Patent Publication Number: US-2006011608-A1

Title: Cover system for heating unit

Description:
This application claims priority from U.S. Provisional Application Ser. No. 60/409,457, filed Sep. 10, 2002, the entire content of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD  
      The Invention relates to devices used in a sterilized environment.  
     BACKGROUND  
      In an operating room, everything is categorized as sterile or non-sterile. The sterile items, which include the surgeon&#39;s gloved hands and the instruments that come in contact with the patient, have been made free of microorganisms according to aseptic techniques. To reduce the risk of infection, operating room personnel act to preserve a “sterile field,” i.e., the region in the operating room that is properly sterile. Operating room personnel are continually mindful of the sterile field, and conscientiously act to avoid contact between sterile and non-sterile items. By maintaining the integrity of the sterile field, the operating room personnel reduce the risk of transfer of microorganisms from non-sterile areas and items to the surgical wound.  
      In some circumstances, such as operations involving resorbable implants, it may be expedient to use a heating unit in the operating room. Resorbable implants, such as resorbable thin bone plates, often need to be shaped prior to fixation into the body. The steps involved in shaping these resorbable implants typically include submersing the resorbable implants into a heated water bath whereby the implants become malleable. Once malleable, the implants may be shaped into a desirable configuration.  
      The implants themselves are sterile, the water (or saline or other solution) in the bath is sterile, and the tray that holds the bath is sterile. The heating unit, however, typically includes electronic components and cannot be sterilized.  
     SUMMARY  
      The invention relates to a cover system that may be used to shield off a non-sterilized heater unit in a sterilized environment. The invention provides a cover system for a non-sterilized heater unit comprising a tray and a cap formed around a mouth of the tray. The tray holds a liquid medium that may be heated to various temperatures, and the cap is effective to prevent exposure of the non-sterilized heater unit to a sterilized environment. In one embodiment, the cover system is a single unit and is autoclavable, i.e., sterilizable in an autoclave.  
      The cover system is sized to fit over a heater unit, and the contours of the cover system may depend upon the contours of the heater unit being covered. In some embodiments of the invention, the cap is transparent or translucent, allowing instrumentation on the heater unit to be visible even when the heating unit is covered.  
      The cap and the tray may be coupled together by any of several techniques. They may, for example, be a single-piece construction, or they may be permanently joined by molding or another technique. The cap and the tray may also be coupled mechanically with a tight junction, and sealed with a sealant. With each of these techniques, the tray and the cap can be coupled to prevent the passage of air and water. A hermetic seal between the tray and the cap preserves the sterile field by physically separating a significant portion of the non-sterile heating unit from the sterile field. The hermetic seal further protects the heating unit in the event of spillage of water from the tray.  
      The cover system optionally includes a sterile drape. Moreover, in some embodiments of the invention, the cap includes a lip that can support a sterile drape. In that case, the drape effectively expands the cover system, thereby providing an added measure of isolation of the heater unit from the sterile field.  
      In one embodiment, the invention is directed to a cover system comprising a tray to hold a liquid to be heated by a heater unit. The tray includes a mouth. The cover system further includes a cap coupled to the tray, with the cap extending around the mouth of the tray and the cap being sized to cover at least a portion of the heater unit. The tray may be made of a material such as stainless steel, and the cap may be made of medical grade plastic. Several different materials may also be used to make up the cover system, however. The cover system may also include a drape, made of a material such as silicone.  
      In another embodiment, the invention is directed to a cover system comprising a tray and a cap coupled to the tray. The tray includes a mouth. The cap extends around the mouth and is sized to cover at least a portion of a heater unit. In accordance with the invention, the tray and the cap are coupled to prevent the passage of air and water.  
      In a further embodiment, the invention presents a system comprising a heater unit and a cover system sized to cover at least a portion of the heater unit. The cover system includes a tray and a cap coupled to the tray, and the tray and the cap are coupled to prevent the passage of air and water.  
      The invention may provide one or more advantages. In particular, the cover system allows the tray to be brought in contact with the heating element of the heater unit. As a result, the heater unit can transfer adequate heat to the tray without compromising the sterile field. It is unnecessary to have an intervening sterile guard between the tray and the heating element. The hermetic seal or tight junction between the tray and the cap prevents the passage of air and water, thereby preserving the sterile field and protecting the heating unit from spills.  
      The cover system may be easily sterilizable and reusable. The cover system can be easily placed over the heater unit and requires no complicated assembly. The addition of an optional drape can further isolate the heater unit from the sterile field.  
      The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is a cross-sectional side view of a heater unit and a cover system.  
       FIG. 2  is a cross-sectional side view of a heater unit and a cover system similar to  FIG. 1 , but further comprising a lip and a drape attached to the lip.  
       FIG. 3  is a perspective drawing illustrating a cover system separated from a heater unit.  
       FIG. 4  is a perspective drawing illustrating the cover system and heater unit shown in  FIG. 3 , with the cover system in place over the heater unit.  
       FIG. 5  is a perspective drawing illustrating the cover system and heater unit shown in  FIGS. 3 and 4 , with the cover system in place over the heater unit and a drape stretched above the cover system and heating unit.  
       FIG. 6  is a perspective drawing illustrating a stand, with a heater unit, cover system and drape deployed on the stand.  
       FIG. 7  is a perspective drawing illustrating an alternate embodiment of a cover system and a heater unit. 
    
    
     DETAILED DESCRIPTION  
      Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same or similar reference numbers are used in the drawings and the description to refer to the same or like parts. It should be noted that the drawings are in simplified form and are not to precise scale. In reference to the disclosure herein, for purposes of convenience and clarity only, directional terms, such as, top, bottom, left, right, up, down, over, above, below, beneath, rear, and front, are used with respect to the accompanying drawings. Such directional terms should not be construed to limit the scope of the invention in any manner.  
      Although the disclosure herein refers to certain illustrated embodiments, it is to be understood that these embodiments are presented by way of example and not by way of limitation. The intent of the following detailed description, although discussing exemplary embodiments, is to be construed to cover all modifications, alternatives, and equivalents of the embodiments as may fall within the spirit and scope of the invention as defined by the appended claims.  
      An effective cover system for a heater unit, such as a surgical heater unit, is described. In a broad embodiment, the cover system comprises a tray and a cap formed around a mouth of a tray. Preferably, the cover system can snugly fit over a heater unit, so as to effectively cover the heater unit. A variety of heater units may be used in accordance with this invention. Generally, the heater unit has a heating surface on top of the heater unit to heat up the tray. In one embodiment, a heater unit used in accordance with this invention is capable of heating a liquid medium in the tray to a temperature of about 60 to about 70 degrees Celsius. U.S. Pat. No. 6,202,935 describes one exemplary heating unit, the disclosure of which is incorporated in its entirety herein by reference.  
       FIG. 1  is a cross-sectional schematic view of a cover system  20  and a heater unit  21 . The cover system  20  is shown in  FIG. 1  comprising a tray  22  and a cap  24 . As will be described below, tray  22  and cap  24  may be constructed of different materials, but are coupled to form a single piece cover system. The tray  22  in the illustrated embodiment comprises a base  29  and a side wall  30  running up from the base  29  to hold a liquid medium  26  therein. The base  29  of the tray  22  may be of any shape, such as square, rectangular, oval or irregular. In one embodiment, the base  29  is rectangular shaped, and the side wall  30  extends between the four corners of the base  29 . An open end of the side wall  30  forms a mouth of the tray  22 . In another embodiment, the base  29  curves into the side walls  30  without corners, thereby forming the mouth. The mouth of tray  22  receives the sterile water or saline solution used in the heated water bath.  
      The cap  24  is formed around, or extends from, the mouth of the tray  22  so as to effectively cover the heater unit  21 . For example, from the mouth of the tray  22 , the cap  24  extends over the heater unit  21  and drops down the side of the heater unit  21 . In one embodiment, the cover system  20  snugly fits over the heater unit  21 , and the tray  22  rests against or in close proximity to a heating pad  36  or other heating element of the heater unit. The cap  24  need not contact heater unit  21 , however. As shown in  FIG. 1 , an air gap  28  may separate the cap  24  from the heater unit  21 . The air gap  28  provides some thermal insulation so that the cap  24  stays cool while the heating pad  36  heats tray  22 .  
      The tray  22  of the cover system  20  may be constructed from any material effective to transfer heat from the heater unit  21  to the liquid medium  26 , such as water, contained by the tray  22 . In one embodiment, the tray  22  is able to effectively transfer heat to the liquid medium  26  contained therein. For example, a tray  22  in accordance with the invention is capable of transferring adequate heat from the heater unit  21  below to heat a liquid medium  26  to about 60 through about 70 degrees Celsius in less than about 15 minutes, and preferably less than about 10 minutes. Preferably, the tray  22  does not rust and does not melt while transferring the required heat to the liquid medium  26 . In one embodiment, the tray  22  is stable to repeated sterilization processes, such as autoclaving and gamma radiation.  
      Furthermore, contaminants, such as microbes and the like, cannot permeate from one surface of the tray  22  to the other. Preferably, the tray  22  of the invention is autoclavable for sterilization. In one embodiment, the tray is constructed from stainless steel, the like, or mixtures thereof. In one embodiment, the tray  22  may have a dimension of 5⅛ inches (13.0 cm) by 6 9/16 (16.7 cm) inches by 4 inches (10.1 cm). Preferably, the tray may hold about 1 to about 2 liters, and preferably about 1.5 liter, of the liquid medium  26 .  
      The cap  24  of the cover system  20  may be constructed from any material effective to seal off any contaminants on the surface of the heater unit  21 . Preferably, the cap  24  does not rust and does not melt when placed over the heater unit  21  in operation. In one embodiment, the cap  24  is stable to repeated sterilization processes, for example autoclaving and gamma radiation. In another embodiment, the cap  21  is constructed from the same material as that of the tray  22 , such as stainless steel. In one embodiment, the cap  24  is constructed from a material different from that of the tray, such as an autoclavable plastic. An example of an autoclavable plastic is Ultem plastics or resins, commercially available from GE Plastics of Pittsfield, Mass. In some embodiments, the autoclavable plastic is transparent or translucent, allowing medical personnel to be able to see instrumentation on the heater unit  21 , such as a temperature readout.  
      In one embodiment, the tray  22  and the cap  24  are molded as a single unit cover system  20 . In one embodiment, the cover system  20  may be constructed from deep molding a deep drawn stainless steel tank into a tinted (smoked) plastic cap. In another embodiment, the tray  22  and the cap  24  are removably attached together to form the cover system  20 . For example, the mouth of the tray  22  meets and attaches with the cap  24 , and a tight junction  23  is formed therebetween. By tight junction, it is meant that a contaminant cannot pass through the interface where the tray  22  and the cap  24  meet. The use of any known means of attachment between the tray  22  and cap  24  is possible, such as an attachment through use of an adhesive, or riveting, clamping, snapping, bolting or latching. A sealant, such as silicone seal or a gasket, may be employed to create or improve a tight junction  23  between the tray  22  and the cap  24 . In particular, the sealant may be deployed between the tray  22  and the cap  24  to create or to assure an airtight and watertight hermetic seal.  
      Whether formed as single piece or joined with a tight junction, the tray  22  and cap  24  are coupled by a hermetic seal that prevents the passage of air and water. The hermetic seal serves at least two functions. First, the hermetic seal preserves the sterile field by physically separating the non-sterile heating unit  21  from the sterile field. Second, the hermetic seal protects the heating unit  21 . In the event water from tray  22  spills, water will not penetrate the hermetic seal and get into the heating unit  21 , and possibly causing damage to the electronic components of the heating unit  21 . In a preferred embodiment, the cover system  20  comprising the tray and the cap is sterilized prior to use.  
      Referring to the cross-sectional schematic view shown in  FIG. 2 , the cap  24  preferably comprises a lip  31  surrounding the mouth of the cap  24 . In other words, the cap includes an outer perimeter that extends around the heating unit  21 , and the outer perimeter includes the lip  31 . A drape  27  can be attached to the lip  31  of the cap  24  by various means, such as hook and loop fasteners including Velcro®. In such an embodiment, the lip  31  may be reduced or altered in size or shape, or eliminated. In a preferred embodiment of the invention, the drape  27  comprises an opening which is shaped to approximate the inner circumference of the lip  31 , so that the opening of the drape  27  can fit around the cap  24  and slide down to rest on the lip  31 . A circumference of the outer edge (measured in a radial direction) of the lip  31  is preferably slightly greater than a circumference of the opening of the drape  27 , so that the drape  27  is caught on the lip  31  to prevent the drape  27  from sliding further down and off of the lip. In one embodiment, the drape  27  is effective to cover the area surrounding the heater unit  21 .  
       FIG. 3  is a perspective view of an embodiment of the invention. A cover system  40  comprises a tray  42  and a cap  44 . The cap  44  is formed around the mouth of the tray  42 , and the junction  46  between the tray  42  and the cap  44  comprises a hermetic seal that prevents the passage of air and water.  
      The cover system  40  is sized to fit over a heater unit  48 . In particular, the cover system  40  is dimensioned so that the tray  42  rests in a well  50 , and the base  52  of the tray  42  rests against or is in close proximity to a heating pad  54  of the heater unit  48 . In addition, the cap  44  follows the general contours of the heater unit  48 . The cap  44  may be sized to touch the heater unit  48 , or may be sized to be separated from the heater unit  48  by an air gap when the tray  42  rests in the well  50 .  
       FIG. 4  is a is a perspective view of the embodiment of the invention shown in  FIG. 3 , with the cover system  40  covering the heater unit  48 . In the embodiment shown in  FIG. 4 , the cap  44  is transparent or translucent. Accordingly, instrumentation on the beater unit  48 , such as a temperature readout  56 , is visible through the cap  44  when the cover system  40  covers the heater unit  48 .  
      The embodiment of the cover system  40  shown in  FIGS. 3 and 4  provides some isolation of the heating unit  48  from the sterile field. The hermetic seal  46  between the tray  42  and the cap  44  preserves the sterile field by physically separating a significant portion of the non-sterile heating unit  48  from the sterile field. The hermetic seal  46  further protects the heating unit  48  in the event water from the tray  42  spills.  
      As shown in  FIGS. 3 and 4 , the cap  44  comprises a lip  58 , which can support a drape as shown below. As shown in  FIG. 4 , the lip  58  does not hinder access to an on-off switch  60  or a power cord  62  of the heater unit  48  when the cover system  40  covers the heater unit  48 . The lip  58  does not isolate the on-off switch  60  or the power cord  62  from the sterile field, however. When the drape is in place as shown in  FIG. 6  below, the on-off switch  60  and the power cord  62  are isolated from the sterile field.  
       FIG. 5  is a perspective view of the cover system  40  and the heater unit  48  shown in  FIGS. 3 and 4 , along with a drape  70 . The drape  70  includes an opening  72  that is shaped to approximate the inner circumference of the lip  58 , so that the opening  72  of the drape  70  can fit around the cap  44  and rest on the lip  58 . The drape  70  is flexible so that it can drape over nearby equipment. The drape  70  may also be transparent or translucent, so that the covered equipment, or parts thereof, can be easily seen.  
      The drape  70  is made of sterilizable material. A variety of materials may be used for the drape  70 . In one embodiment, the drape  70  comprises a thin, textured silicone membrane. The drape  70  may be sterilized in advance, and brought into the operating room in a sterile container. The drape  70  may be re-sterilized or discarded after use.  
      The drape  70  may be of any dimension. As shown in  FIG. 5 , the drape  70  can extend outward from the cap  44 , thereby covering heater unit  48  to a greater degree. In one embodiment, the drape  70  extends about one foot to two feet (30 to 61 cm) radially outward from the opening  72 , but the dimensions of the drape  70  may vary. Although  FIG. 5  shows the drape  70  as being substantially rectangular with the opening  72  in the approximate center of the drape  70 , the drape  70  may be any shape and the opening  72  may be located anywhere.  
       FIG. 6  is a perspective view showing an exemplary deployment of the invention. In an operating room, the heater unit  48  may be placed on a “Mayo stand”  74 , i.e., heater unit  48  may be supported on a tabletop  76  of the stand  74 . The cover system  40  covers the heating unit  48  and at least partially isolates the heating unit  48  from the sterile field. The drape  70  is deployed to cover the heater unit  48  and at least portions of the power cord  62  and the stand  74 . In the embodiment shown in  FIG. 6 , the drape  70  extends about one foot (30 cm) below the tabletop  76  of the stand  74 . When cover system  40 , heater unit  48  and drape  70  are deployed as shown in  FIG. 6 , a sterile person in the operating room is less likely to become non-sterile by inadvertently bumping stand  74 .  
      In this configuration, the drape  70  isolates the on-off switch  60  from the sterile field. The drape  70  does not prevent operating room personnel from having access to the on-off switch  60 , however. Non-sterile personnel can access the on-off switch  60  by reaching under the drape  70  without invading the sterile field. Sterile personnel can access the on-off switch  60  by depressing the on-off switch  60  through drape  70 .  
      The cover system of the invention may be shaped as to accommodate for the various features of the heater unit it is covering. For example,  FIG. 7  shows a cover system  120  sized and configured for a different model of heating unit  122 . In the embodiment of the cover system shown in  FIG. 7 , the cap  124  includes a cut out  135  to provide accessibility to an on/off switch  134  on the heater unit  122 . The cut out  135  may be patched over by a soft cover  140  to allow for manipulation of the on/off switch  134  through the soft cover  140 . Preferably, the soft cover  140  is a plastic, and more preferably a transparent plastic. A similar cut out  142  may be available to allow access for other items, such as the power cord  144  of the heater unit  122 . Other cut outs may be available for viewing of a temperature gauge or other instrument on the heater  122 , for example. A drape can be added to optionally cover any cut outs and corresponding elements of heater unit  122  that protrude through such cut outs.  
      The invention may provide one or more advantages. In particular, the cover system allows the tray to be brought in contact with the heating element of the heater unit. As a result, the heater unit can transfer adequate heat to the tray without compromising the sterile field. The invention can avoid the need for an intervening sterile guard between the tray and the heating element. The hermetic seal or tight junction between the tray and the cap prevents the passage of air and water, thereby preserving the sterile field and protecting the heating unit from spills.  
      The cover system may be easily sterilizable and reusable. The cover system may be easily placed over the heater unit and typically requires no complicated assembly. The addition of an optional drape can further isolate the heater unit from the sterile field.  
      While this invention has been described with respect to various specific examples and embodiments, it is to be understood that the invention is not limited thereto and that it can be variously practiced. A cover system may be customized to the conformation of a particular kind of heater unit, for example, so the invention is not limited to the specific conformations shown in the figures.  
      Because a cover system may be dimensioned for a particular kind of heater unit, the cover system may include one or more coupling elements that temporarily couple the cover system to the heater unit. Snaps, hasps, springs, ribs, notches, grooves and clasps are examples of coupling elements. A cover system may include leaf springs, for example, that mate to grooves on the heater unit, or vice versa. With coupling elements such as these, the cover system can snap into place in the heater unit. Not only do coupling elements help secure the cover system to the heater, the coupling elements may also provide audible or tactile feedback indicating to a user that the cover system is properly in place.  
      Furthermore, the cover system need not be formed from a tray and cap of different materials, but may be formed as a single-piece construction. The drape may be included as an integral part of the cover system, or may be omitted completely.  
      The cover system need not include a lip to support a drape. As shown in  FIGS. 3-7 , a cover system may include tapered sides, and the opening of the drape may be sized to slide part way down the sides.  
      The invention need not be constructed with the specific materials described herein. For example the tray need not be made of stainless steel, but may be made of another metal, or may be made of plastic or another heat-conductive material. The cap need not be formed from a plastic or polymer, but may be formed from metal or any other material. These and other embodiments are within the scope of the following claims.