables the at least one article to be shredded to be fed into the cutter elements. The motor  13  is operable to drive the cutter elements so that the cutter elements shred the articles fed therein. 
     The shredder  10  includes a bottom receptacle  14  having a bottom wall, four side walls and an open top. The bottom receptacle  14  may be molded from a plastic material or any other material. The bottom receptacle  14  sits atop the upper periphery of the bottom housing  16  in a nested relation using flange portions of the bottom receptacle  14  that generally extend outwardly from the side walls thereof. The shredder mechanism  17  along with the motor  13  are configured to be received in the bottom receptacle  14  of the shredder housing  20 . The bottom receptacle  14  may be affixed to the underside of the top cover or wall  11  by fasteners. The receptacle  14  has an opening in its bottom wall through which the shredder mechanism  17  discharges shredded articles into the container  15 . 
     As noted above, the shredder  10  includes the shredder mechanism  17  that includes the electrically powered motor  13  and a plurality of cutter elements. The term “shredder mechanism,” as used herein, is a generic structural term to denote a device that destroys articles using at least one cutter element. Such destroying may be done in any particular way. For example, the shredder mechanism may include at least one cutter element that is configured to punch a plurality of holes in the document or article in a manner that destroys the document or article. In addition, the term “shredder mechanism” is not intended to be limited to devices that literally “shred” documents and articles, but is instead intended to cover any device that destroys documents and articles in a manner that leaves each document or article illegible and/or useless. In the illustrated embodiment, the cutter elements are generally mounted on a pair of parallel rotating shafts. The motor  13  operates using electrical power to rotatably drive the shafts and the cutter elements through a conventional transmission so that the cutter elements shred articles fed therein. The shredder mechanism  17  may also include a sub-frame for mounting the shafts, the motor  13 , and the transmission. The operation and construction of such a shredder mechanism  17  are well known and need not be described herein in detail. Generally, any suitable shredder mechanism  17  known in the art or developed hereafter may be used. 
     In the illustrated embodiment, the shredder  10  may sit atop the large freestanding housing  16 , which may be formed of molded plastic material or any other material. The housing  16  includes a bottom wall, three side walls, an open front and an open top. The side walls of the container  16  provide a seat on which the shredder housing  20  is removably mounted. The housing  16  may be constructed and arranged to receive the waste container  15  therein. In other words, the waste container  15  is enclosed in the housing  16 . The waste container  15  is formed of molded plastic material or any other material. The waste container  15  is in the form of a pull-out bin that is constructed and arranged to slide in and out of the housing  16  through an opening in the front side thereof. The waste container  15  includes a handle  19  that may be configured to allow a user to grasp and pull out the waste container  15  from the housing  16 . In the illustrated embodiment, the handle  19  is located on the front, side wall of the waste container  15 . Any construction or configuration for the housing or waste container  15  may be used, and the illustrated embodiment is not limiting. 
     As an option, the housing  16 , along with the shredder  10 , may be transported from one place to another by simply rolling the housing  16  on roller members  24 , such as wheels or casters. In the illustrated embodiment, the housing  16  includes two pairs of roller members  24  attached to the bottom of the frame of the housing  16  to support the housing  16 . The rolling members  24  can be located on the housing  16  as near the corners as practical. The roller members  24 , in one embodiment, may be locked against rolling motion by lock members to provide a stationary configuration. In one embodiment, the front pair of the roller members  24  may be casters that provide a turning capability to the housing  16 , while the rear pair of the roller members  24  may be wheels that are fixed in direction, so as to only allow roll in the intended direction of travel. 
     The cover  11  may include a switch  12  recessed with an opening therethrough. For example, an on/off switch  12  that includes a switch module may be mounted to the top cover  11  underneath the switch recess by fasteners, and a manually engageable portion that moves laterally within the switch recess. The switch module has a movable element that connects to the manually engageable portion through the opening. This enables movement of the manually engageable portion to move the switch module between its states. 
     The switch module  12  is configured to connect the motor  13  to the power supply. This connection may be direct or indirect, such as via a controller. Typically, the power supply will be a standard power cord with a plug on its end that plugs into a standard alternating current (AC) outlet. The switch  12  may be movable between an “on” position and an “off” position by moving the manually engageable portion laterally within the switch recess. In the “on” position, contacts in the switch module are closed by movement of the manually engageable portion and the movable element to enable a delivery of electrical power to the motor  13 . In the “off” position, contacts in the switch module are opened to disable the delivery of electric power to the motor  13 . Alternatively, the switch  12  may be coupled to a controller, which in turn controls a relay switch, for controlling the flow of electricity to the motor  13 . As an option, the switch  12  may also have a reverse position wherein contacts are closed to enable delivery of electrical power to operate the motor  13  in a reverse manner. 
     A thickness detector  21  may also be provided that is configured to detect a thickness of the at least one article received by the throat  22 . The controller, for example, may be configured to vary the running operation of the motor responsive to the detector detecting the thickness of the at least one article being received by the throat  22 . Exemplary thickness detectors are disclosed, for example, in U.S. Patent Application Publication No. 2007/0246585. 
     According to an aspect of the application, the shredder  10  is provided with a gas detection system. The gas detection system may include a gas detection sensor  32  which is configured to detect a gas within the housing  20 . In addition or alternatively, one or more temperature sensors  34  may be provided which are configured to detect a rapid change in temperature of a aerosol spray. 
     If an aerosol (or other gas) is sprayed into the shredder, the sensor(s) will detect the aerosol gas and the shredder motor  13  may be disabled or deactivated. In addition, the exhaust fan  36  may also be activated to remove the aerosol gas from the housing and/or drawn in ambient air to dilute the gas within the housing. 
     One or more indicators  18  may provide status to the user of one or features of the shedder, including providing a visible and/or audible alert to the user that the sensor has detected a gas. For example, the display indicators  18  may include one or light emitting diodes (LED), liquid crystal display (LCD), speaker, beeper, gauge, lamp, or other indicating means. Additional information may be provided to the user, such as the gas detected, concentration, action taken, and/or further instructions. 
       FIG. 2  shows a cross-sectional view of the top portion of shredder  10  shown in  FIG. 1 . The gas detection sensor  32  may be, for example, mounted adjacent to the motor  13 . This configuration may help prevent detect gases which could be ignited if the motor  12  were to be switched on. Other locations for the gas detection sensor  32  and temperature sensors  34  are also envisioned in which the presence of gases could be ignited by the electrical activity of the paper shredder (e.g., commutators, switches, relays, exposed contact points, etc.). 
       FIG. 3  shows an exemplary gas detector system architecture  30  in accordance, with an embodiment. 
     The gas detection system architecture  30  may include a gas detection sensor  32 . The gas detection sensor  32  may be configured to detect gases, and in particular, flammable and/or combustible gases. For example, detected gases may include, but are not necessarily limited to: hydrocarbons (such as propane, n-butane, iso-butane, etc.), chlorofluorocarbons (CFCs), dimethyl ether, methyl ethyl ether, nitrous oxide, diflourethane, and carbon dioxide. The gas detection sensor  32  may also be configured to detect volatile compounds, including solvents. 
     It will be appreciated that the gas detection sensor  32  may use various gas detection sensor technologies, such as, for example, solid state. pellistor, catalyst, and ionization. In one implementation, the gas detection sensor  32  may be a model TGS 832 manufactured by Figaro USA Inc. The gas detection sensor  32  could also be a model CH-D3 manufactured by Alphasense Ltd. (UK) 
     Multiple gas detection sensors  32  might be positioned at different locations in the shredder  10  and/or configured for detecting different gases. 
     In addition or as an alternative to the gas detection sensor  32 , one or more temperature sensors  34  may be provided for detecting a gas. Typically, gases are stored are under great pressure in their containers. When sprayed, there may be a rapid temperature change due to the expansion of the gas. The temperature sensor  34 , thus may be configured to detect a temperature change associated with the expanding gas. 
     In one implementation, the temperature sensor(s)  34  may be a model LM35CZ manufactured by National Semiconductor Corporation. This is a linear output temperature sensor. In addition to solid state sensors, thermistors could be used (i.e., a resistor whose properties change with temperature). One example of a thermistor that may be used is Part Number 103JG1J manufactured by US Sensor Corp. 
     The temperature sensors  34  may be provided at various location in the shredder housing  20  where a gas is likely to be sprayed (e.g., throat, vents, particle exit, etc.). If desired, one or more temperature sensors  34  may be placed inside the housing  20  away from any openings. 
     A gas detector controller  38  may also be provide for processing the signals generated from the gas sensor  32  and/or the temperature sensor(s)  34 , and controlling various aspects of the shedder. The gas detector controller  38  may include an electrical circuit, integrated circuit, discrete circuit, microprocessor, and/or software (firmware). 
     The controller  38  may be connected to the shredder motor  13 , one or more indicators  18 , and exhaust fan  36 . Based on the feedback from the sensors, the controller  38  may disable the shredder motor  13  and/or enable the exhaust fan  36 . Alternatively or additionally, the indicator  18  may be activated. 
       FIG. 1 , for example, shows the shredder  10  having two temperature sensors  34 . This configuration allows the temperature changes in the shredder  10  to be monitored by the two temperature sensors  34 . In one implementation, if a sudden change is detected by one temperature sensor  34 , the motor  13  may be deactivated for a predetermined amount of time while the exhaust fan  36  is activated. 
     In some embodiments, the controller  38  may be capable of not only detecting a gas, but determining the particular gas (or gases) detected, and its concentration. Depending on the gas and concentration, different alerts, and/or exhausting procedures may be implemented. 
     In addition, the controller  38  may include a memory device  39  to collect and store metric data for investigative purposes. For example, the stored information, may include, the number of times each sensor was activated, the particular gases that were detected, concentrations, time to exhaust, and/or alert actions taken. The user may be able to use the indicator  18  to view the metric data stored in the memory device  39 . In addition, the metric data may be retrieved by service personnel. 
     The controller  38  may in some embodiments may be integrated with other functionalities of the shredder, although it will be appreciated that the controller  38  may be stand alone. 
       FIG. 4  shows an exemplary circuit schematic  40  for a gas detection system for a shredder, in accordance with an embodiment of the application. 
     The output of the gas detection sensor circuit  41  may be provided to an optional amplifier stage  42  to increase the gain of the voltage output of the gas detection sensor. The output signal may then be provided to a comparator stage  44 . The comparator stage  44  compares the output voltage of the sensor (or amplified voltage) to a threshold voltage. The threshold voltage may be set so as to distinguish the gas detected from mere noise. A potentiometer, for example, may be provided in the comparator stage  44  for manual adjustment of the voltage. 
     If the output voltage is greater than the threshold voltage, a relay circuit  46  may be switched which cuts off current to the shredder motor circuit  47 . Thus, even if the user attempts to operate the shredder (including turning the power switch  12  to the “on” position), the shredder mechanism will simply not operate. In addition, the relay switches current flow through a light emitting diode (LED) indicator circuit  48  to indicate the presence of a gas to the user. Further alerts may indicate to the user that a dangerous condition may be present. 
     When the output of the gas detection sensor circuit  41  falls below the threshold voltage, the relay circuit  46  may be switched to permit current to flow to the shredder motor circuit  47 , rather than the LED indicator  48 . As such, the user may again be able to operate the shredder. 
       FIG. 5  shows another exemplary circuit schematic  50  for the gas detection control system for a shredder, in accordance with an embodiment. 
     This circuit  50  may be similar to the circuit  40  shown in  FIG. 4 , with the addition of an exhaust fan circuit  49 . The exhaust fan circuit  49  may be energized to operate when the motor circuit  47  is deactivated. The exhaust fan circuit  49  may purge or quickly remove the aerosol gas from within the housing of the shredder assembly. In some implementations, the fan might also draw ambient air into the shredder housing to reduce/dilute the concentration of gas therein. 
       FIG. 6  shows yet another an exemplary circuit schematic  60  for the gas detection control system for a shredder, in accordance with an embodiment. 
     This circuit  60  includes a gas detection sensor circuit  41 , two temperature sensor circuits  61 , a microprocessor  62 , an exhaust fan circuit  69   36 , indicator circuit  68 , and a shredder motor circuit  47 . The microprocessor may be an 8051 based core or ARM core processor. In one implementation, the microprocessor may be a model CY8C21534 manufactured by Cypress Semiconductor Corp. 
     The microcontroller  62  receives signals from the gas detection sensor circuit  41  and/or the temperature sensor circuits  61  for analysis. The microcontroller  62  may be configured to determine one or more particular gases, and concentrations. 
     Based on the feedback from the sensors, the microcontroller  62  may deactivate the shredder motor circuit  47 . For example, output from the microcontroller  62  may be feed to a switch circuit  66  (such as a Triac) to control current to the shredder motor circuit  47 . Other solid-state switching circuits and mechanisms may similarly be used. 
     The microcontroller  62  may individually control the motor circuit  47 , the exhaust fan circuit  69  and the indicator circuit  68  In one implementation, the indicator circuit  68  may include a beeper (or speaker) for emitting an audible signal, in additional to a LED. Other types of indicators are also possible. 
     The above embodiments are primarily directed to shredders. However, the gas sensing systems disclosed herein may also be adapted for various other applications which have electrically powered motors (e.g., brushed DC motors or universal motors) or heat sources, in which there may be a potential for flash events. This may include most power tools (such as saws and drills), binding and laminating machines, household appliances, vacuum cleaners, hair dryers, etc. Other applications may also be benefited. 
     While this disclosure has been described in connection with what is presently considered to be the most practical embodiment, it is to be understood that it is capable of further modifications and is not to be limited to the disclosed embodiment, and this application is intended to cover any variations, uses, equivalent arrangements or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice in the art to which the disclosure pertains, and as may be applied to the essential features hereinbefore set forth and followed in the spirit and scope of the appended claims.