Patent Publication Number: US-6222450-B1

Title: Metal detection device having improved support assembly

Description:
RELATED APPLICATIONS 
     This is related to U.S. Pat. No. 5,659,247 issued Aug. 19, 1997 and U.S. Pat. No. 5,576,621 issued Nov. 19, 1996, the contents of which are specifically incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to metal detection devices designed to detect the inadvertent disposal of metal articles into waste receptacles and, more particularly, to a metal detector designed to detect the inadvertent disposal of metal objects such as surgical instruments into disposal receptacles particularly useful in medical facilities and the like. Specifically, the present invention relates to a support assembly for the operating components of such a metal detection device. 
     2. Description of the Prior Art 
     One of the major problems in the health care industry today is the high cost of patient care. While many factors contribute to this cost, one of these factors is the difficulty in controlling waste in a hospital environment. In the operating room, surgical instruments are inadvertently but routinely discarded along with the disposable drapes and gowns after an operation. These expensive instruments are intended for reuse, and their disposal represents a substantial waste. In addition, theft of such instruments and small metallic objects also occurs through such disposal mechanisms. A survey of randomly selected hospitals revealed that such wasteful disposal and theft of surgical instruments amounted to losses between $30,000-$50,000 per year per operating room. In a typical hospital having six to ten operating rooms, such loss is substantial. 
     Moreover, used disposable surgical drapes and gowns, by law, are required to be deposited in a so-called “red bag” designated for infectious waste. Such red bags are approximately the size of a lawn and garden trash and leaf bag. The red bags are held for use in an open position in each operating room by a bag holder, typically in the form of a wheeled cart. Hospital personnel merely wad up used drapes and gowns and stuff them into the red bag for disposal. As can be readily appreciated, valuable surgical instruments, typically fashioned from an expensive grade of stainless steel, can easily become bundled with the used drapes and gowns, and disposed inadvertently or otherwise. 
     In penal institutions such as jails and prisons, prisoners are encouraged to participate in various jobs and vocational training programs including welding, mechanics and machining. Some inmates, consequently, have access to machine tools and metal stock materials from which they might fashion weapons. Receptacles for trash and laundry, although necessary in the daily operations of such penal institutions, create the potential for the smuggling by inmates of weapons and potential weapon stock material from shop and training areas to other locations. Accordingly, the monitoring and search of such receptacles place a substantial burden on guards, and thus increases the operating costs of these institutions. 
     Metal detectors of various types are well known in the art. U.S. Pat. No. 3,065,412 discloses a metal detector useful in its detection of metallic impurities in powders, while U.S. Pat. No. 4,821,023 discloses a walk-through metal detector useful at airports. Thus, metal detection devices have been applied in a wide variety of uses in the past. U.S. Pat. No. 4,632,253 and U.S. Pat. No. 4,782,970 disclose devices that are specifically designed to detect the inadvertent disposal of cutlery into a trash container in restaurant environments. Both these patent references disclose devices which are designed to cover trash containers, the first one of which utilizes an inductive probe to detect metal cutlery so as to close a flap to prevent its disposal into the trash container, while the latter reference discloses a magnetic arrangement which traps cutlery prior to being deposited into the receptacle. 
     U.S. Pat. No. 5,001,425 discloses a device designed to cover a receptacle for use in a hospital environment to detect the inadvertent disposal of metal articles in such a receptacle. As is pointed out therein, however, a significant problem in a hospital environment, and in particular surgical environments, is the presence of numerous metal objects surrounding the receptacle. Such metal objects proximate the detector can cause the inadvertent triggering of the detector alarm system without a metallic article having actually been placed therein due to false readings from metal articles immediately surrounding or near the top of such a receptacle. Thus, there is a need for a metal detector that is designed to detect the inadvertent disposal of small metal objects into a receptacle in a hospital, prison or kitchen environment, which is reliable and designed to prevent false signals from being registered due to the presence of metal articles on or near the top or exterior of such a receptacle without having been placed therein. The devices illustrated in the above-identified related U.S. Pat. No. 5,659,247 and U.S. Pat. No. 5,576,621 are designed to meet these needs. However, there remains a need to be able to mass produce such devices in a manner that is both economically viable as well as permits the accurate placement of the operational components of these devices, which placement is extremely important for the proper operation and long term use of the devices. The present invention satisfies this need. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is one object of the present invention to provide a device to detect the inadvertent disposal of surgical instruments and other small metal articles into a receptacle to allow for their retrieval and reuse. 
     It is another object of the present invention to provide a device to assist in the monitoring of receptacles to prevent the unauthorized deposit of metal articles therein to prevent theft or the undetected transfer of metal articles using such receptacles. 
     It is yet another object of the present invention to provide a metal detector for receptacles useful in surgical operating rooms or kitchen environments for the detection of inadvertent disposal of metal articles therein while preventing false alarms or signals resulting from metal material or articles on or near such receptacles. 
     Still another object of the present invention is to provide a metal detector for receptacles which is able to be mass produced in a manner that is both economically viable as well as permits the accurate placement and maintenance of the operational components of these devices. 
     Finally, it is another object of the present invention to provide a metal detector which is readily attachable and removable from wheeled receptacles and which includes a support structure which accurately positions the sensing elements of the device throughout the operational lifetime of the detector. 
     To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, a support assembly for a metal detection device is disclosed. The detection device includes a housing with a central orifice, an induction member surrounding the orifice for generating an output voltage when a metal object is passed nearby, and a mechanism which includes pulse emitting and pulse receiving members for selectively sensing an object passing through the orifice. The support assembly includes a base member having front, rear and opposed side portions sized and shaped for positioning beneath the housing. The base member has a central aperture adapted for substantial alignment with the housing orifice when the base member is positioned beneath the housing. A mechanism secures the base member to the housing, and a plurality of mounting posts are disposed along the base member front, rear and side portions for positioning a metal detection device induction member about the central aperture. A mounting mechanism is provided for the pulse emitting and pulse-receiving members on opposite sides of the central aperture. Finally, a plurality of pulse regulating elements are provided for eliminating ambient light interference and cross-pulse sensing in the pulse-receiving members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings which are incorporated in and form a part of the specification illustrate preferred embodiments of the present invention and, together with a description, serve to explain the principles of the invention. In the drawings: 
     FIG. 1 is a front perspective view of a metal detector constructed in accordance with the present invention; 
     FIG. 2 is a top plan view, with some parts in section, of the detector device illustrated in FIG. 1; 
     FIG. 3 is a cross-sectional view taken substantially along line  3 — 3  of FIG. 2; 
     FIG. 4 is cross-sectional view taken substantially along line  4 — 4  of FIG.  2  and illustrating placement of the device without the support assembly of the invention onto a receptacle support member; 
     FIG. 5 is a side perspective view of the detector device constructed in accordance with present invention mounted onto a portable receptacle member; 
     FIG. 6 is a side perspective view of the receptacle member illustrated in FIG. 5 without the receptacle bag and the detector device mounted thereon; 
     FIG. 7 is a top, frontal perspective view of the support assembly embodiment for a metal detector housing constructed in accordance with the present invention; 
     FIG. 8 is a top, rear perspective view of the support assembly embodiment of FIG. 7; 
     FIG. 9 is a bottom, frontal perspective view of the support assembly embodiment of FIG. 7; and 
     FIG. 10 is a bottom, rear perspective view of the support assembly embodiment of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and in particular to FIGS. 1-6, a metal detector device  10  is disclosed and includes a housing  12  having a front portion  14 , a rear portion  16  and two side portions  18  and  20 , all of which are interconnected by a top surface  22 . In preferred form, the housing  12  is substantially rectangular in shape and includes an exterior circumferential lip  24  that depends downwardly from the top surface  22  along the front and rear portions  14 ,  16  and the side portions  18 ,  20 . The lip  24  provides a surface for mounting the housing  12  to a receptacle structure  26  utilizing a support assembly as further described below. 
     The housing  12  is preferably constructed from any type of known non-metallic material and is most preferably constructed from molded plastic. In preferred form, the housing  12  is formed as an integral component in a rotational molding process wherein a powdered plastic resin material gradually melts within a heated, rotating mold. The liquefied resin then coats the interior surfaces of the mold to form the housing  12 . After cooling, the housing  12  is then removed from the mold. In the instant case, the mold is preferably configured to produce two component parts simultaneously which are severed after removal from the mold. A preferred plastic resin material is polypropylene, although a wide variety of other plastics or non-ferrous materials may also be employed. 
     The housing  12  preferably includes a central aperture or opening  30  which in preferred form is substantially square in shape. A plurality of inclined surfaces  32 ,  34 ,  36  and  38  depend angularly downwardly from the top surface  22  toward the aperture  30  and terminate at the respective edges  40 ,  42 ,  44  and  46 . A plurality of flanges  48 ,  50 ,  52  and  54  each extend vertically downwardly from their respective side edges  40 ,  42 ,  44  and  46  to form a substantially square tube portion  55  defining the aperture  30 . In use, the opening  30  overlies and communicates with a top opening of a waste disposal bag  28 . Accordingly, the inclined surfaces  32 - 38 , the tube  55  and the aperture  30  facilitate the deposit of articles and material into the disposal bag  28  carried by the receptacle  26 . 
     In one embodiment, a pair of pivot arms  56  may be preferably secured to the side edges  18 ,  20  of the housing  12  by a pair of mounting pins  58  in order to secure the housing  12  to the receptacle  26  in a hinged manner as described in greater detail below. This is not utilized, however, with the support assembly described below. In any event, the housing  12  is arranged to be pivoted away from the disposal bag  28  in order to remove the disposal bag  28  from the receptacle  26  when it is full. 
     A control console  60  extends upwardly from a rear portion of the top  22  of housing  12  and preferably includes a downwardly and forwardly inclined control panel  62  surrounded by side members  64 ,  66 . As particularly illustrated in FIG. 4, a hollow interior control box  68  is disposed within the interior of the console  60  and forms a housing for the electronic components of the metal detector  10  as described in greater detail in the related and previously incorporated U.S. Pat. No. 5,659,247. 
     The control panel  62  may include a peak-hold type LCD bar graph  70  for displaying voltage levels induced in the detection circuitry by the deposit of metal articles through the aperture  30  of the housing  12  in order to allow an operator to estimate the size of the metal article disposed. Thus, an insignificant metal object such as a surgical staple or the like would provide a low signal level and would not set off the alarm as described in greater detail below, while a large and expensive surgical instrument would provide a high signal level and set off the alarm. The peak-hold feature causes the graph  70  to maintain the display for a time sufficient to enable operator inspection. In addition, a similar LCD bar graph  72  provides an indication of battery voltage to allow an operator to estimate the remaining battery life for the unit  10 . Finally, an LED low battery indicator  74  provides a positive indication of the need to recharge the batteries for the detector  10 . 
     The metal detector  10  is designed for ease of operation with minimal training. Toward this end, user friendly controls preferably comprise three buttons including a reset button  76 , an “n” button  78  and an “off” button  80 . The reset button  76  is designed to silence an audible alarm after detection of a metal article and to reset the metal detector for continued use. The “on” button  78  activates the power to the device  10  while the “off” button  80  deactivates the power source. The control panel  62  is preferably of a flexible membrane type commonly employed in microwave ovens in which the control buttons  76 ,  78  and  80  comprise zones designated by indicia which do not protrude above the panel  62 . The LCD bar graph displays  70  and  72  and the LED light  74  underlie the panel  62  and are displayed through transparent windows. Panels of this type are custom fabricated pursuant to customer specification by any number of vendors, and are well known to the art. 
     In preferred form, an induction member in the form of a detection coil  82  surrounds the aperture  30  and is designed to detect the presence of metal proximate thereto, particularly as it passes through the aperture  30 . The detection coil  82  in one form is mounted to the outside surfaces  84  of the tube portion  55  which defines the aperture  30 . In preferred form, the detection coil  82  is mounted to the support assembly as described below. While any type of induction member suitable for use in the present invention may be utilized as the detection coil  82 , is preferred that the primary coil be  26  gauge copper wire wound sixteen turns about the aperture  30  and that the detector coil  82  also be  26  gauge copper wire wound six turns about the aperture  30 . In this manner, when a metal object moves physically near the detection coil  82 , it causes a change in the electromagnetic field surrounding the coil  82 , and this causes a change in the current described below. This is true, however, whether the metal article is proximate the coil  82  by being placed through the aperture  30  or proximate the coil  82  by being placed against, on top or even nearby the housing  12 . 
     In order to insure that the detector  10  only detects metal articles passing through the aperture  30  and avoids any false readings from metal articles passing near the detection coil  82  outside the exterior housing  12 , a mechanism for sensing an object, metallic or otherwise, physically passing through the aperture  30  is disposed about the aperture  30 . In preferred form, this mechanism includes a plurality of pulse emitting members  86  which preferably are in the form of light emitting diodes (LED&#39;s), and a plurality of pulse detecting members  88  preferably in the form of infrared phototransistors. While the preferred form of the members  86 ,  88  include infrared LED&#39;s and infrared phototransistors, ultrasound emitters and detectors may also be utilized. Preferably, there are sufficient numbers of pulse emitting members  86  disposed along one flange  50  and sufficient numbers of pulse detection members  88  disposed along the opposite flange  54  in order to span the entire cross-sectional area of the aperture  30 . The pulse emitting members  86  are preferably positioned proximate the edge  42  away from the coil  82  to minimize electrical interference and are interconnected to the electronic components of the console  60  by wiring  90 . Likewise the pulse detecting members  88  are positioned proximate the edge  46  away from the coil  82  and are connected to the console  60  by wiring  92 . In preferred form, there are equal numbers of pulse emitting members  86  and pulse detecting members  88  aligned opposite each other so that as an object passes through the aperture  30 , it physically interferes with the detection by at least one member  88  of a pulse being emitted from the members  86 , and this interference is monitored by the members  88  and signaled to the control panel  60  in a manner described below. 
     In preferred form, a rechargeable nickel-cadmium or nickel metal hydride battery  94  provides all operating power for the detection circuitry of the device  10 . A jack  96  extends through the rear portion  16  and allows connection of the battery  94  to a conventional recharging device in a conventional manner. 
     In general, the device  10  of the present invention operates by powering the detection coil  82  so as to create a magnetic field surrounding it. If a metal member passes proximate to the detection coil  82 , a change is detected in the electromagnetic field therein. A mechanism, described in the referenced patent, calibrates the detection coil  82  by comparing the output voltage thereof caused by a change in the electromagnetic field thereabout to a reference voltage to establish a threshold voltage which is unaffected by transient fluctuations in the coil output voltage as described below. When the threshold voltage of the detection coil  82  is exceeded, an electric signal is generated to simultaneously activate the pulse emitting members  86 . If all the pulse emitting members  86  are detected by the pulse detection members  88 , nothing happens since it is clear that an object has not passed through the aperture  30 , and that the threshold voltage activated by the detection coil  82  was the result of a metal member passing near but outside the housing  12 . However, should the threshold voltage of coil  82  be exceeded so as to activate the pulse emitting members  86 , and one or more of the pulse detection members  88  is not activated, an alarm is triggered in response to the lack of activation by one or more of the pulse detection members. The only manner in which a pulse detection member  88  would not be activated is due to the physical blockage of the pulse emitted from a member  86  to prevent its paired member  88  from receiving and detecting the pulse. In addition, since the pulse emitting members  86  are only activated or turned on when the threshold voltage of the coil  82  is surpassed, non-metallic objects can consistently pass through the aperture  30  without generating an alarm signal since the pulse emitting members  86  are in a non-active state. Consequently, the combination of the detection coil  82 , the pulse emitting members  86  and the pulse detection members  88  and the circuitry interconnecting the same prevents false signals caused by metallic objects exterior to but proximate the detector  10  from being generated. 
     With particular reference to FIGS. 4-6, a typical cart or receptacle structure  26  is illustrated for holding a waste disposal bag  28  for use in conjunction with the metal detector  10 . It should be understood, however, that the metal detector  10  of the present invention may be utilized with any type of receptacle and may be modified to fit the desired end use whether it be in a hospital environment, a penal institution, a kitchen environment or the like. The receptacle  26  typically includes four tubular lower leg members  100 ,  102 ,  104  and  106  that are pivotally connected together in pairs by pivotal connection members  108  and  110 . The pivotal connection members  108 ,  110  may include rivets, pins, bolts, screws or any other appropriate member pivotally interconnecting legs  100  to  102  and  104  to  106 . 
     The upper portions of the receptacle  26  include a pair of substantially U-shaped members  112 ,  114  secured to the upper portion of legs  100 ,  104  and  102 ,  106 , respectively. Preferably, each U-shaped portion  112 ,  114  includes, respectively, a substantially transverse crossbar member  116 ,  118  extending between respective side frame bars  120 ,  122  and  124 ,  126 . Interengaging telescoping connections  128 ,  130 ,  132  and  134  removably connect the side frame bars  120 ,  122 ,  124  and  126  to their respective lower leg members  100 ,  104 ,  102  and  106 , respectively. This detachable construction, in conjunction with pivotal connections  108 ,  110 , allows the receptacle  26  to be collapsed for shipping and storage, yet readily assembled without the use of tools. Preferably, the upper U-shaped portions  112 ,  114  are formed from a non-metallic material such as PVC plastic tubing in order to minimize interference with the metal detector&#39;s circuitry. The lower components of the receptacle  26  may be formed from a lightweight tubular metal material such as aluminum tubing. A bag support rack  128  includes four comer portions pivotally connected at  130  to lower end portions of the leg members  100 ,  102 ,  104  and  106 . In addition, the rack  128  has a two-piece construction, with side rail members bifurcated at abutting joints  132 . Accordingly, the two rack halves may be folded upwardly for storage and transportation of the receptacle  26 . The leg members  100 ,  102 ,  104  and  106  terminate in respective casters  134 ,  136 ,  138  and  140  which allow the receptacle  26  to be easily rolled to a desired location for use. In use, a medical waste disposal bag  28  is placed on the rack  128  with the upper side portions  142  of the bag  28  folded outwardly over the crossbars  116 ,  118  to maintain the mouth of the bag  28  in an open condition for access by the aperture  30  of the device  10 . 
     With reference to the FIGS. 4-6, the housing  12  is pivotally connected to the receptacle  26 . In this particular embodiment without a support assembly, a hinge member  56  in the form of an aluminum strut has a first end pivotally secured by a fastener  58  to the side portion  18  of the housing  12 . A second fastener  144  secures an opposite end of the pivot strut  56  to the aperture  146  in the upper portions of the side frame members  120 . Fasteners  58  and  144  may take the form of bolts, screws, rivets or pins. It should be understood that identical pivotal struts and fastener assemblies  56  are secured on both sides of the housing  12  and attach both side portions  18 ,  20  of the housing  12  to the tubes  120 ,  122  of the receptacle  26 . By virtue of this compound physical linkage, the entire housing  12  may thus be pivoted along an arc between a closed position as illustrated in FIG. 5 wherein the housing  12  is securely fixed about the transverse crossbars  116  and  118  of the receptacle  26  and the aperture  30  opens directly to the open end of the bag  28 , and an open position. The open position is illustrated in the cross-referenced and incorporated U.S. Pat. No. 5,576,621 and is designed to rotate the front end member  14  away from engagement with the transverse crossbar  118  and rotate the housing  12  greater than 90° so as to gain full access to the open end of the bag  28  without passing through the aperture  30  or in any manner being hindered by the device  10 . Thus, it should be noted that the housing  12  and the receptacle  26  are preferably complementary dimensions such that the crossbars  116 ,  118  or the receptacle  26  nest within the housing  12  at the rear  16  and front-end portions  14 , respectively. 
     Referring now to FIGS. 1, and  7 - 10 , the preferred embodiment is illustrated wherein a support assembly  150  is provided for releasable attachment to the housing  12 . It should be understood that while the assembly  150  may be constructed from any desired material, the assembly  150  is preferably a unitary non-metallic member preferably in the form of injection molded plastic. The assembly is sized and shaped to be located beneath the housing  12  so that the housing  12  overlaps the structure  150 . The assembly  150  is designed to provide structural support for the housing  12  as well as proper alignment of the various operating components of the housing  12  as explained above. Moreover, it is also designed to provide easy assembly adapted to mass production of the detector device  10 . 
     Referring to the FIGS. 1, and  7 - 10  in more detail, the support assembly  150  preferably is in the form of a substantially rectangular base member  152  having a front portion  154 , a rear portion  155 , and two opposed side portions  156  and  158 . The size and shape of the base member  152 , however, is determined by the size and shape of the housing  12  in that the base member  152  is adapted to fit within and beneath the housing  12  for carrying the operating components of the device  10 . In preferred form, the base member  152  includes a central aperture  160  sized and shaped so as to align with the opening  30  of the housing  12  and is releasably attachable to the housing  12 . Preferably, a plurality of connection tabs  162  project outwardly from the edges of the support member  150 , and a plurality of mating slots  164  are disposed in the side portions of the housing  12  for selective interengagement with the tabs  162 . 
     A plurality of mounting posts  166  project upwardly into the housing  12  when the base member is in place beneath the housing  12 . The posts  166  are preferably spaced along the front portion  154 , the rear portion  155  and both side portions  156 ,  158  so as to encircle the aperture  160 . Each post  166  preferably includes a notch portion  168  at the distal end thereof adapted to carry the induction member, which in the embodiment previously illustrated in FIG. 1 is in the form of an induction coil  82 . In this manner, the induction coil  82  surrounds the opening  30  and aperture  160  so as to detect any metallic objects passing through or near the opening  30  and aperture  160  as previously discussed. 
     As discussed above, the preferred form for the sensing mechanism of the detection device  10  of the invention is a plurality of pulse emitting members in the form of infrared light emitting diodes  86  (FIGS. 2-3) positioned along one side portion  156  of the support assembly  150 , and a plurality of pulse receiving members in the form of infrared light phototransistors  88  (FIGS. 2-3) positioned opposite the diodes  86  along the opposite side portion  158 . While any type of arrangement may be used to mount the pulse emitting and receiving members  86 ,  88  to the support assembly  150 , they are preferably mounted, respectively, to a pair of circuit boards (not illustrated) using known technology. In turn, a first slot  170  is disposed in the base member side portion  156 , and a second slot  172  is disposed in the opposite base member side portion  158 . The slot  170  is sized and positioned so that the circuit board carrying the pulse emitting members  86  can be readily placed therein in a predetermined position. Likewise, the slot  172  is sized and positioned so that the circuit board carrying the pulse receiving members  88  can be readily placed therein in a predetermined position immediately opposite the light emitting members  86  across the opening  30 . A plurality of spring clips  174  are provided to firmly hold a circuit board within the slot  170 , while a plurality of spring clips  176  are likewise provided to firmly hold a circuit board within the slot  172 . 
     Several problems exist in previous metal detection designs. These problems include interference with the light receiving members by ambient light and cross-pulse sensing. In ambient light interference, outside (ambient) light may be detected by the light receiving members  88  in addition to the pulsed light emitted by the light emitting members  86 , and such erroneous detection can cause errors. Moreover, the light pulses emitted may be of sufficient width that they are received by more than one light receiving member  88 , rather than be received only by the receiving member  88  directly opposite the emitting member  86 . This too can interfere with the proper operation of the device. To eliminate these problems in the present invention, a plurality of pulse regulating elements  180  are provided at each side portion  156 ,  158 . In preferred form, each light regulating element  180  is in the form of a planar ear plate  182  projecting upwardly from the base member  152  into the path of the light emitted from the light emitting members  86  and received by the light receiving members  88 . Each ear plate  182  includes a pinpoint opening  184  designed to narrow the width of the light pulse passing therethrough. In preferred form, an ear plate  182  is positioned adjacent each light emitting member  86 , and an ear plate  182  is likewise positioned adjacent each light receiving member  88 . In this manner, the width of the light beam emitted from each light emitting member  86  is narrowed as it passes through the pinpoint opening  184  of the adjacent ear plate  182  and is again likewise narrowed as it passes through the opening  184  of the plate  182  adjacent the light receiving member  88 . In this manner, ambient light is blocked from being received by the light receiving members  88  due to the proximity of the plate  182  to the receiving members  88 , since only the narrowed light passing through the adjacent plate opening  184  is received by the light receiving member  88 . In addition, cross-pulse sensing is prevented since the light being emitted by the light emitting members  86  is immediately narrowed by the adjacent plate opening  184  rather than being allowed to spread in width as it is emitted and passes across the opening  30 . Moreover, the emitted light is again narrowed by the plate opening  184  of the plate  182  adjacent the oppositely disposed light receiving member  88 . Thus, only the light emitted by the oppositely paired light emitting member  86  can be received by the appropriate light receiving member  88 . 
     To assist in the maintenance and proper placement of the operating elements of the housing  12  and device  10 , the base member  152  includes an elevated stanchion portion  186  which surrounds the aperture  160 . The stanchion portion  186  adds strength to the base member  152  and prevents torsional movement of the support assembly  150  when attached to the housing  12 . Such torsional movement can inadvertently misalign the light emitting and receiving members thus causing errors in the signals registered by the device  10 . By adding torsional stiffness throughout the support assembly  150 , the stanchion portion  186  assists in the proper operation of the device  10  during use thereof. 
     As previously described, the housing  12  is preferably designed to be removably attached to a receptacle structure  26  in pivotal form so that the housing  12  may be rotated upwardly to remove the waste disposal bag  28 . In preferred form, the housing  12  is secured to the receptacle using the support assembly  150 . To accomplish this task, a first channel or trough  188  is formed along the front portion  154  and is sized and shaped to receive and rest upon the upper U-shaped portion  112  of the receptacle  26 . Likewise, a second channel or trough  190  is formed in the rear portion  155  and is sized and shaped to receive and rest upon the upper U-shaped portion  114  of the receptacle  26 . In preferred form, a pair of shelves  192 ,  194  each having a screw aperture  196  therein are formed adjacent the second channel  190 . Attachment elements  198  are provided to be secured to the shelves  192 ,  194  by screw attachment members  200 , respectively. The shape of the attachment elements  198  permits the U-shaped portion  114  of the receptacle  26  to be pivotally secured within the second channel  190  to enable the housing  12  to be pivoted away from the receptacle structure  26  while being securely maintained in place thereon. 
     A pair of attachment arms  202 ,  204  depend downwardly from each side of the rear portion  155 . These attachment arms are provided for releasably securing the disposal bag  28  to the housing  12 , while the opposite end of the bag  28  is hung over the upper U-shaped portion  112  of the receptacle  26  and maintained in place by the form fit between the channel  188  and the U-shaped portion  112 . In addition, a battery case  206  is molded into the rear portion  155  of the base member  152 , while a pair of posts  208 ,  210  and a support plate  212  are provided for securing the operating circuit board (not illustrated) which carries the electronic components and alarm for the device  10 , as more clearly described in the referenced U.S. Pat. No. 5,659,247. The support plate  212  preferably includes a plurality of holes  214  therein to assist in the audible capability of the alarm carried on the operating circuit board. 
     As can be clearly seen from the above, the support assembly of the present invention provides support structures and alignment elements for the operational components of the metal detection device. The support assembly is designed to be injection molded so as to enable ease of manufacture. Moreover, this arrangement allows mass production of the device of the invention, thus reducing the overall costs of the metal detection device. The components of the metal detection device of the invention are easily attached in proper position due to the arrangement of the support assembly of the invention, and this permits the accurate placement and maintenance of the operational components of these devices. Finally, the present invention provides a metal detector which is readily attachable and removable from wheeled receptacles and which includes a support structure which accurately positions the sensing elements of the device throughout the operational lifetime of the detector. 
     The foregoing description and the illustrative embodiments of the present invention have been described in detail in varying modifications and alternate embodiments. It should be understood, however, that the foregoing description of the present invention is exemplary only, and that the scope of the present invention is to be limited to the claims as interpreted in view of the prior art. Moreover, the invention illustratively disclosed herein suitably may be practiced in the absence of any element which is not specifically disclosed herein.