Fork hydraulic system for a fork truck and fork truck

Abstract

This application belongs to the field of engineering machinery and discloses a hydraulic system for forklifts and a forklift truck. The hydraulic system includes a first cylinder and a second cylinder, with the rod-side chambers of the first and second cylinders interconnected. The rodless chamber of the first cylinder is connected to a first lateral movement working oil circuit, and the rodless chamber of the second cylinder is connected to a second lateral movement working oil circuit. It also includes a multi-way valve and a directional valve. The directional valve is located at the boom head of the forklift truck. The first and second lateral movement working oil circuits are hydraulically connected to the attachment group oil circuit of the multi-way valve through the directional valve. This application can drive the two cylinders to produce synchronous lateral movement on corresponding sides, thereby achieving synchronous lateral movement hydraulic drive. This application allows for non-manual adjustment of the fork blade spacing, which not only facilitates fork lifting but also allows for adjustment of the left and right position of the load on the fork mast after the forks are loaded, facilitating precise stacking of heavy objects.

Description

Technical Field

[0001] This application belongs to the field of construction machinery, specifically relating to a forklift truck and its fork hydraulic system. Background Technology

[0002] When a forklift forklift is loaded, it is difficult to move heavy objects sideways on the forks using only manual labor, making stacking difficult. Therefore, the fork cutters can only be moved manually when unloaded or lightly loaded. This is not only time-consuming and labor-intensive, but for heavier forks, several people are needed to move them, resulting in high labor costs. Moreover, each manual movement of the fork cutters requires frequent back-and-forth movement between the cab and the forks, further wasting operation time. Utility Model Content

[0003] The purpose of this application is to provide a hydraulic system for forks and a forklift truck for achieving synchronous left and right side movement of the fork blades.

[0004] To achieve the above objectives, this application provides a hydraulic system for forks in a forklift truck, the hydraulic system comprising: A first hydraulic cylinder and a second hydraulic cylinder, wherein the rod chambers of the first hydraulic cylinder and the second hydraulic cylinder are interconnected, the rodless chamber of the first hydraulic cylinder is connected to a first lateral displacement working oil circuit, and the rodless chamber of the second hydraulic cylinder is connected to a second lateral displacement working oil circuit. A multi-way valve and a directional valve are provided, the directional valve being arranged at the boom head of the forklift, and the first lateral movement hydraulic circuit and the second lateral movement hydraulic circuit being hydraulically connected to the attachment assembly hydraulic circuit of the multi-way valve via the directional valve.

[0005] In some embodiments, the fork hydraulic system includes: The working oil circuit is closed, and hydraulically connected to the rod chamber of the first oil cylinder and the rod chamber of the second oil cylinder; The working oil circuit is opened, and the hydraulic connection is made to the rodless chamber of the first oil cylinder and the rodless chamber of the second oil cylinder. The reversing valve is used to connect the attachment group oil circuit of the multi-way valve to the first lateral movement working oil circuit and the second lateral movement working oil circuit, or to switch to the closing working oil circuit and the opening working oil circuit.

[0006] In some embodiments, both the first lateral movement working oil circuit and the second lateral movement working oil circuit are equipped with hydraulic locks, and both the closing working oil circuit and the opening working oil circuit are equipped with speed regulating valves, overflow valves and hydraulic locks.

[0007] In some embodiments, the hydraulic valves in the first lateral movement hydraulic circuit, the second lateral movement hydraulic circuit, the closing hydraulic circuit, and the opening hydraulic circuit are integrated into a hydraulic valve assembly, which is arranged on the forks of the forklift.

[0008] In some embodiments, the directional valve is a two-position six-way solenoid directional valve.

[0009] In some embodiments, the fork hydraulic system includes: The quick-change connectors connect the first lateral displacement working oil circuit, the second lateral displacement working oil circuit, the closing working oil circuit, and the opening working oil circuit to the directional valve via their respective quick-change connectors.

[0010] In some embodiments, the fork hydraulic system includes: An on / off control valve is used to control the cut-off or connection between the rodless chamber of the first cylinder and the rodless chamber of the second cylinder.

[0011] In some embodiments, the on / off control valve is a cartridge valve disposed in the connecting oil circuit between the opening working oil circuit and the second lateral shift working oil circuit.

[0012] In some embodiments, the fork hydraulic system includes: The shuttle valve has two comparison ports hydraulically connected to the first side-shift working oil circuit and the second side-shift working oil circuit, respectively, and its outlet port is hydraulically connected to the control port of the cartridge valve.

[0013] In addition, this application also provides a forklift truck, which includes the fork hydraulic system for forklift truck described above in this application.

[0014] In the technical solution of this application, the rod chambers of the two hydraulic cylinders are interconnected, i.e., the two hydraulic cylinders are connected in series. Therefore, according to the lateral movement direction, by controlling the multi-way valve and the directional valve, high-pressure oil can be supplied to the corresponding rodless chamber through the corresponding lateral movement hydraulic circuit, thereby driving the two hydraulic cylinders to move synchronously, thus achieving synchronous lateral movement hydraulic drive. In this way, adjusting the fork blade spacing in a non-manual manner not only facilitates fork loading but also allows for adjustment of the left and right position of the load on the fork mast after the forks are loaded, facilitating precise stacking of heavy objects.

[0015] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without any inventive effort. In the drawings: Figure 1 This is a hydraulic schematic diagram of a fork hydraulic system according to a specific embodiment of this application.

[0017] Explanation of reference numerals in the attached figures Detailed Implementation

[0018] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0019] The following description, with reference to the accompanying drawings, describes a fork hydraulic system and a forklift truck according to this application.

[0020] As mentioned earlier, current technology typically involves manually moving the forks to achieve lateral movement, thereby adjusting the lateral position of the transported goods. However, in the era of mechanized operations, this manual method is outdated. Efforts should be made to replace manual labor with automated machinery, which will not only save operators' physical strength and operating time, but also compensate for demanding operating conditions that cannot be met by human labor.

[0021] Therefore, this application discloses a novel hydraulic system for forks, applicable to forklift trucks. For example... Figure 1 As shown, in one specific embodiment, the fork hydraulic system includes: The first hydraulic cylinder 100 and the second hydraulic cylinder 200 are connected to each other by rod chambers. The rodless chamber of the first hydraulic cylinder 100 is connected to the first lateral displacement working oil circuit L1, and the rodless chamber of the second hydraulic cylinder 200 is connected to the second lateral displacement working oil circuit L2. The multi-way valve 20 and the directional valve 30 are located at the boom head of the forklift. The first lateral movement working oil circuit L1 and the second lateral movement working oil circuit L2 are hydraulically connected to the attachment group oil circuit of the multi-way valve 20 through the directional valve 30.

[0022] In this design, the first cylinder 100 and the second cylinder 200 are both drive cylinders used to drive the fork blades to close or open. In this application, the two cylinders are connected in series, meaning the rod-side chambers of the first cylinder 100 and the second cylinder 200 are interconnected, and their respective rodless chambers are connected to working oil circuits. By controlling the multi-way valve 20 and the directional valve 30, the multi-way valve 20 controls the oil supply, and the directional valve 30 controls the connection or disconnection of the lateral movement working oil circuit with the multi-way valve. When high-pressure oil is supplied to the selected lateral movement working oil circuit, the two cylinders can be driven to produce corresponding lateral movement, thereby achieving lateral hydraulic drive. This design allows for non-manual adjustment of the fork blade spacing, facilitating the adjustment of the blades for picking up goods when the forks are unloaded. It also allows for non-manual adjustment of the left and right positions of the load on the fork mast after the forks are loaded, facilitating precise stacking of heavy objects.

[0023] See Figure 1 The fork hydraulic system also includes: Close the working oil circuit L3, which is hydraulically connected to the rod chamber of the first oil cylinder 100 and the second oil cylinder 200; Open the working oil circuit L4, which is hydraulically connected to the rodless chamber of the first oil cylinder 100 and the second oil cylinder 200; The reversing valve 30 is used to connect the attachment group oil circuit of the multi-way valve 20 to the first side-moving working oil circuit L1 and the second side-moving working oil circuit L2, or to switch to the closing working oil circuit L3 and the opening working oil circuit L4.

[0024] As shown in the figure, one side port of the directional valve 30 is hydraulically connected to the attachment group oil circuit of the multi-way valve 20, and the other side port is hydraulically connected to the first lateral movement working oil circuit L1, the second lateral movement working oil circuit L2, the closing working oil circuit L3, and the opening working oil circuit L4, respectively. The pumping hydraulic oil from the hydraulic pump 10 is delivered to the directional valve 30 through the output port of a certain main valve plate of the multi-way valve 20 (i.e., the attachment group oil circuit). Through the reversing action of the main valve plate and the directional valve 30, the oil can be selectively delivered to a certain working oil circuit, thereby driving the fork cutters to achieve the corresponding lateral movement.

[0025] In the diagram, when the directional valve 30 is in its left position, the pumped hydraulic oil can only flow to either the closing working oil circuit L3 or the opening working oil circuit L4. The first lateral movement working oil circuit L1 and the second lateral movement working oil circuit L2 are either cut off or return oil, meaning that only the fork closing or fork opening actions can be performed, and the fork lateral movement is locked. The direction of the pumped hydraulic oil flow is determined by a specific main valve plate of the multi-way valve 20, which determines whether the pumped hydraulic oil flows to the closing working oil circuit L3 and returns oil to the opening working oil circuit L4, or vice versa.

[0026] With the directional valve 30 in the right position as shown in the diagram, the hydraulic oil pumped by the hydraulic pump 10 can only flow through the attachment assembly oil circuit and the directional valve 30 to either the first lateral movement working oil circuit L1 or the second lateral movement working oil circuit L2. The closing working oil circuit L3 and the opening working oil circuit L4 are cut off or returned, meaning only fork lateral movement can be performed; the fork closing or fork opening actions are locked. Similarly, a valve plate of one of the main valves of the multi-way valve 20 determines whether the pumped hydraulic oil flows to the first lateral movement working oil circuit L1 and returns through the second lateral movement working oil circuit L2, or flows to the second lateral movement working oil circuit L2 and returns through the first lateral movement working oil circuit L1.

[0027] As can be seen, the fork hydraulic system of this embodiment integrates multiple actions such as synchronous closing, synchronous opening, synchronous leftward movement, and synchronous rightward movement of the fork blades. It achieves the synchronous closing and opening, and synchronous left and rightward movement of the fork blades using only one directional valve and one hydraulic control valve assembly, resulting in a simple system structure and sufficient functionality.

[0028] In this embodiment, the directional control valve 30 is a two-position, six-way solenoid directional control valve, which can be integrated with the vehicle's electronic control system. Before switching to fork side-shifting operation, the operator can perform the switching action via a button. Those skilled in the art will understand that the directional control valve 30 can also be a manual directional control valve or a hydraulic directional control valve, etc., but this will not be elaborated on here.

[0029] In this embodiment, the hydraulic valves in the first lateral movement working circuit L1, the second lateral movement working circuit L2, the closing working circuit L3, and the opening working circuit L4 are all arranged on the forks of the forklift, while the directional valve 30 is arranged at the boom head of the forklift. This design, placing the solenoid directional valve at the boom head and the hydraulically controlled valve assembly integrating various hydraulic valves on the forks, avoids placing too many hydraulic components at the boom head, resulting in a bulky structure. Placing the solenoid directional valve at the boom head also facilitates cable routing, avoiding the need for cables to extend to the forks, which would require the cables to be designed for movement and increase the risk of damage.

[0030] Furthermore, the fork hydraulic system may also include quick-change connectors 40, and the first lateral movement working oil circuit L1, the second lateral movement working oil circuit L2, the closing working oil circuit L3 and the opening working oil circuit L4 are respectively connected to the directional valve 30 through their respective quick-change connectors 40.

[0031] The pipeline between the solenoid directional valve at the boom head and the hydraulic control valve assembly on the forks uses a quick-connect 40mm coupling, allowing for quick insertion and removal and enabling rapid replacement of different attachments. At the same time, the solenoid directional valve at the boom head can adapt to different attachment operation requirements.

[0032] The hydraulic valves in each working oil circuit can be integrated into a hydraulic valve assembly as shown in the dashed box. For details, see [link to documentation]. Figure 1The hydraulic valves in the first lateral displacement working oil circuit L1 and the second lateral displacement working oil circuit L2 both include a hydraulic lock 70. The hydraulic valves in the closing working oil circuit L3 and the opening working oil circuit L4 both include a speed control valve 50, a relief valve 60, and a hydraulic lock 70. The hydraulic lock 70 is used as a balance valve in the closing working oil circuit L3 and the opening working oil circuit L4. The relief valve 60 is used for high-pressure side to low-pressure side relief between the closing working oil circuit L3 and the opening working oil circuit L4. The speed control valve 50 is used to control the flow rate of the oil circuit. It can be seen that the hydraulic control valve group contains two speed control valves, two relief valves, one shuttle valve, one check valve 91, one damper, two bidirectional hydraulic locks, and one cartridge valve.

[0033] By incorporating two overflow valves, damage to structural and hydraulic components due to overpressure during the fork's closing and opening process can be prevented. Two sets of hydraulic locks (6.1 and 6.2) prevent the fork cylinders from moving freely in non-operational states, while ensuring that the two working oil circuits D1 / D4 and D2 / D3 operate independently without interference. The design of two sets of bidirectional hydraulic locks to mutually isolate the two sets of actuation oil circuits avoids oil circuit interference. A cartridge valve is designed to switch between the two sets of fork movements; this design is simple, reliable, efficient, and prevents malfunctions.

[0034] Furthermore, the fork hydraulic system of this embodiment may also include: The on / off control valve 80 is used to control the cut-off or connection between the rodless chamber of the first cylinder 100 and the rodless chamber of the second cylinder 200.

[0035] By setting an on / off control valve 80, the hydraulic passages for the fork closing / opening and synchronous left / right lateral movement modes can be isolated. When the forks are closing / opening, the on / off control valve 80 is in the conducting state, and the C1 / C2 ports of the hydraulic control valve group shown in the dashed box are connected, i.e., the two rodless chambers are connected. When the forks are moving laterally, the on / off control valve 80 is in the closed state, and the C1 / C2 ports are not connected. This control method is simple, efficient, and reliable, and can avoid malfunctions during the fork control process. The on / off control valve 80 can be electrically controlled using a solenoid valve, but in this embodiment, the on / off control valve 80 is configured as a cartridge valve in the connecting oil circuit between the opening working oil circuit L4 and the second side-shifting working oil circuit L2. The cartridge valve not only facilitates the passage of large flow rates of oil, but also enables automatic on / off control via hydraulic control, as will be described in detail below.

[0036] To achieve automatic hydraulic control of the on / off control valve 80, the fork hydraulic system may include: The shuttle valve 90 has two comparator ports that are hydraulically connected to the first side-shift working oil circuit L1 and the second side-shift working oil circuit L2, respectively, and its outlet port is hydraulically connected to the control port of the cartridge valve.

[0037] By setting the shuttle valve 90, high-pressure oil from the first side-shifting working oil circuit L1 and the second side-shifting working oil circuit L2 can be introduced into the control port of the cartridge valve as pilot oil. Simultaneously, it can also serve as a drain channel for the oil in the control port of the cartridge valve, discharged through the check valve 91. In this way, whether moving to the left or right, the cartridge valve can be locked, thus cutting off the connection between the rodless chambers of the two cylinders. However, during the fork closing or unfolding operation, since there is no high-pressure oil in the first side-shifting working oil circuit L1 and the second side-shifting working oil circuit L2, the cartridge valve cannot be locked, meaning the two rodless chambers remain connected.

[0038] The following combination Figure 1 The working process of the fork hydraulic system is explained in detail.

[0039] When the electromagnet Y1 of the directional valve 30 is de-energized, pressure oil is output through port A of the attachment group oil circuit of the multi-way valve 20, reaching port P1 of the directional valve 30, then through port V1 of the directional valve 30 to port D1 of the hydraulic control valve group, then through the speed control valve 50 in the hydraulic control valve group, through the hydraulic lock 70, and output through port C3 to the rod chamber of the two fork cylinders, causing the two cylinders to retract and realize the fork closing action.

[0040] When the electromagnet Y1 of the directional valve 30 is de-energized, the pressure oil output through port B of the attachment group oil circuit of the multi-way valve 20 reaches port P2 of the solenoid directional valve, then through port C4 of the solenoid directional valve to port D4 of the hydraulic control valve group, then through the speed control valve 50 of the hydraulic control valve group, through the hydraulic lock 70, and after being diverted, is output from ports C2 / C1 to the rodless chambers of the two fork cylinders respectively, and the two cylinders extend to realize the fork opening action.

[0041] When the electromagnet Y1 of the solenoid directional valve 30 is energized, pressure oil is output through port A of the attachment group oil circuit of the multi-way valve 20, reaching port P1 of the solenoid directional valve, then through port C2 of the solenoid directional valve to port D2 of the hydraulic control valve group, and then through the hydraulic lock 50 in the hydraulic control valve group to the rodless chamber of the second cylinder 200 via port C1. At this time, since the two fork cylinders are connected in series, the second cylinder 200 extends and the first cylinder 100 retracts, realizing the synchronous movement of the forks to the left.

[0042] When the electromagnet Y1 of the solenoid directional valve 30 is energized, pressure oil is output through port B of the attachment group oil circuit of the multi-way valve 20, reaching port P2 of the solenoid directional valve, then through port C3 of the solenoid directional valve to port D3 of the hydraulic control valve group, and finally through the hydraulic lock 70 of the hydraulic control valve group to the rodless chamber of the first cylinder 100 via port C2. At this time, the two fork cylinders are connected in series, the first cylinder 100 extends, and the second cylinder 200 retracts, realizing the synchronous movement of the forks to the right.

[0043] This application also protects a forklift truck including the fork hydraulic system described above. As can be seen, this application constructs a hydraulic system capable of controlling the lateral movement of the forks by arranging a directional valve at the boom head and a hydraulically controlled valve assembly on the forks. The power source for this hydraulic system controlling the lateral movement of the forks can be provided by the piston pump of the vehicle's overall hydraulic system and output through the attachment assembly oil circuit of the multi-way valve 20. The A / B ports of the attachment assembly oil circuit of the multi-way valve are connected to the P1 / P2 ports of the solenoid directional valve arranged at the boom head. The solenoid directional valve arranged at the boom head is a two-position six-way directional valve, and its V1 / V2 / V3 / V4 ports are respectively connected to the D1 / D2 / D3 / D4 ports of the hydraulically controlled valve assembly arranged on the forks. The connection method is using a quick-connect coupling 40, which allows for quick insertion and removal, facilitating attachment replacement. The C1 / C2 / C3 ports of the hydraulic control valve assembly arranged on the forks are respectively connected to the rodless chamber of the second cylinder 200, the rod chamber of the two fork cylinders, and the rodless chamber of the first cylinder 100.

[0044] The forklift truck and its fork hydraulic system of this application replace manual operation with automated mechanical operation, saving physical strength; it can avoid operators frequently going back and forth between the cab and the forks to adjust the fork spacing, saving operation time and improving efficiency; it solves the problem that heavy objects cannot move left and right on the forks after being loaded; it uses cartridge valves to isolate the oil passages of the two sets of fork movements, which can avoid malfunctions, and the control method is simple, efficient and reliable.

[0045] It should be noted that the hydraulic valve assembly can be replaced by an electrically controlled valve assembly or a manually controlled valve assembly. Solenoid valves or mechanical valves are combined to control the hydraulic circuit to achieve the purpose of controlling the fork's movement. Any valve assembly that can control the hydraulic circuit to control the fork's movement is acceptable.

[0046] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0047] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A hydraulic system for a fork lift truck, characterised in that, The fork hydraulic system includes: The first hydraulic cylinder (100) and the second hydraulic cylinder (200) are connected to each other by rod chambers. The rodless chamber of the first hydraulic cylinder (100) is connected to a first lateral movement working oil circuit (L1), and the rodless chamber of the second hydraulic cylinder (200) is connected to a second lateral movement working oil circuit (L2). A multi-way valve (20) and a directional valve (30) are provided, the directional valve (30) being arranged at the boom head of the forklift, the first lateral movement working oil circuit (L1) and the second lateral movement working oil circuit (L2) being hydraulically connected to the attachment group oil circuit of the multi-way valve (20) via the directional valve (30).

2. The hydraulic system for a fork truck according to claim 1, wherein, The fork hydraulic system includes: Close the working oil circuit (L3), which is hydraulically connected to the rod chamber of the first oil cylinder (100) and the rod chamber of the second oil cylinder (200); Open the working oil circuit (L4), which is hydraulically connected to the rod chamber of the first oil cylinder (100) and the rodless chamber of the second oil cylinder (200); The reversing valve (30) is used to connect the attachment group oil circuit of the multi-way valve (20) to the first side-shifting working oil circuit (L1) and the second side-shifting working oil circuit (L2), or switch to connect to the closing working oil circuit (L3) and the opening working oil circuit (L4).

3. The hydraulic system for a fork truck according to claim 2, wherein, The first lateral movement working oil circuit (L1) and the second lateral movement working oil circuit (L2) are each equipped with a hydraulic lock (70), and the closing working oil circuit (L3) and the opening working oil circuit (L4) are each equipped with a speed regulating valve (50), an overflow valve (60) and a hydraulic lock (70).

4. The hydraulic system for a fork truck according to claim 3, wherein, The hydraulic valves in the first lateral movement working oil circuit (L1), the second lateral movement working oil circuit (L2), the closing working oil circuit (L3), and the opening working oil circuit (L4) are integrated into a hydraulic valve group, which is arranged on the forks of the forklift truck.

5. The hydraulic system for a fork truck fork according to claim 2, wherein, The reversing valve (30) is a two-position six-way electromagnetic reversing valve.

6. The hydraulic system for a fork lift truck according to any one of claims 2 to 5, wherein The fork hydraulic system includes: The quick-change connector (40) is used to connect the first lateral shift working oil passage (L1), the second lateral shift working oil passage (L2), the closing working oil passage (L3), and the opening working oil passage (L4) to the reversing valve (30) through their respective quick-change connectors (40).

7. The hydraulic system for a fork lift truck according to any one of claims 2 to 5, wherein The fork hydraulic system includes: An on / off control valve (80) is used to control the cut-off or connection between the rodless chamber of the first cylinder (100) and the rodless chamber of the second cylinder (200).

8. The hydraulic system for a fork truck of claim 7, wherein, The on / off control valve (80) is a cartridge valve installed in the connecting oil circuit between the opening working oil circuit (L4) and the second side-shifting working oil circuit (L2).

9. The hydraulic system for a fork truck fork according to claim 8, wherein, The fork hydraulic system includes: The shuttle valve (90) has two comparison ports that are hydraulically connected to the first side-shift working oil circuit (L1) and the second side-shift working oil circuit (L2), respectively, and its outlet port is hydraulically connected to the control port of the cartridge valve.

10. A fork truck characterized by: The forklift truck includes a fork hydraulic system for a forklift truck according to any one of claims 1 to 9.

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