GB2223956A - Mixing head - Google Patents

Abstract

There is disclosed a mixing head (10) comprising an inlet block (11) having an inlet (12) for receiving the components which are to be mixed and then dispensed. There is also an outlet block (13) having an outlet (14) for dispensing the mixed components, after travel along a plurality of flow passages extending between the inlet block (11) and the outlet block (13). Elongate mixers in the form of styrators are arranged in at least some of the passages, and communicating ports (17) arranged in each block (11 and 12) communicate the passages with each other in such a way that a reversing path of travel is defined between the blocks (11, 13) for the components admitted via the inlet (12) prior to discharge via the outlet (14). <IMAGE>

Description

MIXING HEAD This invention relates to a mixing head for mixing liquid or semi-liquid components together and for dispensing the mixed components.

The invention has been developed primarily in connection with the mixing together of a synthetic resin with an accelerator or curing agent, and for dispensing the mixture as a sealant which cures or sets over a period of time following application to any particular joint requiring sealing.

One example of use of such a sealant is in the sealing of the edges of factory-built double glazed units. To form a double glazed unit, two panes of glass are assembled in spaced-apart relationship by means of four spacer bars which are arranged one between each pair of facing edges of the panes of glass. The spacer bars hold the panes of glass so as to form a double glazed unit, and each bar is located slightly inwardly of the glass edges thereby leaving a small rectangular space which requires filling with a suitable sealant.

The sealants used in double glazed units must be capable of application in a reliable manner so as to fill and to seal all voids, and therefore must remain fairly easy to handle for a sufficient time to enable application to take place before curing or setting of the sealant commences. An initial set usually occurs after a few hours, but the full curing can take quite a lot longer.

After the sealant has set, it is important that it should function as a sealant to exclude ingress of water or air into the space between the panes of glass, and yet it must retain a sufficient degree of flexibility to enable it to maintain its sealing action despite relative minor movements taking place between the panes of glass in service, usually as a result of heat dependent expansion and contraction.

One sealant which is widely used is known as a "polysulphide" sealant, and this has the advantage of relatively easy mixing of the base component and a suitable curing agent, and also ready application to joints requiring sealing. However, the long term durability of polysulphide sealants is a problem, and the manufacturers of double glazed units would prefer to use polyurethane sealant material as it has superior operating performance in service.

However, while polyurethane sealants perform much better when properly mixed and applied to a joint requiring sealing, there are considerable handling problems in the mixing of the base component and its curing agent, and in the dispensing of the mixture.

Relatively small amounts of curing or setting agent, known as an "accelerator", are required, to be introduced into the base component, but to obtain a proper setting throughout the applied mixture, it is essential that the accelerator should be dispersed as uniformly as possible throughout the base component.

To date, the only way to achieve a suitably uniform distribution of the accelerator throughout the base component has involved the use of a very lengthy pipe mixing arrangement which comprises an inlet to an initial mixing head, known as a "styrator11, in which initial mixing of the components takes place, a length of pipe approximately 8 foot long which receives the partial mixture issuing from the styrator, and a final mixing head or styrator which receives the mixture from the pipe and further mixes the components before dispensing the mixture.

The 8 foot length of pipe is necessary to allow the initial mixture of the components formed in the first styrator to unwind to a certain extent, since the styrator applies a twisting action to the components. This unwinding is necessary, and over this substantial distance, before feeding can take place of the partially formed mixture to the second styrator, which then completes the mixing process.

Evidently, the handling of the dispenser is cumbersome, by virtue of the considerable length of pipe between the two styrators, and there are also problems in the flushing out of the system when this is required. In view of the irreversible chemical action which takes place following mixing of the components, it is essential to flush out the system during and at the end of a working shift, if the system is going to be left idle for any appreciable length of time e.g. more than half an hour.

The flushing out of the system requires the use of a special solvent, and the components stored in the two styrators and in the length of communicating pipe must be discharged, which represents a substantial volume of waste material. The safe disposal of the waste material can also be a problem. In addition, over a period of time, the costs of solvents represents a significant additional cost to the operation.

Therefore, given that there is a clear demand by users for polyurethane sealants to be made available, there is a clear need to provide a mixing and dispensing head which is (a) less cumbersome in operation than the existing system (b) operates efficiently to mix the base component and the triggering or accelerating agent (c) does not require the use of a special solvent to flush out the system and (d) is less wasteful of material during flushing-ot.

According to the invention there is provided a mixing head for mixing liquid or semi-liquid components and for dispensing the mixed components, the head comprising: an inlet block having an inlet for receiving the components which are to be mixed and then dispensed; an outlet block having an outlet for dispensing the mixed components; a plurality of flow passages extending between the inlet and outlet blocks; elongage mixers arranged in at least some of said passages; and, comunicating ports arranged in each block to communicate the passages with each other in such a way that a reversing path of travel is defined between the blocks for the components admitted via the inlet prior to discharge via the outlet.

Thus, the components can undergo a thorough mixing as they travel along the path of travel between the blocks, and in view of the reversing direction of the path, the path of travel is considerably greater than the distance between the blocks, thereby making the mixing head of a short overall length so that it is easy to handle.

Also, in the event of the head requiring flushing out (when one component is a base component in relatively large proportion and the other is an active component in a relatively smaller proportion which promotes a chemical reaction upon mixing), the supply o the active component can be terminated and the system flushed out using the base component only.

In use of the mixing head for mixing a chemical resin component and a curing or setting component, it is very important that all of the mixed and partially mixed components should be flushed out when the system is inoperative and to be left idle for a certain time more than a predetermined minimum, since otherwise the mixture may become set in situ. Therefore, the system can be flushed out using the base component only.

A mixing head according to the invention is particularly suitable for use in mixing polyurethane resin and an accelerator, to produce a sealant suitable for use in sealing joints, such as along the edges of double glazed units.

Preferably, the ports are arranged so that a single reversing path is defined between the inlet and outlet blocks, and which will comprise an uneven number of traverses equal to at least three.

Conveniently, five passages are provided, at least three of which having an elongate mixer arranged therein, and the passages may each be formed by tubes or pipes detachably coupled at each end in a respective socket provided in the inlet block and the outlet block. Such an arrangement therefore provides a path of travel which is approximately five times as long as the distance separating the two blocks, and this therefore enables thorough mixing of the components to take place.

One embodiment of mixing head according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic and exploded illustration of a mixing head according to the invention for use in mixing and dispensing a sealant derived from a resin component and a setting or curing component; and, Figure 2 is a schematic block diagram illustrating the path of travel of the components as they undergo mixing within the head.

Referring now to the drawings, a mixing head according to the invention is designated generally by reference 10 and comprises an inlet block 11 having an inlet 12 for receiving the components which are to be mixed and then dispensed. There is also an outlet block 13 having an outlet 14 for dispensing the mixed components, after travel along a plurality of flow passages extending between the inlet block 11 and the outlet block 13.

Elongate mixers in the form of styrators 15 are arranged in at least three of the flow passages, which take the form of five tubes or pipes 16. Communicating ports 17, shown by dark lines in Figure 1, communicate the passages with each other in such a way that a single reversing path of travel is defined between the blocks 11 and 13 for the components admitted via the inlet 12 prior to discharge via the outlet 14.

In the illustrated embodiment, and as can be seen particularly from Figure 2, the reversing path of travel of the components, as they undergo successive mixing, comprise five traverses between each of the blocks, and this therefore enables the overall length of the mixing head to be kept sufficiently short that the head can be easily handled, while still providing a sufficient path of travel of the components that they can undergo thorough mixing before they issue as a mixture from the outlet 14.

When the system requires flushing-out at the end of a working shift, or any delay in operation more than a predetermined minimum time, the base component only can be supplied to the missing head so as to flush-out the system.

To enable the mixing head to be thoroughly cleaned out at regular intervals, each pipe 16 can be detachably coupled at each end with the inlet block 11 and the outlet block 13, by being received detachably in a respective one of sockets 18 provided in the blocks 11 and 13. The styrators 15 also can be readily removed for cleaning purposes, and it will be seen particularly from the illustration in Figure 1 that the styrators 15 are able to impart rotary action to the components, so that they undergo a thorough mixing, and the reversal of direction which takes place at the end of each traverse of the components will also promote further mixing of the components.

The illustrated embodiment of mixing head is particularly suitable for mixing a base component and a curing component for forming a polyurethane sealant for use in sealing joints, such as along the edges of double glazed units.

Claims (5)

1. A mixing head for mixing liquid or semi-liquid components and for dispensing the mixed components. the head comprising: an inlet block having an inlet for receiving the components which are to be mixed and then dispensed: an outlet block having an outlet for dispensing the mixed components: a plurality of flow passages extending between the inlet and outlet blocks: elongage mixers arranged in at least some of said passages; and.

comunicating ports arranged in each block to communicate the passages with each other in such a way that a reversing path of travel is defined between the blocks for the components admitted via the inlet prior to discharge via the outlet.

2. A mixing head according to Claim 1. in which the ports are arranged so that a single reversing path is defined between the inlet and outlet blocks. and which will comprise an uneven number of traverses equal to at least three.

3. A mixing head according to Claim 2. in which five passages are provided. at least three of which have an elongate mixer arranged therein.

4. A mixing head according to Claim 3. in which the passages are formed by tubes or pipes detachably coupled at each end in a respective socket provided in the inlet block and the outlet block.

5. A mixing head according to Claim 1 and substantially as hereinbefore described with reference to.

and as shown in the accompanying drawings.