Cyclonic mixer

Abstract: A cyclonic mixer comprises a pair of concentric tubes (12, 16) having an inlet and an outlet. The outer tube is closed at either end, and the inner tube (16) has a plurality of holes (38) with compound angles designed to impart a swirling motion of the air admitted into the interior of the inner mixing tube (16). The holes are judiciously located around the inner tube (16) for creating a swirling pattern. The inlet of the tubes accepts dry particles of two or more different compositions intended to be mixed into the mixer, and the outlet leads the mixture to the next station utilizing the mixture. Air is admitted internally of the outer tube (12) to feed the plurality of holes (38), and the force of the air can be controlled to control the transport of the mixed particles.

Description: This invention relates to mixers and particularly to mixers that mix at least two dry powders or granular materials and transport them by the judicious insertion of air jets located in the mixer casing. As is well known to one skilled in the art of formulating and applying coatings, it can be desirable to introduce reinforcing materials such as cork, glass, etc. or metallic powders or granular or other filler materials into a coating applied to the surface of a substrate. For example, US 5565241, granted to Mathias et al on 15 October 1996 entitled "Convergent End-Effector", having common co-inventors and assigned to the current applicant, relates to a spray gun for coating materials on the surface of a substrate. This type of spray gun is used to apply a coating which includes reinforcing material (cork and glass) added to a liquid resin in a convergent stream formed by the end-effector. In this method of applying the coating, the glass and cork are transported by air to the end-effector where they are mixed with the liquid resin downstream of the nozzle of the end-effector. Each of the reinforcing materials is individually transported from the eductor, and they are mixed prior to being introduced to the liquid resin. DE-A1144090 discloses a mixere applying air to the mixing chamber. It would be desirable to provide an efficient, sturdy and long-lasting mixer that not only mixes the components but has the capability of transporting the mixed components through the mixer to the next station where it is intended to be utilized. Thus, an object of this invention is to provide an improved mixer for mixing at least two different dry particles. According to the invention, there is provided a mixer comprising a pair of concentric tubes with inlets and outlets, where the inner tube includes a plurality of discrete holes disposed in a judicious pattern for injecting air from holes formed in the inner tube to create a helical flow pattern for effecting mixing of different components. In one embodiment, the components are transported independent of the mixing air, and in a second embodiment the mixing air is the sole mechanism for transporting the mixed particles. While in the first embodiment the particles are delivered to the mixer in a flow stream, and are transported by compressed air, the mixing air injected by the mixing holes contributes to the transporting of the mixture. A preferred feature of this invention is the utilization of mixing holes that are judiciously disposed and include compound angles to impart a swirling motion to the incoming air prior to being introduced into the body of the mixer. Preferred embodiments of the present invention will now be described by way of example only arid with reference to the accompanying drawings, in which: Fig. 1 is a cut-away view partly in section and partly in elevation illustrating a first embodiment of the present invention; Fig. 2 is a plan view of the mixer shown in Fig. 1; Fig. 3 is a sectional view taken along the lines 3-3 of Fig. 1; Fig. 4 is a partial view on an enlarged scale showing the mixing hole, to illustrate the compound angle of the mixing hole; Fig. 5 is a partial view illustrating the critical dimensions of the mixer for a given mixer size; and Fig. 6 is a view of another embodiment of the mixer, with a single exit for the mixed components. While this invention is being described for use with an end-effector of the convergent spray technology as disclosed in US 5307992, US 5565241, and US 5579998, all of which are incorporated herein by reference, it is to be understood that this invention has particular utility for any application where it is desirable to transport and mix at least two different dry particle or granular ingredients. The use of the mixer of the present invention is particularly efficacious in applications of the convergent spray gun where fillers are injected into a liquid convergent spray produced by an end-effector prior to being applied to the surface of a substrate. For an understanding of this invention, reference is made to the Figures, which show the mixer generally illustrated by reference numeral 10. The mixer has a cylindrical or tubular outer housing 12 which surrounds an inner housing 16, which is also cylindrical or tubular. The inner and outer housings are concentric and coaxial relative to a centre line 14. The outer housing 12 provides a straight through central passage 18 and is fitted at its inlet end 20 in any suitable manner with a tube 22 that is bifurcated to include a pair of branch lines 24 and 26. A similar tube 28 with branch lines 30 and 32 is suitably fitted at the discharge end 34 of the outer housing 12. As illustrated in Fig. 1, the ingredients A and B are admitted into the mixer 10 and are transported by air. In some applications, the air is sufficient to-transport the ingredients into and out of the mixer and to the ultimate destination of the mixed ingredients. In those applications where this transport is not sufficient to transport the mixed ingredients to the ultimate destination, the air used for mixing will serve this purpose as will be described in further detail hereinbelow. As best seen in Fig. 1, the inner tube has a plurality of holes 38 that are formed and located in order to obtain the desired mixing characteristics of mixer 10. The holes are formed with compound angles. As seen in Fig. 4, the angle in one plane is substantially 30° relative to the horizontal axis taken through centre line 14. Ten holes are provided around the circumference of tube 16 and are spaced substantially 0.88 inches (22.4 mm) apart in the tube 16 which is substantially 12.75 inches (325 mm) in length. The other part of the compound angle is shown in Fig. 5, where the angle of the hole is substantially equal to 30° relative to the centre line 14. In a particularly preferred embodiment, the first hole of holes 38 closest to the inlet 20 is spaced substantially 2.05 inches (52.1 mm) therefrom and the last hole of holes 38 closest to the outlet 34 is substantially 2.50 inches (63.5 mm) therefrom. The inlet end and outlet end of the outer tube 12 are closed off by suitable inserts 40 and 42 respectively and define with the outer surface of inner tube 16 an annular cavity 44 that receives air from an inlet pipe 46. The air admitted into the cavity 44 serves to supply air under pressure to each of the holes 38. The compound angle of each of the holes 38 is selected to impart a swirling motion to the incoming air as it is discharged internally into the centre of tube 16. The spacing of the holes 38 around the circumference of the tube 16 serves to provide a helical path to the air as represented by the arrow 50 (see Figure 6) as it progresses from the inlet 20 to the exit 34 of mixer 10. This provides an efficacious mixer for the two ingredients that are mixed within mixer 10 and transported through pipe 30 to the end-effector (not shown). As is apparent from the foregoing, the pressure of the mixing air can be selected to provide the transporting force of the mixed ingredients from the mixer to the next station. For example, the powder ingredients can be introduced through hoppers or other well known feeders directly into the interior of mixer 10 and the mixing air inserted through holes 38 would not only provide the mixing but would also provide the medium to transport the mixed ingredients. Fig. 6 shows another embodiment where the cyclonic mixer 10 is identical to the cyclonic mixer depicted in Fig. 1 except that the mixed components exit in a single discharge conduit 56. As shown by the arrow 50, the cyclonic mixer serves to impart a helical motion to the mixed stream and conducts the stream from the entrance to the exit. Obviously, in applications where the components are not fed to the mixer by some transport mechanism, the mixer itself can utilize a pressurized source to effectuate the motion. Although this invention has been shown and described with respect to detailed embodiments thereof, it will be appreciated and understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the scope of the invention, as defined in the claims.

Claims: A mixer for mixing at least two different ingredients in the form of dry powders or granular materials, including a outer housing (12) having a straight through passage (18), an inner housing (16) within said outer housing (12) having a straight through passage and being radially spaced from said outer housing to define an annular passage therewith and having an inlet and an outlet, means (40, 42) for closing off the ends of said annular passage to define a cavity (44) for receiving mixing air, a plurality of apertures (38) formed in said inner housing (16) for admitting air into said straight through cavity of said inner housing (16), each aperture (38) having a contour for imparting a swirling motion to the air passing therethrough, said plurality of apertures (38) being disposed in said inner housing (16) to define a helical path extending from the inlet of said straight through passage of said inner housing, means (46) for admitting air into said cavity (44) and means (22, 24, 26) for admitting said two different ingredients into said inlet. A mixer as claimed in claim 1, wherein said inner housing (16) is a tube. A mixer as claimed in claim 1 or claim 2, wherein said apertures (38) are formed with compound angles. A mixer as claimed in any preceding claim, wherein the apertures (38) are equally spaced around the circumference in a helical pattern. A mixer as claimed in claim 1 wherein said apertures (38) are formed with compound angles, said apertures (38) are 30° relative to the horizontal axis (14) of said mixer (10), and the apertures (38) are evenly spaced around the circumference of said inner housing (16) in a helical pattern.

Inventors: HALL TERRY L, MATHIAS DAVID D, SCARPA JACK G, HALL, TERRY L., MATHIAS, DAVID D., SCARPA, JACK G.
Applicants: USBI CO, USBI, CO.
Application year: 1998
Main classification: B01F5
IPC codes: B01F15, B01F3, B01F5, B05B7, B01F13