GB2180778A - Air-delivery adjusting device in a spray-gun - Google Patents

Abstract

Between the handle 3 of a spray gun and a compressed-air inlet fitting 19 is a valve body 11 provided with two blind bores 14, 15. The bores communicate via holes 16, 17 in the body and an outer chamber 27 formed in the handle. An adjusting member 8 comprises a locking nut 12 mounted on the valve body 11 and axially movable on the same so as to progressively open or close the air passage through said through holes 16, 17, among which the ones 16 relating to the bore 14 are of differentiated diameters. <IMAGE>

Description

SPECIFICATION Air-delivery adjusting device in a spray-gun The present invention relates to an air-delivery adjusting device in a spray-gun.

It is known that spray-guns are compressed air operated apparatuses which are designed to spray any surface with atomized paint. For the purpose, generally they briefly consist of a body extending to form a handle inside which a central canalisation is located. The latter extends from the lower handle end to a sprayer suitably located on the spray-gun body.

Furthermore, a paint feeding duct gives out close to the sprayer, the paint being contained in a reservoir connected to the spray-gun.

When the latter is operated, a compressed air feeding tube is connected to the central canalisation, air being supplied by a common compressor. By suitably acting on a trigger lever, the air passage to the sprayer is opened and the paint flowing therefrom is simultaneously evenly distributed.

The principle on which the operation of the spray-guns briefly described hereinbefore is based resides in that the high speed reached by the compressed air while it expands in the sprayer causes paint to be delivered.

It will be recognized that the operating conditions and performances required of the above mentioned spray-guns can vary from time to time depending, for example, upon the type of paint used and/or the type of painting that is wished to obtain.

In order to meet such requirements, sprayguns are provided with suitable adjusting devices. One of them, which is very important to the ends of the present invention, is a device enabling the adjustment of air delivery to the sprayer. Such a device is of great convenience due to the fact that it enables the adjustment of the jet strength as well as of the paint atomization, these characteristics being of the greatest importance for a successful painting.

At present a number of air-delivery adjusting devices are known which substantially differentiate from each other for the location they have on the gun and the system adopted in dispensing the compressed air flow.

Some of them are interposed between the feeding tube and the central canalisation of the spray-gun and consist of a cylindrical valve body inside which an inlet duct and an outlet duct are obtained. Air coming from the feeding tube passes from one duct to the other through a series of through holes disposed on the valve body, and in this region an annular chamber is created which is defined by a locking nut connected to the valve body. The locking nut is further provided with a shoulder adapted to close the holes relating to the outlet duct to a smaller or greater extent depending upon the mutual positioning locking nut-valve body. In this way it is possible to carry out the adjustment of the air supply to the central canalisation without any difficulty by merely screwing and unscrewing the locking nut.

The adjusting devices of the above described type have proved to be quite efficient in accomplishing their task. However they have some disadvantages due to the fact that, in order to allow the locking nut manoeuvrability they must necessarily be located at the outside of the gun handle. This involves a first drawback consisting in that during the gun operation the paint atomized and suspended in the air can enter (which often occurs) the gaps existing between the valve body and locking nut coupling and it can store therein.

As a result, the locking nut can be operated with difficulty and in the worst cases it even jams.

In addition, its positioning at the outside of the handle also causes the gun to be unbalanced. As a result, the operator must do a certain manual effort in order to hold the paint jet in the desired direction.

A further drawback inherent in the above described devices is to be ascribed to the fact that the through holes relative to the outlet duct are closed simultaneously and to the same extent by the shoulder provided on the locking nut. As a result, lack of precision in operation ofter occurs when adjustments on air jets of very little importance have to be carried out.

Under this situation it is an object of the present invention to obviate the above mentioned drawbacks by providing a device adapted to be contained, as to its essential parts, inside the handle of the spray-gun.

A further object of the present invention is to provide a device adapted to allow a better adjustment of the air flow above all when the flow of small amounts of air is concerned.

A still further object of the present invention is to provide a device of low price and easy construction.

The foregoing and still further objects that will become more apparent in the following are substantially attained by an air-delivery adjusting device in a spray-gun of the type com prising an inlet duct at one end of which a pipe fitting is provided connecting it to a com 'pressed air feeding tube, an outlet duct giving out into the central canalisation of the gun, said ducts being obtained in a valve body pro vided with through holes located at the op posed ends respectively of said ducts, a chamber connecting said ducts to each other for the passage of fluid,as well as an adjusting member consisting of a locking nut mounted on said valve body and axially movable on the same so as to progressively open or close the air passage through said through holes, char acterized in that said chamber connecting said ducts is located within the gun handle and is sealingly engaged by said locking nut, said valve body being housed inside said chamber.

Further features and advantages of the invention will become more apparent from the detailed description of a preferred embodiment of an air-delivery adjusting device in a spraygun, given hereinafter by way of non-limiting example with reference to the accompanying drawings, in which: Fig. 1 shows, in a perspective view, a spray-gun incorporating the device of the invention; Fig. 2 shows the device of the present invention partly in section.

Referring to the drawings, a conventional spray-gun known in itself has been globally identified by reference numeral 1. Briefly it consists of a body 2 extending to form a handle 3 and ending in a horizontally-directed sprayer 4. A paint reservoir 5 is also provided which is coupled in a removable manner with body 2, at the lower part thereof,through a connection 6.

A control lever 7 is pivoted on body 2, said lever opening the air passage to the sprayer 4 while simultaneous ly adjusting the paint flow to the same.

The spray-gun 1 further comprises a device for the adjustment of the air delivery, globally identified at 8 and connected at the lower part thereof to handle 3, as well as additional adjusting devices the control handles 9 of which are connected to the rear of body 2.

A central canalisation 10 which is only partially visible in the accompanying figures, extends inside the gun 1 from the lower end of handle 3 to sprayer 4.

According to the invention and referring particularly to Fig. 2, the air-delivery adjusting device 8 comprises a valve body 11 of cylindrical section on which a locking nut 12 is provided, said locking nut being associated therewith through a screw threaded engagement 13.

In greater detail, the valve body 11 is comprised of an inlet duct 14 and an outlet duct 15 coaxially obtained in the same and extending towards opposite directions. Close to the opposed ends of said ducts 14 and 15 and in relation to each of them, respective through holes 16 and 17 are provided which are aligned according to one and the same diametral plane and extend radially in the valve body 11.

In an original manner, holes 16 are slightly different in diameters with respect to each other, which involves the advantages to be described in the following.

In the region of the free end of duct 15 a screw thread 18 is provided through which the device 8 in question is connected to the central canalisation 10 in gun 1. In the region of the free end of duct 14 a pipe fitting 19 is provided which comprises a hexagonal head 19a and a threaded portion 19b. A compressed air feeding tube (not shown as conventional and known in itself) is intended to be connected to said threaded portion 19b.

In an original manner, the locking nut 12 extends on the valve body 11 in a position located between holes 16 and the pipe fitting 19. At the outside it defines a cylindrical surface 20 on which a sealing ring 21 is located.

At the respective ends of said cylindrical surface 20, the locking nut 12 exhibits a conical portion 22 and a knurled annular portion 23 overlapping the hexagonal head 19a, as shown in Fig. 2. At the inside and in the region of the end relating to the conical surface 22, the locking nut 12 is provided with an annular working surface 24 of calibrated diameter so that substantially it sealingly mates with the valve body 11. Inside the locking nut 12, a further annular surface 25 is also provided which substantially extends between the threaded coupling 13 and the annular portion 23. A sealing ring 26 located on the valve body 11 acts on said surface 25.

Advantageously, when the device 8 in question is connected to the spray-gun 1, the locking nut 12 engages with a cylindrical chamber 27 disposed at the base of handle 3 and projecting therefrom in the region of its knurled annular portion 23.

Likewise, the valve body 11 extends inside the cylindrical chamber 27 and engages, by its screw thread 18, with the free end of the central canalisation 10.

Operation of the device according to the invention described above mainly as regards structure, is as follows.

The compressed air coming from the previously mentioned feeding tube runs through the inlet duct 14 and comes then out of holes 16 relative thereto. In this way the compressed air passes through the cylindrical chamber 27 sealingly separated from the surrounding atmosphere by means of the sealing ring 21 and enters the valve body 11 again,in the region of holes 17 relative to the outlet duct 15.

Afterwards, the compressed air reaches the central canalisation 10 that brings it to sprayer 4 in a known and conventional manner.

The adjustment of the air flow to the central canalization 10 is carried out by suitably acting on the annular portion 23, which enables the locking nut 12 to be screwed and unscrewed so that the latter can be axially moved with respect to the valve body 11. In this way the annular surface 24 of the locking nut 12 can close holes 16 to a smaller or greater extent depending upon the positioning of the locking nut itself.

Advantageously, the difference between the diameters of holes 16 also allows that the passage therethrough of very small amounts of air may be adjusted to the best. In fact, it is clear that by acting on the locking nut 12 so as to progressively restrain the air pas sage, it will be possible to obtain first the total closing of the smallest hole, followed by the closing of the other holes in succession, which clearly results in a finer and more precise air-delivery adjustment.

Attention is drawn to the fact that the device in question is substantially fully contained within the gun handle 3, extending outside the same only in the region of the pipe fitting 19 and annular portion 23. In this way all drawbacks to which the above described conventional adjusting devices were subjected have been eliminated.

Furthermore, the device in question appears of simple and cheap construction.

The present invention is susceptible of many modifications and variations all coming within the scope of the inventive idea characterizing it.

All details can be replaced by technically equivalent elements. The materials used may be of any type and the shapes and sizes of any nature and magnitude in accordance with requirements.

Claims (2)

1. Air-delivery adjusting device in a spraygun of the type comprising an inlet duct at one end of which a pipe fitting is provided connecting it to a compressed air feeding tube, an outlet duct giving out into the central canalisation of the gun, said ducts being obtained in a valve body provided with through holes located at the opposed ends respectively of said ducts, a chamber connect ing said ducts to each other for the passage of fluid, as well as an adjusting member consisting of a locking nut mounted on said valve body and axially movable on the same so as to progressively open or close the air passage through said through holes, characterized in that said chamber connecting said ducts is located within the gun handle and is sealingly engaged by said locking nut, said valve body being housed inside said chamber.

2. A device according to claim 1, characterized in that the through holes relating to said inlet duct are of respectively differentiated diameters and are disposed according to one and the same plane transverse to said valve body, so that they are closed in succession by said locking nut during the air-adjusting step.