Abstract:
A mixing drum gate for a concrete transport vehicle is described. The gate includes a pivotally mounted plate that abuts the lower portion of the rim of the drum mouth and is biased against it so as to maintain the abutment during rotation, shifting and flexing of the drum. The gate may include a pneumatically controlled opening mechanism that pivots the plate between an open, closed and intermediate positions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of provisional application Ser. No. 60/348,596, dated Jan. 15, 2002. 

   TECHNICAL FIELD 
   The present invention relates generally to concrete mixing vehicles and apparatus to be used therewith. More particularly, the invention relates to apparatus used to reduce the incidence of inadvertent discharge of material from the mixing drum of a concrete mixing vehicle. 
   BACKGROUND 
   Generally, a concrete transport vehicle has a mixer unit that includes a rotatable mixing drum in which concrete can be mixed and transported. Concrete is usually loaded and unloaded through the drum mouth, which is angled upwards along an inclined axis. The typical concrete truck also includes a hopper for feeding concrete into the drum and a chute for channeling concrete out of the drum. The hopper and chute are normally aligned adjacent the mouth of the drum with the chute positioned below the hopper. As the concrete transport vehicle moves, the mixer unit tends to flex and shift. When combined with the constant rotation of the drum, this flexing and shifting provides for rather irregular positioning of the drum mouth. When the mixer unit contains concrete, it is not uncommon for some concrete material to be inadvertently discharged from the drum mouth, especially when the concrete truck is moving especially up hill. Consequently, concrete may fall from the mixing unit onto roadways and construction sites, resulting in a loss of valuable concrete as well as the potential for a safety hazard or at least a nuisance. Even in light of the potential consequences of inadvertent discharge, little past progress has been made to reduce effectively the likelihood of such discharge due to the irregularity of the movement of the mixing drum. Consequently, there is a need for an apparatus that helps to reduce the occurrence of inadvertent discharge of concrete material from the drum mouth of a mixing unit, as well as a concrete transport vehicle that incorporates the principles of such a device. 
   SUMMARY 
   An apparatus for reducing the likelihood of an inadvertent discharge of concrete material from the drum mouth of a concrete mixing unit is disclosed. The present invention encompasses a gate that, when closed, obstructs at least a portion of the drum mouth so as to reduce the chance that concrete material inadvertently falls from the mixing drum, even when the drum is rotating and the vehicle is moving. The gate generally includes a plate mounted adjacent to the mouth of the mixing drum and movable between an open position and a closed position. When the plate is in the closed position, it is biased against the rim of the mouth of the mixing drum by a biasing member and generally maintains contact with the rim even as the mixing drum rotates and the vehicle moves. 
   One embodiment includes a gate with a plate hingedly mounted on the concrete truck adjacent the mouth of the drum. The hinge may include one or more pivot pins connected to the plate and pivotally mounted to brackets. The brackets may include biasing members, such as springs, that bias the plate toward the mixing drum, so that the plate maintains closed contact with the rim of the mouth of the drum, even when the drum is rotating and/or the vehicle is moving. An opening mechanism may also be operably connected to the plate. The opening mechanism can adjustably reposition the plate between an open position, a closed position or some intermediate position therebetween. The opening mechanism may be designed to be operated from within the cab of the vehicle or by an operator standing next to the vehicle. 
   Another embodiment encompassing principles of the present invention includes a gate having a generally semi-circular plate with two pivot pins axially aligned and extending from the from the top portion of the plate. Each pin is pivotably connected to a bearing that is moveably mounted to a bracket. Each bracket includes an elongated track in which a shoe extending from the bearing is disposed. The shoe of each bearing cooperates with a spring disposed within the tract, whereby the spring biases the shoe, and, in turn, the bearing, pivot pin and plate toward the mixing drum, while also allowing these components to move with the mixing drum as it flexes. Each mounting bracket is secured on the mixing truck in a convenient location, such as, for example, on the hopper support mount. The opening mechanism may include a pneumatically-controlled cylinder connected to the gate by a moveable arm or piston. The arm or piston is connected to the plate and the cylinder is mounted to the outside of the hopper of the mixing vehicle. The pneumatic controls may be wired into the cab of the truck to the facilitate ease of operation of the gate. 
   In use, the gate may be adjustably positioned so that the plate contacts at least a lower portion of the rim of the mouth of the mixing drum or is otherwise disposed adjacent the drum mouth to prevent concrete materials from falling away from the drum. Even with the plate in contact with a portion of the drum mouth, the mixing drum can still be rotated in order to prevent setting of the concrete contained therein. Contact between the plate and rim of the drum mouth generally is maintained even as the drum rotates, flexes and shifts. This contact is maintained by the biasing force applied either directly or indirectly to the plate. The biasing force may be generated by springs located in the channels of the mounting brackets or other appropriate devices and arrangements. In this manner, the mouth of the mixing drum is at least partially obstructed so as to reduce the likelihood of inadvertent discharge of concrete materials from therein. As the concrete truck is operated, contact is maintained between the plate and the rim of the mouth until such time as it is desired to either charge or discharge the aggregate contained within the mixing drum. At such time, the gate may be adjustably opened. If the gate includes an opening mechanism, such as the above pneumatic arrangement, then the opening mechanism may be activated to adjustably move the gate to an open, closed or intermediate position. 
   Thus, a mixing drum gate is now provided that successfully addresses the problems and shortcomings of the prior art. The mixing drum gate allows concrete materials to be maintained inside the mixing drum of a concrete truck as the mixing drum is rotated and the truck is operated, while reducing the likelihood of inadvertent discharge of these materials. This mixing drum gate also may be repositioned easily to allow efficient and normal charging and discharging of the concrete materials from the mixing drum. These and other aspects of the mixing drum gate of this invention will become more apparent upon review of the detailed description set forth below when taken in conjunction with the accompanying drawings, which are briefly described as follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective rear view of a concrete mixing transport vehicle with a mixing drum gate that encompasses principles of the present invention and with portions of the vehicle shown in phantom line. 
       FIG. 2  is another perspective view of the vehicle with a mixing drum gate of  FIG. 1  with portions of the vehicle shown in phantom line. 
       FIG. 3  is a front view of a plate and pivot pins of a mixing drum gate encompassing principles of the present invention. 
       FIG. 4  is a front view of another embodiment of a plate and pivot pins of a mixing drum gate encompassing principles of the present invention. 
       FIG. 5  is a cross-sectional view of a bracket assembly of a mixing drum gate encompassing principles of the present invention. 
       FIG. 6  is a top view of another embodiment of a bracket assembly of a mixing drum gate encompassing principles of the present invention. 
       FIG. 7  is a perspective view of another embodiment of a mixing drum gate encompassing principles of the present invention. 
       FIG. 8  is a side view of the mixing drum gate of  FIG. 1  in a closed position and also in phantom line in an open position. 
   

   DETAILED DESCRIPTION 
   Referring now in more detail to the drawings,  FIGS. 1-8 , in which like numerals refer here appropriate to like parts throughout the several views,  FIG. 1  is a perspective view of the ear of a concrete transport vehicle or concrete truck  100 . The truck  100  is shown in phantom line so as to highlight the mixing drum gate  20 , which would otherwise be partially obstructed by the hopper/chute assembly mounted at the rear of the mixing drum  110 . The concrete truck  100  generally includes a mixing drum  110  with a mouth  12  formed therein, which is defined by a rim  114 . Adjacent to the mouth  112  of the mixing drum  110  is located a hopper  120 , which is used to charge the mixing drum  110  with concrete material from overhead. Also, adjacent the mouth  112  of the mixing drum  110  is a chute  130 , which generally is positioned below the hopper  10  and provides a conduit through which concrete material may be discharged from the mixing drum  110 . A hopper support brace  122  is attached to the concrete truck  100  and is aligned so as to support both the hopper  120  and the chute  130 . The mixing drum gate  20  is disposed adjacent the mouth  112  of the mixing drum  120 , and is shown in  FIG. 1  in a closed position. While this particular example has the drum mouth positioned at the rear of the vehicle the present invention applies equally to mixing units and vehicles that are forward or side loading. Since the size and orientation of drum mouths of concrete trucks vary from vehicle to vehicle, the mixing drum gate may vary in dimension and positioning to operate properly with a given vehicle. 
   In general terms, the embodiment of the mixing drum gate  20 , shown in  FIGS. 1 ,  2  and  8 , includes a plate  22  attached to pivot pins  26  that are pivotally connected to a bracket assembly  31  mounted on the concrete truck  100 . Each bracket assembly  31  biases the pivot pin  26  and the plate  22  toward the mixing drum  110  so that the plate  22  contacts the rim  114  of the mouth  112  of the drum  110 . The plate  22  is pivotally opened and closed by an opening mechanism including a pneumatically controlled cylinder  40  that is connected either to a pivot pin  26 , plate or other convenient connection to actuate the pivoting movement of the plate  22 . 
   In more particular terms, the mixing drum gate  20  includes a plate  22  formed of steel or another appropriate durable material. The plate  22  generally is shaped in a semi-circular form so as to cover the lower portion of the mouth  112  of the mixing drum  110 , although other appropriate shapes for obstructing the mouth of the mixing drum are contemplated by the present invention. The plate  22  is pivotally mounted so that it may swing back and forth from an open position to a closed position. Along its topside, the plate  22  includes shoulders  29  that extend radially from a notch  41 . The notch  41  is generally semi-circular and is provided to allow clearance of the lower portion of the hopper  120  as the plate  22  is opened and closed. The plate also has lips  27  extending from the outer face  25  of the plate  22 . As shown in  FIG. 2 , the lip extends beyond the top edge of the plate  22  and is attached, such as by welding, to a pivot pin  26 . 
   The pivot pins  26  are connected to the lips  27  by welding or other appropriate connection. Each pivot pin  26  is slightly offset from the topside of the plate  22  by approximately the width of the lip  27 . The lip  27  may be formed of a metal bar or other appropriate structure to form generally about a 90 degree angle with the plate  22 . The pivot pins  26  generally extend radially from the top center of the plate  22  and are axially aligned with each other. Each pivot pin  26  is journaled within a bearing  28  that is axially aligned with the pin  26 . The cooperation between each bearing  28  and each pivot pin  36  connected thereto allows the plate  22  to be pivotally adjusted between open, closed and intermediate positions. As shown in  FIG. 8 , plate  22  may be pivotally adjusted downward to a closed position and upward to an open position. 
   Each bearing  28  forms a portion of a bracket assembly  31 , which, in one embodiment includes a bearing  28 , bearing shoe  30 , bracket  32 , bracket channel  34 , and spring  36 . More particularly, the bearing  28  includes an opening axially aligned with the pivot pin  26 . Bearing  28  is attached to a bearing shoe  30 , which is disposed in the channel  34  of bracket  32 . Bearing shoe  30  may be formed of keystock or another suitably rugged material. Channel  34  is an elongated opening within bracket  32  in which the bearing shoe  30  may move. A dust shield  37  may be placed over the channel in order to reduce clogging. Bracket  32  may be approximately one inch by twelve inches and formed of a metal such as steel, or other suitable material. A spring  36  also is disposed in channel  34  and acts upon bearing shoe  30 . The bearing  28  and bearing shoe  30  combination is biased by spring  36  toward the general direction of the mixing drum  110 . The bracket assembly  31  may be mounted to the hopper support brace  122  or other appropriate structure of the concrete truck  100 , so that plate  22  may be adjusted to a close position adjacent the rim  114  of mouth  112 . 
   A bib  23  may be attached to the inner face  21  of the plate  22 , as shown in  FIGS. 3 and 4 . The bib  23  may be formed of an ultra high molecular weight plastic or other suitable material that will tend to provide sealing properties to the bib  23 . The plastic material used to form bib  23  may be approximately 0.5 inches in thickness. The bib  23  contacts the rim  114  of the mouth  112  of the drum  110  so as to provide an improved contact or seal between the plate  22  and the rim  114 . 
   An opening mechanism may also be operably connected to plate  22  so as to allow for the repositioning thereof. As shown in the figures, the opening mechanism may include a pneumatically controlled cylinder  40  having a movable piston  42  therein. In one embodiment, as shown in  FIG. 7 , the piston  42  is connected to the pivot pin  26  by an arm  44 . In another embodiment, shown in  FIGS. 2 and 8 , the piston  42  may be connected to the outer face  25  of plate  22  by an eyelet  47  and clevis pin or by an arm connecting the eyelet  47  to the piston  42 . The eyelet  47  may be connected to the lower center portion of outer face  25  in order to facilitate the movement of plate  22 . As shown in  FIGS. 1 and 2 , the cylinder  40  can be mounted to the hopper  120 , in the case where it cooperates directly with plate  22  by connection with the outer face  25 . Alternatively, as shown in  FIG. 7 , cylinder  40  can be mounted to the hopper support brace  122  when it cooperates with pivot pin  26  by the connection thereto by arm  44 . These and other configurations of the cylinder placement are contemplated. 
   The cylinder  40  can be operated by a slide valve mounted in the cab of the truck  100  that is connected to the cylinder by line  48 . A pressure switch is also provided that cooperates with the pneumatic cylinder system to indicate when gate  20  is open. The cylinder  40  also will be operably connected to an air regulator mounted on the closed side of cylinder  40 . Speed valves may be mounted on the exhaust ports of slide valve. Emergency tees are also provided to operate the gate  20  manually in case the primary opening mechanism fails. 
   As shown in  FIG. 4 , another embodiment of the drum gate  220  of the present invention includes a plate  222  with pivot pins  226  and a plastic bib  223  attached thereto. The lower profile of the plate  222  is generally semicircular and includes a generally semicircular notch  241 , as in the previous embodiment, but, unlike the previous embodiment, the shoulders  229  are sloped inwardly and down. These inwardly sloping shoulders  229  provide further clearance for concrete that is discharging from the mixing drum. The pivot pins  226  can be angled also so as to provide greater clearance when the gate  220  is open. This embodiment otherwise functions generally in the same manner as the embodiment of the plate shown in FIG.  3 . 
   In use, concrete material is charged to the mixing drum  112  through the hopper  120 , or other appropriate fashion. In the closed position, mixing drum gate  20  contacts the mixing drum  110 . More specifically, in one embodiment, the plate  22  of the mixing drum gate  20  contacts or abuts the rim  114  of the mouth of the mixing drum  110 . Even as the drum  110  rotates, the plate  22  contacts the rim  114 . If a bib  23  is mounted on the inner surface  21  of plate  22  of the gate  20 , then the bib  23  contacts and/or forms a seal with rim  114 . This contact is sufficient to keep nearly all concrete material contained within the drum  110  from leaking between the rim  114  and the plate  22 . The plate  22  obstructs the lower portion of the mouth  112 , where concrete material is most likely to be spilling out of the mouth  112 . As the concrete truck  100  and/or the mixing drum  10  moves and rotates, the drum  110  flexes and shifts, in addition to its rotation. As this movement occurs, the contact between the plate  20  and/or bib  23  and the rim  114  is maintained by the plate  22  being biased toward the mixing drum  10  and the rim  114 . The biasing force is indirectly applied to the plate  22  by the spring  36 , or other biasing means used with the gate  20 , acting on the bearing shoe  30  located in the bracket channel  34  and connected to bearing  28 . The bearing  28 , in turn, biases the pivot pin  26  that is connected to plate  22  by lip  27 . Thus, in this manner the gate  20  maintains the contact with the rim  114  and keeps concrete material from discharging from the mouth  112  of the drum  110 . 
   Once the mixing drum  110  is ready to be discharged, the gate  20  can be opened. The operator can activate the slide valve located in the truck cab, thereby causing the cylinder piston  42  to retract and cause the plate  22  to pivot about the axis extending through the pivot pins  26  so as to move the lower portion of the plate  22  up and away from the rim  114 . The concrete material contained within the mixing drum may then be discharged in the normal fashion. To close the gate  20 , the slide valve can be reactivated to cause the cylinder piston  42  to extend and the plate  22  to pivot down. 
   It is to be understood that the above embodiments are provided by way of example only and are not to be construed so as to limit the present invention only to those aspects of the illustrated embodiments. The present invention encompasses modifications and alterations made to the disclosed embodiments by those of ordinary skill in the art.