Method and system for verification of a measurement device of material transfer means

Technical Field

The invention relates to a method and a system for verification of a measurement device of material transfer means. The invention can be preferably applied to weighing devices, which are used for weighing of e.g. loose, grain, longitudinal, piece, or liquid material in e.g. loading or transportation equipment.

Background technology

Material transfer means, such as wheel loaders, excavators or forklifts often include a weighing device for weighing material to be transferred. The weighing in- formation is used for e.g. determining the amount of the material being transferred for debiting the material. Scales can also be used for other purposes, such as for facilitating the loading of a suitable amount of material with the material transfer means to a truck in order to avoid overloading or transporting incomplete loads.

Figure 1 illustrates as an example one material transfer means according to the prior art, a wheel loader 10. The wheel loader has a bucket 12 as a carrying means for the material to be transferred. The bucket is connected to the body parts of the wheel loader with an articulated beam 13. In order to lift/lower the bucket, hydraulic cylinders 14 are connected to the beam, which cylinders are controlled with valves of a hydraulic system. Additionally, the wheel loader has hy- draulic cylinders 15 for turning the bucket.

The purpose of the weighing device of the wheel loader is to weigh the weight of the material which is currently placed in the bucket. The weighing device may function in such a way, for example, that pressure sensors are installed in the lifting cylinders 14, which pressure sensors measure the pressure of the liquid in the cylinder. Additionally there may also be other sensors in the system or the weighing can be made with strain gauge transducers. The information received from the sensors is processed on the basis of e.g. measurement parameters, and a weighing result is achieved as a result of the processing. The user interface 18 of the weighing device is usually placed in the cabin of the wheel loader.

When a weighing device is used as a basis of debiting, verification must be periodically performed for it. It is ensured by the verification that the weighing result does not deviate from the real weight of the object more than what is allowed. The largest allowed deviation as well as the verification procedure is usually deter- mined by the authorities.

The verification is commonly performed by using precision weights, in which the weight is very accurately set into a predetermined even reading. The verification can be performed by weighing with the scales of the material transfer means various amounts of precision weights, the weight of which is within the operating range of the scales. The precision weight is placed on the material transfer means and it is weighed with the scales of the material transfer means. The weighing result of the scales is compared to the weight of the known weight/weights which have been placed to the material transfer means. It is also possible that the verification procedure includes several weighings of a same precision weight, weigh- ings during movement of the material transfer means and/or weighings in different positions of the carrying means, and during movement and pauses between the movements of the carrying means. The purpose of several weighings is also to check the repeatability of the weighing results of the weighing device.

Some disadvantages are related to the prior known verification solution. Material transfer means, such as forklifts or wheel loaders are usually used in industrial, warehouse, construction site or port areas, wherein there are no precision weights that are needed for the verification. On the other hand, in the verification of large material transfer means particularly large precision weights may be needed, such as 25.000 kg. Considerable costs are related to providing such precision weights. Additionally, room and suitable environmental conditions are required in order to store large precision weights in an appropriate manner. It is also inconvenient to transfer large precision weights in connection with the verification.

One solution could be transportation of precision weights to the premises of the material transfer means for the verification. However, transportation of large and heavy weights to the verification premises and transferring them at the verification premises is inconvenient as well.

The holder of the present patent application has also made a finding according to which the weight distribution of the material used in the weighing may affect the weighing result. If the verification is performed with e.g. precision weights with a form of cylinder, sheet or cube, a weighing accuracy according to the verification is

achieved when pieces of the same form are weighed, which pieces have been placed to the material transfer means in the same way as in connection with the verification. It is, however, common that a weighing device is used for weighing of other types of materials, such as loose material, grain, longitudinal, piece or liquid material. Since the distribution of the weight in the material transfer means is then different, the accuracy of the weighing results may be worse than the accuracy which is has been achieved in the verification.

Summary of the invention

The purpose of the present invention is to avoid or reduce the disadvantages of the prior art which were described above.

The object of the invention is achieved with a solution, wherein instead of precision weights, material is used in the verification which is weighed with both the weighing device of the material transfer means and with a reference scales. The material sets are transferred between the material transfer means and the refer- ence scales by means of the material transfer means and/or the reference scales. The weighing results of the weighing device and the reference scales are compared with each other in order to evaluate the accuracy of the weighing device. If the deviation exceeds a predetermined limit the weighing device is not considered to fulfil the accuracy requirement in question. In one embodiment of the invention the verification is performed by weighing with a weighing device and a reference scales same type of material which is weighed with the weighing device in its ordinary use. The material may preferably be loose, grain, longitudinal, piece or liquid material.

In one embodiment of the invention the material transfer means is a wheel loader, whereby the weighing device measures the weight of the material which material is on the bucket of the wheel loader.

In one embodiment the functionality of the reference scales is checked by means of a weight, such as a precision weight, e.g. in the connection of the verification of weighing devices, or prior to the verification. The reference scales may be verified to be e.g. 3-10 times more accurate then the weighing device to be verified. The accuracy, uncertainty and/or repeatability may also be verified before it is used for verification. The authorities determine the properties of the reference scales and/or they are determined by the purpose of use of the weighing device.

According to one embodiment the reference scales comrises a weighing platform, which has walls. According to one embodiment at least one wall can be opened in order to remove/transfer material from the weighing platform.

According to one embodiment the reference scales comprises a space which is limited from sides and bottom, and a removal opening at the bottom for removing weighed material from the reference scales. A reference scales of one embodiment comprises a conveyor for removing the weighed material from the reference scales. According to one embodiment the material is weighed with a reference scales when the material is on the material transfer means. In this case the material transfer means is weighed with the reference scales also without the material in order to determine the weight of the material transfer means so that the measurement value of the material weight is achieved by means of the weighings. The reference scales is in this case preferably e.g. a weight bridge, on which the material transfer means is driven for the weighings.

According to one embodiment the reference scales is verified before the reference scales is used for verification of another weighing device. The reference scales is verified by means of precision weights, for example. Method according to the invention for verifying a weighing device of material transfer means, Wherein said weighing device is meant for weighing material which is transferred with the material transfer means, is characterized in that the verification has at least the following phases:

- a first set of material to be weighed is placed to the material transfer means, - the first set of material is weighed with the weighing device of the material transfer means,

- the first set of material is transferred to a reference scales,

- the first set of material is weighed with a reference scales,

- the weighing results of the first material set obtained with the reference scales and the weighing device of the material transfer means are compared, whereby in the method the first material set is transferred to the reference scales and/or from the reference scales to the material transfer means, and

said transfer of the first material set to the material transfer means and/or away from the material transfer means is performed by means of the material transfer means or the reference scales.

A system according to the invention for verification of a weighing device of material transfer means, is characterized in that

- the system has reference scales for the comparison of the weighing results of the weighing device and the reference scales,

- the material transfer means and/or the reference scales comprises means for transferring a first material set between the material transfer means and the reference scales or from/to the reference scales,

- the weighing device comprises means for weighing the first material set and for forming a first weighing result, and

- the reference scales comprises means for weighing the first material set and for forming a second weighing result for comparison to said first weighing result.

Some preferable embodiments of the invention are described in the dependent claims.

Significant advantages can be achieved with the invention when compared to the known solutions. When using the solution according to the invention it is not necessary to transport large amounts of precision weights to the verification premises, whereby a material transfer means meant for transporting heavy loads is not needed for performing the verification. Instead, the reference scales and the small weigh possibly required for checking its functionality can be easily transported with a small truck. The reference scales may also be made to be assembled at the verification premises, whereby it can be transported as parts or folded even with a passenger car, estate car or a cross-country vehicle, for example.

When using a solution according to the invention a crane is not either needed for transferring precision weights to the material transfer means or out from the material transfer means. The transfer of the material to be weighed to the material transfer means and out from it can be performed with the material transfer means itself /and/or with the reference scales. In this context a platform tilting the the reference scales, such as the tail lift of a truck can be considered to be included in the reference scales.

In the solution according to the invention the verification of the weighing device can be made by using same kind of material as which is handled with the material transfer means in its ordinary use. The material to be weighed may thus be e.g. loose material, grain, longitudinal, piece or liquid material. The weight of the differ- ent types of materials is distributed on the carrying means in different ways, which also affects the weighing result. Ordinary precision weights differ essentially in their weight distribution from said loose, grain, longitudinal and liquid materials, for which reason the a more accurate verification is achieved with a solution according to the invention, in which the type of the load to be weighed corresponds to the ordinary use of the material transfer means.

It is also possible to make the verification process and tuning according to the invention in part or wholly automatic so that information on the objects to be measured or the information on the highest allowed deviation need not be processed manually during the performance of the verification. This is possible because information on the available precision weights is not needed. In the verification action, the weighing device or the reference scales can give an instruction for the user about how much material to be weighed is to be handled, and the results can be transferred between the devices automatically through wireless and/or wired connections. This way the weighing device can also compare automatically the weighing results in order to determine the deviation and possibly to compare the deviation values to the highest allowed values. By means of the data transfer it is also possible to monitor the verification process from a distant point. Also the tuning which is performed before or in connection with the verification can be auto- matic or it can be performed from the distant location.

Short description of the drawings

In the following part the preferable exemplary embodiments of the invention are described in more detail by referring to the enclosed drawings, in which:

Figure 1 illustrates a wheel loader according to prior art; Figure 2 illustrates a flow diagram of one method according to the invention for verification of a weighing device;

Figure 3 illustrates a flow diagram of another embodiment of a method according to the invention for verification of a weighing device;

Figure 4A illustrates one arrangement according to the invention, in which the reference scales has been installed on a platform of a truck;

Figure 4B illustrates an enlarged view of the reference scales of Figure 4A;

Figure 5 illustrates one reference scales according to the invention, which has an inclined, silo-like weighing container; and

Figure 6 illustrates one system according to the invention for verification of a weighing device..

Detailed description of the invention Figure 2 illustrates one method according to the invention for verification of a weighing device 20. First in phase 21 it is checked that the carrying means of the material transfer means is empty, and the weighing device of the material transfer means and the reference scales are adjusted to zero. One can also check the operation of the reference scales by e.g. using a small precision weight. The size of the precision weight may be e.g. only 10% of the maximum weight of the operating range of the reference scales.

After zeroing, preferably zero checking is performed, phase 21b. This can be done e.g. in the case of a wheel loader in such a way that an empty bucket is lifted and lowered e.g. 5 times and it is checked that the weighing result remains zero within the predetermined accuracy after each moving of the bucket. During the zero checking the weighing device is preferably set to an accuracy step which is one accuracy step smaller than the accuracy step under normal use so that the stability of zero is more accurately detected.

In phase 22 a first weighing set of material is placed on the material transfer means, which first weighing set corresponds in its weight to the smallest verification weight to be used. The material can be set to the material transfer means in the same way in which material is set to the material transfer means in its common use. Thus, material can be set e.g. to the bucket of a wheel loader by filling the bucket from a material heap, such as a gravel heap, by controlling the wheel loader and the bucket. The weight of the bucket is monitored with a weighing device included in the material transfer device, and amount of material is set to the material transfer means, which amount is close to the smallest required verification weight. It is preferable to use same kind of a measurement object such as

material in the verification as what is used in the common use of the measurement device. This way e.g. the weight distribution corresponds to the weight distribution appearing in a real use, and the verification situation corresponds very closely to the real situation of use. When a suitable amount of material has been achieved, the material is weighed with a weighing device of the material transfer means, phase 23, and the weighing result is recorded or stored. After this, in phase 24, the material located at the material transfer means is transferred to the reference scales so that the carrying means becomes empty. The emptying of the material transfer means can be checked with the weighing device, which should give zero as a weighing value after the emptying. After the material has been transferred to the reference scales it is weighed with the reference scales, phase 25. After the weighing, the reference scales can be emptied. It is also possible to weigh several material sets without emptying the reference scales between the weighings, whereby the reference scales is preferably zeroed/tared before weighing of each material set. If the reference scales is installed on a platform of a truck the reference scales can be emptied by tipping the platform of the truck into an inclined position whereby the material on the reference scales slides out of its weighing level. If the weighing level has walls, it is preferable that one wall can be opened when the platform is tilted for the removal of the material. Alternatively, the weighing level of the reference scales can be continuously inclined and provided with a controllable removal opening at the lowest position of the weighing level, whereby the material can be removed from the weighing level by opening the removal opening. In case of material pieces the pieces can be removed with the material transfer means.

Although it is preferable to transfer only the material to be weighed onto the reference scales, it is also possible to weigh the material with the reference scales when the material is in the material transfer means. In this case, the reference scales is preferably e.g. weigh bridge on which the material transfer means is driven. The material transfer means is weighed both with the material and without the material, whereby it is possible to achieve the weight of the material as subtraction of the weighing results. The reference scales can be zeroed/tared when the material transfer means is on the reference scales without material, whereby the weight of the material is achieved directly from the reference scales when the material transfer means is on the reference scales with the material. However, it must be noted that when the material is weighed by means of e.g. weigh bridge when the material is on the material transfer means, it is more difficult to achieve

as good measurement accuracy as by weighing only the material with reference scales, which is dimensioned for weighing only material.

Next it is estimated/checked in phase 26, whether the verification requires more weighings of material sets. Often the verification is made with many different weights and/or loads. The amount of weighings and the verification weights to be used are commonly determined by the authorities. In the present embodiment, the weight of each material set can deviate within certain limits because the verification is not based on the accuracy of the weight to be weighed. Therefore, the weights of the material sets can vary more from the standard values, preferably significantly more, than e.g. the accuracy which is required from the measurement device.

If more weighings are needed, next material set is placed to the carrying means of the material transfer means in phase 26a e.g. in the same way as the previous material set. After this, phases 23-25 are performed again. Material sets of deter- mined quantities are weighed in a required amount according to the verification regulations.

After weighing all material sets, it is preferable to perform zero checking, phase 26b. If desired, the zero checking can be performed also after weighing of each material set before setting the next material set to the material transfer means in phase 26a.

The weighing results given by the weighing device and the reference scales from each material set are compared to each other in the distant point in phase 27 in order to determine deviation between the weighing results of the weighing device and the reference scales. The value of the deviation is further compared to the maximum allowed value of deviation. If the value of the deviation is smaller than the highest allowed deviation, the weighing device fulfils the regulation in this respect. If the value of the deviation is higher than the highest allowed deviation the weighing device does not fulfil the verification regulations. The comparison can be made according to Figure 2 after all material sets have been weighed. Alterna- tively the comparison can be made after weighing of each material set.

When the weighings and result comparisons of the material sets have been performed, the verification is finalized, phase 29. If the verification of the weighing device is rejected, it is possible that tuning of the weighing device is performed.

When the weighing device has been tuned it may be possible to perform the verification again or to perform review weighings.

The weighing device may also be tuned before the verification. Also in this case the tuning can be performed by means of reference scales by using one or several material sets which are weighed with the weighing device and the reference scales according to phases 21-26. However, if the deviation value achieved in verification is higher than the predetermined maximum value of deviation, the tuning of the weighing device may be performed on the basis of the weighing and comparison results which have been achieved in the verification. In the tuning the weighing parameters of the weighing device are corrected in such a way that the weighing results which would be achieved from the weighing device with the corrected parameters would be as close as possible to the weighing results given by the reference scales. This tuning may also take place automatically, if the weighing device has a calculation program of tuning parameters, whereby the weighing results given by the reference scales are input to the weighing device. It is also possible that there is a data transfer connection between the weighing device and the reference scales, whereby the weighing results of the reference scales can be transferred electrically from the reference scales to the weighing device for the tuning. It is also possible that the verification process is monitored from the distant point, which may locate at any distance from the verification location. In this case the weighing results given by the weighing device and the reference scales can be transferred to the distant point. The weighing results can be transferred directly through electrical interfaces formed to the weighing device and the reference scales. Alternatively, it is possible to transfer the weighing data as image data, whereby the displays of the weighing device and the reference scales are imaged with e.g. mobile station, web camera or a video camera, and the image data is transferred to the distant point. In this case it is possible to transfer image information the distant point also about the performance of the verification process, such as the transfer of the material sets. In the distant point, the maximum allowed deviation can preferably be stored and the weighing results of the weighing device and the reference scales can be compared with the maximum allowed value of the deviation. Additionally, it is possible that tuning of the measurement device is performed from the distant point by controlling the weighing device from the distant point by means of data transfer. Common data transfer connections, such as wired and wireless data transfer networks and connections, can be used for data

transfer. As one possibility, the data can also be stored and checked afterwards. A certificate on the verification can be made in the local point or distant point, or the certificate can be transferred from the distant point to the local point. The certificate can also be stored to the verified measurement device for possible later need.

It should be noted that the verification method can also include repetitions of weighing performed by the weighing device. For example, the verification of the weighing device of a wheel loader may require several weighings of the same precision weight, weighings during the movement of the material transfer means, and/or weighings in different positions of the carrying means and during movement and pauses between the movements of the carrying means. The purpose of several weighings is also to check the repeatability of the weighing results of the weighing device.

The solution according to the invention also applies to situations where a material transfer means is used with several different carrying means, such as buckets, pegs or grabs. Each carrying means is then examined in the verification. Individual tuning values for each carrying means can be stored in the memory of the weighing device. Tuning values of each carrying means are selected at the scales by selecting the tuning values of the tool being used manually or by providing the weighing device and the tool of the material transfer means with automatic recognition, such as bar code or RFID identifier. The identification of the tool can also be manual, whereby the tool has e.g. a number identifying the tool, which number is input to the weighing device, after which the weighing device takes the correct tuning parameters into use. Figure 3 illustrates another embodiment 30 according to the present invention. In this embodiment material used in the verification is placed to the reference scales, phase 31. The material can be placed to the reference scales with e.g. material transfer means, the weighing device of which is meant to be verified. Alternatively, the material can be transferred to the reference scales with some other transfer means. It is preferable to transfer to the reference scales so much material that it is sufficient for several material sets to be used in the verification. Before the verification weighings it is checked that the carrying means of the material transfer means is empty, and the weighing device and the reference scales are preferably adjusted to zero, phase 32. After zeroing, preferably zero checking is preferably performed, phase 32b. This can be done e.g. in the case of a wheel loader in such

a way that an empty bucket is lifted and dropped for e.g. 5 times and it is checked that the weighing result remains zero after each moving of the bucket.

Next the first material set to be used, weighed, is transferred from the reference scales to the material transfer means, phase 33. In the transfer, the material set can be removed from the reference scales by using similar removing manners as were described above in connection with the description of Figure 2. In the method according to Figure 3 the material set to be removed from the reference scales is, however, dropped to the carrying means of the material transfer means.

After transferring the first material set it is weighed with the reference scales, how much the weight of the material on the reference scales changed due to the removal of the first material set, phase 34. This change of weight is the reference weight of the first material set to be used in the verification. If the reference scales is zeroed/tared before the removal of the first material set, the weight of the first material set is achieved after the removal of the first material set directly as an ab- solute value of the weighing result of the reference scales. If zeroing/taring has not been performed, the reference weight of the first material set is achieved by subtracting the weighing result which is achieved after the removal of the first material set from the weighing result which is achieved before the removal of the first material set. In phase 35 the first material set is weighed with the weighing device of the material transfer means to which the first material set was transferred from the reference scales. Next it is evaluated/checked in phase 36, whether the verification requires more weighings. If further weighings are required, the next material set is placed from the reference scales to the carrying means of the material transfer means in phase 36a e.g. in the same manner as the previous material set. If the the verification weight which is used in the verification is larger than the first verification weight, the first material set can be left to the carrying means of the material transfer means and an additional set of material with a size of the difference between the first second verification weight. This way the second material set has a size of the first material set and the additional material set. After the transfer of material phases 34-35 are performed again. A required amount of material sets of determined sizes are weighted according to the verification regulations.

When all material sets have been weighed, zero checking of the weighing device is preferably performed, phase 36b. When all material sets have been weighed with rising and/or descending weight, the weighing results from each material set

are compared to each other in phase 37 in order to determine the deviation between the weighing results of the weighing device and the reference scales. The value of the deviation is further compared with the highest allowed value of the deviation. If the value of the deviation is smaller than the highest allowed devia- tion, the weighing device fulfils the regulation in this respect. If the value of the deviation is higher than the highest allowed deviation the weighing device does not fulfil the verification regulations. A certificate on the verification can be made, which certificate can also be stored to the verified measurement device for possible later need. The comparison can be made according to Figure3 after all material sets have been weighed. Alternatively the comparison can be made after weighing of each material set before weighing the next material set.

If the deviation is higher than the predetermined maximum value of the deviation, the weighing device may be tuned. When the weighing device has been tuned, verification weighings or checking weighings may possibly be performed. After the weighings of the material sets and the comparisons of the results have been performed, the verification is finished, phase 39.

The embodiment according to Figure 3 can also be applied in such the material transfer means is weighed with the reference scales with and without the material instead of weighing the material alone. On the basis of these weighings the weight of the material is achieved. First a larger set of material can be taken to the material transfer means, and after weighing it, some material can be removed from the material transfer means and weighing of a new, smaller material set can be performed. Thus material sets of different sizes are weighed by removing aprt of the material between the weighings.

Also in the embodiment illustrated by Figure 3 it is possible to transfer weighing results electrically between the weighing device and the reference scales by e.g. using data transfer connection, whereby the verification process can be automatized. The weighing results of the reference scales can be transferred to to the weighing device, in which they can be used for comparing weighing results in order to determine deviation. Further, it is possible to store the highest allowed value of the deviation in the weighing device, into which value the measured deviation can be compared. If the weighing device has been programmed to control the verification process the weighing device can transfer electrically information to the

reference scales on which size of material set is to be transferred from the reference scales to the weighing device.

In the embodiment according to Figure 3 It is also possible to transfer information to a distant point from the weighing device and the reference scales, whereby it is possible to monitor the verification process from a distance. The weighing results can be transferred directly from the weighing device and the reference scales, or the concerned devices and the verification process may be imaged with e.g. mobile station, web camera or a video camera, whereby this image data can be transferred to the distant point. It is also possible to arrange the tuning of the weighing device from the distant point by controlling by means of electrical data transfer. The verification incident can also be recorded and checked afterwards. Through recording, the monitoring person of the verification can monitor the verification independently of time and place via e.g. the Internet. A patent number FM 13982 has been granted for the applicant, in which patent the material to be weighed is imaged together with the weighing incident, whereby the parties can confirm the weighed materials and rights. The same basic procedure can be applied for imaging the verification.

In this case it is possible to transfer image information the distant point also about the performance of the verification process, such as the transfer of the material sets. In the distant point, the maximum allowed deviation can preferably be stored and the weighing results of the weighing device and the reference scales can be compared with the maximum allowed value of the deviation. Additionally, it is possible that tuning of the measurement device is performed from the distant point by controlling the weighing device from the distant point by means of data transfer. Common data transfer connections, such as wired and wireless data transfer networks and connections, can be used for data transfer. As one possibility, the data can also be stored and checked afterwards. A certificate on the verification can be made in the local point or distant point, or the certificate can be transferred from the distant point to the local point. The certificate can also be stored to the verified measurement device for possible later need.

Figure 4A illustrates reference scales, which is installed on the platform of a truck and which can be used in connection with the method and the system according to the invention. Figure 4B illustrates an enlarged view of the reference scales. The reference scales 40 has a weighing base 42, which has walls for preventing the material from flowing away. The weighing base has been supported via weighing sensors 48 to the truck platform which serves as an installation platform. Thus

the weighing sensors output a signal, which is proportional to the total weight of the weighing base and the material on the weighing base. The signals of the weighing sensors are led to the measuring unit of the reference scales (not shown in Figures 4A, 4B), which forms the weighing result on the basis of the sensor sig- nals. It is possible to improve the accuracy of the reference scales, installed on the vehicle platform, with e.g. attitude or acceleration sensors, with which the horizontal attitude of the scales can be checked, or deviation from the horizontal attitude can be compensated. Additionally, a correction of the local g value, i.e. the acceleration of gravity, can be made for the reference scales according to patent Fl 118276.

One wall 43 of the weighing base can be opened for removal of material. The wall 43 is articulated 44 to the rest of the weighing base, whereby it can be turned open. The weighed material can be removed from the weighing base by lifting pieces away or by tilting the truck platform into an inclined attitude and opening the wall 43 of the weighing base. Thus the material on the weighing base slides away from the base 42. It is naturally possible to turn the weighing base into an inclined attitude also in other ways except installing the reference scales on the truck platform. The reference scales can be installed, for example, on feet against the ground whereby the reference scales may include a motorized tilting mechanism. Further, it is possible to form the base of the reference scales of a conveyor belt, whereby the material can be transferred away from the weighing platform by starting the conveyor belt. It is also possible to perform the emptying of the weighing base by transferring a horizontal sheet along and across the surface of the weighing base. In the above described solutions the reference scales is installed on the platform 49 preferably in such a way that the material can fall freely away from the weighing base 42 when the material is removed.

It should be noted that the reference scales can be a separate device, which is possible to be transferred from a truck to another, ori t can be integrated to the structure of a truck, for example. Figure 5 illustrates another reference scales 50 according to the invention. The reference scales has a silo-like container 52 for the material to be weighed. At the bottom of the container, at the lowest location of the container, there is an opening, 53 which has a movable shutter. When the material to be weighed is placed to the container of the reference scales, the shutter is in a closed position, whereby the material remains in the container. The reference scales is supported to its platform with feet 57, and in the scales illustrated in the Figure the weighing

sensors are placed between the feet and the platform. This way the weights of both the reference scale structure and the material to be weighed are directed to the weighing sensors. The scales is zeroed/tared before the weighing in order to remove the own weight of the scales structure from the weighing result. After the weighing the shutter can be opened, whereby the material flows down to the removal tube/removal spout 54 and away from the reference scales.

It must be noted that by means of the reference scales it is possible to weigh the whole weight of the material which is placed on the reference scales or alternatively the weight of the added or removed part of the material. It is possible, for example, that when material sets of different sizes are transferred to the reference scales, the material sets are not removed from the reference scales between the reference weighings. Thus the weight of each material set can be determined by weighing with the reference scales the material weight before the transfer of the concerned material set to the reference scales, and after transferring the transfer to the reference scales, and by forming the difference of said weighing results. Alternatively the reference scales can be zeroed before the transfer of each material set to the reference scales, whereby the weight of each material set is achieved directly as weighing results of the reference scales.

Further, it is possible to use the reference scales in such a way that first a larger amount of material is transferred on the reference scales, which amount of material is enough for several weighings. The transfer of material to the reference scales can be performed with the same material transfer means, for which the verification is performed, or alternatively with some other material transfer means. The weight of the material transferred to the reference scales is weighed or the refer- ence scales is zeroed. After this a material set to be weighed in the verification is transferred to the material transfer means, the weighing device of which is to be verified. The transfer can be performed by releasing material through a removal opening and tube to the carrying means of the material transfer means, such as a bucket. The bucket of the material transfer means can be placed below the end of the removal tube for the transfer of the material. By controlling the shutter and by monitoring the weighing value given by the reference scales it is possible transfer fairly accurately a desired amount of material to the material transfer means. After this the material set is weighed with a weighing device of the material transfer means. This way it is possible to transfer subsequently several material sets, and between the transfers weighing is performed with the weighing device of the material transfer means, and possibly a weighed material set is removed from the ma-

terial transfer means before transferring the next material set to the material transfer means. If the carrying means of the material transfer means is emptied between the weighings of successive material sets the material can be emptied back to the reference scales.

It is possible to transport the reference scales illustrated by Figure 5 as such with e.g. a truck or a van. However, the reference scales may include removable parts, such as feet or a removal tube. Also the walls of the material container may be partly or totally removable, or foldable. In this case it is possible to transport the reference scales also with smaller vehicles, such as in the trunk of a passenger car or an estate car.

Figure 6 illustrates a system according to the invention for the verification of a weighing device of material transfer means. In the system illustrated in Figure 6, the material transfer means is a wheel loader 10, which has a weighing device 60. The weighing device measures weight of the material placed in the bucket of the wheel loader by means of one or several sensors 61. The sensors comprise e.g. a pressure sensor which is installed in the lifting cylinder of the bucket and a movement and/or an acceleration sensor installed in the lifting shaft. A measurement unit 62 of the weighing device receives the signals achieved from the sensors and calculates the weighing result. The weighing result is shown to the user on a user interface 63, which includes a display, for example. The user interface has preferably also input means, such as a keyboard, by means of which the functions of the weighing device can be controlled. By means of input means the weighing device can e.g. be set into weighing mode, verification mode or tuning mode, and weighing results and tuning data achieved in the verification can be input to the weighing device.

A reference scales 40 has been installed on a platform of a truck 47. The reference scales is thus tiltable for removing weighed material. One or several weighing sensors 71 are related to the electric part 70 of the reference scales, which sensors can be e.g. strain gauges or pressure sensors. The sensors have been placed e.g. between the weighing platform and the installation platform, or between the weighing platform and other structure of the reference scales. The measurement unit 72 of the reference scales receives signals achieved from the sensors and calculates the measurement result. The weighing result is shown to the user on the user interface 73, which includes e.g. a display. The user interface has preferably also input means, such as a keyboard, by means of which the functions of the reference scales device can be controlled.

As was mentioned above, the reference scales may also be a weigh bridge, on which the material transfer means can be driven to. In this case the material weight is measured by weighing the material transfer means with and without the material. The reference scales is also most preferably verified. The reference scales can be verified in connection with its manufacture or installation, and after specified time intervals. The verification of the reference scales can be performed with ways described above, or it can preferably also be performed by means of precision weights.

In connection with the verification, material sets are placed e.g. on and away from a bucket of a wheel loader. The corresponding material sets are transferred to and away from the reference scales. The material sets used in the verification are transferred by means of a wheel loader and/or a reference scales. This way separate transfer means are not needed for the transfer of the material sets to be weighed.

The tuning of the weighing device can be performed by comparing the weighing results given by the weighing device and the reference scales and by tuning the weighing device to give the same weighing results as the reference scales sufficiently accurately. "Sufficiently accurate" is in this case preferably in accordance with _r the official verification directives or better.

It is also possible that the weighing device and the reference scales have communication means, by which it is possible to transfer information between the devices. The communication can take place in wireless or wired manner by using short range data transfer or public data transfer systems, such as cellular network or Internet network or their combinations. In the system illustrated in Figure 6 the weighing device comprises data transfer means 65 and an antenna 66 for wireless data transfer. Also the reference scales includes the corresponding parts 75, 76. Thus the weighing device and the reference scales can transfer information related to the verification between the concerned devices. The information can be e.g. the size of the next material set required in the verification, the weighing result achieved with reference scales, the weighing result achieved with the weighing device, tuning parameters, etc. By means of the data transfer it is possible to make the verification procedure automatic so that the user need not input data concerning weighing sets and/or information relating to tuning and/or a check sum to the weighing device.

It is possible to arrange monitoring which takes place at a distant point 90, whereby the monitoring can be performed e.g. by an authority, by someone authorised by an authority or by an instance, which administers material transfer equipment or verification equipment. In this case there is equipment for data transfer and data processing, such as a personal computer 90, in the distant point. The data transfer can take place, for example, in a wireless manner via a cellular network or in a wired manner via the Internet network or as a combination of these.

In the distant point according to Figure 6 the distant point has personal work- station which is provided with wireless data transfer 96. The workstation of the distant point can transfer information with the weighing device and the reference scales, or the workstation can be connected to the Internet, through which the data travels. Thus the weighing results given by the weighing device and the reference scales can be acquired to the distant point. Additionally, it is possible that the verification procedure is also controlled from the distant point. Firmer, one possibility is to transfer image information from the verification premises to the distant point.

It is also possible that the data to be transferred from the local point to the distant point are stored before, during or after the transfer of the data. For this purpose the system may also have imaging means 81 and 83, which have means 82, 84 for wireless data transfer. These mobile stations, web cameras, video cameras or corresponding ones have been arranged to transmit to the distant point image information from the user interface of the weighing device and the reference scales, such as from the display and from the keyboard. This way it is possible to see at the distant point the shown weighing results and also the actions that are performed with the user interfaces of the weighing device and the reference scales. The system may further include a third camera 85, which is arranged to image the verification procedure at a wider area, whereby it is possible to monitor e.g. the transfers of material sets from the distant point. Also this third camera can be equipped with a wireless data transfer means, 86. It is also possible that the amendments of the tuning parameters are performed from the distant point before the verification, for example.

The invention has been described above with the reference to the enclosed embodiments. It is, however, clear that the invention is not restricted only to those,

but is comprises all embodiments which can be imagined within the inventive idea and the enclosed patent claims.

Although applying the invention in connection with a wheel loader is especially preferably, it is clear that the described embodiments can be applied in connection with verification of weighing devices of any loading etc. material transfer means, such as an excavator, a material machine, a forklift, a pallet truck, a crane, flat scales, a belt scales, a conveyor, a silo, a car, a train, a garbage truck, a timber truck, a harvester, a drive machine, a mini loader, a dumper, a reach truck, a tank truck, or other weighing devices. In a corresponding manner, the material to be weighed can be loose material, grain material, longitudinal material or liquid material. The carrying container of the material transfer means can be a container, platform or a gripper instead of a bucket.

In a corresponding manner the material to be weighed can be loose material, grain material, longitudinal material or liquid material. The carrying container of the material transfer means can be a container, platform or a gripper instead of a bucket.

Above, a weighing device of a wheel loader was described, in which a pressure sensor placed in a hydraulic cylinder was used for forming a signal which is proportional to the weight. It is naturally possible to use alternatively or additionally other types of sensors, such as a strain gauge which is connected to the beam. Further, weighing material which is located in e.g. liquid container can be based on either measuring the weight of the whole liquid container containing the material, or on measuring the pressure prevailing in the liquid container.

In the reference scales described above the sensors are located against the in- stallation platform of the reference scales, but the sensor of the reference scales may naturally locate in other place of the reference scales structure. The sensor may, for example, locate between the weighing container of the reference scales and other structure of the scales.

Above, some ways have been described for transferring weighed material away from the reference scales, such as tilting the reference scales and using an outlet tube. However, it is possible to imagine also several other ways, such as using various conveyors which belong to the reference scales, and using a pump when handling liquid materials.

Although the verification of the measurement device is mentioned to be preferably to fill the requirements of the authorities, it is naturally possible to use in the verification of the measurement device also a better limit of accuracy. Additionally, even if verification of a measurement device required by the authority has been described as the most preferable embodiment, the invention can naturally be used also in such applications, targets and environments, wherein the verification is not an action required by the authorities but is based on voluntariness, or other agreements.