The invention relates to a safety device for containers loaded by gas pressure, in particular the gas side of hydropneumatic devices such as hydraulic accumulators.
In order to ensure safety in the operation of devices with containers which contain a pressurized gas, such as, for example, hydraulic accumulators, potential risks which could arise at the installation site must be considered, especially also in conjunction with the possible occurrence of external effects. One important aspect that should be considered in this context is that a temperature increase which occurs in the event of an external fire at the installation site of the pertinent system should not lead to failure of the container.
In this respect, the object of the invention is to make available a safety device which ensures reliable protection of the gas side of pertinent devices against unacceptable pressure spikes caused by increased ambient temperatures.
This object is achieved according to the invention by a safety device having the features specified in claim 1 in its entirety.
One important feature of the invention accordingly consists in the fact that a means is integrated into a connecting device which is provided on the pressure chamber of the pertinent container and normally blocks a passage which runs between the gas side and the outside, but under the influence of temperature, the means can be transferred into a state which enables the clearance of a flow path through the passage and thus, in the event of a fire, ensures pressure relief. Because the device has a connecting part which is attached directly to the pressure chamber which is to be protected, the device responds to temperature elevations which occur directly on the pressure chamber which is to be protected so that high operational safety is ensured. Advantageously, the connecting device can be provided, for example, in a hydraulic accumulator on its fill port via which the gas side can be filled with the working gas.
The means which responds to the effect of temperature can especially advantageously be a solder of an alloy which has a desired melting point.
In exemplary embodiments which are characterized by an especially simple structure, the arrangement can be made such that the solder, located directly in the passage, forms a sealing plug which melts due to a temperature increase.
If, in this case, the passage on its end bordering the gas side runs axially and on the other end undergoes transition into exit channels which are perpendicular to the axial direction, the risk of damage to the vicinity by ejection of the entire amount of the solder forming the molten plug, with said ejection taking place in a straight line in the axial direction, is reduced.
As an alternative to using the solder as the sealing plug which directly blocks the passage, in alternative exemplary embodiments, the solder can also be provided as an element which controls a valve device. For example, the arrangement can be made such that the passage widens toward an axial section which borders the gas side, coaxially thereto, to form a hollow cylinder and that in the latter a valve piston is guided to be able to move axially which is secured by unmelted solder in a closed valve position which blocks the passage, and when the solder melts can be moved out of the closed position by the gas pressure into an open valve position to clear the flow path.
In other exemplary embodiments, on the end region of the passage facing away from the gas side, the connecting device can have a sealing cap which forms a spring housing in which a spring arrangement is held in a tensioned state by unmelted solder, where, when the solder melts, the spring arrangement by its spring force moves a control element which can be moved axially in the spring housing into a position which causes the flow path to be cleared.
In such exemplary embodiments, the blocking element of the passage can be a rupture disk which blocks it, and the control element which is pretensioned by the spring arrangement can have a mandrel which is moved by the spring force to pierce the rupture disk when the solder melts.
In one alternative exemplary embodiment which is actuated by spring force, the arrangement can be made such that the passage has a shutoff valve as a blocking element and that the control element pretensioned by the spring arrangement has a plunger by whose movement the shutoff valve can be forced into the clearance position when the solder melts.
The invention is detailed below using exemplary embodiments shown in the drawings.
FIG. 1 shows a longitudinal section of a hydropneumatic piston accumulator, provided with a safety device according to the exemplary embodiment of the invention shown in FIG. 3, which section is drawn schematically simplified;
FIG. 2 shows a longitudinal section of a first exemplary embodiment of the device according to the invention, shown enlarged roughly three times compared to a practical embodiment;
FIG. 3 shows a longitudinal section of a second exemplary embodiment of the device, drawn more highly enlarged compared to FIG. 2;
FIGS. 4 and 5 show longitudinal sections of a third and a fourth exemplary embodiment of the device, drawn on a somewhat smaller scale and schematically simplified compared to FIG. 3;
FIG. 6 shows a perspective oblique view of another exemplary embodiment which is shown schematically simplified, cut away lengthwise and on a still further enlarged scale, and
FIG. 7 shows a schematically simplified longitudinal section of a sixth exemplary embodiment of the device.
FIG. 1 shows a hydraulic accumulator 1 in the form of a piston accumulator of known design with a hollow cylindrical accumulator housing 3 which is closed by a bottom-side cover 5 and a head-side cover 7. In the manner which is conventional for these accumulators, a cup piston 9 which can be moved axially in the housing 3 separates an oil side 11 from a gas side 13. The oil side 11 can be connected to a hydraulic system, which is not shown, via an oil port 15 which is coaxial to the longitudinal axis 14. In the head-side cover 7, likewise coaxially to the longitudinal axis 14, there is a gas fill port 17 via which the gas side 13 can be supplied with a working gas, such as nitrogen, with a predetermined fill pressure.
In FIG. 1, the accumulator 1 is provided with an exemplary embodiment of the safety device according to the invention, specifically with the exemplary embodiment shown individually in FIG. 3, the safety device forming a connection device 19 which is screwed directly into the fill port 17 of the cover 7, so that the device directly borders the gas side 13 of the accumulator 1.
FIG. 2 shows a first exemplary embodiment in an individual representation. As is apparent, the connection device 19 has the form of a hollow screw with an external thread 21 which can be screwed into the fill port 17 and a hexagonal socket 23 which is located in the head of the screw. From the shaft end to the hexagonal socket 23, the screw is penetrated by a passage 25 which is coaxial to the longitudinal axis 14 and whose diameter is tapered in the longitudinal region adjacent to the hexagonal socket 23 relative to the remaining longitudinal region. In the passage 25, there is a solder 27 whose alloy is chosen such that the melting point is roughly in the range from 160° C. to 170° C. In the unmelted state, the solder 27 forms a sealing plug which blocks the passage 25 and which is additionally secured by its tapering site 29 against being pushed out of the passage 25 due to gas pressure. A temperature increase which may occur in a fire above the melting point of the solder 27 leads to the solder 27 being expelled to the outside and thus to the clearance of a flow path through the passage 25 to relieve the pressure in the container.
FIG. 3 shows the exemplary embodiment which has been modified compared to FIG. 2 and which is shown in FIG. 1 in its operating state connected to the accumulator 1. As in the example of FIG. 2, the connecting device 19 has the form of a screw which can be screwed directly into a gas fill port 17, with an inner passage 25 which on the end 31 bordering the gas side runs coaxially and on the other end undergoes transition into exit channels 33 which are perpendicular to the axial direction. As in the example of FIG. 2, in the passage 25, there is solder 27 as a sealing plug which is axially secured in addition at the transition site between the coaxial part of the passage 25 and the cross channels 33 which continue it. Only two cross channels 33 are visible in FIG. 3. In fact, there are a total of six channels 33 which are arranged in a star shape and which run in the radial direction. As FIG. 3 furthermore shows, the solder 27 as a sealing plug is supported on the face side by way of the housing wall of the connecting device 19; this yields an increased margin of safety compared to the solution as shown in FIG. 2, where the solder 27 on the free face side of the connecting device 19 can emerge directly into the open. To the extent that the connecting device 19 is addressed, it preferably forms a terminal plug for the fill opening of the hydraulic accumulator container.
The material for the solder 27 can be especially a soft solder which is readily available on the market under the commercial designation 178-190Gr.C-L-Sn62PbAg2-2.2. In particular for the solutions as shown in FIGS. 2 and 3, it is, however, also possible to make the solder 27 entirely as hard solder or to mix different types of solder with one another using material technology or to use them in combination with one another. For example, a bead of solder which faces toward the vicinity could consist of a more resistant hard solder material, whereas the inner solder part facing the accumulator could still be a soft solder material.
While in the example of FIG. 2 the melting solder 27 is expelled axially away from the pertinent container and can represent a risk to the vicinity, in the example of FIG. 3, the expulsion of molten solder takes place simply divided into partial amounts according to the number of channels 33, as is apparent from FIG. 1, the melt which is emerging in the transverse direction being captured by projecting walls of the accumulator housing 3 and being screened relative to the vicinity.
FIG. 4 shows a modified example with a connecting device 19 which can likewise be screwed directly into a pertinent fill port. The inner passage 25 on its end 31 bordering the gas side in turn has a first axial section 35 which undergoes transition into a widening which forms a hollow cylinder 37. In the vicinity of the base region of this hollow cylinder 37, the passage 25 continues with cross channels 39 which lead to the outside. In the axial section 35 and in the hollow cylinder 37, a valve piston 41 with periphery-side sealing is guided to be able to move axially, but is normally secured in the closed valve position shown in FIG. 4, and, in it, the periphery of the piston 41 seals at the cross channels 39 of the passage 25 by unmelted solder 27 which may be found between a cover part 43 which seals the hollow cylinder 37 and the bordering side of the piston 41. When the melting point of the solder 27 is reached, it emerges via lateral exit openings 45 so that the gas pressure moves the valve piston 41 out of the closed position shown in FIG. 4 and clears the flow path via the cross channels 39.
FIG. 5 shows an exemplary embodiment which is similar to FIG. 4 and in which unmelted solder 27 in turn secures a valve piston 41 in the closed position in which cross channels 39 of the passage 25 are blocked.
Unlike in the example of FIG. 4, however, in FIG. 5 the space between the valve piston 41 and the cover part 43 is not filled with solder, but the piston 41 is secured in the closed position shown in FIG. 5 by its being held to be axially immovable in a transition fit in an inner cylinder 47 made of an Al alloy. The inner cylinder 47 in turn is supported on the cover part 43. The transition fit between the inner cylinder 47 and the valve piston 41 is formed by a layer of solder 27 applied as a coating on the outer periphery of the piston 41 so that the transition fit is formed between the aluminum material of the cylinder 47 and the steel piston 41. If, when the temperature rises, the solder 27 melts and thus there is no longer any fit between the inner cylinder 47 and the valve piston 41, the latter is moved by the gas pressure into the clearance position so that the pressure drops via the cross channels 39.
In the example of FIG. 6, the connecting device 19 has a screw-on sealing cap 51 which forms a spring housing 53 in which a cup spring package 55 is clamped between the sealing cap 51 and a control element 57 which is supported against axial displacement on the solder 27 which forms a ring body. The control element 57 has a central mandrel 59 which extends through the ring opening of the solder 27 into the passage 25 and ends in a mandrel tip 61. The tip 61 is located at a short distance from a rupture disk 63 which is made of an austenitic material and which is located on the inner end of the passage 25. When the solder 27 melts, the tensioned cup spring package 55 drives the mandrel 59 in the direction of the rupture disk 63, which is pierced so that the pressure drops over the cross channels 39.
In the example as shown in FIG. 6, preferably in the case of failure, the solder 27 is displaced via the cross channel 39, but the main venting function is achieved via the axial holes shown in FIG. 6 within the control element 57 and the sealing cap 51.
In the example of FIG. 7, the screwed-on sealing cap 51 in turn forms a spring housing for a cup spring package 55 which, as in FIG. 6, is clamped between the sealing cap 51 and a control element 57 which can be moved longitudinally in the sealing cap 51, but which is supported via a layer of solder 27 which forms a ring body. Unlike in FIG. 6, the actual blocking element in the passage 25 is not a rupture disk, but a shutoff valve 65 which can be unblocked by the axial movement of an actuating plunger 67. The plunger 67 forms a central axial extension of the control element 57 and extends through the ring opening of the solder 27 in the direction of the shutoff valve 65 with which it interacts by unblocking when the control element 57 is moved axially by the pretensioning of the spring when the solder 27 melts. When the shutoff valve 65 has been opened in this way, the pressure in turn drops via cross channels 39. To the extent that reference is made in the specification to media-carrying bores, they can also be formed by other channels with any cross section.
Patent Application
20130082054
