Abstract:
A self-purging auxiliary fluid supply system for supplying washout or makeup water or other fluids under pressure to a truck-mounted concrete mixing/dispensing drum is disclosed. The system includes a truck-mounted fluid reservoir for containing a quantity of fluid connected to supply fluid to an air-operated diaphragm pump connected to supply auxiliary fluid from the fluid reservoir under pressure to a discharge assembly. The pump further provides an integral purge system for displacing fluid in the fluid supply system after use.

Description:
BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to vehicle-mounted concrete mixing and dispensing systems and, more particularly, to on-board auxiliary fluid supply systems employed to supply water for washout or adding water to a concrete mix. Specifically, the present invention relates to a pump-operated on-board auxiliary fluid supply system that eliminates the need for a pressurized tank and is self purging of residual fluid. 
     II. Related Art 
     Transit concrete mixing trucks, sometimes referred to as ready-mix trucks, have long been in use. They are equipped with large chassis-mounted rotatable mixing drums for mixing and dispensing a quantity of concrete. The drums typically are mounted on an incline and have an opening in the upper end for receiving ingredients to be mixed and discharging mixed concrete products. Loading is accomplished through a charge hopper which extends a distance into the opening of the drum. The drum is further provided with internal helical flights or fins extending around its internal surface which acts to mix the concrete when the drum is caused to rotate in one direction and cause the concrete to be discharged out of the opening when the rotation of the drum is reversed. The upper portion of the drum includes a ring and roller system for drum support and rotation that is carried by a heavy pedestal support assembly. 
     After mixing and discharge, such concrete mixing drums retain an amount of residual concrete on the mixing fins and inner drum surface and discharge chutes which needs to be periodically washed out to prevent it from curing and hardening inside the drum and on external chutes. Therefore, it has become part of the operating routine to wash the interior of the drum and the discharge chutes one or more times per day. In addition, it may be necessary to add additional makeup water to a mix in the drum prior to discharge. 
     In conjunction with the use of makeup or washout water on transit concrete mixing trucks, it has further become a common practice to provide a water supply on the vehicle. The supply has included a water tank that has been typically pressurized to 50 psi or higher by a supply of air from a compressor carried on the truck. This, in turn, supplies water under pressure for washout or other uses through hoses and a valving system in a well-known manner. 
     Such a prior system is illustrated in  FIGS. 1   a  and  1   b  in which a concrete mixer truck, generally at  10 , having a mixing drum  12  and discharge chute  14  is provided with a pressurizable auxiliary water tank  16  mounted on the vehicle. As seen in  FIG. 1   b , the auxiliary water tank  16  includes an air inlet valve  20  that controls the flow of air under pressure from a pressure source (not shown) through an air supply line (also not shown). An air pressure regulator with gauge  22  is provided, together with a pressure relief or pop-off valve at  24 , which prevents over-pressurization of the system. A discharge outlet pipe or hose is provided at  26  suitably valved at  28 . The system may be purged by using pressurized air to clear the hose or pipe  26 . 
     More recently, however, government regulations have curtailed the use of such pressurized tanks in many areas and so it would be desirable to eliminate the need for pressurization of the tank without diminishing the washout or easy purge capabilities of the system. 
     SUMMARY OF THE INVENTION 
     By means of the present invention, there is provided a self-purging auxiliary fluid supply system for supplying water for washout or adding to batches in a truck-mounted concrete mixing drum. The system includes a truck-mounted fluid reservoir for containing a quantity of water, the reservoir being connected to supply non-pressurized fluid to a pump assembly. The pump assembly includes an air-operated diaphragm pump apparatus for supplying auxiliary fluid from the fluid reservoir under pressure to a discharge assembly which connects to a conventional washout/supply system associated with the operation of the mixing drum. The fluid supply system is provided with valving which enables it to quickly integrally purge itself after use. 
     Several embodiments are shown with different locations for the mounting of the pump of the invention. The system is designed for ease of manufacture or as a convenient retrofit system on existing transit concrete mixing trucks. The pump and piping system eliminate the need for pressurizing the reservoir tank and facilitate the draining or purging of associated water lines to prevent freezing in cold weather. A typical diaphragm pump of the invention uses air at about 100 psig to operate the pump and can supply up to 25 gpm of water at a pressure of about 10 psig for water injection or about 8 gpm at about 75 psig for washout. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, wherein like numerals depict like parts throughout the same: 
         FIG. 1   a  is a side elevational view of a transit concrete mixing truck carrying an auxiliary water system in accordance with the prior art; 
         FIG. 1   b  is an enlarged side elevational view of a prior art auxiliary water tank from the system of  FIG. 1   a;    
         FIG. 2  is an enlarged partial perspective view of an embodiment of an auxiliary water system in accordance with the present invention which utilizes a side pump mounting; 
         FIG. 3   a  is a view similar to  FIG. 2  illustrating an alternate embodiment of the auxiliary water system of the present invention; 
         FIG. 3   b  is an enlarged frontal view of the diaphragm pump of  FIG. 3   a;    
         FIG. 4  is an enlarged perspective view of another embodiment of the present invention using a tank-mounted pump; 
         FIG. 5  is a perspective view of another embodiment which utilizes a side pump mounting; and 
         FIG. 6  is an alternate embodiment of a water supply tank equipped with an additive supply tank. 
     
    
    
     DETAILED DESCRIPTION 
     Certain embodiments of the present invention will be described with reference to drawing figures. They represent examples of an auxiliary water supply system for a transit concrete mixing truck which provides high pressure water for washout or additional water to be added to the drum. The embodiments described are meant as examples and are not intended to limit the inventive concepts. 
     It is an important aspect of the present invention that the need for an expensive pressurized water supply tank is eliminated. In addition, the invention further provides a rapid self-purging feature to purge the system of water after use. 
       FIG. 2  depicts an enlarged partial perspective view of an embodiment of the invention which includes a side or frame-mounted pump. The system includes an auxiliary water supply tank  30  which may be fabricated from metal or non-metal materials and is shown carried by support pedestals or saddles  32 ,  33  fixed thereto by heavy straps  34 ,  35 . Saddles  32 ,  33 , in turn, are fixed to truck frame members  36 ,  38 , respectively. An air-operated diaphragm pump  40  is mounted on a bracket  42  fixed to the truck frame member  36 . An air supply inlet connection is shown at  44 , which connects to an air pressure supply tank or accumulator which is pressurized by a conventional source of high pressure air such as a compressor (not shown) used to operate diaphragm pump  40 . The pump  40  has a suction inlet at  46  including a tee, one side of which is connected to a water feed line  50  which, in turn, is connected to the tank  30  at  52 . 
     The tank discharge is preferably a top discharge, bottom draw system using a conventional bottom draw standpipe tube (not shown) that is connected to outlet  52  at the top and extends to the bottom of the tank. This greatly facilitates hose system drainage after use. However, a bottom discharge arrangement can also be used. The tee also leads to a manually operated ball valve  54  used to drain and purge the system. The pump discharge outlet manifold shown at  56  is connected to a pump discharge hose  58  usable for washout or adding water to the drum. The water tank  30  is further provided with a breather vent  60  and fill opening  62 . The pump discharge hose  58  is connected to conventional suitable control valves (not shown) in a well known manner. 
       FIGS. 3   a  and  3   b  depict an alternative trailer-mounted embodiment which uses a mounting bracket  70  mounted flush with trailer frame member  72 . In this embodiment, the water feed line  74  is shown as being connected to a tank discharge outlet on the bottom of the tank  30  and the upper outlet  52  is suitably capped at  76 . Of course, a top discharge, bottom-draw connection could also be used. A ball valve is provided in the intake line at  78 . As best seen in  FIG. 3   b , the input/drain line between valves  78  and  54  is inclined slightly downward to valve  54 . This is to assure easy drainage when valve  54  is opened after the system is used. 
     Another embodiment is depicted in  FIG. 4  in which the air-operated diaphragm pump is mounted on the fluid supply tank itself. The pump is fixed to a mounting plate  90  which is mounted to the upper surface of the tank  30 . This embodiment also includes a water feed line  50  which accesses the tank  30  from the top at  52  and which also preferably uses a bottom draw standpipe system. 
       FIG. 5  depicts yet another embodiment of an auxiliary fluid supply system in accordance with the invention in which the air-operated diaphragm pump  40  is mounted to the side of the fluid supply or water tank  30 . The pump is mounted on a bracket having a platform  90  and side members  92 . The bracket is attached to a stable mounting stand structure  94  which, in turn, is mounted on a truck alongside tank  30  in any convenient location in a well known manner. Connections between the tank and pump and the pump include top mounted water feed line  50  and discharge hose  58 . A drain valve  54  is also shown. 
       FIG. 6  depicts an alternative embodiment of a water supply tank at  100  which is carried by a pair of spaced pedestals  102  and  104  and heavy attaching straps  106  and  108 . A fill opening is shown at  110  and a breather vent at  112 . A top discharge, bottom draw connection is shown at  114  with outlet hose  116 . The tank  100  further carries a smaller reservoir  118  containing additive material to be blended into the water supplied from the main auxiliary water supply tank  100  using supply hose  120  suitably valved at  122 , which can be manifolded with supply hose  116  at the pump input or other conventional mixer system in a well known manner. 
     In operation, with a supply of water or other desirable fluid in the tank  30 , the conventional output control valves (not shown) are opened in accordance with the use of the system and the diaphragm pump  40  is supplied with high pressure air, generally about 100 psig. The diaphragm pump  40  is operated to provide intake suction and pressurized fluid in the discharge line. When the desired amount of water is supplied for the desired use, the control valves in the pump discharge hose  58  and the drain/input valve  54  is opened. This allows water in the line to drain from the pump and also allows the pump to pump air through the system thereby purging out all the lines. This is particularly advantageous to avoid freezing of the system in cold weather. 
     This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the example as required. However, it is to be understood that the invention can be carried out by specifically different devices and that various modifications can be accomplished without departing from the scope of the invention itself.