VEHICLE AND TANKS FOR HYDRO EXCAVATION
This invention is in the field of excavating equipment and in particular hydro excavating equipment where high pressure water is used to loosen soil, which is then vacuumed out of the hole to create the excavation.
BACKGROUND
Hydro excavation is popular, especially when excavating around existing buried pipes, cables, and the like. A high pressure water stream is used to loosen soil, and a vacuum system sucks up the slurry of water and loosened soil and deposits same into a slurry tank. A typical vehicle, either a truck or trailer bed, that is equipped for hydro excavation carries a water tank to supply water, and a slurry tank for collecting the mixture of soil and water that is removed by the vacuum. Hydro excavating equipment is disclosed for example in United States Patent Numbers 5,295,317 to Perrot and 5,408.766 to Pobihushchy.
On a typical hydro excavation vehicle, such as the TornadoT" Hydrovac truck manufactured by Tornado Corporation of StettlerõAlberta, Canada the water and slurry tanks are provided by placing a divider in a horizontal cylindrical tank such that the front portion of the tank holds water and the rear portion holds the slurry. The tank capacities range from 550 gallons of water and 4.0 cubic yards of slurry to 2366 gallons of water and 13.0 cubic yards of slurry.
It can be seen that initially the water tank will he full, and the slurry tank will be empty, and that during operation water will be drawn out the water tank and slurry will be drawn into the slurry tank. Thus the balance of weight carried on the vehicle will shift during the excavation process from the front to the rear. This shifting of weight can adversely affect the handling of the vehicle, and the shift of weight can cause one axle of the vehicle to become overloaded while another is under-loaded.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a vehicle and tank apparatus for hydro excavation that overcomes problems in the prior art.
The present invention provides a vehicle and tank apparatus for hydro excavation. The apparatus comprises an inner tank, and an outer tank substantially enclosing the inner tank such that a water space is created between walls of the inner and outer tanks. A
water pump is operative to draw water from the water space and direct same to a pressure nozzle, and a vacuum system is operative to draw a mixture of water and excavated soil into the inner tank. A vehicle bed mounted on wheels for movement along the ground supports the inner and outer tanks, water pump, and vacuum system.
Enclosing the inner slurry tank inside the outer tank forms a water storage space between the tank walls. This arrangement allows the tanks to be configured so that as water is drawn out of the water space during operation, and slurry is vacuumed into the inner slurry tank, the center of gravity of the tank assembly remains at the same location on the vehicle bed, as opposed to prior art tank arrangements where the weight distribution shifts during operations. Improved stability and weight distribution on the vehicle wheels is improved significantly. The apparatus is readily configured to achieve desired proportions of the capacities of the inner and outer tanks for slurry and water DESCRIPTION OF THE DRAWINGS

2 While the invention is claimed in the concluding portions hereof, preferred embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where:
Fig. I is a schematic cut away side view of an embodiment of a vehicle and tank apparatus of the present invention for use in hydro excavation operations;
Fig. 2 is a schematic front view of the embodiment of Fig. 1;
Fig. 3 is schematic sectional view along line 3-3 in Fig. I;
Fig. 4 is a schematic side view of an alternate embodiment of the vehicle and tank apparatus of the present invention configured such that the axis of the tanks is vertically oriented;
Fig. 5 is a schematic top view of the embodiment of Fig. 4;
Fig. 6 is a schematic cut away side view of an alternate embodiment of a vehicle and tank apparatus of the present invention where the tanks are oriented horizontally and have the same length.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Figs. 1 - 3 schematically illustrate an embodiment of a vehicle and tank apparatus 1 of the present invention for use in hydro excavation operations. The apparatus I
comprises an inner tank 3, and an outer tank 5 substantially enclosing the inner tank 3 such that a water space 7 is created between walls of the inner and outer tanks 3, 5. A water pump 9 is

3 operative to draw water from the water space 7 and direct same to a pressure nozzle 11, and a vacuum system 13 is operative to draw a mixture of water and excavated soil 15 into the inner tank 3. A vehicle bed 17 is mounted on wheels 19 of a truck or trailer for movement along the ground and supports the inner and outer tanks 3, 5, water pump 9, In the illustrated apparatus 1 the inner and outer tanks 3, 5 are cylindrical and are oriented with axes A thereof substantially horizontal. The cylindrical shape of the inner tank 3 provides the strength necessary to resist the pressure exerted thereon by the vacuum Front and rear end portions 3F, 3R of the inner tank 3 extend about an equal distance outward from corresponding first and second ends 5F, 5R of the outer tank 5, and front and rear annular cover plates 21 are fastened between the ends 5F, 5R of the outer tank 5 The front and rear annular cover plates 21 support the inner tank 3 above a bottom wall of the outer tank 5, such that the tanks do not contact each other, avoiding damage from .7)5 Because the center of gravity CG of the inner and outer tanks 3, 5 is at the same location on the vehicle bed 17 midway between the front and rear ends of the inner tank 3, it can be seen that as water is drawn out of the outer tank 5 and the mixture of water and

4 excavated soil 15 is drawn into the inner tank 3, the center of gravity CG of the assembly of inner and outer tanks 3, 5 will stay at the same location. The weight on the wheels 19 will change but the proportion on each will remain about the same as well.
By sealing one of the annular cover plates 21 to the inner tank walls by caulking or the like instead of welding same, the bolts on the flanges 23 can be removed, and the inner tank 3 removed from the outer tank 5 to allow for repair and maintenance of the outer tank 5 if necessary.
It is contemplated as well that, as in the apparatus 101 schematically illustrated in Fig. 4, the inner and outer tanks 103, 105 could be oriented with axes A thereof substantially vertical on the vehicle bed 117. In the illustrated apparatus 101, the inner tank 103 extends above a top edge of the outer tank 105, and an annular cover plate 121 between the top edge of the outer tank 105 and .the inner tank 103 seals the top of the outer tank 105. The water space 107 is between the walls of the tanks 103, 105, and inner and outer access ports 125, 127 through the tank walls are provided for connection of the water pump and vacuum system The center of gravity of the apparatus 101, as in the apparatus 1 described above, remains in the same location on the vehicle bed 117 as material moves into and out of the tanks 103, 105. Fig. 5 illustrates a top view of the apparatus 101, showing that the outer tank 105 can he rectangular instead of cylindrical. So long as the outer tank 105 is located with a center thereof located on the axis A of the cylindrical inner tank 103, the center of gravity will remain at the same location. To vary the proportions of the capacities of the inner and outer tanks 103, 105 the diameter, length, width, and height thereof can be varied.

5 Orienting the tanks 103, 1.05 vertically limits the size of the tank, since width and height restrictions generally apply on public roads where the vehicle will be travelling. The horizontal orientation of Fig. 1 allows one or both of the tanks 3, 5 to be lengthened to increase the capacity thereof, since allowable vehicle lengths are considerably greater than allowable heights. The inner and outer tanks 3, 5 can be lengthened or shortened relative to each other to achieve a desired proportion of the capacity of the inner tank 3 to the capacity of the outer tank 5.
Fig. 5 schematically illustrates an apparatus 201 where the inner and outer tanks 203, 205 are oriented horizontally on the vehicle bed 217, and are the same length. A
full cover assembly 229 is attached to each end of the inner and outer tanks 203, 205 and is operative to close the ends of the inner and outer tanks 203, 205 and support the ends of the inner tank 203 above the bottom wall of the outer tank 205. The full cover assembly 229 could include an existing end wall of the inner tank 203, with lugs or the like extending inward from a plate to support the inner tank 203, with the plate bolted to the flanges 223 on the outer tank 205. The inner tank 205 would then be removable.
Other cover assemblies that would occur to a person skilled in the art could be used as well.
To vary the proportions of the capacities of the inner and outer tanks 203, 205 the diameters thereof could be varied, or alternatively Fig. 5 also shows that one end 203A of the inner tank 203 could extend outward from the end of the outer tank 205, as in the apparatus I described above. Such a configuration may be desirable in some circumstances, however the center of gravity will shift somewhat as material moves in and out of the tanks 203, 205.
The water space 207 is between the walls of the tanks 203, 205 and inner and outer access ports 225, 227 are provided through the full cover assembly 229 for connection of the water pump and vacuum system.

6 The vehicle and tank apparatus of the present invention for use in hydro excavation operations of the present invention provides a vehicle with improved stability and weight distribution. The apparatus is readily configured to achieve desired proportions of the capacities of the inner and outer tanks for slurry and water.
The foregoing is considered as illustrative only of the principles of the invention.
Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.

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