GB2131090A - Injection device - Google Patents

Abstract

An injection device e.g. for cavity wall insulation has a chamber 10 for material to be injected, e.g. polystyrene beads an inlet 20 for supplying said material to the chamber and an outlet tube 14 from which material is ejected, the outlet tube having a converging section 16 at its end adjacent the chamber such that when a jet of compressed air from a nozzle 12 debouching into the chamber is directed into the converging section material is drawn from the chamber through the outlet tube. A binder may be sprayed from a spray head 22 onto the material in the chamber. An alternative arrangement of the inlets is described (Fig. 2). <IMAGE>

Description

SPECIFICATION Improvements in or relating to injection devices The present invention concerns an improved injection device, especially but not exclusively a device for injecting insulation into the cavities of houses etc.

Cavity wall insulation comprising relatively small particles of an insulating material, for example polystyrene beads, is often inserted into wall cavities after a house has been built.

In certain instances, to bind the beads together to prevent their movement after they have been inserted into the wall, a binder, sometimes in the form of latex, is sprayed on the beads before they are injected into the cavity.

The beads are relatively difficult to handle and as they have to be inserted into the cavity through smali apertures relatively sophisticated injection devices are employed.

In the past injection devices have normally included a mixing chamber where the insulating material is coated with binder by a sprayer introducing binder into the chamber. The insulating material is drawn into the chamber by the use of compressed air and once coated with binder is injected into the cavity to be filled by an outlet tube. Arrangements of this nature have a high conumption of compressed air and it is an object of the present invention to obviate or mitigate this disadvantage.

According to the present invention there is provided an injection device comprising a chamber for material to be injected, a compressed fluid inlet in the form of a nozzle debouching into the chamber, and an outlet for fluid and material in the form of a tube, the inlet to said tube being co-axial with the outlet from said nozzle whereby compressed fluid from the nozzle passing through the restriction causes material from the chamber to be drawn through the tube.

Preferably the inlet to the tube is formed by a section which converges in the direction of fluid flow and the inclusive angle of said converging section of the tube may lie in the range 8-15". Preferably the nozzle has a single or multiple hole exit designed to give the maximum velocity to the issuing air jet and is so arranged that said jet is directed in a narrow stream down the axis of the tube.

Preferably the axis of the inlet for material to be injected by the device lies at an angle within the range 20-29" to said axis of the restriction.

The chamber may be provided with a further inlet for a binder for coating material in the chamber prior to ejection therefrom. The further inlet may be provided with a spray nozzle.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 shows a cross-section through an injection device; and Figure 2 shows a similar view of a modified device.

An injection device comprises a chamber 10 into which projects a nozzle 1 2 which is adapted for connection to a source of compressed air. The nozzle 1 2 has a single or multiple hole output which is designed to give the maximum velocity to the issuing air jet.

An outlet tube 14 leads from the chamber, the axis of the tube lying along the axis of the nozzle 1 2 which, in turn, lies at 90 to the longitudinal axis of the chamber 10. At the end of the tube 14 adjacent the chamber 10 there is provided a converging portion 16, the angle of the converging portion 1 6 lying within the range 8-15". There is a space between the end of the nozzle and the inlet to the tube 1 4 for a reason which will become evident from the following description.

The chamber 10 is provided with an inlet 20 of a relatively large diameter adapted for connection to a flexible supply duct transporting solid insulating material, normaily in the form of polystyrene beads, but alternatively in the form of mineral fibres, to the inlet 20. The axis of this inlet lies at an angle within the range 20-29" to the common axis of the nozzle and outlet tube.

A spray head 22 adapted for connection to a supply of liquid binding material is arranged in the chamber 10.

In operation compressed air supplied to the nozzle 1 2 issues in the form of a high velocity jet and projects a narrow column of air down the outlet tube 14. The relative position of the nozzle end 1 2 and the end of the outlet tube 1 4 adjacent to the chamber produces a level of vacuum which causes insulating material from the inlet tube 20 to be drawn into the chamber through the chamber and down the outlet tube 1 4. Whilst in the chamber the insulating material is coated with binder from the spray head 22.

The clearance between the end of the nozzle 1 2 and the converging end of the tube 14 is such that material can readily pass therebetween into the tube 14.

In the device shown in Fig. 2 the reference numerals used in Fig. 1 have been given to corresponding components. In this modified device the chamber 10 is arranged with its longitudinal axis substantially vertical, in the in use position, and the nozzle 1 2 and outlet 1 4 at the closed base of the chamber. As before, the nozzle axis coincides with the outlet axis although a divergence of a few degrees is feasible. The nozzle 12, which terminates just beyond the chamber wall, has a converging-diverging air passage. The gas flow through the nozzle 1 2 being supersonic, it is desirable to profile the internal surface of the nozzle to conform with the properties of, and the conditions relative to, flow of compressibly gases at supersonic speeds.The use of a converging-diverging nozzle of parabolic shape is therefore incorporated. The flow velocity in the throat of the nozzle being supersonic, it is necessary to increase the area of the nozzle exit (the diverging part) to further accelerate the gas and obtain optimum jet velocity in the output 1 4 and thus raise the level of vacuum in the chamber 10. The nozzle 1 2 has a single or multiple hole outlet which is designed to give the maximum velocity to the issuing air jet.

The spray head 22 is arranged to spray binder into the chamber 10 above the nozzle 1 2 and the inlet 22 for insulating material is provided at the upper end of the chamber, the inlet being connected to a flexible duct for transporting the insulating material to the device.

Creation of a high velocity jet converting the potential energy of the compressed air into kinetic energy and the positioning of the nozzle exit with respect to the restricted portion in the outlet tube enables this device to transfer solid material at the rate comparable with existing devices but at a reduced consumption rate of compressed air.

An additional advantage of the present invention is that the jet velocity acting directly into the converging portion of the outlet tube has the effect of breaking up agglomerated insulation material thereby reducing the possibility of blockages. This disadvantage is inherent in existing devices.

Various modifications can be made without departing from the scope of the invention, for example where the insulating material employed does not require a binder the spray head 22 may be dispensed with. The chamber may take other convenient forms. The device may be used with all solid or fibrous insulating materials and also to combine different liquids or different gases or a combination of the two. The converging portion 1 6 and the inlet to the tube 1 4 may be dispensed with so that the tube has parallel internal walls.

Claims (11)

1. An injection device comprising a chamber for material to be injected, a compressed fluid inlet in the form of a nozzle bedouching into the chamber, and an outlet for fluid and material in the form of a tube, the inlet to said tube being co-axial with the outlet from said nozzle whereby compressed fluid from the nozzle passing into the tube causes material from the chamber to be drawn through the tube.

2. A device as claimed in claim 1, in which the inlet to the tube is formed by a section which converges in the direction of fluid flow.

3. A device as claimed in claim 2, in which the inclusive angle of said converging section lies in the range 8" to 15 .

4. A device as claimed in any one of claims 1 to 3, in which the axis of the inlet for material to be injected by the device lies at an angle to the axis of the inlet to the outlet tube lying within the range 20 to 29 .

5. A device as claimed in any one of claims 1 to 3, in which the axis of the inlet for material to be injected by the device is substantially perpendicular to the axis of the inlet to the outlet tube.

6. A device as claimed in any one of the preceding claims, in which a further inlet is provided for introducing binder into the chamber.

7. A device as claimed in claim 6, in which said inlet for binder is positioned to spray binder on to material passing between the inlet for material and the outlet tube.

8. A device as claimed in any one of the preceding claims, in which the nozzle for compressed fluid is a convergent/divergent nozzle.

9. A device as claimed in any one of the preceding claims, in which the nozzle has a single outlet.

10. A device as claimed in any one of claims 1 to 8, in which the nozzle has a multiple outlet.

11. A device as claimed in any one of the preceding claims, in which the outlet tube is straight and its longitudinal axis lies on the axis of compressed fluid debouching from the nozzle.

1 2. An injection device substantially as hereinbefore described with reference to Fig.

1 or Fig. 2 of the accompanying drawings.

1 3. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.