PROTECTIVE SHIELD DEVICE

Abstract: Protective shield device designed especially to enclose the working area of a cutting torch or nozzle, a welding set, a spray nozzle or like unit emitting radiation and gases, said cutting torch, nozzle or like unit, which works on a workpiece, operating within a space defined on one side, by the workpiece and, on the other side, by the hood-like protective shield, said protective shield (1) being provided with a preferably optical observation device (23). The new feature of this invention is that a chamber (34) which has a very small opening (33) directed towards the working area and for the rest is closed relative to the space below the shield, is provided between a light interception means, a lens system or like unit (24 - 27) in the observation device (23), and the working area to be observed in the space below the shield (1), and that a supply conduit for gas under pressure opens into said chamber (34).

Description: PROTECTIVE SHIELD DEVICE The present invention relates to a protective shield device designed especially to enclose the working area of a cutting torch or nozzle, a welding set, a spray nozzle or like unit emitting radiation and gases, said cutting torch, nozzle or like unit, which works on a workpiece, operating within a space defined, on one side, by the workpiece and, on the other side, by the hood-like protective shield, said protective shield being provided with a preferably optical observation device, directed towards the working area, to permit continuous control of the functions of the cutting blowpipe or like unit, the construction of said observation device being such as to permit, without opening or with¬ drawing the protective shield, the required inspection into the working area of the cutting torch or like unit, both during the cutting activity or like operation and when adjustment for this purpose is going on. It is previously known in cutting torches at cutting tables and the like to arrange hood-like shields which adjoin the workpiece, surround the cutting torch head and which are connected to an exhaust conduit, so that gas produced during the cutting operation and other airborne impurities are kept collected by means of said shields and sucked therefrom. Shields of the indicated type also screen off the radiation arising during the cutting operation. It is desirable that the shield should adjoin as efficiently as possible the surface of the workpiece being cut and have as few openings as possible. Considering the fact that it must be possible to control the function of the cutting' torch with respect to position and orientation the pro- tective shields have been provided with hinged visors. To permit control also during the cutting operation the visor or other parts of the shield have been provided with windows of dyed glass. To complete or replace protective glass windows it has been suggested to provide optical observation systems, in- eluding a lens system directed towards the working area an ' located after the lens system, mirror arrangements and/or focusing screen on which an image of the working area is displayed. 5 It has been found, however, that prior-art optical observation systems like protective glass windows will ver soon become unusable because the lens surfaces or the like facing the shield space are coated with smoke deposits and are mechanically damaged by spatter impinging the lens sur 0 face. To eliminate this disadvantage it has bee . suggested to provide air or gas nozzles directed towards the surface of the lens system to flush away deposits. However, such devices have proved to have little effect and prolong only to a small degree the periods between the required inspec- 5 tions. The object of this invention is to provide a device which ensures that the light interception means or lens system is kept free from deposits ' , '" both in the form of smo and dust, and damages due to spatter. The essential charac 0 teristic of the device according to the invention resides therein that a chamber, which has a very small opening directed towards the working area and for the rest is clos relative to the space below the shield, is provided betwee a light interception means, a lens system or like unit in the observation- device, and the working area to be observe ' "" in the space below the shield, and that a supply conduit f gas under pressure opens into said chamber in order to produce a gas flow in the opening of the chamber directed towards the space below the shield, which gas flow is di- rected towards said space, prevents smoke from passing int the chamber and deflects spatter directed towards said chamber and which also removes any impurities accumulated the opening. An embodiment of the device according to the inventio adapted to cutting torches at cutting tables, will be described more fully hereinbelow with reference to the_ accompanying drawing, in which: Fig. 1 is a cross-section of a protective shield ac- 3 cording to the invention mounted on a cutting torch and Fig. 2 is a cross-section on line I-I in Fig. 1. In the drawing, a cutting torch nozzle is designated by S, said nozzle merges in a nozzle shaft B which, in turn, is carried by an adjustable mechanism displaceable along a beam. K designates a sensing means arranged around the nozzle and included in a system for capacitive positioning of the nozzle. The protective hood-like shield, which is generally designated by 1 and is attached to the nozzle shaft B, in¬ cludes a central member 2, provided with a water chamber 3 through which cooling water circulates via conduits 4 and 5. Two tubes 6, indicated by broken lines, extend through the central member 2 and converge in a fork-like manner in a tube (not shown) connected to an exhaust conduit. An intermediate member 10 rests on the central member 2 by means of an inward flange 9 and the edge of said inter¬ mediate member, which is provide ' with a downward flange 11, supports in the same manner a peripheral member 12 which rests on the edge 11 by means of an inward flange 13. In¬ wardly of the outer downwardly extending edge flange 14 of the peripheral member and the flange 11 there is formed a downwardly open ϋ-shaped channel in which a ring 17 is movably supported by means of springs 15 and carrying pins 16. The ring 17 has a downwardly open groove 18 with a slit- shaped opening 19 which is narrower than the groove 18. Suspended in the groove are the generally spherical heads 20 of a very large number of bars 21. As the head and the rest of the bar is interconnected by a thin neck which, in cross-section, is substantially smaller than the slit- shaped opening 19 of the groove 18 the bars can sway freely. The cross-section of the bars is polygonal and preferably square and the bars form a mobile screening curtain between the edge of the peripheral member and the surface A of the workpiece. The risk of the shield being tied up by objects ex¬ tending upwardly from the workpiece is eliminated because the shield is constructed as described above. The mobile bars 21 yield in the first place. If this should be in- sufficient the peripheral member 12 may lift and turn and, finally, also the intermediate part may displace itself relative to the central part 2. Provided in the intermediate part is an opening 22. in which there is fitted an observation device 23 which, in the example shown, consists of an optical viewing apparatus including a lens system 24, a pair of angled mirrors 25 and 26 and a focusing screen 27. The light intercepting objec- tive part, of the apparatus is directed towards the working area at the end of the cutting nozzle S and the cutting torch flame will be reflected on the focusing screen 27 in the form of a magnified image. Before a cutting operation is started, a so-called pilot flame is produced and this can be watched by the nake eye without protection. When the cutting operation is star¬ ted, the light and radiation intensity increases to a very high degree and the cutting flame cannot be watched without risks. * To permit control of both the pilot flame and the cutting process the apparatus may be provided, as is shown, with a filter system which is actuable only during cutting. A simple or composite filter, designated 28, is slide- able into and out of the path of radiation towards the lens system. To obtain automatic screening when cutting is star- ted, the filter 28 is mounted in a slide 29 which is dis¬ placeable in a guide 30. The slide is connected to a pis on 31 of a pressure medium operated cylinder 32. The supply of pressure medium is controlled by means of a valve which, in turn, receives an opening impulse when the cutting cσn- trolling means is acted upon and the sucking-out operation is actuated since as a rule sucking only takes place during cutting. Thus the filter 28 runs into a screening position as soon as the cutting operation starts , and is withdrawn when cutting is interrupted. To eliminate the above-mentioned risk of the lens or objective system 24 being coated with smoke deposits or being damaged by spatter from the cutting operation there i arranged in front of the lens system a chamber 34 provided UR OM with a very small opening 33 directed towards the space be¬ low the shield 1 and the working area. A conduit opens into said chamber and through this conduit a medium under pres¬ sure, air or protective gas, is introduced into the chamber in which there will prevail a pressure which is higher than the pressure in the space below the hood-like shield 1. Gas will thus flow through the opening 33 from the chamber 34 towards the shield space and this gas flow will keep the opening free from deposits. The gas jet passing out through the opening 33 will also deflect spatter and particles moving towards the opening so as to prevent them from reaching the opening. In the chamber 34, which the lens system 24 or the filter 28 faces, there is only pure gas, free from smoke and spatter, which is a guarantee for long- lasting non-problematic service. It is obvious that the invention can be modified and further developed in various respects . Instead of one focusing screen adjacent the shield use may be made of focusing screen situated centrally on the operating site, whereby the image transmission between the light intercepting objective means in the respective shield and the focusing screen can be provided by means of fibre optics, so-called light conductors. One may also imagine observation by means of a TV-apparatus, each shield being provided with a camera member which is connected to a view¬ ing screen, suitably so arranged that-it can reflect images from all the cutting torches. A TV-camera may also be used to observe a number of focusing screens, provided each at one shield, either by means of wide-angle optics or by sweeping over the said screens. Especially in case a TV-system is utilised it is suitable to arrange means which permit a standing reference image to appear on the viewing screen. Even if the example shown illustrates the invention as applied to a gas or plasma cutting device it is obvious that the device according to the invention is applicable to an equally high degree to other operations where noxious gases and airborne particles as well as noxious radiation are ge- nerated during a working process. A shield with an observation device similar to that described above may be utilised in .welding, especially automatic welding. In that case the welding tool will re- place the cutting nozzle. Also in spraying of metal the invention will be of use for checking the working result. If a cylindrical surface is worked on, the protective shield must of course be modi¬ fied so as to adjoin the workpiece appropriately. The observation device can be modified as required. Thus, instead of flitres controlled by compressed-air im¬ pulses, one may utilise an electronic apparatus controlled by the radiation intensity to operate a filtre. Especially when a TV-system is used in the image transmission system i is of course possible to apply electronic means to control the light intensity on the viewing screen. Thus the invention should not be considered limited to that described above and shown in -the drawing but may be modified in various ways within the scope of the appended claims. O A

Claims: CLAIMS 1. A protective shield device designed especially to enclose the working area of a cutting torch or nozzle, a welding set, at spray nozzle or like unit emitting radiation and gases, said cutting nozzle or like unit, which works on a workpiece, operating within a space defined, on one side, by the workpiece and, on the other side, by the protective hood-like shield, said protective shield (1) being provided with a preferably optical observation device (23) , directed towards the working area, to permit continuous control of the functions of the cutting nozzle or like unit, the con¬ struction of said observation device being such as to per¬ mit, without opening or withdrawing the protective shield, the required inspection into the working area of the cutting nozzle or like unit, both during the cutting activity or like operation and when adjustment for this purpose is go¬ ing on, c h a r a c t e r i z e d in that a chamber (34) , which has a very small opening (33) directed towards the working area and for the rest is closed relative to the space below the shield, is provided between a light inter- ception means, a lens system or like unit (24 - 27) in the observation device (23) and the working area to be observed in the space below the shield (1) , and in that a supply conduit for gas under pressure opens into said chamber (34) to produce a gas flow in the opening (33) of the chamber directed towards the space below the shield, which gas flow is directed towards said space, prevents smoke from passing into the chamber and deflects spatter directed towards said chamber and which also removes any impurities accumulated in the opening. 2. A protective shield device as claimed in claim 1, c h a r a c t e r i z e d in that the observation de¬ vice is optical and includes a focusing screen or like means (27) on which light, which has passed through a lens system, is projected to give a properly magnified image of the working area. 3. A protective shield device as claimed in claim 1, • c h a r a c t e r i z e d in that a light conducting means extends to a viewing means from an optical intercep¬ tion means which is directed towards the region around the working area of the cutting nozzle and is provided with th required filtre system. 4. A protective shield device as claimed in claim 3, c h a r a c t e r i z e d in that the light conducting means includes a fibre light conductor and the viewing mea - includes a focusing screen. 5. A protective shield device as claimed in claim 3, c h a r a c t e r i z e d in that the interception mean includes a TV-camera and the viewing means consists of a viewing screen. 0M 1

Inventors: LINDKVIST E
Applicants: LINDKVIST E
Application year: 1981
Main classification: G02B27
IPC codes: B08B15, B23K7, B23K9, B23K31, F16P1, G02B25, G02B27