Abstract:
A medical treatment apparatus, and in particular an extra-corporeal blood treatment apparatus, has a socket unit for the connection of a plug unit belonging to a device for supplying a medical fluid for the medical treatment apparatus. A filling apparatus for filling a device for supplying a medical fluid has a socket unit for the connection of a plug unit of the device for supplying a medical fluid. The device has a plug unit having means for indicating two states of operation, while the socket unit of the treatment apparatus has means for destroying the means for indicating two states of operation. When the plug unit is connected to the socket unit, the means for indicating two states of operation are destroyed, to rule out the possibility of the device being re-used. Re-use of the device is ruled out by the fact that the device cannot be re-filled with fluid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Application Ser. No. 61/611,623, filed on Mar. 16, 2012, and Application No. DE 10 2012 005 194.8, filed in the Federal Republic of Germany on Mar. 16, 2012, each of which is expressly incorporated herein in its entirety by reference thereto. 
    
    
     FIELD OF INVENTION 
     The present invention relates to a medical treatment apparatus, and in particular an extra-corporeal blood treatment apparatus, having a socket unit for the connection of a plug unit belonging to a device for supplying a medical fluid for the blood treatment apparatus. As well as this, the present invention also relates an apparatus for filling a device for supplying a medical fluid for a medical treatment apparatus, having a socket unit for the connection of a plug unit belonging to the device for supplying a medical fluid. What is more, the present invention also relates to a device for supplying a medical fluid for a medical treatment apparatus, having a plug unit for connection to a socket unit of the medical treatment apparatus or the apparatus for filling the device for supplying a medical fluid. 
     BACKGROUND INFORMATION 
     There are a large number of known connectors for connecting external components to units used in medical technology. The access to the units used in medical technology is generally gained by means of plugs which are plugged into mating sockets on the units used in medical technology. This being the case, the units used in medical technology, which will be referred to in what follows as items of medical apparatus, have a suitable socket unit while the external components have a plug unit. 
     What are used to treat patients suffering from kidney diseases are items of blood treatment apparatus which include in particular the known items of extra-corporeal blood treatment apparatus or items of apparatus for peritoneal dialysis. For the patient&#39;s blood to be cleansed, it is necessary for medical treatment fluids to be supplied. These include for example dialysis fluid or substitution fluid. In what is known as automatic peritoneal dialysis (APD) or acute dialysis, the medical treatment fluids are processed automatically in the blood treatment apparatus. The treatment fluids are supplied in fluid reservoirs which are connected to the treatment apparatus. The fresh dialysis fluid is pumped from the fluid reservoir into the blood treatment apparatus and used fluid is pumped out of the treatment apparatus and into the fluid reservoir. The fluid reservoir may already contain a concentrate which needs to be diluted with water. When this is the case, the fluid reservoir merely needs to be filled with water. Because of this, water too is understood to be a medical fluid in this connection. It is also possible for there to be a plurality of fluid reservoirs connected to a blood treatment apparatus when a treatment fluid ready for use is produced in the treatment apparatus by mixing a plurality of fluids. The liquid reservoir is once again connected to the blood treatment apparatus by a plug unit which is inserted in a socket unit on the blood treatment apparatus. 
     For filling the device for supplying dialysis fluid, there are known items of apparatus to which the devices for supplying dialysis fluid can be connected. For this purpose, the items of filling apparatus once again have a socket unit which can be connected to the plug unit of the device for supplying dialysis fluid. 
     A device for supplying a treatment fluid is described in, for example, European Application No. EP 0 575 970 A2. This device for supplying dialysis fluid comprises a bag for receiving the fluid, to which is connected a flexible line which is connected to a plug at its free end. The dialysis apparatus has a socket into which the plug is plugged. With the plug and socket, it is possible to make two flow-permitting connections to enable fresh dialysis fluid to be conveyed out of the bag and into the dialysis apparatus and used dialysis fluid to be conveyed back into the bag. 
     When the device for supplying medical fluids is being filled, it must be ensured that the possibility of the device for supplying medical fluids being re-used is ruled out. 
     European Application No. EP 0 476 089 B1 describes a device for irrigating tissues which has a module to receive a cassette intended for once-only use. The module has an undercut recess into which a projection in hook form on the cassette fits when the cassette is inserted in the module. When the cassette is withdrawn from the module, the projection in hook form breaks off. Described in European Application No. EP 0 947 206 is a plug unit of a device for supplying dialysis fluid which has a bar code. 
     SUMMARY 
     An object underlying the present invention is to increase the safety with which items of blood treatment apparatus, and particularly items of extra-corporeal blood treatment apparatus or items of apparatus for peritoneal dialysis, are supplied with medical fluids and particularly dialysis fluid. 
     The blood treatment apparatus according to the present invention or the apparatus according to the present invention for filling the device for supplying medical fluids has a socket unit, whereas the device according to the present invention for supplying medical fluids has a plug unit. The socket unit and the plug unit are characterised in that a safe and secure connection can easily be made with the two units between the device for supplying medical fluids and, on the one hand, the blood treatment apparatus or, on the other hand, the apparatus for filling the device for supplying medical fluids. 
     The plug unit of the device according to the present invention for supplying a medical fluid has means for indicating two states of operation, while the socket unit of the medical treatment apparatus according to the present invention has means for damaging or destroying the means for indicating two states of operation. The means for indicating two states of operation and the means for damaging or destroying the means for indicating two states of operation are so designed that the means for indicating two states of operation are damaged or destroyed when the plug unit of the device for supplying a medical fluid is connected to the socket unit of the medical treatment apparatus. The first state of operation is thus the state before the plug unit is connected to the socket unit, when the means are intact, and the second state of operation is the state after the plug unit has been connected to the socket unit, when the means are damaged or destroyed. The means for indicating the two states of operation may also indicate other piece of information. However, what is crucial is that these means indicate at least the two states of operation. In a preferred exemplary embodiment the means are formed by an information carrier. 
     The means for indicating the two states of operation need not be completely destroyed. It is enough for these means, if they perform a function, to become unusable, by for example making the information on the information carrier no longer able to be read. 
     After once-only use for its intended purpose of the device for supplying a medical fluid, i.e., when the fluid has been fed to the treatment apparatus, the device cannot be filled with fluid again. Re-use of the device is thus ruled out. 
     The filling of a device for supplying a medical fluid which has already been used is ruled out by the apparatus according to the present invention for filling the device for supplying a medical fluid, which has a socket unit for the connection of the plug unit of the device for supplying a medical fluid. 
     The filling apparatus has means for detecting re-use of the device for supplying a medical fluid which are so designed that it is detected whether the means which the plug unit of the device for supplying a medical fluid has for indicating two states of operation are intact or are damaged or destroyed. 
     The basic principle of the present invention lies in preventing re-use of the device for supplying a medical fluid by ruling out even the filling of the device with a medical fluid. This rules out the possibility of devices for supplying a medical fluid which have already been used once finding their way back into circulation. 
     In a preferred exemplary embodiment of the present invention, the means for indicating two states of operation have a planar information carrier which carries machine-readable information on characteristic properties of the medical fluid such for example as the composition of the fluid or the amount of the said fluid. The information carrier thus serves not only to supply machine-readable information but also to detect re-use of the device. The information on the information carrier may for example be a matrix code but it may equally well be any other machine-readable code. 
     A further preferred exemplary embodiment makes provision for the information carrier to be applied to a portion of the plug unit of the device for supplying a medical fluid which is provided with a depression, the means which the treatment apparatus has for damaging or destroying the planar information carrier having a salient projection which engages in the depression when the plug unit of the device for supplying a medical fluid is connected to the socket unit of the treatment apparatus, thus causing the information carrier to be damaged or destroyed and thus to become unusable. 
     In an exemplary embodiment which is a particular preference, the depression is a groove in the portion of the plug unit, which groove is open at least one end and extends parallel to the axis of the plug unit, which axis defines the direction in which the plug unit is plugged into the socket unit of the treatment apparatus. When the plug unit is plugged into the socket unit, the salient projection is thrust into the groove, as a result of which the planar information carrier is sure to be destroyed without any great force being applied. 
     The means for detecting re-use of the device for supplying a medical fluid preferably have a unit for reading information on the planar information carrier and an analysing unit which is so designed that a signal indicating re-use is generated when the read-out of information is faulty after the destruction of the information carrier. What a faulty read-out also means in this case is that the information cannot be read at all, which should be the case after the information carrier has been destroyed or damaged. 
     If the apparatus for filling the device for supplying a medical fluid already has a reader, in order for example to read characteristic information about the fluid from a machine-readable code, the means for detecting re-use can be implemented without any further ado as to equipment 
     A further exemplary embodiment of the filling apparatus which is a particular preference provides a control unit for controlling the filling process which is so designed that the initiation of the filling process is prevented if the analysing unit generates the signal indicating re-use. 
     The socket unit of the filling apparatus and the plug unit of the device for supplying a medical fluid are preferably so designed that even the making of a flow-permitting connection between the socket unit and the plug unit is prevented. It is however also possible for the feeding of the medical fluid from the filling apparatus into the device for supplying the fluid to be prevented. 
     To make the flow-permitting connection, the socket unit has at least one connecting piece, whereas the plug unit has at least one connector, a fluid-tight connection being able to be made when the connecting piece is connected to the connector. In a preferred exemplary embodiment, the socket unit has a first connecting piece for the connection of a first connector of the plug unit and a second connecting piece for the connection of a second connector of the plug unit, thus enabling a first flow-permitting connection to be made for feeding in fresh treatment fluid and a second flow-permitting connection to be made for feeding out used treatment fluid. 
     If the device for supplying a medical fluid is used not only to supply fresh fluid but also to receive used fluid, the apparatus for filling the device for supplying a medical fluid can also be used to empty the device for supplying fluid. When this is the case it is only the process of filling with fresh fluid that is prevented. When it has already been used, the device is however still to be able to be emptied by the filling apparatus. 
     In the simplest case the device for supplying medical fluids may be a canister or bag which has the plug unit, being for example a bag having a plug. 
     Exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a highly simplified schematic view of a device for supplying a medical fluid, and particularly dialysis fluid, together with a blood treatment apparatus and an apparatus for filling the device for supplying dialysis fluid. 
         FIG. 2  is a perspective view of the plug unit of the device for supplying dialysis fluid and of the socket unit of the blood treatment apparatus shown in  FIG. 1 . 
         FIG. 3  is a view in section of the plug unit and socket unit shown in  FIG. 2 , in which the plug and socket units are not connected together. 
         FIG. 4  is a view in section of the plug unit and socket unit shown in  FIG. 2 , in which the socket unit has been prepared to have the plug unit connected to it. 
         FIG. 5  is a section through the plug unit and socket unit shown in  FIG. 2 , in which the plug unit is loosely inserted in the socket unit. 
         FIG. 6  is a section through the plug unit and socket unit shown in  FIG. 2 , in which the plug unit is connected to the socket unit, thus making the flow-permitting connections. 
         FIG. 7  is a perspective view of the plug unit of the device for supplying dialysis fluid and of the socket unit of the apparatus for filling the device for supplying dialysis fluid. 
         FIG. 8A  shows the socket unit shown in  FIG. 7  when prepared for the initiation of a flushing process. 
         FIG. 8B  shows the socket unit shown in  FIG. 7  during the flushing process. 
         FIG. 9  is a view in section of the plug unit and socket unit shown in  FIG. 7  before the said plug unit and socket unit are connected together. 
         FIG. 10  is a view in section of the plug unit and socket unit shown in  FIG. 7  in which the said plug unit is fitted loosely onto the said socket unit. 
         FIG. 11  is a section through the plug unit and socket unit shown in  FIG. 7  in which the said plug unit and socket unit are connected together to make the flow-permitting connections. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a highly simplified schematic view of a device  1  for supplying a medical fluid and in particular dialysis fluid, and of a blood treatment apparatus  2  and an apparatus  3  for filling the device for supplying dialysis fluid. The blood treatment apparatus  2  may be an extra-corporeal dialysis apparatus or an apparatus for peritoneal dialysis. In the present exemplary embodiment, the blood treatment apparatus  2  is a dialysis apparatus which has a dialyser  4  which is divided into a blood chamber  6  and a dialysis-fluid chamber  7  by a semi-permeable membrane  5 . A blood infeed line  8  runs from the patient to the blood chamber  6  of the dialyser  4  while a blood return line  9 , into which a blood pump  10  is connected, runs from the blood chamber  6  to the patient. Together with the blood chamber  6 , the blood infeed and return lines  8 ,  9  form the extra-corporeal blood circuit I of the dialysis apparatus  2 . 
     Fresh dialysis fluid is conveyed from a dialysis-fluid reservoir  11 , through a dialysis-fluid infeed line  12  into which a dialysis-fluid pump  13  is connected, to the dialysis-fluid chamber  7  of the dialyser  4 , while used dialysis fluid flows out of the dialysis fluid-chamber through a dialysis-fluid outfeed line  14 . A dialysis-fluid reservoir is not essential however. The dialysis fluid supplied may equally well be fed direct to the dialysis-fluid chamber. 
     The device  1 , which has two bags or canisters  15 A and  15 B in the present exemplary embodiment, is used to supply fresh dialysis fluid. The two bags or canisters  15 A,  15 B form a unit  15 , the bag  15 A being filled with fresh dialysis fluid before the dialysis treatment and the bag  15 B being empty. 
     From the dialysis-fluid bag  15 A, an infeed line  16  runs to one connection  17   a  of a plug unit A, while an outfeed line  18  runs from the other connection  17   b  of the plug unit A to the empty bag  15 B. 
     To supply dialysis fluid, the plug unit A is connected before the treatment to a socket unit B which is provided on the blood treatment apparatus  2 , thus enabling fresh dialysis fluid to be fed through the infeed line  16  to the dialysis-fluid reservoir  10  and used dialysis fluid to be feed out through the outfeed line  18 . 
     The device  1  for supplying dialysis fluid is filled with fresh dialysis fluid at apparatus  3 . The device  2  for supplying dialysis fluid can also be emptied by the filling apparatus  3 . The fresh dialysis fluid can be produced on-line in the filling apparatus  3  from water and dialysis fluid concentrate. Fresh dialysis fluid may however also be fed in from an internal or external source of dialysis fluid. Used dialysis fluid can be collected in an internal or external reservoir or discarded at a discharge. 
       FIG. 1  shows an exemplary embodiment in which a tank  20 A is used to hold fresh dialysis fluid and a tank  20 B to receive used dialysis fluid. The lines and pumps required are not shown in the highly schematic representation. As well as this, the device  1  for supplying dialysis fluid also has a control unit ( 80 ) by which all the components of the device  1  are controlled to connect the device for supplying a dialysis fluid to the filling or emptying apparatus and to fill and empty the device for supplying dialysis fluid, as will be described in detail below. 
     The apparatus  3  for filling and emptying the device  1  for supplying fresh dialysis fluid and for receiving used dialysis fluid has a socket unit B′ to which the plug unit A of the device  1  for supplying dialysis fluid is connected. The socket unit B of the blood treatment apparatus  2  and the socket unit B′ of the filling or emptying apparatus may be of identical or different forms. In the present exemplary embodiment the socket units B and B′ are of different forms. However, both the socket units B and B′ are so designed that fluid-tight flow-permitting connections in both directions for fresh and used dialysis fluid can be made to the two items of apparatus  2  and  3  with the plug unit A of the device  1  for supplying dialysis fluid. 
     As well as this, the filling or emptying apparatus  3  has a control unit  80  for controlling the filling and emptying processes and a reader  81  for reading a machine-readable code from a planar information carrier which is provided at the plug unit A of the device  1  for supplying dialysis fluid. The filling or emptying apparatus  3  also has an analysing unit  82  by which the information read from the information carrier can be analysed. The information may for example be information on the composition or amount of the medical fluid supplied. The analysing unit also enables errors to be detected by which the faulty read-out of a code is detected. In the event of the read-out of the code being faulty following destruction of the information carrier, which includes the event of a code not being able to be read out at all, the analysing unit  82  generates a control signal which the control unit  80  receives. If the control unit  80  receives the control signal, it prevents the filling process from being initiated. The initiation of the filling process is preferably prevented by the fact that a flow-permitting connection is not automatically made between the plug unit A of the device  1  for supplying dialysis fluid and the socket unit of the filling or emptying apparatus  3 . It is however also possible for the pumps (not shown) involved in the filling process not to be started or the valves (not shown) not to be opened. 
     In what follows, the plug unit A of the device  1  for supplying dialysis fluid will be described in detail by reference to  FIGS. 2 to 6 , together with the socket unit B of the blood treatment apparatus  2 . 
       FIG. 2  is a perspective view of the plug unit A and the socket unit B, while  FIGS. 3 to 6  show the plug and socket units A, B in section. 
     The socket unit B of the blood treatment apparatus  2  is preferably part of a treatment cassette (not shown) which is interchangeable. The socket unit B may however also be part of a non-interchangeable unit. The socket unit B has an outer flange portion  21  which is screwed to the housing wall  22  of the treatment cassette or blood treatment apparatus or it may be integral with the wall. The outer flange portion  21  may for example be screwed to the wall by screws (not shown) or it may be one common injection moulded part with the wall. Projecting from the outer flange portion  21  are two cylindrical connecting parts  23 ,  24  which are arranged in a common plane on the two sides of the central axis  58  of the socket unit. The cylindrical connecting parts  23 ,  24  concentrically surround respective connecting pieces  25  and  26 , the connecting piece  25  being used to feed in fresh dialysis fluid and the connecting piece  26  to feed out used dialysis fluid. 
     The plug unit A of the device  1  for supplying fresh dialysis fluid and receiving used dialysis fluid has corresponding connectors  27 ,  28  which will be connected to the connecting pieces  25 ,  26  with a fluid-tight seal. The plug unit A has a plug body  29  which connects the two connectors  27 ,  28 . The plug body  29  has an infeed passage  30  which is connected to one connector  27  and an outfeed passage  31  which is connected to the other connector  28 . The infeed line  16  of the device  1  for supplying fresh dialysis fluid and receiving used dialysis fluid is connected to the connection  17   a  to the infeed passage  30  and its outfeed line  18  is connected to the connection  17   b  to the outfeed passage  31 . Situated between the two connectors  27 ,  28  is a projecting piece  32  with which a connection which at first is only loose can be made between the plug unit A and the socket unit B. The projecting piece  32  has a plurality of latching members  33  which are arranged to be circumferentially distributed and which are integrally formed on one end of the plug body  29 . Formed on the outer sides of the free ends of the latching members  33  are latching noses  34 . To protect them against physical contact, the connectors  27  and  28  have sleeves  76  and  77  which are fitted onto and latch into the connectors  27 ,  28  on the plug body  29 . The connectors  27 ,  28  are closed off by respective septums, which are preferably slit, or membranes  35 ,  36 , which will be pierced by the connecting pieces  25 ,  26  of the socket unit. 
     Between the two connectors  27  and  28 , the plug body  29  has a portion  83  in whose outer side there is a groove  85  which extends from the front end of the portion  83  to its rear end, parallel to the axis which defines the direction in which the plug unit A is plugged into the socket unit B, which means that the groove  85  is open at both ends ( FIG. 3 ). Applied to the portion  83  is a planar information carrier  86  which hides the groove  85 . The information carrier  86  is a thin substrate, such as a film or paper for example, on which a matrix code is printed. 
     The socket unit B of the blood treatment apparatus  2  has an outward pointing portion  87  of its main body which is provided on the inside with a salient projection  88 . The longitudinally extending groove  85  in the portion  83  and the salient projection  88  on the portion  87  of the main body are so arranged that the salient projection  88  engages in the groove  85 , which is open at the front end, when the plug unit A is plugged into the socket unit B. The information carrier  86  is thus destroyed when the plug unit is connected to the socket unit. Because the salient projection  88  also extends parallel to the axis which defines the direction in which the plug unit A is plugged into the socket unit B, the projection  88  also acts a guiding piece for the plug unit when it is plugged into the socket unit. 
     If the plug unit A of the device  1  for supplying fresh dialysis fluid and receiving used dialysis fluid, which latter is intended for once-only use, is connected into the socket unit B′ of the filling or emptying apparatus  3 , the device  1  can only be emptied, but not refilled, because the information carrier  86  has been destroyed, as has been described by reference to  FIG. 1 . 
     Mounted in the centre of the flange portion  21  of the socket unit B is a cylindrical guiding piece  37  which extends through a hole  38  in the housing wall  22 . Guided to be longitudinally displaceable in the guiding piece  37  is a tubular receiving piece  40  which has a front portion  41  and a rear portion  42 . A drive unit  43  is provided to displace the tubular receiving piece  40  in the cylindrical guiding piece  37 . In the present exemplary embodiment, the drive unit  43  is an electric motor driven spindle drive which has a linear motor  44  and a spindle  45 , which latter is connected to the rear portion  42  of the receiving piece  40 . The receiving piece  40  is thrust out of the guiding piece  37  and retracted into the guiding piece by the extension and withdrawal of the spindle  45 . 
     Provided in the interior of the front end of the front portion  41  of the receiving piece  40  are a plurality of recesses  46  which are arranged to be circumferentially distributed and which are of a form such that the latching noses  34  on the latching members  33  of the projecting piece  32  on the plug unit A latch into the recesses  46  when the projecting piece  32  is inserted in the receiving piece  40 , a process which will be described in detail below. 
     The socket unit B has means by which it is detected that the projecting piece  32  is inserted in the receiving piece  40 . These means have a sensing member  47 , in the form of a tubular body, which is guided to be longitudinally displaceable in the tubular receiving piece  40 . The tubular sensing member  47  is pre-loaded by a spring  48  which is mounted in the rear portion  42  of the receiving piece  40 . A limit to the movement of the sensing member  47  in the longitudinal direction is set by a stop member  49  which is merely indicated and which is guided in a slot (not visible in the present plane of section) which is provided in the receiving piece  40 . 
     To detect the projecting piece  32  in the receiving piece  40 , the socket unit B has means by which it is detected whether the front end of the sensing member  47  is flush with the front end of the receiving piece  40  ( FIG. 3 ) or whether it has been pushed back into the receiving piece in opposition to the pre-loading from the spring  48 . This is the case when the projecting piece  32  is inserted in the receiving piece  40 . 
     The socket unit B also has a body  50  in pin form which is arranged in an immovable position, inside the tubular sensing member  47 . The body  50  in pin form may for example be locked by a pin  39  which extends through slots (not shown in the plane of section) in the sensing member  47  and the receiving piece  40  and into the guiding piece  37 . 
     In what follows, it will be described in detail how the plug unit A is connected to the socket unit B. 
       FIG. 3  shows the starting position, in which the socket unit B is locked. In this position, the spindle  45  of the linear motor  43  is withdrawn, as a result of which the receiving piece  40  and the sensing member  47  are retracted and the body  50  in pin form thus projects from the receiving piece. The body  50  in pin form thus prevents the projecting piece  32  from being inserted in the receiving piece  40 . 
       FIG. 4  shows the position of the receiving piece  40  and the sensing member  47  in which the spindle  45  of the linear motor  44  is extended and the receiving piece  40  and the sensing member  47  are advanced outwards out of the guiding piece  37 . In this position the body  50  in pin form, which is connected to the guiding piece  37 , is retracted sufficiently far for the projecting piece  32  on the plug unit A to be able to be inserted in the receiving piece  40 . 
       FIG. 5  shows the projecting piece  32  on the plug unit A when fitted into the receiving piece  40  of the socket unit B. When the projecting piece  32  is inserted in the receiving piece  40 , the latching noses  34  on the latching members  33  latch into the recesses  46  in the receiving piece  40  by a snap-in action. The plug unit A is held loosely to the socket unit by this means. However, the flow-permitting connection has not been made yet in this case, because the connecting pieces  25 ,  26  of the socket unit B have not yet been connected to the connectors  27 ,  28  of the plug unit A. In this position the infeed and outfeed passages  30 ,  31  in the plug unit are still closed off with a fluid-tight seal by the membranes  35 ,  36 . 
     When the projecting piece  32  is inserted in the receiving piece  40 , the sensing member  47 , which is guided to be longitudinally displaceable in the receiving piece, is pushed back into the receiving piece  40  by the latching members  33  of the projecting piece  32  in opposition to the resilient force of the spring  48 . The withdrawn position of the sensing member  47 , which is shown in  FIG. 5 , is sensed by means which are not shown, such for example as electrical contacts which are closed or a light barrier, as a result of which the drive unit  43  is started. The linear motor  44  now withdraws the spindle  45 , and the receiving piece  40  and the sensing member  47  are thus retracted. 
       FIG. 6  shows the position of the receiving piece  40  when the spindle  45  of the linear motor  44  is completely withdrawn and the receiving piece  40  and the sensing member  37  are fully retracted. As the receiving piece  40  is retracted, the body  50  in pin form is advanced into the projecting piece  32 , as a result of which the latching noses  34  on the latching members  33  of the projecting piece  32  are secured in the recesses  46  in the receiving piece  40 . The projecting piece  32  is thus locked in the receiving piece  40 . The locking of the projecting piece  32  in the receiving piece  40  takes place simultaneously with the relative movement of the connecting pieces  25 ,  26  and the connectors  27 ,  28 . 
     In the position shown in  FIG. 6 , in which the spindle  45  of the linear motor  44  is fully withdrawn, the two connecting pieces  25 ,  26  and the two connectors  27 ,  28  are connected together with a fluid-tight seal. The locking of the projecting piece  32  in the receiving piece  40  on the one hand ensures that the plug unit A, which at first was only loosely inserted in the socket unit B, can be drawn onto the socket unit in opposition to the forces which arise, and on the other hand prevents the plug unit from being able to detach from the socket unit once the flow-permitting connections have been made. The fluid-tight and non-releasable connection between the plug unit A and socket unit B is thus made automatically once the plug unit has been loosely inserted in the socket unit. 
     The unlocking of the plug unit A from the socket unit B takes place in the reverse order from the locking of the plug unit to the socket unit. For this purpose, the drive unit  43  is started again. This may for example be done by pressing a button or the like. When the spindle  45  of the linear motor  44  is extended again, the receiving piece  40  and the sensing member  47  slide forward again over the body  50  in pin form, as a result of which the locking of the latched connection between the projecting piece  32  and receiving piece  40  is released. At the same time, the connecting pieces  25 ,  26  are disconnected from the connectors  27 ,  28 . The plug unit A is thus situated in the starting position ( FIG. 5 ) again, in which the plug unit is still held loosely on the socket unit. This prevents the plug unit from being able to drop easily off the socket unit. 
       FIGS. 7-11  show an alternative exemplary embodiment B′ of the socket unit which is provided on the apparatus  3  for filling the device  1  for supplying the dialysis fluid. Basically, this alternative exemplary embodiment may equally well be provided on the blood treatment apparatus  2 . It is however also possible for the exemplary embodiment which was described by reference to  FIGS. 2 to 6  to be provided on the filling apparatus  3 . The alternative exemplary embodiment B′ of the socket unit will be described in detail in what follows. 
       FIG. 7  is a perspective view of the alternative exemplary embodiment B′ of the socket unit together with the plug unit A. Both the exemplary embodiments B and B′ of the socket unit can be connected to the same plug unit A, thus enabling the device  1  for supplying dialysis fluid to be connected on the one hand to the apparatus  3  for filling and emptying and on the other hand to the blood treatment apparatus  2 . 
     The two exemplary embodiments of the socket unit differ from one another in particular in that, when the plug unit A is being connected to the socket unit B to make the flow-permitting connections, the connectors  27 ,  28  of the plug unit A are drawn automatically onto the connecting pieces  25 ,  26  of the socket unit B ( FIGS. 2 to 6 ) by moving the plug unit A, whereas in the alternative exemplary embodiment B′ of the socket unit the connecting pieces of the socket unit are moved into the connectors  27 ,  28  of the plug unit A, in which case the plug unit A is not moved. What is more, the alternative exemplary embodiment B′ of the socket unit envisages the closing-off of the two connecting pieces or the making of a flow-permitting connection between the connecting pieces for a flushing process without the plug unit A and socket unit B′ being connected together. 
     The socket unit B′ has a housing body  51  which is inserted in a wall  52  of the housing of the filling apparatus  3  ( FIG. 7 ). The housing body  51  has a central opening  53  in which the receiving piece  57  for the projecting piece  32  of the plug unit A is arranged ( FIG. 9 ). In contrast to the exemplary embodiment which was described by reference to  FIGS. 2-6 , the receiving piece  57  of the socket unit B′ is not guided to be displaceable in the direction defined by the longitudinal axis  58  of the socket unit B′ but is mounted to be rotatable on the longitudinal axis  58  by means of a bearing  59  which is inserted in the central opening  53  in the housing body  51 . The receiving piece  57  is rotated by a drive unit which is not shown. 
     The receiving piece  57  has a front portion  60  which extends out of the housing body  51  and a rear portion  61  which extends into the housing body  51 , the front portion  60  being of a larger inside and outside diameter than the rear portion  61 . Provided on the inside of the front end of the front portion  60  of the receiving piece  57  are the recesses  62  which are arranged to be circumferentially distributed and into which the latching noses  34  on the latching members  33  of the projecting piece  32  latch when the plug unit A is fitted loosely onto the socket unit B′. 
     Guided to be longitudinally displaceable in the tubular receiving piece  57  is the sensing member  63 , which takes the form of a tubular body and which is pre-loaded by a spring (not shown) so that the sensing member  63  is pushed back in opposition to the loading from the spring when the projecting piece  32  is inserted in the receiving piece  57 . 
     Guided in the tubular sensing member  63  is the body  64  in pin form for locking the projecting piece  32  in the receiving piece  57 . The body  64  in pin form can be advanced in the longitudinal direction of the axis  58  and retracted again, to respectively lock and release the projecting piece  32  in the receiving piece  57 , by a drive unit (not shown). 
     In the alternative exemplary embodiment B′ of the socket unit, the connecting pieces  65 ,  66  are mounted in cylindrical openings  67 ,  68  in a connecting part  69  which is guided to be longitudinally displaceable in the housing body  51 , thus enabling the connecting pieces  65 ,  66  to be advanced out of and retracted into the housing body  51 . The drive unit for advancing and retracting the connecting part  69  having the connecting pieces  65 ,  66  is not shown in the drawings. 
       FIG. 9  shows the socket unit B′ in the position in which the plug unit A is fitted loosely onto the socket unit B′. The body  64  in pin form is retracted into the receiving piece  57  and the latching members  33  of the projecting piece  32  which have the latching noses  34  are thus able to latch into the receiving piece  57  which has the recesses  62 . 
       FIG. 10  shows the position in which the plug unit A is fitted loosely onto the socket unit B′, with the projecting piece  32  latched into the receiving piece  57 . The plug unit A is held only loosely in this case without the flow-permitting connections being made. 
     The position of the sensing member  63  is once again monitored. Because the sensing member  63  has been pushed back by the projecting piece  32 , it is detected that the plug unit A has been loosely fitted. When the plug unit is loosely fitted, the drive unit (not shown) is started, as a result of which the body  64  in pin form is advanced in the receiving piece  57 . As a result, the connection between the projecting piece  32  and receiving piece  57 , which at first was only loose, is now locked. At the same time, the connecting part  69  having the two connecting pieces  65 ,  66  is advanced out of the housing body  51 . It is also possible for the body  64  in pin form and the connecting part  69  to be connected together and to be moved in unison by a drive unit. The displacement of the connecting part  69  and the two connecting pieces  65 ,  66  causes the connecting pieces  65 ,  66  to pierce the membranes  35 ,  36  of the plug unit A, as a result of which the fluid-tight connections are made between the connecting pieces and the connectors. It is true that there is, once again, a relative movement between the connecting pieces  65 ,  66  and the connectors  27 ,  28 . However, in this exemplary embodiment it is not the plug unit A itself which is moved. Because the plug unit A is firmly seated on the socket unit B′ once the projecting piece has been locked to the receiving piece, the forces which occur when the plug and socket units are connected together can be absorbed. The connection of the plug unit to the socket unit thus once again takes place automatically. 
     The release of the plug unit A from the socket unit B′ takes place in the reverse order. For this purpose, the body  64  in pin form is retracted in the receiving piece  57 , and the connecting part  69  and the connecting pieces  65 ,  66  are retracted in the housing body  51 , as a result of which the connection between the projecting piece  32  and receiving piece  57  is unlocked and the connecting pieces  65 ,  66  are drawn out of the connectors  27 ,  28 . The unlocking may take place simultaneously with the drawing back of the connecting pieces or prior to the said drawing back of the connecting pieces. 
     The alternative exemplary embodiment B′ of the socket unit has a means  70  for closing off the two connecting pieces  65 ,  66 , or for making a flow-permitting connection between the two connecting pieces  65 ,  66  to enable a flushing process to be carried out with a flushing solution ( FIG. 7 ;  FIG. 8A  and  FIG. 8B ). The means  70  has two connectors  71 ,  72  which are arranged at the same distance from one another as the connectors  27 ,  28  of the plug unit A and which are of the same form as the connectors of the plug unit. The two connectors  71 ,  72  are closed off at a rear end in a flushing piece  73  or are connected to make a flow-permitting connection in the flushing piece  73 . 
     The flushing piece  73  has semi-circular indentations  74 ,  75  on the two opposite sides on which the connectors  71 ,  72  are not arranged. The flushing piece  73  having the connectors  71 ,  72  is connected to the front portion  60  of the receiving piece  57  of the socket unit B′. For this purpose, the flushing piece  73  has a central opening  89  through which the front portion  60  of the receiving piece  57  extends ( FIG. 9 ). Because the receiving piece  57  is mounted to be rotatable on the longitudinal axis  58 , the flushing piece  73  too and the connectors  71 ,  72  can be rotated on the longitudinal axis  58  as a result of the receiving piece  57  being rotated by the drive unit (not shown). 
       FIG. 7  shows the flushing piece  73  having the connectors  71 ,  72  in the position in which the plug unit A can be fitted onto the socket unit B′. In this position, the semi-circular indentations  74 ,  75  are situated in front of the connecting pieces  65 ,  66  of the socket unit B′, while the connectors  71 ,  72  are positioned in a plane which is perpendicular to the plane in which the connecting pieces  65 ,  66  are positioned. 
     To initiate the flushing process, the flushing piece  73  having the connectors  71 ,  72  is pivoted through 90° as a result of the receiving piece  57  being rotated by the drive unit (not shown), and the connectors  71 ,  72  are thus situated in front of the connecting pieces  65 ,  66 . However, this means that the connecting pieces are not yet closed off or that a flow-permitting connection has not yet been made between the connecting pieces ( FIG. 8A ). The connecting part  69  having the connecting pieces  65 ,  66  is then advanced out of the housing body  51  and the connectors  65 ,  66  are thus forced into the membranes of the connectors  71 ,  72 . This makes a fluid-tight connection between the connecting pieces  65 ,  66  of the socket unit B′ and the connectors  71 ,  72  and the two connecting pieces  65 ,  66  are thus closed off or short-circuited by means of the flushing piece ( FIG. 8B ). On completion of the flushing process, the connecting pieces  65 ,  66  are retracted again and the flushing piece  73  having the connectors  71 ,  72  is rotated back to the starting position ( FIG. 7 ). 
     The flushing piece  73  of the socket unit (B′), and the plug body  29  of the plug unit A, are of asymmetrical forms and the plug unit A can thus only be plugged into the socket unit (B′) when in the correct position shown in  FIG. 7 . For this purpose, the flushing piece  73  has a U-shaped projection  78  on the outer side opposite the plug body, while the plug body  29  has a projection  79  on the outer side opposite the flushing piece. The projection  79  is so arranged that it collides with the projection  78  if the plug unit A is plugged into the socket unit (B′) in a position in which it is rotated through 180°. 
     The particular design of the means  70  for closing off or for making the flow-permitting connection forms part of the socket unit B′. There is no need for a separate plug or the like. The socket unit B′ allows fully automatic control both of the connection of the plug unit A to the socket unit B′ and of the initiation of the flushing process, thus simplifying the handling process as a whole. Because the insertion of the plug unit in the socket unit is detected, the filling process or emptying process can be initiated automatically. The filling process may however also be prevented if the information carrier  86  on the plug unit A is destroyed. The control unit  80  of the filling apparatus  3  preferably prevents the connecting pieces  65 ,  66  of the socket unit B from being extended to make a flow-permitting connection. After the filling or emptying, the plug unit can be released automatically. The same is true of the flushing process. When the device  1  for supplying dialysis fluid is connected to the dialysis apparatus  2 , the filling of the fluid reservoir  10  can also be started automatically by the insertion of the plug unit A in the socket unit B of the dialysis apparatus.