Abstract:
Apparatus and methods for locking a discharge chute of a mixing vehicle are disclosed. The locking apparatus can be mounted to existing discharge chutes and frame arrangements and may utilize existing pneumatic systems of the mixing vehicle. The locking apparatus generally include a base having a first arm and a second arm pivotally secured to the base. An airbag may be positioned between the first arm and the second arm to bias a clamping region of the locking apparatus in a locked or a released state depending on the configuration of the locking apparatus.

Description:
BACKGROUND OF THE INVENTION 
   1. Summary of the Invention 
   The present invention relates to discharge chutes on mixing vehicles and, more particularly, to apparatus and methods securing a discharge chute at a desired position about its range of motion. 
   2. Description of the Related Art 
   Vehicles designed to mix and transport concrete typically include mixing drums in which the liquid concrete is held during transportation. The mixing drums normally have a capacity of between seven and ten cubic yards of concrete. This volume of concrete typically weighs between 28,000 lbs and 40,000 lbs. The mixing drums typically rotate on the mixing vehicle to agitate the mass of liquid concrete and to prevent it from setting during transport. 
   The mixing drums are typically set at an angle on the mixing vehicle which places the discharge opening of the mixing drum above the level of a full load of concrete. When the concrete is to be discharged, rotation of the drum is typically reversed which directs the liquid concrete outwardly through a discharge opening. This discharge opening is typically positioned at the front or rear of the vehicle. The discharged concrete is received and guided to the desired location by a pivoting discharge chute. The discharge chute is typically mounted below the discharge opening. The discharge chute is typically configured to pivotally rotate about a vertical axis on the vehicle. Accordingly, the chute may direct concrete to either side or to the front/rear of the mixing vehicle depending upon the particular configuration of the vehicle. Extensions of the chute may be employed to direct concrete to locations more remote from the vehicle. 
   At 4,000 pounds per cubic yard, the liquid concrete can produce substantial forces as it is directed by and moves along the discharge chute. When disposed along a long extension, the dynamic mass of concrete can produce significant torque at the connection of the discharge chute to the vehicle. Given the pivoting nature of a typical discharge chute, the forces on the discharge chute can produce movement which is difficult to manually control and may result in unwanted movement of the discharge chute. This movement of the discharge chute can result in the misdirection of the liquid concrete which wastes both the concrete and the man-hours needed for cleanup. In addition, a freely swinging chute can present a significant safety hazard for those working around the discharge chute. Accordingly, various devices and alternative configurations have been employed for controlling and/or locking discharge chutes in a desired position. 
   Some prior devices for securing the position of a chute include manual operable clamp assemblies mounted to a pivoted chute brace. These clamp assemblies typically consist of a threaded shaft at one end of an upright brace bearing shaft. A wheel is typically threadably engaged to a shaft and can be selectively tightened against the shaft journal to clamp a brace tightly to a vehicle  100  frame. This brace-type brake is partially serviceable for standard length chutes. However, the locking mechanism can vibrate loose and allow the chute to pivot freely. 
   U.S. Pat. No. 3,279,766 to F. V. Mendoza discloses a transit concrete mixer with particular reference to a brake mechanism. The mechanism disclosed enables selective angular positioning of a concrete chute. The brake components used are of typical automotive drum brake design with axially oriented shoes and brake surfaces. A hydraulic brake cylinder is utilized for actuation of the brake shoes selectively bringing them radially against a brake drum. 
   The problem of braking a discharge chute at the pivotal mount for the discharge chute is also recognized to a limited degree in the U.S. Patent to Hansen et al, U.S. Pat. No. 3,334,872. Hansen et al discloses a double ended piston hydraulic cylinder that controls pivotal movement of a discharge chute at the chute&#39;s mounting point on the concrete mixing truck. The cylinder operates to pivot the discharge chute about its axis and also acts as a positive brake. 
   The hydraulic cylinder requires use of an expensive and complex hydraulic system that is not typically supplied as standard equipment on concrete mixing trucks. Hydraulic cylinders wear quickly when exposed to concrete with its naturally abrasive component. Maintenance and repair therefore become frequent. Furthermore, use of a hydraulic cylinder could be considered “overkill”, since the primary need is not for powered movement of the chute. The discharge chute is usually empty when moved from one position to another. The primary need is for holding the discharge chute stationary after being angularly positioned, when it is full of heavy concrete. 
   U.S. Pat. No. 3,410,538 to M. L. Potter discloses a positive locking apparatus for positioning a discharge chute at any of several pre-selected angular positions. Potter&#39;s arrangement uses a positive detent type lock between the chute frame and a pressure plate pivoted with the chute. A pin is used to interconnect the stationary frame with the pivoted pressure plate by insertion within one of several angularly spaced apertures provided in the movable pressure plate. 
   The Potter device and other known “detent” type chute locking mechanisms do allow positive positioning of the discharge chute at the pivot point between the discharge chute and stationary frame but do not enable infinite angular adjustment for precise pouring. Further, such mechanisms will not effectively operate to stop a moving discharge chute without causing possible damage to the lockout mechanism. Difficulty is also experienced in removing and placing the lock pin when the discharge chute is loaded. 
   SUMMARY OF THE INVENTION 
   This Summary capsulizes some of the claimed aspects of the present invention. 
   Additional details of aspects of the present invention and/or additional embodiments of the present invention are found in the Detailed Description of the Invention. Further, an Abstract of the specification&#39;s technical disclosure is included for purposes of complying with 37 C.F.R. 1.72. The Abstract is not intended for use in interpreting the scope of the claims. 
   The present invention includes a locking that can be mounted to existing chute and frame arrangements and that makes use of the existing pneumatic systems typically available for air brakes or air suspension on the mixing vehicle. The locking apparatus can be controlled to stop the chute at any selected angular position and hold it securely in place until actuated or deactuated depending upon the particular configuration of the apparatus. An apparatus for securing a discharge chute of a mixing vehicle can include a base, a first arm, a second arm, and an airbag. The base is generally configured to be mounted to the mixing vehicle. The first arm can define a first clamping portion and a first air bag receiving portion. The first clamping portion is generally configured to contact a first side of a pressure plate. The first arm can be pivotally secured to the base between the first clamping portion and the first airbag receiving portion. The second arm can define a second clamping portion and a second airbag receiving portion. The second clamping portion is generally configured to contact a second side of a pressure plate. The second arm can also be pivotally secured to the base between the first clamping portion and the second clamping portion. The airbag is generally secured at a first end of the airbag to the first airbag receiving portion of the first arm and secured at a second end of the airbag to the second airbag receiving portion of the second arm. The airbag is generally configured to bias the first airbag receiving portion of the first arm and the second airbag receiving portion of the second arm apart upon inflation. The locking apparatus may further include a resilient member secured between the first arm and the second arm proximate to the first airbag receiving portion and the second airbag receiving portion. The resilient member may function to bias the first clamping portion against a first surface of a pressure plate and the second clamping portion against a second surface of the pressure plate. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  illustrates an end view of an exemplary embodiment of the present invention secured to the rear end of a concrete mixing vehicle; 
       FIG. 2  illustrates a partial side view of another exemplary embodiment of the present invention secured to a concrete mixing vehicle; 
       FIG. 3  illustrates a partial side view of another exemplary embodiment of the present invention secured to a concrete mixing vehicle; 
       FIG. 4  illustrates a side view of an exemplary embodiment of the present invention; 
       FIG. 5  illustrates a top view of an exemplary embodiment of the present invention similar to the embodiment illustrated in  FIG. 4 ; 
       FIG. 6  illustrates an exploded perspective view of an exemplary embodiment of the present invention similar to the embodiment illustrated in  FIG. 4 ; 
       FIG. 7  illustrates a side view of another exemplary embodiment of the present invention; 
       FIG. 8  illustrates a side view of another exemplary embodiment of the present invention; 
       FIG. 9  illustrates a top view of an exemplary embodiment of the present invention similar to the embodiment illustrated in  FIG. 8 ; and 
       FIG. 10  illustrates an exploded perspective view of an exemplary embodiment of the present invention similar to the embodiment illustrated in  FIG. 7 . 
   

   All Figures are illustrated for ease of explanation of the basic teachings of the present invention only; the extensions of the Figures with respect to number, position, relationship and dimensions of the parts to form the preferred embodiment will be explained or will be within the skill of the art after the following description has been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following description has been read and understood. 
   Where used in various Figures of the drawings, the same numerals designate the same or similar parts. Furthermore, if used in the description without further elaboration, the terms “top,” “bottom,” “right,” “left,” “forward,” “rear,” “first,” “second,” “inside,” “outside,” and similar terms should be understood to reference only the structure shown in the drawings as it would appear to a person viewing the drawings and utilized only to facilitate describing the illustrated embodiment. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention is intended for use on mixing vehicles  100 . These vehicles  100  are frequently configured and utilized for mixing concrete. For exemplary purposes and ease of description, the following description describes the invention in association with a concrete mixing truck as the vehicle  100 . Vehicles  100  typically include a mixing drum  110  rotatably mounted to the vehicle  100 . The drum  110  includes a discharge opening. The discharge opening typically faces frontward or rearward with respect to the front and rear of the vehicle  100 . A hopper  112  is typically positioned adjacent to the discharge opening. A discharge chute  114  is typically positioned below the hopper  112  for receiving the concrete discharged from the discharge opening. The discharge chute  114  is typically mounted to the vehicle  100  to pivot about a vertical axis. The discharge chute  114  is also typically extendable to one or more elongated positions. Accordingly, the discharge chute  114  may direct concrete to a desired position remote from drum  110 . 
     FIGS. 1 and 2  illustrate a couple of exemplary configurations for vehicles  100  and locking apparatus  10  in which the present inventions may be utilized. As illustrated, vehicle  100  is a rear discharge transit mixer. The vehicle  100  is depicted discharging concrete to one side of the vehicle  100  using a chute  114  having a semicircular configuration. The semicircular shape of discharge chute  114  in part permits the discharge chute  114  to contain and guide the concrete as it is directed to a target location. The vehicle  100  is supported by wheels  116  connected by an axle assembly  118  mounted to the frame of the vehicle  100  through an air suspension system  120 . In addition, vehicles  100  may also include air braking systems. 
   A locking apparatus  10  in accordance with the present invention is secured to the rear of vehicle  100 , for exemplary purposes. The locking apparatus  10  is selectively operable to lock the discharge chute  114  at a selected angular position about the vertical axis  200 . Vertical axis  200  is generally defined relative to vehicle  100  and is used for descriptive purposes only. Locking apparatus  10  is generally configured to grip pressure plate  12  which is connected to discharge chute  114 . The pressure plate  12  and discharge chute  114  are connected such that the pressure plate  12  rotates with the discharge chute  114  as the discharge chute is pivoted about its vertical axis of rotation. In certain embodiments, pressure plate  12  may also be rotatably secured to the vehicle  100 . In operation, when locking apparatus  10  is secured to pressure plate  12 , the discharge chute  114  is secured in a position for rotation around the vertical axis  200 . When locking apparatus  10  is released from the pressure plate, the discharge chute  114  may be rotated around the vertical axis  200 . As generally illustrated for exemplary purposes, pressure plate  12  and discharge chute  114  are configured to rotate in planes substantially perpendicular to vertical axis  200 . 
   The connection of pressure plate  12  and discharge chute  114  may be direct or remote. In some remote variations, pressure plate  12  may be connected to discharge chute  114  by arms, pressure plates, shafts, gears or otherwise as will be recognized by those skilled in the art. Thus, in certain embodiments, pressure plate  12  may be configured to rotate in a plane distinct from that of the discharge chute  114 .  FIG. 1  illustrates a pressure plate  12  remotely secured to discharge chute  114  by an arm  14  for exemplary purposes.  FIG. 2  illustrates a pressure plate  12  secured directly to a discharge chute  114 . Locking apparatus  10  may be connected to air suspension system  120  and/or air brake system to receive compressed air to lock or unlock locking apparatus  10  from pressure plate  12 . 
     FIG. 2  illustrates a partial view of another embodiment vehicle  100 . As illustrated, pressure plate  12  is secured directly to discharge chute  114 . As illustrated, the discharge chute  114  rotatably secured to vehicle  100  by a ring bearing  122  for exemplary purposes. The illustrated pressure plate  12  is oriented on the discharge chute  114  such that the discharge chute  114  and the pressure plate  12  rotate about the same vertical axis  200 . In one aspect, the discharge chute  114  may be secured to an arm or platform  124  secured to the vehicle  100 . The discharge chute  114  is positioned below the hopper  112 . As illustrated, locking apparatus  10  is secured to the arm/platform  124  to position portions of the locking apparatus  10  operably about pressure plate  12 . 
     FIG. 3  illustrates a more detailed partial view of an embodiment of the present invention similar to that illustrated in  FIG. 1  secured to a vehicle  100 . As illustrated, discharge chute  114  includes an arm  14  connecting discharge chute  114  to pressure plate  12 . Pressure plate  12  is rotatably secured to a platform  124 . Locking apparatus  10  is also secured to platform  124  and is positioned adjacent to substantially planar rim  20  of pressure plate  12 . Rim  20  includes an arcuate edge  22 . For exemplary purposes, the entire pressure plate  12  has been illustrated as planar. However, those skilled in the art will recognize that only a rim  20  of the pressure plate can be planar to facilitate interaction with certain embodiments of locking apparatus  10 . As illustrated, locking apparatus  10  includes a first arm  24  and a second arm  26  pivotally connected to a base  28 . In certain embodiments, the shape of arcuate edge  22  of pressure plate  12  permits a portion of the rim  20  of pressure plate  12  to remain positioned between first arm  24  and second arm  26  of locking apparatus  10  for the full range of motion of discharge chute  114  about the vertical axis  200 . In other embodiments, the shape of arcuate edge  22  of pressure plate  12  permits a portion of the rim  20  of pressure plate  12  to remain positioned between first arm  24  and second arm  26  of locking apparatus  10  for the partial range of motion of discharge chute  114  about the vertical axis  200 . In one aspect, the arcuate edge  22  may define a portion of a circle. The center of the circle may be positioned at the point of rotation of plate  12  about the vertical axis  200 . Apparatus  10  further includes an airbag  30  positioned between first arm  24  and second arm  26 . Depending on the particular configuration of locking apparatus  10 , the inflation of airbag  30  may either release or secure locking apparatus  10  to the pressure plate  12 . For inflation, airbag  30  is in communication with a source of compressed air. In one aspect, an air hose  132  in communication with a source of compressed air may communicate the compressed air from its source to the airbag  30 . The source of compressed air may be a compressor, an air tank, or other source for compressed air as will be recognized by those skilled in the art. As mentioned above, one exemplary source of compressed air may the communicated from the air brake or air suspension systems  120  of the vehicle  100 . A system of controllable valves may also be provided to permit the inflation and deflation of the airbag by an operator dependent and/or independent of the function of the source of compressed air. 
     FIGS. 4 to 10  illustrate embodiments of locking apparatus  10  in accordance with the present invention. These embodiments of locking apparatus  10  generally include a base  28 , a first arm  24 , a second arm  26 , and an airbag  30 . The embodiments of  FIGS. 4 to 6  further include a resilient member  34 . The locking apparatus  10  is generally configured to exert a gripping force to a rim  20  of pressure plate  12  between the clamping portions  74 ,  76  of the first arm  24  and the second arm  26  to securely hold the pressure plate  12  in a desired position. As illustrated in  FIGS. 4 to 6 , apparatus  10  releases from pressure plate  12  when the airbag  30  is pressurized sufficiently to overcome the locking force exerted by resilient member  34 . As illustrated in  FIGS. 7 to 10 , apparatus  10  grips the pressure plate  12  when the airbag  30  is pressurized. 
   Base  28  is configured to secure locking apparatus  10  to vehicle  100  and to withstand the forces typically conferred upon locking apparatus  10  to maintain the position of discharge chute  114  during operation of mixing vehicle  100 . As illustrated for exemplary purposes, base  28  may define a flat lower surface  29  to be received on a surface of a vehicle  100  or may be otherwise configured as will be understood by those skilled in the art upon review of the present disclosure. To secure locking apparatus  10  to vehicle  100 , base  28  may define mounting holes  44  for mounting the base  28  to vehicle  100 . Base  28  may be particularly configured to pivotally secure first arm  24  and second arm  26 . Typically, first arm  24  and second arm  26  will movably attached to base  28  to pivot about one or more axes. As illustrated, first arm  24  and second arm  26  are secured to base  28  by a shaft  36 . Base  28  may define a first passage  46  and a second passage  48  concentrically positioned about the intended axis of rotation the first arm  24  and second arm  26 . Shaft  36  may extend through first passage  46  and second passage  48  defined by base  28  to pivotally secure the first arm  24  and the second arm  26  to base  28 . The first passage  46  may be defined on a first extension  56  and second passage  48  may be defined on a second extension  58  extending from base  28 . In one aspect, first extension  56  and second extension  58  may function to position the first arm  24  and the second arm  26  relative to arcuate edge  22  of pressure plate  12 . First extension  56  and second extension  58  may define an intermediate cavity  60  between the extensions  56 ,  58  to receive portions of first arm  24  and second arm  26 . First extension  56  and second extension  58  may be secured to or integral with base  28 . In other aspects, distinct pivot points may be provided for both the first arm  24  and second arm  26  in accordance with the present invention by having a first shaft to which the first arm  24  is mounted and a second shaft to which the second arm  26  is mounted. Those skilled in the art will recognize additional configurations for pivotally mounting first arm  24  and second arm  26  upon review of the present disclosure that are intended to remain within the scope of the present invention. As illustrated, shaft  36  is configured as a bolt for exemplary purposes. Alternatively, the shaft  36  may be integrally formed as part of one of the arms  24 ,  26  or extensions  56 ,  58  or may take any number of other forms as will be recognized by those skilled in the art upon review of the present disclosure. The head  33  of the illustrated shaft  36  may abut an outer surface  57  of first extension  56  and the nut  37  may abut a surface  59  of second extension  58  to secure the bolt in the first passage and the second passage between the first extension  56  and second extension  58 . Upon review of the present disclosure, those skilled in the art will recognize other pivoting linkages that may be utilized to secure the first arm  24  and second arm  26  to base  28  which do not depart from the scope of the present invention. 
   First arm  24  and second arm  26  are elongated members having a first end and a second end. The first ends and the second ends are positioned at opposite ends of the first arm  24  and the second arm  26 . The first ends include a first clamping portion  74  and a second clamping portion  76  on the first arm  24  and second arm  26 , respectively, for engaging the pressure plate  12 . The second ends include a first airbag receiving portion  84  and a second airbag receiving portion  86  on the first arm  24  and second arm  26 , respectively. Each of the first airbag receiving portion  84  and second airbag receiving portion  86  are configured to engage airbag  30  to increase the distance between first airbag receiving portion  84  and second airbag receiving portion  86  upon inflation of airbag  30 . The first arm  24  and the second arm  26  are pivotally secured to base  28 . As illustrated, first arm  24  includes a first mounting passage  64  configured to receive a shaft  36  and second arm  26  includes a second mounting passage  66  to receive a shaft  36 . When shaft  36  is secured to base  28  as illustrated in  FIGS. 4 and 10 , first arm  24  and second arm  26  having received the shaft  36  through the first mounting passage  64  and second mounting passage  66  may also be pivotally secured to base  28 . Any number of washers or spacers  43  may be positioned over shaft  36  as is dictated by the particular configurations of various components. The first mounting passage  64  and the second mounting passage  66  are positioned between the respective clamping portions  74 ,  76  and airbag receiving portions  84 ,  86  of first arm  24  and second arm  26 . The first clamping portion  74  and the second clamping portion  76  may include a first pad  94  and a second pad  96 , respectively. In one aspect, the first pad  94  and the second pad  96  may be designed to optimize the friction generated by contact between the first clamping portion  74  and the second clamping portion  76  and the pressure plate  12  and, accordingly, represent friction pads. Pads  94 ,  95  may be secured to their respective gripping regions  74 ,  76  by screws  95  or may be otherwise secured to their respective gripping regions  74 ,  76 . In another aspect, the first pad  94  and the second pad  96  may be designed to reduce wear and tear on their respective clamping portions and, accordingly, represent wear pads. In yet another aspect, the first pad  94  and the second pad  96  may be designed to dampen vibration or movement of the pressure plate  12  and, accordingly, represent damping pads. The pads  94 ,  96  may be formed from a variety of rubbers, synthetic polymers, metals and other materials and combinations of materials that will be recognized by those skilled in the art. The second arm  24  may include a brace  97  which may be received within a brace cavity  99  to further stabilize at least the second arm  26  when subject to forces conferred from securing discharge chute  114 . Brace  97  will typically be secured to the vehicle  100  directly or to the base  28 . 
   Airbag  30  defines an expansion chamber  32  and includes a first end  40  and a second end  50 . Airbag  30  may be made as a unitary inflatable sack or may be made in a variety of configurations such as the exemplary plates  31 , mounting rings  33 , and membrane  39  illustrated in  FIG. 8 . Airbag  30  is secured between the first airbag receiving portion  84  of the first arm  24  and the second airbag receiving portion  86  of the second arm  26 . As illustrated, airbag  30  may be secured to the first airbag receiving portion  84  and the second airbag receiving portion  86  by bolts  41 . Bolts  41  may include lock washers  45  to further secure bolts  41  to arms  24 ,  26  and/or airbag  30 . As will be understood in the art, airbag  30  may be configured to otherwise be mechanically secured to airbag receiving portions  84 ,  86 , may be adhesively secured, or may be otherwise secured to the airbag receiving portions  84 ,  86 . An air port  38  is in fluid communication with the expansion chamber  32  defined by the airbag  30 . The air port  38  may be integral with an arm  24 ,  26  or may be a independent component secured to an arm  24 ,  26  or directly to airbag  30 . The air port  38  may communicate with the air chamber  32  through an air passage  88  defined in one of arms  24 ,  26 . A gasket  42  may be provided between the opening to air passage  88  and the airbag  30 . The air port  38  functions to at least allow the introduction of air into the expansion chamber  32  from a source of compressed air. Typically, the air port  38  is in fluid communication with an air hose  132  to communicate air from the source of compressed air to the expansion chamber  32 . In one aspect, the airbag  30  is generally configured to increase the distance and/or produce an expanding force between the first end  40  and second end  50  of the airbag  30  upon addition of air into the expansion chamber  32 . A pressure relief valve  78  may also be fluid communication with expansion chamber  32 . Pressure relief valve  78  may be provided to allow a user to release pressure from the expansion chamber  32  and/or may provide for release of pressure when the pressure within the expansion chamber  32  exceeds a set threshold. 
   The embodiments of  FIGS. 4 to 6  include portions of the first arm  24  and second arm  26  that cross within an intersection point or region  92  between the respective clamping portions and airbag receiving portions. In the exemplary illustrated embodiments, intersection  92  is generally positioned at or about the pivot point for the arms  24 ,  26  for exemplary purposes. In other words ascribing upper and lower terminology relative to the base  28  for descriptive purposes, the first arm  24  includes the first upper airbag receiving portion  84  and the first lower clamping portion  74  and the second arm  26  includes the second lower airbag receiving portion  86  the second upper clamping portion  76 . In operation, the distance between the first clamping portion  74  and the second clamping portion  76  increases as the distance between the first mounting portion  84  and second mounting portion  86  increases. To secure the pressure plate  12  between the first clamping portion  74  and the second clamping portion  76 , the resilient member  34  is provided between the first arm  24  and the second arm  26 . The resilient member  34  biases the first clamping portion  74  toward the second clamping portion  76 . The resilient member  34  may be provided on the same side of the pivot point as the first airbag receiving portion  84  and the second airbag receiving portion  86 . Typically, the resilient member  34  will be provided at a sufficient distance from the pivot point to permit the resilient member  34  to exert sufficient force to lock pressure plate  12  and associated discharge chute  114  at a desired position. In this embodiment, inflation of airbag  30  releases the clamping force between the first clamping portion  74  and the second clamping portion  76  as the compressive force of the resilient member  34  is overcome. 
   As illustrated in  FIGS. 4 to 6  for exemplary purposes, resilient member  34  includes a spring  52  disposed over a spring shaft  54  slidably passing through a shaft passage  53  in second arm  26 . A first end of the spring shaft  54  is secured to the second end of the first arm  24 . As illustrated, the first end of the spring shaft  54  is pivotally secured to the second end of second arm  26 . For exemplary purposes, spring shaft  54  is secured by an eyelet shaft  63  secured to second arm  26  and positioned through an eyelet  61  an end of spring shaft  54 . The eyelet shaft  63  may be positioned within a retention lumen  67  defined by the end of second arm  26 . Further, the eyelet  61  may be secured within a retention cavity  65  also defined by the end of second arm  26  and intersecting with retention lumen  67 . The second end of the spring shaft  54  includes a detent  62  configured to retain the spring  52  on the spring shaft  54 . The detent  62  is illustrated for exemplary purposed as a circular stop  72  secured over the end of spring shaft  54  by a threaded cap  70  secured to the end of the spring shaft  54 . The spring  52  is positioned between an upper surface of the second arm  26  and the detent  62 . As illustrated, the spring  52  is biased between the upper surface of the second arm  26  within a spring cavity  53  defined in the top surface of first arm  24 . As such, the first clamping portion  74  of the first arm  24  and the second clamping portion  76  of the second arm  26  are biased toward one another as the spring  52  tends to force the first airbag receiving portion  84  of the first arm  24  toward and second airbag receiving portion  86  of the second arm  26 . In such a configuration, the spring  52  is typically selected to have a spring constant sufficient to maintain the pressure plate  12  in a desired position during operation of vehicle  100 . In other embodiments, the resilient member may be an elastic material, springs or other resilient material operatively connected between the locking apparatus  10  to bias the first airbag receiving portion  84  toward the second airbag receiving portion  86 . To release the first clamping portion  74  and second clamping portion  76  from the pressure plate  12 , compressed air is provided into the expansion chamber  32  through air port  38 . The pressure within the expansion chamber  32  is increased at least until the clamping force exerted by the spring  52  is sufficiently overcome to permit the desired freedom of movement of the discharge chute  114 . 
   The embodiments of first arm  24  and second arm  26  illustrated in  FIGS. 7 to 10  do not cross as do the embodiments of  FIGS. 4 and 6 . In other words, again ascribing upper and lower terminology relative to the base  28  for descriptive purposes, the first arm  24  includes the first upper airbag receiving portion  84  and the first upper clamping portion  74  and the second arm  26  includes the second lower airbag receiving portion  86  the second lower clamping portion  76 . In operation of this embodiment, the distance between the first clamping portion  74  and the second clamping portion  76  decreases as the distance between the first mounting portion  84  and second mounting portion  86  increases. Accordingly, inflation of airbag  30  provides the clamping force between the first clamping portion  74  and the second clamping portion  76 . To release the first clamping portion  74  and second clamping portions  76  from the pressure plate  12 , compressed air may be released from the expansion chamber  32 . Typically, the air is released through pressure relief valve  78  or through air port  38 . The pressure within the expansion chamber  32  is decreased at least until the clamping force exerted by the airbag  30  is sufficiently reduced to permit the desired freedom of movement of the discharge chute  114 . 
   Although illustrated and described herein with reference to certain specific embodiments, the present invention is nevertheless not intended to be limited to the details provided in the foregoing description. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention. These modifications may become apparent to those skilled in the art upon review of the present disclosure.