GB2425497A

GB2425497A - Nozzle with rotating cap portion

Info

Publication number: GB2425497A
Application number: GB0608218A
Authority: GB
Inventors: Nigel Richard Farrow; Michael James George Ratzer
Original assignee: Farrow System Ltd
Current assignee: Farrow System Ltd
Priority date: 2005-04-28
Filing date: 2006-04-26
Publication date: 2006-11-01
Also published as: GB0608218D0

Abstract

A nozzle 10 for use in wet or dry blasting, the nozzle includes, an inlet, though which a blast medium is forced and a tubular shaft 14 rotatably mounted and connecting the inlet to the internal volume of a nozzle cap 15 said nozzle cap 15 being mounted to and rotatable with the shaft 14 about a common axis. Nozzle cap further including one or more first outlets 30A,30B orientated substantially tangentially to the rotational axis of the shaft, the or each first outlet connecting the internal volume of the nozzle cap 15 with the exterior to allow blast medium to exit the nozzle, said exiting process providing a torque force to the nozzle cap causing the nozzle cap to rotate. Also included are one or more second outlets 31 connecting the internal volume of the nozzle cap with the exterior the orientation of said the or each second outlet having both a component non-parallel to and parallel to the rotational axis of the shaft. An air-cleaning arrangement (50,51 of fig 5) may also be included to avoid mineral build up. Also disclosed is a method of cleaning the internal surface of a tubular pipe structure.

Description

AN IMPROVED NOZZLE

Field of the Invention

The present invention relates to an improved nozzle for use in blast cleaning methods. The nozzle can be used in both wet and dry blasting processes and is particularly suitable for use in blasting the inside of a pipe or other tubular structure.

Background to the Invention

It is well known in the art to clean the surfaces of structures by means of the methods known as wet (often referred to as slurry) or dry blasting. Such methods are used for example to remove paints or other protective coatings or to remove surface deposits such as grime or biological growth. Traditionally the methods have been used to clean the harder elements made perhaps of brick, concrete or steel - of buildings or other large structures, but in recent years the sphere of use has expanded to take in graffiti removal and the cleaning of more easily damaged items, such as furniture or those made from glass reinforced polymer.

In summary, a particulate material is entrained and carried in a stream of, usually, air, water or mixture thereof and impacted against the surface to be cleaned. The impact of the stream of entrained material removes surface coatings andlor deposits in a controlled manner. By careful selection of parameters such as the particulate solid used, its particle size, the pressure applied, the fluid carrier or the temperature, the speed and sensitivity of removal can be tailored to suit the specific need. Once the parameters have been selected, the stream is directed in an appropriate fashion against the coating to remove the required amount of material.

Even where the parameters have been correctly selected, there still remains the difficulty of bringing the stream against the surface. Normally the direction of the stream is controlled by means of a nozzle, held by an operator and directed manually in order to most effectively carry out the cleaning. There are however many situations in which this is not possible: for example where the area to be cleaned is difficult to access. One application of particular relevance to the current invention, where difficulties are experienced, is the cleaning of the internal surface of a pipe, and especially a pipe used to convey water.

Over time, the internal surfaces of domestic water pipes, for example, become covered in mineral deposit; the nature of the deposit depends to a large extent on the geographical area in which the pipe is laid. For example, in some areas the deposit is relatively soft, being formed of fine particulate silica. In others it is quite hard especially where the water being carried contains large amounts of calcium, magnesium or iron. Removal of the latter type of deposit is made more difficult due to the tendency to bind both physically and chemically to the internal surface of the pipe.

Conventional mechanical methods of removing such deposits are not efficient and often result in pipe sections being broken and having to be replaced. In order to replace a broken section of pipe it needs to be dug out of the ground, a process which is both time consuming and expensive. The use of a high pressure water jet has been tried but this can again result in a broken pipe and moreover requires a high volume of water which is inconvenient and can leave the immediate area unworkable until the water has drained away.

It is an object of the present invention therefore to provide a nozzle which enables the internal surface of a pipe to be cleaned more effectively.

It is a further object of the present invention to provide a nozzle cap to address the above difficulties.

It is yet a further object of the invention to provide an improved method of cleaning, for example, a sewage,waste or water pipe.

Summary of the Invention

According to a first aspect of the invention there is provided a nozzle, for use in wet or dry blasting, the nozzle including: an inlet, through which a blast medium is forced; a tubular shaft, rotatably mounted and connecting the inlet to the internal volume of a nozzle cap, said nozzle cap being mounted to and rotatable with the shaft about a common axis; the nozzle cap further including one or more first outlets orientated substantially tangentially to the rotational axis of the shaft, the or each first outlet connecting the internal volume of the nozzle cap with the exterior to allow blast medium to exit the nozzle, said exiting process providing a torque force to the nozzle cap causing the nozzle cap to rotate; one or more second outlets connecting the internal volume of the nozzle cap with the exterior the orientation of said the or each second outlet having both a component non-parallel to and parallel to the rotational axis of the shaft. The blast medium forced into the nozzle thereby causes the nozzle cap to rotate resulting in the blast medium exiting from the or each second outlet to provide an annulus of cleaning. As the nozzle moves along the pipe therefore, the internal surface of a pipe or other tubular structure is progressively cleaned.

Preferably, the nozzle cap comprises two first outlets diametrically opposite each other. Such an orientation provides efficient thrust to rotate the nozzle whilst minimising the reduction in blasting through the or each second outlet.

Preferably, the or each second outlet is orientated at an angle of 1 - 500 to the rotational axis of the shaft. Advantageously, the or each second outlet is so orientated that the axis of the second outlet does not intersect the rotational axis of the shaft. The or each second outlet imparts thereby, torque to the nozzle cap.

Optionally said torque, imparted by one or more second outlet opposes the torque imparted by the or each first outlet. The rotational speed of the nozzle cap can be therefore limited.

The nozzle preferably comprises tubular inserts engageable with the first and second outlets to further direct the blast medium. The inserts provide these by an element which is easily replaceable to minimise wear on the nozzle cap and consequently the requirement for it to be replaced in its entirety.

Advantageously, the nozzle is provided with a second pressurised air supply, the second supply being channelled out of the or each first outlets tangential to the rotational axis of the shaft whilst the blast medium is directed out of the or each second outlet.

The nozzle preferably includes a sensor to determine the rotational speed of the nozzle cap. The operator is therefore able to receive information as to whether there is a problem with the cleaning process even when the nozzle is not visible to the operator.

Preferably the nozzle includes gearing to enable the operator to control the rotational speed of the nozzle cap.

According to a second aspect of the invention there is provided a nozzle including a nozzle cap having an outlet connecting the internal volume of the nozzle cap with the exterior to enable a blast medium forced into the internal volume to exit the nozzle cap, the nozzle cap being fixedly mounted to and rotatable about a common axis with a tubular shaft, the nozzle further including drive means to rotate the shaft. The drive means is preferably an electric motor, adjustable to drive the shaft at the required angular velocity. Alternatively, the drive means is an airturbine or a hydraulic motor.

According to a third aspect of the invention there is provided a nozzle cap, mountable to a rotatable shaft, the nozzle cap including an outlet connecting the internal volume of the nozzle cap with the exterior to enable blast medium to exit the nozzle cap, the outlet being oriented at an oblique angle to the axis of the nozzle cap. Preferably, the nozzle cap includes one or more further outlets orientated substantially tangentially to the axis of the nozzle cap, the or each further outlet connecting the internal volume of the nozzle cap with the exterior to allow blast medium to exit the nozzle cap and provide a torque force to the nozzle cap about the axis of the nozzle cap.

According to a fourth aspect of the invention there is provided a method of cleaning the internal surface of a tubular structure, said method including the steps of: (i) providing a nozzle, said nozzle having an inlet to allow pressurised blast medium to enter its internal volume, and further having a rotatably mounted nozzle outlet, operably connecting the internal volume of the nozzle to the exterior to provide a jet of blast medium describing an annulus; (ii) inserting the nozzle into a tubular structure to be cleaned; (iii) forcing blast medium through the nozzle to impact an annular region of the internal surface of the tubular structure; (iv) moving the nozzle progressively in a direction along the axis of the tubular structure, to clean along the length of the tubular structure.

Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings which show by way of example only, one embodiment of a blasting nozzle. In the drawings: Figure 1 is a sectional view through a nozzle assembly; Figure 2 is a side illustration of a nozzle cap; Figure 3 is a top view of a nozzle cap of Figure 2; Figure 4 is an exploded view of the nozzle coupling to an inlet hose; and Figure 5 is a further, partial, sectional view through a further embodiment of nozzle coupling.

Detailed Description of the Invention

A nozzle assembly 10 shown in Figure 1 is suitable for cleaning the internal surface of a tubular structure. The assembly 10 is normally attached to the end of a blast hose of conventional type. The hose typically conveys a blast mixture of, a particulate solid in a carrier gas - usually air - and also often a liquid - most usually water. The blast mixture is forced under pressure from a standard blast pot to the nozzle assembly 10 pressure being supplied from compressed air.

Usually the blast mixture is subject to an applied pressure of up to 10 bar, although pressures above this range can be used where required. In the case of higher pressures suitable safety provisions should be in place. Moreover, if required, heating can be applied to the liquid to ensure that the temperature of the liquid in the blast pot is above 25C. The blast mixture exits the nozzle assembly through one or more outlets in the nozzle assembly. The or each outlet is rotatably mounted about an axis and rotates during delivery of the blast mixture.

The jet of blast mixture exiting an outlet describes therefore an annulus as the jet impacts against the inner surface of the tubular structure. The entire 360 of the tubular structure's inner surface is thereby subjected to the cleaning action of the blast mixture.

In more detail, the blast hose (not illustrated) is connected via a screwthreaded mounting 11 (Figure 5) incorporated into an inlet manifold 12. The inlet manifold 12 itself opens into the first end of a rotatable spindle 13. The spindle 13 includes a tubular shaft 14 along its longitudinal axis, the shaft 14 opening out at a second end into the internal volume of a nozzle cap 15. The nozzle cap 15 is fixedly mounted by means of a support platform 1 4A around the outside of the second end of the shaft 14 to the second end of the spindle 13 and thereby rotates with the spindle 13.

In order to enable the spindle / nozzle cap assembly to rotate freely the spindle 13 is mounted inside two roller bearings 1 6A, I 6B, held at a spaced distance from each other by a bearing spacer 17. The roller bearings 1 6A, 1 6B and the bearing spacer 17 are mounted within a housing 18 to provide a robust unit.

The rotatable functionality provided to the nozzle cap 15 enables a circular cleaning action to be carried out. To effect this action, the nozzle cap 15 illustrated in the drawings has three nozzle outlets to enable the blast medium forced into the nozzle cap's internal volume to exit in directed streams. Two of the nozzle outlets 30A, 30B, having a diameter of approximately 6mm, are orientated perpendicularly to the axis of the spindle 13 and in a direction tangential to the circumference of the nozzle cap 15. As blast medium exits via these outlets therefore, a torque is imparted to the nozzle cap 15. Force imparted to the nozzle cap 15, and thereby to the spindle 13, is balanced as the outlets 30A, 30B are located on opposite sides of the nozzle cap 15. The third nozzle outlet 31 is located in the outward facing end surface 32, and is orientated at an oblique angle to the axis of the spindle.

The angle at which the third nozzle outlet is set is dependant upon its radial distance from the central axis of the spindle. Where the outlet is relatively close to said axis, the angle made is largest at around 40 50 . However, where the outlet is further from the axis then the angle can be shallower at around 1 - 10 , typically 5 . The offset from the axis and the shallower angle enables the blast medium to impact the material to be removed at an angle more suited to its removal.

In Figure 5, the details of the inlet to the nozzle assembly can be seen. The exit port 53 of the inlet manifold does not engage the first end of the tubular shaft 14.

It has been found that, due to the pressure distribution within the assembly, only a small amount of grit enters the passageway 54 between the exit port 53 and the tubular shaft 14. However, a purge system is provided which ensures that grit which does penetrate this passageway is carried away.

The purge is accomplished through the use of a separate air line which forces a jet of air through an inlet aperture 50 (dotted line) in the inlet manifold 12. The air is then forced through the further inlet 51 (dotted line), through the housing 18 and the bearing ejector block 52. A positive pressure is thereby produced and air flows in the direction indicated by the Arrow B. In use therefore, the nozzle cap 15 is placed into the open end of a pipe to be cleaned a blast medium is selected having the majority of particles of a nominal particle size 80-210 micron, although material with a particle size of 90 - 1000t can be used if required by the particular use. The nature of the blast medium is determined by the type of work being undertaken and can be selected from those known in the art. Blast medium is forced down the hose along the tubular shaft 14 in the direction indicated by Arrow A and into the nozzle cap 15. In order to provide the force a compressor operating at around l7OCfm is used. Medium exiting the outlets 30A, 30B causes the nozzle cap to rotate. The medium exiting the obliquely orientated nozzle outlet thereby describes a substantially circular path. When therefore, the medium is directed against the interior surface of the pipe the entire 360 of the surface is cleaned by impact from the blast medium.

As the assembly moves along the inside of the pipe, the inner surface is progressively and uniformly cleaned along its length. In addition to the above cleaning action, any coating not removed due to the oblique nozzle outlet, will also be eventually impacted by the medium exiting the tangential nozzle outlets.

In the above described embodiment, the outlets 30A, 30B are of tubular form and are replaceable. In view of the fact that these elements are subject to a large amount of wear, it is expected that the outlets 30A, 30B will need to be replaced at frequent intervals. The replaceability of the outlets means therefore that there is no need to replace the whole nozzle cap when an outlet wears out. The outlets are held in place in the nozzle cap by conventional means. It will however be recognised that the outlets can be integral with the nozzle cap without detracting from the efficient cleaning afforded by the invention.

The nozzle cap can include means to effect mechanical removal of material from the internal surface of the pipe. For example a scraper blade, rotating with the nozzle can dislodge or partially break up the material either prior to or in conjunction with the impact of the blast medium against the material.

In an alternative embodiment, not illustrated, the spindle is connected to and its rotation driven by, for example, an electric motor or an airturbine. In this embodiment, the tangential nozzle outlets can be dispensed with. The blast medium therefore passes solely out of the remaining forward facing nozzle outlet.

One result of this, is that the energy of the blast medium exiting the nozzle assembly is concentrated out of the one nozzle with consequentially a smaller loss of cleaning force per unit of applied pressure. However, where useful the nozzle cap can include a plurality of forward facing nozzle outlets.

The use of an electric motor enables the speed of rotation to be controlled without recourse to varying the blast pressure. This would obviously be advantageous in that the operator may not wish to, for example, lower the blast pressure to bring the speed of rotation down.

However, as an alternative to such independent rotation means of controlling the rotational speed, the forward facing outlet can be orientated such that the rotational torque which the blast medium provides upon exit from said nozzle is opposed to the torque imparted by the purely tangential nozzles. In this fashion, the rotational speed of the nozzle cap can be reduced.

As a further alternative one or more blocking means can be applied to the outlets to restrict or stop the flow of blast medium through an outlet, thereby reducing the torque imparted to the nozzle cap.

In order to control the rotational speed of the nozzle cap, the nozzle can be provided with two air supply systems. The first system supplies air to the tangential outlets whilst the second is the conventional supply described above as part of the blast medium. The operator is therefore more easily able to control the nozzle cap.

In order to provide further control of the rotational speed of the nozzle cap, a gearing system controllable by the operator can be included to enable the cap to rotate at faster or slower speeds, irrespective of the pressure of the blast medium.

To assist the user, a sensor is included within the nozzle assembly to determine the rotational speed of the nozzle cap. The operator knows thereby whether the assembly has encountered a problem and the cap is not rotating freely. Such would otherwise be difficult to determine, when the assembly is within, for example an underground pipe.

In order to move the nozzle assembly along the length of the pipe, a number of means can be employed. For example, the assembly can be mounted on three skids positioned around the circumference at 120 intervals to maintain the assembly approximately centrally. Alternatively, the assembly can be mounted on a chassis supported on wheels which chassis supports the assembly at a height approximately along the longitudinal axis of the pipe. As a further example, the chassis can be mounted on a walker system or be supported on an air cushion.

The air cushion can be derived from the air supply used to force the blast medium along the pipe.

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible with the scope of the appended claims. -Il-

Claims

Claims 1. A nozzle, for use in wet or dry blasting, the nozzle including:

an inlet, through which a blast medium is forced; a tubular shaft, rotatably mounted and connecting the inlet to the internal volume of a nozzle cap, said nozzle cap being mounted to and rotatable with the shaft about a common axis; the nozzle cap further including one or more first outlets orientated substantially tangentially to the rotational axis of the shaft, the or each first outlet connecting the internal volume of the nozzle cap with the exterior to allow blast medium to exit the nozzle, said exiting process providing a torque force to the nozzle cap causing the nozzle cap to rotate; one or more second outlets connecting the internal volume of the nozzle cap with the exterior; the orientation of said the or each second outlet having both a component non-parallel to and parallel to the rotational axis of the shaft.
2. A nozzle according to Claim 1, wherein the nozzle cap comprises two first outlets diametrically opposite each other.
3. A nozzle according to Claim I or 2, wherein, the or each second outlet is orientated at an angle of I - 500 to the rotational axis of the shaft.
4. A nozzle according to any preceding claim, wherein the or each second outlet is so orientated that the axis of the second outlet does not intersect the rotational axis of the shaft.
5. A nozzle according to Claim 4, wherein said torque, imparted by one or more second outlets opposes the torque imparted by the or each first outlet.
6. A nozzle according to any preceding claim, wherein the nozzle comprises tubular inserts engageable with the first and second outlets to further direct the blast medium.
7. A nozzle according to any preceding claim, wherein the nozzle is provided with a second pressurised air supply, the second supply being channelled out of the or each first outlets tangential to the rotational axis of the shaft whilst the blast medium is directed out of the or each second outlet.
8. A nozzle according to any preceding claim, wherein, the nozzle includes a sensor to determine the rotational speed of the nozzle cap.
9. A nozzle according to any preceding claim, wherein the nozzle includes gearing to control the rotational speed of the nozzle cap.
10. A nozzle comprising a nozzle cap having an outlet connecting the internal volume of the nozzle cap with the exterior to enable a blast medium forced into the internal volume to exit the nozzle cap, the nozzle cap being fixedly mounted to and rotatable about a common axis with a tubular shaft, the nozzle further including drive means to rotate the shaft.
11. A nozzle according to claim 10, wherein the drive means is an electric motor.
12. A nozzle according to claim 10, wherein the drive means is an airturbine.
13. A nozzle according to claim 10, wherein the drive means is a hydraulic motor.
14. A nozzle cap, mountable to a rotatable shaft, the nozzle cap including an outlet connecting the internal volume of the nozzle cap with the exterior to enable blast medium to exit the nozzle cap, the outlet being oriented at an oblique angle to the axis of the nozzle cap.
15. A nozzle cap according to claim 14 comprising one or more further outlets orientated substantially tangentially to the axis of the nozzle cap, the or each further outlet connecting the internal volume of the nozzle cap with the exterior to allow blast medium to exit the nozzle cap and provide a torque force to the nozzle cap about the axis of the nozzle cap.
16. A method of cleaning the internal surface of a tubular structure, said method including the steps of: (i) providing a nozzle, said nozzle having an inlet to allow pressurised blast medium to enter its internal volume, and further having a rotatably mounted nozzle outlet, operably connecting the internal volume of the nozzle to the exterior to provide a jet of blast medium describing an annulus; (ii) inserting the nozzle into a tubular structure to be cleaned; (iii) forcing blast medium through the nozzle to impact an annular region of the internal surface of the tubular structure; (iv) moving the nozzle progressively in a direction along the axis of the tubular structure, to clean along the length of the tubular structure.
17. A nozzle substantially as herein described with reference to the accompanying drawings.
18. A nozzle cap substantially as herein described with reference to the accompanying drawings.