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TECHNOLOGICAL FIELD 
       [0001]    The invention relates to locks, in particular, locks having a bolt made of two elements, displaceable with respect to one another. 
       BACKGROUND ART 
       [0002]    Combination locks commonly comprise a mechanism requiring the input of a certain combination code (buttons pressed at a certain order, combination of digits etc.), subject to which a latch of the lock is free to displace into an open position thereof. 
         [0003]    One example of a combination lock is disclosed in U.S. Pat. No. 6,718,803 to the Applicant. 
         [0004]    Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter. 
       GENERAL DESCRIPTION 
       [0005]    In accordance with one aspect of the subject matter of the present application, there is provided a lock comprising a housing, a locking mechanism, a locking member configured for displacement with respect to the housing between a closed position and an open position, defining respective open and closed states of the lock, and a bolt configured for displacing between an unlocked position in which the locking member is free to displace between its closed and open positions, and a locked position in which the bolt prevents displacement of the locking member between its open and closed positions, wherein said bolt comprises a follower and an arresting bar attached to one another and configured for displacement as a single body, the follower being configured for engaging a portion of the locking member and wherein:
       in an unblocked state of the locking mechanism, in which the arresting bar is free to displace, displacement of the locking member from the closed position to the open position entails displacement of the entire bolt to its unlocked position, and;   in a blocked state of the locking mechanism, in which the arresting bar is prevented from displacement, displacement of the locking member from the closed position to the open position entails disengagement of the follower from the arresting bar, leaving the arresting bar in an arrested position, preventing further displacement of the locking member into its open position.       
 
         [0008]    In general, the locking mechanism is configured, upon providing the proper input (inserting the right key, setting the right combination, pressing buttons in the right order etc.) for assuming an unblocked state, allowing the bolt to freely displace into its unlocked position by virtue of displacement of the locking member 
         [0009]    In particular, the lock can be a lock and comprise a locking mechanism similar to that disclosed, for example, in U.S. Pat. No. 6,718,803 to the Applicant. 
         [0010]    The follower and the arresting bar can be configured for disengagement with respect to one another under a predetermined threshold load applied to either of the two members. 
         [0011]    In particular, application of a load to the follower which is under the threshold load, will cause either of the following:
       displacement of the entire bolt (if the arresting bar is free to displace)—this is equivalent to pulling on the locking member in order to open the lock when the proper input has been provided; and   resistance of the bolt (if the arresting bar is prevented from displacement)—this is equivalent to pulling on the locking member in order to open the lock when the proper input has not been provided.       
 
         [0014]    However, when the arresting bar is held in place (i.e. when the proper input has not been provided), application of a load greater than the threshold load will entail disengagement of the follower from the arresting bar, bringing the lock into a malfunction state in which:
       the follower is in a position corresponding to an unlocked position of the bolt; and   the arresting bar is in a position corresponding to a locked position of the bolt, preventing displacement of the locking member into its open position.       
 
         [0017]    The threshold load can be determined based on the attachment arrangement between the follower and the arresting bar. 
         [0018]    In accordance with one design embodiment, engagement between the follower and the arresting bar is in the form of a fixed attachment, whereby disengagement between the follower and the arresting bar takes place as a result of mechanical failure of a fail element, e.g. tearing or breaking off, in which case the threshold load is determined according to the physical properties (material, geometry etc.) of the fail element. 
         [0019]    According to one example, the fail element can be constituted by a portion of one of the follower and arresting bar, received within a corresponding recess formed in the other of the components. In this case, when the threshold load (or greater) is applied, the fail element breaks off its component. 
         [0020]    According to another example, the fail element can be a separate element, independent of the follower and arresting bar, and configured for fixedly attaching them to one another. In this case, when the threshold load (or greater) is applied, mechanical integrity of the fail element is lost, and the follower is free to displace with respect to the arresting bar. 
         [0021]    In connection with the above, the fail element can be made of materials having a lower toughness or hardness compared to the follower. With particular reference to the first example, the arresting bar can be made of a hard metal having a first hardness and configured for preventing egress of the locking member into its open position, wherein the follower can be made of a metal having a second hardness, lower than the first hardness, and configured to fail under the threshold load. The follower can even be made of a softer material such as plastic etc. 
         [0022]    It is important to note that the fail element should be, on the one hand, sufficiently strong in order to maintain engagement with the arresting bar during normal operation of the lock and transfer the loads applied thereto by the cam portion of the locking member to the arresting bar in order for the bolt to displace properly, and, on the other hand, to be sufficiently softer than the arresting bar so as to tear/break under the application of the threshold load or higher. 
         [0023]    In accordance with another design embodiment, engagement between the follower and the arresting bar is in the form of a coupling, whereby disengagement between the follower and the arresting bar takes place as a result of decoupling, in which case the threshold load is determined according to the strength of the coupling. 
         [0024]    The follower can have at least one follower surface configured for engaging a corresponding cam portion of the locking member. In particular, the arrangement can be such that axial movement of the locking member (during engagement between the cam portion and the follower surface) entails lateral movement of the follower, and, subsequently, of the entire bolt. 
         [0025]    Thus, it is appreciated that the interaction between the locking member and the bolt is achieved via engagement between the locking member and the follower, i.e. in the unlocked state displacement of the locking bar entails displacement of the bolt via engagement with the follower. 
         [0026]    Thus, the arresting bar of the bolt takes no operative part in engagement with the locking member and in affecting said displacement, and serves as a passive component, being driven owing to its attachment to the follower (both moving as a single body). 
         [0027]    Therefore, the bolt is configured for performing at least the following basic functions, each configured for being performed by a different, independent component of the bolt:
       displacement—performed by the bolt owing to the engagement between the locking member and the follower; and   arresting the locking member—performed by the arresting bar.       
 
         [0030]    Thus, the follower can be designed according to specific requirements associated with the displacement of the bolt while the arresting bar can be designed according to specific requirements associated with the ability of the arresting bar to block the locking member. In particular, the materials of which each of the arresting bar and the follower are made can be chosen in accordance with their designated function. 
         [0031]    This arrangement can provide the lock with several unique advantages, which cannot be achieved if the entire bold is constituted by a single body made of a single material. For example, while the arresting bar can be required to be made of a sufficiently strong/hard/tough material in order to withstand forced prying of the lock (pulling out of the locking member by force), the follower can be required to be made of a material providing low friction with the locking member in order to reduce wear and tear of the lock during repeated operation. 
         [0032]    If the entire bolt were made of a single material, the advantages associated with the operation of displacement of the bolt could have yielded disadvantages in terms of the operation of arresting of the bolt, and vise versa, advantages associated with the operation of arresting of the bolt could have yielded disadvantages in terms of the operation of displacement of the bolt. 
         [0033]    In accordance with a particular example, the arresting bar of the bolt can be made of a material having a hardness, for example, a range of hard metals or steels chosen according to the required security level of the lock. The hardness can be chosen to meet specific security level standards. 
         [0034]    The follower can be made of a material having a low friction coefficient allowing smooth engagement with the locking member. More specifically, the material of the follower can be chosen from a variety of polymeric and non-polymeric materials, including (but not limited to) rubber and plastic materials. It should be noted here that since the follower is designed so as to reduce friction against the locking member, the reference to ‘material’ can also refer to a coating/s applied to the follower in order to reduce friction. 
         [0035]    Thus, according to another aspect of the subject matter of the present application there is provided a lock comprising a housing, a locking mechanism, a locking member configured for displacement with respect to the housing between a closed position and an open position, defining respective open and closed states of the lock, and a bolt configured for displacing between an unlocked position in which the locking member is free to displace between its closed and open positions, and a locked position in which the bolt prevents displacement of the locking member between its open and closed positions, wherein said bolt comprises a follower and an arresting bar attached to one another and configured for displacement as a single body owing to engagement between the locking member and the follower, wherein the follower and the arresting bar comprise different materials. 
         [0036]    The locking member can pass at least through the arresting bar such that, in the closed position, at least its cam portion is located axially beyond the arresting bar. Correspondingly, the arresting bar be formed with an opening having an egress portion configured for allowing axial removal of the cam portion through the arresting bar, thereby bringing the lock into its open state, and an arresting portion configured for preventing axial removal of the cam portion through the arresting bar. 
         [0037]    The arrangement is such that in the locked position of the bolt, the arresting portion of the opening is aligned with the cam portion of the locking member, and in the unlocked position of the bolt, the egress portion of the opening is aligned with the cam portion of the locking member. 
         [0038]    In operation, from the closed state of the lock and locked position of the bolt, axial displacement of the locking member entails engagement of the cam portion with the follower. This may yield the following:
       if the locking mechanism is in an unblocked state, displacement of the bolt from its locked position to its unlocked position, bringing the egress portion of the opening to become aligned with the cam portion of the locking member, allowing the later to be removed from arresting bar and brought to the open position; and   if the locking mechanism is in a blocked state, an attempt to displace the follower to an unlocked position of the bolt. However, since the arresting bar is prevented from displacement, this yields a load on the follower, which:
           if the load is below the threshold, nothing happens, i.e. the bolt remains in place; and   if the load is above the threshold, displacement of the follower with respect to the arresting bar.   
               
 
         [0043]    In both cases, the arresting portion of the opening remains aligned with the cam portion of the locking member, thereby preventing its egress from the arresting bar, which, in turn, leaves the lock closed. 
         [0044]    It is appreciated that in the second example, the lock becomes malfunctioned, as the follower disengages from the arresting bar and therefore cannot affect it anymore to displace into the unlocked position. Thus, this renders the lock jammed&#39; and unusable. 
         [0045]    In accordance with a specific design embodiment, the lock can be a padlock, whereby the locking member can be a shank constituting a portion of a U-shaped shackle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0046]    In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
           [0047]      FIG. 1  is a schematic isometric view of a lock; 
           [0048]      FIG. 2  is a schematic front view of the lock shown in  FIG. 1 , with a front cover thereof being removed; 
           [0049]      FIG. 3A  is a schematic isometric view of a locking assembly of the locking mechanism shown in  FIGS. 1 and 2 , in the closed position thereof; 
           [0050]      FIG. 3B  is a schematic front view of the locking assembly shown in  FIG. 3A ; 
           [0051]      FIG. 3C  is a schematic front view of the locking assembly of the locking mechanism shown in  FIGS. 1 and 2 , shown in mid way between its closed and open positions; 
           [0052]      FIG. 3D  is a schematic top view of the locking assembly shown in  FIG. 3C ; 
           [0053]      FIG. 3E  is a schematic front view of the locking assembly of the locking mechanism shown in  FIGS. 1 and 2 , shown in a ‘malfunction position’ thereof; 
           [0054]      FIG. 4A  is a schematic front view of a bolt of the locking assembly shown in  FIG. 3A ; 
           [0055]      FIG. 4B  is a schematic front view of a bolt of the locking assembly shown in  FIG. 3E ; 
           [0056]      FIG. 5A  is a schematic isometric view of the bolt shown in  FIG. 4A ; 
           [0057]      FIG. 5B  is a schematic rear isometric view of the bolt shown in  FIG. 5A ; 
           [0058]      FIG. 6A  is a schematic isometric view of the bolt shown in  FIG. 4B ; 
           [0059]      FIG. 6B  is a schematic rear isometric view of the bolt shown in  FIG. 6A ; 
           [0060]      FIG. 7A  is a schematic exploded view of the combination lock shown in  FIG. 1 ; 
           [0061]      FIG. 7B  is a schematic exploded view of the combination lock shown in  FIG. 7A , with the internal mechanism removed; 
           [0062]      FIG. 8A  is a schematic cross-section view of a portion of the housing of the combination lock shown in  FIG. 7B ; and 
           [0063]      FIGS. 8B and 8C  are schematic enlarged views of details shown in  FIG. 8A . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0064]    It is appreciated that although the specific examples shown in and described with respect to the above mentioned figures refer to a combination lock, the subject matter of the present application can be implemented in any type of lock in which a bolt is incorporated. 
         [0065]    Attention is first drawn to  FIGS. 1 and 2  in which a combination lock is shown, generally designated  1 , and comprising a housing  10  and a shackle  20  configured for displacing between a locked position and an unlocked position, by virtue of entering the proper combination to the lock  1 . 
         [0066]    Turning now to  FIGS. 3A to 3E , the shackle  20  comprises a shackle body  22 , a shank  24 , and a cam portion  25  formed with a first cam surface  26  and a second cam surface  28 . 
         [0067]    The lock  1  further comprises a bolt  30  received within the housing, and configured for selectively engaging the shackle  20  in order to prevent retraction thereof from the housing  10 , and consequently preventing unlocking of the lock  1 . 
         [0068]    With particular reference being made to  FIG. 3B , the bolt  30  comprises a follower  40 , made of generally soft material (e.g. plastic) and an arresting bar  50  made of metal. The follower  40  and the arresting bar  50  are adjoined to one another via a tenon and mortise arrangement so that they are configured for displacing together as a single body. 
         [0069]    In particular, the bolt  30  is configured for performing a lateral displacement between a first position preventing extraction of the cam portion  25  from the housing  10  and a second position allowing such extraction. 
         [0070]    With additional reference being made to  FIGS. 3C and 3D , the follower  40  has a body  42  formed with a follower portion  44  having a follower surface  46 , and comprises a fail element  48  serving as the tenon. The arresting bar  50  also comprises a body  52 , an opening formed with an egress portion  54  and an arresting portion  56 , and a recess  58  serving as the mortise for the fail element  48 . 
         [0071]    Reverting now to  FIG. 3B , the lock  1  is shown in a locked position, where the cam portion  25  of the shank  24  is received axially under the arresting portion  56  of the opening of the arresting bar  50 , thereby preventing extraction of the shank  24  from the housing  10 . 
         [0072]    From this position, pulling on the shackle  24  entails axial movement of the cam portion  25  in an upwards direction. As a result, the cam surface  26  bears against the corresponding cam surface  46  of the follower  40 , applying a load thereto attempting to displace the follower  40  laterally to the right. 
         [0073]    Assuming a proper combination has been entered into the lock, the arresting bar  50  is free to displace together with the follower  40 , resulting in the lateral rightward movement of the entire bolt  30  to the position shown in  FIGS. 3C and 3D . 
         [0074]    In the position shown in these figures, the bolt  30  has displaced to a sufficient amount so that the cam portion  25  of the shank  24  is located directly under the egress portion  54 , allowing further extraction of the cam portion  25 , thereby unlocking the lock  1 . 
         [0075]    It is also noted that in this position, both follower  40  and arresting bar  50  maintain the same relation with respect to one another (i.e. have no relative displacement therebetween), as more clearly shown in  FIGS. 4B, 5A and 5B . 
         [0076]    However, from the same position shown in  FIG. 3B , if the proper combination has not been entered into the lock, the arresting bar  50  will be prevented from displacement together with the follower  40 . As a result, pulling on the shank  24  and applying a load to the follower  40  will result in the lateral rightward movement only of the follower  40 , without the arresting bar  50 , on account of tear or breaking off of the fail element  48  and disengagement of the follower  40  from the arresting bar  50 . 
         [0077]    As a result, the lock  1  will assume the position shown in  FIGS. 3E, 4B, 6A and 6B . In this position, the arresting bar  50  remains in the same position as it was, whereby the arresting portion  56  of the opening thereof is located above the cam portion  25  of the shank  24 , preventing extraction of the shank  24  from the housing  10 . 
         [0078]    It should be noted that in order to allow opening of the lock, the arresting bar  50  should be displaced laterally. This displacement is originally induced by displacement of the follower  40  (due to its connection with the bar  50  via the fail element  48 ), and displacement of the follower is induced by its interaction with the cam portion  25  of the shackle  20 . 
         [0079]    This, once the follower  40  is disengaged from the arresting bar  50 , the latter cannot displace into a desired position and the lock  1  becomes ‘jammed’. The housing  10  does not allow access to the arresting bar  50  (for security reasons) and therefore the lock  1  becomes ‘damaged’ or ‘malfunctioned’ with now way of reverting it back to its original position. 
         [0080]    It is also noted that the structural integrity of the fail element  48  is designed according to the expected loads applied to the arresting bar  50  by the follower  40 . In other words, the fail element  48  is configured for failing under the application of a load above a certain threshold, which defines the difference between a ‘gentle’ pull on the shackle and a violent attempt of pulling out the shackle by force. 
         [0081]    Turning now to  FIGS. 7A and 7B , an exploded view of the combination lock  1  is provided, in the latter of which the combination mechanism  101  is removed for clearer representation. 
         [0082]    It is observed that the combination mechanism  101  is retained within a housing comprising a first housing component  110  and a second housing component  120  configured for forming a full enclosure of the combination mechanism  101 . 
         [0083]    Each of the housing components  110 ,  120  is in the form of a shell  112 ,  122  respectively, each such shell  112 ,  122  having a first port  114 ,  124  configured for receiving therein a first leg of the shackle  20  and a second port  116 ,  126  configured for receiving therein the second leg of the shackle  20 . 
         [0084]    The first shell  112  is configured for being received within the second shell  122  so that the first ports  114 ,  124  are aligned with one another and the second ports  116 ,  126  are also aligned with one another, allowing insertion of the legs of the shackle through both ports simultaneously. 
         [0085]    Turning now to  FIGS. 8A to 8C , a cross-section of the assembled combination lock is shown in which the first sheconstitutes occupies an external part of the housing. A first sleeve  130  is inserted through the first ports  114 ,  124  and a second sleeve  140  is inserted through the second ports  116 ,  126 . 
         [0086]    In assembly, once the sleeves  130 ,  140  are inserted into the above ports, a purposed tool is used to form outer and inner flange portions for each of the sleeves— 134 ,  136  for the first sleeve  130  and corresponding  144 ,  146  for the second sleeve  140 . 
         [0087]    The flange portions prevent axial displacement of the sleeves  130 ,  140  with respect to the ports, and also facilitate securing the two shells  112 ,  122  to one another in a manner closing off the housing and preventing access to the combination mechanism  101 . 
         [0088]    It is noted that the presence of the sleeve within the ports prevents lateral displacement of the housing components  112 ,  122  with respect to one another, thereby preventing disengagement of the components from one another and disassembly of the housing. 
         [0089]    In addition, the use of sleeves allows for the use of shackles  20  of various diameters (of the cross-section of the leg of the shackle) using the same housing components  110 ,  120 . Specifically, if a smaller diameter of the shackle is required, a thicker sleeve can be used so that the shackle leg and sleeve made up a diameter corresponding to that of the ports. 
         [0090]    Furthermore, the arrangement of housing components  110 ,  120  which are separate from the combination mechanism (used only to encapsulate it), allows for simplifying manufacture and reducing costs during the quality assurance tests etc. Specifically, such tests can be performed on the combination mechanism  101  itself (without the encapsulating shell), and once performed, the combination mechanism can be encapsulated in the housing. 
       Components 
       [0000]    
       
           1 —lock 
           10 —housing 
           20 —locking member 
           22 —shackle body 
           24 —shank 
           25 —cam portion (head) 
           26 —cam surface 
           28 —cam surface 
           30 —bolt 
           40 —follower 
           42 —follower plate 
           44 —follower portion 
           46 —follower surface 
           48 —fail element 
           50 —arresting bar 
           52 —arresting plate 
           54 —egress portion of the opening 
           56 —arresting portion of the opening 
           58 —recess (for receiving the fail element) 
           101 —combination mechanism 
           110 —first housing component 
           112 —first shell 
           114 —first port of the first housing component 
           116 —second port of the first housing component 
           120 —second housing component 
           122 —second shell 
           124 —first port of the second housing component 
           126 —second port of the second housing component 
           130 —first sleeve 
           132 —sleeve body 
           133 —inner surface of the first sleeve body 
           134 —outer flange of the first sleeve 
           136 —inner flange of the first sleeve 
           140 —second sleeve 
           142 —sleeve body of the second sleeve 
           143 —inner surface of the second sleeve body 
           144 —outer flange of the second sleeve 
           146 —inner flange of the second sleeve

Summary:
Provided is a lock including a housing, a locking mechanism, and a locking member configured for displacement with respect to the housing between a closed position and an open position, defining respective open and closed states of the lock. The lock further includes a bolt configured for displacing between an unlocked position in which the locking member is free to displace between its closed and open positions, and a locked position in which the bolt prevents displacement of the locking member between its open and closed positions. The bold bolt includes a follower and an arresting bar attached to one another and configured for displacement as a single body owing to engagement between the locking member and the follower. The follower and the arresting bar include different materials.