Abstract:
A fluid drainage device, for use in a closed wound drainage system, which includes a fluid-receiving volume having a bore, a piston in sealing contact with the bore, a prop extending from the piston and which is connected to an energy storage device, wherein the piston can be user-actuated between a first position, whereby energy is stored in the energy storage device, to a second position, whereby energy is released from the energy storage device, to increase the size and reduce the pressure of the volume, allowing fluid to flow from a conduit into the volume.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to the drainage of body fluids from a closed wound. 
         [0002]    The draining of fluid from a closed wound, particularly after surgery, is beneficial as it promotes healing and removes a build-up of fluid which would other otherwise remain in the body and which would increase the chances of infection. 
         [0003]    Various drainage systems have been proposed most of which operate through the use of a partial vacuum in order to promote the drainage of fluids. These drainage systems are usually in the form of compressive containers, electric vacuum machines or pre-charged disposable containers. 
         [0004]    Although these systems all drain fluid, they have varying degrees of efficacy and the manufacturing cost thereof can often be high. In some devices, a vacuum is not always constantly applied and a user must constantly check and re-adjust the device to ensure that the fluid is being drained effectively. Typically, the vacuum level is higher at the start of a working cycle of a device and lower at the end of the working cycle. This variation affects the fluid drainage rate. Some devices are also specific to the volume of fluid to be drained and it is often not possible to adjust this volume easily to suit a particular patient&#39;s needs. 
         [0005]    An object of the present invention is to provide a fluid drainage device, suited for use with a closed wound drainage system, which is cost effective to manufacture and which at least partially addresses the aforementioned issues. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention provides a fluid drainage device for use in a closed wound drainage system which includes a body with a cylindrical bore which defines at least part of a fluid-receiving volume, an inlet to the fluid-receiving volume, a piston in sealing contact with the bore which partly bounds the fluid-receiving volume inside the bore, the piston being movable between a first position and a second position, a piston rod which extends from the piston, an energy storage device engaged with the piston rod, a user-actuated handle mechanism which is movable relative to the body in a first direction, to allow the piston to move from the first position, whereby energy is stored in the energy storage device, to the second position, whereby energy is released from the energy storage device, thereby increasing the size of the fluid-receiving volume, reducing the pressure in the fluid-receiving volume and allowing fluid to flow from a suitable conduit through the inlet and into the fluid-receiving volume. 
         [0007]    The energy storage device may be compression spring. 
         [0008]    Preferably the spring constant of the compression spring is relatively invariable during movement of the piston between the first and second positions. 
         [0009]    Preferably the spring is formed from steel that is electro galvanized and blue passivated to prevent rust. 
         [0010]    The handle mechanism may include at least one threaded component which is movable to allow the energy storage device to be loaded with, or to release, energy. 
         [0011]    Preferably the handle mechanism includes an inner tubular member which is externally threaded and in which the piston rod and energy storage device are housed and an outer tubular member which is threadedly engaged with the inner tubular member such that rotation of the outer tubular member in a first direction causes the outer tubular member to move linearly along the inner tubular member, causing the energy storage device to release energy, thereby creating a vacuum or a region of reduced pressure and causing or allowing the piston to move to the second position. 
         [0012]    The handle mechanism may include indicating means, e.g. on a periphery thereof, to indicate the volume of fluid to be drained. 
         [0013]    As the fluid enters the fluid-receiving volume, the pressure in the fluid-receiving volume increases. The suction effect, exerted via this volume, thus decreases and ultimately a stage is reached, as determined by the setting of the indicating means, at which the fluid is no longer drawn through the inlet into the fluid receiving volume. 
         [0014]    In one form of the invention the inlet valve is a one-way valve, and the device has an outlet valve to allow the fluid in the fluid-receiving volume to be drained. 
         [0015]    The device may be formed from clear plastics material of any suitable kind. 
         [0016]    The device may include a formation to allow the body to be suspended from an overhead structure. 
         [0017]    In a preferred embodiment of the invention the piston is movable in the bore against a frictional force which is at a maximum value at the beginning of a working stroke of the piston and which is at a minimum value at an end of the working stroke of the piston and which decreases as the piston moves over its working stroke from the maximum value to the minimum value. 
         [0018]    The variation in the frictional force may be achieved in any appropriate way. The invention is not limited in this respect. However, in one approach, the shape of the bore is varied so that the frictional force reduces from the beginning of the working stroke towards an end of the working stroke. This may be achieved by increasing the cross-sectional area of the bore, preferably on a linear basis, from one end of the bore to an opposing end. Additionally, use may be made of an appropriate seal which is fitted to the piston and which provides a sealing interface between the piston and an opposing surface of the bore despite the change in dimension of the bore. 
         [0019]    In the device as described, an inlet to the volume, and an outlet from the volume, are positioned on the body at appropriate locations. Typically spring-loaded values are fixed to the inlet and outlet respectively. The outlet, which functions as a drain from the volume, has a relatively weak spring which acts on the valve. A difficulty which has been encountered is that, in use, the drain valve does not always seal properly. On the other hand the force exerted by the spring on the inlet valve can influence the vacuum which is induced in the volume. Variations in the vacuum affect the repeatability of operation of the drainage function. 
         [0020]    To address this problem, in one embodiment of the invention a single opening (inlet/outlet) is formed in the body to the fluid receiving volume. A valve, of compound construction, is connected to the opening. The valve has an inlet port and a drain port and is operable to connect the inlet port to the opening, and hence to the fluid receiving volume, so that the device can act in a drainage mode. Alternatively, the valve is operable to connect the drain port to the opening so that fluid from the fluid receiving volume can be expelled to waste, when required. 
         [0021]    The compound valve preferably manually actuable and is movable, e.g. rotatable, between a first limiting position at which the opening is connected to the inlet port and a second limiting position at which the opening is connected to the drain port. 
         [0022]    In use, the fluid drainage device is connected to a tube which extends from a wound to a receptacle i.e. the container body, in to which fluid is drained. It should be possible, with ease, to connect the body to a tube which could have one of a number of different sizes. This particular problem can be overcome by preselecting tubes of appropriate sizes or by making use of adaptors developed for the purpose. This however, is not necessarily an ideal approach for it can be time-consuming to implement and, additionally, a stock holding of tubes or adaptors of various sizes etc. must be established. 
         [0023]    This aspect can be addressed by providing a connector for use with the fluid drainage device which includes a first tubular member with a first section of constant external circular cross-section which is externally threaded and a second section which extends from the first section and which is tapered reducing in external size away from the first section, and a second tubular member with an internal passage, which has a first part where the passage has a constant cross-sectional area and is internally threaded so that the first part is threadedly engageable with the first section, and a second part which encloses a length of the passage which is tapered reducing in cross-sectional area moving away from the first part. 
         [0024]    The degree of taper of the second section may be substantially the same as the degree of taper of the passage enclosed in the second part. 
         [0025]    The first tubular member may be attached to the second tubular member by inserting the second section through the passage within the first part so that the second section then extends into the tapered passage in the second part. The first part may then be threadedly engaged with the first section. 
         [0026]    As the first part is further threaded onto the first section, the second section is caused to enter to a greater extent into the tapered passage of the second part. 
         [0027]    With the tubular members interengaged as described a gap is formed between opposing surfaces of the second section and of the second part. This gap, in cross-section, is annular and, viewed from one side, is tapered i.e. the gap generally conical in shape. The width of the annular gap, formed between opposing surfaces of the second section and the second part, is reduced as the first part is further threaded onto the first section. 
         [0028]    The first and second tubular members are preferably made from a plastics material. A requirement in this respect is that it should be possible, with relative ease, to sever the second section at an appropriate location and the second part at an appropriate location. This is done taking into account the size of a tube (internal diameter and external diameter) which is to be coupled to the connector. 
         [0029]    The connector suited for use with the fluid drainage device but its application is not limited to this specific implementation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    The invention is further described by way of examples with reference to the accompanying drawing in which: 
           [0031]      FIG. 1  shows a fluid drainage device according to one form of the invention, from one side and in cross-section—the right side thereof showing a piston inside a container body in a first position and the left side showing the piston in a second position inside a bore of the container body; 
           [0032]      FIG. 2  is similar to  FIG. 1  but illustrating another fluid drainage device according to the invention; 
           [0033]      FIG. 3  is a view on an enlarged scale and in cross-section of a portion of the device shown in  FIG. 2 ; 
           [0034]      FIG. 4  is a perspective view of a modified drainage device according the invention with a multiport or compound valve in a first position; 
           [0035]      FIG. 5  is similar to  FIG. 4  but with the valve in a second position; 
           [0036]      FIG. 6  is a plan view of the drainage device in  FIG. 4 ; 
           [0037]      FIG. 7  is a view of the drainage device in cross-section from one side taken on a line  7 - 7  in  FIG. 6 ; 
           [0038]      FIG. 8  is a perspective view from above of the drainage device of  FIG. 5  showing the valve in an exploded configuration; 
           [0039]      FIG. 9  is a perspective view, from below, of the arrangement of  FIG. 8 ; and 
           [0040]      FIGS. 10, 11, 12 and 13  respectively illustrate in cross-section and from one side a connector, which forms part of a preferred embodiment of a drainage device according to the invention, but wherein the connector is coupled to a flexible pipe or conduit which increases in diameter from  FIG. 10  to  FIG. 13  respectively. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0041]      FIG. 1  of the accompanying drawings shows a device  10  for use a fluid drainage system. The device has a container body  12  and a user-actuable handle mechanism  14  at a lower end of the body. A fluid inlet  16  is positioned on one side of a lid  18 . A fluid drainage outlet  20  is positioned on an opposing side of the lid. 
         [0042]    A formation  22  which allows the container body  12  to be suspended from overhead structure, not shown, is centrally located on the lid. 
         [0043]    The right and left ides of the drawing how the device  10  in cross section in different operative modes. 
         [0044]    The body  12  is cylindrical in shape and, internally, defines a cylindrical bore  26  with a smooth internal surface. A piston  28 , of complementary shape to the bore, is slidingly positioned inside the bore. The piston has an external seal  30  which ensures that an intimate seal established between the piston and the bore. A fluid-receiving volume  60  of variable size is defined by the position of the piston inside the bore. 
         [0045]    A piston rod  32  projects from the piston  28 . An energy storage device  34 , shown here in the form of a compression spring, is engaged with the piston rod. 
         [0046]    The handle mechanism  14  comprises an inner tubular member  36 , fixed to the body, which is threadedly engaged with an outer tubular member  38  which is rotatable in relation to the inner tubular member. In order to achieve this, the inner tubular member has external threads  40  and the outer tubular member has internal threads  42  which are engaged with the threads  40 . 
         [0047]    An end  50  of the piston rod  32  bears against and is connected to the piston and is held in place by complement formations  52  on the inner tubular member. 
         [0048]    The spring  34  is housed within the user actuable handle mechanism. It reacts against an end  36 A of the ember  36  and exerts a force on an end  32 A of the rod  32  which urges the piston  28  in a direction A, shown on the left side of  FIG. 1 . 
         [0049]    The inner tubular member  36  is held captive to the outer tubular member  38  through interengagement of the threads  40  and  42 . When the outer tubular member is fully threaded into the inner tubular member as shown in the right side of  FIG. 1 , an end surface  58  thereof abuts an end surface  64  of the inner tubular member. 
         [0050]    In use, an elongate flexible drainage conduit  90 , shown on the right side of  FIG. 1 , is connected to the inlet  16 . A free end of the conduit is positioned, as is known in the art, in a body cavity from which fluid is to be drained (not shown). At this stage the outer tubular member  38  is fully engaged with the inner tubular member and the spring  34  is loaded with energy. The piston  28  is in the first position shown on the right side of  FIG. 1  and the volume  60  has a minimum value. 
         [0051]    Upon rotation in a first direction relative to the inner member  36 , the outer tubular member  38  rides over the threads  40  and moves in an axial direction away from the body  12 . The handle  14  is then in an extended configuration as shown in the left side of  FIG. 1  and, as a consequence, the spring  34  releases energy thereby pulling the piston  28  away from the lid  18  towards a base of the container body. 
         [0052]    Indicating markings  62  are provided on an outer surface of the inner member  36 . The markings show the volume of fluid to be drained. This volume can be adjusted by appropriately rotating the outer member  38 . Once quantity of fluid has been drained, corresponding to the indicated volume, the piston  28  will have moved to a position determined by the position of the member  38  and the pressure in the volume  60  will have increased atmospheric pressure. The drainage of fluid into the volume  60  then stops. 
         [0053]    During the aforementioned process the volume  60  is increased in size. 
         [0054]    The spring  34  is designed to have a relatively invariable spring constant as the piston moves between extended and compressed positions. 
         [0055]    Fluid in the volume  60  can be drained by rotating the outer member  38  in a direction which is opposite to the first direction, thereby loading the spring  34  and causing the piston  28  to push the fluid through the outlet valve  20  so that it can be discarded. 
         [0056]    The fluid inlet  16  and the fluid outlet  2  can be sealed by means of suitable caps, not shown. 
         [0057]    As the connections to, and in, the container body are essentially airtight the volume increase translates into a reduction in the pressure prevailing in the volume to a level which is slightly below atmospheric pressure. Fluid in the body cavity is then expelled by atmospheric pressure actors into the conduit  90  and flows into the volume  60  where it is collected. 
         [0058]    The container body can be made from an appropriate transparent material so that a visual indication is available to a user of the content of the volume. 
         [0059]      FIG. 2  illustrates a device  10 A which is substantially the same as the device  10 . For this reason reference numerals which are the same as reference numerals used in  FIG. 1  are used to designate like components in  FIG. 2 . 
         [0060]    The vacuum in the volume  60  is at a level at the start of a working stroke and reduces over the length of the working stroke. At the start of the working stroke the force exerted by the spring  34  is at a maximum and the spring compressed to a maximum extent. The volume  60  is then of a minimum size. The degree of compression of the spring reduces over the working cycle and the volume  60  increases in size. 
         [0061]    The device  10 A of  FIG. 2  uses a seal  30  which has lips  30 A and  30 B i.e. it is a double-lip hydraulic seal made from a suitable plastics material such as polyurethane. The lips  30 A and  30 B, in the circular cylindrical bore  26 , exert uniform pressure on a surface  26 A of the bore. In  FIG. 3  the lips  30 A and  30 B are shown in an uncompressed form. 
         [0062]    In order to achieve a variable friction force between the piston and the bore, the bore is slightly tapered and increases in cross-sectional dimensions from one end  26 X to an opposing end  26 Y. The degree of taper is slight, typically of the order of 0.2 mm or 0.3 mm. Although the cross-sectional size of the bore increases the flexible double-lip seal is able to accommodate the dimensional change and exhibits a good sealing characteristic over the length of the piston working stroke. 
         [0063]    With the seal in the region  26 X a frictional force between the piston and the cylinder is relatively high due to the lower tolerance between these components. When the piston is in the region  26 Y there is a bigger gap between the piston and the surface  26 A and thus the frictional force between the seal and the cylinder decreases. 
         [0064]    By way of example if the bore of the cylinder is circular cylindrical and uniform then the friction throughout a working stroke is uniform. Calculations and tests have shown that the vacuum level at the end of a working stroke would be approximately 70% of the vacuum level at the beginning of the working stroke. By tapering the bore, in the manner described, the change in the vacuum level from the maximum to the minimum is reduced to about 7%. This means that the rate at which fluid is drained from a body cavity by the device  10 A is kept substantially constant over the working stroke of the device. 
         [0065]      FIGS. 4 to 9  show a device  10 B which is substantially the same as the device  10 . However, the fluid inlet  16  and the fluid drainage outlet  20  shown in  FIG. 1  are dispensed with and are replaced by a single opening  100  to which is fitted a compound, or multiport valve  102  which has a circular base  104 , a circular disc seal  106  and a circular cover  108 . 
         [0066]    The base  104  has an aperture  110  which is directly and permanently connected to the opening  100 . Additionally the circular base  104  has an inlet port  112  and a drain port  114 . 
         [0067]    The inlet port  112 , in use, is connected to a flexible drainage tube  116 , as is shown in  FIGS. 4 and 5 , in accordance with requirements known in the art. This aspect is not further described herein. The drain port  114  leads to a short tube  120  which extends to one side of the base. 
         [0068]    The disc seal  106  is made from rubber and is engageable with a tight fit with the circular base whereby, to some extent at least, the seal is surrounded by a wall  104 A of the base. On a lower side  124 , shown in  FIG. 9 , the disc seal has an arcuate groove  130  which extends through about 180°. The groove is surrounded by a raised bead  132  which, in use, provides a sealing interface between the disc seal  106  and an inner surface  134  of the circular base  104 . 
         [0069]    On an upper side  140  the disc seal has a number of openings  142  which are uniquely engageable with corresponding spigots  144  which project from an inner surface  146  of the cover  108 . Additionally the cover has a plurality of formations  150  on an inner surface of a wall  152  (see  FIG. 9 ). These formations are engageable with complementary formations  160  on the wall  104 A. The arrangement is such that the disc seal is only engageable in a predetermined orientation with the cover  108  and, in turn, the cover is only engageable in a predetermined orientation with the circular base  104 . 
         [0070]    The cover  108  has a raised handle  1  on an upper surface which facilitates manual operation of the valve. 
         [0071]    The device  108  is used substantially the same way as what has been described hereinbefore. The flexible drainage pipe  116  is connected to the inlet port  112 . When the cover  108  is turned in an anticlockwise direction to a limiting position the groove  130  is positioned so that the net port is connected to the opening  100  and fluid drainage can then take place in a conventional manner. The drain port  114  sealed from the port  110  and the port  112  by the seal which is created by the bead  132  bearing on the surface  134 . 
         [0072]    If the cover  108  is manually rotated in a clockwise direction through 90° then a limiting position is again reached but, in this instance, the drain port is connected to the port  110  i.e. to the volume through the opening  100 , and the net port is sealed by the bead  132 . Fluid can now be expelled from the volume  60  to waste. 
         [0073]      FIGS. 4 and 5  illustrate a plug  170  which is attached to a flexible tie  172  secured to the body  12 . In  FIG. 5  the plug is displaced from the tube  120 . In  FIG. 4  the plug is engaged with the tube and seals the drain port and prevents fluid from dripping from the container after it has been emptied. 
         [0074]    The manually operated multipart valve  102  thus dispenses with the need to separate an inlet to the fluid receiving volume from an outlet from the volume. Consequently there is no longer a requirement for an appropriate sealing valve on the inlet, and on the outlet, for an equivalent function can be reliably provided by means of the manually operated valve  102 . 
         [0075]      FIGS. 4, 5 and 7  also illustrate two substantially identical connectors  200  and  202  respectively at an end of the drainage tube  116 . Two drainage tubes  200 A and  202 A, shown in dotted outline, are coupled to the connectors  200  and  202  respectively and extend to locations on a wound (not shown) from which fluid is to be drained. As indicated in the preamble hereof in many instances the tubes  200 A and  202 A are provided, by different supplies, various diameters. The coupling of tubes of different diameters to the drainage device of the invention can thus be problematic. The connectors  200  and  202  help to a considerable extent to alleviate this problem. 
         [0076]      FIG. 10  illustrates from one side and in cross-section the connector  200 . The connector  202  is substantially the same as the connector  200  and for this reason only the connector  200  is described. 
         [0077]    The connector  200  includes a first tubular member  212  and a second tubular member  214 . 
         [0078]    The first tubular member  212  is connected to tubular structure  216  in any appropriate way. The tubular structure may be a tube  200 A, as shown in  FIG. 4 , a spigot on a container or the like. 
         [0079]    Preferably a seal  218  is provided at an interface between the first tubular member  212  and the tubular structure  216 , which enables the connector  200  to be pivoted about a longitudinal axis  220  relative to the tubular structure. This feature adds to the ease of use of the connector. 
         [0080]    The first tubular member  212  has a passage  224  which extends through it. The first tubular member consists of a first section  226  and a second section  228 . The first section is of constant external cross-sectional circular shape and carries external threads  230 . The second section  228  tapers and reduces in external cross-sectional dimension moving away from the first section  226 . The size of the passage  224 , within the second section, is initially constant but subsequently reduces to accommodate the taper on the external surface. 
         [0081]    The second tubular member includes a first part  236  and a second part  238 . A passage  240  extends tip rough the second tubular member. 
         [0082]    The first part  236  is in the nature of a union nut and, in cross-section, internally constant. A thread  242  on an inner surface is complementary in shape to the thread  230  on the first section and is threadedly engageable therewith. 
         [0083]    The second part  238  is tapered moving away from the first part. A portion of the passage  240  within the second part, designated  240 A, is tapered and is generally of the same degree of taper as the tapered external surface of the second section  228 . 
         [0084]    The tubular members are each integrally moulded from a suitable plastics material. The plastics material is fairly tough, yet pliable, and it is possible to cut the second section and the second part with an appropriate tool, such as a sharp pair of scissors with relative ease. 
         [0085]      FIGS. 10, 11, 12 and 13  show that the connector can be used with flexible tubing  250 A,  250 B,  250 C and  250 D respectively of substantially different internal and external diameters. By way of example only the following table sets out the internal and external diameters of the tubes: 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
               
               
                 250A 
                 250B 
                 250C 
                 250D 
               
               
                   
               
             
             
               
                 Internal: 2.1 mm 
                 Internal: 3.2 mm 
                 Internal: 4.3 mm 
                 Internal: 5 mm 
               
               
                 External: 3.5 mm 
                 External: 5 mm 
                 External: 6.5 mm 
                 External: 8 mm 
               
               
                   
               
             
          
         
       
     
         [0086]    Although the dimensions given are exemplary only, the variation in the internal diameter is over 100% and this is the case with the external diameter as well. 
         [0087]    In each instance the second tubular member is disengaged from the first tubular member. In the  FIG. 10  embodiment, the relatively small diameter tube  250 A is pushed through a lower mouth of the first part and then onto the tapered external surface of the second section. The first part is then threadedly engaged with the first section and as the threaded coupling of these components is increased the tapered inner surface of the second part is drawn over the outer surface of the tube and, in the process, the tube is clamped in position in a gap  252  between the second part and the second section. 
         [0088]      FIG. 11  shows that if a tube  250 B has larger dimensions, lengths  260  of the second part and of the second section are severed from the respective tubular elements beforehand. Otherwise the process is the same as what has been described. A similar technique is adopted as the size of the tube further increased—these situations are shown for the tube  250 C in  FIG. 12  and for the tube  250 D in  FIG. 13   
         [0089]    It is necessary to shorten the lengths of the tapered elements of the first tubular member and of the second tubular member to accommodate the differently sized tubes. This is easily done with a sharp pair of scissors. If the tube which is be coupled to the connector has a large internal diameter then little is to be gained by threading the tube over the tapered external surface of the second section. All that is required is to urge the tube into frictional engagement with part of the tapered external surface of the second section and, for ease of use, a part of the second section which does not frictionally engage with the inner surface of the tube is severed and discarded. On the other hand, with the second part of the second tubular member a portion of the second tubular member is severed to expose a portion of the bore which has an adequate diameter to allow the tube to pass there through with relative ease. 
         [0090]    A significant benefit of the connector lies in its capability to couple tubes of different diameters to the drainage device. It is necessary to cut the members as appropriate but this requirement is of a minor nature. Another benefit lies in the fact that the tubular members are threadedly interengaged with one another and in the process a portion of the tube between opposing surfaces of the tubular members gripped with a tight clamping force. This force is such that it would not normally be possible for the tube to be inadvertently detached from the connector.