Abstract:
A valve for a pneumatic dispenser, the dispenser comprising a handle with an actuation arrangement for selectively applying pressure to a respective one of the front and rear chambers on either side of a piston coupled to a rod for applying a dispensing force, thereby controlling movement of the rod. The valve is provided with a body and first and second moveable members moveable relative to the body. The valve can be arranged as a space saving five port valve instead of two three port valves for use in the disclosed dispenser and can be arranged to provide a fail safe mechanism if both valve members are actuated concurrently. A dispenser comprising a stock portion and a cylinder secured to the stock portion is disclosed. Pressure is supplied to the rear chamber of the cylinder from the stock portion through its front chamber and the piston moveable inside the cylinder.

Description:
RELATED APPLICATION 
     The present application claims priority to EP Application No. 10196810.5 filed Dec. 23, 2010, which is incorporated herein in its entirety by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a valve, particularly although not exclusively, a five port valve. The valve finds application in a pneumatic dispenser, particularly but not exclusively, for applying a force to a container holding viscous material to cause the viscous material to be dispensed from the container. 
     SUMMARY 
     European Patent Application EP0551998 A1 discloses a dispenser for viscous material. The dispenser comprises an actuating cylinder containing a piston connected to a rod which extends forward out of the cylinder, and a pistol grip body, in which is mounted a trigger operably connected with a pressure regulator. Actuation of the trigger causes a pressure to be applied to the cylinder via a flexible pipe extending from a regulated two port valve inside the pistol grip to the rear end of the cylinder. The applied pressure causes the piston and, hence, the rod to move forward. A keep is located forward of the cylinder. The keep enables a removable cartridge to be inserted such that application of a force by the rod to a piston inside the cartridge causes viscous material to be dispensed from the cartridge through an aperture. A switch located at an end of the pistol grip distal to the cylinder is used to select between different outlets leading to opposite sides of the piston to enable the piston to be pneumatically driven in either the forward or the rearward direction, according to the selection of the switch. In either case, the pressure is vented from the cylinder after the trigger is released by a dump valve at the rear of the cylinder. When pressure is applied on actuation of the trigger, the dump valve closes until the applied pressure drops when the trigger is released and the dump valve opens to act as a rapid exhaust. 
     Dispensers of a similar general construction as disclosed in EP0551998 A1 are known, which also have a flexible pipe extending from the pistol grip to the rear of the cylinder but have a button at the rear of the cylinder that allows the operator to control whether the pressure applied through the flexible pipe from the pistol grip is applied directly to the rear portion of the cylinder on one side of the piston, or through a coiled tube and the piston to the front portion of the cylinder on the other side of the piston. As for EP0551998, a pressure activated dump valve is used to vent the cylinder to atmosphere when the trigger is released. 
     A common feature of these dispensers is that, in order to change the direction of movement of the piston, the operator must either use two hands or at least move the hand holding the pistol grip from its normal position with the index finger of this hand on the trigger. This causes delays in the operation of the dispenser while the operator moves his hand(s) in order to make the necessary adjustments to the dispenser. Another common feature of these dispensers is that a flexible pipe extends from the pistol grip to the rear end of the cylinder. This flexible pipe hangs loosely from the cylinder and can be a safety hazard. It is also prone to damage and can detract from the visual appearance of the dispenser. The operation of the dump valve to vent the cylinder can involve high levels of noise. 
     U.S. Pat. No. 2,692,706 discloses an air pressure caulking gun with a pair of longitudinally spaced apart air control valves in a valve block actuated by a pivotally mounted trigger member. A trigger finger sits on a valve seat of each control valve to regulate a flow of compressed air to the ports that supply or exhaust air from the valve ports. 
     One aspect of the invention provides a dispenser comprising a handle. A cylinder is secured with respect to the handle. A piston is moveable inside the cylinder, the piston dividing the cylinder into a front chamber and a rear chamber. A rod is arranged to move with the piston, the rod extending from the piston through an aperture in a front end of the cylinder. The handle houses a valve, comprising a body and first and second moveable members linked to an actuation arrangement for controlling the advance and retreat of the rod by actuation of a respective one of the first and second members. The body defines a valve chamber and first, second, third, fourth and fifth ports into the valve chamber, the second and fourth ports being connected to, respectively, the rear and front chamber. The first and second members are moveable within the valve chamber to selectively open and close fluidic communication paths between the ports. The first member is movable between two positions to selectively enable fluidic communication between the second port and either the first port or the third port. The second member is movable between two positions to selectively enable fluidic communication between the fourth port and either the third port or the fifth port. 
     Advantageously, a dispenser with a compact five-port valve can be constructed, in effect combining two three port valves in a single valve body by sharing one of the ports of each notional three port valve. In some embodiments, the second and fourth ports are connected as operating ports (for example to either side of the piston in a dispenser as described above), one of the first, third and fifth ports being connected as a supply or exhaust port and the other two being connected as the exhaust or supply ports, respectively. Space savings are achieved by allowing the operating ports to share a common exhaust or inlet port. A fail-safe may be provided by preventing substantial pressure build-up at both operating ports at the same time. 
     In some embodiments, the first and second members are constrained to move along the same axis and the first and second members may be biased away from each other into respective rest positions. A resilient biasing member may be disposed between the first and second members to this end. In some embodiments, the members are dimensioned such that the possible travel of each of the members is determined by the position of the other one of the members, for example, the members can be arranged to contact each other if one of the members is fully inserted into the chamber. The members may be arranged to be capable of contacting each other inside the chamber to limit how much both members can be inserted at the same time. 
     In some embodiments the first, third and fifth ports are in fluidic communication in configurations of the first and second members with both the first and second members positioned away from their respective rest positions. Where the second and fourth ports are connected as operating ports, it is thus ensured that pressure applied via one or more of the first, third and fifth ports is vented through another one or more of these ports, which are connected as exhaust ports, if both members are actuated at the same time. 
     In some embodiments, for example with the first and fifth port connected to supply pressure to the second and fourth port connected as operating ports and the third port connected as an exhaust port, when the first and second members are in their respective rest positions, fluidic communication is enabled between the second port and the third port, and between the third port and the fourth port, and fluidic communication is prevented between the first port and the second port, and between the fourth port and the fifth port; when the first member is positioned as closely as possible to the second member while the second member remains in its rest position, fluidic communication is enabled between the second port and the third port, and between the fourth port and the fifth port, and fluidic communication is prevented between the first port and the second port, and between the third port and the fourth port; when the second member is positioned as closely as possible to the first member while the first member remains in its rest position, fluidic communication is enabled between the first port and the second port, and between the third port and the fourth port, and fluidic communication is prevented between the second port and the third port, and between the fourth port and the fifth port. There is no configuration in this embodiment of the first and second members in which fluidic communication is enabled between the first port and the second port, and between the fourth port and the fifth port, without at least one of the second port and the fourth port also being in fluidic communication with the third port. 
     In some embodiments, for example with the first and fifth port connected as exhaust ports for the second and fourth port connected as operating ports and the third port connected to supply pressure, when the first and second members are in their respective rest positions, fluidic communication is enabled between the first port and the second port, and between the fourth port and the fifth port, and fluidic communication is prevented between the second port and the third port, and between the third port and the fourth port; when the first member is positioned as closely as possible to the second member while the second member remains in its rest position, fluidic communication is enabled between the first port and the second port, and between the third port and the fourth port, and fluidic communication is prevented between the second port and the third port, and between the fourth port and the fifth port; when the second member is positioned as closely as possible to the first member while the first member remains in its rest position, fluidic communication is enabled between the second port and the third port, and between the fourth port and the fifth port, and fluidic communication is prevented between the first port and the second port, and between the third port and the fourth port. In this embodiment there is no configuration of the first and second members in which fluidic communication is enabled between the second port and the third port, and between the third port and the fourth port, without the first port being in fluidic communication with the second port and/or the fourth port being in fluidic communication with the fifth port. 
     In some embodiments, the first and fifth port are connected to a pressure supply arrangement and the third port is connected to an exhaust arrangement, saving space in particular if the exhaust arrangement comprises a silencer. In some embodiments, the pressure supply arrangement comprises a respective pressure regulator for each of the first and fifth ports, allowing the pressure to be adapted for each chamber, for example using a lower pressure to retreat the rod, thereby saving air when less force is needed. In some embodiments, the rod extends from the piston through the front space. A first fluid conduit is provided for enabling a pressure to be applied from the stock portion to the rear space to advance the rod. The first fluid conduit passes through the front space. This enables the rod to be driven forward without the need for a tube external to the cylinder between the handle and the cylinder. 
     Advantageously, the stock portion and the cylinder can together fully enclose the first fluid conduit. The valve arrangement and the cylinder are then arranged to be in fluidic communication entirely through fluid paths contained within the dispenser, i.e. through the handle and passing directly into the cylinder without first leaving the handle. This ensures that the dispenser is compact, and provides a simpler form factor of the dispenser due to the absence of any visible external fluid paths. The dispenser is also safer as all fluid paths are contained within the dispenser and not exposed, and therefore are less liable to be damaged. 
     In some embodiments, the first conduit passes through an aperture in the piston so that the piston slides along the conduit. In some embodiments, the dispenser further comprises a second fluid conduit passing from the stock portion to the front space for enabling a pressure to be applied to the front space to retreat the rod, the second fluid conduit passing directly from the stock portion to the front space. In some embodiments, the stock portion and the cylinder fully enclose the first and second fluid conduits. An actuation arrangement may be provided to control the application of pressure via the first and second conduits to advance and retreat the rod. 
     Any of the dispensers described above may comprise a holder for holding a container, such as a cartridge or foil pack, containing viscous material to enable application of a dispensing force to the container as the rod advances, thereby dispensing at least some of the viscous material from the container. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are now described by way of example only and with reference to the accompanying drawings, in which: 
         FIG. 1  depicts a perspective view of a dispenser; 
         FIG. 2  depicts a cross-section of part of the dispenser; 
         FIG. 3  depicts a valve arrangement and associated components; 
         FIG. 4A  depicts a cross-section of the valve arrangement in a rest configuration; 
         FIG. 4B  depicts a cross-section of another embodiment of the valve arrangement in the rest configuration; 
         FIG. 5A  depicts a cross-section of the valve arrangement in a drive configuration; 
         FIG. 5B  depicts a cross-section of the other embodiment of the valve arrangement in the drive configuration; 
         FIG. 6A  depicts a cross-section of the valve arrangement in a return configuration; 
         FIG. 6B  depicts a cross-section of the other embodiment of the valve arrangement in the return configuration; 
         FIG. 7A  depicts a cross-section of the valve arrangement in a configuration in which each of its two spools has been depressed; and 
         FIG. 7B  depicts a cross-section of the valve arrangement in a configuration in which each of its two spools has been depressed. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , a pneumatic dispenser  2  comprises a cylinder  4  secured to a stock portion  6  and a cartridge holder  8  secured forward of the cylinder  4 . The cylinder has a wall with a substantially annular cross-section. The cartridge holder  8  is arranged to receive a cartridge (not shown) containing viscous material and is arranged such that the cartridge held in the cartridge holder  8  is disposed in a dispensing relationship relative to the cylinder  4 , as described below. 
     The specific embodiment depicted in  FIG. 1  is arranged to dispense material from two component cartridges having two barrels, one for each component material and has two plungers, one for each barrel. A plurality of rods  10  extend through a front end of the cylinder  4  through respective apertures, which seal around the rods  10 . The rods  10  extend substantially parallel to a longitudinal axis of the cylinder  4 . A plunger  12  for engaging a piston inside the cartridge is coupled to two of the rods  10  at a forward end of the rods  10 . A further, smaller plunger is coupled to the remaining rod. The smaller plunger and remaining rod are obscured behind the cartridge holder  4  in  FIG. 1 . The rods  10  and the plungers  12  are moveable relative to the cylinder  4  along a longitudinal axis of the rods  10  such that a force can be applied to the cartridge by the plungers  12  when the cylinder  4  is pressurized to cause viscous material to be dispensed from the cartridge. 
     The stock portion  6  comprises a handle  14  extending away from the cylinder  4  in the vicinity of the front end of the cylinder  4 . The handle  14  is ergonomically shaped to be held by one hand of a human operator of the dispenser  2  and comprises a drive trigger  18  and a return trigger  20  for, respectively, controlling the advance and return (i.e. retreat) of the rods  10 . The drive trigger  18  and the return trigger  20  face substantially forward and are positioned on the handle  14  such that each trigger can be individually depressed by the operator while the operator&#39;s hand is holding the handle  14 . The drive trigger  18  is positioned on the handle  14  further from the cylinder  4  such that it is actuatable by the middle finger of the operator&#39;s hand, and the return trigger  20  is positioned on the handle  14  closer to the cylinder  4  such that it is actuatable by the index finger of the operator&#39;s hand. The handle  14  also comprises a regulator  22  at an end of the handle  14  distal to the cylinder  4 . The regulator  22  has a quick release pressure connector  24  arranged to connect to a pressure hose to receive pressurized fluid (for example, compressed air) from a pressure source (not shown) and a dial  26  for controlling the pressure of the pressurized fluid supplied by the regulator  22 . 
     With reference to  FIG. 2 , depicting a cross-section of the dispenser with one of the rods  10  visible, a piston  28  coupled to the rods  10  for driving the rods  10  is slidingly accommodated within the cylinder  4 . The piston  28  divides the inside of the cylinder  4  into two chambers: a drive chamber  30  on the rearward side of the piston  28  between the piston  28  and a closure member  32  closing the back end of the cylinder  4 , and a return chamber  34  on the forward side of the piston  28  between the piston  28  and the apertures around the rods  10 . The rods  10  are coupled to the piston  28  and extend forward of the piston  28 . The rods  10  thus move with the piston  28  relative to the cylinder  4  parallel to the longitudinal axis of the cylinder  4 . 
     A valve  36  is situated within the handle  14  so that it is actuatable by the return trigger  20  and the drive trigger  18 . The return trigger  20  is arranged to directly engage a first spool (described below) of the valve and the drive trigger  18  is arranged to actuate a second spool (described below) of the valve via a yoke while the drive trigger  20  pivots about a pivot forward of the valve. 
     A return conduit  38  passes from the valve  36  through an aperture in the cylinder  4  into the return chamber  34  to enable fluidic communication between the valve  36  and the return chamber  34 . A drive conduit  40  passing from the valve  36  to the drive chamber  30  comprises a first drive conduit portion  42 , which passes from the valve  36  to the return chamber  34  through a further aperture in the cylinder  4 . Fluid is prevented from escaping the return chamber  34  between the respective apertures and the outside of the first drive conduit portion  42  or the return conduit  38  by a sealing member  44 . The sealing member  44  sealingly holds O-rings  80  in place around each of the return conduit  38  and the drive conduit  40  and against an inner surface of the cylinder  4  around each of the apertures. A second drive conduit portion  46  passes from the sealing member through the return chamber  34  and extends through an aperture in the piston  28  into the drive chamber  30  to enable fluidic communication between the valve  36  and the drive chamber  30 . The aperture in the piston  28  seals around the second drive conduit portion  46 , and the drive conduit  40  is therefore sealed from the return chamber  34 . In operation, the piston  28  slides over the second drive conduit portion  46  whilst maintaining the seal around it. 
     The valve  36  is in fluidic communication with a pressure inlet conduit  48  connected to the regulator  22 . The valve  36  is also in fluidic communication with an exhaust  50  for releasing pressure in the cylinder  4  to the atmosphere. The exhaust  50  is arranged to act as a silencer  51  in order to reduce the noise emitted from the dispenser  2  when the cylinder  4  is vented through the exhaust  50 . 
     The valve  36  is arranged such that the pressure inlet conduit  48  and the exhaust  50  are each selectively in fluidic communication with the drive chamber  30  and the return chamber  34  under control of the triggers. Actuation of the valve  36  using the triggers enables the operator of the dispenser  2  to selectively enable or prevent fluidic communication between combinations of the pressure inlet conduit  48 , the exhaust  50 , the drive chamber  30  and the return chamber  34  to advance or retreat the rods  10 . 
     In use, when neither the drive trigger  18  nor the return trigger  20  has been depressed by the operator, the dispenser  2  is in a rest configuration. In the rest configuration, the regulator  22  is disconnected from both the drive chamber  30  and the return chamber  34  and both chambers are connected to the exhaust  50 , placing the drive chamber  30  and the return chamber  34  at atmospheric pressure. 
     When the drive trigger  18  has been fully depressed by the operator, and the return trigger  20  is not depressed, the dispenser  2  is in a drive configuration. In the drive configuration, the regulator  22  is connected the drive chamber  30  and remains disconnected from the return chamber  34 , which remains connected to the exhaust  50 . The exhaust  50  is disconnected from the drive chamber  30 , so that pressure builds up in the drive chamber  30 , driving the piston  28  and, hence, the rods  10  forward. 
     When the return trigger  20  has been fully depressed by the operator, and the drive trigger  18  is not depressed, the dispenser  2  is in a return configuration. In the return configuration, fluidic communication between the pressure inlet conduit  48  and the return chamber  34  is enabled, and fluidic communication between the pressure inlet conduit  48  and each of the drive chamber  30  and the exhaust  50  is prevented. Fluidic communication between the exhaust  50  and the drive chamber  30  is enabled, and fluidic communication between the exhaust  50  and the return chamber  34  is prevented. In the return configuration, pressurized fluid is applied to the return chamber  34 , which causes the piston  28  to move rearwards. 
     When each of the drive trigger  18  and the return trigger  20  are depressed by the same amount, and each are depressed as much as they can both be depressed at the same time, the dispenser  2  is in a free flow configuration. In the free flow configuration, a pressure increase in the drive chamber  30  and/or the return chamber  34  is prevented. This is achieved by enabling fluidic communication between the drive chamber  30  and the exhaust  50  and between the return chamber  34  and the exhaust  50 . Fluidic communication is also enabled between the pressure inlet conduit  48  and the exhaust  50 . 
     When both triggers are depressed as far as possible, they are effectively coupled to each other via the spools of the valve  36 , as described below, so that any inward movement of one trigger carries outward movement of the other trigger. Thus with both triggers pressed, an operator can vary between the configurations described above by varying the force applied to each trigger. However, the valve  36  and its link to the triggers are arranged such that, for any amount of depression of either or both the triggers, it is never the case that the regulator  22  is able to supply a substantial increase in pressure to both the drive chamber  30  and the return chamber  34  at the same time. Depending on the amounts of depression of the two triggers, either there is substantially no increase in pressure in each of the two chambers, or there is a substantial increase in pressure in only one of the chambers. 
     The configurations of the dispenser  2 , and in particular the valve  36  are now described in more detail with reference to  FIGS. 3 ,  4 A,  5 A,  6 A and  7 A. The valve  36  comprises a valve body  60 , which defines a substantially cylindrical valve chamber  62 . The valve body  60  defines a return inlet port  64 , a return operating port  66 , an exhaust port  68 , a drive operating port  70  and a drive inlet port  72 , arranged consecutively with respect to the longitudinal axis of the valve chamber  62 . The pressure inlet conduit  48 , which is connected to the regulator  22 , bifurcates between the regulator  22  and the valve  36 , such that a drive inlet conduit  52  is connected to the drive inlet port  72  and a return inlet conduit  54  is connected to the return inlet port  64 . The exhaust  50  is connected to the exhaust port  68 . 
     A drive spool  56  and a return spool  58  are each moveable within the valve  36  to actuate the valve  36 . As shown in  FIG. 2  and discussed above, the drive trigger  18  is connected to the drive spool  56 , and the return trigger  20  is connected to the return spool  58  by respective mechanical links, which cause each spool to move as each respective trigger is depressed. 
     The drive spool  56  and the return spool  58  are situated in the valve chamber  62  and are moveable within the valve chamber  62  substantially along the longitudinal axis of the valve chamber  62 . Each spool extends through a respective aperture in the valve body  60  at opposite ends of the valve chamber  62  along the longitudinal axis. A spring  74  is situated within the valve chamber  62  between the drive spool  56  and the return spool  58 . The spring  74  is in compression and exerts a force on the spools which acts to move them apart. A maximum separation distance of the drive spool  56  and the return spool  58  is defined by a first stop  76  and a second stop  78 , each defined by the valve body  60 , and each acting to prevent movement of the drive spool  56  and the return spool  58 , respectively, beyond a maximum separation distance. 
     Each spool comprises lands and grooves as shown, for example, in  FIG. 4A . A plurality of O-rings  80  are positioned in the valve chamber  62  as shown, for example, in  FIG. 4A  to define adjacent regions of space along the valve chamber  62  between pairs of the O-rings  80 . Each region of space contains one of the five ports. When a land of either of the spools is situated within one of the O-rings  80 , fluidic communication between the two regions of space on either side of that O-ring  80  is prevented, and therefore fluidic communication between the two ports associated with the two regions of space is prevented. Given the consecutive arrangement of the regions of space along the valve chamber  62 , if, for example, fluidic communication between the return inlet port  64  and the return operating port  66  is prevented, fluidic communication is also prevented between the return inlet port  64  and any of the other ports. 
     Each of the ports and each of the apertures through which the spools extend out of the valve body  60  are individually sealed by respective O-rings  80  to prevent fluid from escaping from or entering the valve chamber  62  other than through the valve ports. 
     With reference to  FIG. 4A , in the rest configuration, the spools  56 ,  58  are at their maximum separation distance, and are positioned such that fluidic communication between the return inlet port  64  and the return operating port  66  is prevented, fluidic communication between the return operating port  66  and the exhaust port  68  is enabled, fluidic communication between the exhaust port  68  and the drive operating port  70  is enabled, and fluidic communication between the drive operating port  70  and the drive inlet port  72  is prevented, connecting the cylinder  4  on either side of the piston  28  to the atmosphere, so that the piston is not driven. 
     With reference to  FIG. 5A , in the drive configuration, the drive spool  56  has been moved by the drive trigger  18  from its position in the rest configuration towards the return spool  58  to abut the return spool  58 . The spools are positioned such that fluidic communication between the return inlet port  64  and the return operating port  66  is prevented, fluidic communication between the return operating port  66  and the exhaust port  68  is enabled, fluidic communication between the exhaust port  68  and the drive operating port  70  is prevented, and fluidic communication between the drive operating port  70  and the drive inlet port  72  is enabled, connecting the drive operating port  70  to the regulator  22  to apply a drive pressure to cause the piston  28  and hence the rods  10  to advance. 
     With reference to  FIG. 6A , in the return configuration, the return spool  58  has been moved from its position in the rest configuration towards the drive spool  56  to abut the drive spool  56 . The spools are positioned such that fluidic communication between the return inlet port  64  and the return operating port  66  is enabled, fluidic communication between the return operating port  66  and the exhaust port  68  is prevented, fluidic communication between the exhaust port  68  and the drive operating port  70  is enabled, and fluidic communication between the drive operating port  70  and the drive inlet port  72  is prevented, connecting the return operating port  66  to the regulator  22  to apply a return pressure to cause the piston  28  and, hence, the rods  10  to retreat. 
     With reference to  FIG. 7A , in the free flow configuration, the drive spool  56  and the return spool  58  have each been moved by the same distance away from their position in the rest configuration towards each other until the spools abut each other. The spools are positioned such that fluidic communication between all of the ports is enabled. As a result, a substantial increase in pressure in the drive chamber  30  and/or the return chamber  34  is prevented by enabling fluidic communication between the drive chamber  30 , the return chamber  34 , the pressure inlet conduit  48  and the exhaust  50 , causing pressurized fluid from the regulator  22  to vent through the exhaust  50 . 
     The above described specific embodiment is manufactured from a combination of metal for the cylinder  4 , the rods  10  and the cartridge holder  8  and plastic materials for the remaining structural components including the stock portion  6 . The cylinder  4  and end plates at the distal end of the cartridge holder  8  are made of aluminium, and the rods  10  and the remainder of the cartridge holder  8  are made of steel. The plastic materials used are nylon or acetal, with glass fillers where required. It will be understood that any suitable combination of these materials, including construction with all structural parts made from plastic materials can be used in alternative embodiments. Numerous materials are suitable for use in the sealing parts such as O-rings, for pressure connecting hoses and tubes and other pneumatic components such as valves and connectors, as is well known to the person skilled in the art. 
     It will be understood that the above description of specific embodiments of the invention is by way of example only and it is not intended to limit the scope of the invention. Many modifications of the described embodiments, some of which are now described, are envisaged and intended to be covered by the appended claims. 
     While the specific embodiment described above has a valve connected with one exhaust port  68  and two inlet ports  64 ,  72 , some embodiments have two exhaust ports and a single inlet port. With reference to  FIGS. 4B ,  5 B,  6 B and  7 B, a dual exhaust embodiment is similar to the embodiment described above, with the main differences between the embodiments being that the dispenser  2  comprises a drive exhaust  82  arranged to relieve pressure from the drive chamber  30  and a return exhaust  84  arranged to relieve pressure from the return chamber  34 , and that the pressure inlet conduit does not bifurcate, but has a common pressure inlet conduit  86  connected to one port of the valve  36 , selectively in fluidic communication with the drive chamber  30  and the return chamber  34  via the drive conduit  40  and the return conduit  38 , respectively. The lands and grooves of the spools are arranged differently from the specific embodiment described above, as shown, for example, in  FIG. 4B , as a consequence of the different roles of the ports from one end of the valve  36  to the other. 
     The connections of the return operating port  66  and the drive operating port  70  are the same as in the embodiment described above, but the return exhaust  84  is connected to the return inlet port  64 , which now acts as a return exhaust port, the common pressure inlet conduit  86  is connected to the exhaust port  68 , which now acts as a common inlet port, and the drive exhaust  82  is connected to the drive inlet port  72 , which now acts as a drive exhaust port. 
     As can be seen from  FIGS. 4B ,  5 B,  6 B and  7 B, the spools are arranged such that the drive and return ports are connected to their respective exhaust ports in the rest configuration, the drive port is connected to the common inlet and disconnected from its exhaust port in the drive configuration, and analogously for the return port in the return configuration. As for the specific embodiment described above, all ports are connected in the free flow configuration. 
     In the free flow configuration, in some embodiments, the fluidic communication relationships between the ports are the same as the fluidic communication relationships described above for the rest configuration, e.g., for the specific embodiment described above with respect to  FIG. 4A , fluidic communication between the return inlet port  64  and the return operating port  66  is prevented, and fluidic communication between the drive operating port  70  and the drive inlet port  72  is prevented. 
     In some embodiments, the drive spool  56  and the return spool  58  are biased apart by any kind of biasing means such as a resilient polymeric member. The resilient biasing need not be provided between the two spools but each could have its own resilient biasing member associated with it, for example between the spool and the valve housing. The valve has a different number of ports, in some embodiments, and in particular, in some embodiments, the valve has at least six ports, such that the drive conduit and the return conduit are each selectively in fluidic communication with their own dedicated inlet and exhaust. 
     In general, while the above description has been made in terms of a five port valve used in a dispenser, it will be understood that the invention is not limited in this way and extends to the valve as such, irrespective of its application. The valve will find useful application in many areas where it would be advantageous to combine the functionality of two three port valves in a single valve body, for example to save space, by sharing one of the ports of each notional three port valve. Such applications include, but are not limited to, applications where pressure needs to be applied to and vented from two separate chambers, whether the pressure is supplied from a common pressure source or from one respective pressure source for each chamber. Likewise, depending on the application, the ports of the valve may be placed differently about the longitudinal axis of the valve, for example all to one side or at different angles about the axis. 
     Turning now to the above description of a dispenser incorporating such a valve, while the specific embodiment described above is adapted for use with cartridges, in some embodiments, instead of the cartridge holder  8  as described above, the dispenser  2  comprises other kinds of holders, such as a holder to allow viscous material to be dispensed from a foil pack. 
     In some embodiments, the drive trigger  18  and the return trigger  20  are arranged the other way around, such that actuation of the trigger closer to the cylinder  4  causes the rods  10  to advance, and actuation of the trigger further from the cylinder  4  causes the rods  10  to retreat. In some embodiments, this is achieved by altering the mechanical links between the triggers and the valve  36 , while in other embodiments, this is achieved by connecting the second drive conduit portion  46  to the conduit portion that is in fluidic communication with the return operating port  66  of the valve  36  (which then acts as a drive port), rather than the drive operating port  70  of the valve  36  (which then acts as a return port). 
     In some embodiments, the handle  14  comprises a seesaw switch having a first actuation surface on one side of the pivot, and a second actuation surface on the other side of the pivot, wherein depression of one surface causes the rods  10  to advance, and depression of the other surface causes the rods  10  to retreat. 
     While the wall of the cylinder  4  of the specific embodiment described above has an annular cross-section, in some embodiments, the cylinder  4  has a different cross-section, for example a non-annular cross-section, such as those defining a chamber of an ellipsoid or a polygonal (rounded or not) cross-section. 
     In some embodiments, the dispenser  2  comprises a drive regulator and a return regulator, for regulating the supply of pressurized fluid to the drive chamber  30  and the return chamber  34 , respectively in the respect drive and return configurations, rather than a single regulator. The drive regulator is in fluidic communication with a port of the valve  36  via a drive inlet conduit, and the return regulator is in fluidic communication with another port of the valve  36  via a return inlet conduit. In some of these embodiments, the regulator is arranged such that the pressure applied to the drive chamber  30  in the drive configuration is higher than the pressure applied to the return chamber  34  in the return configuration. In some further ones of these embodiments, each regulator has its own dial for changing the amount of pressure applied to the respective chamber. 
     In some further embodiments, the drive conduit  40  comprises a flexible (e.g. coiled) tube attached to an aperture in the piston  28  instead of the second drive conduit portion  46  extending through an aperture in the piston  28  as described with reference to  FIG. 2 . The flexibility of the tube allows the connection with the piston  28  to remain in place as the piston  28  moves relative to the cylinder  4 . 
     The above description of a specific embodiment of a dispenser above has been made in terms of a dispenser for two component cartridges having three rods and two plungers. It will be appreciated that the number and configuration of the rods are central to the description of the invention and that many other arrangements are possible within the scope of the invention, depending on the application at hand. For example, two rods and respective identical plungers arranged symmetrically about a central plane of the dispenser could be used for a two-component dispenser dispensing material in equal dispensing ratios or a single rod and plunger, for example arranged along a central axis of the cylinder  4 , could be used for dispensing from single component, single barrel cartridges.