EP1967485B1 - Industrial truck - Google Patents

Description

The invention relates to an industrial truck according to claim 1. In particular, the invention relates to an industrial truck, which also has auxiliary functions in addition to a lifting and lowering function for a load-carrying means, in particular for the load-carrying means.

Such a truck is about out DE 698 07 098 T4 2004.07.15 known. In addition to the lifting and lowering function is the process of the fork from the mast away or on this to accomplish by means of an adjusting cylinder and also the pivoting of the lifting device. It is also known to tilt the load-carrying means, for example the fork, not only about a horizontal axis, but also to move laterally along a horizontal axis. Finally, a so-called three-way stacker has become known, in which the fork can also be pivoted about a vertical axis.

JP 2003 267682 describes an industrial truck, wherein a switching valve is arranged in the form of a proportional valve on the carrier.

The operation of the individual functions in the trucks is usually done by hydraulic means. In the drive part of the truck, a motor-driven hydraulic pump is arranged, which is connected via hoses with the control valves for the individual functions.

The functions tilting and side thrust of a lifting device, which is mounted on a height-adjustable support are usually operated by proportional valves. Between the proportional valve, which is usually located in the drive part and the consumer on the mast are often several meters hydraulic hose. At a function request, the hydraulic hose is pressurized. He expands while doing so. Since the secondary functions only require a small volume flow, for example 6 to 8 liters per minute, the effect described results in a clear response delay of the secondary functions. This effect occurs more frequently with longer hoses, ie with larger lifting heights, and larger payloads, since with the length of the hose and increasing pressure also the storage capacity of the hoses increases.

In the not pre-published EP 1 760 033 A2 For a stapler which is mounted on a mast of a truck for the operation of clamp cylinders, a switching valve in the drive part is arranged. A proportional valve for quick control of the clamping pressure in the clamping cylinders is arranged on the support for the clamps. To open or close the brackets, the proportional valve is not provided.

The invention has for its object to provide a truck with mast to be operated on the load fork, wherein the response delay is reduced.

This object is solved by the features of patent claim 1.

In the invention, the proportional valve is mounted on the carrier, and on the drive part, a switching valve is arranged, which connects the hydraulic hose selectively with the hydraulic pump or separates from this. The actuated via the proportional valve cylinder adjust the fork laterally or in their inclination to the horizontal.

If the proportional valve is positioned directly on the carrier, for example for the forklift, in the vicinity of the load, the hoses can be filled with a significantly higher volume flow than is necessary for the supply of the functions, since the throttle point no longer starts, but instead output (load side) of the hydraulic hoses. This reduces the response time of the functions as the dead time caused by the tubing expansion is reduced due to the higher pump speed to be set. After the filling phase of the hydraulic hose, the speed of the pump can provide the required pressure reserve. The output pressure of the hydraulic pump is directly at the proportional valve. This ensures that the volume flow demand of the consumer at all times have sufficient reserves, which leads to a much more constant operating speed, especially if more consumers are to be supplied by the pump.

In order to further reduce the dead time until the hoses have been completely filled, the pump speed can be significantly increased for a short time after a secondary function has been requested.

The invention is suitable for a function of lateral displacement of the fork and a tilt adjustment of the fork about a horizontal axis. For each function an adjusting cylinder is required. These can be controlled according to an embodiment of the invention via a common proportional valve having a neutral position and two working positions, each working position is associated with a hydraulic cylinder.

It is customary to provide a pressure compensator for a control via a proportional valve in order to regulate the set volume flow. Therefore, the invention provides that a pressure compensator associated with the proportional valve is mounted on the carrier.

In summary, it can therefore be stated that, by virtue of the arrangement according to the invention of the valves on the output side or load side of the hoses, the dynamic pressure upstream of the proportional valve does not occur on the input side, but on the output side, i.e. on the output side. So the load side of the hydraulic hoses is generated and thus can turn out higher. Volume flow and pressure are thereby uniform, and the pressure loss in the lines is compensated.

Fig. 1

zeigt äußerst schematisch die Seitenansicht eines Schubmaststaplers.

Fig. 2

zeigt eine hydraulische Schaltungsanordnung für den Schubmaststapler nach Fig. 1.

The invention will be explained in more detail with reference to drawings.

Fig. 1

shows very schematically the side view of a reach truck.

Fig. 2

shows a hydraulic circuit arrangement for the reach truck Fig. 1 ,

An in Fig. 1 illustrated reach truck 30 has a mast 32 which is held on the drive member 34 and by means of a hydraulic cylinder, not shown, along the double arrow 36 is displaceable. On the mast 32, a support 38 is adjustable in height, as indicated by double arrow 40. On the carrier 38, a load fork 42 is mounted, which is pivotable about a horizontal axis with the aid of an adjusting cylinder, also not shown, as indicated by double arrow 44. The load fork 42 is also displaceable along a horizontal axis relative to the carrier 38, as indicated by arrow ends 46. Again, an adjusting cylinder is required.

In Fig. 2 is a lifting cylinder 23 for the mast 32 to recognize, which is connected via a load-holding and lowering valve 21 and a pressure compensator 22 to a hydraulic pump 1.

In Fig. 2 Furthermore, an adjusting cylinder 5 is provided, for example, for the inclination of the fork 42. An adjusting cylinder 6 is for the side thrust of the fork 42 in accordance with 46 in Fig. 1 intended. An adjusting cylinder 17 is provided for the mast thrust 36.

The hydraulic adjusting cylinders 5, 6 and 17 are also supplied by the hydraulic pump 1, which is driven by an electric motor, not shown. It sucks hydraulic medium from a tank 20. A pressure line 9 from the pump 1 leads to a switching valve 10, which shuts off the pressure line 9 in the illustrated neutral position. In the event of overpressure, a pressure relief valve 19 responds in order to return medium to the tank 20. From the switching valve 10 go from two pressure lines 7, 8, in the form of Hydraulic hoses to the hydraulic cylinders 5, 6 are guided. They may have a length of several meters, depending on the maximum lifting height of the fork 42. At the end of the hydraulic lines 7, 8, a pressure compensator 2 and a proportional valve 11 is arranged. These two hydraulic components are located on the carrier 38 according to Fig. 1 , The proportional valve 11 has a neutral position, in which both hydraulic cylinders 5, 6 are not supplied with medium. In one working position, a supply of one of the two hydraulic cylinders 5, 6 takes place in accordance with the controlled electromagnet for the proportional valve. In this case, the pressure compensator 2 ensures that a controlled volume flow is supplied to the hydraulic cylinder 5 and 6, respectively. It depends on the switching position of the switching valve 10, which side of the hydraulic valve 5 and 6 supplied with pressure medium and which side is connected to the tank 10.

The hydraulic unit (valve block) of pressure compensator 2 and proportional valve 11, which is scrapped by a dot-dash line 26, is located on the carrier 38 for the load fork 42.

A proportional valve 16, preceded by a pressure compensator 24, is also in the vehicle, i. housed in the drive part 34 and provides for the proportional control of the working cylinder 17 for the mast thrust.

The valve block 25 according to Fig. 2 is located on the vehicle.

During the filling phase of the hydraulic lines (hoses) 7, 8, Q _1.1 > Q ₁ . Q is the volume flow at the pump speed n. Q _1.1 is the volume flow at the pump speed n ₁ . During the movement phase Q _{1.1 is} greater than or equal to Q _1. After the filling phase of the hose, the speed n, the pump 1 provides the required pressure reserve p _1.1 . The pressure p _1.1 between the pump 1 and 2 pressure compensator is greater p _2.1 , ie at the entrance of the cylinder 5 and 6. This ensures that the volume flow requirement of the hydraulic cylinder 5, the sixth always have enough reserves, which leads to a constant speed of operation.

To further reduce the dead time until the hydraulic hoses 7, 8 have been completely filled, the pump speed can be significantly increased for a short time after a function has been requested. Volume flow Q _2.1 between the proportional valve 11 and cylinder 5 or 6 and pressure p _2.1 are thereby uniform, and the pressure in the lines 7, 8 is compensated.

$${\mathrm{Q}}_{\mathrm{1}}<{\mathrm{Q}}_{1.1}$$

$${\mathrm{Q}}_2\le {\mathrm{Q}}_{\mathrm{2.1}}$$

$${\mathrm{Q}}_2<{\mathrm{Q}}_{1.1}$$

$${\mathrm{Q}}_{\mathrm{1.1}}>{\mathrm{Q}}_{\mathrm{2.1}}$$

$${\mathrm{p}}_{\mathrm{1}}>{\mathrm{p}}_{\mathrm{2}}$$

$${\mathrm{p}}_{\mathrm{1.1}}>{\mathrm{p}}_{\mathrm{2.1}}$$

$${\mathrm{p}}_{\mathrm{1}}<{\mathrm{p}}_{\mathrm{1.1}}$$

$${\mathrm{p}}_2<{\mathrm{p}}_{\mathrm{2.1}}$$

In general, the following terms apply: $${\mathrm{Q}}_{\mathrm{1}}>{\mathrm{Q}}_{\mathrm{2}}$$

$${\mathrm{Q}}_{\mathrm{1}}<{\mathrm{Q}}_{1.1}$$

$${\mathrm{Q}}_2\le {\mathrm{Q}}_{\mathrm{2.1}}$$

$${\mathrm{Q}}_2<{\mathrm{Q}}_{1.1}$$

$${\mathrm{Q}}_{\mathrm{1.1}}>{\mathrm{Q}}_{\mathrm{2.1}}$$

$${\mathrm{p}}_{\mathrm{1}}>{\mathrm{p}}_{\mathrm{2}}$$

$${\mathrm{p}}_{\mathrm{1.1}}>{\mathrm{p}}_{\mathrm{2.1}}$$

$${\mathrm{p}}_{\mathrm{1}}<{\mathrm{p}}_{\mathrm{1.1}}$$

$${\mathrm{p}}_2<{\mathrm{p}}_{\mathrm{2.1}}$$

Claims (4)

1. A floor conveyor with a drive portion and a load portion, wherein the load portion has a lifting scaffold, on which a carrier for a load fork or an attachment device is guided to be adjustable in height, and at least one hydraulic adjusting cylinder is assigned to the carrier for adjusting the load fork or a part on the attachment device, and wherein a hydraulic pump driven by a motor is arranged in the drive portion, which is connected to the adjusting cylinder via a proportional valve and hydraulic tubes, the load fork (42) being laterally shiftable and/or being hingedly mounted in its inclination towards the horizontal, and an adjusting cylinder being provided for shifting and/or for inclining and the proportional valve (11) being mounted on the carrier (38), characterised in that an on-off valve (10) is arranged on the drive portion (34), which selectively connects the hydraulic tubes (7, 8) to or disconnects them from the hydraulic pumps (1).
2. A floor conveyor according to claim 1, characterised in that the two adjusting cylinders (5, 6) are connected with the hydraulic tubes (7, 8) via a proportional valve (11), which has one neutral position and two working positions, wherein one working position is assigned to one adjusting cylinder at a time (5, 6).
3. A floor conveyor according to claim 1 or 2, characterised in that a pressure balance (2) connected upstream to the proportional valve (11) is also arranged on the carrier (38).
4. A floor conveyor according to any one of claims 1 to 3, characterised in that a control device is provided, which upon actuation of an adjusting cylinder (5, 6) triggers the pump motor (1) such that it has an excessive rotational speed for a short time.

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