NL1019690C2 - Cryogenic grinder for carbon dioxide particles, has grinding mechanism formed by nip between two ribbed rolls - Google Patents

Abstract

Particles are ground in a nip between two ribbed rolls (5). A grinder for cryogenic particles comprising solid carbon dioxide has a grinding mechanism comprising two ribbed rolls forming a nip in which the particles are crushed.

Description

The invention relates to a pulverizer for cryogenic particles consisting of solid carbonic acid. With the device, it is possible to crush cryogenic particles having a size of about 3 by 3 by 7 os millimeters to sharp-edged grit with a size of about 1 millimeter.

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Hardener for hard cryogenic particles.

It has been found that the processing of surfaces by blasting with hard carbonic acid particles is particularly effective. When processing delicate objects, the particle size is important for the result to be achieved. The Dutch patent NL-C-194233 describes a method for pressing 10 hard cryogenic particles from carbon dioxide snow. These particles are very suitable for removing dirt and paint, for example. However, components from the electronics do not tolerate this operation. It has been found that jets with cryogenic particles that have been crushed to a size of approximately 1 millimeter provide very good cleaning without damaging the object. It has been found that cryogenic particles obtained with the device of NL-C-194233 can be crushed very efficiently by their hardness, whereby little unusable powder is formed.

The invention relates to a pulverizer consisting of a pair of rollers rotating against each other. The particles are crushed between the rollers and the gap between the rollers determines the size of the particles to be obtained. Because the cryogenic particles have a temperature of approximately minus 80 degrees Celsius, a number of provisions are required to obtain a regular production. The choice of materials is of great importance, and the cold flows must be taken into account in the construction to prevent freezing. Insulation is important in order to limit sublimation as much as possible.

An embodiment of the invention is described with reference to the drawing.

FIG. 1 Shows cross-section of the pulverizer.

FIG. 2 shows section II - li of FIG. 1.

FIG. 3 shows a section through one of the rollers.

The pulverizer is made up of two frame plates (1) and (2) made from, for example, 20 millimeters of modified polytetrafluoretylene, abbreviated POM. In these frame plates (1) and (2) slotted plates (3) and (4) are placed. Plates (3) and (4) extend from the top of Frame (1) and (2) to a distance of 0.2 to 0.5 millimeters from the rollers (5). Frame (1) and (2) with plates (3) and (4) thus form a bunker for the cryogenic particles to be crushed. The frame is fixed with columns (6).

In Frame (1) and (2) provisions are made for the shafts (7) of the rollers (5). For one of the shafts, a setting option (not shown) is available to adjust the gap between rollers (5).

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Mounted on the shaft end of shafts (7) is a gear (8) with a diameter and toothing such that the two gear wheels (8) are always engaged and the rollers rotate against each other and at the same speed. One of the gear wheels (8) is coupled to a motor (10) with coupling (9). Motor (10) is a speed-adjustable motor, preferably a pneumatic one. The rollers (5) consist of a shaft (7) surrounded by the roller body (11) made of modified polytetrafluoroethylene. It is important that the diameter of the shaft is no more than 30% of the diameter of the roller. Grooves (12) are provided in the circumference of the rollers which have a mutual distance between 1 and 4 millimeters, preferably 1.5 millimeters with a depth of approximately 1 millimeter. The diameter of the rollers is between 10 and 70 millimeters, preferably 50 millimeters.

It has been found that a speed of 300 revolutions per minute gives an optimum result. By controlling the motor (10) in revolutions, the yield can be adjusted to the consumption during blasting. In practice, the speed will be between 50 and 500 revolutions per minute,

The pulverizer can be mounted on the hopper of the blasting device and the motor (10) can be controlled from the blasting device.

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Claims (5)

Crusher for crushing cryogenic particles consisting of solid carbonic acid, characterized in that the pulverizer mechanism consists of two mutually rotating ribbed ox rollers (5), wherein the cryogenic particles are crushed in the gap between the rollers (5). Cryogenic particle pulverizer according to claim 1, characterized in that the rollers (5) are coupled to gears (8) mounted on the shaft ends of shafts (7), the gap between the rollers (5) being adjustable between 0 and 3 millimeters . 10 Cryogenic particle pulverizer according to claims 1 and 2, characterized in that the rollers (5) consist of modified polytetrafluoretylene and are provided on the circumference with shallow grooves (12) with a distance between 1 and 4 millimeters, preferably 1, 5 millimeters, and wherein the rollers (5) have a diameter between 30 and 70 millimeters, preferably 50 millimeters. Cryogenic particle pulverizer according to claims 1, 2 and 3, characterized in that the rollers (5) are driven with a speed-adjustable motor (10) and rotate at a speed between 50 and 500 revolutions per minute. 20 Cryogenic particle pulverizer according to claim 1, 2, 3 and 4, characterized in that all parts that come into contact with cryogenic particles are made from thick-walled insulating plastic. * * * *! ; i. ^ "c