Patent Application
20050247730
1. Technical Field
The invention relates to an apparatus for dispensing a plurality of powders, such as colorants for paint, dye, caulking or grout or components of cosmetics, and to a method of compounding substances.
2. Background of the Related Art
A prior art apparatus of this type is disclosed in U.S. patent application 2003/0230355. This document pertains to an interactive cosmetic body powder selection system having a point of sale dispenser. The system includes a cosmetic powder dispenser that contains a plurality of different shades, tints or hues of colors or pigments, which can be dispensed in pre-selected proportions to create a custom color selection. A user-interactive system is provided at a point-of-sale for allowing a user to choose or dispense a color, effect, or both. Information about the selection is employed for dispensing the appropriate proportions of ingredients. Preferably the ingredients are dispensed manually into a powder canister having an integrated brush in fluid communication with the canister. In another embodiment, the system is automated.
U.S. Pat. No. 4,959,947 relates to an apparatus for the production and packaging of a compound mixture, in which extremely accurate and rapid weighing-out, proportioning and packaging of individual components are achieved, is provided. For this, filling stations (4 to 6) are equipped with combined discharge, weighing and transfer devices (22), which allow single-component treatment. In column 4, lines 25 to 32 it is stated that “The first type of filling station 4 (individual vessels 1 to 4) illustrated in
German Utility Model 299 24 013 relates to a metering device for a powder, such as aluminum powder for making cellular concrete, which comprises a relatively large screw for generating a relatively large mass flow and a relatively small screw, which receives material from the relatively large screw.
An aspect of the present invention provides an apparatus for and method of relatively accurately and relatively quickly dispensing different amounts of powder.
In accordance with a further aspect of the invention, the said amounts vary over a wide range.
A still further aspect of the invention provides an apparatus of relatively robust construction.
The invention relates to an apparatus for dispensing a plurality of powders, such as colorants for paint, caulking-or grout or components of cosmetics, comprising a plurality of containers for holding the powders, a plurality of metering powder pumps, connected to a container or having a connector for releasably connecting a container to the respective powder pump, wherein the capacity of the metering powder pump, i.e. the amount dispensed at each revolution (in case of screw pumps) or nominal stroke (in case of a piston pumps) is selectable.
By employing metering pumps of which the capacity is selectable, the time needed for dispensing a particular amount of powder can be reduced and/or the accuracy with which this amount is dispensed can be increased. In other words, it becomes possible to optimize for speed on the one hand and accuracy on the other.
A selectable capacity can be achieved in various ways. E.g. by providing a screw pump, which can be tilted so as to lower the outlet opening and thus stimulate the flow of powder, or by providing a screw pump, wherein the screw comprises a helical wire or spring wound about a rod and wherein the effective pitch of the screw and thus the capacity can be increased respectively decreased by elongating respectively shortening the helical wire or spring. It is also possible to employ a conical screw housed in a (horizontal) conical chamber, with the outlet opening at the apex of the conical chamber. By moving the screw, in axial direction, away from or towards the outlet opening, the capacity of the powder pump can be respectively increased or decreased.
However, it is preferred that the metering powder pumps comprise at least two, preferably separated pump mechanisms, one mechanism having a relatively large dispensing capacity and another mechanism having a relatively small dispensing capacity. With such pumps, the amounts to be dispensed may vary over a wide range.
It is further preferred that the apparatus according to the invention comprises at least one weighing device for weighing at least one, preferably all of the dispensed amounts.
The invention further relates to a method of compounding substances, such as paints, dyes, caulking or grout or cosmetics, comprising the steps of
It is preferred that at least some, preferably all of the metering powder pumps comprise at least two pump mechanisms and that the method further comprises the steps of
Optimization of speed and/or accuracy is further facilitated if the said large part is at least ten times larger than the said small part.
The method according to the present invention is especially suitable for compounding substances at a point-of-sale or, in case of paint, at a paint shop.
Within the framework of the invention, the term “powder” is defined as particles having a size in a range from 0 to 1500 μm, preferably in a range from 10 to 500 μm, and at least includes granulates, microgranulates, crystals, frit, grounds, microspheres and the like.
It is noted that the drawings are not necessarily to scale and that details, which are not necessary for understanding the present invention, may have been omitted. The terms “upper”, “lower”, “horizontal”, “vertical”, “front”, “rear”, and the like relate to the embodiments as oriented in the figures. Further, elements that are at least substantially identical or that perform an at least substantially identical function are denoted by the same numeral.
This particular dispensing apparatus 1 is an automated version and includes a horizontal turntable 2, mounted on a support 3 and carrying, along its circumference, a plurality of metering powder pumps 4 and twenty-four containers 5 for the powders. The turntable 2 can be rotated about a vertical, central axis by means of a motor inside the support 3 and between discrete positions, in this case forty-eight positions (two for each container as will become apparent below) including a front or dispensing position provided with a stepper motor 6 for driving one of the pumps 4.
The apparatus 1 further comprises a control device 7 comprising a small keyboard 8 for entering information, such as client data and paint recipes, and a display 9. The control device 7 also comprises a computer 10 for storing the said information and for driving the turntable 2 and the stepper motor 6.
A weighing device 11, comprising an upper plate (shown in
As can be seen in
Inserts 17 are mounted, e.g. by means of an external screw thread, in the said channel. These inserts 17 are provided with axially extending pump chambers, which accommodate two concave profile screws 18 of different size and which can be readily replaced, e.g. when a different type or size of screw is to be fitted.
In this example, the screws 18 extend radially with respect to the turntable 2. The relatively large screw 18A has a diameter of 22 mm and a double pitch of 12 mm, yielding a dispensed volume for each revolution of 735 mm3, whereas the relatively small screw 18B has a diameter of 8.5 mm and a double pitch of 7 mm, yielding a dispensed volume for each revolution of 35 mm3. First ends of the screws 18, extending away from the central vertical axis of the turntable 2, are each provided with an adaptor 19 which is to be engaged by the stepper motor 6, as will be explained in more detail below. Further, each of the screws 18 is made of polypropylene (PP) or Teflon™ (PTFE) reinforced with a cylindrical metal rod 20.
In order to further improve the dispensing accuracy of the screws 18, the effective outer diameter of the screws 18 is in excess of the effective inner diameter the respective chamber. The rim of the screw is at least partially bent in the displacement direction of the pump. Such bending can be achieved by simply inserting the oversized screws in the channels from the outlet side towards in the inlet side.
In an alternative embodiment, which is especially suitable for fragile powders, the effective outer diameter of the screw is smaller than the effective inner diameter of the respective chamber, resulting in clearance between the screw and the chamber, and wherein the screw is provided with bristles that bridge this clearance. This type of screw was found to be effective in reducing the forces exerted on the powder.
As illustrated in
In another example, employing the weighing device 11, if the screws have an accuracy of 2%, 96% of the required amount is dispensed by the large screw 18A and the dispensed amount is verified by the weighing device 11. If it is established that e.g. 97% of the required amount has been dispensed, the large screw 18A is driven to dispense a total of 99% and the remaining part is dispensed by means of the small screw 18B.
The accuracy of the screws can be further enhanced by calibrating, relative to a reference or zero position of the screw, the dispensed amounted in several positions within one revolution, e.g. for each step of 30 degrees yielding a total of 12 steps in one revolution. By calibrating for several positions, any non-linear effects can be taken into account. These effects dependent inter alia on the dimensions and material of the screw and on the powder that is being dispensed. In some cases, the screw will dispense relatively small amounts or not dispense at all during e.g. two or three steps and then dispense a relatively large amount in the fourth step, which phenomenon could be referred to as “pulsing”. Many of these effects were found to be sufficiently regular to allow compensation by calibration.
In addition to use during dispensing, the above-described weighing device 11 can also be used to calibrate one or more of the pumps.
Once dispensing of a particular powder has been completed, the lid 16 is closed and the turntable 2 is rotated until the next required container 5 is in the dispensing position. Closing the lid 16 prevents powder from falling out during rotation. In an alternative embodiment, the screws that have just been used are revolved in reverse direction prior to rotation of the turntable thus drawing the powder back into the metering powder pump.
With the above described apparatus and method dispensing it is possible to relatively accurately and quickly dispense amounts ranging from e.g. 10 milligram to 500 gram.
As a matter of course, this disclosure is not restricted to the above-disclosed embodiments, which may be varied in different manners within the spirit and scope of the invention. For example, the apparatus according to the present invention can be configured as a linear dispensing apparatus i.e. with the containers aligned is a row. Also, the apparatus may comprise at least one container for a liquid and a metering liquid pump connected to that container.
