MIXING APPARATUS

Abstract: A container (1) for liquid and semi-liquid materials such as paint has a bottom wall (2) and a side wall (3). A mixing device (6) is provided in the container, the device having a planar mixing head (7) disposed substantially parallel to the bottom wall (3), and a limb (8) which extends substantially perpendicularly from a peripheral edge region of the mixing head adjacent to the side wall (2) of the container. A coupling (9) is provided in the container for releasable connection with an external handle by which the mixing device is reciprocated vertically to agitate and mix the contents of the container. The handle may have a flattened end for removing a lid (4) from the container.

Description: MIXING APPARATUS TECHNICAL FIELD OF THE INVENTION This invention relates to the mixing of liquid and semi-liquid materials (hereinafter referred to collectively as "liquids"). BACKGROUND Many liquids such as paints and varnishes require mixing prior to use, and ideally, many require periodic mixing throughout the period of use to prevent separation of the contents or to ensure that the surface layer does not become thick through evaporation. The most common method of mixing liquids in small containers such as paint tins is to stir them with a stick, but this is a very inefficient method of mixing and also presents a problem of disposal when the stick remains coated with the liquid. When mixing liquids on a larger scale a common form of mixing device is a motorised impeller, but this is not very efficient for mixing viscous materials, and impellers are not easy to clean. Furthermore, the impeller and its associated drive system can impede access to the interior of the container, e.g. for inspection and cleaning purposes. The present invention seeks to provide a new and inventive form of mixing apparatus. SUMMARY OF THE INVENTION The present invention proposes mixing apparatus which includes: - a liquid container having a bottom wall and a side wall; and - a mixing device having a generally planar mixing head disposed substantially parallel to said bottom wall, and a limb which extends substantially perpendicular from a peripheral edge region of the head adjacent to the side wall of the container for moving the mixing head up and down in said liquid. Since the mixing head is normally disposed adjacent to the bottom wall of the container and the limb is disposed adjacent to the side wall the mixing device does not significantly impede access to the contents of the container. Thus, if the liquid is paint for example, after the initial mixing the device can remain in the container while the paint is removed, allowing the paint to be periodically agitated. A preferred aspect of the invention is that the limb is provided with reciprocating means for moving the mixing head, the reciprocating means being located above the container and coupled to the limb by releasable connection means In the case of a small container such as a paint tin the releasable connection is preferably located within the container so that the mixing device can remain within the container allowing the container to be resealed if desired The mixing device can be manufactured relatively cheaply so that it can be disposed of with the container In a simple form the reciprocating means may comprise a grasping handle for attachment to the limb externally of the container so that the handle may be grasped clear of the liquid without risk of major contamination with the liquid The handle can be reused a number of times with the same or another mixing device The mixing head could be of various shapes and configurations depending on the nature of the liquid being mixed The mixing head preferably contains at least one aperture and preferably covers between 30 and 60 percent of the area of the bottom wall of the container As the mixing head approaches the bottom of the container a high laminar flow is created at the bottom of the container which has the effect of carrying any settled materials into the body of the liquid When the mixing head is static a proportion of any settled materials will lie on top of the mixing head and be lifted with it assisting the re-mixing BRIEF DESCRIPTION OF THE DRAWINGS The following description and the accompanying drawings referred to therein are included byway of non-limiting example in order to illustrate how the invention may be put into practice In the drawings Figure 1 is a vertical section through mixing apparatus in accordance with the invention; Figure 2 is a longitudinal section through a handle for use with the mixing apparatus; and Figures 3 to 7 are plan views of the mixing apparatus showing various modifications thereof. DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to Fig. 1 , a paint container or can 1 of metal or plastics has a circular bottom wall 2, a cylindrical side wall 3 and a press-fit lid 4. The container is substantially filled with liquid paint such that there is a small air gap between the surface 5 and the lid 4. A mixing device 6 is supplied inside the can. The device can be formed of metal or plastics and includes a mixing head 7 and an upstanding limb 8. The head 7 is substantially planar so that it rests on the bottom wall 2. The limb 8 may take the form of a round rod which projects above the level of the liquid to terminate in a screw-threaded coupling 9 of reduced diameter. The rod is secured at the peripheral edge of the mixing head 8 to stand adjacent to the side wall of the can but with the coupling 9 accessible within the can opening. Referring to Fig. 2, a separate reusable handle 10 is provided. The handle is of elongate shape and has an internally screw-threaded socket 11 at one end for releasable connection with the coupling 9. The blind end of the socket may be provided with an intercepting cross-bore 12 for the escape of trapped air or liquid. Thus, when the lid is removed from the container the handle will project co-axially with the limb 8 allowing the mixing device to be gripped in the hand and moved up-and-down through the liquid. The turbulence thereby created as the paint flows through and/or around the mixing head 7 creates an effective mixing action which ensures thorough mixing of the paint in a relatively short period of time. The upper end of the handle may be formed into a flattened blade 14 which can be utilised for levering the lid from the paint can. The handle could be a plastic moulding, shaped to be aesthetically pleasing and comfortable to hold. Other releasable means of attachment could be used, e.g. a releasable spring-loaded clip or an insert-and-twist bayonet type fitting. The flat mixing head 7 should be shaped to locate within the can 1 so that the limb 8 is located within the top opening where it will be readily accessible for the handle to be attached. When the can lid is fitted the mixing device is located against axial or lateral movement within the can. If the mixing device is put into a finished can it must be capable of being passed through the can opening, e.g. by tilting or flexing. On the other hand it may be practicable to incorporate the mixing device into the can during its manufacture. If the mixing devices are formed of a material which is denser than the liquid in the can then the mixing devices may locate loosely in the can as the mixing device will naturally sink. On the other hand, if they are made of a material less dense than the liquid the can so that they will naturally float it will be desirable to prevent this by shaping the mixing head to contact the can and generate sufficient frictional resistance that they will stay where they are put. In general metal mixing devices will naturally sink and may be a loose fit whereas plastic mixing devices will need to contact the can wall. The mixing head 7 will be tailored to suit the material to be mixed. As a general rule thick materials require a mixing head of smaller surface area and thin materials require a head of larger surface area. If the mixing devices are of plastic then the limb 8 can be moulded integral with the mixing head. If they are to be supplied separately from the can it would be advantageous if the mixing devices stack on top of each other offering easier handling and storage. This could be achieved by making the limbs tapered and hollow. To prevent air being trapped when the cans are filled or a pocket of material being trapped during mixing the limbs could have a slot up one side. The tapered shape could be a simple cone but a three or four sided pyramid shape would not only stack but locate the mixing devices which would be advantageous when removing them from the stack for placing in the can. The use of such mixing devices is not restricted to cylindrical cans. Square or rectangular containers could also be used. Nor are the mixing devices restricted to containers with a large opening. If the mixing device is incorporated into the container during its assembly and the limb 8 is suitably positioned it could be accessed through a restricted screw top opening allowing the materials to be mixed prior to pouring out for use. In use it is envisaged that the mixing device will be placed in the can prior to being filled with material and the lid fitted. The end user will open the can using the handle, exposing the top of the limb above the material. The handle is then attached to the limb and the material mixed by moving the mixing device up and down. The handle may remain attached during use as its position at the edge of the can opening will not impede access to the material with a brush making frequent mixing during use very easy. The handle can be detached and the lid refitted at any time when the user has finished. The very bottom of the handle might possibly come into contact with the material and this may be cleaned off at the same time and with the same solvent as used for cleaning the brush, or it may be left to dry. The mixing device can be manufactured relatively cheaply as a disposable item which is simply discarded with the container and is never cleaned. The outline of the head 7 may be of various planar shapes, e.g. triangular as in Fig. 3, square as in Fig. 4, substantially circular as in Fig. 5, Y-shaped as in Fig. 6, or cruciform as in Fig. 7, all of which can be manipulated into a can after manufacture. The area of the head may be reduced by cutting one or more shaped or circular holes from the centre region if appropriate. The invention thus provides a simple mixing system offering convenience to the user, effective mixing, with a mixing head tailored to the materials, allowing easy access with a brush, entailing little or no cleaning, and which is available all the time that the materials are in use. Thorough mixing can generally be achieved in 30 to 40 strokes of the mixing device. The invention is particularly useful for mixing coloured paints. The paint cans can contain a base colour while measured quantities of colouring materials are supplied separately, e.g. in small sachets or disposable syringes. Thus, stores are no longer required to carry large stocks of ready- mixed paints which take up considerably more storage space. In the case of a container having a screw cap it would be possible to attach the arm of the mixing device to the cap so that the cap can be used as a handle to move the mixing deice up and down. Although the above example concerns a small container, i.e. a paint can, it is possible to use a scaled-up version of the mixer for bulk mixing of liquids. The handle would be replaced by a reciprocating motor connected to the limb by a releasable coupling to allow the motor to be used with different mixing devices and the container to be sealed when required. There is thus easy access to the interior of the container, e.g. for inspection purposes, and the mixer is easily cleaned, for example by lowering a spray ball into the container to wash above and below the mixing head. It will be appreciated that the features disclosed herein may be present in any feasible combination. Whilst the above description lays emphasis on those areas which, in combination, are believed to be new, protection is claimed for any inventive combination of the features disclosed herein.

Claims: CLAIMS 1. Mixing apparatus which includes: - a liquid container having a bottom wall and a side wall; and - a mixing device having a generally planar mixing head disposed substantially parallel to said bottom wall, and a limb which extends substantially perpendicular from a peripheral edge region of the head adjacent to the side wall of the container for moving the mixing head up and down in said liquid. 2. Mixing apparatus according to Claim 1 , in which the limb is provided with reciprocating means for moving the mixing head, the reciprocating means being located above the container. 3. Mixing apparatus according to Claim 2, in which the reciprocating means is manually operable. 4. Mixing apparatus according to Claim 3, in which the reciprocating means includes a grasping handle. 5. Mixing apparatus according to Claim 3, in which the reciprocating means includes a flattened blade. 6. Mixing apparatus according to Claim 2, in which the reciprocating means is and coupled to the limb by releasable connection means. 7. Mixing apparatus according to Claim 6, in which the releasable connection is located within the container. 8. Mixing apparatus according to Claim 1 , in which the mixing head contains at least one aperture. 9. Mixing apparatus according to Claim 1 , in which the mixing head covers between 30 and 60 percent of the area of the bottom wall of the container. 10. Mixing apparatus according to Claim 1 , in which the mixing head is of substantially triangular, square, circular, Y-shaped or cruciform profile.

Inventors: ROGERS CHRISTOPHER ROY, SMITH RICHARD TIPTON, ROGERS, CHRISTOPHER, ROY, SMITH, RICHARD, TIPTON
Applicants: ROGERS CHRISTOPHER ROY, SMITH RICHARD TIPTON, ROGERS, CHRISTOPHER, ROY, SMITH, RICHARD, TIPTON
Application year: 2001
Main classification: B01F11
IPC codes: B01F11, B01F13, B44D3