The present invention relates to a measuring device for analysis of particles.

The measuring device comprises

- a first feeding chute and a consecutive second feeding chute,

- the first feeding chute and the consecutive second feeding chute are arranged so that the first feeding chute is arranged above the consecutive second feeding chute, so that the particles of a flow of particles that falls from a free open end of the first chute is controlled in order for said particles to be delivered in free fall onto the consecutive second feeding chute,

- the feed rate of the feeding chutes are controlled by signals from camera units, which signals are analyzed by a computer unit, whereby the particles at the consecutive second feeding chute are separated before they fall out over the edge at the open end of the consecutive second feeding chute.

The invention concerns especially the analysis of the size of particles in a sample. Within the scope of the present invention the sample can also be used to analyze, diagnose, test other features of the particles or objects in a sample, such as e.g. the color and the shape.

The invention concerns especially analyzes of small particles, however much larger objects can also be analyzed using the measuring device in accordance with the present invention. As examples of larger objects can e.g. be mentioned potatoes and apples, but even larger objects may be analyzed using the measuring device of the present invention . The inventions can be used in many kinds of industry, including but not limited to the food industry, to analyze crushed stone, gravel, and rubble, and in any production where the distribution of the individual objects and/or particles matter.

For example in sugar production, the distribution of grain size is an important parameter in the production, but also for many of the industries using sugar in their products, grain size distribution is important. As an example, the dissolution rate is dependent on the grain size, and therefore the grain size is often checked by the end user. This includes cake manufacturers, candy manufacturers, soft drink manufacturers etc. Checking is often performed by taking samples, either random or at intervals, from production, which samples will be analyzed using instruments that are designed to measure the grain size distribution .

Manual methods, based on a system of stacked sieves in which the sieves have a decreasing mesh size, exist. The particle size distribution can be determined by weighing the residuals on each sieve. In the sugar industry, they call this method the ICUMSA method.

There also exist computer-based analysis methods, where the material samples are attempted separated and images taken of the particles in free fall. From the images, the particle size and distribution is calculated using image analysis .

In known solutions of measuring devices, that are using feeding chutes for dispensing particles, it is the shape and. vibration frequency of the chute that determine how much the particles will be sepa ated before they reach the edge of the feeding chute. This kind of separation of the particles is difficult if not impossible to control. This is particularly difficult for small particles wherein the dispersion of the particle size is relatively large, and in case the particles tends to aggregate. In an attempt to control the amount of particles that is conveyed forward in the feeding chute, solutions for existing systems are available, where the feed hopper neck is positioned close to the bottom of the chute, in order to restrict the layer thickness on the feeding chute. Another solution uses an additional vibrator on the oscillating chute that applies vibrations at a perpendicular angle with respect to the feed direction.

From International patent application no. WO 02/44692 is known an apparatus for carrying out the analysis of the colori etry, as well as of the size and the purity of ground product s .

It is a main aspect of the present invention to provide a measuring device of the kind mentioned in the opening paragraph for determining at least the size, shape and/or color of the particles or objects in a sample.

In a further aspect is provided a method for determining at least the size, shape and/or color of the particles or objects in a sample.

The novel and unique whereby these and other aspects are achieved according to the present invention consist in that the measuring device comprises that

each feeding chute has a means for generating vibrations at controlled frequency,

a first set of a first camera unit and a first light source arranged below the first feeding chute,

a second set of a second camera unit and a second light source arranged below the second feeding chute, wherein

both the first set of a first camera unit and a first light source light and the second set of a second camera unit and a second light source is placed so that the particles fall freely through the optical path between a camera unit and a light source of a respective set, and - the means for generating vibrations at controlled frequency and the camera units are connected to a computer unit .

In order for the analysis of the sample to be accurate, it is important that the particles do not overlap while they fall through the area in which the images are generated. In the case of overlapping particles, the image analysis of the in the known computer-based methods will treat the overlapping particles as a single particle, and thus the calculated particle distribution will become incorrect.

In products, such as sugar, there is a tendency for the grains to stick together or to get attached to the surfaces they are in contact with, both of which cause inaccuracies in the known computer-based methods of analysis, since the size distribution is based on the result of the image analysis .

The measuring device of the present invention has a built- in system for the separation of particles so that e.g. the particle size, color and/or shape can be measured with high precision.

The measuring device has a first feeding chute and a consecutive second feeding chute, however a plurality of consecutive feeding chutes equipped as the preceding feeding chutes with means to control the vibration frequency of the feeding chute, light sources and camera units are foreseen within the scope of the present invention. In the subsequent description the term the last feeding chute is used to illustrate that more than two consecutive feeding chutes can be implemented in the present invention. The last feeding chute may be the second consecutive feeding chutes in embodiments limited to two feeding chutes.

The measuring device for the measuring of particles or other objects in a sample, which is in accordance with the invention for the analysis of particles, is generally intended for determining at least the size distribution of particles or objects in a bulk material sample.

To that aspect the measuring device has two built-in feeding chutes. Attached to each feeding chute is a vibrator. The vibrating frequency of each vibrator is controlled so the vibration intensity varies, so that the the particles or objects are conveyed at different conveying speeds and rates from the charging end, which may be closed, to the open end of the feeding chute. The feeding chutes are positioned so that the second feeding chute is receiving the particles from the first feeding chute .

Under the first feeding chute, a light source and a camera unit, which measures the particle density, is installed. Under the second and any consecutive feeding chute, a light source and a camera unit, which measures the size of the particles as well as the particle density, is installed. The camera units installed at the free end of a respective feeding chute wherefrom the particle and/or objects fall are connected to a computer unit that performs the analysis of the signals from the camera units.

Using e.g. two consecutive feeding chutes, makes it possible to feed the particles from the first feeding chute to the second chute such that the particles, during transport on the second chute, are separated before they fall off the edge of the second feeding chute. Thus, it will be possible to achieve good accuracy in the result from the analysis which calculates the particle distribution. In addition to this, the measuring device, with two feeding chutes provided with means for generating vibrations at controlled frequency, enables a high level of reproducibility .

With a color camera under the feeding chute, it is also possible to measure the color of the particles or objects, which is sometimes a parameter that the producer and the end user will want to know about. It may for example be important to end users of sugar, as sugar among others used for soft drinks, must have a well-defined color or should not be colored.

Each feeding chute is fixed to a means for generating vibrations at controlled frequency, thus "a frequency controlled vibration generator", and the vibrating frequency on each feeding chute is controlled by the results from the computer image analysis done by the computer unit. The vibration speed of the first chute is controlled by the analysis that calculates the particle density on the way to the final chute in the sequence of consecutive feeding chutes. In the event that the density is greater than desired, the vibration speed is reduced and vice versa if the particle density is less than desired. The last chute generally has a high feed rate compared to the rate of advance on the first chute, and in this way the particles are separated before they reach the open end of the last feeding chute. In addition to measuring the particle size, the particle density of the particles, falling down from the open end of the last feeding chute, can also be analyzed. Here the occurrence of overlapping particles is analyzed. Should there be any occurrences of overlapping particles, the vibration speed of the last chute is reduced until the particle density reaches the desired level, after which in turn the vibration speed is increased to a reasonable level until the desired high vibration speed is reached. If it turns out that it is not possible to achieve the desired high vibration speed, where particles separate sufficiently, the desired particle density from the first feeding chute is adjusted down so that the desired speed of advancement on the last feeding chute is obtained.

As the first feeding chute is being emptied, there will be fewer and fewer particles coming to the last feeding chute and the particle density, which is detected by the camera unit system, is getting smaller and smaller. The computer unit receives signals accordingly and the means for generating vibrations at controlled frequency gradually increases the vibration frequency until it finally ends at the maximum frequency. When the vibration speed of the feeding chute is at maximum, the last particles, which may stick to the surface, detach. After a predetermined time, when no further particles exit the open edge of the last feeding chute, both vibration generators are stopped and the computer unit calculates the particle distribution and possibly the color and any other measured parameter of the sample.

The two feeding chutes of the measuring instrument may be placed in a horizontal plane at an arbitrary angle relative to each other, and the first open end of the first feeding chute provides material for the subsequent consecution feeding chute, such as the second feeding chute. The slope of the feeding chutes in the described measuring device can be positive, zero or negative with respect to a horizontal plane .

The design of the feeding chutes may include one or more design options such as e.g. that

- in addition to having a closed end and an open end the feeding chute may have sides to confine the sample to the feeding chute, and/or

- one or both of the first feeding chute and the consecutive second feeding chute may also have a concave, a convex or a flat bottom, and/or

- the feeding chutes can have different shapes.

In all configurations of the measuring device, there may be one or more computer units that analyze the data from the camera units for the analysis of the sample of particles or objects, and to control the vibration frequency of the feeding chutes.

In measuring devices which, in addition to the size and shape of the particles or objects in a sample, also measure the color, at least one color camera is installed below one of the feeding chutes.

The invention further relates to a method of analyzing particles using the measuring device described above, wherein a sample of particles or objects is transported in at least two consecutive feeding chutes by means of means for generating vibrations at controlled frequency in such a way that the particles or objects on the last feeding chute are separated before they fall freely through the optical path after said last feeding chute.

The flow of particles that fall out over an open edge of the first feeding chute is controlled by the signals from the first camera unit under the first feeding chute and a feedback of the signals from the second and any subsequent camera unit under the second and subsequent feeding chute, respectively, is send to the computer unit to control that any excessive particle density falling through the optical path at the open edge of the second and consecutive feeding chute result in a reduction in the flow of particles from the first or other preceding feeding chute, as well as in a temporary reduction in the conveyance of particles on the second and consecutive feeding chute.

Preferably the speed of the means for generating vibrations on the feeding chutes is/are controlled continuously to increase control of separation of the particles in a samp1e .

The speed of the means for generating vibrations may be set at full speed and controlled by time when the sample is terminated to empty the feeding chutes fully of particles and objects included in the sample being analuzed.

Other advantages and features of this invention will be described in more detail in the following with reference to the accompanying drawing, wherein Fig. 1 is a schematic side view of a measuring device for the analysis of e.g. particles in accordance with the invention, and

Fig. 2 shows schematically a top view of two consecutive feeding chutes.

With reference to Fig. 1 and 2 the design of the measuring device for analyzing particles is described, in accordance with the invention, as follows.

The camera-based measuring device, as schematically illustrated from a side view in Fig. 1, is used to analyze particles 2 and in particular small and very small particles of bulk goods such as sugar, coffee and the like. Some individual particles 18 and 23 are shown in Fig. 1.

The particle distribution in the two chutes is schematically shown in Fig. 2, and the first feeding chute 1, which is the first of two chutes 1,17 in the configuration of the measuring device, is formed with a closed end 4 and an open end 5, in which the particles are then routed such that the particles 6 in free fall are fed to the second and last feeding chute 17.

In Fig. 1, the first feeding chute 1 is shown with a positive angle 20 with respect to the horizontal plane so that it decreases from the closed end 4 to the open end 5. With this configuration, gravity will assist the particles 2 in moving towards the open end 5, but in other configurations, the angle 20 can be 0 (horizontal), or negative with an inclination from the closed end 4 to the open end 5.

The first feeding chute 1 is by means of a mechanical connection 3 coupled to a first vibration generator 19 that controls its vibration frequency. For the further detailed description a means for generating vibrations at controlled frequency means is for the sake of simplicity also named "frequency controlled vibration generator". The function of the first frequency controlled vibration generator 19 is to facilitate forward movement of the particles 2 on the first feeding chute 1, and by increasing or decreasing the frequency of vibrations by means of the first vibration generator 19, the rate of movement of the particles 2 is controlled according to the particle density observed by camera unit 7.

In Fig. 1, the first feeding chute 17 is shown with a positive angle 22 with respect to the horizontal plane so that it falls from the closed end 10 to the open end 16. With this configuration, gravity will assist the particles 18 in moving towards the open end 16, but in other configurations, the angle 22 is 0 (horizontal) or negative with an inclination from the closed end 10 to the open end 16.

The second and last feeding chute 17 is coupled to a second frequency controlled vibration generator 12 using a mechanical connection 11.

The function of the second frequency controlled vibration generator 12 is to create sufficient forward movement so that the particles 6, which are falling onto the second and last feeding chute 17, are advanced at a high speed towards the open end 16 of the second and last feeding chute 17. This causes the particles 18 to separate, as shown in Fig. 2, before they fall off the edge of the open end 16.

In order to carry out the measuring of the particle density and, optionally, color of the particles 6, there is a first light source 8 placed so that the particles 6 fall through the optical path 9 between the first camera unit 7 and the first light source 8 on the way down into the second and last feeding chute 17.

In order to carry out the measuring of particle size, shape, density, and optionally color, there is located a second light source 15 which illuminates towards the second camera unit 13 and the particles 18, which fall out of the open end 16 of the second and last chute 17, are passing through the optical path 14 between the second light source 15 and the second camera unit 13.

The camera units 7 and 13 and the vibration generators 19 and 12 are connected to a computer unit 21 which receives signals from the camera units 7 and 13. In the computer unit 21 the signals from the camera unit 7 are analyzed to determine the particle density and, optionally, color, while the signals from the second camera unit 13 are analyzed to determine the particle size, shape, density, and optionally color.

From the particle density analysis results of the particles 6, a signal is transmitted to the first vibratory generator controller 19 and the desired vibration frequency is set. In this way, the desired particle density is always achieved, and it is adjusted so that the particles 18 of the second and last feeding chute 17 are sufficiently separated before they fall off the edge of the open end 16 of the second and last feeding chute 17.

Basically, the vibration rate of the second frequency- controlled vibration generator 12 may be high, but it can be controlled by the computer unit 21. This is done in the event that the second camera unit 13 detects the large particle density of the particles 2 second and last feeding chute 17. In the case of a too high particle density of the particles 23 in the free fall through the open end 16 of the second and last feeding chute 17, the speed of the second vibration generator 12 is temporarily reduced until the particle density is normalized. Then the speed of the second vibration generator 12 is increased again to the desired high value.

If the particle density of the particles 6 on the first feeding chute 1, observed by the first camera unit 7, is too large, there is a risk that the separation of the particles in the subsequent chute 17 is not sufficient, and thus, there may be overlap of the particles 23, falling off the edge of the open end 16 of the second and last feeding chute 17. In this situation, the more particles could be seen as a particle too large, and the measuring of such overlapping particles will give the wrong result.

In the case of persistent overlapping particles 23, the measuring of the size distribution will be incorrect and the result of the analysis becomes worthless.

In the event that the second camera unit 13 measures a to high particle density of the particles 23 that fall off the edge at the second and last feeding chute 17, the signal is sent to the computer unit 21, which reduces the desired particle density of the particles 6, measured by the first camera unit 7, and thus transmits a signal to the first vibration generator 19 such that the conveying speed of the particles 2 is reduced. In this way, an optimal separation of the particles 23 within the particle analysis is achieved, while the analysis speed is kept at its optimal for the current sample.

When no more particles are exiting the open end 5 of first feeding chute 1, the frequency of the first vibration generator 19 is increased until the frequency is at the maximum, and in this way the first feeding chute 1 is empty for any possible small particles having been stuck on the surface. When the first feeding chute 1 and the second and last feeding chute 17 have been running the maximum for a predefined time, set in the computer unit 21, the device stops and the device is then ready for the next sample.

This method for emptying the device of particles means that it is only rarely necessary to carry out a manual cleaning of the respective feeding chutes 1 and 17.

In its entirety, the invention is a measuring device and/or instrument for measuring at least size, density, shape, and color, and combinations of these parameters of small particles, as well as of larger objects. The measuring device and the method of the invention provide analytical results of bulk goods (small and large particles) with specific parameters that are comparable to the recognized manual methods, for example ICUMSA sugar. This includes the particle size, particle shape, size distribution and color.

The measuring device for analysis of particles, such as sugar and coffee, consisting of two feeding chutes each attached to a frequency-controlled vibration generator, controlled by signals from camera units placed under each feeding chute. Under each feeding chute, there is a light source and a camera unit that is used to capture images of particles that fall from the feeding chutes. The signals from the camera units are received by a computer unit that analyzes them, and from the measured particle densities between the first and last feeding chute and after the last feeding chute, the flow rate in the two feeding runs is controlled. The flow rate in the last feeding chute is set high while the first feeding chute is controlled to achieve a constant flow of particles to the last feeding chute while the flow rate is adjusted by the separation of the particles as they leave the last feeding chute.