GB1601403A

GB1601403A - In-line mixers

Info

Publication number: GB1601403A
Application number: GB9035/78A
Authority: GB
Original assignee: General Signal Corp
Current assignee: SPX Corp
Priority date: 1977-03-21
Filing date: 1978-03-07
Publication date: 1981-10-28
Also published as: MX4423E; SE439735B; DE2811489C2; FR2384536A1; IT1093884B; AU3426278A; DE2811489A1; JPS53116563A; AU515460B2; IT7821426A0; SE7803226L; FR2384536B1

Description

(54) IMPROVEMENTS IN OR RELATING TO IN-LINE MIXERS (71) We, GENERAL SIGNAL CORPORATION, a corporation organized and existing under the laws of the State of New York, United States of America, of High Ridge Park, Stamford, Connecticut 06904, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates generally to improvements in mixing.

In many areas of technology it is frequently desirable to mix a fluid with one or more other substances while the substances are passing through a conduit en route to a delivery point. It has been necessary to mix gasses, liquids, and even some solids of a powdered or particulate nature. In the past, numerous devices have been employed to solve this problem and these devices have been generally classified as "in-line" blenders and mixers. One type of "in-line" device known as a static or motionless blender and mixer comprises a conduit having therewithin a plurality of stationary elements defining within the conduit a plurality of flow chanels intersecting with one another so as to cause substances flowing in said flow channels to mix.Although such devices have taken on numerous forms, it is known in the art that a particularly effective means of mixing substances is to flow the substances through a plurality of spiral flow paths which are periodically subdivided and reversed in direction of twist. For example U.S. Patent No. 3,286,992 to Armeniades et al discloses a mixing device having a hollow cylindrical tube and a plurality of curved sheet-like elements extending in series longitudinally within the tube throughout the length thereof. The sheet-like elements have periodic reversals of curvature and are affixed to the walls of the tube. U.S. Patent No. 3,794,300 to Harder discloses an in-line blender having a shaft extending longitudinally through a conduit and having a plurality of sheet-like mixer elements spirally twisted about the shaft and affixed to it.

Although such prior art devices have generally performed in an acceptable manner, they have exhibited certain shortcomings. Since each mixing stage in these devices has been made of continuous sheet material. the amount of rotation imparted to the fluid per mixing stage has been fixed for each stage. Furthermore, the mixing stages in the prior devices have not been easily adjusted to change flow patterns and accommodate different flow conditions. Thus. different mixing devices have been required to satisfy different flow conditions. Additionally, although these devices have generally been effective for mixing under laminar flow conditions, they have not been as effective under turbulent flow conditions. Finally, such devices have usually been of a rather permanent nature and have not been easily disassembled for cleaning.It is also frequently desirable to inject fluids into a fluid line, or sample fluids flowing in the line. Thus, a need has developed for a fluid injection and sampling device which may be easily combined with an in-line blender to co-operate with the blending process.

The present invention provides an in-line mixer comprising a conduit having defined therewithin a plurality of stationary mixing stages, each mixing stage comprising a series of individual channel defining elements juxtaposed with one another longitudinally of said conduit and angularly orientated with respect to each other to define generally spiral flow channels which spiral in opposite directions in adjacent mixing stages, the pitch of the spiral flow channels being determined by the relative angular orientation of adjacent channel defining elements within a respective mixing stage, each said element having a predetermined extent longitudinally of the conduit and being so formed transversely to the conduit as, within its own longitudinal extent, to divide the flow cross-section of the conduit into a plurality of separate flow channel sections, the serial juxtaposition of said elements serving to combine said channel sections serially with one another so as to constitute said generally spiral flow channels, flow channels of one stage intersecting the flow channels of the or each adjacent stage.

As will be explained in the following, the in-line mixer according to the present invention may be easily adapted for use in both laminar and turbulent flow conditions, and may be easily assembled and disassembled for cleaning and repositioning. Furthermore, the design of the in-line mixer of the invention is such that the number of flow channels may be varied.

The device is both simple in construction and inexpensive to manufacture, and can readily be combined with a fluid injecting and sampling device.

The advantages and novel features of the present invention will become apparent from the following detailed description of exemplary embodiments of the invention which are shown in the accompanying drawings wherein: Figure 1 is a side view, partly in cross-section, of an in-line mixer or blender of the present invention; Figure 2 is an end view of a portion of the in-line blender shown in Figure 1; Figure 3 shows an end view of a mixing element; Figure 4 shows the mixing element shown in Figure 3 as viewed from the opposite end; Figure 5 shows a partial enlarged side view of the mixing element shown in Figure 3; Figure 6 shows a side view of a spacer element; Figure 7 shows a side view in partial cross-section of a second embodiment of the present invention; Figure 7A shows a schematic end view taken along section A - A of Figure 7;; Figure 7B shows a schematic end view taken along lines B - B of Figure 7; Figure 8 shows an end view of a device for injecting and sampling fluids in the line; Figure 8A shows in partial cross-section taken along lines 8A-8A of Figure 8; Figure 9 shows an end view in partial cross-section of a second form of a device for injecting and sampling fluids in the line; Figure 9A shows a cross-section of the device shown in Figure 9 taken along lines 9A 9A; Figure 10 shows a third form of a device for injecting and sampling fluids in the line; and Figure lOA shows a cross-section of the device shown in Figure 10 taken along lines 10A 10A.

Referring to Figures 1 through 5 of the drawings, a preferred embodiment of the in-line mixer or blender of the present invention will be described in detail. Figure 1 shows an in-line blender 20 including a conduit 22 having a hollow interior disposed about a central axis 24. The substances to be mixed are introduced into a section of conduit upstream of the conduit 22, in a known manner. A shaft 26 extends longitudinally through the conduit 22 along the central axis 24. Mounted on the shaft 26 are a plurality of mixing stages 28, 30, 32, etc., extending in series along the shaft within the conduit 22. In a preferred embodiment there are six such mixing stages.However, it should be understood that in any particular case the number of mixing stages may be determined by the properties of the substances being mixed, the desired flow, the desired pressure drop through the mixer, and the cost of manufacture. Each of the mixing stages defines a plurality of spiral channels within the hollow interior of the conduit 22. These spiral channels extend the entire length of each of the mixing stages. One of the particularly unique features of the present invention is that each of the mixing stages includes of plurality of distinct segments or mixing elements 34.

Each of the segments or mixing elements 34 is formed in the shape of a propeller and, as is best seen in Figures 3 and 4, includes a hub 36 and a plurality of blades 38 extending radially outwardly from the hub 36. Each of the blades includes a spiral twist. The angle of each blade 38 at the base thereof with respect to the central axis 24 is designated in Figure 5 as angle b. The angle that the radially outward tip of the blade 38 forms with the central axis 24 is designated in Figure 5 as angle c. The difference between these two angles (angle b-c) is the angle of twist of each blade. In Figure 5, angle b is illustrated as being 15 degrees and angle c as 45 degrees so that the angle of twist b-c is equal to 30 degrees. The tip angle c determines the pitch of each mixing stage (i.e., the axial length required to rotate a channel through 360 degrees) and in cooperation with the hub diameter determines the hub angle b.

Depending on the substances being mixed and the desired pressure drop over the entire length of the blender 20, the tip angle c will generally vary from 30 degrees to 60 degrees.

For a given tip angle c and a given axial length per segment, the number of segments 34 within each mixing stage will determine the amount of rotation imparted to the fluid passing through that mixing stage. Thus in the embodiment illustrated in Figure 1, there are seven segments creating 180 degrees of rotation for each spiral channel within each mixing stage.

The axial length of the segments 34 determines the degree of flexibility one would have in altering the flow patterns within the blender 20 and thus the axial length of the segments 34 may be chosen accordingly. Although for economy of design, the axial length of each segment 34 has been illustrated as being equal, it is to be understood that it is within the scope of the present invention to include segments having different axial lengths within the same blender. In the embodiment shown in Figure 1, the axial distance between blades of adjacent segments is preferably minimized to eliminate crossover flow between channels. In this embodiment the axial distance between blades will preferably be significantly less than the thickness of a blade. The radial dimension of the blades 38 is such that each blade 38 will touch or nearly touch the inner walls of the conduit 22.A slight amount of clearance is desired between the outer tips of the blades 38 and the walls of the conduit 22 to permit the entire mixing structure to be withdrawn from the conduit 22, as will be discussed in more detail later.

Another particularly unique feature of the present mixer is that each of the segments 34 further includes means for adjusting both the angular and the axial position of each of the segments with respect to adjacent segments along the shaft 26. The adjusting means includes the hub 36 and indexing means on the axial ends of the hubs for maintaining a predetermined fixed angular relationship between adjacent hubs. As can be seen most clearly in Figures 3, 4, and 5, this indexing means comprises a plurality of linear projections 40, projecting axially from the ends of the hub 36, extending radially outwardly from the hole in the hub surrounding shaft 26, and spaced an equal angular distance from one another about one end of the hub 36.These projections are preferably thirty in number and are spaced 12 degrees apart, although a greater or lesser number of projections could be provided depending on the accuracy of indexing required. Correspondingly, a plurality of linear depressions or grooves 42 are formed in the opposite axial end of hub 36, extend radially outwardly from the hole in the hub surrounding shaft 26, and are spaced equally about the end of the hub 36. These depressions 42 are spaced in a like manner to the projections 40, and thus would be spaced 12 degrees apart. Since in assembling the blender 20 the hubs 36 are in sliding engagement with the shaft 26, it is apparent that when adjacent hubs are placed in an abutting relationship, the projections 40 will engage the depressions 42 to thereby prevent relative rotation between adjacent segments.It will be understood by those skilled in the art that other means of preventing rotation between adjacent segments could be provided. For example, each of the hubs 36 could include a set screw extending radially therein to engage the shaft 26 and prevent axial or angular movement between the hub 35 and the shaft 26.

Thus, a plurality of segments may be axially and angularly positioned on the shaft 26 to define a plurality of spiral channels which rotate in a first direction, for example, as shown in mixing stage 28. Likewise, a second stationary mixing stage 30 may be placed axially adjacent the first mixing stage 28 to define a plurality of spiral channels which rotate in a second angular direction opposite to the first angular direction. Preferably, the leading edges of the blades of the first segment of mixing stage 30 are positioned so as to bisect the spiral channels defined by mixing stage 28. This generally results in optimal division of flow and therefor optimal mixing of the substances passing through conduit 22. Likewise, subsequent mixing stages will result in a reversal of twist of the channels and also will bisect the spiral channels of the previous mixing stage.However, it should be understood that it is within the scope of this invention to position the various mixing stages and segments in any manner that proves desirable. Thus, the angle of intersection between axially adjacent mixing stages may be varied. As was mentioned above, the number of mixing stages within the blender 20 may also vary in accordance with various desired flow and mixing characteristics.

Although the mixing segments 34 are illustrated as having three blades and thus creating three spiral channels within the conduit 22, it is within the scope of the present invention to vary the number of blades 38 in accordance with the mixing characteristics one wishes to design into the blender 20. For most mixing applications, from two to four blades should prove sufficient to provide the desired flow and mixing through conduit 22. In the embodiment shown in Figure 1, three blades are preferred.

The blender 20 further includes a retaining means 44 shown in cross-section in Figure 1 and in an end view in Figure 2. The retaining means includes a retaining member 46 having an outer ring 48, an inner hub 50, and plurality of vanes 52 extending radially outwardly from the hub 50 to the ring 48. The vanes 52 are preferably identical in number to the number of blades on the first mixing segment and are preferably aligned with the leading edges of these blades. Although the in-line blender of the present invention is suitable for mixing fluids flowing therethrough in either direction, the retaining means 44 is preferably located on the inlet end of the blender so that flow in Figure 1 would be from right to left.

The conduit 22 includes flanges 54 mounted on both ends thereof to enable the in-line blender 20 to be bolted to adjacent sections of conduit. The ring 48 is adapted to be clamped between the flange 54 and the flange of an adjacent section of conduit. The inner surface of the hub 50 is threaded as is an end portion 56 of shaft 26. A threaded adapter 58 threadingly engages end portion 56 of shaft 26 and hub 50 of retaining member 46 to prevent axial movement therebetween. The opposite end of shaft 26 is externally threaded and adapted to receive a holding means 60 for holding the mixing stages in compression against the retaining means 44 and thereby prevent axial movement of the mixing stages within the conduit 22.The holding means preferably includes a pair of nuts 62 and 64 and a lock washer 66 which threadingly engage the threaded end portion 68 of shaft 26 to hold the mixing stages in compression against retaining means 44.

In a typical in-line blender of the type shown in Figure 1, the blender components may be formed from a variety of materials, the most important selection criteria being that of sufficient strength and rigidity and that the particular material selected does not react with the substances being mixed. One preferred such material is stainless steel. Additionally, the mixing segments 34 are preferably formed by casting to further the economy of manufacture. The diameter of the conduit 22 will generally vary from approximately two inches to approximately twelve inches. The length of the conduit 22 will generally be approximately equal to ten times the diameter of the conduit.

The in-line blender 20 is designed to be used for all types of flow conditions i.e., laminar or turbulent. In laminar flow, the fluid particles move along straight, parallel paths in layers. The magnitudes of the velocity of adjacent layers are not the same. The viscosity of the fluid is dominant and thus suppresses any tendency of the flow to achieve turbulent conditions. In turbulent flow, the particles of fluid move in a haphazard fashion in all directions, making it impossible to trace the motion of an individual particle.

The Reynolds number for an in-line blender and a specific fluid can be calculated to determine whether the flow is in the laminar or turbulent range. The Reynolds number is defined as: RE = Vc.p E where: RE = Reynolds number V = mean veolicty of feet/second d = diameter of conduit in feet p = mass density of fluid in slugs/foot3 I1 = absolute viscosity in pounds seconds/foot2 When the Reynolds number is less than 2,000, the flow is generally classified as laminar.

When the Reynolds number of in-line blender 20 is greater than 2,000, the flow is generally classified as turbulent.

The embodiment of the in-line blender shown in Figure 1 is generally preferred for laminar flow conditions. In the embodiment shown in Figure 1, the angular and axial position of adjacent hubs is adjusted so as to minimize the space between the blades of adjacent segments to correspondingly optimize blending for laminar flow of fluid through the conduit 22. Thus distinct spiral channels are set up by each mixing stage, and no crossover flow is permitted between these channels. Accordingly, mixing is accomplished by rotation of the fluid within the channel and by periodically dividing flow at each new mixing stage.

On the other hand, the angular and axial position of the hubs with respect to adjacent hubs may be adjusted to define significant gaps between the blades of adjacent segments and thereby optimize blending for turbulent flow of fluid through the conduit 22. Both angular and axial displacement may be accomplished, for example, by utilizing set screws on each of the hubs and changing their relative positions on the shaft, as was discussed above. However, a preferred form of axial displacement is illustrated in Figure 6 and includes the use of a plurality of spacer elements 70. These spacer elements may be of any desired axial length and may be interspersed as desired between adjacent hubs within a mixing stage to create gaps between adjacent segment blades. Each of the spacer elements 70 is placed in sliding engagement with the shaft 26 and includes indexing means on the axial ends thereof for maintaining a fixed angular relationship between adjacent hubs. The indexing means consists of projections 72 and 74 which are identical to the projections 40 and grooves 42 found on the hubs 36.

A preferred embodiment designed to mix under turbulent flow conditions is illustrated in Figures 7, 7A, and 7B. Figure 7 shows a first mixing stage 80 and a second mixing stage 82.

The mixing stages 80 and 82 separate mixing stages such as those illustrated in Figure 1. The first mixing stage 80 includes two segments 34c and 34d, similar to the segment 34 illustrated in Figure 1, each of which includes blades twisted in a first direction. However, the segments 34c and 34d are angularly spaced so as to create significant gaps 84 between adjacent blades. The gaps 84 are particularly evident in Figure 7B, which schematically illustrates the relative angular positions of segments 34c and 34d. The angular position of the segments 34c and 34d in mixing stage 80 may be contrasted with the angular position of the segments 34a and 34b in the mixing stage immediately upstream of mixing stage 80 by examining Figure 7A. In Figure 7A it is apparent that there is no angular gap between adjacent segments 34a and 34b.The size of the gaps 84 may be adjusted to achieve optimal mixing. However, the degree of adjustability of the gaps 84 is limited by the fineness of the indexing means 40 and 42. Utilizing the 12 degree indexing illustrated in Figures 3 and 4, the gaps 84 could be adjusted in 12 degree increments. The second mixing stage 82 includes segments 34 having blades twisted in the opposite direction to those of mixing stage 80. The segments 34 of mixing stage 82 are likewise angularly displaced relative to one another so as to create gaps 84 between the blades thereof. Thus, the rather short spiral channels defined by mixing stages 80 and 82 permit a significant amount of crossover flow between the channels such that the stages 80 and 82 impart a chopping action to the flow. This chopping action is highly desirable under turbulent flow conditions to achieve satisfactory mixing.It is within the scope of the present invention to either increase or decrease the number of segments in stages 80 and 82 depending on the substances being mixed. Additionally, of course, the number of turbulent or chopper stages 80 or 82 utilized within a given blender will also depend on the substances being mixed. Thus, it becomes apparent that because of the flexibility of the possible segment combinations that may be utilized within the conduit 22, the in-line blender 20 may be constructed to achieve optimal flow condition for any substances being mixed.

Another particular feature of the present mixer relates to the ease with which the in-line blender may be assembled and disassembled. To assemble the in-line blender, the retaining device 44 is secured to the end 56 of the shaft 26. This is accomplished by threadingly engaging the member 58 with the inner portion of the hub 50 and with the end 56 of shaft 26. A plurality of the mixing elements or segments 34 are then placed on the shaft 26 in sliding engagement therewith. Should one wish to axially space any segments from adjacent segments, spacer element 70 may also be placed in sliding engagement with the shaft 26 as desired. Each of the segments 34 is then positioned at a desired angular and axial position on the shaft 26.After the desired number of elements have been added to the shaft, the holding device 60 is placed on the end 68 of shaft 26 so as to hold the various elements in compression between the holding device 60 and the retaining device 44. This is accomplished by sliding the lock washer 66 in place against the last element on the shaft and by threadingly engaging nuts 62 and 64 on the end 68 of shaft 26. It should be understood, of course, that to a certain extent the sequence of the steps thus far described may be altered. For example, the mixing elements may be added to the shaft first and the retaining device 44 and holding device 60 subsequently added. Or the holding device may be engaged with the end 68 of shaft 26 before the retaining device 44 is engaged.

The shaft 26 with the mixing elements mounted thereon is then placed into conduit 22. As was mentioned before, there is sufficient clearance between the tips of the blades 38 and the inner surface of conduit 22 to permit the entire assembly to slide in and out of conduit 22.

The shaft 26 with the mixing elements mounted thereon is then secured within conduit 22 so as to prevent relative axial movement between the mixing assembly and the conduit 22.

This is preferably accomplished by placing the retaining device 44 in to a bearing relationship with one end of the conduit and securing it thereto. This is accomplished by clamping the retaining device 44 between flange 54 of conduit 22 and the flange of an adjacent section of conduit.

The in-line blender may further be coupled with a device for injecting fluids into the fluid line and for sampling fluids flowing in the line. A first such device is shown in Figures 8 and 8A. A fluid sampling and injecting device 100 is similar in construction to the retaining member 46 shown in Figure 1 and is adapted to be utilized as a retaining member as shown in Figure 1. The device 100 includes a frame shown as an outer ring 102. The ring 102 has an outer cylindrical surface 104 and a hollow interior which defines an inner cylindrical surface 106, which is adapted to be disposed about the central axis 24. A hub 108 is also disposed about the central axis and is affixed to one end of the shaft 26. A plurality of vanes 110 are connected to the hub 108 and the inner surface 106 of frame 102.The vanes 110 extend radially outwardly from the hub 108 and divide the hollow interior of the frame 102 into a plurality of flow channels. As was discussed in connection with the retaining ring 46 shown in Figure 1, these flow channels are aligned with the spiral channels of the first mixing stage 28 such that they form a continuation of the spiral channels. Means are provided in the frame 102 for placing each of the flow channels in fluid communication with a point external the outer surface 104 of frame 102. As shown in Figures 8 and 8A, this fluid communication means comprises a plurality of openings 112 in the frame 102 which extend radially outwardly from the inner surface 106 to the outer suface 104.The portion of the opening 112 nearest the surface 104 preferably includes a threaded portion 114 for securing a conduit to the opening 112, to deliver fluid to, or remove fluid from, the flow channels.

Preferably, there is one opening 112 for each flow channel, however, a greater or lesser number may be utilized as desired.

Figures 9 and 9A show a second embodiment of the fluid injection and sampling device.

The Figure 9 and 9A embodiment is identical in every respect to that shown in Figures 8 and 8A with the exception that the flow injection and sampling device 120 shown in Figures 9 and 9A further includes a plurality of tubular members 122 extending through each of the openings 112 into the flow channels. Each tubular member 122 is preferably releasably affixed to the frame 102 by means of a standard compression fitting 124, so that the radial position of each tubular member 122 is adjustable. The end of each tubular member which extends into the flow channel is closed, preferably by means of a plug 126. However, each tubular member 122 contains an opening 128 in the side of the member to permit fluid to be injected and sampled in a direction parallel to the flow within the channel.For injection of fluid into the flow channel, the opening 128 will generally be positioned on the downstream side of the tubular member 122. For sampling fluid in the flow channel, the member 122 may be rotated through 180 degrees so that the opening 128 will be positioned on the upstream side of the member 122. The member 122 may also be utilized as a pressure sensing tap.

In Figures 10 and 10A a third embodiment of the fluid injection and sampling device is illustrated. Here a fluid injection and sampling device 130 is identical to the devices shown in Figures 8 and 9 with the exception that a tubular member 132 extends through each of the openings 112 into each of the flow channels. As was the case in the Figure 9 embodiment, the tubular members 132 are releasably affixed to the ring 102 by a compression fitting 124 so that the radial position of each of the tubular members 132 is adjustable. However, the tubular members 132 differ from the tubular members 122 in that the end of each tubular member 132, which extends into the flow passage, is open to permit fluid to be injected and sampled in a direction perpendicular to the flow within the channel. The tubular member 132 is also useful as a pressure sensing tap.It should be understood that although each of the fluid injection and sampling devices shown in Figures 8, 9, and 10 are illustrated as including only identical fluid communication means, it is within the scope of the present invention to utilize any combination of the three different fluid communication means on a single frame 102.

Thus, it is apparent that the in-line blender of the present invention may be easily adapted for use in either laminar or turbulent flow conditions. This is so since the individual mixing elements of the in-line blender may be assembled and arranged to form numerous different mixing paths. Furthermore, simply by using elements which have a greater or lesser number of blades, the number of flow channels may also be varied within the in-line blender. The blender is relatively simple in construction and inexpensive to manufacture.

The components of the blender may be easily assembled and disassembled for cleaning and repositioning, adding further to the economy of operation. Finally, a fluid injection and sampling device has been provided which may easily be combined with an in-line blender to cooperate with the blending process.

WHAT WE CLAIM IS: 1. An in-line mixer comprising a conduit having defined therewithin a plurality of stationary mixing stages, each mixing stage comprising a series of individual channel defining elements juxtaposed with one another longitudinally of said conduit and angularly orientated with respect to each other to define generally spiral flow channels which spiral in opposite directions in adjacent mixing stages, the pitch of the spiral flow channels being determined by the relative angular orientation of adjacent channel defining elements within a respective mixing stage, each said element having a predetermined extent longitudinally of the conduit and being so formed transversely to the conduit as, within its own longitudinal extent, to divide the flow cross-section of the conduit into a plurality of separate flow channel sections, the serial juxtaposition of said elements serving to combine said channel sections serially with one another so as to constitute said generally spiral flow channels, flow channels of one stage intersecting the flow channels of the or each adjacent stage.

2. An in-line mixer as claimed in claim 1, wherein there is an angular offset at the junction of adjacent stages so that the output of any one spiral flow channel which spirals in one direction feeds into the inputs of a plurality of spiral flow channels which spiral in the opposite direction.

3. An in-line mixer as claimed in claim 1 or 2. wherein the angular extent of any spiral

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the outer surface 104 of frame 102. As shown in Figures 8 and 8A, this fluid communication means comprises a plurality of openings 112 in the frame 102 which extend radially outwardly from the inner surface 106 to the outer suface 104. The portion of the opening 112 nearest the surface 104 preferably includes a threaded portion 114 for securing a conduit to the opening 112, to deliver fluid to, or remove fluid from, the flow channels. Preferably, there is one opening 112 for each flow channel, however, a greater or lesser number may be utilized as desired. Figures 9 and 9A show a second embodiment of the fluid injection and sampling device. The Figure 9 and 9A embodiment is identical in every respect to that shown in Figures 8 and 8A with the exception that the flow injection and sampling device 120 shown in Figures 9 and 9A further includes a plurality of tubular members 122 extending through each of the openings 112 into the flow channels. Each tubular member 122 is preferably releasably affixed to the frame 102 by means of a standard compression fitting 124, so that the radial position of each tubular member 122 is adjustable. The end of each tubular member which extends into the flow channel is closed, preferably by means of a plug 126. However, each tubular member 122 contains an opening 128 in the side of the member to permit fluid to be injected and sampled in a direction parallel to the flow within the channel.For injection of fluid into the flow channel, the opening 128 will generally be positioned on the downstream side of the tubular member 122. For sampling fluid in the flow channel, the member 122 may be rotated through 180 degrees so that the opening 128 will be positioned on the upstream side of the member 122. The member 122 may also be utilized as a pressure sensing tap. In Figures 10 and 10A a third embodiment of the fluid injection and sampling device is illustrated. Here a fluid injection and sampling device 130 is identical to the devices shown in Figures 8 and 9 with the exception that a tubular member 132 extends through each of the openings 112 into each of the flow channels. As was the case in the Figure 9 embodiment, the tubular members 132 are releasably affixed to the ring 102 by a compression fitting 124 so that the radial position of each of the tubular members 132 is adjustable. However, the tubular members 132 differ from the tubular members 122 in that the end of each tubular member 132, which extends into the flow passage, is open to permit fluid to be injected and sampled in a direction perpendicular to the flow within the channel. The tubular member 132 is also useful as a pressure sensing tap.It should be understood that although each of the fluid injection and sampling devices shown in Figures 8, 9, and 10 are illustrated as including only identical fluid communication means, it is within the scope of the present invention to utilize any combination of the three different fluid communication means on a single frame 102. Thus, it is apparent that the in-line blender of the present invention may be easily adapted for use in either laminar or turbulent flow conditions. This is so since the individual mixing elements of the in-line blender may be assembled and arranged to form numerous different mixing paths. Furthermore, simply by using elements which have a greater or lesser number of blades, the number of flow channels may also be varied within the in-line blender. The blender is relatively simple in construction and inexpensive to manufacture. The components of the blender may be easily assembled and disassembled for cleaning and repositioning, adding further to the economy of operation. Finally, a fluid injection and sampling device has been provided which may easily be combined with an in-line blender to cooperate with the blending process. WHAT WE CLAIM IS:

1. An in-line mixer comprising a conduit having defined therewithin a plurality of stationary mixing stages, each mixing stage comprising a series of individual channel defining elements juxtaposed with one another longitudinally of said conduit and angularly orientated with respect to each other to define generally spiral flow channels which spiral in opposite directions in adjacent mixing stages, the pitch of the spiral flow channels being determined by the relative angular orientation of adjacent channel defining elements within a respective mixing stage, each said element having a predetermined extent longitudinally of the conduit and being so formed transversely to the conduit as, within its own longitudinal extent, to divide the flow cross-section of the conduit into a plurality of separate flow channel sections, the serial juxtaposition of said elements serving to combine said channel sections serially with one another so as to constitute said generally spiral flow channels, flow channels of one stage intersecting the flow channels of the or each adjacent stage.

flow channel is between 90 degrees and 360 degrees.

4. An in-line mixer as claimed in any one of the preceding claims, wherein the angular orientations of the individual channel defining elements are adjustable.

5. An in-line mixer as claimed in any one of the preceding claims, wherein the positions of the individual channel defining elements longitudinally of said conduit are adjustable.

6. An in-line mixer as claimed in any one of the preceding claims, wherein the individual channel defining elements are mounted on a shaft whereupon they are capable of both axial and angular movement, means being provided for holding the elements in set positions on the shaft.

7. An in-line mixer as claimed in claim 6, including spacers mounted on said shaft between some of the channel defining elements for determining the axial setting of the elements on the shaft.

8. An in-line mixer as claimed in claim 6 or 7, wherein the shaft is mounted at one end thereof to one end of the conduit and holding means is associated with the other end of the shaft and serves to clamp the elements between itself and the mounting of the said one end of the shaft to the conduit.

9. An in-line mixer as claimed in claim 8, wherein the shaft is releasable at said one end from the conduit, the said holding means is releasable, and the shaft, the holding means and the channel defining elements are all removable from the conduit.

10. An in-line mixer as claimed in any one of the preceding claims, wherein interlocking indexing means are provided on abutting sufaces of the elements in said serial juxtaposition of elements for maintaining adjacent said elements in set angular relationship with one another.

11. An in-line mixer as claimed in any one of the preceding claims, wherein each of said channel defining elements has a plurality of generally outwardly extending blades for defining said flow channel sections.

12. An in-line mixer as claimed in claim 11, and wherein the said elements are mounted on a shaft, wherein the elements comprise a hub portion mounted on the shaft and said blades extend outwardly therefrom.

13. An in-line mixer as claimed in claim 11 or 12, wherein each of said blades is formed with a spiral twist from its root towards its tip.

14. An in-line mixer as claimed in claim 13, wherein different ones of said channel defining elements have blades with differently directed spiral twists.

15. An in-line mixer as claimed in claim 14, with at least one pair of channel defining elements which have differently twisted blades juxtaposed next adjacent each one to the other.

16. An in-line mixer as claimed in any one of claims 11 to 15, wherein the angular orientation of at least some of said channel defining elements with respect to the next adjacent element is such as to minimise the spacing between the blades of the adjacent elements for use during laminar flow of substances through said conduit.

17. An in-line mixer as claimed in any one of claims 11 to 15, wherein the angular orientation of at least some of said channel defining elements with respect to the next adjacent element is such as to define significant gaps between the blades of the adjacent elements for use during turbulent flow of substances through said conduit.

18. An in-line mixer as claimed in any one of claims 11 to 17, wherein each of said channel defining elements has two or three or four blades for defining two or three or four fluid flow channels respectively in said conduit.

19. An in-line mixer as claimed in any one of the preceding claims, including means placing one or more of the flow channels defined in said conduit in fluid communication with the exterior of said conduit for enabling sampling of fluid flowing in the -respective channel(s) and enabling injection of fluid into fluid flowing in the respective channel(s).

20. An in-line mixer as claimed in claim 19, wherein said fluid flow communication means comprises an annular member affixed to one end of the conduit and having internally thereof members defining flow channels within the annular member which are in continuity with the flow channels defined in the conduit, at least one opening being provided through the annular member from the interior to the exterior thereof for enabling fluid flow communication with a respective one or more of the channels defined wihin the annular member.

21. An in-line mixer as claimed in claim 20, and wherein said channel defining members within the conduit are mounted on a shaft, said channel defining members within the annular member comprising vanes extending between the interior surface of the annular member and a central hub, the vanes serving to support the hub, and the hub serving to support one end of said shaft.

22. An in-line mixer as claimed in claim 20 or 21, including a tubular probe extending through the said opening into the respective channel defined within the annular member to enable fluid to be transferred to or from said channel.

23. An in-line mixer as claimed in claim 22, wherein the extent of projection of the tubular probe into the respective channel is adjustable.

24. An in-line mixer as claimed in claim 22 or 23, wherein the orifice of the tubular probe within the respective channel is directed to permit fluid to be taken from or introduced into fluid flowing in the respective channel in a direction parallel to the direction of fluid flow in the channel.

25. An in-line mixer substantially as herein described with reference to Figures 1 to 5 of the accompanying drawings.

26. An in-line mixer substantially as herein described with reference to Figures 7, 7A and 7B of the accompanying drawings.

27. An in-line mixer as claimed in claim 25 or 26 provided with a fluid sampling or injection device substantially as herein described with reference to Figures 8 and 8A, Figures 9 and 9A, or Figures 10 and 10A of the accompanying drawings.