GB2074481A - Blasting lance - Google Patents

Abstract

A lance for surface-preparation shot-blasting in confined spaces, e.g. in an excavation around a service duct, has a rigid stem (1) to which is articulated a blast nozzle (6). The attitude of the nozzle relative to the stem is governed by displacement of a flexible conduit (7) by which blasting material is brought to the nozzle. The conduit (7) may be attached to a slidable handle (2) for this purpose. <IMAGE>

Description

SPECIFICATION Blasting lance This invention relates to a lance for use in surface cleaning processes in which small, more or less abrasive particles are projected forcefully onto the surface by means of a vehicle of compressed fluid, usually compressed air. For brevity, these processes will be referred to here and after as shotblasting but it is to be clearly understood that they include use of particles such as sand or grit.

The present invention is concerned to provide a hand held lance for directing the particles at the surface to be prepared, and it is intended for applications where access to the surface is restricted and difficult. The problem arises particularly and acutely in the sealing or resealing of already-laid service ducts such as gas mains, where the joints thereof may have become leaky as a result of drying out or failure of the original sealant or as a result perhaps of soil movement. Various processes have been devised for in situ sealing or encapsulation of such joints which can be carried out within very restricted access volumes (obviously it is undesirable to have to excavate large volumes around every joint).However, in many circumstances it is necessary to treat the surfaces of the duct at and immediately adjacent to the joint so that there will be efficient bonding of the sealant onto the duct surfaces, and this is usually carried out by shotblasting.

Shotblasting within a very confined access space is difficult and previously has been carried out, in this particular context, by having a lance of which the nozzle is manually moved about within the excavated cavity which requires the shutting off of the blasting during movement and (for reasons of access) the removal of the lance from the hole.

The present applicants provide by means of the present invention a shotblasting lance which allows for remote operation and orientation of a nozzle within a very constricted volume without the need of manual intervention at the nozzle and hence of temporary shut down of the blasting, and provide this in a remarkably simple construction.

In the invention there is provided a lance for surface preparation by blasting which has an elongate rigid stem to one end of which is articulated a blast nozzle, and a conduit for conveying blasting material and vehicle to the nozzle which is moveable in the direction along the stem thereby to control the attitude of the nozzle relative to the stem, about its articulation with the latter.

It can be seen that in the context of the surface preparation of service ducts such as gas mains the operative may stand at ground level by means of the stem, lower the nozzle into an excavated hole and adjust it for level and positions. Then, by altering the relationship between the conduit and the stem he can alter the angle of the nozzle relative to the stem.

In particular he will be able to more or less align the nozzle with the stem for the purpose of passing the nozzle down the side of the joint (where the cavity will be narrowest) then restore the nozzle to an acute angle to the stem to treat the under surface of the joint.

To achieve particularly reliable control of the relationship between the stem and the nozzle it is preferable to form the stem as a hollow tube with a flexible conduit for the blasting means movably freely within the tube. Even further security and control can be achieved by providing a telescopic handle for the stem which is slidable relative to the latter, but to which the conduit for blasting means is constrained.

Then, by adjusting the axial relationship between the handle and the stem the operative will alter the angle between the nozzle and the stem.

A preferred articulation is one involving a pivoting linkage spacing apart the stem and the nozzle. By this means acute angles between the nozzle and the stem can more readily be achieved and because the nozzle can be eccentric of the stem axis a "sweep" can be obtained by rotation of the stem.

A particular embodiment of the invention will now be described with reference to the accompanying drawings wherein: Figure lisa diagrammatic side view of the embodiment, Figure 2 is a diagrammatic side view of a detail, in a different position, and Figure 3 shows a modified pivoting linkage, in side view.

The embodiment shown is a lance for grit blasting of the surface of pipes adjacent to and at a joint between those pipes in a gas main, as a preliminary to the resealing of that joint from the outside by the application of a ring or encapsulation of sealant. A restricted cavity is dug down to and around the joint and the lance is to allow remote operations at the bottom of that cavity by a workman standing at ground level.

The lance therefore has a stem 1 which is of sufficient length to allow that use (in the present embodiment approximately 2 metres). The stem is in this embodiment a hollow tube having at one end a suitable grip 2 and at the other having a pivot 3 for a pair of link arms 4 which attheirotherend of articulated are hinged at 5 to a directional blasting nozzle 6.

Down the centre of the tube formed by the stem 1 there runs a flexible conduit 7 through which blasting material (abrasive particles and vehicle) are passed under pressure to the nozzle 6. The conduit 7 is not fixed axially relative to the tube of the stem 1 and it can be pushed up or down that tube. The results of that (shown by way of example in Figures 1 and 2) will be to alter the angle of the nozzle 6 relative to the axis of the stem 1 from a position where the nozzle can be more or less aligned with that stem to one where it forms a sharply acute angle (seen in Figure 2).This is enabled by the provision of the swinging linkage 4 allowing the nozzle to adopt a position laterally off-set from the axis of the stem where small variations in the length of the flexible conduit 7 projecting from the bottom and rounded end 8 of th at stem can sensitively affect the angle of the nozzle.

To ensure the smooth passage of the conduit 7 within the stem 1 a telescopic handle portion 9 is preferably provided, this also having a grip 10 like grip 2 at its end, and the conduit is secured axially to the handle. The handle is also a hollow tube within which the conduit passes, this tube being slidable telescopically within the tube of the stem 1.

Apart from the general smoothness of the operation aided by providing a handle, it also enables indicia to be marked on it indicating the probable attitude of the noule relative to the stem.

In a modified pivoting linkage 4, seen in Figures 3 and 4, a collar 11 on the end of the stem 1 has a lug 12 projecting to one side of it. A collar 13 is clamped by nutand bolt 17to the butt 14 ofthe nozzle 6, and a lug 15 projects to one side of it. The two lugs are pivotally connected at 16 by a bolt and anti-friction nut 18, with a thin washer between the lugs, so that the lugs may pivot about the axle formed by the bolt. Thus the nozzle and stem are linked for pivoted motion under the influence of the hose 7, as before, between the position seen in Figure 3 with 1800 between them and a position in which they are aligned and coaxial. The lugs 15, 12 are slightly off-set from the diametrical, as seen in Figure 4, to allow that alignment.

Figure 3 also shows how the end of the stem 1 can be flared or chamfered at 19.

It can be seen that the lances shown can be inserted into and withdrawn from cavities of very restricted dimensions and moved around in such cavities with a very considerable degree of angular, directional and elevational control without the need for cutting off the blast or any intervention within the cavity to alter any of those settings.

Claims (7)

1. A blasting lance with an elongate rigid stem, a blast nozzle movably articulated to the stem and a conduit for conveying blasting material and vehicle to the nozzle, the conduit being movable in the direction of elongation of the stem whereby to control the attitude of the noule relative to the stem.

2. A blasting lance according to claim 1 wherein the conduit is a continuous flexible pressure hose.

3. A blasting lance according to claim 1 or claim 2 wherein the stem is hollow and the conduit passes down the hollow ofthe stem.

4. A blasting lance according to any one ofthe preceding claims having additionally a handle which is movable relative to the stem in the direction of elongation of the stem and the conduit is attached to the handle to be moved with it.

5. A blasting lance according to any one ofthe preceding claims wherein the articulation of the nozzle includes a swinging linkage pivotally linked to the nozzle at one end and to the stem at the other.

6. A blasting lance according to any one of claims 1 to 4 wherein the articulation includes a lug on the nozzle and a lug on the stem, coupled by a pivot axle.

7. A blasting lance substantially as herein described with reference to and as illustrated in the accompanying drawings.