Forklift truck with lifting height measuring system

Abstract

Industrial truck with a lifting frame (10) and a load handling device (11) arranged vertically on the lifting frame (10) and a lifting height measuring system which has at least one sensor (2) for signal detection of a target mark (4) which moves vertically in the same direction as the load handling device (11), characterized in that the sensor (2) is housed in a sensor housing (1) which, in the measuring state, has a housing window (3) which is permeable to the signal of the sensor (2) in the direction of the target mark (4) and which, in the rest state, can be covered by means of a cover device (6) which moves vertically in the same direction as the vertical movement of the load handling device (11).

Description

[0001] The invention relates to a forklift truck with a lifting frame and a load handling device arranged vertically on the lifting frame, as well as a lifting height measuring system for the lifting height of the load handling device, which has at least one sensor for detecting a target mark that moves vertically in the same direction as the load handling device.

[0002] Various lifting height measurement systems are used for industrial trucks with a lifting frame, such as a mast, on which a load-handling attachment, most commonly a load fork, is guided for vertically moving loads. These systems detect the lifting and the lifting height of the load-handling attachment. For example, cable-pull sensors are used to measure the length of cable unwound from a pulley when the load-handling attachment is lifted. Other systems use a cable that is stretched vertically and looped around a measuring pulley. When the load-handling attachment is lifted, this measuring pulley is moved upwards and set into rotation by the cable wrapping. By recording this rotational movement, the height of the load-handling attachment can be determined.

[0003] The problem with these solutions is that the ropes used often break, as they are subject to mechanical wear and tear and material fatigue from alternating stresses. Furthermore, the ropes can snag on objects such as shelves or loads. Malfunctions can also occur if these systems are used outdoors and ice forms at low temperatures.

[0004] According to the current state of the art, optical sensors, such as laser distance sensors or those using an LED as a power source, are known to perform absolute height measurements and, due to their small size, can be easily integrated into a lifting frame. However, when using a laser distance sensor as a lifting height measurement system, contamination of the laser optics, a receiving sensor, or a reflective target can lead to system failure. A similar issue arises with optical lifting height sensors using an LED as a power source, where contamination of the LED, its optics, a receiving sensor, or a reflective target can also cause system failure. This is particularly true when the forklift is used outdoors (outdoors). Low temperatures (e.g.,Ice can form (in winter or when used in cold storage facilities). If ice forms over the lens, this can lead to unwanted scattering effects and, depending on the thickness of the ice, even to an interruption of the light beam.

[0005] From EP 2 562 128 A1, a forklift truck with lift height measurement is known in which the problem of contamination of optical measuring elements is solved by a nanocoating on a surface on or in front of the optics. In particular, a nanocoating with a lotus effect is used. On a nanocoated surface, dirt particles, but also ice, cannot form a firm bond with the surface. Vibration and shocks during operation of the forklift truck can dislodge ice and dirt particles. However, this does not prevent contamination of the optical measuring elements under all operating conditions. For example, if the forklift truck remains inactive for an extended period in a dirty environment, the optical measuring elements may still be dirty when the forklift truck is put back into operation.Only after prolonged operation do the dirt particles become loose again through vibration and shocks.

[0006] From EP 2 135 837 B1, a forklift truck with an optical lifting height measurement is known, which has an optical sensor that detects markings.

[0007] EP 2 924 389 B1 and US 2013 / 0 182 237 A1 each disclose a generic industrial truck with the features of the preamble of claim 1.

[0008] DE 10 2011 009 368 A1 discloses a forklift truck with a rope length encoder as a lifting height measuring system of a load handling device.

[0009] The present invention is based on the objective of providing a forklift truck with a lifting height measuring system that avoids the aforementioned disadvantages and is insensitive to contamination and ice formation.

[0010] This problem is solved according to the invention by housing the sensor in a sensor housing which, in the measuring state, has a housing window permeable to the signal of the sensor in the direction of the target mark, which can be covered in the rest state by means of a cover device which moves in the same direction as the height movement of the load-bearing device.

[0011] The invention is based on the consideration that, in a stroke height measuring system with a sensor and a height-adjustable target, at least contamination of the sensor can be reliably prevented if the sensor is covered by a covering device, i.e., a cover, when at rest and thus when not in use. The sensor is a signal receiver that receives the signals emanating from or reflected by the target. The signals can be, for example, optical, acoustic, or electromagnetic in nature. Examples include camera systems, laser scanners, LEDs, radar systems, and ultrasonic systems. In order for the sensor, housed within the sensor casing, to receive these signals, a signal-permeable window is provided in the sensor casing. In the simplest case, this can be an opening in the casing through which signals can pass.Especially in the case of an optical sensor, the housing window can be designed as a light-transmitting window, e.g. made of glass.

[0012] The resting state is preferably a state in which the load-bearing device and thus the target mark are completely lowered.

[0013] The sensor is preferably designed as an optical sensor. The measuring principle of such optical stroke height measuring systems is based on the fact that the stroke height-dependent distance of an optical path between the target and the sensor changes. For example, in a distance measurement, the extent to which a measuring path between the target and the sensor changes depending on the stroke height is recorded. For this purpose, the optical sensor is preferably designed as a laser sensor, in particular a laser scanner, or as an LED sensor. Alternatively, the change in the optical path can also be determined using other methods, such as changes in captured image patterns. For this purpose, the optical sensor is preferably designed as a camera, in particular a stereo camera.

[0014] Advantageously, the target is designed as a reflector. This allows a signal sent to the target to be reflected and detected by the sensor. Furthermore, the sensor housing preferably includes at least one additional signal transmitter that can send a signal through the housing window in the direction of the target. The sensor can be a camera, and the signal transmitter can be an illumination device for the target detected by the camera. The signal transmitter can also be a laser or an LED lamp. A laser scanner is particularly preferred, in which the sensor and signal transmitter form a single, highly compact unit. This also allows for a shared housing window for transmitting the signal and receiving the reflected signal.

[0015] In a particularly advantageous embodiment of the invention, the sensor housing is arranged in the lower region of the lifting frame and the housing window is directed vertically upwards, while the target mark is arranged vertically movable on the lifting frame above the housing and the cover device is arranged on the target mark, whereby the housing window can be covered by means of the cover device by lowering the target mark. The target mark, and thus the cover device, can be arranged on a part of the lifting frame that moves relative to the sensor housing during a lifting movement or on the load-handling device.

[0016] The target marker, located at the top of the vertical measuring section, is oriented with its reflective surface facing downwards and is therefore generally not subject to heavy soiling or ice formation. It may thus suffice to protect the sensor, located in the lower section and facing upwards, and, if applicable, the signal transmitter also housed within the sensor casing, from contamination. This is achieved by lowering the cover device located on the target marker onto the casing window. In this way, during the majority of the forklift's operating phases, when the load-handling attachment is in a rest or transport position and, in particular, when the load-handling attachment is fully lowered, the housing window of the sensor casing is automatically covered by the cover device, which is lowered along with the load-handling attachment, thus protecting the sensor and, if applicable, the signal transmitter from contamination and external influences.

[0017] In a particularly preferred embodiment, the target mark and the covering device are designed such that when the target mark and the covering device are lowered onto the housing window, at least the side of the target mark facing the sensor is also covered and thus also protected from contamination and external influences.

[0018] Preferably, the sensor housing and the cover device are designed in such a way that, in the resting state, they seal off the sensor and the target marker from the outside environment.

[0019] In an advantageous embodiment of the invention, this is achieved by the sensor housing having a bellows in the area of ​​the housing window, onto which the cover rests in the resting state.

[0020] Alternatively, according to a further embodiment of the invention, the sensor housing can have surface elements in the area of ​​the housing window into which the cover device engages in the rest state with surface elements parallel to these in the manner of a labyrinth seal.

[0021] The invention is suitable in principle for all types of industrial trucks in which a lifting height measuring system is installed to detect the lifting height of a load-handling attachment. In particular, the invention is suitable for forklift trucks or reach trucks with a lifting mast in which the lifting height of the load-handling attachment is measured.

[0022] The invention provides a reliable way to protect a lifting height measuring system, in particular an optical lifting height measuring system with a sensor and a target marker designed as a reflector, of industrial trucks from contamination and external influences, especially mechanical stress from foreign objects. In its resting state, a dense, sealed, protective environment is created for the sensor and the target marker.

[0023] Further advantages and details of the invention are explained in more detail with reference to the exemplary embodiments shown in the schematic figures. Here, Fig. 1 a stroke height measuring system according to a first embodiment of the invention with sensor housing and target mark in the measuring state, Fig. 2 a lifting height measuring system of the Fig. 1 with sensor housing and target marker in standby mode, Fig. 3 a stroke height measuring system according to a second embodiment of the invention with bellows on the sensor housing in the measuring state, Fig. 4 a lifting height measuring system of the Fig. 3 with bellows on the sensor housing in standby mode, Fig. 5 a lifting height measuring system of the Fig. 3 and Fig. 4 with bellows on the sensor housing in standby mode in a perspective view and Fig. 6 a lifting height measuring system of the Fig. 5 in another perspective view.

[0024] In the Fig. Figure 1 shows a first embodiment of the invention with a lifting height measuring system for a forklift truck with a sensor housing 1, for example, fixed in the lower area on the lifting frame.

[0025] A sensor 2, designed as an optical sensor 2a, is housed in the sensor housing 1. The sensor housing 1 is open vertically upwards. This opening forms a housing window 3, allowing the sensor 2 to receive signals from the target mark 4 unimpeded during measurement. The target mark 4 is housed in a cover 6, which is attached to a height-adjustable part of the lifting frame that moves with the vertical movement of a load-handling device of the lifting frame. The target mark 4 is preferably arranged on the load-handling device, for example, a lifting carriage mounted vertically on the lifting frame.

[0026] The distance between sensor 2 and target mark 4 can be determined via signal analysis. From this, the lifting height of the load-handling device can be deduced.

[0027] A cover device 6, in which the target mark 4 is arranged, has surface elements 7a designed as side parts which move parallel to corresponding surface elements 5a of the sensor housing 1 at a small distance when the cover device 6 is lowered onto the sensor housing 1.

[0028] The Fig. Figure 2 shows the lifting height measuring system. Fig. 1 in the resting state. The cover device 6 was lowered onto the sensor housing 1 as a result of the lowering of the load-bearing device. The surface elements 7a of the cover device 6, which is designed as a closing cover, engage with the corresponding surface elements 5a of the sensor housing 1 and form a type of labyrinth seal. In the resting state, sensor 2 and target marker 4 are thus hermetically sealed from the environment and protected against environmental influences and external mechanical influences.

[0029] In the Fig. 3, Fig. 4, Fig. 5 to Fig. Figure 6 shows a second embodiment of the invention with a lifting height measuring system for a forklift truck, comprising, for example, a sensor housing 1 that is fixedly attached to the lower part of the lifting frame 10. With the Fig. 1 and Fig. Two identical components are provided with the same reference numerals. Sensor 2, designed as an optical sensor 2a, is housed in sensor housing 1 and is located in the Fig. 3, Fig. 4, Fig. 5 to Fig. 6 is not shown in more detail.

[0030] In the embodiment of the Fig. 3, Fig. 4, Fig. 5 to Fig. 6 the sensor housing 1 has a flexible bellows 5b attached in the area of ​​the housing window 3.

[0031] The Fig. Figure 3 shows the measurement state in which the target mark 4, located in the cover device 6, is at a distance from the sensor housing 1. The sensor 2, preferably an optical sensor 2a, housed in the sensor housing 1, can receive the signals from the target mark 4 (reflector) unimpeded through the housing window 3 and the bellows 5b. The target mark 4 is attached to a height-adjustable part of the lifting frame 10, which moves with the vertical movement of the load-handling device 11. For this purpose, the target mark 4 is preferably arranged on the load-handling device 11, for example, a lifting carriage arranged height-adjustably on the lifting frame 10.

[0032] The distance between sensor 2 and target mark 4 can be determined via signal analysis. From this, the lifting height of the load-handling device can be deduced.

[0033] The Fig. Figure 4 shows the lifting height measuring system from the Fig. 3 in the resting state, in which the cover device 6 with the target mark 4 is lowered onto the bellows 5b of the sensor housing 1. The cover device 6 has surface elements 7b designed as side parts which rest on the bellows 5b in the resting state. In the resting state, the bellows 5b and the cover device 6, which rests on the bellows 5b and thus closes the sensor housing 1, hermetically seal both the sensor 2 and the target mark 4 from the environment and protect them against contamination and external mechanical influences.

[0034] In the Fig. 5 and Fig. Figure 6 shows that the cover device 6 is attached to the load-bearing device 11, for example a lifting carriage, of the lifting frame 10 by means of a holder 12.

[0035] The sensor housing 1 of the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. 6 is preferably designed as an enclosure that is decoupled from the sensor 2 and within which the sensor 2 is arranged. The sensor 2, which is arranged within the sensor housing 1 designed as an enclosure and is attached to the lifting frame 10, can thus be protected by a [missing information - likely a specific component or element] in the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. The 6th adjustment device, not shown in detail, is precisely adjusted to the target mark 4.

[0036] The invention makes it possible to protect a lifting height measuring system of a forklift truck with an optical sensor 2a and a target marker 4 designed as a reflector from contamination and external influences. The sensor 2a and the reflector surface of the reflector can be optimally protected from external influences during the operation of the forklift truck. As shown in the Fig. 1 and Fig.As can be seen in Figure 3, when the forklift truck is in operation and the lifting height measuring system is in its measuring state, the reflector (target mark 4) located in the cover device 6 and the sensor 2 located in the sensor housing 1 are protected from external influences. When at rest with the load-handling device lowered, a dense, sealed, protective environment is created for the sensor 2 and the target mark 4, so that the sensor 2 and the target mark 4 are hermetically sealed from the environment and protected against contamination and external mechanical influences.

[0037] The invention protects the lifting height measuring system of the industrial truck from contamination and mechanical stresses caused by foreign objects, so that the industrial truck equipped with the lifting height measuring system can be used in all operating environments.

[0038] The sensor housing 1 and the cover device 6 form a protective system separate from the sensor 2, which protects against external influences of the environmental conditions and thus enables a high availability of the stroke height measuring system designed as an optical stroke height measuring system.

Claims

[1] Industrial truck with a lifting frame (10) and a load handling device (11) arranged vertically on the lifting frame (10) and a lifting height measuring system which has at least one sensor (2) for signal detection of a target mark (4) which moves vertically in the same direction as the load handling device (11), characterized by , that the sensor (2) is housed in a sensor housing (1) which, in the measuring state, has a housing window (3) permeable to the signal of the sensor (2) in the direction of the target mark (4), which in the rest state can be covered by means of a cover device (6) which moves in the same direction as the height movement of the load handling device (11). [2] Industrial truck according to claim 1, characterized by , that the sensor (2) is designed as an optical sensor (2a). [3] Industrial truck according to claim 1 or 2, characterized by , that the target mark (4) is designed as a reflector. [4] Industrial truck according to any one of claims 1 to 3, characterized by , that the sensor housing (1) additionally contains at least one signal transmitter which can send a signal through the housing window (3) in the direction of the target mark (4). [5] Industrial truck according to any one of claims 1 to 4, characterized by , that the sensor housing (1) is arranged in the lower area of ​​the lifting frame (10) and the housing window (3) is directed upwards, while the target mark (4) is arranged vertically on the lifting frame (10) above the sensor housing (1) and the cover device (6) is arranged on the target mark (4), wherein the housing window (3) can be covered by means of the cover device (6) by lowering the target mark (4). [6] Industrial truck according to any one of claims 1 to 5, characterized by , that the sensor housing (1) and the cover device (6) are designed such that, in the rest state, they seal off the sensor (2) and the target mark (4) from the outside. [7] Industrial truck according to any one of claims 1 to 6, characterized by , that the sensor housing (1) has a bellows (5b) in the area of ​​the housing window (3) on which the cover device (6) rests in the rest state. [8] Industrial truck according to any one of claims 1 to 6, characterized by , that the sensor housing (1) has surface elements (5a) in the area of ​​the housing window (3) into which the cover device (6) engages in the rest state with parallel surface elements (7a) in the manner of a labyrinth seal.

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