Safety device

Abstract

Safety device for protecting mobile work equipment which is exposed to mechanical stress during work processes against overload, comprising a piston-cylinder unit (10) which interacts with the respective work equipment and a hydropneumatic pressure accumulator which is connected to the piston-cylinder unit (10) in a fluid-conducting manner, characterized in that - the piston-cylinder unit (10) has at least two separate fluid chambers (16, 18), - the pressure accumulator has at least two further liquid chambers (20, 22) separated from one another and at least one energy storage chamber, in particular a gas chamber (24), separated therefrom, and - the respective fluid chamber (16, 18) of the piston-cylinder unit (10) is fluid-conductingly connected to the respective assignable further fluid chamber (20, 22) of the pressure accumulator.

Description

[0001] The invention relates to a safety device for protecting movable work equipment which is exposed to mechanical stress during work processes against overload, comprising a piston-cylinder unit which interacts with the respective work equipment and a hydropneumatic pressure accumulator which is connected to the piston-cylinder unit in a fluid-carrying manner.

[0002] When operating crushing systems such as roller, jaw, impact, and cone crushers or mills, there is a risk that the material to be crushed may contain hard foreign materials, such as metal parts, which can cause damage or destruction due to excessive force impulses, such as impacts, acting on the tool in question. The same applies to agricultural tillage equipment such as plows, where overloading can occur when encountering obstacles such as rocks.

[0003] US 2007 / 0069053 A1 discloses an impact crushing plant with a drivable rotor located in a housing, which has crushing bars whose radius, together with an impact wall of the housing, defines the width of a crushing gap, wherein the impact wall is formed by an impact rocker that is movable to change the width of the crushing gap, wherein a safety device is provided which, in the event of a mechanical overload occurring during operation, allows a movement of the impact rocker that increases the width of the crushing gap, and wherein the safety device has a hydropneumatic piston-cylinder unit, the piston of which separates the oil side from a gas side and supports the impact rocker against the load, as well as a hydropneumatic pressure accumulator, the oil side of which is in fluid connection with the oil side of the piston-cylinder unit.

[0004] Based on this prior art, the invention seeks to further improve such safety devices, particularly to ensure trouble-free operation. This object is achieved by a safety device having the features of patent claim 1 in its entirety.

[0005] Because according to the characterizing part of patent claim 1 it is provided that - the piston-cylinder unit has at least two separate fluid chambers, - the pressure accumulator has at least two separate liquid chambers and at least one separate energy storage chamber, in particular a gas chamber, and - that the respective fluid chamber of the piston-cylinder unit is fluidly connected to the respective assignable further fluid chamber of the pressure accumulator, a closed, hydraulic system is created which enables rapid response of the safety device, in particular on its respective piston side, with simultaneous, desired, delayed return to an initial position under the effect of the energy storage chamber, in particular in the form of a gas chamber filled with nitrogen gas. The rod sides, both on the piston-cylinder unit side and on the differential piston accumulator side, are also fluidly connected, so that the respective rod sides can follow the movement on the respective piston side without hindrance. In particular, this prevents any vacuum effects on the rod side of the aforementioned devices that would disrupt movement, and cavitation is largely avoided.

[0006] In a preferred embodiment of the safety device according to the invention, the piston-cylinder unit is designed as a differential cylinder or as a synchronous cylinder. In the differential cylinder configuration, the rod-side volume can be different from the base or piston-side volume of the piston-cylinder unit. In the synchronous cylinder configuration, the volume is the same on both the piston and rod sides. This allows the safety device to be adapted to a wide variety of conditions.

[0007] In a further preferred embodiment of the safety device according to the invention, the pressure accumulator is designed as a differential piston accumulator, the rod side of which opens into the gas chamber containing a working gas, in particular nitrogen gas. Preferably, it is further provided that the liquid chamber on the piston side of the piston-cylinder unit is fluidly connected to the further liquid chamber on the piston side of the differential piston accumulator. Furthermore, it is advantageous if the liquid chamber on the rod side of the piston-cylinder unit is fluidly connected to the further liquid chamber on the rod side of the differential piston accumulator. The differential piston accumulator thus compensates for any change in the volume of both liquid chambers or oil chambers on the piston-cylinder unit side, which applies to both the piston side and the rod side.When an overload event occurs, the ratio of fluid outlet (oil out) to fluid inlet (oil in) is almost identical in the differential piston accumulator as in the piston-cylinder unit, resulting in unhindered operation for the safety device. Furthermore, when an overload event occurs, the safety device responds immediately and carries out a compensating process, for example, by controlling the piston-cylinder unit by moving an impact rocker in a baffle plate system to enlarge the crushing gap and prevent mechanical overloads caused by components of a corresponding size that are difficult or impossible to crush, such as metal parts. Overall, the aforementioned fluid or oil volume is therefore slightly compressed in the safety device, creating a slight negative pressure on the rod side of the device.The gas volume on the gas side of the differential piston accumulator acts as a damping "spring." Otherwise, the safety device operates in a force-balanced manner by uniformly shifting oil volumes.

[0008] In a further preferred embodiment of the safety device according to the invention, a third chamber, in particular a liquid chamber, is introduced between the liquid chambers on the piston side and the rod side of the piston-cylinder unit, through which the piston rod of the piston-cylinder unit passes. The third chamber is preferably provided with a liquid connection, which is preferably supplied with liquid via the piston rod. In this way, due to the third liquid chamber or oil chamber on the piston-cylinder unit, a so-called "zero point adjustment" is possible, i.e. the safety device can be calibrated to an initial state from which it carries out the aforementioned compensating processes in both sides as the basic position.It has proven particularly advantageous that the respective fluid chambers of the piston-cylinder unit and the differential piston accumulator contain a hydraulic medium as the fluid, such as largely incompressible hydraulic oil.

[0009] In a further preferred embodiment of the safety device according to the invention, a valve block with a throttle function is inserted into the respective fluid connection between the piston and rod sides of the piston-cylinder unit and the differential piston accumulator. This results in a throttled expulsion of fluid from the piston side of the differential piston accumulator to the piston side of the piston-cylinder unit. Likewise, a correspondingly throttled flow occurs in the opposite direction from the rod side of the piston-cylinder unit to the rod side of the differential piston accumulator. In the respective opposite flow direction, relating to the throttle function, the fluid flow can be completely released by opening a check valve.

[0010] In a further preferred embodiment of the safety device according to the invention, it is provided that a further valve block, each with a pressure relief valve for both the piston and rod sides, is provided in the respective fluid connection between the piston and rod sides of the piston-cylinder unit and the differential piston accumulator. This further valve block allows a predeterminable maximum operating pressure to be set on both the piston sides and the rod sides of the safety device. Particularly on the piston sides, such pressure relief can be released as needed by means of an electromagnetically controlled directional control valve. In the event of a control failure, the valve can also be manually operated using a button.

[0011] This safety device is explained in more detail using an exemplary embodiment shown in the drawing. The single figure shows the essential components of the safety device in a schematic and not-to-scale representation, similar to a hydraulic circuit diagram.

[0012] The safety device shown in the figure serves to protect movable work equipment exposed to mechanical stress during work processes against overload. For this purpose, the safety device comprises a piston-cylinder unit 10 that interacts with the respective work equipment (not shown). For this purpose, for example, the free end of the piston rod 12 engages a pivotably mounted impact arm of an impact crushing system, as shown by way of example in US 2007 / 0069053 A1, so this will not be discussed in further detail here.

[0013] Furthermore, the safety device comprises a hydropneumatic pressure accumulator in the form of a differential piston accumulator 14, which is fluidically connected to the piston-cylinder unit 10. For this purpose, the piston-cylinder unit 10 has at least two separate fluid chambers 16, 18. Likewise, the pressure accumulator in the form of the differential piston accumulator 14 has two separate, further fluid chambers 20, 22 and a separate energy storage chamber, in particular a gas chamber 24, which is filled with a working gas, such as nitrogen, in a predeterminable quantity and at a predeterminable gas pressure.

[0014] As can also be seen from the figure, the respective fluid chamber 16, 18 of the piston-cylinder unit 10 is fluid-conducting with the respective, assignable, further fluid chamber 20, 22 of the pressure accumulator 14 in fluid- or media-conducting connection. The piston-cylinder unit 10 can be designed as a differential cylinder, but also as a synchronous cylinder. In the present case, a differential cylinder is to be used for the piston-cylinder unit 10. The piston rod 12 is integrally connected to a piston 26, and the corresponding piston-rod unit 27 divides a cylinder housing 28 of the unit 10 into a piston side 30 and a rod side 32 with the respective fluid chambers 16 and 18, respectively.

[0015] The differential piston accumulator 14 also has a piston-rod unit 34, the piston rod 36 of which opens into the gas chamber 24 at its free end and thus on the rod side. To separate the gas chamber 24 from the adjacent liquid chamber 22, which is also penetrated by the piston rod 36 of the differential piston accumulator 14, a partition wall 40 inserted into an accumulator housing 38 is provided.

[0016] With this in mind, the fluid chamber 16 on the piston side 30 of the piston-cylinder unit 10 is fluidly connected, or connectable for operation, to the further fluid chamber 20 on the piston side 42 of the differential piston accumulator 14 via a connecting line 44. The piston side 42 of the differential piston accumulator 14 is bounded on one side by the piston 43 of the piston-rod unit 34 and on the other by wall sections of the accumulator housing 38.

[0017] Furthermore, the fluid chamber 18 on the rod side 32 of the piston-cylinder unit 10 is connected to the further fluid chamber 22 on the rod side 46 of the differential piston accumulator 14 via a further connecting line 48 in a media- or fluid-conducting manner, wherein the rod side 46 is delimited by the piston rod 36 as well as by the partition wall 40 and by the opposite end face of the piston 43 of the piston-rod unit 34. On the outer circumference side, the rod side 46 with the associated further fluid chamber 22 is delimited by wall parts of the accumulator housing 38.

[0018] The piston-cylinder unit 10 thus has a first fluid chamber 16 on the piston side and a second fluid chamber 18 on the rod side. The differential piston accumulator 14 accordingly has a third fluid chamber 20 on the piston side and a fourth fluid chamber 22 on the rod side. The volume released on the piston side in the first fluid chamber 16 of the piston-cylinder unit 10 can accordingly be absorbed by the third piston-side fluid chamber 20 of the differential piston accumulator 14.

[0019] The dimensions of the two mutually different piston-rod units 27 and 34 of the piston-cylinder unit 10 and the differential piston accumulator 14 are selected such that the fluid volume delivered in a rod-like manner into the fourth fluid chamber 22 of the differential piston accumulator 14 is slightly larger than the volume to be absorbed by the second rod-side fluid chamber 18 of the piston-cylinder unit 10. In particular, the volume delivered from the fourth fluid chamber 22 should be 1 to 15%, preferably 2 to 10%, particularly preferably 5 to 7% larger than the volume absorbed by the second rod-side fluid chamber 18 during operation of the safety device.

[0020] As can be further seen from the figure, a third fluid chamber 50 is provided between the fluid chambers 16, 18 on the piston side 30 and the rod side 32 of the piston-cylinder unit 10, which is penetrated by the piston rod 12 of the piston-cylinder unit 10 in the same way as the fluid chamber 18. Furthermore, the fluid chamber 50 is separated from the fluid chamber 18 on the rod side by a further partition wall 52, which, in a stationary manner, penetrates the cylinder housing 28 of the piston-cylinder unit 10. This third chamber 50 is provided with a fluid connection 54, which can preferably be supplied with fluid via the piston rod 12, for example, using an external extraction point 56.Depending on the fluid quantity in the third fluid chamber 50, a so-called zero-point adjustment for the piston-cylinder unit 10 can be initiated, i.e., a starting or basic position can be achieved from which the unit 10 can start; a position that corresponds to a starting position of the impact rocker of the impact crushing system.

[0021] The respective fluid chambers 16, 18, 20, 22, and 50 of the piston-cylinder unit 10 and the differential piston accumulator 14 contain a preferably largely incompressible medium, such as hydraulic oil, as the fluid. It is further understood that during operation of the safety device, the respective fluid chambers 16, 18, 20, 22, and 50, as well as the gas chamber 24, change in terms of their respective storage volume. For example, if the piston-rod unit 27 retracts to the right as viewed in the direction of the figure, the fluid volume on the piston side 30 is displaced into the fluid chamber 20 or onto the piston side 42 of the differential piston accumulator 14, so that the piston-rod unit 34 extends to the left against the effect of the gas pressure in the gas chamber 24, and its movement is dampened in the process.In this way, a safe, dampened force introduction is achieved through the safety device if the impact rocker suddenly causes a deflection force on the piston rod 12 to retract to the right, widening the crushing gap. Once the non-grindable material has successfully passed through the impact crusher and left the crushing gap, delimited by the impact rocker, the piston-rod unit 34 springs back under the action of the gas accumulator in the gas chamber 24, and a delayed, slow return of the piston-rod unit 27 to the left occurs, as the fluid located in the further fluid chamber 20 on the piston side 42 of the differential piston accumulator 14 returns to the piston side 30 of the unit 10.

[0022] As can also be seen from the figure, a valve block 58 with a throttle function, realized by an orifice or throttle 60, is inserted into the respective fluid connection in the form of the connecting lines 44, 48 between the piston sides 30, 42 and the rod sides 32, 46 of the piston-cylinder unit 10 and the differential piston accumulator 14. Running parallel to this, a check valve 62, 64 is connected in the supply line, which, on the one hand, opens the fluid path from the first connecting line 44 to the piston side 42 of the differential piston accumulator 14 and blocks it in the opposite direction; on the other hand, the further check valve 64 in the further valve block 58 blocks the fluid connection from the rod side 32 of the unit 10 to the rod side 46 of the piston accumulator 14 and opens the corresponding fluid path in the opposite flow direction.In the respective blocked direction of the check valve 62, 64, the fluid is then guided over the respective orifice 60 in the opposite flow direction.

[0023] Each valve block 58 can have relevant measuring points M, with the valve block 58 for the differential piston accumulator 14 being connected to its bottom side. Furthermore, each valve block 58 and the unit 10 can have a pressure safety plate 66 that protects the associated fluid circuit or valve block 58. Furthermore, it is possible to feed fluid from the outside via a central supply 68 via connection point A into the first connecting line 44 or via connection B into the further connecting line 48. Furthermore, the piston-rod units 34 and 27 of the differential piston accumulator 14 and the piston-cylinder unit 10 have position measuring devices 70 of conventional design, so that position monitoring can be achieved for both the unit 10 and the accumulator 14.

[0024] Furthermore, a further valve block 72 is connected to the connecting lines 44 and 48, which, as an additional valve block, has two pressure relief valves 74, 76. If the 2 / 2-way valve 78 of the additional valve block 72 is electromagnetically switched to its open position against the action of a return spring, which can also be done manually using a button if necessary, the first pressure relief valve 74 would open in the event of a predeterminable overpressure, for example of more than 50 bar, in the first connecting line 44 and release a pressure-reducing fluid path to tank T. Should a predeterminable overpressure occur on the rod sides 32 and 46, for example of more than 40 bar, the second pressure relief valve 76 switches and in turn releases the fluid path from the second connecting line 48 to tank T.

[0025] With the circuit diagram solution shown in the figure, using the described piston-cylinder unit 10 with the differential piston accumulator 14, an improved safety device is created that is particularly reliable for heavy-duty use in impact crushers, crushing mills, agricultural equipment, etc. This has no equivalent in the state of the art.

Claims

[1] Safety device for protecting mobile work equipment which is subjected to mechanical stress during work processes against overload, with a piston-cylinder unit (10) which interacts with the respective work equipment and with a hydropneumatic pressure accumulator which is connected to the piston-cylinder unit (10) in a fluid-carrying manner, characterized by , that - the piston-cylinder unit (10) has at least two separate fluid chambers (16, 18), - the pressure accumulator has at least two further liquid chambers (20, 22) separated from one another and at least one energy storage chamber, in particular a gas chamber (24), separated therefrom, and - the respective fluid chamber (16, 18) of the piston-cylinder unit (10) is fluid-conductingly connected to the respective assignable further fluid chamber (20, 22) of the pressure accumulator. [2] Safety device according to claim 1, characterized bythat the piston-cylinder unit (10) is designed as a differential cylinder or as a synchronous cylinder. [3] Safety device according to claim 1 or 2, characterized by that the pressure accumulator is designed as a differential piston accumulator (14), the piston rod (36) of which opens into the gas chamber (24) with a working gas, in particular nitrogen gas. [4] Safety device according to one of the preceding claims, characterized by that the fluid chamber (16) on the piston side (30) of the piston-cylinder unit (10) is fluid-conductingly connected to the further fluid chamber (20) on the piston side (42) of the differential piston accumulator (14). [5] Safety device according to one of the preceding claims, characterized by that the fluid chamber (18) on the rod side (32) of the piston-cylinder unit (10) is fluid-conductingly connected to the further fluid chamber (22) on the rod side (46) of the differential piston accumulator (14). [6] Safety device according to one of the preceding claims, characterized by , that - the volume delivered on the piston side in a first fluid chamber (16) of the piston-cylinder unit (10) can be absorbed by a third piston-side fluid chamber (20) in the differential piston accumulator (14) and - the dimensions of two different piston rod units (27, 34) of the piston-cylinder unit (10) or of the differential piston accumulator (14) are selected such that - the volume delivered on the rod side in a fourth fluid chamber (22) of the differential piston accumulator (14) is greater, in particular 1 to 15%, preferably 2 to 10%, particularly preferably 5 to 7%, than the volume to be absorbed by a second rod-side fluid chamber (18) of the piston-cylinder unit (10). [7] Safety device according to one of the preceding claims, characterized bythat between the liquid spaces (16, 18) on the piston side (30) and the rod side (32) of the piston-cylinder unit (10) a third space, in particular liquid space (50), is introduced, through which the piston rod (12) of the piston-cylinder unit (10) passes. [8] Safety device according to one of the preceding claims, characterized by that the third chamber (50) is provided with a liquid connection (54) which is preferably supplied with liquid via the piston rod (12). [9] Safety device according to one of the preceding claims, characterized by that the respective fluid spaces (16, 18, 20, 22, 50) of the piston-cylinder unit (10) and the differential piston accumulator (14) have a hydraulic medium, such as hydraulic oil, as the fluid. [10] Safety device according to one of the preceding claims, characterized bythat a valve block (58) with an orifice or throttle function (60) is inserted into the respective fluid connection (44, 48) between the pistons (30, 42) and the rod sides (32, 46) of the piston-cylinder unit (10) and the differential piston accumulator (14). [11] Safety device according to one of the preceding claims, characterized by that in the respective fluid connection (44, 48) between the piston (30, 42) and the rod sides (32, 46) of the piston-cylinder unit (10) and the differential piston accumulator (14) a further valve block (72) with a pressure relief valve (74, 76) is provided for both the piston (30, 42) and the rod side (32, 46).

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