Abstract:
A syringe for connection to a fluid container containing fluid to be discharged comprises a syringe barrel with a plunger moving therein, and a discharge outlet, through which fluid contained in the fluid container is dischargeable by actuation of the plunger, said syringe barrel being connected with the fluid container port and the discharge outlet via a fluid channel system, and a valve mechanism being provided in the fluid channel system, allowing the syringe barrel to be filled with fluid from the fluid container and to then discharge said fluid through the discharge outlet, wherein the valve mechanism comprises a valve member which is movable between first and second positions, said valve member, in said first position, allowing fluid flow from the fluid container to the syringe barrel and simultaneously blocking fluid flow from or to the discharge outlet and, in said second position, allowing fluid flow from the syringe barrel to the discharge outlet while simultaneously blocking fluid flow from or to the fluid container.

Description:
RELATED APPLICATION 
   This application claims priority to German Patent Application No. 103 26 306.3 filed Jun. 11, 2003. 
   TECHNICAL FIELD 
   The invention relates to a syringe comprising a fluid container port for a fluid container containing fluid to be discharged, a syringe barrel with a plunger moving therein, and a discharge outlet, through which fluid supplied by actuation of the plunger in the fluid container port is dischargeable, said syringe barrel being connected with the fluid container port and the discharge outlet via a fluid channel system, and a valve mechanism being provided in the fluid container port, allowing the syringe barrel to be filled with fluid supplied at the fluid container port and to then discharge said fluid through the discharge outlet. 
   BACKGROUND OF THE INVENTION 
   Particularly in veterinary applications, syringes are known which allow a syringe barrel to be filled repeatedly from a fluid container and to discharge the drawn fluid manually from the syringe barrel. This allows repeated injections of a precisely predetermined volume, as in the case of, for example, serial vaccinations or treatments of animals, and does not require the cumbersome filling of the syringe from a separate fluid container. The prior art syringes comprise two check valves. A first check valve is located between the syringe barrel and the discharge outlet and is connected such that fluid flow is possible only from the syringe cylinder to the discharge outlet, but not a counterflow such as might occur when drawing fluid from the fluid container connected with the syringe. A second check valve allows a fluid flow from the fluid container to the syringe barrel when pulling back the plunger, but not when advancing the plunger. 
   Such valve system is known for different fluid container systems. In a first construction, a fluid container is attached directly to the syringe, so that stored fluid flows into the syringe barrel by advancing the plunger. For this purpose, the fluid container is provided with a suitable pressure compensation mechanism preventing a vacuum from being generated within the fluid container. In a second variant, the fluid is contained under pressure and, when suitably released, automatically flows into the syringe barrel while pushing back the plunger. It is known to conduct a stop detection in these types of pressurefillable syringes, so that, when the syringe has been emptied, i.e. when the plunger is maximally advanced into the syringe barrel, the syringe barrel is automatically refilled, pushing back the plunger. 
   In particular, in the aforementioned second type of syringes, which are filled via a fluid container connected therewith, there may occur, during a filling operation, an undesired discharge of fluid through the discharge outlet, which is generally caused by the response behavior of the two check valves. 
   Therefore, it is the object of the invention to improve a syringe of the aforementioned type such that undesired discharges of fluid no longer occur during filling of the syringe barrel. 
   SUMMARY OF THE INVENTION 
   This object is achieved by a syringe of the aforementioned type, wherein the valve mechanism comprises a valve member which is movable between first and second positions, said valve member, in said first position, allowing fluid flow from the fluid container port to the syringe barrel and simultaneously blocking fluid flow from or to the discharge outlet and, in said second position, allowing fluid flow from the syringe barrel to the discharge outlet while simultaneously blocking fluid flow from or to the fluid container. 
   Thus, the invention no longer uses two independent check valves, but the closing of the discharge outlet and the opening of a filling opening, through which the syringe barrel may be filled with fluid from the fluid container, is effected by means of one single valve member moving between two positions. Accordingly, the closing of the discharge outlet and the opening of the supply opening for fluid flowing into the syringe barrel is effected by one single valve member, so that the occurrence of problems with differently responding check valves, each equipped with independent valve members, is positively eliminated. Moreover, a considerable simplification is achieved, because only one valve is required, which now serves the function of the two valves present in the prior art. 
   A particularly simple and compact structure is achieved by arranging the valve member in an opening region where a discharge channel from the syringe barrel to the discharge outlet and a duct from the fluid container to the syringe barrel converge. Switching between the first and second positions may then be achieved even by a very small movement of the valve member. A particularly simple construction is achieved if the valve member is displaceable between both positions. 
   Many useful alternatives which allow the first and second positions to be realized are suitable for the design of the valve member. For example, the valve member may be embodied in the form of a disk provided with suitable bores. However, it is particularly simple to manufacture a valve member having a first sealing surface, which closes the discharge channel to the discharge outlet in the first position, and having a second sealing surface, which closes the duct from the fluid container in the second position. Such sealing surfaces are technically rather easy to realize and allow a structure of the valve member comprising only few parts. This, of course, automatically leads to a simple assembly and disassembly. The latter aspect is advantageous bearing in mind that easy cleaning is required, in particular, for veterinary syringes. 
   The embodiment of the valve mechanism according to the invention comprising only one single valve member may be further improved by additionally providing a third position of the valve member at which the syringe barrel, the fluid container port and the discharge outlet are not in fluid communication with each other. This allows replacement, for example, of a needle attached to the discharge outlet or of the fluid container. 
   The third position of the valve member represents kind of a rest position, wherein the three components, namely the fluid container port, the syringe barrel and the discharge outlet, are separated from each other. Therefore, it is advantageous to provide a biasing means which urges the valve member toward the third position. In order to enable use of the syringe, the biasing means may be provided with a releasing means. Actuation of the syringe is particularly simple if the biasing means urges the valve member toward the third position in such a way that the resulting bias can be overcome by actuating the syringe plunger, thus moving the valve member into the second position. A separate device releasing the bias exerted by the biasing means is then dispensible; the user merely needs to move the syringe plunger in the usual way and may thus overcome said bias and move the valve member from the third into the second position. 
   In a particularly convenient embodiment of the invention, the biasing means is provided such that, when drawing further fluid from the fluid container, which may be effected either by the aforementioned pressure-filling or mechanically, the bias is also overcome and the valve member moves from the third to the first position. 
   In this respect, a construction which is particularly convenient, because it can be realized as a technically simple and easy-to-clean construction, is achieved if the valve member comprises an upper part with the first sealing surface and a lower part with the second sealing surface, said upper and lower parts being displaceable relative to one another and being pushed apart into the third position by the biasing means. 
   In order to keep the valve member easily accessible for cleaning purposes, it is preferred to arrange the valve member in a valve chamber, which forms one seat each for the first and second sealing surfaces of the valve member and into which a fluid channel opens, which extends to the syringe barrel. The valve chamber then forms the aforementioned opening region into which the ducts from the fluid container port, from the discharge outlet and from the syringe barrel extend. 
   The advantageous operation of the valve member of the syringe according to the invention is put to favourable use, in particular, by connecting the fluid container with a pressurizing means, allowing the fluid to be pressurized in order to fill the syringe barrel with fluid. 
   In applications where a large number of injections is to be carried out, as is common, for example, in veterinary medicine or in animal breeding, syringes are provided which are connectable to a fluid container holding a large quantity of fluid and from which said fluid is automatically drawn into the syringe barrel as soon as all injections have been performed, i.e. as soon as the plunger abuts within the syringe barrel upon being maximally advanced. In this connection, it is known to provide a stop-detecting device which recognizes an abutment of the plunger within the syringe barrel and transmits a corresponding signal to a control unit which then causes the syringe barrel to be refilled from the fluid container. 
   In most cases, this is effected by providing for a suitable pressure increase within the supply duct from the fluid container to the syringe barrel, for example, by pressurizing the fluid in the fluid container or by opening a valve to the fluid container holding pressurized fluid. 
   Mechanical switches are suitable to detect the stop position. It is also known in the prior art to measure the position of the plunger within the syringe barrel by means of a magnetic field sensor which, attached to the housing of the syringe, senses a magnetic unit, which may be formed, for example, by the plunger rod provided with a suitable magnetic structure. In a known working solution, a rotatable magnet assembly, which is supported on the housing of the syringe barrel and whose angular position is sensed by a magnetic field sensor also attached to the housing, is driven by the plunger rod via a gear unit. 
   These approaches allow precise sensing of the plunger position. Therefore, they are intended for syringes whose plunger is to be advanced by a predetermined length using a motor, in order to discharge a predetermined amount of fluid. However, the expenditure required in this connection is not necessary at all in detecting the stop position of the plunger. Therefore, these concepts have not been successful for syringes in which it is merely required to detect the stop position of the plunger at the bottom of the syringe barrel. 
   Thus, it is envisaged according to the invention to provide the syringe with a position-sensing device for the plunger moving inside the syringe barrel and connected to a plunger rod, wherein at least one magnet is fixed in a stationary manner relative to the syringe barrel and a magnetic field sensor is attached to the plunger rod to sense the magnetic field of the magnet. 
   This construction solves the problem of easily detecting, at reduced expenditure, whether the plunger is located at its end position, fully advanced into the syringe barrel. In this connection, sensing is effected in a contact-free manner, so that wear caused by contact, which is inevitable in a mechanical stop switch, no longer occurs. 
   The arrangement in which the magnet is fixed in a stationary manner relative to the syringe barrel and the magnetic field sensor is attached to the plunger rod, which is the opposite of the prior art arrangement, enables a surprisingly simple solution, wherein the plunger rod may remain unchanged as with syringes having no position-sensing device, in particular, at the plunger or at the plunger portion where the plunger rod is located inside the syringe barrel when being maximally advanced. Complex designs or alterations of the plunger rod as required for known position-sensing devices using the magnetic principle can be dispensed with completely. 
   Contrary to conventional syringes, i.e. syringes operating without a position-sensing device, the plunger rod may remain completely unchanged by simply fitting the magnetic field sensor to the plunger rod at its end facing away from the plunger. In particular, a plunger rod extension carrying the magnetic field sensor may be used. In a particularly convenient further embodiment, the magnetic field sensor is directly connected with a circuit also attached to the plunger rod, said circuit processing the signal from the magnetic field sensor and emitting an output signal, which indicates whether the plunger is maximally advanced into the syringe barrel. Said circuit may be part of the plunger rod extension. 
   The described further embodiment of the circuit is further advantageous in that contacting is required only via three conductors; two of said conductors serve to supply power to the circuit and a third conductor transmits the output signal, which is preferably a binary signal. 
   The circuit may be of a particularly small construction, if the signal from the magnetic field sensor is, for a predetermined minimum field strength, greater than a threshold value, and the position and the coercive force of the magnet as well as the position of the magnetic field sensor at the end of the plunger rod are selected such that the signal from the magnetic field sensor exceeds the threshold value only if the plunger abuts inside the syringe barrel. The magnet, which is arranged in a stationary manner relative to the syringe barrel, as well as the magnetic field sensor comprising said circuit will then function in the manner of a reed contact. 
   In this embodiment, the arrangement of the magnet is to be selected to correspond to the sensitivity of the magnetic field sensors and to the circuit design. A particularly simple construction is achieved by arranging the magnet in the region of a plunger rod guide through which the plunger rod extends into the syringe barrel. 
   The signal from the magnetic field sensor makes it possible to very simply provide a control unit causing the syringe barrel to be filled when the output signal indicates a maximally advanced plunger in the syringe barrel. 

   
     DESCRIPTION OF THE DRAWINGS 
     The invention is explained in more detail below, by way of example and with reference to the drawings, wherein: 
       FIG. 1  shows a schematic sectional view of a veterinary syringe; 
       FIG. 2  shows an enlarged sectional view of the syringe of  FIG. 1  in the region of the valve mechanism, with a valve member being located in a first position, in which fluid flow from a fluid container port to a syringe barrel is possible and, at the same time, fluid flow from the syringe barrel to a discharge outlet is not possible; 
       FIG. 3  shows the same view as  FIG. 2 , wherein the valve member is now in a second position, in which fluid flow from the syringe barrel to the discharge outlet is possible and, at the same time, fluid flow between the fluid container port and the syringe barrel is blocked; 
       FIG. 4  shows the same view as  FIGS. 2 and 3 , with the valve member being in a third position, in which the supply duct to the fluid container port, the discharge outlet and the syringe barrel are not in fluid communication with each other; 
       FIG. 5  shows an enlarged representation of the end of a plunger rod of the syringe, said plunger rod having fitted thereon a circuit comprising a magnetic field sensor, and 
       FIG. 6  shows a circuit diagram for the circuit of  FIG. 5 . 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a veterinary syringe  1  in a sectional representation. The syringe  1  comprises a handle  2  having applied thereto a lever by which the syringe can be actuated. Actuation of the lever acts on a plunger  3  which is attached to a plunger rod  4  and moves inside a barrel  5 . The syringe further comprises a port  6  onto which a syringe needle may be fitted. A port  6  is screwed onto a syringe head  7  by means of an intermediate ring. On an opposite side, a barrel  5  is screwed into the head using a suitable gasket. Further, a supply duct  8  from a fluid container (not shown in  FIG. 1 ), which is connected to a fluid container port of the syringe head  7 , terminates in the syringe head  7  via a valve mechanism without a reference numeral in  FIG. 1 , which will be explained later. 
   A position-sensing device  9 , which is electrically connected via a signal cable and cooperates with a magnet  11  provided at the end of the handle  2  into which the syringe barrel is inserted, in order to detect, whether the plunger  3  is maximally advanced into the barrel  5 , i.e. whether the barrel  5  is empty, is fitted onto the end of the plunger rod  4  located opposite the plunger  3 . 
     FIG. 2  shows a detail of the syringe  1  of  FIG. 1  in the region of the syringe head  7 . As can be seen, the barrel  5  is attached to the syringe head  7  by means of a gasket screwed into the syringe head  7 . The gasket has a bore and thus acts as a restrictor  12 . The thus-formed outlet through the restrictor  12  at the bottom of the barrel  5  opens into a barrel outlet  13  formed by a bore extending into a valve chamber  14 . The valve chamber  14  is formed by the syringe head  7  and a valve housing  15  screwed into the head. A discharge channel  16  for connection opens into the valve chamber  14 . In  FIG. 2 , a valve member  17  closes the discharge channel  16 . The valve member  17  comprises a lower part  18  having a sealing surface  19 , which is shown in  FIG. 2  in a position spaced apart from a valve seat  20 . 
   Thus, the valve chamber  14  is formed by a valve housing  15 , which is screwed into the syringe head  7  in a sealing manner, so that the valve chamber  14  is formed by the syringe head  7 , having a discharge channel  16  formed therein, extending toward the port  6 , and by the barrel outlet  13 , extending toward the barrel  5 , as well as by the valve housing  15 . 
   The valve seat  20  is part of a supply port  21 , which is formed in the valve housing  15  and which connects to a fluid container (not shown). In the position of the valve member  17  shown in  FIG. 2 , fluid can flow from the supply port  21 , past the sealing surface  19  and the valve seat  20 , to the barrel outlet  13  and, from there, through the restrictor  12  into the barrel. The discharge channel  16  is sealed, at the same time, by an upper part  22  of the valve member  17 , so that no fluid can flow to the port  6 . The upper part  22  is fitted on a plate  23 , which is attached to the lower part  18  of the valve member  17  by a ring  24 . Further, between said upper and lower parts, there extends a spring  25 , which biases the lower part  17  away from the upper part  22  together with the plate  23 , which has elastic properties. 
   The compressed shape of the valve member  17  shown in  FIG. 2 , in which the upper part  22  and the lower part  18  are pressed upon each other by the elastic force of the plate  23  and of the spring  25 , is achieved by pressurized fluid being supplied via the supply port  21 . Said fluid flows into the barrel  5 ; the discharge channel  16  is sealed by a nose  26  which is formed on the upper part  22  and is in sealing contact with a taper bore  27  of the discharge channel  16 . Since the barrel outlet  13  opens into the valve chamber  14  between the sealing surface  19  and the taper bore  27 , fluid flows from the supply duct  21  into the barrel  5 , i.e. the barrel  5  is filled from the fluid container, in the condition shown in  FIG. 2 . 
   In order to adjust the pressure required to compress the valve member  16  into the position shown in  FIG. 2 , an opening  28  is provided in the lower part  18 , through which fluid may also exert pressure on the bottom surface of the upper part  18 . For the same reason, the upper part  22  of the valve member  17  also comprises openings  29 , whose size is a decisive factor for the pressure exerted by the upper surface and required in order to leave the position of  FIG. 2 . 
     FIG. 2  shows a first position, in which fluid can flow from the fluid container port  21  to the barrel  5 , but not between the barrel  5  and the discharge outlet  6  or between the fluid container port  21  and the discharge outlet  6 . 
   In a second position, fluid flow is possible only between the barrel  5  and the discharge outlet  6 ; this position of the valve member  17  is shown in  FIG. 3 . It corresponds substantially to the position of  FIG. 2 , but now, the entire valve member  17  is still pressed down onto the valve seat  20  with the upper part  22  being pressed onto the lower part  18 . This condition is achieved if there is no more overpressure at the supply port  21 , but the plunger is being pushed forward inside the barrel  5 , so that pressurized fluid flows from the barrel outlet  13  and into the valve chamber  14 . The pressure acting on the upper part  22  of the valve member  17  has the effect, on the one hand, that the upper part  22  is pushed toward the lower part  18  and, on the other hand, that the sealing surface  19  of the lower part  18  comes to rest on the valve seat  20 . As a result, no fluid flow is possible from the valve chamber  14  to the supply port  21 . Instead, fluid flows from the barrel  5 , via the restrictor  12 , the barrel outlet  13  and the discharge channel  16 , to the port  6  and, from there, out of the syringe  1 . 
   If there is no increased pressure at the supply port  21  nor at the syringe barrel  5 , this will result in the third position of the valve member shown in  FIG. 4 . The spring  25  as well as the elastic plate  23  expand the valve member  17  in that the upper part  22  is pushed away from the lower part. As a consequence, the lower part  18  is seated against the valve seat  20  by its sealing surface  19  and seals the valve chamber  14  to the supply port  21 . Likewise, the nose  26  is seated in the taper bore  27  and blocks the discharge channel  16 . Thus, the barrel outlet  13  and, consequently, the barrel  5 , the discharge channel  16  (and also the port  6 ) as well as the supply port  21  (and the fluid container) are fluid-disconnected from each other. The valve member  17  may be moved either to the first position ( FIG. 2 ) or to the second position ( FIG. 3 ) by applying overpressure to the supply port  21  or by generating overpressure at the barrel outlet  13 . 
     FIG. 5  shows the position-sensing device  9  in an enlarged representation. The position-sensing device  9  emits a signal via the signal cable  10 , indicating whether the plunger  3  is fully advanced into the barrel  5 .  FIG. 5  shows the end of the barrel  5  located opposite the syringe head  7 , said end being held in a barrel reception  30  provided on the handle  2 . The barrel reception  30  further comprises a plunger rod guide  31 , by means of which the plunger rod  4  passes into the barrel  5 . 
   A bore  33  is provided in the end  32  of the plunger rod  4  located opposite the plunger  3 , said bore  33  receiving a printed circuit board carrier  34  which forms an extension of the plunger rod  4 . The printed circuit board carrier  34  holds a printed circuit board  35  provided with a Hall sensor  36  thereon, which senses the fields of three magnets, of which only one magnet  11  is shown in the sectional view of  FIG. 5 . The magnets are inserted in suitable bores in the area of the plunger rod guide  31 . 
   The Hall sensor  36  is connected with a circuit  37 , which is located on the printed circuit board  35  and also comprises an LED  38 , in addition to other components to be explained later. The LED  38  indicates whether the position-sensing device  9  is activated. The circuit  37  on the printed circuit board  35  comprising the Hall sensor  36  and the LED  38  is connected to the signal cable  10  via a plug connection  39 . 
     FIG. 6  shows the circuit diagram of the circuit  37 . The Hall sensor  36  of the circuit  37  is provided as an active component which is connected to a Gnd terminal  40  and a Vcc terminal  41  for power supply. The output of the Hall sensor  36 , which senses the magnetic field symbolized as H in  FIG. 6 , is applied to the gate of a FET  43  whose drain-source path extends from the potential of the Gnd terminal  40  to the base of a transistor T 1 . In a convenient realization, the Hall sensor  36  and the FET  43  are comprised in one component, and the transistor T 1  is, for example, of the BC547C type. 
   The base of the transistor T 1  further has a resistor R 3  applied thereto, having a resistance of, for example, 4.7 kΩ, whose other pole is on the potential of the Vcc terminal. The emitter of the transistor T 1  is applied to Gnd potential, whereas the collector is connected with a signal output  42 . In order to cause this signal output  42  to rise to Vcc during blocking of the transistor T 1 , the collector of the transistor T 1  is additionally connected to Vcc via a resistor R 4  (1 kΩ). 
   In order to allow a user to recognize whether the circuit  37  is supplied with supply voltage, i.e. whether the Hall sensor  36  can emit the required signal, the LED  38  is additionally connected with a suitable ballast resistor (e.g.  270 ), between Vcc and Gnd, so that a 10 mA current flows and the LED  38  lights up at Vcc=5 V. 
   Thus, in the circuit  37 , the Hall sensor  36  switches the base of the transistor T 1  to the potential of the Gnd terminal  40 , via the FET  43 , if the magnetic field H exceeds a certain threshold value. Said threshold value, and thus a non-conducting transistor T 1 , occurs when the plunger  3  is in the stop position inside the barrel  5 , i.e. when the barrel  5  has been emptied. Only then is the magnetic field H of the magnet  11  large enough to cause the Hall sensor  36  and, thus, the circuit  37  to switch over. If the plunger  3  is not in the stop position, the transistor T 1  is conducting, and the signal at the signal output  42  of the circuit  37  is on a low level. The same applies if the circuit is not activated, i.e. if no supply voltage is applied to the Vcc terminal  41 . The signal output  42  is then also on a low level, but now depending on the distance of the Hall sensor  36  from the magnet  11 . At the same time, the LED  38  does not light up. 
   However, if the plunger  3  is in the stop position, i.e. if it is fully advanced into the barrel  5 , the Hall sensor  36  is then approximated to the magnet  11 , such that the magnetic field H causes the Hall sensor  36  to switch over; the FET  43  switches through, thus blocking the transistor T 1 . The output signal  42  is on the level of the Vcc terminal  41 , i.e. high. 
   By monitoring the signal output  42 , a control unit (not shown) can detect an empty barrel  5 . A pressure increase at the supply port  21  then moves the valve member  17  into the first position shown in  FIG. 2  and the barrel  5  is refilled.