Safety device against excess temperature

A safety apparatus is for containers loaded by gas pressure, in particular the gas side (13) of hydropneumatic devices such as hydraulic accumulators (1). The safety apparatus has a connection device (19) that can be attached to the pressure chamber of the container to form a passage (25) between the gas side (13) of the container and the outside. A structure (27) normally blocks the passage (25) and under the influence of temperature can be transferred into a state that allows a flow path through the passage (25) to be cleared.

FIELD OF THE INVENTION

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.

BACKGROUND OF THE INVENTION

In the operation of devices with containers that contain a pressurized gas, for example, hydraulic accumulators, potential risks could arise at the installation site that must be considered, especially in conjunction with the possible occurrence of external effects. One important aspect that should be considered in this context is that a temperature increase that occurs in the event of an external fire at the installation site of the pertinent system should not lead to failure of the container.

SUMMARY OF THE INVENTION

An object of the invention is to provide an improved safety device that ensures reliable protection of the gas side of pertinent devices against unacceptable pressure spikes caused by increased ambient temperatures.

This object is basically achieved according to the invention by a safety device having a structure integrated into a connecting device that is provided on the pressure chamber of the pertinent container and that normally blocks a passage extending between the gas side and the outside. Under the influence of temperature, the structure can be transferred into a state that clears a flow path through the passage. Thus, in the event of a fire, the connecting device ensures pressure relief. Because the device has a connecting part attached directly to the pressure chamber to be protected, the device responds to temperature elevations that occur directly on the pressure chamber 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 structure that responds to the effect of temperature can especially advantageously be a solder of an alloy having a desired melting point.

In exemplary embodiments characterized by an especially simple structure, the solder, located directly in the passage, forms a sealing plug that melts due to a temperature increase.

If the passage on its end bordering the gas side extends axially and on the other end undergoes transition into exit channels 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 the ejection taking place in a straight line in the axial direction, is reduced.

As an alternative to using the solder as the sealing plug that directly blocks the passage, in alternative exemplary embodiments, the solder can also be provided as an element that controls a valve device. For example, the passage can widen toward an axial section bordering the gas side, coaxially thereto, to form a hollow cylinder. In the hollow cylinder, a valve piston is guided for movement axially and is secured by unmelted solder in a closed valve position blocking the passage. When the solder melts, the valve piston 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 that forms a spring housing in which a spring arrangement is held in a tensioned state by unmelted solder. When the solder melts, the spring arrangement by its spring force moves a control element that can be moved axially in the spring housing into a position that causes the flow path to be cleared.

In such exemplary embodiments, the blocking element of the passage can be a rupture disk that blocks it. The control element is pretensioned by the spring arrangement and can have a mandrel that is moved by the spring force to pierce the rupture disk when the solder melts.

In one alternative exemplary embodiment that is actuated by spring force, the passage has a shutoff valve as a blocking element. 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.

Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a hydraulic accumulator1in the form of a piston accumulator of known design with a hollow cylindrical accumulator housing3closed by a bottom-side cover5and a head-side cover7. In the conventional manner for these accumulators, a cup piston9can be moved axially in the housing3and separates an oil side11from a gas side13. The oil side11can be connected to a hydraulic system (not shown), via an oil port15coaxial to the longitudinal axis14. In the head-side cover7, likewise coaxially to the longitudinal axis14, a gas fill port17is provided via which gas port the gas side13can be supplied with a working gas, such as nitrogen, with a predetermined fill pressure.

InFIG. 1, the accumulator1is provided with a first exemplary embodiment of the safety device according to the invention, with the first exemplary embodiment shown individually inFIG. 3. The safety device forms a connection device19screwed directly into the fill port17of the cover7, so that the device directly borders the gas side13of the accumulator1.

FIG. 2shows a second exemplary embodiment of the safety device in an individual representation. As is apparent, the connection device19has the form of a hollow screw with an external thread21that can be screwed into the fill port17and has a hexagonal socket23located in the head of the screw. From the shaft end to the hexagonal socket23, the screw is penetrated by a passage25that is coaxial to the longitudinal axis14and that has a diameter tapered in the longitudinal region adjacent to the hexagonal socket23relative to the remaining longitudinal region. In the passage25, a solder27with an alloy chosen such that the melting point is roughly in the range from 160° C. to 170° C. is located. In the unmelted state, the solder27forms a sealing plug that blocks the passage25and that is additionally secured by its tapering site29against being pushed out of the passage25due to gas pressure. A temperature increase that may occur in a fire above the melting point of the solder27leads to the solder27being expelled to the outside, and thus, to the clearance of a flow path through the passage25to relieve the pressure in the container.

FIG. 3shows the first exemplary embodiment of the safety device modified compared toFIG. 2and is shown inFIG. 1in its operating state connected to the accumulator1. As in the example ofFIG. 2, the connecting device19has the form of a screw that can be screwed directly into a gas fill port17, with an inner passage25. On the end31of the passage25bordering the gas side, the passage25extends coaxially. On the other end, passage25undergoes transition into exit channels33that are perpendicular to the axial direction. As in the example ofFIG. 2, in the passage25, solder27forms a sealing plug that is axially secured in addition at the transition site between the coaxial part of the passage25and the cross channels33that continue it. Only two cross channels33are visible inFIG. 3. In fact, a total of six channels33are arranged in a star shape and extend in the radial direction. AsFIG. 3furthermore shows, the solder27as a sealing plug is supported on the face side by the housing wall of the connecting device19. This arrangement yields an increased margin of safety compared to the solution as shown inFIG. 2, where the solder27on the free face side of the connecting device19can emerge directly into the open. To the extent that the connecting device19is addressed, it preferably forms a terminal plug for the fill opening of the hydraulic accumulator container.

The material for the solder27can be especially a soft solder that is readily available on the market under the commercial designation 178-190Gr.C-L-Sn62PbAg2-2.2. In particular for the solutions as shown inFIGS. 2 and 3, the solder27can be made 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 that faces toward the vicinity could be 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 ofFIG. 2the melting solder27is expelled axially away from the pertinent container and can represent a risk to the vicinity, in the example ofFIG. 3, the expulsion of molten solder takes place simply divided into partial amounts according to the number of channels33. As is apparent fromFIG. 1, the melt emerging in the transverse direction can be captured by projecting walls of the accumulator housing3and screened relative to the vicinity.

FIG. 4shows a modified example with a connecting device19that can likewise be screwed directly into a pertinent fill port. The inner passage25on its end31bordering the gas side in turn has a first axial section35that transitions into a widening forming a hollow cylinder37. In the vicinity of the base region of this hollow cylinder37, the passage25continues with cross channels39that lead to the outside. In the axial section35and in the hollow cylinder37, a valve piston41with periphery-side sealing is guided to be able to move axially, but is normally secured in the closed valve position shown inFIG. 4. In this closed valve position, the periphery of the piston41seals at the cross channels39of the passage25by unmelted solder27found between a cover part43that seals the hollow cylinder37and the bordering side of the piston41. When the melting point of the solder27is reached, solder27emerges via lateral exit openings45so that the gas pressure moves the valve piston41out of the closed position shown inFIG. 4and clears the flow path via the cross channels39.

FIG. 5shows an exemplary embodiment similar toFIG. 4in which unmelted solder27in turn secures a valve piston41in the closed position such that cross channels39of the passage25are blocked by valve piston41.

Unlike in the example ofFIG. 4, inFIG. 5the space between the valve piston41and the cover part43is not filled with solder. The piston41is secured in the closed position shown inFIG. 5by it being held to be axially immovable in a transition fit in an inner cylinder47made of an Al alloy. The inner cylinder47in turn is supported on the cover part43. The transition fit between the inner cylinder47and the valve piston41is formed by a layer of solder27applied as a coating on the outer periphery of the piston41so that the transition fit is formed between the aluminum material of the cylinder47and the steel piston41. When the temperature rises, the solder27melts, and thus, any fit no longer exists between the inner cylinder47and the valve piston41. The valve piston41then can move by the gas pressure into the clearance position so that the pressure drops via the cross channels39.

In the example ofFIG. 6, the connecting device19has a screw-on sealing cap51that forms a spring housing53in which a cup spring package55is clamped between the sealing cap51and a control element57that is supported against axial displacement on the unmelted solder27forming a ring body with a central or ring opening27a. The control element57has a central mandrel59that extends through the ring opening27aof the solder27into the passage25and ends in a mandrel tip61. The tip61is located at a short distance from a rupture disk63made of an austenitic material and located on the inner end of the passage25. The spring55, solder27and control device57are axially aligned in a wider axial portion of passage25in sealing cap51, with control device57being coaxially between unmelted solder27and spring55. When the solder27melts, the tensioned cup spring package55drives the mandrel59in the direction of the rupture disk63. Disk63is then pierced so that the pressure drops over the cross channels39.

In the example as shown inFIG. 6, preferably in the case of failure, the solder27is displaced via the cross channel39. The main venting function is achieved via the axial holes or openings57aspaced laterally outwardly from mandrel59, shown inFIG. 6, within the control element57, and vent opening or hole51ain the sealing cap51, respectively.

In the example ofFIG. 7, the screwed-on sealing cap51in turn forms a spring housing for a cup spring package55that, as inFIG. 6, is clamped between the sealing cap51and a control element57. Control element57can be moved longitudinally in the sealing cap51, but is supported via a layer of solder27forming a ring body. Unlike inFIG. 6, the actual blocking element in the passage25is not a rupture disk, but a shutoff valve65that can be unblocked by the axial movement of an actuating plunger67. The plunger67forms a central axial extension of the control element57and extends through the ring opening of the solder27in the direction of the shutoff valve65. Plunger67interacts with valve65and unblocks valve65when the control element57is moved axially by the pretensioning of the spring when the solder27melts. When the shutoff valve65is opened in this way, the pressure in turn drops via cross channels39.

To the extent that reference is made in the specification to media-carrying bores, such bores can also be formed by other channels with any cross section.