US2786656A

US2786656A - Impact spraying of slurries

Info

Publication number: US2786656A
Application number: US438743A
Authority: US
Inventors: Ernest R Corneil
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-06-23
Filing date: 1954-06-23
Publication date: 1957-03-26
Anticipated expiration: 1974-03-26

Description

Filed June 23, 1954 March 26, 1957 E. R. CORNEIL 2,786,656

' IMPACT SPRAYING 0F SLURRIES 2 She e ts-Sheet 1 IN VEN TOR. frnasi R. Carrzez' Z March 26, 1957 E. R. CORNEIL IMPACT SPRAYING OF SLURRIES 2 Sheets-Sheet 2 Filed June 23, 1954 IMPACT SPRAYING DFSLURRIES Ernest R. Cornell, Thoro'ld, Ontario, Canada Application June 23, .1954, Serial No. 438,743

3 Claims. '(Cl. 259-151) This invention relates to a .means for spraying and more particularly ,for spraying slurries of .coarse particles of a pigment in .a liquid carrier.

Heretofore therel1as been ,no satisfactory way .to spray a slurry containing massiveplgment particles onto a surface and obtain a uniform coating. Dilficulty is encountered because of the natural tendency of the particles to settle out-of suspension, thus clogging equipment and resulting in a non-uniform coating. Thus .pigment partic'le size constitutes a limitation in theme of priorspraying equipment.

Further, in order to maintain continuous flow and a uniform spray of suspended pigments in a liquid carrier, low viscosity carriers are used containing volatiles which are lost by evaporation, ,On drying. These vapours create an unpleasant atmosphere and a danger of fire and explosion.

Another object is to provide an efticient ,.easily cleaned, inexpensive sprayer for applying coatings of coarse pigment particies in non-volatile liquid carriers.

A further object is to provide a device .for spraying a slurry of massive particles of solid materials in a liquid carrier which agitates into homogeneity -and .then discharges successive incrementsof such slurry.

The invention will be described with reference to the accompanying drawings, in which:

'Figure 1 is a sectional elevation ofone embodiment of the invention,

Figure 2 is a plan view of one form of nozzle,

Figure 3 is a section through the nozzle .of :Figure 2,

Figure 4 is a plan view of another form of nozzle, and

Figure '5 is a space diagram indicating acceleration and velocity variation with time.

Referring to Figure 1, 1 is a body member having a mixing chamber 2 therein arranged to receive slurry 3 through intake 4 from a supply tank .5. Apiston 6 is disposed in chamber 2 and is carried 'byrod 7 reciprocally mounted in the wall of the chamber. Axially aligned with piston '6 is a cylinder 9.3150 .mountedin the wall of chamber '2. The cylinder '9 has an open inner end to reciprocally receive the piston 6 in sliding fit engagement therewith and its outer end .is provided with a nozzle structure 10. The nozzle structure 10 .comprises an inner rigid disc or support plate 11, slightly dished as shown, engagingthe outer end .of :cylinder 9 and :having an :elongated centrally disposed slot 212 itherein. A disc 13, part or .all of which .is .formed of Efiexible material, such as rubber, rubber fabric, .or plastic composition, overlies, has a slit 14 thereinoverlying slot 12 and'substantially coextensive therewith. The 'slit 14 provides complementary resilientlips .15 .and 11 6 in normally closed relation due to the inherent resiliencyt f the flexible disc 13. A ring clamp 17, in screw-threaded engagement with the body .rnernber it, retains the discs 11 and 13 in position on the outer end of the cylinder 9, a sealing ring 18 being interposed between the clamp 17 and disc 13. It will be apparent that the clamp 17 is readily removable, as by means of a wrench or the like, for removal of discs 11 and 13 to permit cleaning of associated portions of the device.

gaged by oneend of a coil spring 29 also supported in guide 18a. The other end of spring v20 .bears against a plate .22 which is longitudinally adjustable with respect to guide 18a as by means of a screw .23. The screw 23 may be carried by a removable cover plate 24.

Thecrosshead 19 is provided with acarn slot QShaving a portion 26 of restricted uniform width extending right .angularly to guide 18a and piston rod 7. The slot 25 also has a portion27 of greater width, one wall 28 of which extends in substantial axial alignment with piston rod 7. Portion 27 also hasa wall 29 parallel to wall .28 and joined thereto by a quarter circular .or .arcuate wall 30, and a wall 31 forming .a continuation of one wall of portion 26.

.Cam slot 25 is engaged .by a follower pin 32 eccen- ,trically carried by a gear wheel .33 .mounted on a shaft 34. Gear wheel 33 is arranged to .be constantly driven as by-rneans eta worm gear .35 carried by a shaft 36 -rotated by a motor 37.

In operation, it will be apparent that a compressive or cooking action onspringlZ will be effected in response to rotation of gear wheel .33 from point D to point A, during which movement follower pin 32 will traverse portion 26 of the cam slot to move crosshead .19 against the spring and cause such cocking action. At point .A, pin 32 is suddenly released from slot portion .26 to permit a rapid pressure stroke of the piston under theaction of spring 22 and crosshead 19. Following such stroke, pin 32 traverses the enlarged portion27 of the ,cam slot.

The operation of the mechanism described is diagrammatically represented in Figure :5 whichis sealed for a piston with a 1%" overall stroke, a /6 effective stroke and a 4;" diameter cylinder.

Pigments such as sawdust, corkgranules, vermiculite, flock, chafi and sand, may be mixed with a carrier which need not be of the normal low viscosity type. The size of the pigment particles need be only small enough so that upon rather violent agitation a homogeneous slurry is formed. The supply tank '5 is charged with a mixture of pigment and carrier which flows through intake 4 into mixing chamber 2. Mixing of this slurryis accomplished in two ways. The motion of the piston within the chamber causes agitation ofthe mixture and also as indicated in Figure 5, in the cross-hatched area EFG,'the piston action causes rather violent reverse "flow from the mixing chamber into the cylinder, agitating the mixture further just before discharge.

When "follower pin 32 rotates into position .A, as indicatedin Figures 1 and 5, the spring (20, which has been cocked during the reverse or suction stroke of .the piston, is released and the crosshead 19 and the piston are moved ahead rapidly. The increasing volume of piston rod within the mixing chamber displaces some of the slurry, as indicated by area AB'B. At B, the piston enters the cylinder and imparts a velocity BC to the increment -.of

slurry within the cylinder opening, the resilient nozzle lips 15 and 16 and discharging the increment from the cylinder area "BHD'. When .the follower pin 32 reaches point D'the velocity of the piston iszero and the nozzle lips close. The suction stroke of the piston begins and the slurry behind the piston is pushed out into the mixing chamber area DEE. At E, the piston leaves the cylinder and slurry rushes violently into the cylinder, as indicated by area EFG, because of the low pressure left by the piston movement in the closed cylinder chamber.

greases Throughout the suction stroke D'G the spring 20 was maximum. This acceleration decreases linearly due to the force of resistance ofi'ered by the slurry on the piston head until the follower pin 32 reaches a point between B and D' where it engages the crosshead 19 and exerts a force transmitted to the piston which slows the rate of decrease of acceleration of the piston, as shown by line HS, caused by the force of the slurry on the piston head. At point D the piston is instantaneously stationary and thus has no acceleration.

Referring to the liquid acceleration curve, when the follower pin 32 reaches point B, the piston enters the cylinder and the velocity BC is immediately imparted to the increment of slurry in the cylinder. The liquid acceleration curve runs from zero at B to a very high value, represented at C, then almost immediately back to the piston acceleration curve at H. The value of C is approximately proportional to the mass of the reciprocating assembly. The piston 6, piston rod 7 and crosshead 19 provide a large mass which, being accelerated by the spring, exerts a force which imparts a high acceleration to the increment of slurry within the cylinder.

The piston acceleration-spring loaded curve is directly applicable to the conventional pump. Since in the conventional pump the fluid acceleration is greatest when the velocity is a minimum, and there is no acceleration when the velocity is greatest, a very lazy discharge is effected. This is clarified by considering the relationship F =Ma. At the time when the velocity is greatest and thus the mass is greatest, there is no acceleration and thus no force and no impact. Further, in the conventional pump the velocity of the liquid into or out of the cylinder starts at a minimum and builds up to a maximum then drops off to zero gradually. The slow starting velocity permits separation in the slurry giving a non-uniform coating.

in the present invention the maximum acceleration BH' occurs at the same time as the maximum velocity BC giving a very high impact to the slurry against the nozzle, causing the resilient nozzle lips to open and the uniform slurry to be discharged at a high velocity. The slurry is discharged immediately after a period of extreme agitation that is through about 120 of rotation from E to B, thus ejecting a homogeneous mixture which will form a uniform coating of consistent composition.

Figure 4 shows a second form of nozzle structure. Two pairs of lips 39 are arranged in a flexible disc 38 in a right angled intersecting relation. The support plate 40 has corresponding slots 41. The disc 38 and plate 40 maybe moulded together as a substantially integral part. It will be recognized that any number of slots radiating from a common center or otherwise can be used to give different patterns to the material being ejected. Any quick acting mechanism which is opened in response to pressures from within the cylinder is construed to fulfill the requirements for the nozzle of the present invention.

What I claim is:

l. A device for spraying a slurry of massive particles of solid material in a liquid carrier comprising a piston, a mixing chamber for said slurry reciprocally receiving said piston to cause agitation of said slurry, a cylinder having an open end communicating with said chamber and arranged to reciprocally receive said piston, said mixing chamber having an intake for said slurry, a pressure-operable nozzle normally closing the other end of said cylinder, means for loading said piston to impart a pressure stroke in one direction thereto, comprising a spring exerting pressure on the piston in said one direction, and means for compressing said spring to cock the same, and means for releasing said compressing means, said pressure stroke causing entry of said piston into said cylinder, said nozzle being openablc by force transmitted to the slurry in the cylinder by the piston in response to said pressure stroke, and means for imparting to the piston a suction stroke in the opposite direction to effect closure of said nozzle and an inrush of slurry from the mixing chamber into said cylinder.

2. A device for spraying a slurry of massive particles of solid material in a liquid carrier comprising a piston, a mixing chamber for said slurry reciprocally receiving said piston to cause agitation of said slurry, a cylinder having an open end communicating with said chamber and arranged to reciprocally receive said piston, said mixing chamber having an intake for said slurry, a pressure-operable nozzle normally closing the other end of said cylinder, means for loading said piston to impart a pressure stroke in one direction thereto, comprising a piston rod carrying the piston, a member fixed to said rod, a guide slidably supporting said member, a spring bearing on said member to urge the piston in said one direction, said member having a cam slot therein, a Wheel having a cam follower pin extending into said slot, means for continuously rotating said wheel, said slot having a narrow portion extending right angularly to the axis of said rod, and a wide portion extending parallel to the axis of said rod, said pressure stroke causing entry of said piston into said cylinder, said nozzle being openable by force transmitted to the slurry in the cylinder by the piston in response to said pressure stroke, and means for imparting to the piston a suction stroke in the opposite direction to effect closure of said nozzle and an inrush of slurry from the mixing chamber into said cylinder.

3. A device for spraying a slurry of coarse particles of solid material in a liquid carrier comprising a piston, a mixing chamber for said slurry reciprocally receiving said piston to cause agitation of said slurry, a cylinder having an open end communicating with said chamber and arranged to reciprocally receive said piston, said mix ing chamber having an intake for said slurry, a pressureoperable nozzle normally closing the other end of said cylinder, pressure means acting on the piston to impart a rapid pressure stroke thereto, the movement of said piston during said pressure stroke being from within the mixing chamber to within said cylinder to cause agitation of the slurry in said chamber and propulsion of the slurry through said cylinder and nozzle, means for moving said piston in the opposite direction against the action of said pressure means to effect a suction stroke thereof in reverse extent to said pressure stroke, said suction stroke causing agitation of the slurry in said chamber and cylinder, and power means for successively and continuously actuating said pressure means and piston moving means to cause successive pressure and suction strokes of the piston.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain of 1908