Abstract:
A lockout device couplable between a pneumatically-operable vehicle parking brake and a plunger-actuated control valve. The plunger is movable between a brake-disengaging position in which pressurized air flows through the control valve to the parking brake, and a brake-engaging position in which such air flow is prevented. The device has a shaft which is rotatable with respect to the plunger. The shaft has recessed and non-recessed portions. The plunger has a second recess. A key is removably couplable to the shaft and is rotatable between an engaged position in which the shaft&#39;s non-recessed portion protrudes into the second recess while the plunger is in the brake-engaging position, preventing movement of the plunger into the brake-disengaging position; and, a disengaged position in which the recessed portion of the shaft intersects the second recess, permitting movement of the plunger between the brake-disengaging and engaging positions.

Description:
TECHNICAL FIELD  
         [0001]    This invention pertains to a key-actuated parking brake engagement/disengagement control for air brake equipped vehicles.  
         BACKGROUND  
         [0002]    Air brake equipped vehicles such as trucks and buses normally utilize spring-type parking brakes. Air pressure is applied to disengage a spring mechanism in order to disengage the parking brakes. When the air pressure is relieved, the spring mechanism engages the parking brakes, which remain engaged until the air pressure is reapplied. A control valve allows the vehicle driver to exhaust air from the parking brake pneumatic circuit to engage the parking brakes; and, to repressurize the circuit in order to disengage the parking brakes.  
           [0003]    There have been instances in which drivers have forgotten to actuate the parking brake control valve before leaving the vehicle. If the control valve is not properly actuated, the parking brakes are not engaged. There have been “roll away” incidents in which driverless buses have caused serious injuries while rolling away from a parked position, due to driver failure to operate the control valve so as to engage the parking brakes.  
           [0004]    Although most trucks are equipped with a key-operated ignition switch, this is not universally true of buses. Many buses have an ignition switch which can be operated without a key. This invention provides a key-operated device which controls the vehicle parking brake (pneumatic) circuit to reduce the potential for vehicle “roll away” due to driver failure to engage the parking brakes.  
         SUMMARY OF INVENTION  
         [0005]    The invention provides a vehicle brake lockout device for coupling between a pneumatically-operable vehicle parking brake and a pneumatic control valve. The control valve has a plunger which the vehicle driver can move between a brake-disengaging position in which pressurized air flows from a pressurized air supply through the control valve to the parking brake, and a brake-engaging position in which such air flow is prevented. In one embodiment, the device incorporates a shaft which can be rotated with respect to the plunger. The shaft has recessed and non-recessed portions. The plunger has a second recess. A key can be removably coupled to the shaft and rotated between engaged and disengaged positions. If the plunger is in the brake-engaging position then the key can be moved into the key&#39;s engaged position. This causes the non-recessed portion of the shaft to protrude into the plunger&#39;s recess, preventing movement of the plunger into the brake-disengaging position. In the key&#39;s disengaged position, the recessed portion of the shaft intersects the plunger&#39;s recess, permitting movement of the plunger between the brake-disengaging and engaging positions.  
           [0006]    An optional switch can be coupled to the shaft such that the switch has a first electrical conductivity state when the key is in its engaged position and a second electrical conductivity state when the key is in its disengaged position. These switch states can be used for any desired purpose, such as controlling the vehicle&#39;s ignition circuit. A second recessed portion on the shaft can be positioned adjacent the switch such that the switch is actuated into its first electrical conductivity state when the shaft&#39;s second recessed portion is rotated into contact with the switch; with the switch being actuated into its second electrical conductivity state when the shaft&#39;s second recessed portion is rotated away from contact with the switch.  
           [0007]    An optional solenoid can be electrically connected to the vehicle&#39;s ignition circuit. The solenoid has one operating state when the ignition circuit is energized and a second operating state when the ignition circuit is de-energized. The solenoid has a plug which is projected into or withdrawn from the plunger&#39;s recess, depending on the solenoid&#39;s operating state.  
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]    [0008]FIG. 1 is an oblique pictorial illustration of a vehicle parking brake lockout device in accordance with the invention, shown in the “parking brake disengaged” position.  
         [0009]    [0009]FIG. 2 is a top plan view of the FIG. 1 apparatus, excluding the plunger, shown in the “parking brake engaged” position.  
         [0010]    [0010]FIG. 3 is a partially sectioned side elevation view of the FIG. 1 apparatus, shown in the parking brake engaged position.  
         [0011]    [0011]FIG. 4 is a fluidic/pneumatic circuit diagram schematically depicting the FIG. 1 apparatus and also schematically depicting an alternative embodiment of the invention.  
         [0012]    [0012]FIG. 5 is a partially sectioned side elevation view of an alternative embodiment of the invention, shown in the parking brake disengaged position.  
         [0013]    [0013]FIG. 5A is an end elevation and sectional view of the key shaft and sliding valve portions of the FIG. 5 apparatus.  
         [0014]    [0014]FIG. 6 depicts the FIG. 5 apparatus in the parking brake engaged position.  
         [0015]    [0015]FIG. 6A is an end elevation and sectional view of the key shaft and sliding valve portions of the FIG. 6 apparatus.  
         [0016]    [0016]FIG. 7 is a partially sectioned side elevation view of a further alternative, solenoid-actuated embodiment of the invention. 
     
    
     DESCRIPTION  
       [0017]    Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.  
         [0018]    FIGS.  1 - 3  depict a first embodiment of the invention, namely ignition/brake lockout device  10 . Body member  12  is mounted on vehicle control panel  14  (FIG. 3) in a location convenient for driver access. Control knob  16  is fixed on the upper end of plunger  18 , which is slidably mounted in aperture  20  (FIG. 2) in body member  12 . Parking brake control valve  22  (FIG. 3) is mounted on the underside of vehicle control panel  14 , beneath body member  12 .  
         [0019]    Control valve  22  is equipped with an actuating rod  24  which projects upwardly from control valve  22 , through aperture  26  in vehicle control panel  14  and is coupled to the lower end of plunger  18  (for example, by means of suitable threaded fittings respectively provided on plunger  18  and actuating rod  24 ).  
         [0020]    Control valve  22  has an inlet port  26  which receives pressurized air from supply tank  28  and/or emergency air tank  30 . Control valve  22  also has an exhaust outlet port  32  and a parking brake actuation port  34 . The outlet ports of a conventional quick release valve  36  are respectively coupled to the air inlet ports of parking brakes  38 ,  40  via pressurized air lines  42 ,  44  respectively. Quick release valve  36 &#39;s inlet port is coupled to control valve  22 &#39;s parking brake actuation port  34  via pressurized air line  46 . Quick release valve  36  also has an exhaust port, as indicated by dashed line arrow  48 . The vehicle&#39;s service (i.e. primary) brakes  50 ,  52  are schematically illustrated in FIG. 4, but need not be further described. Solid line indicia  54 ,  56  respectively indicate disengagement of parking brakes  38 ,  40 ; whereas dashed line indicia  58 ,  60  respectively indicate engagement of parking brakes  38 ,  40 .  
         [0021]    The aforementioned components and indicia bearing drawing reference numerals  14 - 60  are conventional components of prior art air brake vehicle parking brake systems. Before describing the invention, the operation of a such prior art systems will first be explained with reference to FIGS. 3 and 4 and the aforementioned prior art components bearing drawing reference numerals  14 - 60  inclusive.  
         [0022]    Parking brakes  38 ,  40  are disengaged by pulling knob  16  upwardly into the dashed line position indicated in FIG. 3. Knob  16  draws plunger  18  upwardly through aperture  20 , simultaneously drawing control valve  22 &#39;s actuating rod  24  upwardly through aperture  26  in vehicle control panel  14 . Such upward movement of rod  24  actuates control valve  22  such that pressurized air which flows from supply tank  28  and/or emergency air tank  30  to inlet port  26  is routed to parking brake actuation port  34  and thence through line  46  to quick release valve  36 . Quick release valve  36  delivers pressurized air from line  46  to lines  42 ,  44  respectively, pressurizing parking brakes  38 ,  40  so as to release their integral spring mechanisms (not shown) and thereby disengage the parking brakes.  
         [0023]    Parking brakes  38 ,  40  are engaged by depressing control knob  16  into the solid outline position shown in FIG. 3, as indicated by arrow  62  in FIGS. 3 and 4 respectively. This forces plunger  18  downwardly through aperture  20  in body member  12 , and forces control valve  22 &#39;s actuating rod  24  downwardly through aperture  26  in vehicle control panel  14 . Such downward movement of rod  24  actuates control valve  22  such that pressurized air which flows from supply tank  28  and/or emergency air tank  30  to inlet port  26  is unable to pass through control valve  22 . Instead, pressurized air is exhausted from line  46  via control valve  22 &#39;s exhaust outlet port  32 . The resultant drop in air pressure within line  46  activates quick release valve  36 , which allows air to be exhausted from parking brakes  38 ,  40  through lines  42 ,  44  as indicated by arrow  48 . This in turn allows the spring mechanisms incorporated in parking brakes  38 ,  40  to deploy so as to engage parking brakes  38 ,  40  respectively.  
         [0024]    Ignition/brake lockout device  10  is now described with further reference to FIGS.  1 - 4 . Lock tumbler  64  is mounted within body member  12  in a location convenient for driver insertion of key  66 . One end of shaft  68  is fixed to the inward end of lock tumbler  64  for rotation by operation of key  66 , as hereinafter explained. A first recess or detent  70  is provided in shaft  68 . An optional second recess or detent  72  may be provided at another convenient location on shaft  68  (as illustrated, but not necessarily, the end of shaft  68  opposite the end thereof which is affixed to lock tumbler  64 ). A circumferential groove  74  (FIG. 3) is also provided in plunger  18 .  
         [0025]    Key  66  can be rotated between the disengaged position shown in FIG. 1 and the engaged position shown in FIGS. 2 and 3. When key  66  is in the disengaged position (FIG. 1) shaft  68  is rotated such that first recess  70  intersects aperture  20  so as to permit vertical movement of plunger  18  through aperture  20  to engage or disengage parking brakes  38 ,  40  as previously explained. When key  66  is in the engaged position (FIGS. 2 and 3) shaft  68  is rotated such that the non-recessed portion of shaft  68  protrudes into aperture  20 . Such protrusion is possible only if plunger  18  is positioned to locate groove  74  immediately adjacent the non-recessed portion of shaft  68 , as seen in FIG. 3. Such positioning of plunger  18  and location of groove  74  occurs only when knob  16  is depressed; which, as previously explained, is the position in which parking brakes  38 ,  40  are engaged.  
         [0026]    It can thus be seen that parking brakes  38 ,  40  can be engaged only if key  66  is rotated into the engaged position (FIGS. 2 and 3). This is an improvement in comparison to unkeyed prior art systems because it is less likely that a driver would leave the vehicle with key  66  in place on the vehicle&#39;s control panel  14 . To remove key  66 , the driver must rotate key  66  into the “engaged” position. However, key  66  can be rotated into the engaged position only if knob  16  and plunger  18  are depressed. Since such depression engages parking brakes  38 ,  40  it is apparent that device  10  reduces the potential for “roll away” of a driverless vehicle.  
         [0027]    The likelihood that a driver will leave the vehicle with key  66  in place on the vehicle&#39;s control panel  14  can be further reduced if key  66  is required by the driver for some additional purpose. For example, some transit operators provide locked washrooms for the drivers use. If key  66  is required to open a locked washroom door then it is more likely that a driver will remove key  66  before leaving the vehicle, thereby engaging parking brakes  38 ,  40  as aforesaid.  
         [0028]    Device  10  can optionally be electrically connected to the vehicle&#39;s ignition circuit (not shown), or to the vehicle&#39;s electrical accessory circuit (not shown), etc. to further reduce the likelihood that a driver would leave a vehicle with key  66  in place on the vehicle&#39;s control panel  14 . For example, if key  66  must be removed to shut off the vehicle&#39;s engine, then it is more likely that a driver will remove key  66  before leaving the vehicle (thereby engaging parking brakes  38 ,  40  as aforesaid) to shut off the engine in order to avoid leaving the vehicle unattended with the engine running. This can be achieved by positioning shaft  68 &#39;s optional second recess  72  for rotation relative to optional micro-switch  76  (FIG. 2) and electrically connecting micro-switch  76  to the vehicle&#39;s ignition circuit (not shown). When key  66  is in the disengaged position shown in FIG. 1 (i.e. when parking brakes  38 ,  40  are disengaged) the non-recessed portion of shaft  68  adjacent second recess  72  is rotated to depress micro-switch  76 &#39;s lever  78 , thereby turning micro-switch  76  “on”. This “on” signal can be used in any desired manner. For example, if micro-switch  76  is electrically connected into the vehicle&#39;s ignition circuit, then this “on” signal can be used to complete the vehicle&#39;s ignition circuit such that the vehicle&#39;s engine can be started. When key  66  is in the engaged position (FIGS. 2 and 3; i.e. when parking brakes  38 ,  40  are engaged) second recess  72  is rotated into the position shown in FIG. 2, whereupon a spring (not shown) within micro-switch  76  returns lever  78  to its disengaged position, thereby turning micro-switch  76  “off”. If micro-switch  76  is electrically coupled into the vehicle&#39;s ignition circuit as aforesaid, then this “off” signal can be used to deactivate the vehicle&#39;s ignition circuit and prevent the engine from starting. This is an improvement in comparison to prior art systems lacking an ignition key because it is less likely that a driver would leave a vehicle with the engine running. The driver can only switch the vehicle&#39;s engine off by rotating key  66  into the disengaged position. However, key  66  can be rotated into the disengaged position only if knob  16  and plunger  18  are depressed. Since such depression engages parking brakes  38 ,  40  it is apparent that device  10  reduces the potential for “roll away” of a driverless vehicle.  
         [0029]    [0029]FIGS. 5 and 6 depict an alternate embodiment of the invention, namely ignition/brake lockout device  80  which is also schematically illustrated in dashed outline in FIG. 4. Either one but not both of ignition/brake lockout devices  10 ,  80  are utilized in a single vehicle. If device  80  is utilized, then the aforementioned prior art components bearing drawing reference numerals  14 - 60  inclusive are also utilized. Device  80  can for example be used in situations where it is desired to retain an existing parking brake mechanism incorporating the aforementioned prior art components bearing drawing reference numerals  14 - 60 .  
         [0030]    Ignition/brake lockout device  80  incorporates body member  82  which is mounted beneath vehicle control panel  14  in a convenient location for driver actuation of key  84  so as to control pressurized air passage between inlet port  86  and outlet port  88  and thus control delivery of pressurized air from supply tank  28  and/or emergency air tank  30  through pressurized air line  46  to quick release valve  36 . An aperture  90  is provided in body member  82 , between ports  86 ,  88 . Shuttle valve member  92  is provided in aperture  90  for slidable displacement there-along as hereinafter explained. Spring  94  biases valve member  92  toward inlet port  86 , as shown in FIG. 6. Lock tumbler  96  is mounted in body member  82  to receive key  84 . Shaft  98  is fixed to the inward end of lock tumbler  96  for rotation by operation of key  84 , as hereafter explained. A recess  100  is provided in shaft  98  and a circumferential groove  102  is provided around a central portion of valve member  92 .  
         [0031]    In operation of ignition/brake lockout device  80 , knob  16  must be depressed to allow key  84  to be rotated between the disengaged position shown in FIGS. 5 and 5A, and the engaged position shown in FIGS. 6 and 6A. When key  84  is in the disengaged position, shaft  98  is rotated so that recess  100  faces aperture  90  with no portion of shaft  98  obstructing aperture  90 , thereby permitting slidable displacement of valve member  92  along aperture  90 . If knob  16  is raised, pressurized air flows from supply tank  28  and/or emergency air tank  30  through control valve  22  as previously explained to parking brake actuation port  34 , and air is delivered via line  46  to device  80 &#39;s inlet port  86 , as indicated by arrow  104 . Pressurized air entering inlet port  86  forces valve member  92  toward outlet port  88 , overcoming the biasing force of spring  94  such that cylindrically apertured portion  106  of valve member  92  is positioned over nozzle  108  which protrudes from outlet port  88  into aperture  90 . Pressurized air entering inlet port  86  is thus able to flow through aperture  90 , through valve member  92 &#39;s inlet orifice  110  into bore  111  and thence into cylindrical aperture  106 , as indicated by arrow  112 .  
         [0032]    Orifice  110  is sized to allow sufficient pressure to build up behind valve member  92  (i.e. to the right of valve member  92 , as viewed in FIG. 5) to overcome the biasing force of spring  94 , as aforesaid. O-ring  114  provides releasable sealing engagement between valve member  92  and nozzle  108 , such that pressurized air entering cylindrical aperture  106  is contained and flows through nozzle  108  and through outlet port  88  into pressurized line  46  and thence to quick release valve  36 , thereby disengaging parking brakes  38 ,  40  as previously explained. Sweep seal  109  prevents air leakage between the outer surface of valve member  92  and the inner surface of aperture  90 .  
         [0033]    When key  84  is in the engaged position shown in FIG. 6, shaft  98  is rotated such that its non-recessed portion protrudes into and obstructs aperture  90 , as seen in FIGS. 6 and 6A. Such protrusion is possible only if valve member  92  is positioned within aperture  90  to position groove  102  immediately adjacent shaft  98  as seen in FIG. 6. Such positioning is possible only if pressurized air is not being delivered from control valve  22  to device  80 &#39;s inlet port  86  such that spring  94  is able to bias valve member  92  into the position shown in FIG. 6, in which air is exhausted from aperture  106  through exhaust orifice  105 , as indicated by arrow  103 . However, spring  94  can bias valve member  92  into the position shown in FIG. 6 only if knob  16  is depressed to force actuating rod  24  downwardly to block passage of pressurized air through control valve  22  and engage parking brakes  38 ,  40 .  
         [0034]    Exhaust orifice  105  is sized so that it is sufficiently large to prevent excessive pressure build up within aperture  90  if knob  16  is pulled upwardly after key  84  is removed from device  80 , and sufficiently small to permit adequate pressure to build up behind valve member  92  (i.e. to the right of valve member  92 , as viewed in FIG. 5) to overcome the biasing force of spring  94 , as aforesaid.  
         [0035]    It can thus be seen that parking brakes  38 ,  40  can be engaged only if key  84  is rotated into the engaged position (FIGS. 6 and 6A). This is an improvement in comparison to unkeyed prior art systems because it is less likely that a driver would leave the vehicle with key  84  in place on the vehicle&#39;s control panel  14 . To remove key  84 , the driver must rotate key  84  into the “engaged” position. However, key  84  can be rotated into the engaged position only if knob  16  and plunger  18  are depressed. Since such depression engages parking brakes  38 ,  40  it is apparent that device  80  reduces the potential for “roll away” of a driverless vehicle.  
         [0036]    Device  80  can be optionally be electrically connected to the vehicle&#39;s ignition circuit (not shown), or to the vehicle&#39;s electrical accessory circuit (not shown), etc. to further reduce the likelihood that a driver would leave a vehicle with key  84  in place on the vehicle&#39;s control panel  14 . This can be achieved as previously described for device  10 , by providing a second recess (not shown) in shaft  98  for rotation relative to a micro-switch (not shown) and electrically connecting the micro-switch to the vehicle&#39;s ignition circuit. FIG. 7 depicts a further alternative embodiment incorporating solenoid  116  which can be coupled to plunger  18  and further electrically coupled to the vehicle&#39;s ignition circuit. This is achieved by mounting solenoid  116  on body member  12  such that solenoid  116 &#39;s slidable plug  118  can be biased by spring  120  into plunger  18 &#39;s circumferential groove  74  when knob  16  is depressed as illustrated in FIG. 7. More particularly, when the vehicle&#39;s ignition is “off”, solenoid  116  is de-energized, allowing spring  120  to bias plug  118  into groove  74 . When the vehicle&#39;s ignition is “on”, solenoid  116  is energized and withdraws plug  118  from groove  74 , overcoming the biasing force of spring  120 , allowing knob  16  to be raised into the dashed outline position shown in FIG. 7 so as to disengage parking brakes  38 ,  40 .  
         [0037]    As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. For example, if plunger  18  is non-rotatable then instead of providing a circumferential groove  74  in plunger  18  one need only recess the portion of plunger  18  adjacent the portion of shaft  68  bearing first recess  70 . Similarly, if valve  92  is non-rotatable then instead of providing a circumferential groove  102  in valve  92 , one need only recess the portion of valve  92  adjacent the portion of shaft  98  bearing recess  100 . Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.