HYDRAULIC CONTROL SYSTEM OF A LIFT DRIVE OF A LIFTING GEAR OF A FLOOR CONVEYOR AND FLOOR CONVEYOR

Description

[0001] The invention relates to a hydraulic control system of a lifting drive of a lifting frame of an industrial truck, wherein the control system has a control directional valve device which is connected to a delivery line of a hydraulic pump, to a container line leading to a container and to a connecting line leading to the lifting drive, wherein the control directional valve device is designed to control the lifting operation and the lowering operation of the lifting drive.

[0002] In such hydraulic control systems, the control directional valve device is designed to control the lifting and lowering operations of the lift drive of the industrial truck's mast. The lift drive consists of one or more hydraulic lifting cylinders that raise and lower a load-handling device, such as a load fork, mounted on the mast. A load on the load-handling device rests on the control directional valve device.

[0003] If, in such a hydraulic control system, a fault occurs in the control directional valve device during lowering operation while a load is being lowered, for example with a nominal load, the control directional valve device is suddenly actuated into a neutral position or a locked position, in which the connection between the lifting drive and the container is blocked. Such a fault in the control directional valve device can occur in a control directional valve device that is controlled and actuated electrically by means of an electrical actuating device, for example, in the event of a power failure of the electrical actuation signal of the actuating device and / or due to a plug break in an electrical cable that is connected to the electrical actuation device of the control directional valve device and carries the actuation signal of the actuating device. As a result of the sudden actuation of the control directional valve device into the neutral position orIn the event of such a fault in the control directional valve device, the load on the load-handling device is suddenly stopped, and depending on the previous lowering speed of the load-handling device and the weight of the load picked up by the load-handling device, a pulse is introduced into the mast via a pressure peak. A system according to the preamble of claim 1 is known from KR20140005285.

[0004] In conventional industrial trucks, the maximum lowering speed of the load handling device is generally <0.6 m / s. Due to changes in legal regulations, maximum lowering speeds of greater than 1 m / s, for example 1.2 m / s, are permitted and used in current industrial trucks.

[0005] In particular in the case of industrial trucks which have maximum lifting and / or lowering speeds of the load handling device in the range of greater than 1 m / s, for example 1.2 m / s, in the event of a fault of this type, for example a break in the plug of an electrical cable which is connected to the electrical actuation device of the control directional valve device and carries the control signal of the actuation device, a large impulse in the form of a pressure peak is introduced into the mast when the load handling device is lowered. For this reason, in the case of industrial trucks which have maximum lifting and / or lowering speeds of the load handling device in the range of greater than 1 m / s, for example 1.2 m / s, the maximum lowering or lowering speeds can generally be increased.In order to limit the lifting speed of the load-handling device to maximum lifting and / or lowering speeds of the load-handling device in the range greater than 1 m / s, for example, 1.2 m / s, the mechanical mast structure of the mast must be reinforced to prevent component failure of the mast in the event of the aforementioned failure. However, reinforcing the mechanical mast structure of the mast is disadvantageous because it is very costly.

[0006] The present invention is based on the object of providing a hydraulic control system and an industrial truck with a hydraulic control system that is improved with regard to the aforementioned disadvantage. This object is achieved according to the invention in that the control system has a pressure relief valve that is assigned to the connecting line, wherein the pressure relief valve is designed to limit a pressure peak introduced into the mast in the event of a fault in the control directional valve device.

[0007] A fault in the control directional valve device is particularly to be regarded as a fault in the control directional valve device in which the control directional valve device is suddenly actuated, i.e. within a short period of a few milliseconds, into a neutral or a locked position, in which the connection of the lifting drive to the container line or the conveyor line is blocked and thus the lifting or lowering movement of the lifting drive and thus of the load handling device is suddenly stopped. As a result of the sudden actuation of the control directional valve device into the neutral or locked position in such a fault in the control directional valve device, the load on the load handling device is suddenly stopped and, depending on the previous lowering speed of the load handling device and the weight of the load carried on the load handling device, a pulse in the form of a pressure peak is introduced into the mast.

[0008] A fault in the control directional valve device within the meaning of the application is therefore considered to be, in particular, a fault in the control directional valve device that leads to a sudden stop of the lifting or lowering movement of the lifting drive. This is also referred to below as a fault in the control directional valve device that leads to a digital lifting stop or digital lowering stop.

[0009] Such a fault in the control directional valve device, which leads to a digital lifting stop or a digital lowering stop, occurs in particular in the case of a control directional valve device that is controlled and actuated electrically by means of an electrical actuating device, for example in the event of a power failure of the electrical actuation signal of the actuating device and / or due to a plug break of an electrical cable that is connected to the electrical actuating device of the control directional valve device and carries the actuation signal of the actuating device.

[0010] According to the invention, a pressure relief valve associated with the connecting line is provided for such a fault scenario. This valve limits the impulse introduced into the mast by limiting the pressure peak. The use of the pressure relief valve according to the invention thus eliminates the need for complex reinforcement of the mechanical mast structure of the mast, thus preventing component failure of the mast in the aforementioned fault scenario.

[0011] According to an advantageous embodiment of the invention, the pressure relief valve is connected to the connecting line on the inlet side and to the container on the outlet side. Thus, when the pressure relief valve is opened, a connection between the connecting line and the container can be established, particularly to limit the pressure peak.

[0012] According to an advantageous embodiment of the invention, the pressure relief valve is designed, in particular, to limit the pressure peak introduced into the lifting frame in the event of a fault in the control directional valve device by connecting the connecting line to the container. To limit the pressure peak, the pressure relief valve opens and establishes a connection between the connecting line and the container.

[0013] According to an advantageous embodiment of the invention, the pressure relief valve, in particular, has a blocking position and an opening position, wherein the pressure relief valve is biased toward the blocking position by a spring device and toward the opening position by the pressure present in the connecting line. This achieves, in particular, that the pressure relief valve is actuated directly into the opening position by the pressure present in the connecting line, counter to the force of the spring device, in order to limit the pressure peak introduced into the mast.

[0014] According to an advantageous embodiment of the invention, the pressure relief valve is designed as a pressure relief valve. A pressure relief valve can be used to provide a pressure relief valve with minimal construction effort.

[0015] According to an advantageous embodiment of the invention, the pressure relief valve is designed as a control valve, in particular a two-position control valve. The control valve is designed, in particular, as a two-port, two-position valve. Such a control valve allows for a pressure relief valve to be provided with minimal construction effort.

[0016] According to an advantageous embodiment of the invention, the control valve is designed in particular as a switching valve or as a proportional valve throttling in intermediate positions.

[0017] Particularly preferably, the spring device can be set to an opening pressure of the pressure relief valve that is greater than the maximum system pressure of the lifting drive. Particularly preferably, the spring device can be set to an opening pressure of the pressure relief valve that is greater than 100%, 110%, or 120% of the maximum system pressure of the lifting drive.

[0018] According to an advantageous embodiment of the invention, the spring device, in particular, is set to an opening pressure of the pressure relief valve that is greater than 120% of the maximum system pressure of the lifting drive, preferably greater than 330 bar. With such an adjustment of the opening pressure of the pressure relief valve, the pressure relief valve is not used to protect the maximum system pressure of the lifting drive and thus does not respond during normal operation when raising and lowering the load-handling device. Instead, it responds only in the event of a fault in the control directional valve device and is actuated into the open position in order to limit the pressure peak introduced into the lifting frame.

[0019] According to an advantageous embodiment of the invention, the control system, in particular, comprises a pressure-limiting device connected to the feed line on the input side and designed to protect the maximum system pressure of the lifting drive. With such a pressure-limiting device connected to the feed line, the maximum system pressure of the lifting drive can be easily protected and limited.

[0020] According to an advantageous embodiment of the invention, in particular the control directional valve device is electrically operated.

[0021] According to an advantageous embodiment of the invention, the control directional valve device comprises, in particular, a control directional valve having a neutral position, a lowering position, and a lifting position. The control directional valve is actuated into the neutral position by a spring device, can be actuated toward the lowering position by means of a first electrical actuating device, in particular a magnet, and can be actuated toward the lifting position by means of a second electrical actuating device, in particular a magnet. With such a control directional valve, the lifting operation and the lowering operation of the lifting drive can be controlled with just a single control directional valve.

[0022] According to an alternative and likewise advantageous embodiment of the invention, the control directional valve device in particular comprises a lifting valve and a lowering valve, wherein the lowering valve has a blocking position and a lowering position, wherein the lowering valve is actuated by a spring device in the direction of the blocking position and can be actuated by means of an electrical actuating device, in particular a magnet, in the direction of the lowering position, and wherein the lifting valve has a blocking position and a lifting position, wherein the lifting valve is actuated by a spring device in the direction of the blocking position and can be actuated by means of an electrical actuating device, in particular a magnet, in the direction of the lifting position.With such a control directional valve device, which has a lifting valve for controlling the lifting operation of the lifting drive and a lowering valve for controlling the lowering operation of the lifting drive, the lifting operation and the lowering operation of the lifting drive can be controlled with a simply constructed lifting valve and a simply constructed lowering valve.

[0023] The invention further relates to an industrial truck, in particular a counterbalance forklift truck or reach truck, with a lifting frame comprising a lifting drive and a hydraulic control system according to the invention.

[0024] The invention has a number of advantages.

[0025] By limiting the pressure peak that occurs in the event of a fault in the control directional valve device, which leads to a digital lifting stop or a digital lowering stop, by the pressure relief valve according to the invention, it is possible to dispense with the need to reinforce the mechanical mast structure of the lifting frame when increasing the maximum lifting speeds and / or lowering speeds of the load handling device to a range greater than 1 m / s, for example, 1.2 m / s. This results in cost savings.

[0026] Furthermore, by eliminating the need to reinforce the mechanical mast structure of the mast, there is no additional restriction of visibility for the operator of the industrial truck when looking through the mast.

[0027] In addition, a reduction in the number of mast variants is possible if different designs of industrial trucks with different maximum lifting speeds and / or lowering speeds of the load handling device in the range of 0.6 m / s and in the range of 1.2 m / s are to be produced, since the design of an industrial truck with a maximum lifting speed and / or lowering speed of the load handling device in the range of 0.6 m / s and the design of an industrial truck with a maximum lifting speed and / or lowering speed of the load handling device in the range of 1.2 m / s can be equipped with the same mast.

[0028] Further advantages and details of the invention are explained in more detail by way of example with reference to the embodiments shown in the schematic figures. Figure 1 shows a first embodiment of a hydraulic control system of a lifting drive according to the invention and Figure 2 shows a second embodiment of a hydraulic control system of a lifting drive according to the invention.

[0029] In the Figure 1 and the Figure 2 a circuit diagram of a hydraulic control system 1 according to the invention of a lifting drive 2 of a lifting frame (not shown in detail) of a non-detailed industrial truck is shown.

[0030] The same components are used in the Figures 1 and 2 provided with the same reference numbers.

[0031] The control system 1 of the Figures 1 and 2 comprises a control directional valve device 5 which is designed to control the lifting operation and the lowering operation of the lifting drive 2.

[0032] In the illustrated embodiments, the lifting drive 2 comprises a plurality of hydraulic lifting cylinders 3a, 3b, 3c. The lifting cylinders 3a, 3b are designed, for example, as mast lifting cylinders. The lifting cylinder 3c is designed, for example, as a free-lift cylinder. The lifting frame (not shown in detail) consists, for example, of a stationary mast and one or more extending masts that can be raised relative to the stationary mast, as well as a load-handling device that is arranged so that it can be raised in the highest-extending extending mast. The lifting cylinders 3a, 3b designed as mast lifting cylinders are designed to raise and lower the extending mast or masts relative to the stationary mast of the lifting frame. The lifting cylinder 3c designed as a free-lift cylinder is designed to raise and lower the load-handling device in the highest-extending extending mast.

[0033] The control directional valve device 5 is connected to a delivery line 10 of a hydraulic pump 11, to a container line 13 leading to a container 12 and to a connecting line 14 leading to the lifting drive 2.

[0034] In the illustrated embodiments, the hydraulic pump 11 is designed as a hydraulic pump operated in an open circuit, which sucks pressure medium from the container 12 by means of a suction line 15 and pumps it into the delivery line 10.

[0035] In the illustrated embodiments, the control directional valve device 5 is part of a directional valve block 16, into which further, not shown in detail

[0036] Control valves which are connected to the conveyor line 10 and the container line 13 and control additional hydraulic consumers of the industrial truck, for example a tilt drive and / or a side shift device of the mast or the load handling device, can be arranged.

[0037] In the illustrated embodiments, the control directional valve device 5 comprises a lifting valve 20 and a lowering valve 21.

[0038] The lowering valve 21 is connected to the connecting line 14 and the container line 13. The lowering valve 21 has a blocking position 21a and a lowering position 21b. In the blocking position 21a, the connection between the connecting line 14 and the container line 13 is blocked. In the open position 21b, the connecting line 14 is connected to the container line 13. In the illustrated embodiments, the lowering valve 21 is provided with a leak-tight blocking position 21a, in which a check valve 22 is effective, blocking in the direction of the container line 13.

[0039] The lowering valve 21 is electrically actuated. In the illustrated embodiments, the lowering valve 21 is actuated by a spring device 23 toward the blocking position 21a and can be actuated by an electrical actuating device 24, for example, a magnet, toward the lowering position 21b.

[0040] The lifting valve 20 is connected to the conveying line 10 and the connecting line 14. The lifting valve 20 has a blocking position 20a and a lifting position 20b. In the blocking position 20a, the connection between the conveying line 10 and the connecting line 14 is blocked. In the open position 20b, the conveying line 10 is connected to the connecting line 14.

[0041] The lifting valve 20 is electrically actuated. In the illustrated embodiments, the lifting valve 20 is actuated by a spring device 25 toward the blocking position 20a and can be actuated by an electrical actuating device 26, for example, a magnet, toward the lifting position 20b.

[0042] To control the control valve device 5, a control device 30, for example an electronic control device 30, is provided, which is connected to the electrical actuating devices 24, 26 of the control valve device 5 by means of electrical cables 31, 32. When the control valve device 5 is actuated, corresponding control signals are carried in the electrical cables 31, 32, which act on the actuating devices 24, 26.

[0043] A pressure limiting device 36 is arranged in a line 35 leading from the delivery line 10 to the container 12. The pressure limiting device 36 is connected on the inlet side to the delivery line 10 and is biased into a blocking position by a spring 37 and into an opening position by the pressure present in the delivery line 10. The pressure limiting device 6 serves to protect the maximum system pressure of the lifting drive 2, for example, the maximum permissible delivery pressure of the hydraulic pump 11 or to limit the nominal load of the lifting drive 2. The opening pressure of the pressure limiting device 6 predetermined by the spring 37 and thus the maximum system pressure of the lifting drive 2 is set, for example, to a value of 280 bar.

[0044] According to the invention, the control system 1 of the Figures 1 and 2a pressure relief valve 40, which is assigned to the connecting line 14. The pressure relief valve 40 is designed to limit a pressure peak introduced into the lifting frame in the event of a fault in the control directional valve device 5.

[0045] In the illustrated embodiments, the pressure relief valve 40 is connected on the inlet side to the connecting line 14 and on the outlet side to the container 12. For this purpose, the pressure relief valve 40 is arranged in particular in a connecting line 51 leading from the connecting line 14 to the container 12. The pressure relief valve 40 is thus arranged and connected in parallel to the control directional valve device 5.

[0046] In the illustrated embodiments, the pressure relief valve 40 has a blocking position 40a and an opening position 40b, wherein the pressure relief valve 40 is acted upon by a spring device 41 in the direction of the blocking position and by the pressure present in the connecting line 14 in the direction of the opening position.

[0047] In the embodiment of the Figure 1 the pressure relief valve 40 is designed as a pressure relief valve 42.

[0048] In the embodiment of the Figure 2 the pressure relief valve 40 is designed as a control valve 43, for example a two-position control valve.

[0049] In the embodiment of the Figure 2 The control valve 43 is designed as a proportional valve that throttles in intermediate positions. Alternatively, the control valve 43 can be designed as a switching valve.

[0050] The opening pressure of the pressure relief valve 40, predetermined by the spring device 41, is preferably set to a value greater than 120% of the maximum system pressure of the lifting drive 2. For example, if the system pressure of the lifting drive protected by the pressure limiting device 36 is 280 bar, the pressure relief valve 40 is preferably set to an opening pressure greater than 330 bar.

[0051] During normal operation of the control system 1 of the Figures 1 and 2The lifting or lowering operation of the lifting drive 2 is controlled by correspondingly controlling the lifting valve 20 or the lowering valve 21. During normal operation of the control system 1, the maximum system pressure is protected by the pressure limiting device 36. The pressure relief valve 40, whose opening pressure preferably corresponds to at least 120% of the maximum system pressure protected by the pressure limiting device 36, therefore does not serve to protect the maximum system pressure during normal operation when raising and lowering the lifting drive 2, so that the pressure relief valve 40 is not used during normal operation and is not actuated into the open position during normal operation.

[0052] The control system 1 is preferably designed such that the maximum lifting speeds and / or lowering speeds of the load handling device controlled by the lifting drive 2 are in the range of greater than 1 m / s, for example 1.2 m / s.

[0053] During lifting or lowering operation of the lifting drive 2, a fault in the control directional valve device 5 can occur, in which the lifting valve 20 or the lowering valve 21 is suddenly actuated by the corresponding spring device 25 or 23 into the locked position 20a or 21a, respectively, and thus the lifting movement or lowering movement of the load-handling device controlled by the lifting drive 2 is suddenly terminated, for example, within a few milliseconds. A fault in the control directional valve device 5 within the meaning of the application is therefore considered, in particular, a fault in the control directional valve device 5 that leads to a sudden stop of the lifting movement or lowering movement of the lifting drive 2. This is also referred to below as a fault in the control directional valve device 5 that leads to a digital lifting stop or digital lowering stop.

[0054] Such a fault in the control directional valve device 5, which leads to a digital lifting stop or a digital lowering stop, is in particular a power failure in the control device 30 and / or a plug break in the electrical cable 31 or 32. As a result of the sudden actuation of the lifting valve 20 or the lowering valve 21 into the blocking position 20a or 21a in such a fault, the load on the load handling device is suddenly stopped and, depending on the previous lifting or lowering speed of the load handling device and the weight of the load picked up on the load handling device, a pulse in the form of a pressure peak is introduced into the lifting frame.

[0055] In the event of such a fault, which leads to a sudden stop of the lifting or lowering movement of the lifting drive 2, the pressure relief valve 40 according to the invention responds and is controlled into the open position by the pressure present in the connecting line 14, counter to the force of the spring device 41. In the event of such a fault, which leads to a sudden stop of the lifting or lowering movement of the lifting drive 2, the pressure relief valve 40 controlled into the open position limits the impulse applied to the mast by limiting the pressure peak. A component failure of the mast in the event of a fault leading to a digital lifting stop or a digital lowering stop can thus be easily prevented with the pressure relief valve 40 according to the invention without reinforcing the mechanical mast structure of the mast.

Claims

1. Hydraulic control system (1) of a lifting drive (2) of a lifting frame of an industrial truck, wherein the control system (1) has a directional control valve device (5) which is connected to a delivery line (10) of a hydraulic pump (11), to a container line (13) routed to the container (12), and to a connecting line (14) routed to the lifting drive (2), wherein the directional control valve device (5) is configured to control the lifting operation and the lowering operation of the lifting drive (2), characterized in that the control system (1) has a pressure protection valve (40), which is associated with the connecting line (14), wherein the pressure protection valve (40) is configured to limit a pressure peak, which is introduced into the lifting frame, in the event of a fault in the directional control valve device (5).

2. Hydraulic control system according to Claim 1, characterized in that the pressure protection valve (40), at the input end, is connected to the connecting line (14) and, at the output end, is connected to the container (12) .

3. Hydraulic control system according to Claim 2, characterized in that the pressure protection valve (40) is configured to limit the pressure peaks, which are introduced into the lifting frame, by connecting the connecting line (14) to the container (12) in the event of a fault in the directional control valve device (5).

4. Hydraulic control system according to any of Claims 1 to 3, characterized in that the pressure protection valve (40) has a blocking position (40a) and an opening position (40b), wherein the pressure protection valve (40) is acted on by a spring device (41) in the direction of the blocking position (40a) and by the pressure prevailing in the connecting line (14) in the direction of the opening position (40b).

5. Hydraulic control system according to any of Claims 1 to 4, characterized in that the pressure protection valve (40) is in the form of a pressure limiting valve (42) .

6. Hydraulic control system according to any of Claims 1 to 4, characterized in that the pressure protection valve (40) is in the form of a control valve (43), in particular a two-position control valve.

7. Hydraulic control system according to Claim 6, characterized in that the control valve (43) is in the form of a switching valve or in the form of a proportional valve which imparts a throttling action in intermediate positions.

8. Hydraulic control system according to any of Claims 4 to 7, characterized in that the spring device (41) is adjusted to an opening pressure of the pressure protection valve (40) that is greater than 120% of the maximum system pressure of the lifting drive (2), preferably is greater than 330 bar.

9. Hydraulic control system according to Claim 8, characterized in that the control system (1) has a pressure limiting device (36) which, at the output end, is connected to the delivery line (10) and is configured to protect the maximum system pressure of the lifting drive (2).

10. Hydraulic control system according to any of Claims 1 to 9, characterized in that the directional control valve device (5) is electrically actuated.

11. Hydraulic control system according to Claim 10, characterized in that the directional control valve device (5) comprises a directional control valve, which has a neutral position, a lowering position and a lifting position, wherein the directional control valve is actuated into the neutral position by a spring device, can be actuated in the direction of the lowering position by means of a first electrical actuating device, in particular a magnet, and can be actuated in the direction of the lifting position by means of a second electrical actuating device, in particular a magnet.

12. Hydraulic control system according to Claim 10, characterized in that the directional control valve device (5) comprises a lifting valve (20) and a lowering valve (21), wherein the lowering valve (21) has a blocking position (21a) and a lowering position (21b), wherein the lowering valve (21) is actuated in the direction of the blocking position (21a) by the spring device (23) and can be actuated in the direction of the lowering position (21b) by means of an electrical actuating device (24), in particular a magnet, and wherein the lifting valve (20) has a blocking position (20a) and a lifting position (20b), wherein the lifting valve (20) is actuated in the direction of the blocking position (20a) by a spring device (25) and can be actuated in the direction of the lifting position (20b) by means of an electrical actuating device (26), in particular a magnet.

13. Industrial truck, in particular counterbalance forklift truck or reach truck, having a lifting frame comprising a lifting drive (2), and having a hydraulic control system (1) according to any of the preceding claims for controlling the lifting drive (2).