Method for impregnating timber with a liquid and injector therefor

This invention relates to an all gas-loadable liquid injector. The gas-loadable liquid injector comprises an accumulator for containing a liquid and a propellant gas, a liquid delivery tube for insertion into a material to be treated by the liquid, and intermediate means between the liquid delivery tube and the accumulator. The intermediate means restricts the flow of liquid when the pressure in the accumulator substantially exceeds that in the delivery tube and allows a restricted flow of liquid when the pressure in the accumulator is substantially equal to or less than that in the delivery tube. The intermediate means has a flexible and collapsible tube extending into the accumulator from the bowels of the accumulator and a straight rigid tube having a free end. The free end of the rigid tube always lies at the lowest level in the accumulator regardless of the altitude of the injector so as to dip into any liquid in the accumulator.

Related Application 
This application is a continuation of PCT/GB90/0457 filed Mar. 27, 1990. 
BACKGROUND OF THE INVENTION 
This invention relates to a liquid injector and particularly to an injector 
for impregnating timber with a liquid wood preservative, or brick with a 
damp-proofing liquid, the injector being an easily portable unit which can 
be either taken to its site of use in a self-powered condition ready for 
use or can be easily put into such condition on site. 
SUMMARY OF THE INVENTION 
Gas-loadable injectors are known from CH, A, 272 644 and DE, B, 121 4861 
comprising an accumulator for containing a liquid and a propellant gas, 
and a liquid delivery tube for insertion into a material to be treated by 
the liquid. 
The invention is characterised by intermediate means between the liquid 
delivery tube and the accumulator for restricting flow of liquid when the 
pressure in the accumulator substantially exceeds that in the delivery 
tube and for allowing unrestricted flow of liquid when the pressure in the 
accumulator is substantially equal to or less than that in the delivery 
tube. 
Because of this, the injector can be re-charged with liquid through the 
delivery tube. This enables the injector to be used successfully in a 
method of continued impregnation of a body comprising initially setting up 
a jig on the body, with the use of the jig boring two intersecting holes 
into the body, the first hole opening into the body at a position intended 
to become inaccessible and the second hole opening into the body at a more 
accessible position, removing the jig, installing an injector such as 
described above by inserting the liquid delivery tube into the first hole, 
closing-off the second hole, beginning the injection of liquid into the 
body, burying or otherwise rendering the injector inaccessible, after a 
predetermined period opening the second hole, introducing fresh liquid 
under pressure into the second hole from outside so as to back-fill and 
repressurise the accumulator and closing-off the second hole so that 
continued impregnation can take place from the injector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 a gas-loadable injector comprises an accumulator formed of a 
first plastics shell 1, a second plastics shell 2, and a plastics membrane 
and ring member comprising a membrane 4 and a ring 3. The ring 3 is 
hot-plate welded at 5 to the shells 1 and 2. A plastics pressure seal 6 is 
screwed into an opening 7 in the shell 1 remote from the welded ring. Also 
remote from the welded ring the shell 2 has an integral boss 8 onto which 
is screwed a cap and delivery tube member comprising a cap 9 and a 
delivery tube 10 having a coarse external screw thread. 
Within the boss 8 there is a chamber 11 which flares from one side of a 
throat 12 with fine grooves 13 in the flare. A ball 14 is retained in the 
chamber 11 by means of a cruciform piece 15 screwed into the chamber 11 
from the interior of the shell 2. A frangible seal 16 is screwed into 
another chamber in the boss 8 on the other side of the throat 12 and 
between the throat 12 and a nose portion 17 of the cap 9, which portion 17 
has a through-bore 18 communicating with the delivery tube 10. On the rim 
of the cap 9 and a shoulder on the boss 8 there are co-operating ratchet 
teeth 19 which permit the cap 9 to be screwed on the boss 8 but prevent 
unscrewing of the cap 9 from the boss 8. The unstressed shape of the 
membrane 4 is shown in full lines. 
The injector is charged in the following manner. The seals 6 and 16 and the 
cap 9 and delivery tube 10 are removed. This enables the interior of the 
two shells 1 and 2, with the membrane 4 in its full line position, to be 
at atmospheric pressure initially. The seal 6 is screwed back into place 
and the liquid is forced into the shell 2 under pressure until the 
membrane is distended into a position as shown in broken lines. As the 
supply of liquid to the shell 2 is disconnected the pressure in the shells 
1 and 2 forces the ball 14 to seal against the throat 12. There will be 
very little seepage of liquid through the grooves 13 until a replacement 
seal 16 is screwed into place. A frangible plastics washer with a ring 
pull (not shown) is placed about the boss 8 and on the shoulder having the 
teeth 19. The cap 9 is then screwed onto the boss 8 and into contact with 
its teeth 19 on the frangible washer. In this condition the nose 17 has 
not pierced the seal 16. 
When the charged injector is to be used, it is turned as a whole, while 
screwing the tube 10 into a pre-bored hole in a timber to be treated until 
a sealing pad 20 about the tube 10 is hard against the timber. Then the 
frangible washer is broken and pulled clear so that the cap 9 can be 
screwed home on the boss 8. In so doing, the nose 17 pierces the seal 16 
and causes the ball 14 to seat on the throat 12 whereupon liquid is fed 
through the grooves 13 at a controlled rate and into the timber. While the 
pressure in the shell 2 is substantially greater than in the tube 10 the 
ball 14 remains seated on the throat 12 so that outward flow of liquid is 
restricted. When the pressure in the shell 2 is substantially equal to or 
less than the pressure in the tube 10 on the ball 14 leaves the throat 12 
so as to allow unrestricted flow through the throat 12. Because of this 
the injector can be re-charged with liquid through the tube 10. It will be 
noted that the walls of the shells 1 and 2 are thinned at 21 so as to be 
more translucent than the remainder of the walls. This enables the 
positions of the membrane 4 to be observed, particularly if it has a 
contrasting colour. 
Another form of gas-loadable injector is shown in FIG. 2 and for simplicity 
the same reference numerals are used to identify corresponding parts as in 
FIG. 1. In FIG. 2 the injector again comprises an accumulator formed of a 
first shell 1 of flexible plastics and a second shell 2 of a more rigid 
plastics. The shells 1 and 2 are hot-plate welded together at 5. Again, 
the shell 2 has an integral boss 8 onto which is screwed a cap and 
delivery tube member comprising a cap 9 and a delivery tube 10 having a 
coarse external screw thread. However, unlike FIG. 1, the boss 8 is formed 
on a re-entrant portion 22 of the shell 2 and the co-operating ratchet 
teeth 19 are consequently formed differently. In FIG. 2 the flared chamber 
11 has a plain flare from the throat 12 and the ball 14 is resiliently 
urged into contact with the throat 12 by a compression spring 23 seated in 
an insert 24 screwed into the chamber 11. The frangible seal 16, the nose 
portion 17, the through-bore 18 and the sealing pad 20 are identical with 
those in FIG. 1. 
The insert 24 has a bored spigot 25 onto which is fitted one end of a 
flexible and collapsible tube 26. A straight rigid tube 27 has one end 
fitted into the other end of the tube 26 and the other end of the tube 27 
lies at the lowest level within the shells 1 and 2 as shown by various 
broken lines dependent upon the attitude of the injector. 
Directly opposite the re-entrant portion 22 of the shell 2, the shell 1 has 
a depression 28 from which a stem 29 extends inwardly. A disc 30 is 
mounted on the inner end of the stem 29 so as to deflect the free end of 
the tube 27 from contact with the inner side of the depression 28. Within 
the depression 28 there are provided spines 30a and a step 31 for contact 
with one end of a curved strap-like metal spring 32. Another step 33 for 
contact with the other end of the spring 32 is provided on the shell 2 
near the re-entrant portion 22. 
The injector is charged in the following manner. The seal 16, the cap 9 and 
delivery tube 10, and the spring 32 are removed. The liquid is forced into 
the shells 1 and 2 under pressure so as to trap and pressurise therein. As 
the supply of liquid to the shells 1 and 2 is disconnected the ball 14 
seats on the throat 12 and retains the liquid under pressure within the 
shells 1 and 2. A replacement seal 16 is then screwed into place. A 
frangible plastics washer with a ring pull (not shown) is placed about the 
cap 9 which is then screwed onto the boss 8 until the washer is clamped 
between the teeth 19. In this condition, as before, the nose 17 has not 
pierced the seal 16. 
When the charged injector is to be used, the spring 32 is applied as shown 
and the injector is turned as a whole, while screwing the tube 10 into a 
pre-bored hole in a timber to be treated, until the sealing pad 20 is hard 
against the timber. Then the frangible washer is broken and pulled clear 
so that the cap 9 can be screwed home on the boss 8. In so doing, the nose 
17 pierces the seal 16 and dislodges the ball 14 by means of a rod-like 
projection from the ball 14 extending loosely through the throat 12. This 
releases the liquid into the timber. While the pressure in the shells 1 
and 2 is substantially greater than in the tube 10 the tube 26 is 
collapsed so that outward flow of liquid is restricted. When the pressure 
in the shells 1 and 2 is substantially equal to or less than the pressure 
in the tube 10 the tube 26 opens so as to allow unrestricted flow through 
the throat 12. Because of this the injector can be recharged with liquid 
through the tube 10. 
It will be noted that although the accumulator in FIG. 2 is not a separated 
one like in FIG. 1, it can operate in any attitude because of the tubes 26 
and 27. Furthermore, the spines 30a afford a visual means of indicating 
exhaustion of the injector since loss of pressure within the shells 1 and 
2 causes the spines 30a to close together and create a change in 
appearance. 
It is envisaged to provide the liquid for on-site refilling in a portable 
drum or the like, and to provide filling equipment comprising a small pump 
having a draw-off cylinder which can be inserted in the filler hole of the 
drum, a delivery line, a pressure gauge and a coupling piece. For filling 
large numbers of injectors a "factory fill" system is used. 
The invention may be used in impregnating timber with a liquid wood 
preservative in which case the tube 10 is externally screw-threaded for 
securing into a pre-bored hole as already described. In order to dry out 
damp timber and open interstices therein for the reception of the liquid 
wood preservative, electrically heated probes may be inserted in the 
pre-bored holes in the timber prior to the application of the injector. 
In the case of impregnating brick with a damp-proofing liquid such as 
silicone the tube 10 may incorporate an expanding collar or the like to 
provide a mechanical anchor and liquid isolation on pre-bored holes in the 
bricks. The same could be used in timber. 
Where a liquid is required to be injected from a location at predetermined 
depth in a pre-bored hole the tube 10 may incorporate two expanding 
collars or the like spaced apart longitudinally of the tube and with the 
liquid outlet disposed between the collars. Such an arrangement can be 
used to advantage in a multi-layered hull of a large timber ship. 
The liquid injectors described are both designed to impregnate substances 
exhibiting varying natural rates of liquid uptake. In the case of a 
substance with a rapid rate of liquid uptake the liquid flow is reduced to 
the design minimum close to that of the material requirement. However, in 
the case of a substance with a slow rate of liquid uptake the full 
discharge pressure is permitted to be employed deep inside the material. 
Since the injector is a closed system it can be used under water, or buried 
in sand etc. 
It has already been mentioned that both injectors described can be 
re-charged via the tube 10. This would be appropriate when the liquid 
injector is buried or is otherwise inaccessible for refilling with liquid. 
Such a case exists where the injector is installed at the base of a 
telegraph pole and buried as shown in FIG. 3 and it becomes necessary 
after a period to re-impregnate the pole with liquid. At the initial 
installation of the injector the base of the pole 33 to be buried 
ultimately, is exposed sufficiently to enable the injector to be buried 
when fitted. Preferably a protective sheath 34 is applied about the pole 
at this exposed area extending a short distance above ultimate ground 
level. A jig (not shown) is applied to the pole and two intersecting holes 
are bored into the pole, the first hole 35 extending substantially 
horizontally across the pole a little short of the other side, at a level 
below ultimate ground level and the second hole 36 being bored in a 
downwardly inclined direction from a level near to the ultimate ground 
level. The jig is then removed and the injector is installed as shown with 
the delivery tube 10 screwed into the hole 35. The hole 36 is closed off 
with a removable bung 37 and the impregnation is begun. The cavity about 
the base of the pole is infilled to the ultimate ground level so burying 
the injector. After a predetermined period of a number of years the hole 
36 is re-opened and fresh liquid is introduced under pressure from outside 
so as to backfill and re-pressurise the injector. The fresh liquid then 
begins to be introduced into the timber at a controlled rate. Finally the 
bung 37 is replaced in the hole 36. The hole 36 may also serve to receive 
a diagnostic probe to monitor the efficacy of the protective agent(s) and 
the internal condition of the timber of the pole from time to time. The 
probe may be permanently secured to the bung 37. 
The hole 35 can be bored completely through the pole so that an injector 
may be fitted to each end of the hole 35. Where more than two injectors 
are to be installed there can be bored a plurality of intersecting holes 
35. In each case, however, there is only a need for a single hole 36 for 
back-filling all the injectors and diagnostic purposes. 
The injector is designed to inject any liquid which may include nutrients 
and micro-organisms biologically tailored to protect the timber from 
bio-degradation and insect attack.