WO1996014962A1

WO1996014962A1 - Grit-blasting installation

Info

Publication number: WO1996014962A1
Application number: PCT/NL1995/000388
Authority: WO
Inventors: Jacobus Karel Lodewijk Van Leeuwen
Original assignee: Vacblast N.V.
Priority date: 1994-11-11
Filing date: 1995-11-10
Publication date: 1996-05-23
Also published as: NL1000809A1; NL1000809C2; AU3882895A

Abstract

Grit-blasting installation, comprising a main frame (8) which is connected to drive elements (2-7) by means of which the main frame (8) is held an essentially fixed distance away from the surface to be blasted and, by which means, is movable over said surface essentially parallel thereto, and a sub-frame (24) which is fixed via guide elements (17, 21) to the main frame (8) and is movable by means of said guide elements with respect to said main frame essentially parallel to the surface to be blasted, to which sub-frame (24) a grit-blasting element (23) is attached, provided with a nozzle which can be directed towards the surface to be blasted, which nozzle can be connected via a piping system (36) to a source of compressed medium and to a source of the grit which generates the abrasive effect.

Description

Grit-blasting installation

The invention relates to a grit-blasting installation, which in particular is suitable for treating relatively large surface areas, such as the wall of a building, or the hull of, for example, an oil tanker. In particular, the invention relates to a grit-blasting installation which is suitable for effective blasting of surfaces of complex shape, such as the bow or the keel of a ship. In addition, the invention relates to a grit-blasting installation which can be operated by one person, or even can operate fully automatically, and with which environmental pollution is restricted to a minimum. As is customary, large surface areas, such as, for example, the outside wall of a block of flats, but also, for example, the legs of an offshore drilling platform or production platform, are sand-blasted by means of blasting guns which can be held by hand. The material used for the blasting grit is, for example, sand, aluminium or steel. During blasting an appreciable cloud of liberated dust and blasting grit is produced. In order to restrict environmental pollution to a minimum, a screen is arranged a few metres away from the surface to be sand-blasted. The erection and subsequent removal of such a screen is expensive. Furthermore, large amounts of blasting grit and dust are liberated, which accumulate between the screen and the surface to be blasted and subsequently have to be removed. The costs for environmentally friendly disposal of such dust and blasting sand are starting to assume astronomical proportions because of the ever more stringent environmental requirements. Furthermore, the personnel who operate the blasting guns are continually exposed to the cloud of blasting grit and dust in which they are standing, which in the long term has an adverse effect on their health. Moreover, the operation of a blasting gun is hard and heavy work, both reasons why sand-blasting of a surface demands more time than would be expected on the basis of the speed at which the blasting sand performs its cleaning action. In particular, sand-blasting of irregularly shaped surfaces, such as curved surfaces, is particularly heavy and complex because of the conditions under which the operating personnel have to work.

The aim of the present invention is so to improve the sand-blasting of a surface, in particular of an irregularly shaped surface such as a curved surface, that the abovementioned disadvantages are eliminated or at least substantially removed. To this end a grit-blasting installation corresponding to the appended Claim 1 is proposed. Surprisingly, it has been found that using a grit-blasting installation of this type it is possible to achieve results which are comparable with those of sand-blasting by means of a blasting gun which can be held by hand, or that the results are even better in comparison with the latter. On the other hand, only a relatively low level of effort in respect of the design and construction of the grit-blasting installation according to the present invention is required in order to achieve such results and, consequently, the capital investment and the costs in connection with operation and maintenance can be restricted to the minimum.

With the grit-blasting installation according to the invention, it is possible to achieve control of the sand jet over the surface to be blasted, the operator merely having to operate a control panel which can be set up a large distance away from the surface to be blasted and thus outside the area where major dust generation is caused. Compared with the operation of a blasting gun which can be held by hand, appreciably less effort is required to control the grit jet by means of the control panel, by means of which electrical, hydraulic, pneumatic or mechanical drive elements are actuated, so that the operator can be assigned to the job for a longer period, whilst his her health is better protected, so that the work can be carried out more rapidly and more safely.

The invention is based on the insight that, by the use of a main frame and a sub- frame connected thereto, to which sub-frame the jet nozzle is attached, a mechanically controllable grit-blasting system which operates reliably can be achieved at relatively low investment cost, with which system appreciable advantages can be obtained in respect of reduction of environmental pollution, reduction of physical stress on the operator and increase in the speed of work, whilst said work can also be carried out more accurately. At the same time, the possibility of fully automatic control of the grit jet over the surface to be blasted, by means of, for example, an assembly of sensors and a central electronic computer, is created by this means. Furthermore, by making use of the main frame with the sub-frame movably connected thereto, accurate guiding of the grit jet with respect to the surface to be blasted can be achieved, the jet nozzle being movable accurately over said surface to be blasted at a virtually constant distance therefrom, by which means optimum adjustment of the system can be achieved, which leads to effective cleaning in combination with the minimum possible environmental pollution while maintaining a high rate of cleaning and a low level of physical stress on the operator. Such results can be achieved in accordance with the present invention with a relatively simple construction of the grit- blasting installation.

In the case of a grit-blasting installation according to the invention, the main frame advantageously comprises at least two support points arranged some distance apart in order to keep the main frame bearing against the surface to be blasted and some distance away from the latter, and the drive elements are suitable for keeping the main frame bearing against said surface under pre-tension. Keeping the main frame bearing against the surface to be blasted in this way promotes the accuracy and the ease with which the blasting element can be moved over the surface to be blasted.

As a result of the accurate guiding of the jet nozzle relative to the surface to be blasted, it has become possible, according to a preferred embodiment of the present invention, to carry out blasting within a defined area which is virtually completely shut off from the environment, which defined area is determined by a shielding body which is mounted on the sub-frame and which closely encloses the grit jet and, tightly abutting the surface to be blasted, can be moved over said surface by sliding or rolling. As a result of the reliable guiding by means of the main frame and the sub-frame, tight abutment of said enclosure against the surface to be blasted is ensured under virtually all circumstances. Despite the relatively heavy enclosure with the requisite sealing elements, this is necessary in order to keep the unavoidable generation of dust within as small an area as possible.

The dust generated within the enclosure and the blasting grit released can be efficiently removed from said area by suction, preferably via an annular vacuum or suction slit, for transfer to, for example, a separator installation in order to separate off the grit, for re-use, from the dust, after which the dust can be disposed of in an environmentally friendly manner.

In order to obtain grit jets of as high a quality as possible, it is preferable to attach the nozzle to the sub-frame such that it can swing, so enabling the jet nozzle to perform a reciprocating movement in order to obtain a grit jet moving to and fro over the surface to be blasted. With this arrangement it is preferable to drive the jet nozzle in reciprocating fashion in one direction, such that said nozzle, together with the sub-frame, is moved in the direction virtually perpendicular thereto over the surface to be blasted. As a result of the reciprocating movement of the jet nozzle, more efficient blasting is achieved, whilst the blasting treatment is also carried out more uniformly. For the sake of simplicity of the construction and its reliable operation, it is preferable, in the case of a jet nozzle driven in reciprocating fashion, to attach the enclosure firmly to the sub-frame, the shape of the enclosure then having to be adapted such that the grit jet issuing from said jet nozzle is not impeded by the enclosure during the reciprocating movement of the jet nozzle. According to an advantageous embodiment, the grit-blasting installation further comprises a platform with a control panel for an operator, to which platfoπn the main frame is attached via a boom construction. Said platform itself can then, in turn, be fixed to, for example, a cherry picker. By arranging for the platform and the operator to be in the vicinity of the blasting element, the quality and efficiency of the blasting work can improve appreciably, since a rapid visual check is possible.

In this context blasting grit is defined as granular or particulate material with which a so-called "sand-blasting effect" can be achieved. Examples of such materials are aluminium oxide granules, glass beads, plastic beads and steel filaments. In this context, grit jet is defined as the jet of grit generated by means of compressed air or compressed gas.

In the text which follows, the invention is explained in more detail by way of example with the aid of two preferred embodiments shown in more detail in the drawing. In the drawing: Fig. 1 shows a perspective, partially exposed, view of the grit-blasting installation according to the invention;

Fig. 2 shows a- perspective view of the main frame and the sub-frame of the installation shown in Fig. 1;

Fig. 3 shows a cross-sectional side view of the assembly of injection nozzle and enclosure of the installation shown in Fig. 1;

Fig. 3a shows a front view of the elements shown in Fig. 3; Fig. 4 shows a view corresponding to Fig. 3 of an alternative assembly of injection nozzle and enclosure, partially exposed;

Fig. 4a shows a front view of the elements shown in Fig. 4; Fig. 5 shows a perspective view of a second embodiment of the grit-blasting installation according to the invention;

Fig. 6 shows a side view of the grit-blasting installation shown in Fig. 5; and Fig. 7 shows a top view of the grit-blasting installation shown in Fig. 5, with partially exposed components. The installation 1 shown in Fig. 1 comprises a jointed, telescopic arm 2 of, for example, a cherry picker. A platform 5, on which an operator is able to stand, is fixed at the end of the arm section 4 which is driven by means of the hydraulic piston/cylinder combination 3 such that it can swing. A control panel 6 is located on said platform 5. Furthermore, a boom construction 7 is fixed to the platform 5. A frame 8 is attached to said boom construction 7 such that it is pivotable about an essentially horizontal hinge line. As is shown in more detail in Fig. 2, said frame 8 has, for this purpose, stub shafts 9 which protrude sideways at its vertical side sections 10, form hinge pins and are inserted in a hole in, in each case, one lug 11 on the boom structure 7. By means of the telescopic, jointed aim 2 and by means of the pivotable mounting in the boom structure 7, the frame 8 is able to assume many angular positions, in order to follow an irregularly shaped surface, for example a surface having a single or double curvature. For example, a pressure sensor, which is connected to a control unit (not shown), is incorporated in the piston/cylinder combination 3, by means of which sensor the frame 8 can be held continuously pressed under a predetermined pre-tension against a surface.

As is shown in more detail in Fig. 2, the frame 8 consists of two vertical side sections 10, located opposite one another and some distance apart, as well as two horizontal top and bottom sections 12, located some distance apart. The sections 10, 12 are connected to one another in such a way that an essentially rectangular, preferably square, open frame is defined. In a currently advantageous embodiment, the frame has sides approximately two metres long.

At its front, said frame 8 has a stub 13 in the vicinity of each of its coiners, which stubs 13 extend forwards out of the plane of the frame 8 and are intended to rest against a surface. By means of said stubs 13, the frame 8 is held a fixed distance away from the surface. The stubs 13 can have a sliding surface or a rolling surface at their free ends, such that the frame 8 can be slid or rolled over the surface with little friction and as little risk as possible of damage to said surface against which said sliding surface or rolling surface is resting. In this variant a resiliently compressible ball 14, which is freely rotatable in all directions about its mid point, protrudes from the free front end of the stub 13. Mounting of said resiliently compressible ball 14 in the front end of the stub 13 will be clear to those skilled in the art.

A cross-member 15 is mounted on the frame 8. The cross-member 15 runs essentially parallel to the side sections 10. At each of its outer ends, the cross-member 15 has a trolley 16, which is guided by wheels 17 such that it can travel along the top and, respectively, bottom sections 12. The upper trolley 16 in Fig. 2 is drivably coupled to an endless belt 18 which is guided in a loop and in its turn is drivably coupled to a pneumatic piston/cylinder unit 19. By this means the cross-member 15 is movably driven to and fro in the direction of the arrow A parallel to the sections 12 so as to move essentially parallel to the surface against which the frame 8 is resting by means of its stubs 13. Of course, any other type of drive can be chosen for moving the cross-member 15 to and fro. Instead of the trolleys 16, it is, of course, also possible to choose any other type of sliding or roller guide for the cross-member 15 along the sections 12.

A sub-frame 20 is mounted on the cross-member 15. Guide wheels 21 fixed to said sub-frame 20 are movably guided on either side of the longitudinal edges of the cross- member 15, by which means the sub-frame 20 is movable to and fro essentially parallel to the longitudinal direction of the cross-member 15 in the direction of the arrow B. In the same way as in the case of the cross-member 15, the sub-frame 20 is movably driven to and fro by means of a piston/cylinder combination 22, which, in a manner which is not shown in more detail, drives an endless belt (not shown) guided in a loop and the sub- frame 20 connected thereto. Of course, here also any other type of drive is usable.

A jet pipe 23 is mounted in the sub-frame 20. Said jet pipe 23 is shown in more detail in Fig. 3 and a more detailed description thereof is given further below. A frame 24, which is movable to and fro with respect to the sub-frame 20 in the direαion of the arrow C, that is to say in a direction essentially perpendicular to the plane defined by the frame 8, is mounted on the sub-frame 20 for mounting of the jet pipe 23. To provide said movability of the frame 24, the sub-frame 20 has a cross-member section 26, the longitudinal direαion of which runs parallel to the direαion of the arrow C. At the upper and lower longitudinal edges of said cross-member section 26, which edges are located opposite one another, rotary guide wheels 25, connected to the frame 24, are guided to provide the to and fro movability of the frame 24. The to and fro drive of the frame 24 is achieved by means of a pneumatic piston/cylinder unit 27 of relatively limited stroke (preferably about twenty centimetres), only part of which can be seen here. By means of said piston/cylinder unit 27 it is possible to keep the jet pipe 23 resiliently bearing against the surface, against which the frame 8 also bears, whilst the jet pipe 23 is also capable of following changes in contour in said surface under resilient pre -tension. Of course, the pre-tensioning function of the piston/cylinder unit 27 can also be achieved by means of, for example, a mechanical spring or another element.

A pin 28 extends from the top and bottom of the jet pipe 23, which pin 28 is conneαed, such that it is rotatable about its longitudinal axis, with, in each case, one end region of one leg of the essentially U-shaped frame 24. By this means the jet pipe 23 can swing with respect to the sub-frame 20 about a hinge line which runs essentially parallel to the longitudinal direαion of the side sections 10 of the frame 8 and the cross-member 15. Said fixing of the jet pipe 23 such that it can swing further enables the position of the jet pipe 23 to be adapted to the local shape of the surface against which the frame 8 bears. Thus, the jet pipe 23 is efficiently and rapidly movable by means of the sub-frame

20 and the frame 8, via guides 17 and 21, over a surface against which the frame 8 is kept bearing. By means of the guide 25 and, where appropriate, the pivotable mounting of the jet pipe 23 in the frame 24, the jet pipe 23 is also capable of reliably following local changes in shape of the surface against which the frame 8 is bearing. Because the frame 8 is conneαed to a jointed arm, the angular positions of the joints of which are adjustable, whilst the frame 8 is pivotably mounted in a boom structure 7, the frame 8 is capable of following a surface which has a single or double curvature.

The operator, standing on the platform 5, is now able, by means of the control panel 6, to effect remote control of the various movements of the frame 8 on the one hand and of the jet pipe 23 on the other hand. With this arrangement, the procedure followed is as follows: by operating the jointed arm 2, the frame 8 is placed against a pre-seleαed area of a surface to be blasted, for example an area of the surface of the hull of a freighter with substantial fouling. As soon as the frame 8 has been brought into position, the operator will move the jet pipe 23 in the direction of the arrows A and B, during which operation the jet pipe 23 is continually kept, by the piston/cylinder unit 27, pressed against the surface to be blasted. Because the jet pipe 23 is movable with respect to the frame 8, which can be kept reliably bearing against the surface to be treated, control of the jet pipe 23 can be carried out accurately and efficiently. It will be clear that it is preferable to hold the frame 8 against the surface under a pre-stressing force which is greater than the force with which the jet pipe 23 is kept pressed against the surface by means of the piston/cylinder unit 27. The frame 8 is then moved to a different area of the surface, after which the jet pipe 23 is again moved over the surface area, with the frame 8 essentially stationary. If the surface area to be blasted is greater than the surface area enclosed within the frame 8, it is also possible to move the frame 8 over the surface area while, at the same time, moving the jet pipe 23 within the frame 8. However, this method of working demands a greater level of skill on the part of the operator.

Fig. 3 shows the construction of the jet pipe 23 in more detail. As is shown, said jet pipe 23 consists of an outer jacket 29 and an inner pipe 30, which between them define an annular suαion slit 31, which has a width of a few millimetres. At its mouth, the jacket 29 has an arc-shaped sealing element 32 which is suitable for resting resiliently against the surface 33 to be treated, in order to interaα therewith to produce a seal. The inner pipe 30 terminates a considerable distance away from the surface 33 to be treated, this distance in praαice being a few tens of centimetres. Furthermore, four supports 34 arranged in the shape of a star (see Fig. 2) are fitted to the enclosure 29, which supports 34 carry rollers 35, by means of which the jet pipe 23 can be rolled over the surface 33 to be treated and the seal 32 is subjected to as little mechanical stress as possible in order to restrict wear thereof to a minimum. A feed line 36, by means of which the granular material and compressed air for the production of a grit jet or sand jet are fed, opens into the inner pipe 30. The cloud of dust and grit which forms in the space 37 between the mouth of the jacket 29 and the surface 33 to be treated, enclosed within the seal 32, is removed via the suαion slit 31 for, for example, filtering and recovery of the blasting grit.

Fig. 4 shows a variant for the jet pipe 23. In this case use is made of a jet nozzle 38 which moves in reciprocating fashion and by means of which a larger surface can be blasted with the jet pipe 23 stationary. For this purpose, the nozzle 38 is hingeably driven such that it is rotatable about the shaft 39 running perpendicular to the plane of the drawing. For example, the jet nozzle 38 is swung to and fro at a fixed frequency between its outermost positions indicated by the continuous arrow and the arrow indicated by a broken line. At the same time, the jet pipe 23 can be moved inside the frame 8 in the manner described above.

Those components of the variant of the invention shown in Figs. 5-7 which have a function which corresponds to the function of the components of the grit-blasting installation from Figs. 1 and 2 bear a corresponding reference. Figs. 5-7 also show how the guide sleeves 21 on the sub-frame 20 are slidably guided over guide rods 40 inserted through said sub-frame, the ends of which guide rods 40 are fixed between the prongs of the essentially fork-shaped cross-member 15. The sub-frame 20 is thus movable to and fro in the direαion of the arrow B by means of a belt drive 41 (see Fig. 7). A pliable electrical supply rail 42 runs to the respective pneumatic drives for the belts 18 and 41. The frame 8 can be rotated about the hinge 9 with respect to the boom structure 7 by means of a pneumatic rotary cylinder 43. The frame 8 now consists of two essentially U-shaped elements which are arranged some distance apart and between which the cross-member 15, which is likewise essentially U-shaped, or fork-shaped, is movable to and fro. Each U-shaped element of the frame 8 has two legs 44, which are located opposite one another some distance apart and which run essentially parallel to the direαion C in which the jet pipe 23 is movable to and fro. Said two sections 44 are conneαed to one another by means of a section 10, which runs essentially parallel to the direαion B in which the sub-frame 20 is movable to and fro. Guide sleeves 17 are also located on the cross-member element 15, through which guide sleeves two rods 12 running some distance apart and essentially parallel to one another are inserted for the sliding to and fro movement of the cross- member element 15 in the direαion of the arrow A. Although in this embodiment the jet pipe 23 is fixed to the sub-frame 20 such that it can not swing, it is now also again possible to eleα for fixing of the jet pipe 23 to the sub-frame 20 such that said jet pipe 23 can swing in the direαion of the arrow D (in the plane of the drawing in Fig. 6).

The embodiment shown in Figs. 5-7 makes it possible for the jet pipe 23 to be movable outside the region which is enclosed within the bearing points 13. An embodiment of this type is particularly suitable for the treatment of relatively small surfaces, which may not be readily accessible. Of course, with this embodiment it is also possible to use, for example, roller guides, such as are used in the embodiment according to Figs. 1 and 2, in place of the slide guides with the sleeve elements 17, 21 and 25. Other combinations of components from the respective alternative embodiments according to Figs. 1 and 2 and, respectively, 5-7 will also be clear to a person skilled in the art. Of course, variants on the embodiments described and shown here are also conceivable, which variants likewise belong to the essence of the invention. For example, the method of supporting the jet pipe 23 and its seal with respect to the surface 33 to be treated can be produced in other ways. When large, essentially flat surfaces are to be blasted, it would also be possible, for example, to guide the boom structure 7 slidably or movably along a fixed rail or other guide element, so that there is then no need for a jointed arm. In combination with a rail or sets of rails of this type over which the boom structure 7 is guided, the frame 8 could be rigidly mounted in the boom structure 7. By this means it is possible to guide the frame 8, by means of guiding the boom structure 7, at a reliable, essentially constant distance from the surface 33 to be treated, as a result of which there is no further need to keep the frame 8 pressed, via the spacer stubs 13, against the surface 33 to be treated.

Claims

1. Grit-blasting installation, comprising a main frame which is conneαed to drive elements by means of which the main frame is held an essentially fixed distance away from the surface to be blasted and, by which means, is movable over said surface essentially parallel thereto, and a sub-frame which is fixed via guide elements to the main frame and is movable by means of said guide elements with respect to said main frame essentially parallel to the surface to be blasted, to which sub-frame a grit-blasting element is attached, provided with a nozzle which can be directed towards the surface to be blasted, which nozzle can be conneαed via a piping system to a source of compressed medium and the grit which generates the abrasive effeα.

2. Grit-blasting installation according to Claim 1, wherein the main frame is a frame within which the sub-frame is mounted and is movable.

3. Grit-blasting installation according to Claim 2, wherein the sub-frame is conneαed to a section and is movable over said section parallel thereto, which section is fixed to the frame such that it is movable transversely to its longitudinal direαion.

4. Grit-blasting installation according to one of the preceding claims, wherein the main frame has at least two bearing points arranged some distance apart in order to keep the main frame bearing against the surface to be blasted and some distance away from the latter, and wherein the drive elements are suitable for keeping the main frame bearing against said surface under pre-tension.

5. Grit-blasting installation according to one of the preceding claims, wherein the drive elements comprise a jointed arm which is conneαed to a control installation for bringing and holding the various arm joints into various angular positions with respect to one another.

6. Grit-blasting installation according to one of the preceding claims, wherein the grit-blasting element comprises a pipe element which at its one outer end carries a sealing element arranged around its peripheral edge for essentially medium-tight sealing interaαion with the surface to be blasted, whilst the nozzle opens into its opposite outer end region.

7. Grit-blasting installation according to Claim 6, wherein the pipe element is conneαed to pre-tensioning elements to keep the pipe element pressed, by its sealing elements, against the surface to be blasted.

8. Grit-blasting installation according to Claim 7, wherein the pipe element is surrounded, on the side where the sealing elements are located, by guide elements for reliable or slidable guiding over the surface to be blasted.

9. Grit-blasting installation according to one of the preceding Claims 6 to 8, wherein the nozzle is pivotable with respect to the pipe element and is drivably coupled to a reciprocating mechanism for generating a grit jet moving to and fro over the surface to be blasted.

10. Grit-blasting installation according to one of the preceding Claims 6 to 9, wherein the pipe element is surrounded, a relatively short distance away, essentially concentrically by a jacket element in order to delimit between them an annular suαion slit which surrounds the pipe element and which at one end is in fluid conneαion with the region surrounded by the sealing elements on the pipe element and at the other end is in fluid connection with a suction device, in order to remove the blasting grit, blown against the surface to be blasted, together with the dust, dirt and the like liberated by said blasting grit, within a closed circuit to a treatment unit.

11. Grit-blasting installation according to one of the preceding Claims 6 to 10, wherein the pipe element gradually widens from the nozzle.

12. Grit-blasting installation according to one of the preceding claims, wherein the grit-blasting element is mounted on the sub-frame in such a way that said sub-frame is movable to outside the region defined by the said bearing points on the main frame.