GB2127316A - Static mixer - Google Patents

Abstract

A static mixer including a plurality of twisted vane elements (12) located end to end in a length of flexible pipe (10), the direction of twist of successive vane elements being of opposite hand and successive vane elements (12) being connected together loosely within the bore of the pipe by means e.g. inter-engaging notches (16) which permit their articulation and allow the pipe to flex. <IMAGE>

Description

SPECIFICATION Static mixer The invention relates to so-called static mixers for the mixing of liquids.

Static mixers of conventional construction comprise a plurality of twisted vane elements welded together end to end and inserted into a length of pipe. The developed shape of each vane element is a rectangle of a width which will extend completely across the bore of the pipe, the direction of twist of successive vane elements being of opposite hand so that, as a liquid passes along the pipe, it is subjected to shear in the plane of transition between each vane element and the next successive vane element.

Such mixers generally work quite well in a wide range of applications but are subject to various drawbacks. For example, since the length of pipe must be of necessity be a straight pipe there are practical limitations on the overall length of the mixer. Furthermore, the effective length of such a mixer cannot be varied so that having been designed for one particular application it cannot readily be adapted to suit another. The object of the invention is to provide a static mixer which will at least partly overcome such drawbacks.

According to one aspect of the invention, there is provided a static mixer including a length of flexible pipe and a plurality of twisted vane elements located within the bore of the pipe, the direction of twist of successive vane elements being of opposite hand, the successive twisted vane elements being connected together loosely within the bore of the pipe by means which permit their articulation and allow the pipe to flex. The means which connect the successive twisted vane elements together within the bore of the pipe may be constituted by a central notch in at least one end of each element, the notch having a width equal to the thickness of the material of which the vane elements are made, the arrangement being such that the end portion of the immediately adjacent vane element can be engaged with said notch.Both ends of each twisted vane element may be notched for the connection together of successive elements in an articulable manner. The twisted vane elements may be an interference fit in the bore of the pipe and may be located within the bore of the pipe by means of an abutment member at what, in use of the mixer, will be the downstream end of the pipe. The flexible pipe may be made of a synthetic plastics material and will preferably have braided wire reinforcement to enable the mixer to operate under relatively high internal pressure.

According to a further aspect of the invention, there is provided a method of making a static mixer, the method including the step of entering a plurality of separate twisted vane elements in turn into a length of flexible pipe. The twisted vane elements may be made by suitably twisting a relatively long length of strip material and cropping the vane elements from the pre-twisted strip, a subsequent step in the forming of the vanes being the forming of a notch in at least one end of each vane, the notch having a width equal to the thickness of the strip material of which the vane elements are made, the arrangement being such that adjacentvane elements can be engaged together end to end in articulable but non-rotatable relation.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings, of which Figure 1 is a perspective view of a static mixer embodying the invention, and Figure 2 is an exploded view illustrating two of the component parts of the mixer, this being drawn to a somewhat larger scale than Figure 1.

Referring now to Figure 1 of the drawings, the static mixer there illustrated includes a length of flexible pipe 10 and a plurality of twisted vane elements 12 located within the bore of the pipe and retained therein by means of an abutment member constituted by or including an annular sleeve 14 at what, in use of the mixer will be the downstream end of the pipe. As indicated in chain-dotted lines in Figure 2, the developed shape of each vane element is a rectangle, and the width of the rectangle is such as to extend completely across the bore of the flexible pipe into which the vane element is to be fitted. The vane elements have been made by suitably twisting a relatively long length of strip material and cropping off the almost finished vane elements from the pre-twisted strip. The direction of twist of successive vane elements are of opposite hand, as shown in Figure 2.Consequently, half of the vane elements are cropped from a length of strip material which has been pre-twisted with a clockwise twist and the other half have cropped from a length of strip material which has been pre-twisted with an anti-clockwise twist.

A final step in the forming of the twisted vane elements 12 has been the forming of a notch 16 in each end of each element, the arrangement being such that, as shown in chain-dotted lines in Figure 2, adjacent vane elements can be engaged together end to end in articulable but non-rotatable relation.

In use, a static mixer embodying the invention will operate in substantially the same manner as a conventional static mixer so that as liquid passes along the pipe it is subjected to shear in the plane of transition between each vane element and the next successive vane element. However, by virtue of the fact that the twisted vane elements are connected together in an articulable manner and are contained within a length of flexible pipe there is no limitation on the overall length of the mixer since the length of pipe can be a coiled length. In addition, there are certain applications in which the fact that the mixer is flexible is a great advantage, for example in the coating of underground pipes with a cold setting together of a liquid or plastics coating medium and a liquid curing agent or initiator.It will also be understood that by virtue of the fact that the twisted vane elements are connected together loosely within the bore of the pipe, the effective length of the mixer can be varied by adding or substracting a number of the vane elements. In this way, a mixer which has initially been designed for one particular application can readily be adapted to suit another application.

The invention is applicable to mixers having a wide range of bore diameters and it will be understood that if the flexible pipe is capable of withstanding high internal pressure the liquids which are to be mixed can be forced through the mixer at high pressure. Such a flexible pipe may be provided with braided wire reinforcement, the synthetic plastics walls of the pipe being such as to withstand chemical attack from whatever substance will be passed through the mixer.

Various modifications may be made. For example, it will be observed in Figure 2 that the opposite ends of each twisted vane element are turned through substantially a right angle relative to each other; however, the vane elements could have a lesser or greater amount of twist. It will also be understood that the optimum length of each vane element may be determined by trial and experiment and that the length of each vane element will depend to some extent on the bore diameter which the element has to fit. It is not essential for both ends of each vane element to be notched; it would be quite possible for adjacent vane elements to be engaged together end to end in articulable but non-rotatable relation if only one end of each vane element was suitably notched.

It may be found that to enable the plurality of vane elements to be entered into the bore of the pipe one by one, for an already assembled length of elements to be urged further along the pipe by a further vane element, at least the leading end of each vane requires to be very slightly tapered or rounded at its outer corners so that it does not "snag" or "pick up" the walls of the pipe.

Claims (10)

1. A static mixer including a length of flexible pipe and a plurality of twisted vane elements located within the bore of the pipe, the direction of twist of successive vane elements being of opposite hand, the successive twisted vane elements being connected together loosely within the bore of the pipe by means which permit their articulation and allow the pipe to flex.

2. A static mixer according to claim 1, in which the means which connect the successive twisted vane elements together within the bore of the pipe are constituted by a central notch in at least one end of each element, the notch having a width equal to the thickness of the material of which the vane elements are made, the arrangement being such that the end portion of the immediately adjacent vane element can be engaged with said notch.

3. A static mixer according to claim 2, in which both ends of each twisted vane element are notched for the connection together of successive elements in an articulable manner.

4. A static mixer according to any one of the preceding claims, in which the twisted vane elements are an interference fit in the bore of the pipe.

5. A static mixer according to any one of the preceding claims, in which the plurality of vane elements are located within the bore of the pipe by means of an abutment member at what, in use of the mixer, will be the downstream end of the pipe.

6. A static mixer according to any one of the preceding claims, in which the flexible pipe is made of a synthetic plastics material and has braided wire reinforcement to enable the mixer to operate under relatively high internal pressure.

7. A method of making a static mixer, including the step of entering a plurality of separate twisted vane elements in turn into a length of flexible pipe.

8. A method according to claim 7, in which the twisted vane elements are made by suitably twisting a relatively long length of strip material and cropping the vane elements from the pre-twisted strip, a subsequent step in the forming of the vanes being the forming of a notch in at least one end of each vane, the notch having a width equal to the thickness of the strip material of which the vane elements are made, the arrangement being such that adjacent vane elements can be engaged together end to end in articulable but non-rotatable relation.

9. A static mixer constructed, arranged and adapted to be used substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.

10. A method of making a static mixer, substantially as hereinbefore described.