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This Application claims the benefit of U.S. Provisional Application No. 61/892,005, filed Oct. 17, 2013. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to locks and to other security devices that use locks and locking mechanisms. The present invention also relates to air brakes and air brake securing devices. More specifically, the present invention relates to a tamper-proof air brake securing device and assembly that is used with air brake control knobs of the type that are mounted to the dashboard of a tractor vehicle and are used to release the air brakes of the vehicle, which brakes are used to hold a parked tractor, or a parked tractor-trailer combination, against movement. 
     BACKGROUND OF THE INVENTION 
     Air brakes have long been used on heavy duty vehicles for purposes of efficiency and ease of replenishment, since air is always available. In the case of air brakes, pressurized air is used for braking and for preventing vehicles from being moved. In the case of the latter, air brakes prevent vehicle movement by locking the wheels of the vehicle. Such air brakes are set or engaged typically by pulling an air control knob of the air brake plunger outwardly from the dashboard and disengaged by pushing the knob inward or toward the dashboard. Two knobs are typically provided. One knob controls the brakes of the tractor. The other knob controls the brakes of the trailer. The function of the knobs is to control the flow of air for setting or releasing the parking brakes. 
     One problem with such air brake systems is that the air brake actuation knobs can be tampered with. In order to prevent this type of tampering, devices have been attempted in an effort to disable or prevent each control knob from being actuated. 
     SUMMARY OF THE INVENTION 
     What is needed is a device or assembly for securely and inexpensively locking the air brake actuation knobs to prevent the knobs from being actuated. The present invention provides such an assembly that, when used properly, helps to prevent the air brake actuation knobs from being actuated. The present invention provides for a unique locking assembly having a number of components that form such assembly. The air brake lock in accordance with the present invention is a theft-prevention device that mounts over the air brake knobs on the dash of a semi-truck cab. The air brake lock assembly of the present invention is installed between the dash and the knobs and, when locked, the assembly prevents the knobs from being pushed in. If the air brake knobs cannot be pushed back in, the air brake will remain locked and the truck and trailer will remain immobile. In one embodiment of the present invention, the assembly includes a base and an enclosure for each brake knob. An air brake lock is disposed between the knobs such that the knobs can be selectively locked and unlocked. In one embodiment, the assembly is spring-loaded. In another embodiment, the assembly is not spring-loaded. Other alternative embodiments are disclosed as well, all with the goal of creating a product that is easy to install and easy to operate. Features of one alternative embodiment may also be incorporated into another embodiment and such is not a limitation of the present invention. 
     The foregoing and other features of the air brake lock assembly of the present invention will be apparent from the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top perspective view of the first embodiment of an air brake lock assembly that is constructed in accordance with the present invention. 
         FIG. 2  is a perspective view of the assembly shown in  FIG. 1  and illustrating a cross-sectioned view of the assembly structure. 
         FIG. 3  is a perspective view of the top of a portion of the assembly shown in  FIG. 1 . 
         FIG. 4  is a perspective view of the bottom of that portion of the assembly shown in  FIG. 3 . 
         FIG. 5  is another perspective view of the top of the assembly shown in  FIG. 1  and showing one knob enclosure and spring in an exploded view. 
         FIGS. 6 and 7  are perspective views of the bottom of the assembly shown in  FIG. 1  and showing the locking plate installed in the first embodiment of the assembly. 
         FIGS. 8A through 8C  are perspective views showing the steps in assembly of the brake lever knobs in accordance with the present invention. 
         FIG. 9  is a perspective view of the second embodiment of an air brake locking assembly that is constructed in accordance with the present invention. 
         FIG. 10  is a perspective view of the assembly shown in  FIG. 9  and illustrating a cross-sectioned view of the assembly structure. 
         FIG. 11  is an enlarged perspective view of a first knob enclosure constructed in accordance with the present invention. 
         FIG. 12  is an enlarged perspective view of a second knob enclosure constructed in accordance with the present invention. 
         FIG. 13  is a further enlarged and exploded perspective view of the assembly shown in  FIG. 1 . 
         FIG. 14  is a top perspective view of a second embodiment of an air brake lock assembly that is constructed in accordance with the present invention. 
         FIG. 15  is an exploded perspective view of the assembly shown in  FIG. 14 . 
         FIG. 16  is a bottom perspective view of a portion of the assembly shown in  FIG. 14 . 
         FIG. 17  is a top perspective view of a third embodiment of an air brake lock assembly that is constructed in accordance with the present invention. 
         FIG. 18  is an exploded perspective view of the assembly shown in  FIG. 17 . 
         FIG. 19  is an enlarged partial cross-sectioned view of a portion of the assembly shown in  FIG. 17 . 
         FIG. 20  is a bottom perspective view of a portion of the assembly shown in  FIG. 17 . 
         FIG. 21  is a top perspective view of a fourth embodiment of an air brake lock assembly that is constructed in accordance with the present invention. 
         FIG. 22  is an exploded perspective view of the assembly shown in  FIG. 21 . 
         FIGS. 23A and 23B  are enlarged partial cross-sectioned views of portions of the assembly shown in  FIG. 21 . 
         FIG. 24  is another enlarged partial cross-sectioned view of a portion of the assembly shown in  FIG. 21 . 
         FIG. 25  is a side elevational view of the assembly shown in  FIG. 21 . 
         FIG. 26  is a top perspective view of the assembly shown in  FIG. 21  and illustrating an installation shim used with the assembly. 
         FIG. 27  is top perspective view of a fifth embodiment of an air brake lock assembly that is constructed in accordance with the present invention. 
         FIG. 28  is a greatly enlarged view of one of the knob enclosures of the assembly shown in  FIG. 27 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings in detail,  FIG. 1  is a perspective view showing a portion of a first preferred embodiment of the air brake lock assembly, generally identified  10 , that is constructed in accordance with the present invention.  FIG. 13  is an exploded perspective view of the same assembly  10 . Unlike an air brake button housing of the type that is known in the art, the assembly  10  is composed of a knob enclosure  30 ,  40  for each knob  130 ,  140 , respectively, a lock subassembly  50  and a housing  20  that packages all of these components. Conventionally, there is provided a square knob enclosure  30  and an octagonal knob enclosure  40 , the respective knobs  130 ,  140  being associated with them. The square knob  130  is used to control the brakes of the semi-truck and is yellow in color whereas the octagonal knob (or “octo knob” as may be used herein) is red and is used to control the brakes of the semi-trailer. 
     The air brake lock assembly  10  is operated by turning a key  51  that is inserted into a lock cylinder  52  of the lock subassembly  50  to provide “locking” and “unlocking” action to the assembly  10 . The lock cylinder  52  has a disc shaped locking plate  54  mounted to a bottom or back side  53  of the cylinder  52 . See  FIGS. 2 and 6 . The locking plate  54  is bent in such a way that its cam-like outer edges  55  are inclined creating a helical profile. See also  FIG. 7 . The locking plate  54  is positioned in the housing  20  so the outer edges  55  of the plate  54  rest in slots  31 ,  41  that are located on the sides  32 ,  42  of the knob enclosures  30 ,  40 , respectively. See  FIG. 11 , for example. 
     When the lock cylinder  52  is turned 90° back and forth, the outer inclined edges  55  of the locking plate  54  push against the knob enclosures  30 ,  40 , thereby toggling the enclosures “in” and “out.” When the knob enclosures  30 ,  40  are toggled out, the air brake knobs  130 ,  140  are pushed “out” into the “lock” position. See  FIG. 2 . When the knob enclosures  30 ,  40  retract back “in,” the knobs  130 ,  140  can also be pushed back into the “unlocked” position. 
     As illustrated in  FIGS. 2 and 5 , the first embodiment of the assembly  10  is a spring loaded concept. That is, this first embodiment has springs  132 ,  142  that provide additional force to push the brake knobs  130 ,  140  outwardly. In this way, the load on the lock cylinder  52  is reduced, such as where a substantial amount of force is needed to move the air brake levers (not shown) outwardly. As shown, the springs  132 ,  142  and knob enclosures  30 ,  40  are placed into two corresponding sockets  23 ,  24  of the housing  20 . See also  FIG. 3 . 
     As shown in  FIGS. 6 and 7 , the housing  20  is then flipped upside-down in order to install the locking plate  54  to the lock cylinder  52 . The locking plate  54  drops into the middle of the housing  20  and is then turned to engage the plate edges  55  with the corresponding slots  31 ,  41  on the knob enclosures  30 ,  40 . The locking plate  54  is then secured with a machine screw or other fastener  58  which threads into the back of the lock cylinder  52 . The installed locking plate  54  retains the knob enclosures  30 ,  40  and springs  132 ,  142 , respectively, in the housing  20 . It should also be noted in  FIG. 7  that each of the sockets  23 ,  24  includes an inwardly curved portion  25 ,  26 , respectively, the curved portions  25 ,  26  further comprising openings  27 ,  28 . It is the openings  27 ,  28  that allow a portion of the knob enclosures  30 ,  40  to be exposed such that the outer edges  55  of locking plate  54  can engage them. 
     As illustrated in  FIGS. 8A through 8C , the knobs  130 ,  140  of the brake levers are unscrewed from each respective shaft  131 ,  141 . With the lock assembly  10  in the unlocked position, the housing  20  slides over lever shafts  131 ,  141 , and the knobs  130 ,  140  are screwed back down. When the lock cylinder  52  is returned to the locked position, the knob enclosures  30 ,  40  advance up and around the respective knobs  130 ,  140 , preventing them from turning and becoming unscrewed. 
     Where the force needed to push the levers out is small enough, additional springs may not be needed to reduce the load on the lock cylinder  52 . In this case, which is a second embodiment of the assembly, generally identified  110 , the springs can simply be eliminated, which will result in the entire package being slightly more compact. See  FIGS. 9 and 10 . The tooling should also be a little less complex in this second embodiment, as locating features for the springs are eliminated from other components. The remainder of the assembly procedure for the “spring-less” design is exactly the same as it is in the spring loaded concept of the first embodiment. The only difference is that the spring installation step is omitted. 
     Lastly, there are several options for molding the knob enclosures  30 ,  40 . For example, one enclosure  140  design that is shown in  FIG. 11  requires slightly more complex and expensive tooling that uses shutoffs to create the undercut slot  41  on the side  42 , but doesn&#39;t require any secondary operations. Another enclosure  44  design requires much less complex tooling without any shutoffs. This design, however, does require an additional secondary operation to cut the slot  45  in the side  47  after the part is molded. 
     Referring now to  FIGS. 14 to 16 , a third preferred embodiment of the air brake lock assembly, generally identified  210 , that is constructed in accordance with the present invention is illustrated. Specifically referring to  FIG. 16 , it will be seen that the assembly  210  comprises a “sliding lock plate” configuration. This embodiment is similar to the prior embodiments in that the assembly  210  includes a housing  220 , a square knob enclosure  230 , an octo knob enclosure  240  and a lock cylinder  250 . Referring now to  FIG. 15 , it will be seen that the lock cylinder  250  includes a central portion that can be used to secure the lock cylinder  250  to the housing  220  using a lock cylinder nut  251  that is disposed to the inner side of the housing  220 . The lock cylinder  250  also comprises a bottom portion, or “tail,”  252  that is shaped to engage an aperture  262  defined within a cam plate  260 . The cam plate  260  is secured to the tail  252  of the lock cylinder  250  using a lock cylinder screw  255  and a lock washer  257 , or other suitable fastening means. 
     The assembly  210  further comprises a bottom plate  270  which effectively “captures” two locking plates  280  within the housing  220 . The bottom plate  270  is affixed to the housing  220  by use of fasteners, such as screws  271 . The bottom plate  270  has a central aperture  272  that is flanked to each side with opposing side apertures  274 . The side apertures  274  are profiled to match the shaft profiles of the knob enclosures  230 ,  240  such that the shafts  232 ,  242  of the knobs  230 ,  240  can pass through them. Disposed between the bottom plate  270  and the housing  220  are the locking plates  280 , each plate  280  has somewhat of an H-shape to it and is identically configured to the other. 
     Referring now to  FIG. 15 , it illustrates the parts whereby the locking plates  280  are captured within the housing  220 . As shown, the cam plate  260  is mounted to the tail  252  of the lock cylinder  250 . The cam plate  260  has cam-like outer edges  264  that functionally cooperate with apertures  282  disposed at a first side  284  of each locking plate  280 . Each locking plate  280  further comprises an opposing second side  286  that similarly comprises an aperture  288  defined in it. In application, the cam plate  260  slides the two locking plates  280  back and forth from an unlocked position to a locked position. With that action, the second side  286  of each locking plate  280  slides under a knob enclosure  230 ,  240  to prevent the knobs (not shown) from being pushed downward. 
     Referring now to  FIGS. 17 to 20 , a fourth preferred embodiment of the air brake lock assembly, generally  310 , that is constructed in accordance with the present invention is illustrated. The assembly  310  of the fourth preferred embodiment comprises an adjustable height arrangement. This embodiment likewise has a housing  320 , which comprises a housing subassembly  322  having an upper housing  324  and a lower housing  326 . The assembly  310  also comprises a square knob enclosure  330 , an octo knob enclosure  340 , a lock cylinder  350  and a lock cylinder insert  356 . Referring now to  FIG. 18 , it will be seen that the lock cylinder  350  is inserted into the circular aperture  355  of the cylinder insert  356 , the cylinder insert  356  fitting within an aperture (not shown) of the housing  310  and extending into the housing  310 . As with the prior embodiment, the lock cylinder  350  comprises a tail  352  the end of which is engaged with a locking cam  360 . The locking cam  360  is flanked by two locking plates  380 , all of which is held in place by a spacer block  370 . Lower plates  390  are disposed below the spacer block  370  but within the lower housing  326 . 
     In this configuration, the housing subassembly  322  consists of the upper and lower housings  324 ,  326 , respectively, which can “telescope” in and out from each other to allow for an adjustable height of the housing  320 . Set screws  321  located in each of the four corners of the housing subassembly  322  ensure that the housing height can be adjusted and remain secure in a set position. See  FIG. 19 . The sliding locking plates  380  conceal the set screws  321  when the assembly  310  is in the “locked” position. This ensures the assembly  310  cannot be adjusted to a lower position such that the knobs (not shown) and the air brake security assembly  310  can be removed. 
     Referring now to  FIG. 20 , it shows that the locking cam  360  was modified from a sheet metal plate to a cast or molded cam to provide better contact with the locking plates  380 . Functionally, the locking cam  360  and the locking plates  380  operate substantially the same as the prior assembly  210  operated, the locking cam  360  having cam-like outer edges  364  that functionally cooperate with apertures  382  disposed at a first side  384  of each locking plate  380 . 
     Referring now to  FIGS. 21 to 26 , a fifth preferred embodiment of the air brake lock assembly, generally  410 , that is constructed in accordance with the present invention is illustrated. The assembly  410  of the fifth preferred embodiment comprises a contoured lower housing arrangement. Specifically, this embodiment also has a housing  420 , which comprises a housing subassembly  422  having an upper housing  424  and a lower housing  426 . The assembly  410  also comprises a square knob enclosure  430 , an octo knob enclosure  440 , a lock cylinder  450  and a lock cylinder insert  456 . Referring now to  FIG. 22 , it will be seen that the lock cylinder  450  is inserted into the circular aperture  455  of the cylinder insert  456 , the cylinder insert  456  fitting within an aperture (not shown) of the housing  420  and extending into the housing  420 . As with the prior embodiment, the lock cylinder  450  comprises a tail  452  the end of which is engaged with a locking cam  460 . The locking cam  460  has the same two locking plates  480  to either side of it, all of which is held in place by a spacer block  470 . These plates  480  function in the same way that their previously-discussed counterparts  280 ,  380  function relative to the assemblies  210 ,  310 , respectively. Lower plates  490  are disposed below the spacer block  470  but within the lower housing  426 . 
     In this modified configuration, the housing subassembly  422  consists of the upper and lower housings  424 ,  426 , respectively, and housing springs  428  to hold the lower housing  426  tightly against adjustment set screws  421  to prevent the housing  410  from vibrating and moving around. Specifically, the housing springs  428  push the upper housing  424  upwardly against the set screws  421  whereas the adjustment screws  421  push the lower housing  426  downwardly to increase the overall height of the assembly  410 . See  FIGS. 23A and 23B . 
     Further in this embodiment, and as is shown in  FIG. 24 , knob enclosure springs  432 ,  442  were added in the housing subassembly  422  to ensure that the enclosures remain seated tightly against the air brake knobs  430 ,  440 . That is, the knob enclosure springs  432 ,  442  push the knob enclosures  430 ,  440  upward against the air brake knobs (not shown). It should also be noted that the contour of the lower housing  426  was modified to fit both older and newer Freightliner® truck dashes (FREIGHTLINER is a registered mark of Daimler Trucks North America LLC). See  FIG. 25 . As shown in  FIG. 26 , an installation shim  400  is used to ensure that the locking plates  480  are not “pinched” to the point of binding when the housing  410  is adjusted tightly between the knobs and the dash (also not shown). 
     Referring lastly to  FIGS. 27 and 28 , a sixth preferred embodiment of the air brake lock assembly, generally  510 , that is constructed in accordance with the present invention is illustrated. The assembly  510  of the sixth preferred embodiment comprises a modified knob enclosure arrangement. Specifically, a lip  533 ,  543  was added to the outer perimeter  532 ,  542  of the knob enclosures  530 ,  540 , respectively, to provide more material for the operator to grip the knobs (not shown). Snap features (also not shown) were also added to secure the knobs in the knob enclosures  530 ,  540 . 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details disclosed and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept.

Summary:
An air brake lock assembly helps to prevent air brake actuation knobs from being actuated. The air brake lock in accordance with the present invention is a theft-prevention device that mounts over the air brake knobs on the dash of a semi-truck cab. It is installed between the dash and the knobs and, when locked, the assembly prevents the knobs from being pushed in. If the air brake knobs cannot be pushed back in, the air brake will remain locked and the truck and trailer will remain immobile. In one embodiment of the present invention, the assembly includes a base and an enclosure for each brake knob. An air brake lock is disposed between the knobs such that the knobs can be selectively locked and unlocked. In one embodiment, the assembly is spring-loaded. In another embodiment, the assembly is not spring-loaded.