Wafer for use in the selective connecting and disconnecting of plastic tubes
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of application Ser. No. 158,505, filed Nov. 29, 1993, now U.S. Pat. No. 5,397,425, which in turn is a continuation-in-part of Ser. No. 139,833, filed Oct. 22, 1993 now abandoned, which in turn is a continuation-in-part of application Ser. No. 965,875 filed Oct. 23, 1992, now U.S. Pat. No. 5,279,685, which in turn is a continuation-in-part of application Ser. No. 764,249 filed Sep. 23, 1991, now U.S. Pat. No. 5,209,800, which in turn is a continuation-in-part of application Ser. No. 682,977 filed Apr. 10, 1991, now U.S. Pat. No. 5,156,701, which in turn is a continuation-in-part of application Ser. No. 604,967 filed Oct. 29, 1990, now abandoned, which in turn is a continuation-in-part of application Ser. No. 569,855 filed Aug. 20, 1990, now U.S. Pat. No. 5,141,592. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to the total containment welding of plastic tubes. Various prior art exists disclosing different approaches for welding plastic tubes together. Prior patents disclose processes where the weld connection depends on the melt rheology of plastic resulting in non-uniform size of the weld connection. No attempt was made in the prior art to gain control of the size of the weld connection. 
     Parent application Ser. No. 158,505 discloses various wafer constructions for use in the total containment welding of plastic tubes and in the selective connect and disconnect of the plastic tubes. Such wafers are sufficiently effective that the same wafer could be used multiple times by removing the plastic material accumulated on the wafer after each use. In certain applications, however, it is desired to prevent the multiple use of the wafer and to assure that the wafer will be used only once. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide a wafer of the type disclosed in parent application Ser. No. 158,505 wherein there is assurance that the wafer can only be used once. 
     It is a further object of this invention to provide such a wafer which is capable of inactivating the total containment device where the wafer mounted in the device has previously been used. 
     In accordance with this invention the wafer is preferably generally of the type disclosed in parent application Ser. No. 158,505 in that it is in the form of a flat plate having opposite sides, each of which is disposed toward a respective set of first and second clamp jaws. Each of the sides of the wafer has an outwardly extending scoop generally located in the plane between the first and second clamp jaws for removing plastic material from the plastic tube as the wafer moves through the gap to control the size of the weld connection. The wafer in the preferred practice of this invention also includes an aperture or hole extending completely therethrough. The aperture is covered with a sensing material. The total containment welding device includes a sensor for sensing the material. If the material is not sensed the device is inactivated. A material is selected which preferably is removed during operation of the device so that after a single use the aperture is no longer covered by the material. 
     The wafer may be provided with more than one aperture each of which has detector material. A more sophisticated sensing would be required to assure that all of the apertures are provided with the material. In another practice of the invention the hole or aperture may be an elongated slot having some indicia, such as a bar code, which could be visible to the naked eye or could be invisible and be capable of being sensed by the device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a wafer in accordance with this invention; 
     FIGS. 1A and 1B are side elevational views of a portion of a wafer similar to that of FIG. 1 showing alternate practices of this invention; 
     FIG. 2 is a top plan view of the wafer shown in FIG. 1; 
     FIGS. 3 and 4 are front and rear elevational views of the wafer shown in FIGS. 1-2; 
     FIG. 5 is a bottom plan view of the wafer shown in FIGS. 1-4; 
     FIG. 6 is a perspective view of the wafer shown in FIGS. 1-5; 
     FIG. 7 is a side elevational view showing the wafer of FIGS. 1-6 mounted in a holder; 
     FIG. 8 is a top plan view of the holder/wafer shown in FIG. 7; 
     FIGS. 9 and 10 are front and rear elevational views of the wafer/holder shown in FIGS. 7-8; 
     FIG. 11 is a bottom plan view of the wafer/holder shown in FIGS. 7-10; 
     FIG. 12 is a perspective view of the wafer/holder shown in FIGS. 7-11; 
     FIG. 13 is a top plan view of a portion of a total containment device in which the wafer of FIGS. 1-12 could be used; and 
     FIG. 14 is a cross-sectional view taken through FIG. 13 along the line 14--14. 
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to variations of the wafer shown and described in parent application Ser. No. 158,505, the details of which are incorporated herein by reference thereto. Such wafer could advantageously be used in a total containment device of the type described in parent U.S. Pat. No. 5,279,685. The details of the &#39;685 parent patent and of the other parent patents and applications are all incorporated herein by reference thereto. 
     The present invention includes features in the wafer to assure single use of a wafer. Advantageously, the preferred practice of this invention requires minimal modifications to the wafer and total containment device. 
     FIGS. 1-6 show the details of wafer 20. As shown therein wafer 20 is in the form of a flat plate having a pair of opposite sides 22,22. Wafer 20 also includes a cut-out or notch 24 for engagement by a pawl in the home position of the wafer in the manner described in parent U.S. Pat. No. 5,279,685. Wafer 20 also includes a pair of wings 26 as described in the various parent applications. 
     Wafer 20 is unique in that it also includes a scoop 28 on each of its sides. Scoop 28 is located generally in line with wings 26 which would be at an elevation which is in the general plane of the clamped tubes 18 where each upper jaw and lower jaw press against the tube ends to flatten the tube ends. See FIG. 13 and U.S. Pat. No. 5,279,685. Thus, scoops 28 are in a position to contact the melted tubes. 
     The wafer 20 also includes a slit 50 extending completely through the wafer downstream from scoops 28. As illustrated slit 50 extends inwardly from the downstream generally vertical trailing edge in a straight line generally horizontal direction toward the upstream generally vertical leading edge of wafer 20. Slit 50 terminates downstream from scoops 28. Slit 50 may be of any suitable dimension and preferably has a length of 7 mm and a width of 0.5 mm. Slit 50 is disposed in line with scoop 28 and wing 26 on each of the sides 22 of wafer 20. 
     The advantage of providing a slit, such as slit 50, in the heated wafer downstream from the scoops 28 is to permit the molten material from the tubes 18 to begin contacting each other at an earlier time while the tubes are still in the area of the heated wafer. 
     In order to assure the single use of the wafer, wafer 20 is provided with a hole or aperture 36 at any suitable location such as being generally in line with notch 24. Aperture 36 is intended to be covered by a sensing material 38. This can be conveniently accomplished by forming the wafer as a plate which is folded upon itself at one end 40 so that the wafer 20 is of double thickness, as best shown in FIGS. 2 and 4-6. Prior to the complete folding the sensing material 38 is positioned to cover hole 36. Material 38 is preferably selected to be of material which would melt or otherwise be destroyed upon the heating of the wafer. Thus, once there has been a single use of the wafer, material 38 no longer covers aperture 36 and can not be sensed in an attempted second use of the wafer. 
     FIGS. 13-14 illustrate, in general, portions of the total containment device 10 of the type described in parent U.S. Pat. No. 5,279,685. As shown therein device 10 includes a carriage 12 for moving the wafer through the device. Parent U.S. Pat. No. 5,279,685 discloses the inclusion of various sensors, such as for indicating that the wafer is properly loaded in the carriage and for detecting that the wafer is properly conditioned with respect to the clenching block. FIG. 14 illustrates one such sensor 14 which, in the device of the parent patent, functions as the aperture blockage sensor. Sensor 14 is mounted in the path of movement of aperture 36 and thus would sense aperture 36 passing through the path of view of sensor 14. Thus, the present invention advantageously makes use of a sensor already in device 10 for its single use sensing operation. If desired, however, one of the other sensors or a completely additional sensor may be used for this purpose. 
     In operation, as wafer 20 is moved in a downstream direction sensor 14 views aperture 36. If there is sensing material 38 located in aperture 36 the material will be sensed. Such sensing could be in terms, for example, of a voltage reading which would differ from the voltage reading of the copper wafer material 20 and would differ from the voltage reading of a completely open hole 36. If the sensor 14 does not detect the proper voltage which would result from the proper sensing material 38 being in aperture 36 then the device 10 would be inactivated. This would mean that either the wafer 20 had been previously used and no longer has sensing material 38 or that there is a manufacturing defect and the sensing material was not mounted over hole 36. 
     When the sensing material 38 is properly detected and other device requirements are met, the wafer 20 is heated for use in the selective connect/disconnect of the plastic tubes 18,18. The heating operation results in a melting of sensing material 38 so that hole 36 is completely exposed. 
     The concept of sensing a condition of the wafer which would indicate whether or not the wafer has been previously used can be practiced in various manners. FIG. 1A, for example, illustrates the provision of two holes 36A,36B, each with a sensing material 38A,38B. Sensing materials 38A and 38B may be the same or different materials. This arrangement would provide a more sophisticated reading to require a binary or sequential voltage reading from sensor 14 in order to prevent device 10 from being inactivated. Such more sophisticated reading would be desirable to make it more difficult for a user to attempt to insert sensing material back into wafer 20 after the wafer has already been used. 
     Cover material 38 is preferably a two mil thick polyethylene sheet which may contain carbon black. Such material could also be used as material 38A. Material 38B could likewise be the same material or could be a material having a different voltage characteristic. 
     FIG. 1B shows yet another practice of this invention wherein the aperture 36C is an elongated slot. The cover material 38C could be the same as cover material 38 or could simply be any suitable material, preferably a transparent material having some indicia thereon which would be detected by the sensor. For example, the indicia could be a bar code or some form of alphanumeric code. The indicia could be visible to the naked eye or could be invisible to the naked eye since it is only necessary that the indicia be visible to the sensor. 
     FIGS. 7-12 illustrate wafer 20 mounted in a suitable holder 60 which could be of the same general construction as the holder illustrated in FIG. 14 of parent U.S. Pat. No. 5,279,685. The purpose of the holder is to mount wafer in the carriage, during the initial movement of wafer 20. Holder 16 generally includes a split body 62 having a slot 64 into which wafer 20 would be slidably mounted. Interior of body 62 would include two registration recesses for receiving lugs 68 on wafer 20. Holder body 62 includes downward extensions 70 which have half round filets 72 to increase the frictional contact on wafer 20 by the spring action of the body extension 70 which thus act as spring arms. 
     In operation, wafer 20 would be mounted in holder 60 during the initial positioning of the wafer in carriage 12. As the wafer is moved downstream it is detached from holder 60 thereby exposing slit 50 which is initially covered by extension 70 of holder 60. 
     It is to be understood that the holder 60 illustrated in FIGS. 7-12 may be used with the type of wafer described in parent application Ser. No. 158,505 and is not limited to the type of wafer intended for single use purpose. Even where holder 60 is used for a single use wafer, the holder itself may be reused multiple times.