You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
     This invention relates to apparatus used for hydrovac excavation. 
     BACKGROUND OF THE INVENTION 
     In hydrovac excavation, a jet of water is blasted into soil to liquify the soil and then the liquified soil is sucked up using a vacuum truck. The jet of water is directed into the soil using a blast wand that is manually operated. Various types of wand have been used for this purpose. Typically, the wand consists of a pipe with a valve on one end and blast nozzles on the other end. The blast nozzles generally blast straight out, in the direction of the pipe, so the thrust of the nozzles pushes against the pipe handle, thus tiring the operator. Also, with the nozzles blasting straight out, a hole is created in the soil and rebounding water shoots directly back at the operator&#39;s face and body. This makes the wands dirty to use, and potentially dangerous due to soil fragments shooting into the face and eyes of the operator. 
     SUMMARY OF THE INVENTION 
     These difficulties with prior art hydrovac wands are addressed with the following invention. 
     According to an aspect of the invention, a hydrovac wand is provided with a crossfire nozzle arrangement that reduces thrust to the wand operator, and that has a spray pattern that eliminates spray back. In another aspect of the invention, a pair of jets erode a hole while two other jets push the debris back to a suction hose. In another aspect of the invention, a two high pressure swivels are provided at the end of the wand to allow the wand to rotate in all directions without binding. In a still further aspect of the invention, boom controls are placed on the wand to maximize digging rates. 
     These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     There will now be described preferred embodiments of the invention, with reference to the drawings, by way of illustration only and not with the intention of limiting the scope of the invention, in which like numerals denote like elements and in which: 
     FIG. 1 shows a side view of a hydrovac blast wand according to the invention; 
     FIG. 2 is a side view of a nozzle arrangement for the hydrovac blast wand of FIG. 1; 
     FIG. 3 shows a hydrovac blast wand and hydrovac truck according to the invention showing a first boom position; 
     FIG. 4 shows a hydrovac blast wand and hydrovac truck according to the invention showing a second boom position; and 
     FIG. 5 is a close up of an end of the hydrovac blast wand showing boom controls. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In this patent document, “comprising” means “including”. In addition, a reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present. 
     In FIG. 1, a hydrovac digging device is formed with a hydrovac blast wand  10  has a control end  12  and digging end  14 . At the digging end  14  is a nozzle arrangement formed of two pairs of nozzles  16 . Each nozzle  16  is oriented at 45° to the wand axis, and at 90° to the other nozzle in its pair. The nozzles  16  are in symmetric pairs at an angle to the wand axis, that is, the nozzles of a pair have the same angle to the wand axis but are oppositely arranged. In this arrangement, the net thrust due to the nozzles is reduced in the direction of the wand axis to lower than the sum of the thrusts of the nozzles when they are directed in the same direction. It is preferred that the pairs of nozzles are arranged side by side in the same plane. However, other arrangements are possible, and additional nozzles may be used. The difficulty with not having the nozzles symmetrically arranged is that if the thrust imparted by the nozzles is unbalanced, a net sideways force is placed on the wand that is difficult to control. The nozzles need not be at 45° to the wand axis. For example, some slight benefit is obtained if the nozzles are at, say 10°, but the improvement is not great. And, above 45°, the forward thrust becomes unnecessarily reduced for most applications. The nozzles could be made to swivel if desired, for different digging applications. The embodiment shown is two dimensional, with the nozzles arranged in a line. The nozzle arrangement may also be three dimensional, for example with the nozzles forming a four sided pyramid, the hydrovac blast wand being at the apex and the nozzles forming the edges of the pyramid that meet at the apex. Such a nozzle arrangement is more difficult to build. One of the advantageous features of the design shown is that the nozzle arrangement may be simply made with readily available parts. In the embodiment shown, the digging end is formed of a coupling  50  with screw connections to both the wand  10  and screwed ell  52 , a pair of screwed tees  54  connected to the screwed ells by nipples  56 , and water jets  58  for the nozzles. 
     Nozzle protection is provided by a rod or rods  19  that are connected as by welding to the nozzles at some convenient point so that the rods  19  are out of the way of the nozzle jets, but still protect the nozzles against banging into hard objects. A handle  23  is provided on the hydrovac blast wand  10  at a convenient location nearer to the control end than the digging end to allow the hydrovac blast wand to be easily manipulated. 
     Connections are provided at the control end  12  for supplying fluid through the hydrovac blast wand  10  to the nozzle arrangement. A pair of swivels  20 ,  22 , interconnect a high pressure hose  24  and the hydrovac blast wand  10  (through a reducing union  21 ) to provide a fluid path from the hose to the nozzles. The swivels  20 ,  22  are oriented at an angle to each other preferably at a right angle. The swivels  20 ,  22  are readily purchased off the shelf. The hose  24  is also readily commercially available, and may be for example a 10 foot whip of ⅜″ hose. 
     As shown in FIGS. 3 and 4, the hydrovac digging device is used in combination with a hydrovac truck (or trailer)  30  having a boom  32  supported on a boom support  33 . The hydrovac truck  30  is conventional, and includes a water tank  34  that sits on the bed  36  of the truck. The boom  32  is movable up and down with hydraulic arm  38  that interconnects the boom  32  and the bed  36  of the truck  30 . A vacuum hose  37  is supported by the boom  32  and runs off to the tank  34 . The boom  32  is also rotatable about the boom support  33  with a boom rotator  40 . Boom controls  42  (FIG. 5) are provided at the control end  12  of the hydrovac blast wand  10 . Hydrovac trucks, booms, vacuum hoses, and boom controls are all themselves conventional and not described further here. The location of the boom controls  42  is believed to be novel. Boom control leads  44  run off to the conventional boom and fluid supply control box  46 . 
     The hydrovac blast wand is operated conventionally. The operator holds the wand the handles, while fluid is directed through the nozzles into the soil. The vacuum hose  37  is manipulated with the boom  32  using the boom controls  42  to place the vacuum hose in position to suck up liquified soils. The swivels  20 ,  22  allow the hydrovac blast wand  10  to be easily moved around in relation to the high pressure hose. 
     The following materials have been used in an embodiment of the invention: 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Item 
                 Description 
               
               
                   
                   
               
             
             
               
                   
                 10 
                 ½″ SA 106B tube 
               
               
                   
                 19 
                 {fraction (3/16)}″  rod bent to shape 
               
               
                   
                 20, 22 
                 ⅜″  hydraulic 90° swivel 
               
               
                   
                 21 
                 ½-⅜″  reducing union 
               
               
                   
                 23 
                 ½″ round bar 
               
               
                   
                 24 
                 SAE 4000 PSI single wound hydraulic hose 
               
               
                   
                 50 
                 ½″ half coupling 3000# rating NPT ends SA105 
               
               
                   
                 52 
                 ¼″ 90° elbow 3000#  rating NPT ends SA105 
               
               
                   
                 54 
                 ¼″ equal 3000# rating NPT ends SA105 
               
               
                   
                 56 
                 ¼″ SA106B tube 1″ LG 
               
               
                   
                 58 
                 ¼″ TECSI-¼″-MC4-04/0 water jets 
               
               
                   
                   
               
             
          
         
       
     
     Immaterial modifications may be made to the invention described here without departing from the essence of the invention.

Summary:
A hydrovac wand is provided with a crossfire nozzle arrangement that reduces thrust to the wand operator, and that has a spray pattern that eliminates spray back. A pair of jets erode a hole while two other jets push the debris back to a suction hose. Two high pressure swivels are provided at the end of the wand to allow the wand to rotate in all directions without binding. Boom controls are placed on the wand to maximize digging rates.