Background to the invention

The invention relates to a method and measuring device for detecting binding wires.

Binding wires are used to bind various products, such as cellulose units or iron rods, which are moved from place to place with the aid of conveyors or lifted by the binding wires. Particularly when lifting heavy products, a sufficient number of binding wires is important to avoid dangerous situations, such as the breaking of the binding wires. Using various measuring devices, such as inductive sensors, it is at present possible to check that there are binding wires in a product. However, using these devices it is not possible to ensure that the number of binding wires is sufficient for safe lifting or transportation. It is only possible to check the number of binding wires by eye, but as this is done by a person it is too slow and is not suitable, for example, in a factory environment. The number of binding wires should be checked immediately the product is made and also before lifting, as errors can take place in binding, wires can break, or knots can open.

Brief description of the invention

The invention is therefore intended to develop a method and a measuring device for implementing the method, in such a way as to solve all the aforementioned problems. The aim of the invention is achieved by means of a method and device that are characterized by what is stated in the independent Claims. Preferred embodiments of the invention are the subjects of the dependent Claims.

The invention is based on placing a measuring device in the vicinity of the binding wires. A magnetic field is created by the measuring device and a value is measured relating to the change in the magnetic field caused by the binding wires, in order to obtain a measurement result.

The advantage of the method and device according to the invention is an increase in safety in the packaging, transportation, and lifting of products bound by binding wires. In various stages, it is easy to check the sufficiency of the binding wires in products and automatically stop the transportation or lifting if there are not sufficient binding wires. With the aid of the invention, the detecting of binding wires is also cost-effective, rapid, and easy. Brief description of the figures

The invention will now be described in greater detail in connection with preferred embodiments, referring to the accompanying drawings, in which:

Figure 1 shows a perspective view of one measuring device; Figure 2 shows one binding-wire detection method;

Figure 3 shows a front view of one measuring device; and

Figure 4 shows one measuring device seen at an angle from above.

Detailed description of the invention

Figure 1 shows an exploded view of one measuring device 1, by means of which binding wires can be detected. Figure 3 shows a front view of one measuring device and Figure 4 shows the measuring device 1 of Figure 3 seen at an angle from above. The measuring device 1 comprises a means, such as a coil 2, attached to a frame 4, for creating a magnetic field, and a shield plate 3. In addition, the measuring device 1 comprises an attachment component 6 attached to the cover 5 for attaching the measuring device in a desired location, such as a lifting device or a production line.

The coil 2 can have an air or ferrite core. A coil 2 with a ferrite core can be manufactured by winding a conductor around the ferrite core. Insulated copper wire, for example, can be used as the conductor, and a plate containing a ferromagnetic substance as the ferrite core. The ferrite core should be large enough for a bundle of binding wires to fit inside the magnetic field created around the coil. The binding wires to be measured are held at a sufficient distance from the coil 2, for example, by plastic insulation. Behind the coil 2 is a shield plate 3, for example, a ferrite plate, which acts as a conductor for the magnetic field. The shield plate 3 prevents iron structures above the coil 2 from interfering with the measurement. If the mechanics of the measuring device 1 are designed so that iron structures do not interfere with the measurement, the shield plate 3 can be omitted.

In addition, the measuring device 1 can comprise means for detecting a change in the magnetic field, when binding wires are brought into the vicinity of the magnetic field. The means for the detection of a change in the magnetic field can be a configuration, constructed from separate components, or a circuit, such as a microcircuit. In addition, the measuring device can comprise means for measuring the losses of the coil 2. The measuring device can also comprise a control unit, with which the measurement data can be processed. The data obtained from the control unit can be stored in the memory of the measuring device 1 or in a memory external to the measuring device 1. The measuring device 1 can also comprise at least one data-processing device connected to it operationally, for process the measurement results. Alternatively, the measuring device can also be connected to an external control unit, which can be located in an external data-processing device, in which the measurement data can be stored, and in which the measurement data obtained can be processed and forwarded. The external control unit can be, for example, a computer or the production- control system of an industrial plant.

In one embodiment, the measuring device 1 can be attached to, or integrated with any lifting device whatever. The lifting device can be a cellulose- unit lifting device, which is used for lifting cellulose units bound with binding wires. One or more grab elements of the lifting device can comprise a measuring device. Before lifting, the grab element is threaded under the binding wires and the measuring device 1 is placed near the binding wires, preferably on top. The grab element can bundle the binding wires into a bundle, so that the binding wires remain as well as possible in a specific place relative to the coil 2, which facilitates measuring and obtaining reliable measurement results. After this, a magnetic field is created with the aid of, for example, a magnetic-field creation means, such as a coil 2. The measuring device 1 can comprise, in addition, a device detecting a change in the magnetic field, with the aid of which a change in the magnetic field is detected. After this, the measuring device 1 can be arranged to measure one or more values relating to a change in the magnetic field, in order to obtain at least one measurement result. The binding wires are preferably made from metal, which permits the strength and electrical properties of the magnetic field to be utilized in the measurement.

The measurement of a change in the magnetic field can be based on the measurement of the amount of losses in the coil 2 in the measuring device 1, for example, using a coil-loss measuring device. The amount of the losses of the coil 2 can be obtained by measuring the magnitude of the power required to maintain constant-amplitude oscillation and/or by measuring the impedance of the coil 2. In the measurement of power, the coil 2 and the capacitor in the circuit board of the measuring device 1 can form a resonance circuit. The resonance frequency is preferably in the order of magnitude of 400kHz, but other frequencies can also be used. At least one measurement result measured with the aid of the measuring device 1 can be sent to the control unit or data-processing device, which compares the measurement result to at least one predefined threshold value stored in the memory. If the value of at least one measurement result is less than at least one predefined threshold value, an error is noted in the number of binding wires. Noting an error can trigger various operations in the measuring device, the production line, or the lifting device. If the product is being lifted, a warning light can come on in the measuring device 1, when the person operating the machine can stop the lifting. Another alternative is to automatically stop the lifting of the product when the error becomes apparent. In one embodiment, the measuring device 1 can be located on the production line and detect the binding wires at the end of the production process. An error found in the number of binding wires can cause an error code to be sent from the measuring device to the production control system, when production can be stopped automatically, a warning light can light up and/or the faulty product can be guided to the side of the production line. If an error is not found in the detection of the binding wires, a green light can light up in the measuring device 1, or some other indication of a sufficient number of binding wires can appear.

Before measurement is started, the measuring device 1 can be calibrated and one or more threshold values defined, with which the actual measurement results are compared. The defined threshold value can be stored in the measurement device's 1 own memory or in the memory of a data-processing device operationally connected to the measuring device 1. When defining the threshold value, at least one value relating to a change in the magnetic field caused by the binding wires is measured when the number of binding wires is as required. For example, when lifting cellulose units there can be eight binding wires and a safety factor of 4 can be used for the number of winding wires of the cellulose units. Then, according to the requirements, eight binding wires will carry a quadruple load relative to the dimensioning. When defining the threshold value, at least one value, relating to a change in the magnetic field, is measured for eight wires. The result obtained is used to define the threshold value. A value, by which the number of binding wires is still sufficient to ensure safe lifting, is selected as the threshold value. For example, there are normally eight binding wires, but lifting can still be safe even though there might be only four wires, i.e. a half fewer. The threshold value can then be defined, for example, as half of the value of the measurement result. Binding wires made from different materials or intended for different situations can have different safety factors. The change in the magnetic field is great when there are many wires, but diminishes when the number of wires is reduced. Thus the amount of the change in the magnetic field can be used to define the precise number of wires. The measuring device 1 can also comprise a display, which can show the number of wires obtained in the measurement, or other information relating to the measurement.

In one embodiment the lifting device comprises a measuring device according to the above description. The lifting device can be a cellulose-unit lifting device or some other lifting device suitable for lifting products.

Figure 2 shows one method for detecting binding wires with the aid of a measuring device 1. In the method, the measuring device 1 is placed 20 in the vicinity of the binding wires. The measuring device 1 is used to create 22 a magnetic field and to measure 24 at least one value relating to a change in the magnetic field caused by the binding wires, in order to obtain at least one measurement result.

A measuring device according to the above description can be used to detect binding wires in various connections, such as to detect binding wires on a production line after the packaging of the products or in a shop for checking products on sale. The safe lifting of products bound by binding wires can be ensured by locating the measuring devices in various hoists, when it is possible to ensure a sufficient number of binding wires prior to lifting.

It will be obvious to one skilled in the art that in the development of technology the basic idea of the invention can be implemented in many different ways. Thus the invention and its embodiments are restricted to the examples described above but can vary within the scope of the Claims.