WO2008035238A1

WO2008035238A1 - Mixing valve for portable sandblasting machines

Info

Publication number: WO2008035238A1
Application number: PCT/IB2007/051816
Authority: WO
Inventors: Susanna Giovannini
Original assignee: Ibix S.R.L.
Priority date: 2006-09-18
Filing date: 2007-05-14
Publication date: 2008-03-27
Also published as: ITRA20060056A1

Abstract

The claimed valve, here illustrated in a longitudinal section and while the sandblasting machine is working, substantially consists of a body (1) that, being suited to the fastening of the nozzle (3) on which to fix the flexible rubber hose carrying the spray gun on its opposite end, is entirely longitudinally crossed by a mixing chamber having the inlet (4) of the compressed air in a first area with larger diameter (2A) and the inlet (5) of the abrasive particles in a second area (2B), coaxial to the first one. Inside the said chamber (2A, 2B) there is the cut-off (6) composed of two coaxial parts (6A) and (6B) with different diameter, being the first (6A) constrained to the said mechanical or pneumatic means suited to the closing movement and the second one (6B), with smaller diameter, to the first one through a connecting pin (7) serving as spring-holder for the cylindrical coil spring (8) serving to reciprocally space the said two parts (6A) and (6B) of the cut-off in closure position.

Description

Description MIXING VALVE FOR PORTABLE SANDBLASTING

MACHINES

Technical Field

[1] The present invention relates, in particular, to a mixing valve for portable dry sandblasting machines. Background Art

[2] It is known that sandblasting is a finishing and cleaning operation consisting in projecting a jet of abrasive particles, for instance quartz sand, metal grit, etc, at high speed against the surface of metal or non-metal pieces.

[3] Basically two types of sandblasting are known: the dry sandblasting, which consists in the emission of the abrasive particles through compressed air, and the hydro- sandblasting, which consists in the emission of the above-mentioned abrasive particles through a jet of pressure water having the aim to abate the big amount of very fine dusts produced by the crumbling of the above-mentioned abrasive particles in the collision with the surface of the pieces to treat.

[4] In the known machines and the devices currently on the market, the stop of the sandblasting apparatus, obtained releasing the trigger of the jet spraying gun, does not prevent the residual compressed air remained in the circuit, between the entrance of the air itself and the mixing valve with which these apparatuses are equipped, from trailing out further abrasive product.

[5] To overcome this drawback some known realizations make use of a depressurization system that, though, is not always effective since its manual activation is unlikely well- timed compared to the release of the trigger. This becomes clear especially when it requires the use of two different operators if the intervention area is distant from the machine and from the control to operate. Furthermore, this depressurization system noticeably complicates this type of apparatuses, making them more encumbering and onerous.

Disclosure of Invention Disclosure

[6] The principal aim of the present invention is to overcome the cited drawback in a simple, practical and economic way, providing at the same time the maximum security for the operator and for the surroundings.

[7] On the whole, this invention proposes a mixing valve mainly characterized in that it comprises a chamber for the mixing of the compressed air and the abrasive product, wherein a cut-off operates which, at the release of the spray gun trigger, almost im- mediately closes the two inlet ducts for the air and the abrasive material, which are in communication with the mixing chamber itself. Description of Drawings

[8] Description details of the invention will be further evident in the three drawing sheets illustrating a preferred embodiment, by way of an illustrative non-limiting example, wherein:

[9] fig. 1 and 2 illustrate a top view and the transversal section XX of the claimed valve by the plane of to the interception unit for the abrasive material;

[10] fig. 3 illustrates the longitudinal section of the above-mentioned valve at rest and with the ducts closed by its own cut-off;

[11] fig. 4 illustrates the longitudinal section of the valve in operation and the opening of the ducts for the inlet of the air and of the abrasive material. Best Mode

[12] It is evident from the attached illustrations that the claimed mixing valve is composed of a body 1, in aluminium or other suitable material, entirely crossed by a longitudinal cavity 2, serving as mixing chamber and communicating at the exit with a nozzle 3, on which to fix the flexible rubber hose carrying, on the opposite end, the spray gun suitable to supply the jet of abrasive particles and compressed air.

[13] The said chamber comprises a first area of larger diameter 2A, which is overlooked by the compressed air inlet 4, and a second area 2B coaxial to the first one, which is overlooked by the inlet 5 for the abrasive particles.

[14] The air inlet 4, preferably equipped with a control and unidirectional retention unit not represented in the drawings, is located before the inlet 5 of the abrasive particles, according to the crossing path of the mixing chamber 2. It is arranged in this way so that the cut-off 6, thanks to the thrust of an elastic member, spring -like or of other equivalent type operating inside the cylinder 9 axially applied to the chamber 2, can open or close the above-mentioned inlets at a very definite time succession.

[15] The said cut-off 6 is composed of two coaxial parts 6A and 6B longitudinally crossed by a connecting pin 7 that, functioning as spring-holder for the cylindrical coil spring 8 operating to reciprocally space the above-mentioned two parts 6A and 6B of the cutoff, with its own head 7 A prevents from the unthreading of the front part 6B and it is screwed, with the threaded end, in the end portion of the translation rod 9A of the cylinder 9. The translation rod 9 A, connected to a mechanical or pneumatic thrust unit internal to the said cylinder, allows the adjustment of the spring 8 and, consequently, the shift of the front part 6B of the cut-off relatively to the rear part 6A.

[16] At rest, the valve is in the closing position illustrated in fig. 3, in which the front component 6B of the cut-off 6 obstructs with its cylindrical portion the duct 5 for the entrance of the abrasive material and with its front end the exit nozzle 3. The said front end is adequately rounded to compensate with its convexity the wear to which the support stop offered by the frustum-conical flow leader 3 A at the entrance of the nozzle 3 is exposed, for the passage of the abrasive material.

[17] By starting the compressor of the portable sandblasting machine and also by operating the spray gun, the air reaches the valve still in closing position and leaks between the wall of the area 2A and the component 6A of the cut-off 6, while these are still in rest against the narrowing ring on the border between the two areas 2 A and 2B. The air goes around the two parts of the cut-off till it determines, in contrast with the thrust of the mechanical or pneumatic unit of the cylinder 9, the arrival of the part 6A of the cut-off as far as the limit of its own area 2A, and also the translation of the said part 6B trailed by the rear part 6A.

[18] Therefore, the inflow of abrasive material, reaching the valve through the duct 5 and manually adjusted through the interception unit 10, starts only after the air inlet and stops before its closure when, owing to the release of the spray gun trigger, the mechanical or pneumatic thrust unit of the cylinder 9, previously compressed, expands taking the entire cut-off 6 back to closing position. This means that the part 6A is brought in rest against the narrowing ring on the border between the two areas 2A and 2B, and the part 6B is brought to lean, pushed by its own spring 8, on the border of the area 2B and in particular against the frustum-conical flow leader 3 A of the nozzle 3, thus securing its closure.

[19] From what is described above it is evident that the claimed valve is particularly versatile, since it can easily adapt to the different physical, mechanical and particle- size features of the various materials with which cleaning or finishing operations can be performed and without the need to use different apparatuses depending on the materials used.

[20] Finally, the claimed valve, whose overall features illustrated and described being unchanged, could be susceptible to changes and variants anyway included within the present claimed invention.

Claims

[1] Mixing valve for portable sandblasting machines characterized in that it comprises a mixing chamber (2) suitable to receive air and an abrasive material and to be set in communication with an outflow nozzle (3) for the outflow through a suitable connectable spray gun that can be operated through a trigger, wherein an air inlet (4) and an inlet (5) for the abrasive material are positioned, and a cut-off (6) housed in the said mixing chamber (2), suited to be moved between an opening position owing to the air pressure and a closing position by operation of suitable mechanical or pneumatic means which are compressed in the said opening position, being the said air inlet (4) positioned before the said inlet (5) for the abrasive material according to the air flow direction across the said mixing chamber (2), so that the inflow of the abrasive material starts after the air inflow and stops before the stop of the air inflow when, upon release of the said spray gun trigger, the said mechanical or pneumatic means, previously compressed, expand taking the said cut-off (6) back to said closing position.

[2] Mixing valve for portable sandblasting machines according to claim 1, characterized in that it consists of a body (1) that, suited to the fixing of the said nozzle (3) on which to fix a flexible rubber hose carrying the said spray gun on its opposite end, is entirely longitudinally crossed by the said mixing chamber , wherein the said compressed air inlet (4) is positioned in a first area (2A) with larger diameter and the said abrasive particles inlet (5) in a second area (2B), coaxial to the first one (2A).

[3] Mixing valve for portable sandblasting machines according to one of the previous claims, characterized in that the said cut-off (6) is composed of two coaxial parts (6A, 6B) with different diameters, being the first part (6A) constrained to the said mechanical and pneumatic means suited to operate the closing movement, and the second part (6B), with smaller diameter, constrained to the first part (6A) through a connecting pin (7) serving as spring-holder for a cylindrical coil spring (8) operating to reciprocally space the said first and second parts (6A, 6B) of the said cut-off (6).

[4] Mixing valve for portable sandblasting machines according to claim 3, characterized in that the said connecting pin (7) prevents with its head (7A) from the unthreading of the said front second part (6B) and is screwed, with a threaded end, to the end of a translation rod (9A) of the said pneumatic and mechanical means (9), which allows the adjustment of the said spring (8) and, consequently, the relative shift of the said front second part (6B) of said the cut-off (6).

[5] Mixing valve for portable sandblasting machines according to one of the previous claims, characterized in that the second part (6B) of the said cut-off (6) occludes with its cylindrical portion the inlet (5) for the entrance of the abrasive material and with its front end the exit nozzle (3), being the said end adequately rounded to compensate with its convexity the wear to which is exposed, for the passage of the abrasive material, a frustum-conical support stop offered by a flow leader (3A) positioned at the entrance of the said nozzle (3).

[6] Mixing valve for portable sandblasting machines according to one the previous claims, characterized in that by starting the said portable sandblasting machine and also by operating the said spray gun, the air reaches the valve still in the said closing position and leaks between the surface of the said first area (2A) and the first part (6A) of the said cut-off (6), still in rest against a narrowing ring on the border between the said first and second areas (2A, 2B), going around the said first and second parts (6A, 6B) of the said cut-off (6) till it determines, in contrast with the thrust exerted by the said mechanical or pneumatic means of the said cylinder (9), the arrival of the said first part (6A) of the said cut-off (6) as far as the limit of the said first area (2A), and also the translation of the said second part (6B) trailed by the said rear first part (6A).

[7] Mixing valve for portable sandblasting machines according to claim 6, characterized in that the inflow of the abrasive material reaching the valve through the said inlet (5) and manually adjusted through an interception unit (10), starts after the air inlet and stops before its closure when, owing to the release of the said spray gun trigger, the said mechanical or pneumatic thrust means of the said cylinder (9), previously compressed, expands bringing the said entire cut-off (6) back to closure.

[8] Mixing valve for portable sandblasting machines according to claim 7, characterized in that the closure of the said cut-off (6) is realized through the rest of the said first part (6A) against the said narrowing ring at the border between the first and second areas (2A) and (2B) of the said chamber (2) and the rest of the said second part (6B), pushed by its own spring (8), on the border of the said second area (2B) and in particular against the said frustum-conical flow leader (3A) of the said nozzle (3).