A Mixing Apparatus and Mixing Method

Abstract

Lightweight construction panels, such as plasterboard, (e.g. gypsum plasterboard) are commonly used to provide internal partitions in buildings. Sheets of plasterboard are typically carried and positioned by hand. Accordingly, it is desirable to reduce the weight of plasterboard. It is known to include an aqueous foam in the stucco slurry used to produce plasterboards. However, prior known mixers have been found to destroy foam bubbles. The present invention provides a stucco slurry mixing apparatus (100) including an inlet (130) for the introduction of foam into a mixing chamber (110), wherein the inlet (130) includes an inlet aperture (132) in a wall of the mixing chamber (110) and an inlet conduit (134) extending therefrom such that a relative angle between a longitudinal axis (136) of the inlet conduit (134) and a tangent (140) to a mixing path (124) defined by a mixing member (120) is less than 90 degrees.

Claims

1. A stucco slurry mixing apparatus comprising: a vessel for receiving and mixing ingredients therein; a mixing member configured to move within the vessel and mix ingredients contained therein, wherein the movement of the mixing member defines a non-rectilinear mixing path; wherein the vessel comprises: a first inlet for the introduction of ingredients comprising at least aqueous foam into the vessel, wherein the first inlet comprises an inlet aperture in a wall of the vessel and an inlet conduit extending therefrom such that a relative angle between a longitudinal axis of the inlet conduit and a tangent to the mixing path is less than 90 degrees; a second inlet comprising a second inlet aperture in a wall of the vessel for the introduction of further ingredients into the vessel; and an outlet for mixed slurry, wherein the first inlet and outlet are positioned such that, in use, the average residence time of the aqueous foam within the vessel is similar to the average residence time of the other components of the stucco slurry within the vessel.

2. The stucco slurry mixing apparatus of claim 1, wherein the inlet conduit extends from the inlet aperture in a direction away from a direction of rotation of the mixing member.

3. The stucco slurry mixing apparatus of claim 1, wherein the mixing path lies entirely within a single plane and the longitudinal axis of the inlet conduit lies parallel to and spaced from the plane in which the mixing path lies.

4. The stucco slurry mixing apparatus of claim 1, wherein the mixing member is positioned between the first inlet and the outlet.

5. The stucco slurry mixing apparatus of claim 1, wherein the mixing member is positioned between the second inlet and the outlet.

6. The stucco slurry mixing apparatus of claim 1, wherein the inlet aperture is in a side wall of the vessel.

7. The stucco slurry mixing apparatus of claim 1, wherein the second inlet aperture is in a top wall of the vessel.

8. The stucco slurry mixing apparatus of claim 1, wherein the second inlet is spaced from the first inlet.

9. The stucco slurry mixing apparatus of claim 1, wherein the inlet aperture is elliptical or oval in shape.

10. The stucco slurry mixing apparatus of claim 1, wherein the inlet conduit extends from the inlet aperture such that a relative angle between the longitudinal axis of the inlet conduit and the tangent to the mixing path is less than 45 degrees.

11. The stucco slurry mixing apparatus of claim 1, wherein the inlet conduit extends from the inlet aperture such that a relative angle between the longitudinal axis of the inlet conduit and the tangent to the mixing path is less than 20 degrees.

12. The stucco slurry mixing apparatus of claim 1, wherein the inlet conduit extends from the inlet aperture such that the longitudinal axis of the inlet conduit is parallel to the tangent to the mixing path.

13. The stucco slurry mixing apparatus of claim 1, wherein the vessel further comprises a third inlet.

14. The stucco slurry mixing apparatus of claim 1, wherein the outlet comprises an outlet aperture and an outlet conduit extending therefrom, wherein the outlet conduit diverges from a direction of rotation of the mixing member as it extends away from the outlet aperture.

15. The stucco slurry mixing apparatus of claim 14, wherein a relative angle between a longitudinal axis of the outlet conduit and a further tangent to the mixing path is less than 90 degrees.

16. The stucco slurry mixing apparatus of claim 1, wherein the mixing path is circular.

17. The stucco slurry mixing apparatus of claim 1, wherein, in use, the average residence time of the aqueous foam within the vessel is within 30% of the average residence time of the other components of the stucco slurry within the vessel.

18. The stucco slurry mixing apparatus of claim 1, wherein, in use, the average residence time of the aqueous foam within the vessel is within 20% of the average residence time of the other components of the stucco slurry within the vessel.

19. A method of mixing a stucco slurry using the stucco slurry mixing apparatus as claimed in claim 1, the method comprising the steps: introducing ingredients including at least aqueous foam into the vessel via the first inlet; introducing further ingredients into the vessel via the second inlet, moving the mixing member to mix the ingredients within the vessel and removing mixed slurry from the vessel via the outlet, wherein the average residence time of the aqueous foam within the vessel is similar to the average residence time of the other components of the stucco slurry within the vessel.

20. The method of claim 19, wherein aqueous foam is the only ingredient introduced into the stucco slurry via the first inlet.

21. (canceled)

Description

DETAILED DESCRIPTION

[0065] An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

[0066] FIG. 1 is a schematic cross-sectional plan view of a first stucco slurry mixer;

[0067] FIG. 2 is a schematic cross-sectional side view of the stucco slurry mixer shown in FIG. 1;

[0068] FIG. 3 is a schematic cross-sectional plan view of a second stucco slurry mixer; and

[0069] FIG. 4 is a schematic cross-sectional side view of the stucco slurry mixer shown in FIG. 3.

[0070] FIG. 1 is a schematic cross-sectional plan view of a first stucco slurry mixer 100. The mixer 100 includes a cylindrical mixing chamber 110. A mixing arm 120 is located within the mixing chamber 110 and is configured to rotate about a central point of rotation 122. The mixing arm 120 is shown to rotate clockwise in the orientation shown in FIG. 1, but anti-clockwise rotation of the mixing arm 120 is also envisaged. Rotation of the mixing arm 120 about the point of rotation 122 defines a circular mixing path 124. The mixing path 124 shown in FIG. 1 is defined by the movement of an end 126 of the mixing arm 120.

[0071] The mixer 100 includes a first inlet 130. The mixer 100 also includes a second inlet, which will be described in more detail with reference to FIG. 2 below. The first inlet 130 includes an inlet aperture 132 in a curved wall of the cylindrical mixing chamber 110. The first inlet 130 also includes an inlet conduit 134 which extends from the inlet aperture 132. The inlet conduit 134 extends away from the mixing chamber 110 in a direction opposed to the direction of the mixing path 124. In particular, in the orientation shown in FIG. 1, the mixing path 124 has a generally upward direction at the point adjacent to the first inlet 130, and the inlet conduit 134 extends from the mixing chamber 110 in a generally downward direction.

[0072] The inlet conduit 134 of the first inlet 130 extends away from the mixing chamber 110 such that a longitudinal axis 136 of the inlet conduit 134 is parallel to, and spaced from, a first tangent 140 to the circular mixing path 124. The first tangent 140 is a tangent to the mixing path 124 at a point adjacent to the inlet aperture 132. Accordingly, ingredients, such as aqueous foam, may be introduced into the mixing chamber 110 via the first inlet 130 in a direction that is tangential to the direction of movement of other ingredients already present inside the mixing chamber 110 as they move around the mixing path 124.

[0073] The mixer 100 also includes an outlet 150. The outlet 150 includes an outlet aperture 152 in the curved wall of the cylindrical mixing chamber 110. The outlet 150 also includes an outlet conduit 154 that extends from the outlet aperture 152. The outlet conduit 154 extends away from the mixing chamber 110 in a direction toward the direction of the mixing path 124. In particular, in the orientation shown in FIG. 1, the mixing path 124 has a generally downward direction at the point adjacent to the outlet 150, and the outlet conduit 154 extends from the mixing chamber 110 in a generally downward direction. Here, the first inlet 130 and the outlet 150 are spaced from one another such that the slurry exiting the outlet 150 is substantially homogenous.

[0074] The outlet conduit 154 of the outlet 150 extends away from the mixing chamber 110 such that a longitudinal axis 156 of the inlet conduit 154 is parallel to, and spaced from, a second tangent 142 to the circular mixing path 124. The second tangent 142 is a tangent to the mixing path 124 at a point adjacent to the outlet aperture 152. Accordingly, mixed slurry may be removed from the mixing chamber 110 via the outlet 150 in a direction that is tangential to the direction of movement of the mixed slurry as it moves around the mixing path 124 inside the mixing chamber 110.

[0075] FIG. 2 is a schematic cross-sectional side view of the stucco slurry mixer 100 shown in FIG. 1. As can be seen in FIG. 2, the mixing arm 120 is positioned between the first inlet 130 and the outlet 150. The mixer 100 also includes a second inlet 160 that is shown to be on the same side of the mixing arm 120 as the first inlet 130, such that the mixing arm 120 is also positioned between the second inlet 160 and the outlet 150.

[0076] The inlet aperture 132 is positioned in the curved wall 112 of the mixing chamber 110 near to an upper surface 114 of the mixing chamber 110. The inlet conduit 134 extends away from the cylindrical mixing chamber 110 such that the longitudinal axis 136 of the inlet conduit 134 is parallel to, spaced from, and above a plane 128 in which the mixing arm 120 lies.

[0077] The outlet aperture 152 is positioned in the curved wall 112 of the mixing chamber 110 near to a lower surface 116 of the mixing chamber 110. The outlet conduit 154 extends away from the cylindrical mixing chamber 110 such that the longitudinal axis 156 of the outlet conduit 154 is parallel to, spaced from, and below a plane 128 in which the mixing arm 120 lies.

[0078] To mix a slurry with the mixer 100 shown in FIGS. 1 and 2, ingredients such as stucco, water, and any desired additives may be introduced into the mixing chamber 110 via the second inlet 160. The mixing arm 120 may then be rotated to mix the ingredients into a stucco slurry. As the slurry is moved by the mixing arm 120, foam may be introduced via the first inlet 130. Due to the tangential arrangement of the first inlet 130, the shear stresses experienced by the foam on entry to the mixing chamber 110 may be minimised. The foam may be evenly dispersed throughout the slurry due to the motion of the slurry and the movement of the mixing arm 120. Once the slurry and foam have been mixed to a desired extent, the mixed slurry may be removed from the mixing chamber 110 via the outlet 150. Due to the tangential arrangement of the outlet 150, the shear stresses experienced by the foam on exit from the mixing chamber 110 may be minimised.

[0079] FIG. 3 is a schematic cross-sectional plan view of a second stucco slurry mixer 200. The mixer 200 includes a cylindrical mixing chamber 210. A mixing disk 220 is located within the mixing chamber 210 and is configured to rotate about a central point of rotation 222. The mixing disk 220 includes several teeth 226 along its outer edge. Although the teeth 226 are shown in FIG. 3 to be spaced, the teeth 226 may be adjacent. Accordingly, more teeth 226 than shown in FIG. 3 may be provided. The mixing disk 220 is shown to rotate clockwise in the orientation shown in FIG. 3, but anti-clockwise rotation of the mixing disk 220 is also envisaged. Rotation of the mixing disk 220 about the point of rotation 222 defines a circular mixing path 224. The mixing path 224 shown in FIG. 2 is defined by the movement of an end of a tooth 226 of the mixing disk 220.

[0080] The mixer 200 includes a first inlet 230. The mixer 200 also includes a second inlet, which will be described in more detail with reference to FIG. 4 below. The first inlet 230 includes an inlet aperture 232 in a curved wall of the cylindrical mixing chamber 210. The first inlet 230 also includes an inlet conduit 234 that extends from the inlet aperture 232. The inlet conduit 234 extends away from the mixing chamber 210 in a direction opposed to the direction of the mixing path 224. In particular, in the orientation shown in FIG. 3, the mixing path 224 has a generally upward direction at the point adjacent to the first inlet 230, and the inlet conduit 234 extends from the mixing chamber 210 in a generally downward direction.

[0081] The inlet conduit 234 of the first inlet 230 extends away from the mixing chamber 210 such that a longitudinal axis 236 of the inlet conduit 234 is parallel to, and spaced from, a first tangent 240 to the circular mixing path 224. The first tangent 240 is a tangent to the mixing path 224 at a point adjacent to the inlet aperture 232. Accordingly, ingredients, such as aqueous foam, may be introduced into the mixing chamber 210 via the first inlet 230 in a direction that is tangential to the direction of movement of other ingredients already present inside the mixing chamber 210 as they move around the mixing path 224.

[0082] The mixer 200 also includes an outlet that is not shown in FIG. 3 and will be described in more detail with reference to FIG. 4 below.

[0083] FIG. 4 is a schematic cross-sectional side view of the second stucco slurry mixer 200 shown in FIG. 3. The outlet 250 includes three outlet apertures positioned in a lower surface 216 of the mixing chamber 210, with respective outlet conduits extending therefrom. The outlet conduits extend away from the outlet apertures in a direction away from the lower surface 216 of the mixing chamber 210. In the orientation shown in FIG. 4, the outlet conduits extend downwards.

[0084] As can be seen in FIG. 4, the mixing disk 220 is positioned between the first inlet 230 and the outlet 250. The mixer 200 also includes a second inlet 260 that is shown to be on the same side of the mixing disk 220 as the first inlet 230, such that the mixing disk 220 is also positioned between the second inlet 260 and the outlet 250.

[0085] The inlet aperture 232 is positioned in the curved wall 212 of the mixing chamber 210 near to an upper surface 214 of the mixing chamber 210. The inlet conduit 234 extends away from the cylindrical mixing chamber 210 such that the longitudinal axis 236 of the inlet conduit 234 is parallel to, spaced from, and above a plane in which the mixing disk 220 lies.

[0086] To mix a slurry with the mixer 200 shown in FIGS. 3 and 4, ingredients such as stucco, water, and any desired additives may be introduced into the mixing chamber 210 via the second inlet 260. The mixing disk 220 may then be rotated to mix the ingredients into a stucco slurry. As the slurry is moved by the mixing disk 220, foam may be introduced via the first inlet 230. Due to the tangential arrangement of the first inlet 230, the shear stresses experienced by the foam on entry to the mixing chamber 210 may be minimised. The foam may be evenly dispersed throughout the slurry due to the motion of the slurry and the movement of the mixing disk 220. Once the slurry and foam have been mixed to a desired extent, the mixed slurry may be removed from the mixing chamber 210 via the outlet 250.