EP3272696B1 - Cylinder/piston assembly for an outrigger - Google Patents

Description

The present invention relates to a cylinder / piston unit, in particular for a support, which has a hydraulic cylinder with a cylinder chamber and a longitudinally movable piston, wherein the piston carries a piston rod, which is at least partially hollow.

Such a cylinder / piston unit is from the Scriptures

DE 20 2014 000 335 U1 known. By the at least partially hollow piston rod, an electrical signal line can be guided, via which a force sensor integrated in the piston rod can be read out. The electrical signal line is designed as a spiral cable and leads from the piston rod through an opening in the piston in the cylinder chamber filled with hydraulic fluid and through it to the end of the hydraulic cylinder facing away from the piston, where the signal line via an electrical feedthrough from the cylinder / piston unit exits and leads from there to an evaluation device.

Leading the signal cable through the cylinder chamber has certain disadvantages in terms of reliability and life expectancy of the cylinder / piston unit. On the one hand, there is the danger that the signal cable is trapped between the piston and the cylinder end when the piston is completely retracted and thus takes damage. On the other hand, the insulating sheath of the signal line can be attacked by the hydraulic means.

From the Scriptures DE202009004673 is a cylinder / piston assembly with a hollow piston rod is known in which a solid rod attached to the cylinder bottom solid rod protrudes into the piston rod and is inserted into this. By means of sliding contacts can be made via the inner rod an electrical connection between the piston rod and the cylinder bottom become. Again, the running through the hydraulic space electrical connection on the one hand on the other hand susceptible to wear.

In Scripture US 4,879,440 A , which discloses a cylinder / piston unit according to the preamble of claim 1, a hydraulic cylinder is shown in which from the cylinder bottom protrudes a rod-shaped support member into the cylinder chamber, which telescopically in the inside hole piston rod can be inserted. The rod-shaped carrier element serves as a carrier for a magnetic sensor, which is provided as a limit switch. By the rod-shaped support member, a thin signal cable extends to the magnetic sensor.

The Japanese Utility Model JP S58-137695 U shows a support cylinder for a work machine. On the underside of the piston, on which the formed in the manner of a piston rod, internally hollow support base is supported, a sensor is arranged. A connecting line hangs freely from the bottom of the cylinder through the piston into the support foot leading and telescopically in this insertable inner tube into the fetch support leg and leads to the sensor.

It is an object of the present invention to provide an improved cylinder / piston assembly, which enables a reliable and trouble-free signal transmission from the end of the piston rod to the opposite end of the hydraulic cylinder.

These and other objects are achieved by the features of claim 1. Advantageous embodiments can be found in the dependent claims.

According to the invention, in a cylinder / piston unit of the type mentioned above, an inner tube extending through the cylinder space is provided, which protrudes into the at least partially hollow piston rod via a bore in the piston and can be pushed telescopically into it. Here, the inner tube on the piston and / or the hollow piston rod against the cylinder chamber sealed and forms together with the hollow piston rod a hydraulic fluid-free interior through which a signal transmission can take place. In addition, a sensor is arranged at the distal end of the piston rod, in particular a force sensor which generates a support force-dependent signal, which is transmitted through the hydraulic fluid-free interior.

The hydraulic fluid-filled cylinder space is thus formed by the annular space surrounding the inner tube. Accordingly, the piston is annular and sealed against both the cylinder inner wall and the inner tube. Instead of an outer piston ring for sealing the piston relative to the cylinder inner wall piston and piston rod can of course also be designed as a so-called plunger and sealed by means of a so-called stuffing box seal on the cylinder head.

In a particularly preferred embodiment of the present invention extends through the hydraulic fluid-free interior a wireless signal transmission path. By the inner tube such a wireless transmission path is well protected against external interference and thus enables secure data transmission through the cylinder / piston unit through. The wireless signal transmission path can be designed, for example, as an optical free-space transmission path, in particular an infrared transmission path. As such, it is simple and inexpensive to implement.

While a cable connection and also a connection via sliding contacts is susceptible to signal interruptions, for example caused by cable breakage due to material fatigue due to frequent disassembly and contraction, or due to contact difficulties of the sliding contacts, for example due to corrosion or wear of the sliding contacts, is a wireless transmission in the hydraulic fluid-free interior safely protected against signal loss. Also, the risk of a short circuit caused by fatigue is reduced. In addition, a multi-channel signal transmission can be achieved by a simple modulation, which is much easier than to install several sliding contacts in the piston rod. Besides, one is Wireless connection compared to sliding contacts associated with less technical effort.

Additionally or alternatively, an electrical line can be laid by the hydraulic fluid-free interior. This is preferably designed so that the length of the electrical line automatically adapts to the stroke of the piston. This can preferably be realized by means of a spiral cable. Such an electrical line can in principle also serve for data transmission through the cylinder / piston unit, but in combination with a wireless signal transmission path, the electrical line can be used as a pure electrical supply line for supplying power to an electrical circuit arranged at the distal end of the piston rod. For example, a transmitter / receiver and / or a sensor with associated control circuit, be formed.

As an alternative to a running through the hydraulic fluid-free interior electrical supply line and means for wireless energy transfer to a arranged at the end of the piston rod electrical circuit, for example, a transmitter / receiver and / or a sensor, each with associated control circuit, are provided.

In a preferred embodiment, the cylinder / piston assembly is used in a hydraulic support of a mobile work machine and allows monitoring of the support forces transmitted via the support. In this case, it is particularly advantageous if the sensor and an associated control circuit, in particular a microcontroller, are supplied with operating voltage via an electrical supply line extending through the hydraulic medium-free interior, or alternatively wirelessly. Thus, no unprotected running outside the support electrical lines are needed and sensor and control circuit are well protected against external influences and damage.

In particular, the present invention also relates to a hydraulic support for supporting work machines, with a cylinder / piston unit of the type mentioned above. At the end of the piston rod here a Stützfußfuß is arranged, wherein in the column base or the piston rod, a force sensor for determining the support acting supporting forces is integrated. The force sensor can be read out via the hydraulic fluid-free interior.

Figur 1

eine schematische Ansicht eines Kranfahrzeugs mit seitlichen Stützauslegern und hydraulischen Stützen, bei dem die vorliegende Erfindung zum Einsatz kommt,

Figur 2

einen Längsschnitt durch ein Zylinder/Kolben-Aggregat und

Figur 3

ein Blockschaltbild einer Infrarotübertragungsstrecke.

Further advantages and features of the present invention will become apparent from the description of the following embodiments with reference to the figures; showing:

FIG. 1

a schematic view of a crane vehicle with lateral support arms and hydraulic supports, in which the present invention is used,

FIG. 2

a longitudinal section through a cylinder / piston unit and

FIG. 3

a block diagram of an infrared transmission path.

This in FIG. 1 schematically shown crane vehicle has laterally extended support arm 1, at the free end of each a hydraulic support is arranged. The vertically extending hydraulic support comprises a hydraulic cylinder 2 with a downwardly directed piston rod 3, at whose lower end a joint head 5 is arranged. Within the piston rod 3, a force sensor 4 is integrated above the joint head 5, with the aid of which a proportional to a supporting force or at least dependent on a supporting force measuring signal can be generated. Such a force sensor is often referred to as a force transducer. The condyle 5 forms a ball-jointed connection to a support leg 6, in that the condyle 5 is received by a socket formed on the support leg 6.

The support arms 1 are laterally extendable or swung out in a conventional manner, so that the crane vehicle can be supported laterally by extending the hydraulic cylinders 2 when the support arms are extended or swiveled out. For transport, however, the support arms are pushed or pivoted into a transport position.

The force sensor 4 integrated into the end of the piston rod 3 can be arranged, for example, within a receiving bushing formed on the lower end of the piston rod 3, into which a journal movable in the bushing is inserted "floating", at the lower end of which the condyle 5 is located. Such an embodiment is for example in the patent application DE 10 2016 104 502 the applicant, to which reference is made in order to avoid unnecessary repetition.

It is essential in the context of the present invention that measured values of the force sensor 4 are transmitted through piston rod 3 and hydraulic cylinder 2 to an evaluation device arranged on the support arm 1 or inside the crane vehicle, at least remote from piston rod end and support leg 6, respectively. In one aspect According to the present invention, the transmission of the measured values from the force sensor 4 is effected by a hydraulic medium-free interior, which is formed by the piston rod 3, which is hollow at least in sections for this purpose, and an inner tube 8 which can be inserted telescopically and penetrates the cylinder space in the longitudinal direction.

An embodiment of such a cylinder / piston unit with hydraulic fluid-free interior is in FIG. 2 shown in a longitudinal section. The cylinder / piston unit comprises a hydraulic cylinder 2, in whose hydraulic fluid-filled cylinder space a longitudinally movable piston 7 is arranged in this. The piston 7 is sealed via one or more outer piston rings (not shown) with respect to the inner wall of the hydraulic cylinder in a conventional manner. On the piston 7, the downwardly facing piston rod 3 is arranged and protrudes on the cylinder head via a corresponding bottom opening in the hydraulic cylinder 2, which may also be provided with a hydraulic seal and / or scrapers, out of this down. By pressurization or supply of hydraulic fluid in the hydraulic chamber above the piston 7, the piston rod 3 is extended, retracted by discharging hydraulic fluid from the upper hydraulic chamber or supplying hydraulic fluid into the hydraulic chamber below the piston 7 again.

The piston rod 3 is partially, namely provided by the arranged at its lower end force sensor 4 to the piston 7 with a central longitudinal bore 3 ', which also extends through the piston 7 in the longitudinal direction. In other words, the piston rod 3 is hollow inside. In the interior of the hydraulic cylinder 2, a centrally extending along its longitudinal axis inner tube 8 is also arranged, which protrudes telescopically into the central longitudinal bore 7 'in the piston 7 and further into the central longitudinal bore 3' of the piston rod 3. Opposite the longitudinal bore 7 'and the piston 7, the inner tube 8 is sealingly sealed via a hydraulic seal 9 inserted in the piston 7, for example an inner piston ring. The inner tube 8 is thus inserted telescopically into the hollow piston rod 3 when the piston 7 retracts.

At the upper end of the hydraulic cylinder 2, the inner tube 8 is guided via a corresponding bore to the outside and secured there. A seal 10 seals the connection between the inner tube 8 and the outlet bore at the upper end of the hydraulic cylinder. The longitudinal bores 3 ', 7' by piston 7 and piston rod 3 together with the telescopically insertable inner tube 8 into this hydraulic fluid-free, compared to the hydraulic chamber of the hydraulic cylinder 2 fluidically sealed interior, are transmitted by the measuring signals of the force sensor 4.

In the embodiment runs through the hydraulic means-free interior an infrared transmission path, which is formed by an infrared transmitter 20, an infrared receiver 21, a transmitter-side control circuit 22 and a receiver-side control circuit 23. The power supply for the arranged at the lower end of the piston rod 3 force sensor 4, the infrared transmitter 20 and the associated control circuit 22 via a likewise guided through the hydraulic fluid-free interior spiral cable 11, which serves as a supply line. At the upper end of the inner tube 8, a connected to the spiral cable 11 terminal 12, which is connected to a power source, and connected to the receiver-side control circuit 23 signal terminal 13 for the measurement signals of the force sensor 4 from. The signal terminal 13 is connected directly or via further circuit parts with an evaluation device, while the power connector 12 is connected as mentioned with a power source.

Instead of a run through the hydraulic fluid-free interior supply line 11 can of course also a self-sufficient power supply by means of battery o.ä. be provided. Another possibility is to provide wireless energy transfer. Such an energy transmission path comprises a (micro) wave generator coupled to a transmitter in the column base 6. On the side of the sensor 4 and the associated control circuit 22, a microwave receiver and a rectifier are provided, which the transmit converted microwave energy into a DC voltage for the supply of sensor 4 and control circuit 22.

A block diagram of an infrared transmission path, as used in the interior of the hydraulic fluid-free interior, is shown schematically in FIG FIG. 3 shown. That from the sensor 4 FIG. 2 The upcoming load-bearing-dependent analog measurement signal is applied to the input of an analog-to-digital converter 22a. The digital outputs of the analog-to-digital converter 22a are connected to a transmission-side control circuit 22b, to which an infrared transmitter 20, for example in the form of an infrared light-emitting diode, is connected. The transmitter-side control circuit 22b converts the digital signals coming from the analog-to-digital converter 22a into digital communication signals, which are transmitted from the infrared transmitter 20 in the form of short light pulses via the free space transmission path 24 to an infrared receiver 21.

The infrared receiver 21, for example in the form of an infrared-sensitive photodiode, is connected to a receiver-side control circuit 23a, which evaluates the light pulses received from the infrared receiver 21 and converted into electrical signals on the basis of the transmission protocol used and extracts the transmitted digital data representing the measurement signal of the force sensor 4 , These can then optionally be given via a corresponding digital output of the receiver-side control circuit 23a to a digital-to-analog converter 23b, which again generates an analog measurement signal which corresponds to the measurement signal originally output by the force sensor 4. Alternatively, of course, the digitized measurement signal can also be output on the data line 13 at the upper end of the hydraulic cylinder 2 for further processing in an evaluation device, or the signal can be converted into various other types of digital signals.

As an alternative to an infrared transmission path as explained above, other optical free-space transmission methods can also be used, for example in the visible Spectral range, are used. In addition, other wireless signal transmission methods, such as a high-frequency range short-range radio transmission conceivable. An acoustic signal transmission through the hydraulic means-free interior, for example in the ultrasonic range is possible in the context of the present invention.

In the exemplary embodiment, the signal transmission between the sensor 4 and the evaluation device takes place unidirectionally, so that only measured values of the sensor 4 can be transmitted to the evaluation device. However, bidirectional signal transmission is also possible and included within the scope of the present invention, so that control commands and acknowledgments can also be transmitted to the sensor 4 and its associated control circuit 22. In this case, a transmitter and receiver with associated control circuits would be arranged on both the side of the sensor 4 and on the far side of the hydraulic cylinder.

A duplex transmission path has the advantage that this can be ensured by means of an 'acknowledgment function' a complete or error-free transmission. An example of such an acknowledgment function would be the following communication: The transmitter sends out signals in the form of a data packet (e.g., value: 12345, binary value: 011000000111001, number of bits sent: 15). After the signal has been received, the receiver sends back a signal to the transmitter and determines how many bits (here: 15) were received. The transmitter checks if all values (15 bits) have been completely transmitted. If so, the sender sends the next signal, if not, the erroneously received packet is resent.

In the context of the present embodiment, the spiral cable 11, which is also guided by the hydraulic fluid-free interior of the cylinder / piston unit, only the power supply of sensor 4 and control circuit 22. The wireless signal transmission of the measuring signals by the hydraulic fluid-free interior of the cylinder / piston unit however, ensures a particularly robust and trouble-free readout of the sensor 4, as well as a galvanic decoupling of the following evaluation on board the crane vehicle from the burdening on the ground pillar foot 6. Alternatively to a wireless signal transmission is of course in addition to a wired power supply and signal transmission through a corresponding extending through the hydraulic fluid-free interior signal line possible and in Within the scope of the present invention.

As a force sensor 4, for example, a load cell can be used. Such serves as a load cell for the measurement of compressive forces and can be formed for example by a spring body load cell with ring torsion spring. Here, a toroidal deformation body is disposed within the load cell, which is acted upon on its inner side with force and attached to its outer side on the thrust bearing of the load cell. Due to the load, the ring torsion spring undergoes a torsion, by which it is compressed at the top and stretched at the bottom. About strain gauges, which are attached to the top and bottom of the ring torsion spring, this deformation can be measured. In another design, the load cell can also be formed by a hollow body expansion cylinder. In addition to spring body force transducers with strain gauges, other types of force transducers, such as piezo force transducers or resistance force transducers, can be used in the context of the present invention.

A corresponding electrical circuit and evaluation device for reading the force transducer can either be arranged externally and be connected via appropriate, guided by the hydraulic fluid-free interior of the cylinder / piston unit electrical signal lines to the force transducer or alternatively be located above the force transducer in an overlying receiving space.

A cylinder / piston assembly of the type described above can be used as a support member in all types of work machines, especially in mobile work equipment where support is required.

Claims (9)

1. Cylinder/piston unit especially for a support, comprising a hydraulic cylinder (2) having a cylinder chamber and, movable longitudinally therein, a piston (7) which carries a piston rod (3), the piston rod (3) being at least partly hollow, wherein an internal pipe (8) running through the cylinder chamber is provided, which internal pipe projects through a bore (7') in the piston (7) into the at least partly hollow piston rod (3) and can be pushed telescopically into the latter, and wherein the internal pipe (8), at the piston (7) and/or the hollow piston rod (3), is sealed with respect to the cylinder chamber and forms therewith an internal chamber that is free of hydraulic medium,
   characterised in that
   at the remote end of the piston rod (3) there is arranged a sensor (4), especially a force sensor, which generates a support-force-dependent signal which is transmitted through the hydraulic-medium-free internal chamber.
2. Cylinder/piston unit according to claim 1, wherein a wireless signal transmission path (24) runs through the hydraulic-medium-free internal chamber.
3. Cylinder/piston unit according to claim 2, wherein the signal transmission path (24) is in the form of an optical free-space transmission path, especially an infrared transmission path.
4. Cylinder/piston unit according any one of the preceding claims, wherein an electrical line (11) runs through the hydraulic-medium-free internal chamber.
5. Cylinder/piston unit according to claim 4, wherein the electrical line is in the form of a helix cable.
6. Cylinder/piston unit according to claim 4 or 5, wherein the electrical line is a pure electrical supply line.
7. Cylinder/piston unit according to any one of claims 1 to 3, wherein means are provided for wireless energy transmission to an electrical circuit (4, 22) arranged at the end of the piston rod (3).
8. Cylinder/piston unit according to claim 7, wherein the sensor (4) and an associated control circuit (22), especially a microcontroller, are supplied with operating voltage via an electrical supply line (11) running through the hydraulic-medium-free internal chamber.
9. Hydraulic support for supporting work machines, having a cylinder/piston unit according to any one of the preceding claims, a support foot (6) arranged at the end of the piston rod and having a force sensor (4) integrated in the support foot (6) or piston rod (3) to determine support forces acting on the support (2, 3), wherein the force sensor (4) is readable via the hydraulic-medium-free internal chamber.

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