Abstract:
A shredder includes a thickness detector device having a contact portion in a throat of a housing. The contact portion is movable by a thickness between opposing major surfaces of at least one article being received by the throat. The thickness detector device includes a detectable portion movable by the contact portion, and a detector for detecting at least one position of the detectable portion that includes a position when the detectable portion has been moved by the contact portion by an amount that correlates to a predetermined maximum thickness. A controller is coupled to the thickness detector, is operable to prevent a motor from driving cutter elements in a shredding direction responsive to the detector detecting that the detectable portion has been moved by the amount that correlates to the predetermined maximum thickness, and is configured to vary the predetermined maximum thickness based on receiving an input parameter.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is continuation of U.S. patent application Ser. no. 11/767,152, filed Jun. 22, 2007 and currently pending, which is a divisional application of U.S. patent application Ser. No. 11/444,491, filed Jun. 1, 2006 and currently pending, which is a continuation-in-part of U.S. patent application Ser. No. 11/177,480, filed Jul. 11, 2005 and currently pending, which in turn is a continuation-in-part of U.S. patent application Ser. No. 10/937,304, filed on Sep. 10, 2004 and issued on Dec. 25, 2007 as U.S. Pat. No. 7,311,276, the entire contents of which are all incorporated herein by reference. U.S. patent application Ser. No. 11/444,491, filed Jun. 1, 2006 and currently pending is also a continuation-in-part of U.S. patent application Ser. No. 11/385,864, filed on Mar. 22, 2006 and currently pending, the entire content of which is also incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to shredders for destroying articles, such as documents, compact discs, etc. 
         [0004]    2. Description of Related Art 
         [0005]    Shredders are well known devices for destroying articles, such as documents, compact discs (“CDs”), expired credit cards, etc. Typically, users purchase shredders to destroy sensitive articles, such as credit card statements with account information, documents containing company trade secrets, etc. 
         [0006]    A common type of shredder has a shredder mechanism contained within a housing that is removably mounted atop a container. The shredder mechanism typically has a series of cutter elements that shred articles fed therein and discharge the shredded articles downwardly into the container. The shredder typically has a stated capacity, such as the number of sheets of paper (typically of 20 lb. weight) that may be shredded at one time; however, the feed throat of a typical shredder can receive more sheets of paper than the stated capacity. A common frustration of users of shredders is to feed too many papers into the feed throat, only to have the shredder jam after it has started to shred the papers. To free the shredder of the papers, the user typically reverses the direction of rotation of the cutter elements via a switch until the papers become free. 
         [0007]    In addition, shredders that are subjected to a lot of use should have periodic maintenance done to them. For example, the cutter elements may become dull over time. It has been found that lubricating the cutter elements may improve the performance of cutter elements, particularly if the shredder is used constantly over a long period of time. 
         [0008]    The present invention endeavors to provide various improvements over known shredders. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    It is an aspect of the invention to provide a shredder that does not jam as a result of too many papers, or an article that is too thick, being fed into the shredder. 
         [0010]    In an embodiment, a shredder is provided. The shredder includes a housing having a throat open to an exterior of the housing for permitting a user to feed at least one article to be shredded, and a shredder mechanism received in the housing and including an electrically powered motor and cutter elements. The shredder mechanism enables the at least one article fed into the throat to be shredded to be fed into the cutter elements and the motor is operable to drive the cutter elements in a shredding direction so that the cutter elements shred the articles fed therein. The shredder includes a thickness detector device that includes a contact portion in the throat, the contact portion being movable by a thickness between opposing major surfaces of the at least one article being received by the throat, a detectable portion movable by the contact portion, and a detector for detecting at least one position of the detectable portion. The at least one position of the detectable portion includes a position when the detectable portion has been moved by the contact portion by an amount that correlates to a predetermined maximum thickness. The shredder includes a controller coupled to the thickness detector. The controller is operable to prevent the motor from driving the cutter elements in the shredding direction responsive to the detector detecting that the detectable portion has been moved by the amount that correlates to the predetermined maximum thickness. The controller is configured to vary the predetermined maximum thickness based on receiving an input parameter. 
         [0011]    In an embodiment, there is provided a method of operating a shredder that includes: (a) a housing having a throat open to an exterior of the housing for permitting a user to feed at least one article to be shredded; (b) a shredder mechanism received in the housing and including an electrically powered motor and cutter elements, the shredder mechanism enabling the at least one article fed into the throat to be shredded to be fed into the cutter elements and the motor being operable to drive the cutter elements in a shredding direction so that the cutter elements shred the articles fed therein; (c) a thickness detector device comprising (i) a contact portion in the throat, the contact portion being movable by a thickness between opposing major surfaces of the at least one article being received by the throat, (ii) a detectable portion movable by the contact portion, and (iii) a detector for detecting at least one position of the detectable portion, the at least one position of the detectable portion including a position when the detectable portion has been moved by the contact portion by an amount that correlates to a predetermined maximum thickness; and (d) a controller coupled to the thickness detector; wherein the controller is operable to prevent the motor from driving the cutter elements in the shredding direction responsive to the detector detecting that the detectable portion has been moved by the amount that correlates to the predetermined maximum thickness; and wherein the controller is configured to vary the predetermined maximum thickness based on receiving an input parameter. The method includes the controller receiving the input parameter and varying the predetermined maximum thickness; detecting with the detector when the detectable portion has moved the amount that correlates to the predetermined maximum thickness; and the controller preventing the motor from driving the cutter elements in the shredding direction responsive to the detector detecting when the detectable portion has moved the amount that correlates to the predetermined maximum thickness. 
         [0012]    In an embodiment, there is provided a shredder that includes a housing having a throat open to an exterior of the housing for permitting a user to feed at least one article to be shredded, and a shredder mechanism received in the housing and including an electrically powered motor and cutter elements. The shredder mechanism enables the at least one article fed into the throat to be shredded to be fed into the cutter elements and the motor being operable to drive the cutter elements in a shredding direction so that the cutter elements shred the articles fed therein. A thickness detector device is configured to detect a thickness between opposing major surfaces of the at least one article being received by the throat. The thickness detector device includes a first portion in the throat, a second portion that is configured to rotate upon movement of the first portion, and an optical detector configured to detect a position of the second portion. The shredder includes a controller coupled to the thickness detector device. The optical detector is configured to detect at least one position of the second portion and to communicate such detection to the controller, the at least one position including a position when the thickness of the at least one article is at least equal to a predetermined maximum thickness. The controller is operable to prevent the motor from driving the cutter elements in the shredding direction responsive to the detector detecting that the thickness of the at least one article is at least equal to the predetermined maximum thickness. The controller is configured to vary the predetermined maximum thickness based on receiving an input parameter. 
         [0013]    Other aspects, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a shredder constructed in accordance with an embodiment of the present invention; 
           [0015]      FIG. 2  is an exploded perspective view of the shredder of  FIG. 1 ; 
           [0016]      FIG. 3  is a schematic illustration of an oiling mechanism in accordance with an embodiment of the present invention; 
           [0017]      FIG. 4  is a perspective view of a shredder having an oiling mechanism in accordance with an embodiment of the present invention; 
           [0018]      FIG. 5  is a perspective view of a shredder having an oiling mechanism in accordance with an embodiment of the present invention; 
           [0019]      FIG. 6  is a schematic of interaction between a controller and other parts of the shredder; 
           [0020]      FIG. 7  is a schematic of an embodiment of an indicator located on the shredder; 
           [0021]      FIG. 8  is a schematic of an embodiment of a detector configured to detect a thickness of a article to be shredded by the shredder; 
           [0022]      FIG. 9  is a schematic of another embodiment of a detector configured to detect a thickness of a article to be shredded by the shredder; 
           [0023]      FIG. 10  is a schematic of another embodiment of a detector configured to detect a thickness of a article to be shredded by the shredder; 
           [0024]      FIG. 11  is a schematic of another embodiment of the detector of  FIG. 10 ; and 
           [0025]      FIG. 12  is a flow diagram of an embodiment of a method for shredding an article. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]      FIGS. 1 and 2  illustrate a shredder constructed in accordance with an embodiment of the present invention. The shredder is generally indicated at  10 . In the illustrated embodiment, the shredder  10  sits atop a waste container, generally indicated at  12 , which is formed of molded plastic or any other material. The shredder  10  illustrated is designed specifically for use with the container  12 , as the shredder housing  14  sits on the upper periphery of the waste container  12  in a nested relation. However, the shredder  10  may also be designed so as to sit atop a wide variety of standard waste containers, and the shredder  10  would not be sold with the container. Likewise, the shredder  10  could be part of a large freestanding housing, and a waste container would be enclosed in the housing. An access door would provide for access to and removal of the container. Generally speaking, the shredder  10  may have any suitable construction or configuration and the illustrated embodiment is not intended to be limiting in any way. In addition, the term “shredder” 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. 
         [0027]    As shown in  FIG. 2 , in an embodiment, the shredder  10  includes a shredder mechanism  16  that includes an electrically powered motor  18  and a plurality of cutter elements  19 . “Shredder mechanism” 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 the illustrated embodiment, the cutter elements  19  are generally mounted on a pair of parallel rotating shafts  20 . The motor  18  operates using electrical power to rotatably drive the shafts and the cutter elements through a conventional transmission  23  so that the cutter elements shred articles fed therein. The shredder mechanism  16  may also include a sub-frame  21  for mounting the shafts, the motor  18 , and the transmission  23 . The operation and construction of such a shredder mechanism  16  are well known and need not be described herein in detail. Generally, any suitable shredder mechanism  16  known in the art or developed hereafter may be used. 
         [0028]    The shredder  10  also includes the shredder housing  14 , mentioned above. The shredder housing  14  includes top wall  24  that sits atop the container  12 . The top wall  24  is molded from plastic and an opening  26  is located at a front portion thereof. The opening  26  is formed in part by a downwardly depending generally U-shaped member  28 . The U-shaped member  28  has a pair of spaced apart connector portions  27  on opposing sides thereof and a hand grip portion  28  extending between the connector portions  27  in spaced apart relation from the housing  14 . The opening  26  allows waste to be discarded into the container  12  without being passed through the shredder mechanism  16 , and the member  28  may act as a handle for carrying the shredder  10  separate from the container  12 . As an optional feature, this opening  26  may be provided with a lid, such as a pivoting lid, that opens and closes the opening  26 . However, this opening in general is optional and may be omitted entirely. Moreover, the shredder housing  14  and its top wall  24  may have any suitable construction or configuration. 
         [0029]    The shredder housing  14  also includes a bottom receptacle  30  having a bottom wall, four side walls and an open top. The shredder mechanism  16  is received therein, and the receptacle  30  is affixed to the underside of the top wall  24  by fasteners. The receptacle  30  has an opening  32  in its bottom wall through which the shredder mechanism  16  discharges shredded articles into the container  12 . 
         [0030]    The top wall  24  has a generally laterally extending opening, which is often referred to as a throat  36 , extending generally parallel and above the cutter elements. The throat  36  enables the articles being shredded to be fed into the cutter elements. As can be appreciated, the throat  36  is relatively narrow, which is desirable for preventing overly thick items, such as large stacks of documents, from being fed into cutter elements, which could lead to jamming. The throat  36  may have any configuration. 
         [0031]    The top wall  24  also has a switch recess  38  with an opening therethrough. An on/off switch  42  includes a switch module (not shown) mounted to the top wall  24  underneath the recess  38  by fasteners, and a manually engageable portion  46  that moves laterally within the recess  38 . The switch module has a movable element (not shown) that connects to the manually engageable portion  46  through the opening. This enables movement of the manually engageable portion  46  to move the switch module between its states. 
         [0032]    In the illustrated embodiment, the switch module connects the motor  18  to the power supply. Typically, the power supply will be a standard power cord  44  with a plug  48  on its end that plugs into a standard AC outlet. The switch  42  is movable between an on position and an off position by moving the portion  46  laterally within the recess  38 . In the on position, contacts in the switch module are closed by movement of the manually engageable portion  46  and the movable element to enable a delivery of electrical power to the motor  18 . In the off position, contacts in the switch module are opened to disable the delivery of electric power to the motor  18 . 
         [0033]    As an option, the switch  42  may also have a reverse position wherein contacts are closed to enable delivery of electrical power to operate the motor  18  in a reverse manner. This would be done by using a reversible motor and applying a current that is of a reverse polarity relative to the on position. The capability to operate the motor  18  in a reversing manner is desirable to move the cutter elements in a reversing direction for clearing jams. In the illustrated embodiment, in the off position the manually engageable portion  46  and the movable element would be located generally in the center of the recess  38 , and the on and reverse positions would be on opposing lateral sides of the off position. 
         [0034]    Generally, the construction and operation of the switch  42  for controlling the motor  42  are well known and any construction for such a switch  42  may be used. 
         [0035]    In the illustrated embodiment, the top cover  24  also includes another recess  50  associated with an optional switch lock  52 . The switch lock  52  includes a manually engageable portion  54  that is movable by a user&#39;s hand and a locking portion (not shown). The manually engageable portion  54  is seated in the recess  50  and the locking portion is located beneath the top wall  24 . The locking portion is integrally formed as a plastic piece with the manually engageable portion  54  and extends beneath the top wall  24  via an opening formed in the recess  50 . 
         [0036]    The switch lock  52  causes the switch  42  to move from either its on position or reverse position to its off position by a caroming action as the switch lock  52  is moved from a releasing position to a locking position. In the releasing position, the locking portion is disengaged from the movable element of the switch  42 , thus enabling the switch  42  to be moved between its on, off, and reverse positions. In the locking position, the movable element of the switch  42  is restrained in its off position against movement to either its on or reverse position by the locking portion of the switch lock  52 . 
         [0037]    Preferably, but not necessarily, the manually engageable portion  54  of the switch lock  52  has an upwardly extending projection  56  for facilitating movement of the switch lock  52  between the locking and releasing positions. 
         [0038]    One advantage of the switch lock  52  is that, by holding the switch  42  in the off position, to activate the shredder mechanism  16  the switch lock  52  must first be moved to its releasing position, and then the switch  42  is moved to its on or reverse position. This reduces the likelihood of the shredder mechanism  16  being activated unintentionally. Reference may be made to U.S. Patent Application Publication No. 2005-0218250 A1, which is incorporated herein by reference, for further details of the switch lock  52 . This switch lock is an entirely optional feature and may be omitted. 
         [0039]    In the illustrated embodiment, the shredder housing  14  is designed specifically for use with the container  12  and it is intended to sell them together. The upper peripheral edge  60  of the container  12  defines an upwardly facing opening  62 , and provides a seat  61  on which the shredder  10  is removably mounted. The seat  61  includes a pair of pivot guides  64  provided on opposing lateral sides thereof. The pivot guides  64  include upwardly facing recesses  66  that are defined by walls extending laterally outwardly from the upper edge  60  of the container  12 . The walls defining the recesses  66  are molded integrally from plastic with the container  12 , but may be provided as separate structures and formed from any other material. At the bottom of each recess  66  is provided a step down or ledge providing a generally vertical engagement surface  68 . This step down or ledge is created by two sections of the recesses  66  being provided with different radii. Reference may be made to U.S. Pat. No. 7,025,293, which is incorporated herein by reference, for further details of the pivotal mounting. This pivotal mounting is entirely optional and may be omitted. 
         [0040]    As schematically illustrated in  FIG. 3 , in order to lubricate the cutter elements  19  of the shredder  10 , a lubrication system  80  may be included for providing lubrication at the cutter elements  19 . The system includes a pump  82 , that draws lubricating fluid, such as oil, from a reservoir  84 . In a typical application, the reservoir  84  will have a fill neck  86  that extends through the top wall  24  of the shredder housing  14  to allow for easy access for refilling the reservoir (see  FIG. 5 ). 
         [0041]    The pump  82  communicates through a series of conduits  88  to one or more nozzles  90  that are positioned proximate the cutter elements  19 . In one embodiment, the nozzles can be positioned such that oil forced through the nozzles is dispersed as sprayed droplets in the throat of the shredder  10 . In another embodiment, the oil is dispersed in back of the throat of the shredder  10 . Generally, the nozzles have openings small relative to the conduits, thereby creating a high speed flow at the nozzle, allowing the oil to be expelled at a predictable rate and pattern. 
         [0042]    As shown in  FIG. 4 , a system in accordance with an embodiment of the present invention may be a retrofit device. In this embodiment, the reservoir  84  is mounted to an outside surface of the shredder  10 . It is connected via a conduit  92  to the main unit  94 . The main unit  94  may include a power supply (not shown) and the pump  82  (not shown in  FIG. 4 ). In any embodiment, the reservoir  84  may be designed to be removed and replaced, rather than re-filled. 
         [0043]    An alternate embodiment includes the system  80  built into the housing of the shredder  10 . In this embodiment, shown in  FIG. 5 , the fill neck  86  can be designed to extend through the top wall  24  of the shredder housing  14 . Operation of the system  80  does not depend on whether it is retrofit or built-in. 
         [0044]    In operation, a controller  96  (shown in  FIG. 6 ) for the lubrication system  80  is programmed with instructions for determining when to lubricate the cutter elements  19 . The controller processes the instructions and subsequently applies them by activating the pump  82  to cause fluid from the reservoir to be delivered to the nozzles  90  under pressure. The nozzles are positioned and arranged to spray the pressurized lubricating oil to the cutter elements  19 . In general, the oil will be dispersed in a predetermined pattern directly onto the cutter elements and/or the strippers. In a particular arrangement, it may be useful to array the nozzles below the cutter elements so that lubrication is sprayed from below. In an alternate embodiment, the oil is sprayed onto an intermediate surface  98  (shown in  FIG. 3 ) and allowed to drip from there onto the cutter elements  19  and the strippers (which are generally located on the outward or post-cutting side of the cutting mechanism and include a serrated member or a comb type member having teeth that protrude into the spaces between the individual cutting disks). The illustrated embodiments of the lubrication system  80  are not intended to be limiting in any way. Reference may be made to U.S. patent application Ser. No. 11/385,864, which is hereby incorporated by reference, for further details of an oiling mechanism. The lubrication system  80  is an optional feature of the shredder  10 . 
         [0045]    In an embodiment of the invention, the shredder  10  includes a thickness detector  100  to, detect overly thick stacks of documents or other articles that could jam the shredder mechanism  16 , and communicate such detection to a controller  200 , as shown in  FIG. 6 . Upon such detection, the controller  200  may communicate with an indicator  110  that provides a warning signal to the user, such as an audible signal and/or a visual signal. Examples of audible signals include, but are not limited to beeping, buzzing, and/or any other type of signal that will alert the user that the stack of documents or other article that is about to be shredded is above a predetermined maximum thickness and may cause the shredder mechanism  16  to jam. This gives the user the opportunity to reduce the thickness of the stack of documents or reconsider forcing the thick article through the shredder, knowing that any such forcing may jam and/or damage the shredder. 
         [0046]    A visual signal may be provided in the form of a red warning light, which may be emitted from an LED. It is also contemplated that a green light may also be provided to indicate that the shredder  10  is ready to operate. In an embodiment, the indicator  110  is a progressive indication system that includes a series of indicators in the form of lights to indicate the thickness of the stack of documents or other article relative to the capacity of the shredder is provided, as illustrated in  FIG. 7 . As illustrated, the progressive indication system includes a green light  112 , a plurality of yellow lights  114 , and a red light  116 . The green light  112  indicates that the detected thickness of the item (e.g. a single paper, a stack of papers, a compact disc, a credit card, etc.) that has been placed in the throat  36  of the shredder  10  is below a first predetermined thickness and well within the capacity of the shredder. The yellow lights  114  provide a progressive indication of the thickness of the item. The first yellow light  114 , located next to the green light  112 , would be triggered when the detected thickness is at or above the first predetermined thickness, but below a second predetermined thickness that triggers the red light  116 . If there is more than one yellow light  114 , each additional yellow light  114  may correspond to thicknesses at or above a corresponding number of predetermined thicknesses between the first and second predetermined thicknesses. The yellow lights  114  may be used to train the user into getting a feel for how many documents should be shredded at one time. The red light  116  indicates that the detected thickness is at or above the second predetermined thickness, which may be the same as the predetermined maximum thickness, thereby warning the user that this thickness has been reached. 
         [0047]    The sequence of lights may be varied and their usage may vary. For example, they may be arranged linearly in a sequence as shown, or in other configurations (e.g. in a partial circle so that they appear like a fuel gauge or speedometer. Also, for example, the yellow light(s)  114  may be lit only for thickness(es) close to (i.e., within 25% of) the predetermined maximum thickness, which triggers the red light  116 . This is a useful sequence because of most people&#39;s familiarity with traffic lights. Likewise, a plurality of green lights (or any other color) could be used to progressively indicate the detected thickness within a range. Each light would be activated upon the detected thickness being equal to or greater than a corresponding predetermined thickness. A red (or other color) light may be used at the end of the sequence of lights to emphasize that the predetermined maximum thickness has been reached or exceeded (or other ways of getting the user&#39;s attention may be used, such as emitting an audible signal, flashing all of the lights in the sequence, etc.). These alert features may be used in lieu of or in conjunction with cutting off power to the shredder mechanism upon detecting that the predetermined maximum thickness has been reached or exceeded. 
         [0048]    Similarly, the aforementioned indicators of the progressive indicator system may be in the form of audible signals, rather than visual signals or lights. For example, like the yellow lights described above, audible signals may be used to provide a progressive indication of the thickness of the item. The audible signals may vary by number, frequency, pitch, and/or volume in such a way that provides the user with an indication of how close the detected thickness of the article is to the predetermined maximum thickness. For example, no signal or a single “beep” may be provided when the detected thickness is well below the predetermined maximum thickness, and a series of “beeps” that increase in number (e.g. more “beeps” the closer the detection is to the predetermined maximum thickness) and/or frequency (e.g. less time between beeps the closer the detection is to the predetermined maximum thickness) as the detected thickness approaches the predetermined maximum thickness may be provided. If the detected thickness is equal to or exceeds the predetermined maximum thickness, the series of “beeps” may be continuous, thereby indicating to the user that such a threshold has been met and that the thickness of the article to be shredded should be reduced. 
         [0049]    The visual and audible signals may be used together in a single device. Also, other ways of indicating progressive thicknesses of the items inserted in the throat  36  may be used. For example, an LCD screen with a bar graph that increases as the detected thickness increases may be used. Also, a “fuel gauge,” i.e., a dial with a pivoting needle moving progressively between zero and a maximum desired thickness, may also be used. As discussed above, with an audible signal, the number or frequency of the intermittent audible noises may increase along with the detected thickness. The invention is not limited to the indicators described herein, and other progressive (i.e., corresponding to multiple predetermined thickness levels) or binary (i.e., corresponding to a single predetermined thickness) indicators may be used. 
         [0050]    The aforementioned predetermined thicknesses may be determined as follows. First, because the actual maximum thickness that the shredder mechanism may handle will depend on the material that makes up the item to be shredded, the maximum thickness may correspond to the thickness of the toughest article expected to be inserted into the shredder, such as a compact disc, which is made from polycarbonate. If it is known that the shredder mechanism may only be able to handle one compact disc at a time, the predetermined maximum thickness may be set to the standard thickness of a compact disc (i.e., 1.2 mm). It is estimated that such a thickness would also correspond to about 12 sheets of 20 lb. paper. Second, a margin for error may also be factored in. For example in the example given, the predetermined maximum thickness may be set to a higher thickness, such as to 1.5 mm, which would allow for approximately an additional 3 sheets of paper to be safely inserted into the shredder (but not an additional compact disc). Of course, these examples are not intended to be limiting in any way. 
         [0051]    For shredders that include separate throats for receiving sheets of paper and compact discs and/or credit cards, a detector  100  may be provided to each of the throats and configured for different predetermined maximum thicknesses. For example, the same shredder mechanism may be able to handle one compact disc and 18 sheets of 20 lb. paper. Accordingly, the predetermined maximum thickness associated with the detector associated with the throat that is specifically designed to receive compact discs may be set to about 1.5 mm (0.3 mm above the standard thickness of a compact disc), while the predetermined maximum thickness associated with the detector associated with the throat that is specifically designed to receive sheets of paper may be set to about 1.8 mm. Of course, these examples are not intended to be limiting in any way and are only given to illustrate features of embodiments of the invention. 
         [0052]    Similarly, a selector switch may optionally be provided on the shredder to allow the user to indicate what type of material is about to be shredded, and, hence the appropriate predetermined maximum thickness for the detector. A given shredder mechanism may be able to handle different maximum thicknesses for different types of materials, and the use of this selector switch allows the controller to use a different predetermined thickness for the material selected. For example, there may be a setting for “paper,” “compact discs,” and/or “credit cards,” as these materials are known to have different cutting characteristics and are popular items to shred for security reasons. Again, based on the capacity of the shredder mechanism, the appropriate predetermined maximum thicknesses may be set based on the known thicknesses of the items to be shredded, whether it is the thickness of a single compact disc or credit card, or the thickness of a predetermined number of sheets of paper of a known weight, such as 20 lb. The selector switch is an optional feature, and the description thereof should not be considered to be limiting in any way. 
         [0053]    Returning to  FIG. 6 , in addition to the indicator  110  discussed above, the detector  100  may also be in communication with the motor  18  that powers the shredder mechanism  16  via the controller  200 . Specifically, the controller  200  may control whether power is provided to the motor  18  so that the shafts  20  may rotate the cutter elements  19  and shred the item. This way, if the thickness of the item to be shredded is detected to be greater than the capacity of the shredder mechanism  16 , power will not be provided to the shredder mechanism  16 , thereby making the shredder  10  temporarily inoperable. This not only protects the motor  18  from overload, it also provides an additional safety feature so that items that should not be placed in the shredder  10  are not able to pass through the shredder mechanism  16 , even though they may fit in the throat  36  of the shredder  10 . 
         [0054]      FIG. 8-11  show different embodiments of the detector  100  that may be used to detect the thickness of an article (e.g. a compact disc, credit card, stack of papers, etc.) that is placed in the throat  36  of the shredder. As shown in  FIG. 8 , the detector  100  may include a contact member  120  that is mounted so that it extends into the throat  36  at one side thereof. The contact member  120  may be pivotally mounted or it may be mounted within a slot so that it translates relative to the throat  36 . The contact member  120  is mounted so that as the item to be shredded is inserted into the throat  36 , the item engages the contact member  120  and causes the contact member  120  to be pushed out of the way of the item. As shown in  FIG. 8 , a strain gauge  122  is located on a side of the contact member  120  that is opposite the throat  36 . The strain gauge  122  is positioned so that it engages the contact member  120  and is able to measure the displacement of the contact member  120  relative to the throat  36 . Other displacement sensors may be used. The greater the displacement, the thicker the item being inserted into the throat  36 . The strain gauge  122  communicates this measurement to the controller  200  and the controller  200  determines whether the displacement measured by the strain gauge  122 , and hence thickness of the item, is greater than the predetermined maximum thickness, thereby indicating that the item that is being fed into the throat of the shredder  10  will cause the shredder mechanism  16  to jam. If the detected thickness is greater than the predetermined maximum thickness, the controller  200  may send a signal to the indicator  110 , as discussed above, and/or prevent power from powering the motor  18  to drive the shafts  20  and cutter elements  19 . This way, a jam may be prevented. Likewise, the measured displacement of the contact member  120  may be used by the controller  200  to output progressive amounts of thicknesses, as discussed above. Of course, different configurations of the strain gauge  122  and contact member  120  may be used. The illustrated embodiment is not intended to be limiting in any way. 
         [0055]    In another embodiment, illustrated in  FIG. 9 , the detector  100  includes the contact member  120  and a piezoelectric sensor  124 . In this embodiment, the contact member  120  is mounted such that it protrudes through one wall  126  of the throat and into the throat by a small amount, thereby creating a slightly narrower throat opening. A spring  128  may be used to bias the contact member  120  into the throat  36 . The narrower opening that is created by a tip  130  of the contact member  120  and a wall  132  opposite the spring  128  is less than the predetermined maximum thickness. Therefore, if an item that is too thick to be shredded enters the throat  36 , it will engage a top side  134  of the contact member  120 . Because the top side  134  of the contact member  120  is sloped, the contact member  120  will move against the bias of the spring  128  and into contact with the piezoelectric sensor  124 , thereby causing a voltage to be created within the piezoelectric sensor  124 . As the thickness of the item increases, the force applied by the contact member  120  to the piezoelectric sensor  124  increases, thereby increasing the voltage generated within the piezoelectric sensor  124 . The resulting voltage may be communicated to the controller  200  or directly to the indicator  110 , thereby causing the indicator  110  to indicate that the item is above the predetermined maximum thickness. In addition, the controller, upon sensing the voltage, may prevent power from powering the motor  18  to drive the shafts  20  and cutter elements  19 . Of course, different configurations of the piezoelectric sensor  124  and contact member  120  may be used. The illustrated embodiment is not intended to be limiting in any way. 
         [0056]    In another embodiment, illustrated in  FIG. 10 , the detector  100  includes the contact member  120  and an optical sensor  140 . In this embodiment, the contact member  120  is pivotally mounted such that one portion extends into the throat  36  and another portion, which has a plurality of rotation indicators  142 , extends away from the throat  36 . The optical sensor  140  may be configured to sense the rotation indicators  142  as the rotation indicators  142  rotate past the optical sensor  140 . For example, the optical sensor  140  may include an infrared LED  144  and a dual die infrared receiver  146  to detect the direction and amount of motion of the contact member  120 . As shown in  FIG. 7 , the contact member  120  may be configured such that a small amount of rotation of the contact member is amplified at the opposite end of the contact member  120 , thereby improving the sensor&#39;s ability to sense changes in the thickness of the items that cause the contact member  120  to rotate. Of course, different configurations of the optical sensor  140  and contact member  120  may be used. The illustrated embodiment is not intended to be limiting in any way. 
         [0057]    Another embodiment of the detector  100  that includes the optical sensor  140  is shown in  FIG. 11 . As illustrated in  FIG. 8 , the detector  100  is located above an infrared sensor  150  that detects the presence of an article. Of course, any such sensor may be used. The illustrated embodiment is not intended to be limiting in any way. The sensor  150  provides a signal to the controller  200 , which in turn is communicated to the motor  18 . When the sensor  150  senses that an article is passing through a lower portion of the throat  36 , the controller  200  signals the motor  18  to start turning the shafts  20  and cutter elements  19 . Of course, because the detector  100  is also in communication with the controller  200 , if the detector  100  detects that the thickness of the article that has entered the throat is too thick for the capacity of the shredder mechanism  16 , the shredder mechanism  16  may not operate, even though the sensor  150  has indicated that it is time for the shredder mechanism  16  to operate. Of course, this particular configuration is not intended to be limiting in any way. 
         [0058]    Although various illustrated embodiments herein employ particular sensors, it is to be noted that other approaches may be employed to detect the thickness of the stack of documents or article being fed into the throat  36  of the shredder  10 . For example, embodiments utilizing eddy current, inductive, photoelectric, ultrasonic, Hall effect, or even infrared proximity sensor technologies are also contemplated and are considered to be within the scope of the present invention. 
         [0059]    The sensors discussed above, and other possible sensors, may also be used to initiate the shredding operation by enabling the power to be delivered to the motor of the shredder mechanism. This use of sensors in the shredder throat is known, and they allow the shredder to remain idle until an item is inserted therein and contacts the sensor, which in turn enables power to operate the motor to rotate the cutting elements via the shafts. The controller  200  may be configured such that the insertion of an item will perform this function of enabling power delivery to operate the shredder mechanism motor. The motor may be cut-off or not even started if the thickness exceeds the predetermined maximum thickness. 
         [0060]    Returning to  FIG. 6 , for embodiments of the shredder  10  that include the lubrication system  80 , the controller  200  may be programmed to communicate with the controller  96  associated with the lubrication system  80  to operate the pump  82  in a number of different modes. The controller  200  and the controller  96  may be part of the same controller, or may be separate controllers that communicate with each another. In one embodiment, the controller  96  is programmed to operate according to a predetermined timing schedule. In another, the controller  96  activates the pump upon a certain number of rotations of the drive for the cutter elements. In another embodiment, the detector  100  at the throat  36  of the shredder  10  monitors the thickness of items deposited therein. Upon accumulation of a predetermined total thickness of material shredded, the controller  96  activates the pump to lubricate the cutter elements  19 . For example, if the predetermined total thickness of material is programmed in the controller  96  to be 0.1 m (100 mm), then once the total accumulated detected thickness of articles that have been shredder is at least equal to 0.1 m (e.g., one hundred articles with an average thickness of 1 mm, or fifty articles with an average thickness of 2 mm, etc.), the controller  96  will activate the pump  82  of the lubrication system  80  to lubricate the cutter elements  19 . 
         [0061]    It is also possible to schedule the lubrication based on a number of uses of the shredder (e.g., the controller tracks or counts the number of shredding operations and activates the pump after a predetermined number of shredder operations). In each of the embodiments making use of accumulated measures, a memory  97  can be incorporated for the purpose of tracking use. Although the memory  97  is illustrated as being part of the controller  96  associated with the lubrication system, the memory may be part of the shredder controller  200 , or may be located on some other part of the shredder  10 . The illustrated embodiment is not intended to be limiting in any way. 
         [0062]    In addition, the accumulated measures (e.g. the number of shredding operations or the accumulated thickness of the articles that have been shredded) may be used to alert the user that maintenance should be completed on the shredder. The alert may come in the form of a visual or audible signal, such as the signals discussed above, or the controller may prevent power from powering the shedder mechanism until the maintenance has been completed. 
         [0063]    The ability to keep track of the accumulated use of the shredder may also be helpful in a warranty context, where the warranty could be based on the actual use of the shredder, rather than time. This is similar to the warranties that are used with automobiles, such as “100,000 miles or 10 years, whichever comes first.” For example, the warranty may be based on 100 uses or one year, whichever comes first, or the warranty may be based on shredding paper having a total sensed thickness of 1 meter or 2 years, whichever comes first, and so on. 
         [0064]      FIG. 12  illustrates a method  300  for detecting the thickness of an item, e.g. a stack of documents or an article, being fed into the throat  36  of the shredder  10 . The method starts at  302 . At  304 , the item is fed into the throat  36  of the shredder  10 . At  306 , the detector  100  detects the thickness of the item. At  308 , the controller  200  determines whether the thickness that has been detected is greater than a predetermined maximum thickness. The predetermined maximum thickness may be based on the capacity of the shredder mechanism  16 , as discussed above. If the controller  200  determines that the thickness that has been detected is at least the predetermined maximum thickness, at  310 , a warning is provided. For example, to provide the warning, the controller  200  may cause the red light  116  to illuminate and/or causes an audible signal to sound and/or cause power to be disrupted to the motor  18  so that the shredder mechanism  16  will not shred the item. The user should then remove the item from the throat  36  of the shredder  10  at  312 , and reduce the thickness of the item at  314  before inserting the item back into the throat  36  at  304 . 
         [0065]    If the controller  200  determines that the thickness that has been detected is less than the predetermined maximum thickness, the controller  200  may cause the green light  112  to illuminate and/or allows power to be supplied to the shredder mechanism  16  so that the shredder  10  may proceed with shredding the item at  316 . 
         [0066]    In the embodiment that includes the plurality of yellow lights  114  as part of the indicator  100 , if the controller  200  determines that the thickness that has been detected is less than the predetermined maximum thickness, but close to or about the predetermined maximum thickness, the controller  200  may cause one of the yellow lights to illuminate, depending on how close to the predetermined maximum thickness the detected thickness is. For example, the different yellow lights may represent increments of about 0.1 mm so that if the detected thickness is within 0.1 mm of the predetermined maximum thickness, the yellow light  114  that is closest to the red light  116  illuminates, and so on. Although power will still be supplied to the shredder mechanism  16 , the user will be warned that that particular thickness is very close to the capacity limit of the shredder  10 . Of course, any increment of thickness may be used to cause a particular yellow light to illuminate. The example given should not be considered to be limiting in any way. 
         [0067]    Returning to the method  300  of  FIG. 9 , at  318 , the user may insert an additional item, such as another document or stack of documents, as the shredder mechanism  16  is shredding the previous item that was fed into the throat  36  of the shredder at  304 . If the user does insert an additional item into the throat  36  at  318 , the method returns to  304 , and the detector  100  detects the thickness of the item at the location of the detector  100  at  306 , and so on. If part of the previous item is still in the throat  36 , the cumulative thickness of the item being shredder and the new item may be detected. If the user does not add an additional item at  318 , the method ends at  320 . The illustrated method is not intended to be limiting in any way. 
         [0068]    The foregoing illustrated embodiments have been provided to illustrate the structural and functional principles of the present invention and are not intended to be limiting. To the contrary, the present invention is intended to encompass all modifications, alterations and substitutions within the spirit and scope of the appended claims.