Fluid sprinkling – spraying – and diffusing – With means causing intermittent interruption of supply to...
Reexamination Certificate
1999-07-09
2001-01-23
Kashnikow, Andres (Department: 3752)
Fluid sprinkling, spraying, and diffusing
With means causing intermittent interruption of supply to...
C137S624140, C239S101000, C239S413000, C239S526000, C239S532000, C239S570000
Reexamination Certificate
active
06176437
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a compressed air dusting gun and more specifically, to a gun which includes a pressure discharge valve oscillating within a predetermined frequency range.
The application of compressed air for removal of dirt and cleaning purposes is a well known and extensively used technique. In order to produce a concentrated and controllable air jet, the usual design includes a pistol-like tool equipped with an oblong air nozzle and a built-in shut-off valve. The shut-off valve is manually operated via a pawl or similar trigger mechanism mounted in connection with the handle of the dusting gun. When the trigger mechanism is activated, a concentrated air jet is discharged through the nozzle and by pointing this air jet on the object to be cleaned, it is possible to loosen and blast off foreign matter, such as dust, earth, oily coats. The ability of the air jet to loosen old dirt and adherent coatings of various kinds depends on the dynamic pressure exerted by the jet, i.e. primarily the jet velocity. The greater the velocity, the better the cleaning effect.
However, the jet velocity is limited to the available air pressure source, usually on the order of
6
bar, and consequently, an increase in the cleaning effect can only be achieved by increasing the air flow. Especially for the purpose of removal of adherent thick accumulations, the air consumption may easily be disproportionately large and the cleaning method therefore uneconomical.
DE Publication No. 1,099,760 (Odendahl) describes a known dusting gun for compressed air which consists of a valve designed with a longitudinally displaceable oblong valve body whose one end is in sealing contact against a valve seat shutting off the air flow through the gun under the influence of a compression spring, and whose other end is embodied as a piston, which is displaceably inserted into a closed cylinder. One side of the piston is in contact with the air duct in the dusting gun downstream of the valve via a longitudinal bore through the valve body and whose other side is in connection with the pressure side upstream of the valve through an adjustable regulator. The inlet to and the outlet from the dusting gun are shaped as a Laval nozzle. The regulator may be adjusted so that the movement of the piston is in resonance with the natural frequency of the pressure column in the system.
This known dusting gun is complicated in its construction. It is difficult to adjust and the velocity of the air is oscillating in a region from somewhat below to somewhat above the Mach region.
SUMMARY OF THE INVENTION
It is a purpose of the present invention to describe a blast gun for compressed air without the drawbacks of known prior art which is simple in construction and which has a high cleaning effect and high efficiency. According to the invention, this is achieved by designing the dusting gun as described and claimed hereinafter.
The dusting gun of the invention employs an oscillating shut-off valve with the effect that the compressed air, instead of being ejected as a continuous air jet through the nozzle, is divided into a series of short pressure pulses, more specifically, a pulsating air stream with periodically repeated pressurized discharges. These periodical pressure discharges, by way of example with frequencies in the range of 2-50 Hz, involve a time related concentration of the pressure energy of the air so that the peak value of the dynamic pressure of the air in each individual pulse is increased as compared to the dynamic pressure that would be achieved if the same volume of air is ejected continuously through a nozzle. The dynamic pressure in the air jet determines the ability of the air to loosen adherent accumulations from the surface to be cleaned.
In addition to the greater dynamic pressure, it has been discovered that the pulsating air jet also has the effect of setting the impurities in vibrating motion under the influence of the air pulses. In the case of certain types of impurities and coats, practice has shown that this effect contributes to increasing the cleaning action of the dusting gun as the vibrations cooperate in loosening the substances so that the cleaning operation is much faster, more thorough, and more economical with regard to the consumption of compressed air. The dusting gun according to the invention is therefore able to replace traditional high pressure continuous flow cleaning or water-based jet cleaning, with the advantages this entails, both with regard to economy and environmental protection.
According to the invention, the piston seal is made of Teflon® brand PTFE or a similar material and further in accord with this design, the sealing arrangement satisfies the demand for low friction and ease of valve actuation. An expedient measure is the manufacture of the valve seat or the valve body itself with a rubber or other elastic coating, such as polyurethane or synthetic rubber, with a view to reduce noise level and to assure long life of the valve.
The dusting gun, according to the invention, can, like any ordinary compressed air dusting gun, be combined with an ejector for the supply of liquid or granular material together with the air. The combination of pulsating compressed air and an additive consisting of a granular agent for cleaning or a liquid cleaning solution provides a significant increase in the cleaning result. This option is proposed for special cases where a significant increase in cleaning efficiency is demanded.
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Dennison, Scheiner Schultz & Wakeman
Kashnikow Andres
Skannerup Mona
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