US 3074600 A
Description (OCR text may contain errors)
Jan. 22, 1963 w. J. WARHURST 3,074,600
POWDER SPRAY DEVICES Filed April 15, 1960 lz'z/u 121mb 7. Hafhurai;
United States Patent 3,074,600 PGWDLJR SIRAY DEVICES Wiliiam John Warhurst, Albany Works, 7 High St, Hampton Hill, England Filed Apr. 15, 1960, Ser. No. 22,498 4 Claims. (Cl. 222-193) This invention relates to powder spray devices and has been devised with the object of providing a generally improved device for this purpose.
There has previously been proposed a device for producing a cloud of powder and air for spraying a small quantity of powder through a nozzle onto a printed sheet or other surface, wherein a powder extractor intermittently extracts small charges of powder from a container and exposes the charges to a jet of air issuing from a nozzle in a mixing chamber whereby the jet of air removes each successive charge from the extractor by entraining each charge and causes dissemination of the powder in the jet of air.
A device for the same purpose according to the present invention is primarily characterised in that the charges are extracted into a space behind a nozzle and subjected to an air stream induced by an air jet issuing from the nozzle and with which the powder then becomes entrained to issue as a spray.
The improved device preferably also includes amongst other features a regulator for varying the amount of each charge.
One particular and at present preferred device according to the invention is shown in the accompanying drawings in which:
FIGURE 1 is a central vertical section of the device;
FIGURE 2 is a section on line X--X of FIGURE 1, and
FIGURE 3 is an elevation view in the direction of arrow A in FIGURE 1.
Referring now to the drawings, the device comprises a base 1 in the shape of a bowl which forms the lower part of a powder container the body of which is constituted by a transparent cylinder 2.
The container is closed by a top cover 3 and gaskets 4 are fitted to seal the joints between the cylinder 2 and the bowl 1 and cover 3. The whole container assembly is held together by a U-shaped bail 5 the central part of which engages the cover 3 and having inturned ends pivotally supported in holes (not shown) in the wall of the bowl 1.
The cover 3 has a filling opening normally closed by an apertured plug 7.
At the centre of the bowl 1 is a cylindrical chamber 12 access to which for cleaning purposes is by removal of a screw plug 15. This chamber contains the lower end of a plunger 11 which is downwardly biased by a spring 21 and attached at its head end to the centre of a resilient diaphragm 8 which forms the floor of the powder container. The edge of this diaphragm is held in the bowl 1 by a metal washer 9 and a circlip iii which engages in a recessed part of the bowl.
At one side of the bowl I there is fitted a pilot valve 18 controlled by a spring I9 and intended to be subjected to an intermittent stream of air derived from a compressed air supply and admitted through a union 20. There are two outlet ducts 15', 22 leading from the region of the pilot valve the former communicating with the chamber 12 and the latter communicating with an air space on one side of a resilient diaphragm 23. The pilot valve is also open to atmosphere on its outlet side through a vent 24 as shown in FIGURE 2.
The bowl 1 is formed at one side with a square external boss 31 which contains a hardened cylindrical liner 30 forming a bore within which a powder extractor plunger 3,67%,ddii
- 29 is slidably received. The outward end of the liner is enlarged to accommodate a coil spring 28 which bears against the enlarged head of the plunger 29 to bias the latter in an outward direction.
The plunger head is engaged by a rivet attached to the centre of resilient diaphragm 23 which is peripherally sealed against the boss 31 by a cover 27 secured by screws 26. The diaphragm 23 is backed up by the enlarged head of a regulating shaft 25 which is pressed inwardly by a spring 32 and rotatably received through the cover 27.
The shaft 25 is grooved to accommodate a sealing washer 33 and screwed onto its outer end is a knurled knob 34 secured by a lock nut 35.
For preventing access of powder to the interior of the liner 30 there is fitted between the inward end of the latter and the plunger 29 a flexible sealing sleeve 36.
On the side of the bowl 1 opposite the boss 31 there is detachably secured by means of screws 3'7 (FIGURE 3) a face plate 38 having a flared powder discharge orifice 39 in front of the nozzle 16 and communicating with an air inlet orifice 40 in front of the reduced diameter end of the plunger 29 which is a sliding fit through a hole 59 in an inwardly directed part 51 of the face plate and is formed with a series of circumferential powder-extracting grooves 41.
Provision is made for adjusting the initial position of the powder extractor plunger 29 to regulate the length of its stroke and thereby the number of powder extracting grooves which can pass from one side to the other of the hole 54 Accordingly the inward face of the knurled knob 34 on the regulating shaft 25 is formed as a spiral cam surface 42 which is notched at regular intervals for engagement with a tooth 43 on cover 27.
In operation when compressed air is intermittently supplied through union 2% it lifts pilot valve 18, passes through duct 22 and in conjunction with springs 28 and 32 causes pulsation of diaphragm 23 and reciprocating movement of powder extracting plunger 2%. Simultaneously air intermittently flows along duct 15 into chamber 12 whence it flows through duct 14 and issues at high velocity from nozzle 16. The air jet from the nozzle causes air to be drawn in through inlet 46 to form an air stream indicated by arrows S in which is entrained any powder contained at that instant in the grooves 41 of the plunger 29 when the latter is in its projected position. The powder thus extracted is discharged from orifice 35% with the air stream.
The intermittent supply of compressed air to chamber 12 also acts on the head of the spring biased plunger 11 therein to cause rapid vibration of diaphragm S and thereby prevent compaction of the powder in the bowl I.
In a modified form of apparatus the powder container assembly may contain a co-axial tube into which small charges of powder are carried by the grooves of a radially directed reciprocating plunger as aforesaid. In such an arrangement the nozzle is mounted at the centre of the bowl in a position such that the intermittently supplied compressed air stream creates a partial vacuum at the lower end of the central tube and the powder mixed with air is discharged along a radial passage to the exterior of the device.
1. A powder spray device comprising a powder container, a powder and air mixing chamber adjoining the powder container and having an air inlet and a powder spray outlet, a nozzle for admitting an air jet intermittently to the mixing chamber, in the direction of the powder spray outlet a powder extracting plunger mounted across the base of the powder container and having at one end recesses for collecting small charges of powder, from the powder container and means for reciprocating the plunger to cause the said end of the plunger with said Patented Jan. 22, 1963 1 recesses periodically to enter the said mixing chamber behind the outlet of said nozzle simultaneously with the occurrence of an air jet through said nozzle which causes an air flow through the mixing chamber so that said powder charges became mixed by entrainment with said jet and are delivered through said discharge opening.
2. A powder spray device as set forth in claim 1 having a pneumatically operated diaphragm for moving the plunger in one direction and a spring for moving the plunger in the opposite direction.
3. A powder spray device as set forth in claim 1 having means for adjusting the length of the stroke of the said plunger for regulating the rate at which powder is extracted from the container and sprayed from the device.
4. A powder spray device as set forth in claim 1 in- 15 cluding a pneumatically operated diaphragm for moving the plunger in one direction, and a spring for moving the plunger in the opposite direction, a shaft bearing against the back of the diaphragm and means for adjusting the position of said shaft along its axis to vary the amplitude and vibration of the diaphragm and thereby the length of the stroke of the plunger.
References-'Cited inthe file of this patent UNITED STATES PATENTS 2,818,200 Webb et a1. Dec. 31, 1957 2,860,819 Ledingham- Nov. 18,1953
FOREIGN PATENTS 327,747 Switzerland Mar. 31, 1958