GB2484694A

GB2484694A - Mixing extruded materials

Info

Publication number: GB2484694A
Application number: GB1017704.6A
Authority: GB
Inventors: Paul Evans; Urs Joos; Frank Wolff
Original assignee: CHEMFIX PRODUCTS Ltd
Current assignee: CHEMFIX PRODUCTS Ltd
Priority date: 2010-10-20
Filing date: 2010-10-20
Publication date: 2012-04-25
Anticipated expiration: 2030-10-20
Also published as: GB2484694B; GB201017704D0

Abstract

Apparatus for mixing and dispensing materials extruded from a container comprises a mixer tube (1, Fig. 1) defining an axis (X-X) between a first end (1A, Fig. 1) and second end (1B, Fig. 1), a mixer part 4 which circumferentially deflects and mixes the materials and a mixer part 3 for diverting the materials radially outward before being acted upon by the circumferentially deflecting mixer part. The first end of the mixer tube attaches to a cartridge or other container for the separate materials, whilst the second end of the mixer tube expels the mixed materials. The mixer part which diverts the materials radially may comprise radial channels (9, Fig. 3), each designed to divert the materials radially outwardly to an outlet 10 within the mixer tube. Preferably, the outlet from each radial channel faces at least partly in an upstream and/or radially outward direction. The mixer parts which radially and circumferentially deflect the materials can be a single moulding of synthetic plastics material.

Description

Mixing Extruded Materials The present invention relates to apparatus for mixing and dispensing materials as they are extruded from a cartridge or other container. After mixing and dispensation, these S materials react together. In most cases the materials consist of adhesive and a hardener that causes the adhesive to set soon after mixing.

The invention particularly relates to apparatus of the type that comprises a mixer tube or nozzle defining an axis extending between a first end, for attachment to a cartridge (or other container) for the separate materials, and a second end for expelling the mixed materials. The mixer tube contains means (usually referred to as a mixer "flight") for mixing the materials by a process that involves deflecting them circumferentially with respect to the axis, The separate materials to be mixed can be contained in twin compartments provided with individual dispensing plungers such as described for example in patent specification US 5033650. Alternatively, eg as described in patent specification GB2455372A, they can be contained in a so-called "chub" manufactured from flexible sheet synthetic plastics material and defining twin compartments. In this latter example, the chub is loaded into a cartridge designed to fit into a conventional extrusion gun. In both of these systems the different materials, after leaving the individual compartments, pass into a mixer tube containing a mixer flight which acts to mix the two materials together.

Conventionally, the mixer flight has used a spiral element to cause the two materials to flow along a spiral path and thereby to become mixed together. Sometimes a series of spiral elements are arranged alternately with opposite handedness to improve the mixing effect. The surfaces of the spiral elements define a constant angle with the axis of the mixer tube.

A problem with present mixers is that, to achieve satisfactory mixing, they need to be longer than that of a standard cartridge. This presents a packaging problem because for compactness, it is often desirable to package the mixer tube and cartridge alongside each other. Furthermore, the length of the mixer tube and the mixer flight within it results in the need for considerable pressure to extrude the cartridge contents making it difficuh to use. Yet another problem arises from wastage of material left to harden in the mixer tube when the cartridge, or other container for the unmixed components, is empty; the amount of waste being directly proportional to the length of the mixer tube.

According to the invention, in apparatus of the aforementioned type, the mixer tube also contains radial deflecting means located upstream of the circumferential deflecting means and defining a path or paths arranged to divert the materials radially outward before being acted upon by the circumferential deflecting means.

Using this technique the materials to be mixed are subjected to a preliminary mixing process during which they are first diverted from a forward axial direction to a radial direction and then, preferably, back to a reverse axial direction before undergoing the conventionally, alternating, circumferential diversions. Tests have shown that this combination of direction changes allows the required degree of mixing to be achieved in a mixer tube of significantly shorter length and offering less resistance to flow than The radial and circumferential deflecting means can be embodied as separate parts, eg separate mouldings of synthetic plastics material, forming a two-part flight.

Ahernatively, they can be formed integrally as a single-piece flight. The radial deflecting means preferably has an axial channel which initially receives the materials to be mixed, and which leads into separate radial channels, each arranged to guide the materials outwardly to an outlet within the mixing tube.

The outlet from each of the radial channels can be an open side thereof, preferably facing at least partly in an upstream direction, i.e. in a direction that is the reverse of the general axial flow. In this way the materials are caused to undergo changes of direction from forward to radial to backward and then to forward.

One way in which the invention may be performed will now be described by way of example with reference to the accompanying drawings in which:-Fig.1 is an axial cross-section of a mixer tube and flight constructed in accordance with the invention; Fig. 2 is similar to Fig 1 but shows the mixer flight in side elevation; Fig. 3 is a detail of the lower part of Fig 1; Fig. 4 is a detail of the lower part of Fig 2; and Fig. 5 is a perspective view of the mixer flight.

Referring to the drawings, the illustrated apparatus comprises a conventional nozzle-shaped mixer tube 1 having an axis of symmetry X -X. The mixer tube 1 has a relatively wide end 1 A (shown as the lower end in the Figures) and tapers to a relatively narrow upper end lB. The lower end 1A defines an internal cylindrical surface 1 C and an internal screw thread adapted to engage with a complementary external thread of a cartridge (not shown).

Held within the mixer tube 1, is a mixer flight 2 which is injection moulded in one piece from synthetic plastics material. Referring to Fig. 5, the mixer flight comprises a first part 3 and a second part 4.

The mixer part 3, which will be referred to as the "radial deflecting means," has a cylindrical axial boss 5 defining a channel 6 with an inlet 7. The boss 5 is of reduced external diameter at the upstream end. The channel 6 leads axially to its downstream end where it joins four arms 8 defining distribution channels 9 (Fig. 4). Each distribution channel 9 leads radially outwardly to a free end 10 immediately adjacent the internal surface 1 C of the mixer tube 1. Each channel 9 is open on its upstream-facing side. That open side faces into a space 11 between the boss 5 and the internal wall surface 1C of the mixer tube 1.

The mixer part 4 is designed along conventional principles and will be referred to as the "circumferential deflecting means" because it rotates the materials circumferentially about the axis X -X. The circumferential deflecting means 4 defines nine mixer elements, each indicated on Fig. 5 by reference numeral 12. Each of these mixer elements has the shape of an auger that makes a single 360 degree turn between a leading edge (e.g. edge 13) at its upstream end and a trailing edge (e.g. edge 14) at the downstream end. Ahernate mixer elements have alternate handedness and are staggered, rotationally about the axis X -X, so that the trailing edge 14 of one mixer element is, in this particular example, 90 degrees out of alignment with the leading edge 13 of the next mixer element. In alternative embodiments, angular displacements of anywhere between 40 degrees and 140 degrees have been found to give good results The materials to be mixed are contained in separate compartments of a cartridge (not shown). Immediately before use, these compartments are opened and the cartridge is screwed onto the mixer tube 1. For one particular specialist designs of cartridge, an opening of one of the compartments fits over the reduced-diameter end of the boss 5.

When the materials are extruded from the cartridge they flow partly into the inlet 7 of the channel 6 and partly into the annular space surrounding the boss.

The materials flowing into the channel 6 are diverted from the axial direction into four radial directions, through respective channels 9 defined by arms 8. The material being guided by the arms 8 can escape from the latter only by flowing, as shown by arrows on Fig 5, into the path of the remaining material so that it follows paths upstream against the flow of the remaining material, circumferentially outward over opposite sides of each arm 9 and then axially downstream with the rest of the flowing material.

In summary, the effect of the radial deflecting means 3 is to cause one part of the flowing materials to follow a convoluted course: a) downstream in an axial direction through the boss 5; b) radially outward through the four arms 8; S c) in eight streams, around opposite sides of the arms 8; and d) joining into the remaining part of the flow in the downstream axial direction.

This convoluted flow course creates a high degree of initial mixing. The partially mixed materials are then further mixed by the second mixer part 4. First, the flow is divided into two streams by the leading edge 6 of the first mixer element S which are caused to swirl circumferentially in an anticlockwise direction (as viewed in the direction of the flow). This process is repeated, (in the opposite direction) clockwise by the second mixer element; and so on, to form a homogenous mixture which passes into the nozzle-shaped end-portion 1A. Here, the mixture assumes a smooth laminar flow before being expelled as a bead from the nozzle-shaped end. Because the end portion 1A is tapered, it is possible to select the size of the bead by cutting off an appropriate length of the tapered portion 1A.

Although the mixer part 4 is designed on principles of a conventional flight, it is considerably shorter and has fewer elements than is conventional. Indeed the total length of the two parts 3 and 4 is shorter and provides less resistance to flow than conventional mixer flights whilst still achieving a sufficiently thorough mixing effect.

Because of this relative shortness of the mixer flight, the mixer tube also is relatively short, resulting in reduced wastage of residual mixture in the tube when the cartridge is empty.

Claims

Claims 1. Apparatus for mixing and dispensing materials extruded from a container, the apparatus comprising a mixer tube defining an axis extending between a first end, for attachment to a cartridge or other container for the separate materials, and a second end for expelling the mixed materials, and a circumferential deflecting means contained within the mixer tube, the deflecting means being designed to mix the materials by deflecting them circumferentially with respect to the axis, characterised in that the mixer tube also contains radial deflecting means located upstream of the circumferential deflecting means and defining a path or paths arranged to divert the materials radially outward before being acted upon by the circumferential deflecting means.
2. Apparatus according to Claim 1 characterised in that the radial deflecting means defines radial channels, each designed to divert the materials radially outwardly to an outlet within the mixer tube.
3. Apparatus according to Claim 2 characterised in that each radial deflecting means defines an axial channel from which the radial channels extend.
4. Apparatus according to Claim 2 or 3 characterised in that outlet from each radial channel faces at least partly in an upstream direction.
5. Apparatus according to Claim 2 or 3 or 4 characterised in that outlet from each radial channel faces at least partly in a radially outward direction.
6. Apparatus according to any preceding Claim characterised in that the radial and circumferential deflecting means are defined by a single moulding of synthetic plastics material.Amendments to the claims have been filed as follows Claims 1. Apparatus for mixing and dispensing materials extruded from a container, the apparatus comprising a mixer tube defining an axis extending between a first end, for attachment to a cartridge or other container for the separate materials, and a second end for expelling the mixed materials, a circumferential deflecting means contained within the mixer tube, the circumferential deflecting means being designed to mix the materials by deflecting them circumferentially with respect to the axis, and a radial deflecting means located upstream of the circumferential deflecting means, the radial deflecting means defining radial channels to divert the materials radially outward to an outlet within the mixer tube before being acted upon by the circumferential deflecting means; characterised in that the outlet from each radial channel faces at least partly in an upstream direction.y-15 2. Apparatus according to Claim 1 characterised in that each radial deflecting means defines an axial channel from which the radial channels extend.Q") 3. Apparatus according to Claim 2 characterised in that outlet from each radial channel faces at least partly in a radially outward direction.4. Apparatus according to any preceding Claim characterised in that the radial and circumferential deflecting means are defined by a single moulding of synthetic plastics material.5. Apparatus substantially as illustrated in figures 1-4.