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REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to United Kingdom Patent Application 0606631.0 filed on Apr. 1, 2006, the entirety of which is incorporated by reference herein. 
     BACKGROUND TO THE INVENTION 
     The present invention relates to a paddle latch for a closure. Particularly, although not exclusively, the present invention concerns paddle latches designed to be installed on the doors of heavy plant containers and buildings where water ingress to the interior of the container or building is undesirable. 
     It is known to provide paddle latches on the doors of heavy plant containers or buildings containing heavy plant equipment such as generators or pumps. Paddle latches are suited to this application as paddles generally provide a large area with which to actuate the latch, which can be advantageous if the user is wearing protective gloves. Furthermore, the paddle latch acts as a latch and handle whereby the user only needs to pull on the paddle to both actuate the latch and open the door in the same movement. 
     Paddle latches often comprise a latch member which, when in a latched condition, engages with a feature on the door frame such that the door cannot be opened. The latch member is often mounted on a shaft such that it can rotate from a latched position whereby it engages the feature on the door frame to an unlatched position whereby it is clear of that feature and the door can be opened. 
     In known paddle latches, the latch member is often resiliently biased towards the latched position. Unlatching can be achieved by actuating the paddle which physically contacts the latch member overcoming the resilient bias and moving the latch member into an unlatched position whereby the door may be opened. It is also known for the interaction between the paddle and the latch member to only act to move the latch member into an unlatched position. Therefore when the paddle is in the closed position, movement of the latch member will not cause corresponding movement of the paddle. Consequently, the door can be closed and latched without any corresponding motion of the paddle. This is desirable as it is instinctive to apply a door closing force upon the paddle, and if it was to move in an opposite sense to the applied force, this movement would create both undue stresses on the components of the latch and would make closing the door more difficult. 
     In order to provide a slam function that allows the door to be shut without corresponding movement of the paddle, previous paddle latches have provided a mechanical interaction between the paddle and the latch member that is only effective in a single direction, such that movement of the paddle actuates the latch member from a latched to an unlatched position (in order to open the door), but movement of the latch member from a latched position to an unlatched position and back again (e.g. during door closure) does not cause corresponding motion of the paddle. 
     It is generally undesirable to allow water ingress into the container or building in which the equipment is stored. Heavy plant equipment such as generators and transformers do not respond well to the presence of water, and regulations stipulating levels of sealing on the containers or buildings are becoming ever more stringent. Water ingress can not only impair the operation of this equipment, but can also cause corrosion of metals. Furthermore, water can collect in sumps provided under such equipment, reducing their capacity for collecting oil, and resulting in oil over-flowing into the surrounding environment. 
     Items of heavy plant equipment such as generators often create a negative pressure environment inside the container or building as they operate, which results in a “suction” effect at any orifices between the exterior and the interior of a container or building. This suction effect draws in any water that may be present on the surface of the container or building resulting from rain fall or condensation. 
     Furthermore, items of heavy plant equipment (such as generators) often create a lot of noise. Any such noise can be transmitted from the interior to the exterior of the container via orifices and slots in latches. This noise can be disruptive, and cause discomfort to those in the vicinity of the container. It is therefore desirable to decrease the noise transmitted from the interior to the exterior of the container. 
     As discussed above, known paddle latches require that the paddle (normally located on the exterior of the building for access) and the latch member (normally located on the interior of the building such that it can contact a part of the door frame) have to be in contact in order for the latch to operate. The requirement for a mechanical interaction implies that there must be some kind of orifice or slot through which one of the components must pass in order to interact with the other. Furthermore, due to the motion of the components the orifice or slot is usually at least partially open in order to allow linear movement during operation. 
     Bearing in mind the requirement for sealing discussed above, the existence of such slots and orifices is disadvantageous in paddle latches. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide an improved paddle latch. 
     According to a first aspect of the invention there is provided a paddle latch comprising a housing defining a first side and a second side, a shaft extending through the housing defining a first shaft portion on the first side and a second shaft portion on the second side, a paddle for actuation by a latch user on the first side and a releasable latch member for co-operation with an associated striker to latch the, latch paddle on the second side wherein the paddle is connected to the first shaft portion and the latch member is connected to the second shaft portion such that torque may be transferred from the paddle to the latch member to release the latch member from the striker in use. 
     As discussed, known latches often comprise shafts on which the paddle rotates, but the interaction between the paddle and the latch member is normally a direct one giving rise to the necessity for large slots or orifices, which can cause water ingress into the container or building. The present invention overcomes this by allowing the drive shaft to transfer the force between the paddle and the latch member such that the only orifices that are required in the paddle latch are those through which the drive shaft must pass. This is advantageous as the drive shaft motion is only rotational and therefore orifices with a tight fit can be used, which may be more resistant to water ingress than prior art latches whilst still providing the required functionality. 
     Large slots of orifices can transmit noise from the interior to the exterior of the container, which is undesirable (as discussed above). The present invention mitigates this problem by allowing the drive shaft to transfer the force between the paddle and the latch member such that the only orifices that are required in the paddle latch are those through which the drive shaft must pass. Consequently as the drive shaft fits tightly inside these orifices, there is very little or no gap through which noise may pass. 
     A latch retention device will now be described in detail by way of example and with reference to the accompanying drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevation of a wall of a container comprising a door and a paddle latch in accordance with the present invention; 
         FIG. 2  is a perspective view of a paddle latch in accordance with the present invention; 
         FIG. 3  is a side section view of the latch of  FIG. 2  in the direction denoted by III; 
         FIG. 3   a  is a perspective view of a drive shaft for the latch of  FIG. 2 ; 
         FIG. 4  is an end view of the latch with  FIG. 2  with a partially cut-away section; 
         FIG. 4   a  is a perspective exploded view of a drive shaft and latch arm for the latch of  FIG. 2 ; 
         FIG. 5  is a bottom view of the latch of  FIG. 2 ; 
         FIG. 6  is an end view of the latch of  FIG. 2 ; 
         FIG. 7  is a side view of a part of the latch of  FIG. 2 . 
         FIG. 8   a  is a similar view to  FIG. 7  showing the latch of  FIG. 2  interacting with a striker in a latched position; 
         FIG. 8   b  is a similar view to  FIG. 8   a  showing the latch of  FIG. 2  in an unlatched position as actuated by a user; 
         FIG. 9   a  is a similar view to  FIG. 7  showing the latch of  FIG. 2  interacting with a striker with the closure in an open position; 
         FIG. 9   b  is a similar view to  FIG. 9   a  showing the latch interacting with a striker upon movement of the closure from an open to a closed position; 
         FIG. 9   c  is a similar view to  FIG. 9   b  showing the latch of  FIG. 2  interacting with a striker when the closure is in a closed position; 
         FIG. 10  is a section view of a drive shaft interacting with a latch arm according to a further embodiment of the latch of  FIG. 2 ; and 
         FIG. 11  is a section view of a drive shaft interacting with a latch arm in accordance with the still further embodiment of the latch with  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1  a paddle latch  10  is configured for use with a door  12  on a container  14 . 
     The container  14  comprises a striker  15  (as shown in  FIG. 3 ) with which the panel latch  10  interacts in order to secure the door  12  in a closed position. The striker  15  may take many forms but is generally a metal member or bar attached to the container  14 , or simply a portion of the door surround of the container. 
     Referring to  FIGS. 2 to 6 , paddle latch  10  comprises a handle, commonly referred to as a paddle  16 , housing  18 , latch member  20  and drive shaft  22 . 
     The housing  18  comprises a housing body  24  and an attachment bracket  26  as depicted in  FIG. 4 . 
     The housing body  24  is a moulded plastic or stamped metal component comprising a substantially flat flanged portion  28 , a first depression  30  and a further depression  32  formed therein. The first depression  30  comprises a small rectangular section  34  and an adjacent large rectangular section  36 . The small rectangular section  34  comprises a circular orifice  35  defined through two opposite side walls  39 ,  41  thereof. The further depression  32  is substantially rectangular in shape. 
     A tab  37  as shown in  FIG. 4  extends from an end face of the small rectangular section of  34  and substantially parallel with it. The function of the tab  37  will be described later. 
     The housing body  24  further defines two attachment posts  38  which project from the rear wall of the first depression  30  such that they are level with the further depression  32 . The attachment posts  38  are threaded internally. 
     When installed (as shown in  FIG. 4 ), the flange portion  28  abuts the surface of the door  12  such that it is sealed against water ingress, optionally utilising a seal  29 . Attachment bracket  26  is mounted on the inside of the door  12  so as to abut the inner surface of the door  12  and the attachment posts  38 . Bolts  40  can then be threaded through washers  42  and through orifices (not shown) in attachment bracket  26  to be threadably engaged with the interior threads of the attachment posts  38  such that the paddle latch  10  is held in position. 
     The paddle  16  is constructed from a moulded plastic or stamped metal material and comprises handle portion  44  and hub portion  46 . The handle portion  44  is substantially wider than the hub portion  46  and when in the closed position sits within the large rectangular section  36  of first depression  30  within the housing  18 . The handle portion  44  is shorter than the large rectangular section of first depression  30  and consequently defines a finger hole  48  into which the operator&#39;s fingers may be inserted. 
     The hub portion  46  sits within the small rectangular section  44  of the first depression  30 . When the paddle  16  is in a closed position (as shown in  FIG. 2 ) the surfaces of handle portion  44  and hub portion  46  are flush with the flange portion  28  of the housing  18 . 
     The handle portion  44  optionally contains a lock  50  extending therethrough and into the housing  18  through the first depression  30  into the further depression  32 . The lock  50  comprises a locking member  52  which may be rotated about the lock axis (denoted by broken line A in  FIG. 3 ) following insertion of a key (not shown) such that the locking member  52  engages a feature of the further depression  32  such that the paddle  16  cannot be moved. This prevents the paddle latch  10  from being actuated and hence prevents the door from being opened. 
     The hub portion  46  extends into the first depression  30  of the housing  18  and defines a circular passageway  54  therethrough. The paddle  16  is positioned in the housing  18  such that it is able to rotate about the axis of the circular passageway  54 . 
     A drive shaft  22  is depicted in  FIG. 3   a  and comprises central a cylindrical section  56 , a first end section  58  and a second end section  60 , the end sections  58 ,  60  being semicircular in cross section. The end sections  58  and  60  may be formed by, for example, a machining operation on circular bar stock. The drive shaft  22  further comprises a threaded hole  62  extending at least part way through the central cylindrical section  56 . The drive shaft  22  receives a grub screw  64  defining a complementary thread to that of the threaded hole  62 . The cylindrical section has a diameter to be a snug fit in passageway  54  and has a length sufficient to extend into the opposite walls  39 ,  41  of the small rectangular section  34  of the housing  18 . Furthermore, the cylindrical section comprises a first o-ring groove  59  and a second o-ring groove  61 , into which drive shaft o-rings  63  fit (as shown in  FIG. 4 ). The drive shaft o-rings  63  form a water and/or noise resistant seal between the interior and the exterior of the container. 
     The latch member  20  comprises a first latch arm  66 , a second latch arm  68 , a latch head  70 , a latch spring  72 , a return spring  73  and screws  74 . 
     The first latch arm  66  and the second latch arm  68  are constructed from sheet metal material and each comprise a head portion  76 , a centre portion  78  (substantially perpendicular to the head portion  76 ) and a base portion  80  (parallel to the head portion  76 ), such that the head portion  76  and the base portion  80  are offset by the length of the centre portion  78  as shown in  FIG. 4 . The latch head  70  is configured to sit between the head portions  76  of the latch arms  66 ,  68 . It comprises a moulded metal or plastic body defining four threaded holes  82 , which correspond to holes through the head portions  76  of the latch arms  66 ,  68 . The screws  74  are inserted through the holes in the latch arms  66 ,  68  and engaged with the threaded holes  82  of the latch head  70  as shown in  FIG. 4 . In other embodiments the latch head may be adapted to suit various configurations of door and striker. 
     The base portions  80  of the latch arms  66 ,  68  each comprise an orifice  84  defining a circle sector with an angle greater than 180° as depicted in  FIG. 4   a . It should be noted that the shape of this orifice may vary greatly within the scope of the invention, and is generally dependent on the cross-sectional shape of the ends  58  and  60  of the drive shaft  22 , as will be described later. 
     In order to assemble the paddle latch  10 , the paddle  16  is inserted into the first depression  30  of the housing  18  as shown in  FIG. 2 . The circular passageway  54  lines up with the circular orifices  35  in the walls of the small rectangular section  34  in the housing  18 . The axis on which these orifices lie is shown at R in  FIG. 4 . 
     Orifices  84  of the base portion  80  of the latch arms  66 ,  68  also line up with axis R, such that a passageway is defined through the latch arms  66 ,  68 , the small rectangular section  34 , and the circular passageway  54  which receives the drive shaft  22  as shown in  FIG. 4 . In this embodiment the drive shaft comprises seals (not shown) such as o-rings where it engages the housing in order to prevent the passage of liquid through the orifices  35 . In other embodiments for applications with less stringent sealing requirements, the seals may be omitted. 
     The latch member  20  is positioned substantially perpendicular to the closure  12  as shown in  FIG. 3  with the base portion  80  of the first latch arm  66  abutting the tab  37  of the housing  18  as shown in  FIG. 4 , such that it is able to rotate about the drive shaft  22  only in a clockwise direction from the state shown in  FIG. 3 . 
     The latch spring  72  is threaded onto the drive shaft  22  such that it engages the second latch arm  68  and the flange portion  28  of the housing  18  as shown in  FIG. 7 . The latch spring  72  therefore resiliently biases the latch member  20  in an anticlockwise direction when viewed in  FIG. 7  (or alternatively a clockwise direction when viewed in  FIG. 3 ) against the tab  37 . 
     The return spring  73  is threaded onto the drive shaft  22  such that it engages the drive shaft  22  and the flange portion  28  of the housing  18 . In this manner the return spring resiliently biases the drive shaft  22  (and therefore paddle  16 ) to its retracted position. The spring therefore need only be sufficiently strong to bias the paddle flush with the housing. 
     It should be noted that both springs  72 ,  73  are located on the interior of the paddle latch  10 , and are therefore advantageously well protected from water damage which may impair their function. 
     Furthermore, the drive shaft  22  is rotationally positioned within the orifices  84  of the latch arms  66 ,  68  such that the flat end sections  58 ,  60  abut the corresponding surfaces of the orifices  84 , of the latch arms  66 ,  68  so as to rotate the latch arms  66 ,  68  when a torque is applied to the drive shaft  22 . As can be seen in  FIG. 7 , rotation of the latch member  20  in a clockwise direction through its normal range of motion, would not cause a corresponding rotation of the drive shaft  22  due to the shape of the orifice  84 . 
     The paddle latch  10  is shown in  FIG. 3  in a latched position. The door  12  is unable to open due to the interaction of the latch member  20  and the striker  15 . Rotation of the paddle  16  by an operator&#39;s fingers inserted into finger hole  48  causes rotation of the drive shaft  22  via the engagement of the grub screw  64  with the drive shaft  22 . This rotation causes the abutting surfaces of the drive shaft  22  and the latch member  20  to cause the latch member  20  to rotate as shown in  FIGS. 8   a  to  8   b.    
       FIG. 8   a  shows a view similar to that of  FIG. 7  with the shaft  22  cross-hatched and the latch member  20  hatched for clarity. The latch spring  72  abuts the flange portion  28  and the latch member  20  such that it is biased in an anticlockwise direction against the tab  37 .  FIG. 8   b  shows the condition whereby the paddle  16  has been used to rotate the drive shaft  22  by angle X. This rotation acts against the bias of the latch spring  72  and rotates the latch arm  20  by angle X moving the latch member  20  out of alignment with striker  15  such that the door may be opened (from the position shown in  FIG. 8   b ). 
     The torsional restoring force of the latch spring  72  acts to bias the latch member  20  back to the position shown in  FIG. 8   a . The torsional restoring force of the return spring  73  acts to bias the paddle back to its original position in order to avoid accidental damage as a result of its exposure. 
     The container  14  comprises a striker  15  (as shown in  FIG. 3 ) with which the panel latch  10  interacts in order to secure the door  12  in a closed position. The striker  15  may take many forms but is generally a metal member or bar attached to the container  14 . 
       FIGS. 9   a  to  9   c  show a slamming event whereby an open door is required to be closed by pushing on the paddle  16 . In this situation it is undesirable for the paddle  16  to move for the reasons discussed above. 
     In  FIG. 9   a , a force is applied to the door  12  or paddle latch  10  (usually by the paddle  16 ) in the direction shown by arrow F. In order for the latch member  20  to pass the striker  15 , the inclined surface on the latch head  70  slides along the striker  15 , causing the latch member  20  to rotate by angle Y as shown in  FIG. 9   b . As the orifice  84  defines a sector of a circle substantially larger than the semi-circular profile of the corresponding flat end section of the shaft  22 , the latch member  20  can rotate freely without engaging the drive shaft  22  against the resilient bias of the latch spring  72 . When the door has closed far enough for the latch head  70  to pass the striker  15 , the resilient bias of the latch spring  72  causes the latch member  20  to return to its position abutting the tab  37  as shown in  FIG. 90 . This entire sequence occurs without movement of the paddle  16 . 
     It should be understood that the angle of the sector defined by the orifice  84  should be greater than the maximum desired angle of rotation, Y, experienced when the door is closed in the manner described above. If this is not the case, then the latch member  20  will engage the drive shaft  22  actuating the paddle  16 , which is undesirable. 
     If, when in a closed position as shown in  FIG. 3 , it is desired that the paddle latch  10  should be locked such that the door  12  cannot be opened, then the lock  50  may be engaged in a blocking position such that the paddle  16  cannot move and therefore it would not be possible to actuate the latch member  20  by using the paddle  16 . However, it should also be noted that if the lock is engaged whilst the door  12  is open, then it is entirely possible to slam the door in the manner described above, as the latch member  20  can rotate without engaging the drive shaft  22 . Therefore, it is not possible to damage any of the components of the paddle latch  10  by slamming the door  12  when the lock  50  is engaged. 
     It should be understood that the interaction between the drive shaft  22  and the latch member  20  may be defined by a wide range of geometries. Any interaction between the drive shaft and the latch member that results in torque being transferred with relative rotation of the two components in a first direction (e.g. if the drive shaft  22  is rotated clockwise from  FIG. 8   a  to  FIG. 8   b ) but not in a second direction (e.g. if the latch member is rotated in a clockwise sense from  FIG. 9   a  to  FIG. 9   b ) is within the scope of the invention. Optionally, at the point at which the drive shaft and the latch member interact, the drive shaft cross-section may define a circle sector with a first included angle, and the orifice in the latch member a circle sector with a second included angle. As long as the second included angle is Y° above the first included angle, where Y° is the maximum desired angle of rotation of the latch member, then the latch will operate. In the embodiment described here, the first included angle is 180° (a semicircle) and the second included angle is (180+Y)°. It should be noted that the first included angle may vary greatly within the scope of the invention. Examples of alternative geometries of drive shafts and latch members are described below. 
       FIG. 10  shows an alternative embodiment of the device whereby drive shaft  122  comprises a spline-type cross section instead of a flat end section. The corresponding orifice  184  on latch member  120  defines a spline with wider grooves such that rotation of the drive shaft  122  in a clockwise fashion will engage the latch member  120  but corresponding motion of the latch member  120  will not cause rotation of the drive shaft  122 . 
       FIG. 11  shows another embodiment of the invention whereby the shaft  124  comprises a protrusion  126  and the latch member  122  comprises a corresponding protrusion  123  in orifice  186 , such that clockwise rotation of the shaft  124  causes corresponding rotation of the latch member  122  but clockwise rotation of the latch member  122  will not cause rotation of the drive shaft  124 . Alternatively, the protrusion  126  of the drive shaft  124  could be provided via a key and keyway assembly. 
     It will be appreciated that by using the shaft to transfer torque from the paddle to the latch member means that only the shaft needs to extend from the exterior of the housing through to the interior. Inherently, it is far easier to seal this type of opening through the housing than the openings of known paddle latches, resulting in a latch that is cost-effective to manufacture, whilst achieving the desired sealing properties. 
     Numerous changes may be made within the scope of the present invention. Two examples of alternative drive shaft/latch member interfaces have been given in  FIGS. 10 and 11 . The intention that any mechanical interface may be used as long as it provides torque transmission in a first direction but not in a second. Consequently, a large range of profiles of the drive shaft and corresponding orifice may be selected. 
     The lock  50  does not have to contact the housing to prohibit the movement of the paddle  16 , rather it may pass through the housing  18  and directly engage the latch member  20  when in a locked position. 
     The latch member  20  need not be in a vertical position when latched, the position may vary depending on the relative position of the paddle latch  10  and the striker  15 . 
     The biasing method used may vary from the torsional latch spring  72 . For example, a linear compression spring may be used between the latch member  20  and a corresponding surface of the housing  18 . 
     Different methods may be used to provide the mechanical connection between the paddle  16  and the drive shaft  22 . The grub screw  64  may be replaced with an interference fit between the drive shaft  22  and the paddle  16 . For example, the drive shaft  22  may be profiled to define a flat portion (such as seen in  FIG. 3   a  at  58 ) all the way along, and the paddle  16  may define a corresponding orifice such that rotation of the drive shaft  22  within paddle  16  is not possible. 
     This concept extends to the further examples shown in  FIGS. 10 and 11  whereby the features of the drive shaft may extend along its length and the passageway  54  of the paddle  16  and may be adapted to engage them. 
     The application of the paddle latch  10  is not limited to doors but may be any type of closure. Correspondingly, a resilient biasing means (in this case latch spring  72 ) may not be present at all and the paddle latch  10  may be mounted such that the latch member  20  is restored to its latch position by action of gravity, or other suitable means. 
     The lost motion created between the end sections  58 ,  60  of the drive shaft  22  and the orifices  84  of the latch arm  20  may alternatively exist between the centre portion  56  of the drive shaft  22  and an orifice in the hub portion  46  of the paddle  16 . In this instance, the drive shaft  22  and the latch member  20  would be fixably attached so as to rotate together. 
     In order to facilitate assembly, the drive shaft  22  may comprise two separate components for insertion at either side of the latch. In this way the drive shaft  22  would not have to pass all the way through the hub portion  46  of the paddle  16 . 
     The drive shaft o-rings  63  are provided to seal the circular orifices  35 . Alternatively, design tolerances and materials selection may be made such that sufficient relative motion and sealing is created without further sealing means. 
     The output from the shaft may be adapted to drive an alternative form of latch member, such as a sliding latch bolt. Also, either or both of the latch spring or the return spring may be replaced with resilient means integrated to the components which they bias. For example small, leaf-spring type structures could be machined in the orifices of the latch arm to interact with the drive shaft in this manner. 
     Locks are commonly employed in paddle latches for security reasons, but in certain embodiments may be omitted if so desired.

Summary:
A paddle latch comprising a housing defining a first side and a second side, a shaft extending through the housing defining a first shaft portion on the first side and a second shaft portion on the second side, a paddle for actuation by a latch user on the first side and a releasable latch member for co-operation with an associated striker to latch the paddle latch on the second side wherein the paddle is connected to the first shaft portion and the latch member is connected to the second shaft portion such that torque may be transferred from the paddle to the latch member to release the latch member from the striker in use.