EP1669132A2

EP1669132A2 - A mixer head

Info

Publication number: EP1669132A2
Application number: EP05388106A
Authority: EP
Inventors: Sonny Andersen; Ronny Andersen; Tommy Andersen
Original assignee: Soroto Maskiner ApS
Current assignee: Soroto Maskiner ApS
Priority date: 2004-12-10
Filing date: 2005-12-07
Publication date: 2006-06-14
Also published as: EP1669132A3

Abstract

Mixer head (1) for a portable power-driven compulsory mixer (2), said mixer head (1) comprising a first end (3) remote from the mixer, a second end (4) near the mixer and an axis of rotation (5), the mixer head (1) further comprising mixing means arranged between the first end and the second end.

To provide a more efficient mixer head, the mixer head by rotation about the axis of rotation (5) defines a working space having the shape of a truncated cone with a diameter (d) at the first end (3) being smaller than a diameter (D) at the second end (4).

Description

The present invention relates to a mixer head for a portable power-driven compulsory mixer, said mixer head comprising a first end remote from the mixer, a second end near the mixer and an axis of rotation, the mixer head further comprising mixing means arranged between the first end and the second end.
Mixing building materials, such as concrete, mortar etc. is exhausting even when mixing small amounts in a bucket. Portable power-driven mixers for building materials are well known in the art, and a large variety of designs have been employed over the years. One such power-driven mixer is known from DE-A1-102 51 109. This mixer comprises a mixer head with a mixer arm provided with a spiral mixing arrangement.
Another power-driven mixer with a common mixer head is disclosed in EP-A2-1 256 374. This mixer head comprises a helical strip element.
Those prior art mixer heads are found to be relatively inefficient, in that time needed to provide a satisfactory mixing of materials having low miscibility is relatively high.
It is hence an object of the invention to provide a more efficient mixer head.
To achieve this object the mixer head as mentioned in the introduction is characterised in that the mixer head by rotation about the axis of rotation defines a working space having the shape of a truncated cone with a diameter at the first end being smaller than a diameter at the second end. A mixer head having this geometry is found to provide convincing results with regard to efficiency of mixing materials having relatively low miscibility.
The truncated cone may have any suitable conicity, however according to an embodiment, the truncated cone has a conicity of between 1 and 15°, preferably in the interval of 7-11°, which is found to provide a fair compromise. Further this conicity is relatively close to the conicity of common bricklayer's buckets, so a person using a mixer having a mixer head with a conicity within this range does not need to tip the mixer to follow the contour of the bucket wall. This both enhances the efficiency of mixing, as the risk of un-mixed materials near the bucket wall is reduced, and relieves the user of tiring work postures.
The mixer head may be provided with any type of mixing means, such as paddles or the like. According to an embodiment, however, the mixing means comprises at least one helical strip, which provides a good mixing at a modest manufacturing cost.
To provide an efficient mixing and scraping off residual material near a vessel wall, such as a bricklayer's bucket, the at least one helical strip may have an edge remote from the central axis of rotation, said edge being arranged to closely follow the envelope surface of the truncated cone.
The mixer head may be made of any suitable material, such as a plastic material, but in an embodiment the mixer head is made of metal, which will provide a wear resistant mixer head.
To minimize the risk that the mixer head will damage a vessel wall, the mixer head may further comprise a ring element at the first end. Hereby any potentially sharp points on the mixer head are avoided, and further a mixer having such a mixer head will be more easy to hold, as the mixer will be less prone to vibrate.
To further minimize the risk of the mixer head damaging the vessel during use, the mixer head may comprise a ring element at the second end. Further such a ring will further reduce the risk of vibration of the mixer, as the outer contour of the mixer head would be round with no irregularities.
The mixer head may be provided with a coupling for connection to a separate shaft. According to an embodiment, however, the mixer head comprises a shaft arranged at the axis of rotation for rotation of the mixer head. Such a mixer head with a shaft will facilitate being driven by a power-drill or a power-mixer.
In the following the invention will be more thoroughly explained by way of example and with reference to the schematic drawing, in which

Fig. 1 illustrates a prior art mixer head,
Fig. 2 illustrates use of the mixer head according to Fig. 1,
Fig. 3 illustrates a mixer head according to the invention,
Fig. 4 depicts a mixer with the mixer head according to Fig. 3 used in a bricklayer's bucket, and
Fig. 5 is a sectional view of an embodiment of the mixer head.

The prior art mixer head 100 illustrated in Fig. 1 is of cylindrical outline. The mixer head 100 with cylindrical outline is however found to have some disadvantages when used with a portable power-driven compulsory mixer 2 as seen in Fig. 2. As an example, if the mixer is used to mix a material 21 in a vessel 14 having inclined walls, such as a bricklayer's bucket, the operator must tilt the mixer to follow the wall. Otherwise there is a risk of residual material at the vessel walls as indicated by 101, i.e. poor mixing. When the mixer is tilted, there is an increased risk of splash from the mixer head, i.e. a risk of material being splashed around and out of the vessel due to centrifugal force as illustrated by 102. Further to provide an efficient mixing, the operator must carefully work round the vessel in a tiring work posture with a tilted mixer. Moreover the resulting work circle is relatively large as will be understood from Fig. 2.
In Fig. 3 is seen a mixer head 1 according to the invention. The mixer head 1 has a first end 3 remote from a mixer 2 and a second end near the mixer 2, as can be seen in Fig. 4. At the first end 3 of the mixer head 1 the diameter is d, whereas at the second end 4, the diameter is D, and as can be seen D>d. By rotation of the mixer head 1 about the axis of rotation 5 by means of a shaft 15, the mixer head 1 defines a working space having the shape of a truncated cone as schematically illustrated. The truncated cone has a conicity a, which is somewhat exaggerated in the drawing to illustrate the principle.
The mixer head 1 can be used with a portable power-driven compulsory mixer 2 of the type widely used for mixing cement, mortar, concrete, adhesives, paint and the like, especially by bricklayers at building sites. Such a mixer 2 having handles 20 and incorporating the mixer head 1 of the invention is illustrated in Fig. 4. In Fig. 4, the mixer 2 and mixer head 1 is used in a conical vessel 14, such as a common bricklayer's bucket, to mix a material 21. Such buckets are widely used and come in different sizes, however all more or less conical in shape. Typically the smallest buckets have the largest conicity, and the widely used 10-liter bucket has a conicity of approximately 10°. In Fig. 4 is illustrated how the mixer head 1 relatively closely follows the contour of the wall of the vessel 14, so the risk of un-mixed residuals at the wall is greatly reduced, and hence the efficiency of the mixer is improved. Experiments have shown that the time needed for a satisfactory mixing of colour powder into adhesive could be reduced by approximately 1/3 from approximately 60 s to about 40 s.
In Fig. 5 is seen an embodiment of the mixer head 1 in sectional view. The mixer head comprises a shaft 15 (only a small portion illustrated) by which the mixer head is rotated. A spoke 18 connects the shaft 15 to a first ring element 8, and correspondingly a spoke 17 connects the shaft 15 to a second ring element 9, which will provide a very rigid and robust construction. If the requirement for robustness is less strict, it may be enough to connect the shaft 15 to one of the spokes 17, 18. It is currently preferred to have an open ring element 8, 9, but a disk could be used as an alternative, although mixing is expected to be less efficient. The mixer head 1 illustrated in Fig. 5 comprises a helical strip element 6, which travels from one end of the spoke 17 to an opposite end of the spoke 18. A similar further helical strip element would normally be provided, but is left out in the drawing for the sake of clarity.
By rotation of the mixer head 1, the helical strip element 6 defines a working space having the shape of a truncated cone with an envelope surface 16. The helical strip element 6 is shaped so an outer edge 10 of the strip element 6 will closely follow the envelope surface 16.
The helical strip element shown is particularly useful, but other types of mixing means could be used, such as arms projecting from the shaft or the like. The helical strip element may have any width, based among other factors on a compromise between mixing efficiency and power consumption.
The conicity of the mixer head 1 could be chosen to closely match the conicity of the most widely used vessel. Alternatively a set of mixer heads 1 with different conicity within the normal range of up to 20° could be provided, so the operator would be able to find a suitable mixer head for any vessel. Currently a range of conicity of the mixer head 1 in the interval of approximately 7-11° is preferred, as the walls of bricklayer's buckets normally differ from a cylindrical shape by 8-10°. It will be appreciated that by choosing a mixer head having a conicity larger than the vessel, the circle the operator must operate will become smaller, which may be an advantage in some cases, so a mixer head having a conicity of e.g. 15° or 20° could be used.
A prototype of the invention comprised a mixer head having a length of 14 cm between the first end and the second end. The diameter D of the second end was 10 cm, whereas the diameter d of the first end was 8 cm. The mixer head with these dimensions was found to provide good mixing efficiency with a portable power-driven mixer when used in a 10 I bucket.
The mixing means may be arranged to impart an upward or downward motion to the material to be mixed, or be adapted to impart both upward and downward motion at the same time. Further the mixing means may be arranged for rotation clockwise or counter-clockwise. Moreover it will be evident to the skilled person that two or more mixing heads may be arranged to be driven by a common mixer.

Claims

A mixer head (1) for a portable power-driven compulsory mixer (2), said mixer head (1) comprising a first end (3) remote from the mixer, a second end (4) near the mixer and an axis of rotation (5), the mixer head (1) further comprising mixing means arranged between the first end and the second end characterized in that the mixer head by rotation about the axis of rotation (5) defines a working space having the shape of a truncated cone with a diameter (d) at the first end (3) being smaller than a diameter (D) at the second end (4).
A mixer head (1) according to claim 1, wherein the truncated cone has a conicity of between 1 and 15°, preferably in the interval of 7-11°.
A mixer head (1) according to claim 1 or 2, wherein the mixing means comprises at least one helical strip (6).
A mixer head (1) according to claim 3, wherein the at least one helical strip has an edge (10) remote from the central axis of rotation, said edge (10) being arranged to closely follow the envelope surface (16) of the truncated cone.
A mixer head (1) according to any of the claims above, wherein the mixer head (1) is made of metal.
A mixer head (1) according to any of the claims above, further comprising a first ring element (8) at the first end (3).
A mixer head (1) according to any of the claims above, further comprising a second ring element (9) at the second end (4).
A mixer head (1) according to any of the claims above, further comprising a shaft (15) arranged at the axis of rotation (5) for rotation of the mixer head (1).