Device, carrying body and lifting vehicle

[0001] The present invention relates to a device comprising a support body for transferring a load, which carrier body contains space, inside which at least one force sensor is located between the first wall, which accepts the load and the other wall opposite with the force sensor partly protruding beyond the edge of the other wall, and containing a transmission gear, to the force sensor force resulting from the load on the first wall, with this, that the force transmission includes at least partially bendable force transmission body, which extends from the side of the force sensor facing the first wall, through a recess in the force sensor and to the opposite side of the force sensor, and is attached at least near the opposite side of the force sensor.

[0002] A known example of such a device are the weighing forks of a lifting vehicle, such as for example a forklift or pallet truck, the weighing forks usually comprising, as a carrying body, two lifting teeth in which four force sensors are normally located referred to as transducers. The transducers include a pressure sensor or strain gauge, for example, in the form of a so-called secondary transducer, such as a resistance strain gauge, which is able to determine the mechanical deformation of the transducer and generate it in the form of an electronic signal. In the known device, the transducers lie in the space between the top wall of the lifting forks on which the load is received and the bottom wall of the lifting forks on which the transducers are placed. Because some of the transducers extend beyond the edge of the bottom wall, the transducers are prone to bending under pressure. The force resulting from the pressure exerted on the forks, for example, by the load placed on the weighing forks, is transmitted directly through the top wall to the transducers, which results in the mechanical deformation of these transducers. The deformation measurement is determined by a sensor and sent as an electronic signal to a processing device designed for this purpose. The force exerted on the lifting forks can be calculated from the electronic signal, and based on the combined result of the four force sensors, the total weight of the load on the lifting forks can be obtained by means of a processing device.

[0003] Although it is possible, using a known device, to measure forces for deriving, for example, the weight of the load obtained on the device, the known device has the disadvantage, however, that the measured values ​​are not optimally accurate in all conditions. The exact result of the measurement will be achieved with the use of force sensors only in the case of loading in the direction to which the force sensor is tuned, such as in the case of a known lifting device in the exactly vertical direction.

However, the moment of loading the load on the support body results in a mechanical play of forces in this support body, whereby certain parts in the support body will be stretched, or on the contrary, will be compressed to the extent that depends on the combination of weight and load placement. The force exerted on the force sensors, as a result of the load, therefore in practice contains many components such as, for example, torque and torque, which are the result of centrifugal loading of the support body in which the force sensor is built.

To transfer the force that is exerted by the load on the support body to the force sensor, German Patent Application DE 196 32 161 discloses a transfer body between the support body and the force sensor. Said known transfer body consists of a compensating body between the upper surface of the force sensor and the first wall of the support body that receives the load.

[0004] German patent application DE 40 29 925 discloses a device of the type described at the outset which uses a bendable element in the transfer body to compensate for non-vertical moments of force on the force sensor. This known transfer body includes a diabolo-shaped body that extends from the first wall of the support body through a recess in the force sensor to about half the height of the force sensor, where it is attached to the force sensor with a screw. The diabolo-shaped body has a tapered portion that allows it to bend. However, due to its shape, with the tapered portion constituting only a smaller part of the total height of the body, such a diabolo-shaped body is susceptible to bending only in one direction at a time. In addition, the bending range in the body is limited to a certain height of the tapered part. In order to improve the transmission of force between the carrying body and the force sensor, and thus increase the mounting accuracy, the present invention aims, inter alia, at providing a device that removes the above disadvantages in a practical manner.

[0005] In order to achieve the stated objective, a device of the type identified at the outset has the feature of the invention that that said force transmitting body is an elongated shaft, and the housing of the force-transmitting body within the cavity allows the force-transmitting body to bend within that cavity, and that the force transmitting body is coupled to the force sensor near the second wall by using fastening means, wherein the securing means in particular comprise a securing nut. The force exerted on the first wall, for example, the pressure force resulting from the load placed on it, will be transferred via the force transfer body to the opposite side of the force sensor to which the force transfer body is attached. By using here at least partially bendable force-transmitting body located inside the cavity to allow bending of the force-transmitting body, moments of forces exerted on the force-transmitting body, in contrast to the exactly vertical moment of force, lead to bending of the force-transmitting body.

[0006] Therefore, the force-transmitting body loads the force sensor almost exclusively in an exactly vertical direction, even in the case of centrifugal loading of the support body. The accuracy of the force sensor measurement result becomes practically independent of the load being placed on the support body. Since, in addition, the force transmission body extends here through the recess of the force sensor, and is therefore largely embedded in this recess, the overall dimension of the force sensor with the force transfer body does not increase at all or increases very slightly. Therefore, the device can take on such a compact form as known devices, which is of great importance for many applications, such as, for example, in portable industrial weighing devices. Because the force-transferring body is placed in a protected manner, built into the recess, the device is additionally sufficiently strong and durable to meet the quality standards applicable in various fields of use. This makes the device suitable for use in the most arduous working environments.

[0007] A preferred embodiment of the device according to the present invention has the feature that the force sensor comprises a transducer provided with a pressure sensor, i.e. a deformation sensitive sensor. The pressure sensor, i.e. a sensor sensitive to deformation, for example, in the form of a so-called secondary transducer, such as, for example, a strain gauge, is capable of and is adapted to determine the mechanical deformation of the transducer resulting from the moment of loading the load taken on the carrier body in the consequences of lifting and / or moving the load, and for generating it as an electronic signal. Then the charging moment can be obtained from the electronic signal by means of a processing device suitable for this purpose.

[0008] In a further preferred embodiment, the device according to the present invention is characterized in that the force transmitting body inside the cavity of the force sensor comprises a bendable part with a rim smaller than the cross section of the cavity. It is therefore positioned exactly around the bendable portion in such a way that the force transfer body has sufficient freedom of movement to convert any loading moments in a direction other than the optimal direction for bending the force transfer body such that the force sensor is only loaded in the direction whose force sensor is tuned.

[0009] A particular embodiment of the device according to the present invention has the feature that the force transmitting body comprises an external screw thread for a screw connection with a complementary internal screw thread within the cavity of the force sensor. Therefore, a reliable coupling between the force sensor and the force transmitting body can easily be made, with the forces acting on the force transmitting body being generated to the force sensor.

[0010] In a further preferred embodiment, the device according to the present invention is characterized in that the force transmitting body inside the cavity of the force sensor comprises a laterally extending edge between the outer surface of the force sensor and the first wall. Direct contact between the force sensor and the first wall is avoided by inserting an edge. For this reason, the mechanical deformation of the force sensor is only the result of the force acting through the force transfer body, making the measurement results extremely reliable.

[0011] In a further preferred embodiment, the device according to the present invention is characterized in that the force transmitting body inside the cavity of the force sensor is attached by means of a first outer end directly to the first wall. The attachment of the force transmitting body to the first wall prevents undesirable detachment of the force transmitting body from the first wall, thereby exerting an improper load on the force sensor.

[0012] In a further preferred embodiment, the device according to the present invention is characterized in that the force transmitting body inside the cavity of the force sensor extends completely through the force sensor from the first wall and is connected at least near the second wall to the force sensor. Therefore, the force transfer body can be reliably coupled to the force sensor in a simple manner. According to the present invention, the force transmitting body is coupled to a force sensor near the second wall by means of fastening means. In its particular embodiment, the device of the present invention is characterized in that the fastening means comprise a fastening nut. The use of separate fastening means, in particular the fastening nut, makes it possible to make the force transmitting body itself in a relatively simple way as an elongated mandrel that can be carried by the recess of the force sensor. Thus, the cost of producing the power transmission body is saved.

[0013] The present invention also relates to a support body for use in the device according to the invention.

[0014] The device of the present invention is widely used in all kinds of measuring systems in which forces resulting from transported, transferred or lifted loads are measured. The device is particularly suitable here as a lifting device for the lifting vehicle for the purpose of measuring and determining the forces of the load transported in the lifting vehicle. Therefore, the present invention relates in particular to a lift vehicle comprising the device according to the invention.

[0015] For an accurate determination of the weight of the load, the lifting vehicle according to the present invention is characterized in a preferred embodiment in that the device comprises at least one lifting forks in which a force sensor with a force transmitting body according to the invention is positioned at their both outer ends. The invention will now be further explained on the basis of an exemplary embodiment and the attached drawing. In the drawing:

Fig. 1 is a detailed view of the force sensor and the body transmitting the device of the invention;

Fig. 2 shows a side view of a longitudinal section of the device according to the invention.

[0016] The figures of the drawings are purely schematic and are not to scale. For the sake of clarity, some dimensions in particular may be exaggerated to a greater or lesser extent. Corresponding parts are marked in the figures as far as possible with the same reference numbers.

[0017] As shown in Fig. 1 in detailed view, and in Fig. 2 in a side view of the longitudinal section, the device 1 comprises a support body with a first wall 3 for receiving load, and with a second wall 2. The first and second walls leave a free space in which the force sensor 4 is placed. In this exemplary embodiment, the force sensor 4 is a transducer provided with a strain gauge having the ability to determine the deformation of the transducer and to generate it as a signal. The transducer part 4 is attached to the second wall 2. However, another part of the transducer 4 extends beyond the edge of the second wall 2 and therefore can bend freely in the event of vertical pressure from above, for example, resulting from placing the load on the first wall 3. The transducer 4 lies clearly at the first wall 3 with the force transmitting body 5 inserted. To this end, the force-transmitting body 5 comprises at its outer end a laterally protruding edge between the transducer 4 and the first wall 3. The force transmitting body 5 extends through a recess in another part of the transducer and is engaged on the opposite side of this transducer near the second wall 2 with respect to the transducer 4 by means of fastening means 7. Part of the force-transmitting body 5 inside the cavity has a thin rim and takes on a flexible form, whereby the force-transmitting body 5 is able and is adapted to bend when it is subjected to a moment of force that is not exactly vertical. The force transfer body 5 thus performs a force transfer that loads the transducer only in the direction to which the transducer is adapted, in this exemplary embodiment, in the vertical direction. This results in a very reliable and accurate measurement result of the sensor used in the transducer, the correction being carried out for the most part for centrifugal placing of the load on the support body. As shown in Fig. 2, the device 1 in this exemplary embodiment are lifting forks that, for example, can be used in a lifting vehicle such as, for example, a forklift or (hand) pallet truck. The lifting forks contain two lifting teeth that form a support body on which load can be received. Two force sensors are located in each fork lifting tooth 10 near the outer ends of the underlying portion of the lifting tooth of these forks. The effect of the load force placed on the fork lifting tooth can be obtained very accurately from the measurement values ​​of four force sensors taken together. The weight of the load can, for example, be calculated, or it is also possible to check whether the moment of loading the load on the device exceeds the set threshold value, so that a warning about this action, e.g. an alarm signal, can be generated on time.

[0018] Although the invention is further elucidated with reference to only a few exemplary embodiments, it will be obvious that the invention is not limited in any way to them. On the contrary, many other variations and embodiments are possible within the scope of this invention, as defined in the appended claims, for a person skilled in the art.