Patent Publication Number: US-7896538-B2

Title: Power system for a small load concrete truck drum

Description:
TECHNICAL FIELD 
     This invention relates generally to power systems for turning concrete truck drums, and more specifically concerns an engine-driven power system for use with small-load concrete truck drums. 
     BACKGROUND OF THE INVENTION 
     Large concrete delivery trucks with rotating (spinning) drums which can accommodate 9-11 yards or even more of concrete are well known. In operation, it is important that the drum be kept spinning, regardless of whether the truck is moving or at a standstill. This maintains the concrete within the drum in a desired mix state. 
     In order to accomplish this, power for the spinning drum on the large concrete trucks is taken from the engine flywheel. In this arrangement, the drum continues to spin as long as the engine is running. 
     Small-load concrete trucks, e.g. those trucks having a 2-5 cubic yard capacity, also have used flywheel take-off systems to provide power for spinning of the drum. However, this arrangement has some disadvantages for smaller or medium-sized commercial trucks which are not specifically manufactured to carry concrete drums. Hence, it is desirable for a concrete truck with a small load drum to have a power system which does not use the engine flywheel and which spins the concrete drum as long as the engine is running. 
     DISCLOSURE OF THE INVENTION 
     Accordingly, the present embodiment is a power system for turning a drum on a concrete mixer truck, comprising: a power take-off unit connected to a power take off gear in a transmission for the concrete mixer truck, wherein the power take-off gear is driven by the engine, so that it is always operating, driving the power take-off unit, when the engine is running, regardless of whether the transmission is engage or not; a hydraulic pump powered by the power take-off unit; and hydraulic lines connecting the pump to a fluid reservoir and to a drive system for a mixing drum on the truck, wherein the mixing drum is capable of receiving a load of concrete in the range of only two to five cubic yards, wherein the mixing drum continues to turn as long as the engine of the truck is running. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of a concrete mixer truck with a power system embodiment operating off the transmission of the truck. 
         FIG. 2  shows in more detail the embodiment of  FIG. 1 . 
         FIG. 3  shows a top view of a pump portion of the power system of  FIG. 1  and associated equipment. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
       FIG. 1  shows a small or light load concrete mixer truck  10 . Concrete truck  10  includes a truck body with a cab  11 , and a mixer drum  12  capable of carrying small concrete loads, i.e. two to five cubic yards of concrete. The truck is medium duty, such as 18,000-34,000 GVW or equivalent. Various trucks, even standard light duty trucks can, however, be used. Mixer drum  12  is maintained in a spinning mode by a planetary drive assembly  14 , which is conventional and thus not shown in detail. In the embodiment shown, the transmission  16  ( FIG. 2 ) of the truck has a PTO (power take off) drive gear. The PTO drive gear is engine driven and provides direct engine power at a PTO port located at the side of the transmission. The PTO drive gear operates when the truck is moving or stopped. A commercially available example of such a transmission is an Allison Model 3000 or 3500 RDS. 
     Referring to  FIG. 2 , connected to the transmission PTO port is a PTO unit  20 . The PTO unit  20  is also conventional, such as from Chelsea or similar manufacturer. The Chelsea PTO provides full-time power, operating off of the engine through the transmission, i.e. as long as the engine is running, PTO unit  20  is capable of supplying power. Extending from PTO unit  20  is a mechanical drive line  22 , which in the embodiment shown extends to a hydraulic pump  24 . Hydraulic pump  24  is a variable displacement axial piston pump, also available commercially. The pump can either be a closed circuit or an open circuit pump. A suitable pump is available from Bondioli and Pavesi or similar manufacturer. Associated with the pump is a 12V actuator  26  and an oil filter  28  ( FIG. 3 ). The pump  28  is mounted on a bracket which in turn is mounted to the frame  29  of the truck. 
     Two hydraulic lines  30  and  32  extend between the pump  24  and the planetary drive  14 , for controlling the planetary drive  14 . This is a conventional arrangement for concrete mixer trucks. Fluid can flow in both directions through lines  30  and  32 , so that drum  12  can be turned in both rotational directions. Conventional controls  31  on the pump permit an operator to control the direction of the fluid and hence the direction of the spinning of the drum. 
     Two additional hydraulic lines  34  and  36  extend between pump  24  and a fluid reservoir  38 , one line carrying fluid from the pump to the reservoir and the other carrying fluid from the reservoir back to the pump. 
     In operation, mixer drum  12  will be continuously turning in one direction or the other as long as the engine of the truck is running. The mixer drum will continue to turn even through the truck may be stopped. This has the advantage of maintaining the concrete in a proper mix state. At a construction site, a discharge assembly  44 , mounted to the rear of the truck  10 , directs concrete exiting from drum  12  down a chute portion of the discharge assembly to the desired location for the concrete. 
     While the embodiment shown includes a connecting drive line between the PTO  20  and the pump  24 , the pump can alternatively be mounted directly to the output port of the PTO. 
     The system shown and described herein is advantageous, since it provides a constantly turning drum capability for a concrete truck carrying small loads, i.e. two to five cubic yards, without requiring an engine flywheel take off assembly. Hence, a conventional medium or even light truck can be used, with a proper transmission, to carry a small/light size concrete drum. 
     Although a preferred embodiment of the invention has been disclosed for purposes of illustration, it should be understood that various changes, modifications and substitutions may be incorporated in the embodiment without departing from the spirit of the invention which is defined by the claims which follow.