WO2010108449A1

WO2010108449A1 - Improved paint mixing device

Info

Publication number: WO2010108449A1
Application number: PCT/CN2010/071332
Authority: WO
Inventors: Shun Pui Andrew Chiu
Original assignee: Shun Pui Andrew Chiu
Priority date: 2009-03-27
Filing date: 2010-03-25
Publication date: 2010-09-30
Also published as: CN201537475U

Abstract

An improved paint mixing device for matching paint color is disclosed. The device includes a paint nozzle (2). A sensor (3) and an image taking unit capable of at least taking images from different directions are arranged below an outlet of the paint nozzle (2).

Description

Improved Paint Mixing Device

Technical Field

The present invention relates generally to the field of mechanical equipment, and in particular to an improved paint mixing device used for producing coloured paints.

Background Art

Conventional paint mixing devices essentially consist of a means for discharging a specific coloured tinter into a paint bucket or container, the tinter or tinters being selected to produce a coloured paint according to a predefined colour recipe. The amount of tinter required is included as part of the recipe Afterwards, the discharged tinters are uniformly mixed (for example by shaking the paint container) to obtain a paint of the desired colour. The paint container will typically contain a base paint which displays all the properties of a conventional paint without the presence of any tinters. The combination of the base paint and the desired amount of tinter produces a coloured paint which is then suitable for application to a painting surface. Such a mixing device is often located inside a store at the point of sale thereby enabling a consumer to choose a tinted paint colour and have that paint colour mixed immediately. Such a mixing device is referred as an in-store tinting device and allows a consumer to choose from a larger selection of paint colours when compared to those paints already mixed at the paint processing plant.

To achieve accurate and reproducable paint colours using this method it is essential that the correct amount of tinter is discharged into the paint container otherwise the desired final paint colour is not obtained. In an attempt to alleviate the disadvantages of prior art paint mixing devices, the applicant of the present invention has proposed paint mixing devices in two Chinese patent application Nos. 200520065534.9 and 200610035665.1. The paint mixing devices described therein adopt high precision image detection techniques for measuring the paint flow rate. The calculating method is described in detail as follows. i As shown in Fig.1 , an image detector adopted in these prior designs comprises a light-emitting part 11 and a light-receiving part 12. A paint discharger 10 has an outlet arranged above an intermediate position between the light-emitting part 11 and the light-receiving part 12. Upon activation of the image detector, a net of light is established between the light-emitting part 11 and the light-receiving part 12. When paint is discharged from the outlet, it will inevitably pass through the net of light. When the paint passes through the net, the cross section of a paint cylindrical drop or droplet 13 cut by the net of light can be measured very accurately by the image detector. Next, the principle of calculation will be described in detail with reference to the paint droplet 13. Fig.2a shows a paint droplet 13 with a height L and a cross section S at an arbitrary position, with the cross section S being approximated as a circle. When the paint droplet 13 is divided into n sections along its longitudinal direction, each of these sections can be regarded as a circular cylinder with a respective height L1 , L2, L3... Ln as well as a respective sectional area S1 , S2, S3... Sn. Thus, the approximate volume V of the paint droplet 13 may be calculated by V=L1 ^*S1 +L2^*S2+L3^*S3+... +Ln^*Sn. Turning to Figs. 2b and 2c, the overall height of the paint droplet 13 can be calculated as long as its velocity has been obtained. In this case, the total volume of the paint droplet passing through the net of light can be calculated by determining sectional areas of the droplet at different moments. Specifically, the diameter and thus the area of each section of the paint droplet can be determined from the width of the section detected by the image detector when the paint droplet passes through the net of light. For example, during the course that the paint droplet passes through the net of light, the image detector measures, at a substantially small time interval t (small enough), the cross section of the paint droplet 13, such that a total of four cross sectional areas s1 , s2, s3 and s4 are obtained at moments t1 , t2, t3 and t4, respectively. In case of a flow velocity v of the paint droplet 13, the volume V of the paint droplet 13 may be calculated by V=s1 ^*vt1 +s2^*vt2+s3^*vt3+s4^*vt4. As long as the time interval t is small enough, the volume of the paint flow may be calculated accurately. However, the calculating method as described above is based on an assumption: the paint droplet (or cylindrical drop) is regular in shape, i.e. it has a circular section. The applicant has discovered that in practice the shape of the paint droplet (or cylindrical drop) is irregular due to many factors such as air resistance, surface tension, etc.. In Fig. 3, a paint cylindrical drop 14 of irregular shape is shown. Images of the paint cylindrical drop taken from different directions by a high speed digital camera are different from each other. As illustrated, the image 141 taken from a direction X is quite different from the image 142 taken from a direction Y. In this case, if the width DX of the paint cylindrical drop obtained by measuring the image taken from the direction X is taken as the diameter of the paint cylindrical drop, the calculated total volume of the paint cylindrical drop will be significantly larger than the volume calculated based on the width DY of the paint cylindrical drop obtained by measuring the image taken from the direction Y. Thus, for irregular paint cylindrical drops, a total volume obtained by the current method might not be correct, and a measuring error caused thereby should be adjusted. If not, the colours of the paint thus mixed might be deviated from what is desired. In view of this, the inventor proposed the present invention.

Summary of the Invention The technical problem to be solved by the present invention is to overcome the drawbacks existing in prior art paint mixing devices by providing an improved paint mixing device capable of accurately measuring a paint flow rate.

Specifically, the present invention provides an improved paint mixing device comprising a paint nozzle, a sensor and an image taking unit capable of at least taking images from different directions are arranged below an outlet of the paint nozzle.

Preferably, the image taking unit comprises at least three digital cameras arranged in different directions and distributed radially with respect to a central axis of the outlet of the paint nozzle.

Preferably, the image taking unit comprises one digital camera and at least two mirror imaging devices associated with the digital camera.

Preferably, the mirror imaging devices are arranged at an angle of 120 degrees with respect to each other, the digital camera is arranged on an angular bisector of the angle, and the digital camera and the mirror imaging devices are distributed radially with respect to a central axis of the outlet of the paint nozzle.

Preferably, the mirror imaging devices are glass mirrors.

Preferably, the sensor is an infrared sensor.

A paint container is provided below the sensor and the image taking unit, and is arranged below the paint nozzle, The digital camera comprises a light source.

The sensor comprises an infrared generator and an infrared receiver. The infrared receiver comprises a light shielding plate provided with two slots for light to pass through. A sensing unit is arranged right behind the slots.

The principle of the measuring method according to the present invention is the same with that of the prior art. The difference lies in that: in the prior art measuring method, only one group of data is collected, that is to say, the data is obtained from a 2-dimensional image (i.e., a width of a paint cylindrical drop obtained by measuring an image taken from one direction is taken as the approximate diameter of the section of the cylindrical drop); while in the present invention, an image taking unit capable of at least taking images from different directions is used, i.e. the paint cylindrical drop is measured in a 3-dimensional way, and reference volumes are calculated based on the data of the images taken from different directions, so as to obtain a resultant volume by averaging all reference volumes. Therefore, the measurement accuracy can be improved considerably. As compared with prior art paint mixing devices, the paint mixing device according to the present invention may calculate the volume of irregular paint cylindrical drops (or droplets) more accurately, thus reduce the error to a minimum level. Brief Description of the Drawings

The present invention will be described in detail below with reference to the accompanying drawings, in which:

Fig.1 is a schematic diagram of an image detector used in a prior art paint mixing device;

Fig. 2 shows the principle of measuring the paint volume in a prior art paint mixing device;

Fig.3 shows an irregular paint cylindrical drop and its images taken from different directions; Fig.4 is a schematic diagram of a first embodiment of the present invention;

Fig.5 shows schematically an operation of an image taking unit 4 according to the first embodiment of the present invention;

Fig.6 shows schematically images taken from three directions according to the first embodiment of the present invention; and Fig.7 is a schematic plan view of an image taking unit according to a second embodiment of the present invention.

Detailed Description of the Preferred Embodiments

Fig.4 shows schematically a paint mixing device, for example an in-store paint mixing device, according to a first embodiment of the present invention, which comprises a paint nozzle 2 for dispensing tinter, a sensor 3 arranged at an outlet of the paint nozzle 2, an image taking unit capable of at least taking images from different directions, and a paint container 5, wherein the paint container 5 is placed below the sensor 3 and the image taking unit 40, and is below the paint nozzle 2. For the paint nozzle 2 and other components of the paint mixing device, please refer to Chinese patent application Nos. 200520065534.9 and 200610035665.1 for more detail. Tinter is discharged from the paint nozzle 2 and then flows into the paint container 5.

According to the first embodiment, the sensor 3 is an infrared sensor comprising an infrared generator 31 and an infrared receiver 32. The infrared receiver 32 comprises a light shielding plate 321 in which two slots 322 are provided for light to pass through. A sensing unit 323 is arranged right behind the slots 322.

The image taking unit of the first embodiment comprises one digital camera 40 and at least two mirror imaging devices 41 , 42 associated with the digital camera 40. The mirror imaging devices 41 , 42 are glass mirrors arranged at an angle of 120 degrees with respect to each other, and the digital camera 40 is arranged on an angular bisector of the angle. The digital camera 40 and the mirror imaging devices 41 , 42 are distributed radially around a central axis of the outlet of the paint nozzle 2, i.e. paint cylindrical drops or droplets discharged from the paint nozzle 2 pass through the center of an area including the digital camera 40 and the mirror imaging devices 41 , 42.

According to the first embodiment, the sensor 3, the image taking unit and the paint container 5 are usually arranged inside the device, thus may suffer from insufficient illumination. In order to take images with high quality, the digital camera 40 may comprise a light source 401.

The paint mixing device according to the first embodiment operates as follows. When paint is discharged from the paint nozzle 2, a paint cylindrical drop 6 (or a paint droplet) will pass through the sensor 3. During the course of its falling down, the paint cylindrical drop 6 moves across between the infrared generator 31 and the infrared receiver 32, shields the two slots 322 in the light shielding plate 321 and thereby activates the sensing unit 323 arranged right behind the slots 322. The sensing unit 323 will in turn activate the digital camera 40 to take images of the paint cylindrical drop 6. The taken images are then sent to a processing unit for calculation. According to the present invention, a sub-volume of each segment of the paint cylindrical drop 6 passing through during each time interval is calculated with the calculating method described above, and then the total volume of the paint cylindrical drop 6 is obtained by summing up all the sub-volumes.

Different from the prior art 2-dimensional calculating method, a 3-dimensional calculating method is adopted according to the present invention to compensate the error caused by the 2-dimensional calculating method. As shown in Figs. 5 and 6, since the image taking unit 4 comprises one digital camera 40 and two mirror imaging device 41 , 42 associated with the digital camera 40, three images of the paint cylindrical drop 6 can be taken by the digital camera 40, with one of the three images being a direct image 62 directly taken by the digital camera 40 and the other two being mirror images 61 , 63 reflected in the mirror imaging devices 41 , 42. For a regular paint cylindrical drop 6, these three images are identical, and the volumes of the paint cylindrical drop calculated based on these three images are the same as well. However, for an irregular paint cylindrical drop, these three images are different from each other.

As shown in Figs. 5 and 6, the direct image 62 has a width different from that of the mirror images 61 , 63; thus, for the same physical paint segment, there exists three image segments 611 , 621 , 631 corresponding to the images 61 , 62 and 63 respectively, while the calculated sub-volumes of these segments 611 , 621 , 631 are different from each other. According to the present invention, the resultant volume of the physical paint segment is an average of these three sub-volumes. Assuming that the image segments 611 , 621 , 631 corresponding to the direct image 61 and the mirror images 62, 63 respectively have a width of D1 , D2 and D3 (the horizontal dimension when viewing Figure 6) and a height of dt, the sub-volumes of the image segments 611 , 621 , 631 can be calculated as:

V1 = π (D1/2)^{2 *} dt

V2 = π (D2/2)^{2 *} dt

V3 = π (D3/2)^{2 *} dt and the average sub-volume Vt of the physical paint segment can be calculated as Vt = (V1 +V2+V3)/3.

Finally, the total volume of the paint cylindrical drop 6 can be calculated as a summation of the sub-volumes of all paint segments.

With such a calculating method, the volume of an irregular paint cylindrical drop or droplet 6 can be accurately calculated with a reduced error.

Fig.7 shows a second embodiment of the present invention. In the first embodiment, only one camera 40 is used and images from other directions are provided by the two mirror imaging devices 41 , 42. By doing so, the number of digital cameras can be reduced and respective images can be taken synchronously. However, of course, it is possible to use three digital cameras 40 to take images directly. As shown in Fig.7, the image taking unit 4 according to the second embodiment comprises three digital cameras 40 arranged in different directions. The digital cameras 40 are distributed radially with respect to the central axis of the outlet of the paint nozzle 2. The same effect as in the first embodiment can be achieved as long as the cameras 40 operate synchronously.

Of course, it is not intended to limit the images of the paint cylindrical drop to be taken only within three directions; instead, one can take more images from more different directions according to practical needs. Essentially, the more images are taken, the more accurate the calculated volume of the paint cylindrical drop can be. As to how to increase the number of images taken from different directions, one may arrange more mirror imaging devices according to the first embodiment, or alternatively arrange more digital cameras according to the second embodiment.

As compared with a prior art paint mixing device, the paint mixing device according to the present invention is capable of calculating the volume of irregular paint cylindrical drops (or droplets) more accurately, and of reducing the error to a minimum level.

The embodiments as described above are preferred ones of the present invention and are not intended to limit the scope of the present invention. All the modifications or variations made with reference to the shape, configuration, features and spirit as described herein are within the scope of the present invention.

Claims

1. An improved paint mixing device comprising a paint nozzle (2), characterized in that a sensor (3) and an image taking unit capable of at least taking images from different directions are arranged below an outlet of the paint nozzle (2).

2. The improved paint mixing device according to claim 1 , characterized in that the image taking unit comprises at least three digital cameras (40) arranged in different directions and distributed radially with respect to a central axis of the outlet of the paint nozzle (2).

3. The improved paint mixing device according to claim 1 , characterized in that the image taking unit comprises one digital camera (40) and at least two mirror imaging devices (41 ) associated with the digital camera (40).

4. The improved paint mixing device according to claim 3, characterized in that the mirror imaging devices (41 ) are arranged at an angle of 120 degrees with respect to each other, the digital camera (40) is arranged on an angular bisector of the angle, and the digital camera (40) and the mirror imaging devices (41 ) are distributed radially with respect to a central axis of the outlet of the paint nozzle (2).

5. The improved paint mixing device according to claim 3, characterized in that the mirror imaging devices (41 ) are glass mirrors.

6. The improved paint mixing device according to any one of claims 1 to 5, characterized in that the sensor (3) is an infrared sensor.

7. The improved paint mixing device according to any one of claims 1 to 5, characterized in that a paint container (5) is provided below the sensor (3) and the image taking unit and is arranged right below the paint nozzle (2).

8. The improved paint mixing device according to any one of claims 2 to 5, characterized in that the digital camera (40) comprises a light source (401 ).

9. The improved paint mixing device according to claim 6, characterized in that the sensor (3) comprises an infrared generator (31 ) and an infrared receiver (32), wherein the infrared receiver (32) comprises a light shielding plate (321 ) provided with two slots (322) for light to pass through, and a sensing unit (323) is arranged right behind the slots (322).