Abstract:
A zipper has a slider moveable in an opening direction to open the zipper and in a closing direction to close the zipper. The slider comprises a control member and a casing, the control member being moveable between a locking position in which movement of the slider in the opening direction is prevented and an unlocking position in which movement of the slider in the opening direction is allowed. When the control member is in the locking position the casing at least partially encloses the control member so as to substantially prevent the application of a contact force tending to move the control member from the locking position to the unlocking position. The control member is at least partly formed of a material to which a magnetic force is applied by a permanent magnet in proximity.

Description:
BACKGROUND 
     A commonplace type of zipper comprises two rows of inter-lockable elements (or teeth) and a slider which can be moved in an opening direction to open the zipper and in a closing direction to close the zipper. 
     Examples of such zippers are disclosed in U.S. Pat. No. 2,599,078 and U.S. Pat. No. 5,255,418. Each of these documents discloses a zipper that has a slider which includes an automatic locking mechanism that serves to prevent unintentional movement of the slider in the opening direction. In each case, the locking mechanism includes a control member that is moveable from a locking position, in which movement of the slider in the opening direction is prevented, to an unlocking position. Movement of the control member from the locking position to the unlocking position is achieved by application of a force to the control member via a pull tab which physically engages the control member. In both U.S. Pat. No. 2,599,078 and U.S. Pat. No. 5,255,418, the control member has a pin, formed integrally with the control member, the pin interposing between the elements of the zipper to achieve the locking. 
     Other zippers have sliders that are provided with security locking mechanisms incorporating combination locks or key operated locks and which allow the slider to be locked to prevent unauthorised opening of the zipper. 
     SUMMARY 
     According to a first aspect of the invention, there is provided a zipper having a slider moveable in an opening direction to open the zipper and in a closing direction to close the zipper, the slider comprising a control member and a casing, the control member being moveable between a locking position in which movement of the slider in the opening direction is prevented and an unlocking position in which movement of the slider in the opening direction is allowed, wherein when the control member is in the locking position the casing at least partially encloses the control member so as to substantially prevent the application of a contact force tending to move the control member from the locking position to the unlocking position, the control member being at least partly formed of a material to which a magnetic force is applied by a permanent magnet in proximity whereby to allow the control member to be moved from the locking position to the unlocking position by application of a magnetic force to the control member. 
     According to a second aspect of the invention, there is provided a slider for a zipper, comprising a control member and a casing, the control member being moveable between a locking position for preventing opening of a zipper incorporating the slider and an unlocking position for allowing opening of the zipper, wherein when the control member is in the locking position the casing at least partially encloses the control member so as to substantially prevent the application of a contact force tending to move the control member from the locking position to the unlocking position, the control member being at least partly formed of a material to which a magnetic force is applied by a permanent magnet in proximity whereby to allow the control member to be moved from the locking position to the unlocking position by application of a magnetic force to the control member. 
     As used herein the term “contact force” refers to a mechanical force applied through physical contact between two solid objects such as a force applied by pushing or mechanical engagement, or a force applied via friction, but does not extend to any force which requires adhesion between the two objects nor to magnetic attraction or repulsion between the two objects. 
     Proximity, as used herein encompasses both nearby but not touching, and also touching. 
     Preferably, in either the first or second aspects of the invention, the casing substantially fully encloses the control member. The control member is moveable from the locking position to the unlocking position by a magnetic force applied to the control member by a permanent magnet in proximity to and external to the casing. 
     According to a third aspect of the invention, there is provided a zipper having a slider moveable in an opening direction to open the zipper and in a closing direction to close the zipper, the slider comprising a control member and a casing, the control member being moveable between a locking position in which movement of the slider in the opening direction is prevented and an unlocking position in which movement of the slider in the opening direction is allowed, the casing substantially fully enclosing the control member, the control member being at least partly formed of a material to which a magnetic force is applied by a permanent magnet in proximity whereby to allow the control member to be moved from the locking position to the unlocking position by application of a magnetic force to the control member by a permanent magnet in proximity to and external to the casing. 
     According to a fourth aspect of the invention, there is provided a slider for a zipper, comprising a control member and a casing, the control member being moveable between a locking position for preventing opening of a zipper incorporating the slider and an unlocking position for allowing opening of the zipper, the casing substantially fully enclosing the control member, the control member being at least partly formed of a material to which a magnetic force is applied by a permanent magnet in proximity whereby to allow the control member to be moved from the locking position to the unlocking position by application of a magnetic force to the control member by a permanent magnet in proximity to and external to the casing. 
     Unless otherwise stated, the following preferred features are independent of one another and are applicable to all aspects of the invention. 
     Preferably, the magnetic force is magnetic attraction. The material is preferably a ferrite material. The casing is preferably formed of a non-magnetic material. 
     Preferably, the slider is provided with means for resiliently urging the control member into the locking position. Where such resilient urging means are provided, it is desirable for the slider to have a detent mechanism operable to hold the control member in the unlocking position, against the resilient urging means, once the control member has been moved to the unlocking position. 
     Preferably, the slider is provided with a button which can be operated directly by hand to move the control member from the unlocking position to the locking position. The button may be part of the casing. Where both a button and a detent mechanism are provided, operation of the button over-rides the detent mechanism to move the control member from the unlocking position to the locking position. 
     Preferably, the zipper has two rows of inter-lockable elements and the slider includes a locking member moveable between a locking position and an unlocking position. When the locking member is in the locking position, the locking member is interposed between the elements to prevent sliding movement of the slider in the opening direction and when the locking member is in the unlocking position the slider is slideable in the opening direction to open the zipper. Movement of the control member from the locking position to the unlocking position causes or allows the locking member to move from the locking position to the unlocking position. 
     Where such a locking member is provided, the control member is preferably operatively linked to the locking member so that movement of the control member from the locking position to the unlocking position causes the locking member to move from the locking position to the unlocking position. This can be achieved by magnetic attraction between the control member and the locking member. 
     Where a locking member is provided, the locking member preferably has a pivot portion and a pin portion. The locking member pivots between the locking position and the unlocking position substantially around a point defined by the pivot portion and the pin portion is interposed between elements to prevent movement of the slider in the opening direction when the locking member is in the locking position. 
     Preferably, the slider defines a Y-shaped channel for receiving two rows of zipper elements. In this case, the slider includes a locking pin which projects into the Y-shaped channel when the control member is in the locking position. Preferably, the locking pin is at least partially retracted from the Y-shaped channel when the control member is in the unlocking position. 
     According to a fifth aspect of the invention, there is provided a kit comprising a zipper according to the first or third aspects of the invention and a permanent magnet for moving the control member from the locking position to the unlocking position. 
     According to a sixth aspect of the invention, there is provided a security bag comprising a bag closed by a zipper according to the first or third aspects of the invention. The bag is preferably formed at least partially from a transparent plastics material so as to allow the contents of the bag to be viewed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following is a more detailed description of embodiments of the invention, by way of example, reference being made to the appended schematic drawings in which: 
         FIG. 1  is an isometric drawing from above showing a slider of a zipper; 
         FIG. 2  is a front elevation of the slider of  FIG. 1 ; 
         FIG. 3  is a representation, partially in cross-section, showing the slider of  FIGS. 1 and 2  in a locking configuration and also showing some elements of the zip; 
         FIG. 4  is a representation, partially in cross-section, showing the slider of  FIGS. 1 to 3  in an unlocking configuration, and also showing some elements of the zipper; 
         FIG. 5  is a similar view to  FIG. 4 , showing a retail magnet detacher in close proximity to the top of the slider; and 
         FIG. 6  shows the zipper incorporated in a security bag. 
     
    
    
     Referring first to  FIGS. 1, 2 and 6 , the zipper comprises two rows  10 ,  12  of inter-lockable elements  13  and a slider  14 . The two rows  10 ,  12  of inter-lockable elements  13  are conventional in design and will not be described in detail. The elements  13  of each row  10 ,  12  may be, for example, metal or plastic elements  13  mounted, in a known manner, on a plastic strip so as to form the row  10 ,  12 . 
     DETAILED DESCRIPTION 
     The slider  14  is engaged with the two rows  10 ,  12  of elements  13  so that the slider  14  can be slid both in an opening direction, so as to open the zipper, and also in a closing direction, so as to close the zipper. 
     Referring now to  FIGS. 1 to 4 , the slider  14  has a bottom plate  16 , a top plate  18  and a separator  20  which connects the bottom plate  16  and the top plate  18  and which holds the two plates  16 ,  18  mutually parallel to and spaced from one another. 
     As best seen in  FIG. 2 , the bottom plate  16  has two flanges  22  and the top plate  18  has two flanges  24 . In a conventional manner, the bottom plate  16 , the top plate  18 , the separator  20 , the bottom plate flanges  22  and the top plate flanges  24  together define a Y-shaped channel  26  which receives the two rows  10 ,  12  of elements  13 . At the rear of the slider  14  (see  FIG. 1 ), the Y-shaped channel  26  has a rear opening  28  through which extend the two rows  10 ,  12  of elements  13  in an inter-locked state (seen in  FIG. 6 ). At the front of the slider  14  (see  FIG. 2 ) the Y-shaped channel  26  has two front openings  30 ,  32 , through which extend respective ones of the two rows  10 ,  12  of elements  13  in a disengaged state (not shown). 
     The opening direction of movement of the slider  14  corresponds to movement of the slider  14 , relative to the two rows  10 ,  12  of elements  13 , from the right hand side to the left hand side as shown in  FIG. 4 . Conversely, the closing direction of movement of the slider  14  corresponds to movement of the slider  14 , relative to the two rows  10 ,  12  of elements  13 , from the left hand side to the right hand side as shown in  FIG. 4 . The manner in which the slider  14  opens and closes the zipper is conventional. 
     Referring to  FIGS. 1 to 4 , the top plate  18  is generally disc-shaped. An upper surface of the top plate  18  is formed with a first recess  34 , a second recess  36 , and an aperture  38  which extends from the bottom of the second recess  36 , completely through the top plate  18 , to a lower surface of the top plate  18 . 
     A cylindrical wall  40  is fixed to the upper surface of the top plate  18 , around the periphery of the top plate  18 . An upper end of the cylindrical wall  40  is provided with an inwardly projecting flange  42  and an opening  44 . A button  46  fits within the opening  44 . The button  46  is provided with a flange  48  which cooperates with the flange  42  on the cylindrical wall  40  to prevent the button  46  from moving in an upward direction, as shown in  FIGS. 3 and 4 , out of the opening  44 . The button  46  and the cylindrical wall  40  are formed of a plastics material. 
     As seen in  FIGS. 3 and 4 , the slider  14  has a pivoting locking member  50 . The locking member  50  is formed of stainless steel and has, at one end, a pivoting portion  52 . The pivoting portion  52  is received in the first recess  34  of the top plate  18  so as to allow the locking member  50  to pivot generally around the pivoting portion  52 . The locking member  50  also has a body portion  54  from which projects a locking pin  56 . As best seen in  FIG. 3 , the body portion  54  of the locking member  50  is shaped so as to be received within the second recess  36  of the top plate  18 , whereupon the locking pin  56  projects through the aperture  38  of the top plate  18 . 
     Still referring to  FIGS. 3 and 4 , the slider  14  also includes a control member  58 . The control member  58  has a cup portion  60  with an open end facing upwardly towards the button  46  and a closed end facing downwardly towards the top plate  18 . The cup portion  60  is also made of stainless steel. A small disc-shaped permanent magnet  62  is fixed inside the cup portion  60  at the closed end of the cup portion  60 . A first helical spring  64  is held within the cup portion  60  and acts between the disc-shaped magnet  62  and the button  46  so as to urge the control member  58  downwardly into contact with the body portion  54  of the pivoting locking member  50 . 
     The slider  14  also includes a detent  66 . The detent  66  includes a cup portion  68  which has an open end facing towards the cylindrical wall  40  and a closed end facing generally towards the control member  58 . A rounded head  70  is provided on the closed end of the cup portion  68 . A second helical spring  72  is held within the cup portion  68  and acts between the cup portion  68  and the cylindrical wall  40  to urge the cup portion  68  and the rounded head  70  towards the control member  58 . The cup portion  68  and the rounded head  70  of the detent  66  are formed of a plastics material. 
     Although not shown for the purpose of clarity, the slider  14  may also be provided with various internal walls or structures serving to hold the control member  58  and the detent  66  in the correct positions, so as to allow movement of the control member  58  and the detent  66  between the positions shown in  FIGS. 3 and 4 . 
     The operation of the zipper will now be described. 
     The natural configuration of the slider  14  is the locking configuration that is shown in  FIG. 3 . In this locking configuration, the cup portion  60  of the control member  58  is held downwardly by the first helical spring  64 , so that the cup portion  60  bears against the body portion  54  of the pivoting locking member  50 . In turn, the pivoting locking member  50  is held down by the control member  58  so that the body portion  54  lies within the second recess  36  of the top plate  18  and the locking pin  56  passes through the aperture  38  in the top plate  18 . As seen in  FIG. 3 , the locking pin  56  is interposed between elements  13  from the two rows  10 ,  12  of elements  13 . 
     The locking pin  56  has a first planar surface  74  which, when the pivoting locking member  50  is in the locking position shown in  FIG. 3 , lies perpendicular to the two rows  10 ,  12  of elements  13 . Contact between the planar surface  74  and one of the elements  13  of the two rows  10 ,  12 , prevents sliding movement of the slider  14  in the opening direction (that is to say from the right hand side to the left hand side as shown in  FIG. 3 ). 
     The locking pin  56  also has an angled surface  76 . When the pivoting locking member  50  is in the locking position, as shown in  FIG. 3 , the angled surface  76  is inclined in relation to the two rows  10 ,  12  of elements  13 . If a force is applied to the slider  14 , tending to move the slider  14  in the closing direction (from left to right as shown in  FIG. 3 ), the angled surface  76  cams against an element  13  of the two rows  10 ,  12  and this, in turn, causes the pivoting locking member  50  to pivot so that locking pin  56  is disengaged from between the elements  13  of the two rows  10 ,  12 . In this way, as the slider  14  is moved in the closing direction, the pivoting locking member  50  acts as a pawl, ratcheting against the elements  13  of the two rows  10 ,  12 . Any attempt to move the slider  14  in the opening direction causes the locking pin  56  to lock against an element  13  of the two rows  10 ,  12  thereby preventing opening of the zipper. This is achieved because the control member  58 , under the operation of the first helical spring  64 , bears against the pivoting locking member  50 , urging the pivoting locking member  50  into the locking position shown in  FIG. 3 . 
     As seen in  FIGS. 3 and 4 , the control member  58  is substantially entirely enclosed within a casing consisting of the cylindrical wall  40 , the button  46  and the top plate  18 . The fact that the control member  58  is encased means that it is not possible to contact the control member  58  with either a finger or a tool such as a screwdriver, so as to move the control member  58  upwardly out of the locking position shown in  FIG. 3 . 
     In order to unlock the slider  14  from the locked configuration shown in  FIG. 3  to the unlocked configuration shown in  FIG. 4 , it is necessary to use a powerful permanent magnet, as shown in  FIG. 5 .  FIG. 5  shows a detaching magnet  78  of a type that is commonly used in retail outlets to remove security tags from articles such as clothing. When the detaching magnet  78  is placed lightly against the button  46 , an attractive magnetic force acts between the detaching magnet  78  and the cup portion  60  of the control member  58  (the cup portion  60  being made of stainless steel). This magnetic force causes the cup portion  60  to move upwardly into an unlocking position against the button  46 , as shown in  FIGS. 4 and 5 . This movement causes the first helical spring  64  to become compressed. Once the cup portion  60  contacts the button  46 , the rounded head  70  of the detent  66  no longer engages the cup portion  60  and this allows the detent  66  to move, under the operation of the second helical spring  72 , in the right to left direction as shown in  FIGS. 3 to 5 . This movement, in turn, causes the rounded head  70  of the detent  66  to engage under the closed end of the cup portion  60  of the control member  58 . When in this position, the detent  66  prevents the control member  58  from moving back down towards the pivoting locking member  50 . Once the detent  66  has acted to hold the control member  58  in the unlocking position shown in  FIGS. 4 and 5 , the control member  58  remains in the unlocking position even if the detaching magnet  78  is removed. 
     The control member  58  no longer pushes down against the pivoting locking member  50 . The disc magnet  62  provided in the control member  58  attracts the pivoting locking member  50  (which is made of stainless steel) and causes the pivoting locking member  50  to pivot into the unlocking raised position shown in  FIGS. 4 and 5 . In this unlocking position, the locking pin  56  is no longer interposed between the elements  13  of the two rows  10 ,  12 . Hence, with the control member  58  in the unlocking position, the slider  14  can be moved freely in either the opening direction or the closing direction. 
     The slider  14  is returned to the locking configuration shown in  FIG. 3  by depressing the button  46 . When the button  46  is depressed, this pushes down the control member  58 . In turn, the cup portion  60  of the control member  58  bears down on the rounded head  70  of the detent  66  and this pushes the detent  66  back towards the cylindrical wall  40 , against the second helical spring  72 , so as to allow the control member  58  to move downwardly and into contact with the pivoting locking member  50 . During this operation, the rounded head  70  of the detent  66  moves back into contact with the circumferential surface of the cup portion  60  of the control member  58 . The control member  58 , under the force applied by the first helical spring  64 , pushes the pivoting locking member  50  back into the locking position shown in  FIG. 3 . Hence, again, movement of the slider in the opening direction is prevented. 
     Hence, the zipper is normally in a locking configuration, preventing unauthorised opening of the zipper. However, the zipper can be unlocked, using a strong permanent magnet of a type already commonly used in the retail trade, in a manner which is fast, easy and fool-proof. Unlike existing zippers which can be locked against unauthorised opening, there is no need to remember a code of a combination lock or to carry an appropriate key. The slider can be locked simply by pressing the button  46 . 
     A highly desirable use of the zipper is shown in  FIG. 6 .  FIG. 6  shows the zipper mounted on a bag  80  which is conveniently used as a security bag in a retail environment, such as in a supermarket. The bag  80  is formed of a tough plastics material which is resistant to ripping or cutting. The bag  80  is also transparent so that any product placed within the security bag can be readily viewed by a potential customer. The bag  80  may also be provided with a security tag designed to trigger an audible alarm if an attempt is made to carry the security bag  80  out of the retail environment. 
     In use, a product is placed within the bag and the zipper is closed by sliding the slider  14  in the closing direction. As the slider  14  is in the locking configuration shown in  FIG. 3 , the slider cannot be slid in the opposite opening direction to open the bag. When it is desired to remove the article from the bag, a shop worker can use the detaching magnet  78  to unlock the slider  14 , as discussed above, so as to allow the slider  14  to be slid in the opening direction. 
     It will be appreciated that many adaptations may be made to the zipper, or to the security bag, without departing from the scope of the invention as defined in the claims. 
     In one such adaptation, the detent  66  and the pivoting locking member  50  may be dispensed with. Instead, the control member  58  may be provided with a locking pin either firmly attached to the control member  58  or formed integrally with the control member  58 . The control member  58 , together with the associated locking pin, would then be permanently urged downwardly, by the helical spring  64 , so that the locking pin interposes between elements  13  of the two rows  10 ,  12 . In this way, the slider  14  would be locked against movement in the opening direction unless and until the detaching magnet  78  is placed against the slider  14  so as to move the control member against the first helical spring  64  into an unlocking position. In this adaptation, the control member  58  would move back into the locking position as soon as the detaching magnet  78  is removed. Accordingly, in this embodiment, it would be necessary to hold the detaching magnet  78  against the slider during the whole time that the slider was being moved in the opening direction. 
     In another alternative embodiment, it is not necessary for the control member to be fully enclosed. The control member could, for example, take the form of a metal cylinder. Instead of the casing described above, the control member would fit closely within a cylindrical tube having an open end. The control member could then be lifted into an unlocking position by inserting a cylindrical magnet into the open end of the tube, so as to bring the magnet into contact with the control member, and then pulling the magnet upwardly so as to pull the control member upwardly into an unlocking position. The cylindrical tube would prevent a thief from obtaining purchase on the control member either with his fingers or with a tool, as only the planar end surface of the cylindrical locking member would be accessible.