Method and nozzle assembly for fluid jet penetration of a work material

A method for improved penetration of a work material using a high velocity fluid jet from a nozzle element by providing a sealed chamber between a surface of the work material and the nozzle element is described. With hard and/or irregular materials, a deformable element is provided between the nozzle element and the work surface so that the deformable element conforms to the surface to effect the seal. A preferred nozzle element assembly including the deformable element is also described. The method is particularly adapted to mining operations such as coal, hard rock excavation, and wood impregnation.

SUMMARY OF THE INVENTION 
The present invention relates to the method and nozzle assembly for 
producing an improved high velocity jet. More particularly the present 
invention relates to a method for producing a high velocity jet which more 
rapidly and/or effectively penetrates a work material. 
PRIOR ART 
High velocity fluid jets (above about 10,000 psi or 700 kg per sq cm fluid 
ejection pressure) are well known to those skilled in the art and have 
found significant commercial usage. My U.S. Pat. Nos. 3,524,367; 
3,532,014; 3,705,693; 3,851,899 and 3,750,961 describe methods and nozzle 
assemblies for producing such jets. 
In general it has been found that it is important to have a standoff 
distance of between 5 and 500 nozzle diameters between the ejection point 
from the fluid jet nozzle and a surface of the work material in order to 
develop good penetration. As a result there tends to be considerable 
splashback from the surface as the jet penetrates the material. Further, 
with thick cross-sectioned and/or irregularly textured materials, the jet 
rapidly begins to wander away from its longitudinal axis after 
penetration. Further still, where the surface of the work material is hard 
and irregular, the surface tends to deflect and dissipate the energy of 
the jet. 
It is therefore an object of the present invention to provide a method and 
nozzle assembly which eliminates jet splashback and which tends to 
maintain the jet on its axis as it penetrates the work piece. It is 
further an object of the present invention to provide a method and nozzle 
assembly which allows for penetration along the axis of the jet into a 
surface of a work material which is slanted in a plane which is not 
perpendicular to the axis of the jet. Further still it is an object of the 
present invention to provide a nozzle assembly which is simple and 
inexpensive to construct. These and other objects will become increasingly 
apparent by reference to the following description and the drawing.

GENERAL DESCRIPTION 
The present invention relates to an improvement in the method of 
penetrating a work material with a high energy fluid jet ejected from a 
nozzle element which comprises: providing an essentially sealed chamber 
between the fluid ejection point from the nozzle element and a surface of 
the work material; and ejecting a high energy fluid jet through the nozzle 
at a fluid pressure upstream of the nozzle which develops to at least 
about 700 kilograms per square centimeter (10,000 psi) until the work 
material is penetrated to the desired extent. Preferably the sealed 
chamber is provided in part by a deformable element with a tubular opening 
forming part of the chamber compressed between the nozzle element below 
the fluid ejection point and the work material. 
The present invention also relates to an improved fluid jet nozzle element 
for penetrating a work material which comprises: a rigid nozzle element 
with a fluid exit point for a high velocity fluid jet; and a deformable 
element with a tubular opening adjacent and surrounding the exit point of 
the nozzle element for positioning in contact with a surface of the work 
material to form a sealed chamber. Preferably the deformable element is 
composed of an elastomer. 
FIG. 2 shows a nozzle assembly 10 according to the present invention in 
contact with a surface 11 of a work material 12 wherein a hole 13 (shown 
as enlarged) has been penetrated into the material 12 by a high velocity 
fluid jet. A deformable element 14 is compressed against the surface 11 in 
order to provide a seal. In the nozzle assembly 10 shown in FIG. 2, the 
deformable element 14 is supported by a holder 15 having an annular lip 
15(a) for holding the resilient element 14 in place. A bulge 14(a) is 
formed on the deformable element 14 due to compressing the assembly 10 
against the work surface 11. Thus a sealed chamber 20 is formed to confine 
the fluid jet prior to penetration of the material 12. 
A sapphire nozzle 16 is mounted in a metal casing (not shown) which bears 
on a shoulder 17 of the holder 15. A fluid inlet conduit 18 leads into the 
holder 15 in contact with an annular elastic ring 19 so as to compress the 
ring 19 onto the sides of the casing for nozzle 16 to seal the nozzle 16 
from leakage. 
The deformable element 14 has sufficient strength to seal the chamber 20 
when subjected to the fluid pressure from the jet during penetration of 
the work material 12. A ring seal or a cylindrical tube of a deformable 
material functions satisfactorily. As shown hereinafter in the Examples, a 
tube of deformable material where the outside walls are unsupported will 
function satisfactorily. 
FIG. 3 shows a prior art nozzle assembly 21 which is similar to that in 
FIG. 2 except that the deformable element 14 is not present. The nozzle 
assembly 21 is described in detail in FIG. 4. As the jet pierces a hard 
work surface such as encountered in mining the jet splashes away from the 
surface. Also penetration time is greater with certain materials. 
FIG. 4 shows the nozzle assembly 21 of FIG. 3 in detail wherein a material 
22, particularly wood, which has a deformable surface 23 and which is soft 
enough to form a fluid seal with the smooth end 24 of a metal holder 25. 
An inlet conduit 26, nozzle ring seal 27 and nozzle 29 are provided 
mounted as shown in FIG. 4. A sealed chamber 30 is provided in this manner 
for penetrating the surface 23 of the material 22 by compressing the 
surface 24 of the holder 25 against the material 22 surface 23. Straight 
penetration by the jet 32 is achieved. As shown in FIG. 5, where wood is 
to be pierced at an angle to the annular rings 31 with a conventional 
standoff of the nozzle assembly 21, the result is that the jet 32 will 
wander away from the axis of penetration using the prior art method. 
The seal in the chambers 20 or 30 that is formed does not have to be 
perfect and can allow for minor leakage of fluid. However, as will be 
apparent to those skilled in the art, the enhanced penetration effect is 
lost if there is substantial fluid leakage. 
In the nozzle assembly of the present invention, there is preferably a 
standoff distance of between 5 and 200 nozzle diameters between the 
surface of the work material and the nozzle fluid ejection point. The 
nozzle usually is circular in cross-section and has a diameter between 
about 0.002 and 0.100 inch (0.05 and 2.5 mm). 
Where a tubular deformable element is provided forming the chamber between 
the nozzle holder and the surface of the work material, the opening in the 
deformable element has a length, along with the portion of the holder 
below the nozzle exit, which corresponds to the standoff distance. 
Preferably the thickness of the tubular deformable element is between 
about 1 to 5 cm. The tubular deformable element has an opening having a 
width of at least the diameter of the nozzle opening up to about one inch 
(2.5 cm). 
The deformable element is preferably made of a resilient elastomer such as 
rubber for ease of sealing with rough, hard surfaces, although a 
tetrafluoroethylene polymer with a low coefficient of friction can be used 
where there is to be sliding contact with the work surface subsequent to 
piercing. The clamping pressure on the deformable element is usually at 
least about 20 psi (1.4 kg/sq cm) for a resilient elastomer. More clamping 
pressure would be required for a deformable metal seal. 
SPECIFIC DESCRIPTION 
The following Examples specifically illustrate the method of the present 
invention in contrast to the prior art. 
EXAMPLE 1 
The apparatus used in this Example is similar to that illustrated in FIGS. 
2 and 3, except that a rubber stopper was pressed between the nozzle 
holder and the work surface. The prior art method of FIG. 3 was tried 
first. 
The material to be pierced was quartzite, approximately 5/8 inch (1.59 cm) 
in thickness with a standoff of 3/4 inch (1.9 cm) between the nozzle 
holder and the work surface. Using ordinary filtered tap water, a 0.010 
inch (0.0254 cm) diameter sapphire nozzle, and building pressure from 0 to 
40,000 psi (0 to 2800 kg per sq cm) maximum, the time to reach full 
pressure being approximately 8 seconds, the jet was directed at the 
quartzite for a period of 1 minute. After this interval of time, the jet 
either did not pierce through the work or just broke through after the one 
minute period. 
Using the apparatus similar to FIG. 2, with an ordinary laboratory black 
rubber stopper one inch (2.54 cm) in thickness and having a one inch (2.54 
cm) diameter, compressed between the work and the nozzle holder, the 
average time required for piercing the rubber and quartzite was only 12 
seconds, representing a very large improvement (about five times) in the 
speed of piercing. The jet was allowed to initially penetrate the rubber 
stopper in this Example although this is unnecessary. The clamping 
pressure on the stopper was about 10 psi (0.7 kg/cm) and there was very 
little leakage from the chamber. 
EXAMPLE 2 
Example 1 was repeated on a piece of lead 1/2 inch (1.27 cm) in thickness 
using the apparatus of FIG. 3 and after one minute the jet did not pierce 
through the lead, although a small bubble was apparent on the underside in 
some cases. When the rubber stopper was inserted as in Example 1, the 1/2 
inch (1.27 cm) thickness was pierced within 15 seconds. In this Example, 
the jet without the sealed chamber would not even penetrate the work piece 
since the latter was soft enough to deflect the jet without being pierced. 
EXAMPLE 3 
Repetition of Example 1 on a sheet of 1/4 inch (0.63 cm) hard aluminum 
plate seemed to show no particular speed advantage with the rubber 
stopper, however the hole was larger and more uniform in cross-section and 
there was no splashback. 
EXAMPLE 4 
Using a block of Douglas fir wood, 31/2 inches (8.75 cm) in thickness, with 
a distance of approximately 1/4 inch (0.63 cm) between the nozzle holder 
and the work surface, the jet was directed at the wood using the prior art 
method as shown in FIG. 5. The growth ring orientation in the block was at 
an angle as indicated in FIG. 5, and the jet pierced the block for a 
distance of about 3/4 inch (1.9 cm) and was then deflected along the 
softer portion of the growth rings, and shot out the side of the block at 
a distance of approximately 11/2 inches (3.8 cm), a few seconds after full 
pressure of 40,000 psi (2800 kg per sq cm) was reached. 
When the method was repeated with the nozzle pressed at a pressure of about 
20 psi (1.4 kg/sq cm) in clamping contact with the work surface as shown 
in FIG. 4, thus eliminating the air gap and forming the sealed chamber 30, 
the block was pierced to its full depth cleanly and neatly in less than 9 
seconds. It was observed that full pressure of the jet had not yet been 
reached. This indicates that a lower fluid pressure can be used to obtain 
complete penetration using the method of the present invention. 
As can be seen from the foregoing Examples, the penetration by the high 
velocity jet is much straighter and faster using the sealed chamber. The 
apparatus is particularly important in the mining of mineral materials 
using the deformable element to form a seal with an irregular work 
material. It is also significant for piercing and impregnating materials 
such as wood.