US 3221993 A
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Description (OCR text may contain errors)
7 Dec. 7, 1965 E. J. BALS 3,221,993
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SPRAYING EQUIPMENT Filed Oct. 22, 1962 3 Sheets-Sheet 5 l9 2o /2\ HHHHIHHI 20 /6 2 7 22 /5 am mi L 25 I H 2 I I 4 32 A s 6 3 7 INVENTOR fan Mo duL/w 1344.:
ATTORNEY United States Patent 3,221,993 SPRAYING EQUIPMENT Edward Julius Bals, Pedmore, near Stourbridge, England,
assignor to Birfield Engineering Limited, London, England, a company of Great Britain Filed Oct. 22, 1962, Ser. No. 232,220 Claims priority, application Great Britain, Oct. 24, 1961, 37,994/ 61 1 Claim. (Cl. 239-77) This invention relates to spraying equipment of the type comprising a duct and a rotary atomiser at or adjacent the downstream end of the duct, so that an air blast produced by an engine-driven fan in the duct picks up atomised droplets produced by the atomiser and carries them away in the form of a spray.
Equipment of the foregoing type commonly employs a common drive for the fan and atomiser. In such equipment the size of the droplets of liquid produced by the atomiser is inversely proportional to the speed of rotation and the square root of the diameter of the atomiser. It has been found that to obtain the most favourable size of droplet for crop spraying an atomiser of rather large diameter must be used. The effect of this is to throw the droplets off at an excessive tangential velocity, so that they tend to pass through the air stream instead of becoming entrained in it.
As the tangential velocity is directly proportional to the diameter of the atomiser and the speed of rotation, it follows that droplets of the required size can be produced with reduced tangential velocity if the speed of the atomiser is increased, and the diameter is reduced. This reduction in diameter slightly increases the length of the tangent between the atomiser and the annular air stream.
The object of this invention is to provide equipment which enables the atomiser to be driven at considerably higher speed than the engine, so that the diameter of the atomiser can be reduced While the size of the droplets remains substantially the same, without increasing the cost of the engine or necessitating a gear drive for the atomiser which would add not only to the cost but also to the weight of the equipment.
To this end, according to the invention, spraying equipment of the type set forth has a rotary atomiser driven by turbine blades disposed downstream of the enginedriven fan and themselves driven by the air blast, the turbine blades being of comparatively small pitch as compared with the blades of the fan.
Preferably the atomiser is mounted at the downstream side of the turbine blades effectively just within the downstream end of the duct, and a common shaft on which the turbine blades and the atomiser are both mounted is conveniently itself mounted in bearings within a hub on which are mounted deflector blade positioned downstream of the fan to reduce the rotational component of velocity of the air blast. Alternatively, the hub of the fan may be extended in the downstream direction and the common shaft mounted in bearings therein, so that the frictional loss in the bearings is very much decreased as a result of the lower actual bearing speed.
Two diametrically opposed turbine blades may be used mounted on a hub structure in the form of a two-bladed windmill, the hub structure being connected to the atomiser. It has been found highly desirable that the turbine blades each be arranged with the trailing edge thereof disposed radially of the rotational axis of the blades, and the blades may be formed on a one-piece sheet metal pressing with the blades formed to a concave lateral profile facing the air blast.
The invention will now be further described with ref- 3,221,993 Patented Dec. 7, 1965 erence to the accompanying drawings which illustrate, by way of example, one form of spraying equipment in accordance with the invention. In the drawings:
FIGURE 1 is an end view of the equipment,
FIGURE 2 is an opposite end view, and
FIGURE 3 is a side View partly sectioned on the line III III in FIGURE 1.
The equipment comprises four cowlings 1, 2, 3 and 4 which taper in the downstream direction and are flange bolted together at 5, 6 and 7 to form a duct. The upstream end cowling 1 is flared to form an air intake cowling and is used to mount the complete cowling assembly on the frame of a small internal combustion engine 8 which provides a self-contained power unit of the equipment. The immediately adjacent cowling 2 houses a multiblade fan 9 a central hub 10 of which is mounted on the crankshaft 12 of the engine 8 rotation of which thus produces an air blast in the duct; the cowling 3 houses fixed deflector blades 13 which reduce the rotational component of the blast leaving the fan 9; and the downstream end cowling 4 houses a two-bladed windmill 14 and a rotary atomiser 15 mounted on a common shaft 16.
The atomiser 15 has a hub portion 17 which is at the downstream end of the atomiser and positioned just beyond the mouth of the duct, the effective portion of the atomiser 15 consisting of a gauze cylinder 18 mounted on the portion 17. The gauze cylinder 18 is open at the upstream end and coaxially surrounds the shaft 16, and on rotation of the atomiser 15 any liquid Within the cylinder 18 is sprayed outwardly from the latter as an atomised mist under centrifugal action.
At the upstream end the shaft 16 is extended past the windmill 14 into the hub 19 of the deflector blades 13, being mounted therein in two spaced and adjustable cup and cone bearings 20. A thrower ring 22 mounted on the shaft 16 protects the downstream bearing 20 from any of the spraying liquid which may run along the shaft 16, and a lubricator 23 is provided for external lubrication of the bearings 20. A liquid supply pipe 24 passes through the wall of the downstream end cowling 4 to feed the liquid to be sprayed to the centre of the atomiser 15, and the pipe 24 is supplied from a liquid reservoir (not shown) in a suitable manner.
The fan 9 has blades of normal pitch, the blade section being inclined at about 40 to the duct axis, whereas the turbine blades of the windmill are of very small pitch. In fact the turbine blade section is inclined at about to the duct axis, and these blades are formed integrally in a simple sheet metal pressing of cranked form in the plane of the windmill 14 to provide trailing edges disposed radially of the shaft 16. Each turbine blade is pressed to a convex lateral profile facing downstream of the air blast.
In use the fan 9 is driven at a speed of approximately 5000 rpm. and the air blast impinging on the turbine blades of the windmill 14 drives the windmill and atomiser 15 at a speed somewhat greater than 15,000 rpm. even when liquid is being fed to the atomiser 15 through the pipe 24. Thus the atomiser 15 rotates at somewhat more than three times the fan speed, and can be made much smaller in diameter for the same results than if it were driven at fan speed as in prior arrangements. The resultant small droplets are acted upon by the air blast, and are ejected from the duct in the form of an atomised spray which can be directed in the desired spraying direction.
The frame of the engine 8 is mounted on a support stem 25 by means of an adjusting plate 26 which pivots at 27 on the stem 25. A notched periphery 28 of the plate 26 is engaged by a locking bolt 29 which is axially displaceable to clear the notches and can be selectively engaged with the latter to fix the plate 26 in an adjusted position. This enables the inclination of the spraying trajectory to be adjusted to spray a desired area. The stem 25 has a base mounting flange 30 which is received Within a mounting ring 32 which can be bolted down to a supporting structure. Loosening off of the ring 32 enables the horizontal direction of the spraying trajectory to be adjusted.
A wire grill 37 at the downstream end of the duct, just within the cowling 4, provides a guard for the windmill 14. The grill 37 has a central aperture through which the shaft 16 and atomiser 15 project.
It will be seen that the described equipment provides a very compact assembly which is self-contained apart from the spraying liquid reservoir. A petrol tank 33 for the engine 8 is bolted at 34 to the adjoining flanges of the cowlings 1 and 2, thecarburettor 35 is arranged at one side of the equipment and the exhaust silencer 36 at the opposite side.
Liquid spraying equipment comprising an internal combustion engine, an axial-flow fan mounted on: the crankshaft of said engine, a rotary atomiser, a Windmill for driving the atomiser and connected to the upstream side of the atomiser, said Windmill embodying blades of comparatively small pitch as compared with the blades of said fan, fixed deflector blades positioned between said fan and said windmill, and a common duct comprising four annular cowlings bolted together, namely an upstream end cowling forming an air intake, a next adjoining cowling forming a housing for said fan, a next adjoining cowling housing said fixed deflector blades, and a downstream end cowling housing said Windmill.
References Cited by the Examiner UNITED STATES PATENTS 1,974,538 9/1934 Johnston 239.77 2,738,226 3/1956 Bals 23977 2,965,302 12/1960 Waldrum g 23977 2,979,269 4/1961 Bals 239.77 3,063,644 11/1962 Bals 239-77 FOREIGN PATENTS 1,167,611 8/1958 France.
EVERETT W. KIRBY, Primary Examiner.