DE20120649U1 - Device for closing a pot-shaped digestion container - Google Patents

Description

MLS GmbH
P26051DE

Device for closing a pot-shaped digestion container

The invention relates to a device according to the preamble claim 1 or 7.

In order to carry out an analysis of substances, it is known to heat one or more substances, e.g. a solid or liquid sample material, in a digestion vessel, which in most digestion cases creates an overpressure in the digestion vessel, which in turn promotes the digestion of the sample material or the like.

A device of the type specified in the preamble of claim 1 is described in EP 0 830 891 A1. In this generic design, an elastic pressure medium acting between a screw part and a pressure stamp is formed by a stack of metal disc springs arranged one above the other, the pressure stamp being formed as a U-shaped component in which a dome-shaped cage part is arranged, which consists of metal and forms a Faraday cage for the disc springs. This device is multi-part and of a large, in particular high, construction, so that the disadvantages described above also apply to it.

A device for closing a pot-shaped digestion container according to the preamble of claim 7 is described in GB 2 184 040 A. In this known device, the pressure stamp, the screw part and the elastic pressure medium arranged between them are accommodated in a hat-shaped screw lid of a pot-shaped support container in which a receiving container is suitably inserted, against whose lid the pressure stamp acts. The screw part is guided vertically displaceably with a pressure piece in a vertical guide hole in the screw lid and is designed as a nut which is screwed onto a pressure piece extending coaxially upwards from the pressure stamp in a threaded shaft which passes through a guide hole. In the ring wall of the hat-shaped screw lid, when screwed on, an inner ring groove is arranged at the height of the upper edge of the support container, from which a vent channel extends radially outwards through the ring wall. The known design is multi-part, of large construction, complex to manufacture and time-consuming to handle. There is also a risk that the pressure piece and the nut will move apart due to contamination, for example, resulting in different pressure ranges when opening and closing the lid of the receiving container.

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The invention is based on the object of simplifying a device of the types specified at the outset and designing it in such a way that a small or low construction is achieved. In addition, the device is to be improved in terms of its function. In addition, the aim is to reduce the number of individual parts of the device and the material required for them.

This object is solved by the features of claim 1 or 7. Advantageous developments of the invention are described in the subclaims.

In the device according to the invention according to claim 1, the pressure stamp and the screw part overlap each other in a sleeve-like manner with at least one ring wall, which can be part of the pressure stamp, which preferably extends upwards in one piece from the latter and overlaps the screw part in a sleeve-like manner, or which can be part of the screw part, which preferably extends downwards in one piece from the latter and overlaps the pressure stamp in a sleeve-like manner. It is also possible for two peripheral walls to be provided, of which one ring wall extends upwards from the pressure stamp and the other ring wall extends downwards from the screw part and the ring walls overlap each other in a sleeve-like manner. This not only provides guidance and/or radial support for the pressure stamp, but the interior space between the pressure stamp and the screw part that accommodates the elastic pressure medium is closed by the at least one ring wall, so that neither contaminants from the receiving space of the receiving container in the event of an overpressure reaction that lifts the lid of the receiving container nor other contaminants from the environment of the device can get into the interior space for the elastic pressure medium. This also protects the interior from aggressive treatment or decomposition chemicals, which protects the movement function of the device and ensures a long service life. A thread guide is a forced guide in both axial directions of movement, which leads to a safe adjustment of the screw part even if there is a certain stiffness in the guide.

The seal between the pressure stamp and the screw part can be improved by arranging a seal between the sleeve-like cooperating guide surfaces, preferably a ring seal, which can be an O-ring, for example, which can be inserted in an outer ring groove of the overlapping part or in an inner ring groove of the overlapping part.

Within the scope of the invention, there are many possibilities for supporting the screw part on an abutment. Such an abutment can be formed, for example, by a supported disk that covers a stand for the digestion container in a space that can be exposed to microwaves. If such a disk is open on all sides, it can also be used to cover several stands for digestion containers that are distributed around the circumference with the device. In this case, the disk can be a turntable in a manner known per se, which is mounted so that it can rotate with the stands in the microwave space.

The abutment can also be formed by the ceiling wall of a pressure-absorbing body that delimits a stand for a digestion vessel on both sides, from the bottom and the top. With this design, the digestion vessel can be placed on the stand with the device from one side and then removed again.

It is also possible according to claim 7 to form the abutment on the outer surface of the digestion tank or to support it thereon. For this purpose, the screw part can be formed by the top wall of a cap, the ring wall of which can be connected to the digestion tank in its free edge area, e.g. by screws. In this case, it is particularly advantageous if a screw ring with an external thread is placed on the outer surface of the digestion tank and is supported on it, preferably on the underside of a flange in the edge area of the digestion tank, so that the flange absorbs the support forces of the device and ensures that the screw ring is positioned by contact. This design is particularly characterized by a small design that takes up little installation space, is handy, uses little material and is also lightweight.

It is possible and advantageous in all designs to arrange a marking or a scale between the screw part or attachments thereof and the abutment so that the screw part can be pre-set in stages or continuously with respect to the elastic closing force of the pressure medium so that a certain opening pressure is reached, when this pressure is exceeded in the digestion chamber of the digestion vessel, the lid of the digestion vessel automatically lifts off and thus opens. This allows the operator to predetermine the desired maximum internal pressure in the receiving chamber of the receiving vessel, taking into account the substance or substances to be treated.

Advantageous embodiments of the invention are explained in more detail below using several exemplary embodiments and drawings. It shows

Fig. 1 shows a container arrangement with a device according to the invention for

Closing a digestion vessel in vertical section;

Fig. 2 the detail marked X in Fig. 1 in an enlarged

Depiction;

Fig. 3 shows a modified container arrangement with a likewise modified

Device for closing a digestion vessel in vertical section.

A pot-shaped digestion vessel 1 with a hollow cylindrical and, for example, relatively thin peripheral wall la and a flat bottom wall 1b is surrounded by a hollow cylindrical support shell 2 and supported radially outwards, which can extend up to a flange 1c at the upper edge of the peripheral wall la, so that the flange 1c rests on the upper end face of the support shell 2.

The top opening of the decomposition vessel 1 can be closed and opened by a flat and stepped cylindrical lid 3, for example, which in the embodiment with a lower cylindrical lid attachment 3a fits into the decomposition vessel 1 with little play and is preferably sealed by an annular seal 4. This can be formed by an O-ring 4a, which sits in an annular groove in the outer surface of the lid attachment 3a. The lid 3 therefore rests with its shoulder surface 3b on the flange 1c.

The device designated as a whole with 5 for closing the digestion container 1 even when there is excess pressure in its digestion interior Id consists mainly of 3 parts, namely a pressure stamp 6, a screw part 7 arranged at least partially above it and an elastic pressure medium 8 which is arranged between an upwardly directed support surface 6a on the pressure stamp 6 and a downwardly directed support surface 7a on the screw part 7 and is prestressed with a certain compression force during functional operation. In the exemplary embodiment, the pressure medium 8 consists of several disc springs stacked in opposite directions. The screw part 7 has an external thread 7b at least in its upper area, with which it is screwed into a threaded hole 9a of an abutment 9 as a screw part. In order to rotate the screw part 7, a rotary engagement element 11 is arranged on its upper side for a positively locking

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A rotary tool that can be brought into the rotary connection is arranged. In the exemplary embodiment, the rotary engagement element 11 is formed by a non-circular plug-in recess.

In order to cover the space 12 occupied by the pressure medium and thus protect it from contamination, an annular wall 7c is provided which surrounds the space 12 and by means of which the pressure stamp 6 and/or the screw part 7 are at least partially overlapped in a sleeve-like manner. In the exemplary embodiment, the preferably hollow-cylindrical annular wall 7c extends in one piece from the screw part 7 downwards, at least partially overlapping the preferably cylindrical peripheral surface of the pressure stamp 6 with play for movement, whereby the space 12 is inaccessible from the side.

The vertical overlap dimension a can be dimensioned so large that a guide function between the pressure stamp 6 and the screw part 7 and/or a ring seal 13 is ensured during the telescoping of the device 5, which is yet to be described. A sealing ring 13a is preferably arranged in the overlap gap, e.g. an O-ring, which sits in an annular groove in the outer surface of the pressure stamp 6 and is covered by the inner surface of the ring wall 7c in every telescoping position. The vertically extending maximum telescoping dimension b is determined in the present embodiment by the distance of the ring wall 7c from the cover 3. In a design of the pressure stamp 6 with a flange 6b, which is shown in outline, the maximum telescoping dimension b is determined by the distance to the flange 6a. The flange 6b allows the pressure surface of the pressure stamp 6 acting against the cover 3 to be increased and the surface pressure effective during functional operation to be reduced.

The pressure medium 8 or the spring disks can be centered by the inner surface of the ring wall 7c. However, in order to avoid frictional wear between them during telescoping, the preferably ring-shaped pressure medium 8 is centered internally by a centering bolt 6c with little play, which in the embodiment extends in one piece from the pressure stamp 6 upwards and can dip into a guide hole 7d between the support surface 7a and the rotary engagement element 11 or end shortly before it, thereby creating an additional, but not absolutely necessary, guide for the pressure stamp 6.

Preferably coaxially arranged in the pressure stamp 6 is a through hole 14 which can be lined, for example, by an annular wall 15 which can have a flange at its lower end with which it can be countersunk in a recess in the pressure surface.

The ring wall 15 can be pressed into the pressure stamp 6 with a press fit for its axial fastening.

The hole 14 can be used to accommodate functional elements, such as sensor elements, which pass through the screw part 7 and are functionally connected to the associated control or regulating devices. For example, a temperature sensor can be provided which is inserted into the hole 14. A pressure measuring element can also be inserted into the hole 14, the vertical position or change in position of which when the cover 3 is lifted off serves as an indicator for the level of the internal pressure prevailing in the digestion chamber Id during functional operation.

In the embodiment according to Fig. 1, the abutment 9 is formed by the top wall 16a of a support housing 16, which can be box-shaped with an arched wall 16b and two side walls 16c and forms a front-open or horizontally continuous storage space 17 for the digestion container 1, into which the latter can be inserted and removed again from the relevant side. In the inserted state, the digestion container 1 rests with its flat bottom wall 1b in the embodiment on the bottom wall 16b of the support housing 16, whereby the former bottom wall 1b is supported against the internal pressure.

An intermediate disk 18 can be arranged between the bottom walls 16b and 16b, which preferably consists of heat-insulating material, e.g. plastic, in order to reduce the heat dissipation from the digestion container 1.

The ring wall 7c extending downwards from the screw part 7 enables a large vertical adjustment range for the screw part 7 due to the resulting relatively large length and thus its adaptation to digestion vessels 1 of different heights if the external thread 7b extends at least to the lower end region of the ring wall 7c or, for example, over its entire vertical length.
30

In order to prevent the pressure stamp 6 from falling out of its overlapping position with the screw part 7 when there is no digestion container 1 under the device 5, a limiting device 21 is provided between the pressure stamp 6 and the screw part 7 or the ring wall 7c, which limits the maximum extension movement of the pressure stamp 6 and in the embodiment is formed by a stop device with a stop element 22 in the lower end region of the ring wall 7c. The counter stop element is preferably formed by the sealing ring 13a, which projects radially slightly beyond the outer surface of the pressure stamp 6 and thus forms the counter stop element 22.

can be done without the need for a special counter-stop element. The sealing ring 13a therefore fulfils both a sealing and a stop function. The stop element 21 is formed by an inner annular bead on the inner surface of the ring wall 7c. The diameter of the annular bead is larger than the diameter of the pressure stamp 6, taking into account a small amount of movement 5 or sliding play, which ensures that it can be moved in the annular bead. The inner diameter d2 of the annular bead is slightly larger than the remaining inner diameter dl of the ring wall 7c, which allows the inner bead to be formed. The inner diameter d2 is only large enough for the sealing ring 13a to form an elastic seal against the inner surface 7e of the ring wall 7c. In the exemplary embodiment, the outer flank of the stop element 22 or annular bead is formed by an inclined or rounded introduction surface 23. The inner flank 24 is a stepped surface that preferably extends approximately at a right angle to the center axis of the pressure stamp 6. In the embodiment, the inner annular bead is pointed in cross-section, so that a pointed annular edge is produced. As a result, the sealing ring 13a is sheared off when the pressure stamp 6 is forcibly pulled out of its socket connection and, taking into account the damage to the sealing ring 13a, dismantling protection is created.

In the embodiment according to Fig. 3, in which identical or comparable parts are provided with identical reference numerals, the screw part 7 with its ring wall 7c is designed to be so large that it covers the digestion container 1 in a cap-like manner at least in its upper edge region and is screwed to it, so that the peripheral wall 1a or the flange 1c or a possibly present support casing 2, to which the ring wall 7c can be screwed, forms the abutment 9. In the embodiment, a support ring 25 is placed on the digestion container 1, preferably in the upper region of the digestion container 1, in particular arranged in contact with the flange 1c and connected to the outer casing surface of the digestion container 1, e.g. by pressing or gluing. Such a connection ensures that the abutment forces are introduced into the digestion container 1. If the support ring 25 rests against the flange 1c, a connection to the outer casing surface can be dispensed with, since the flange 1c absorbs the abutment forces. But even in this case it is advantageous to hold the support ring 25 captive on the digestion container 1, e.g. by gluing or pressing.

The screw connection between the screw part 7 and the support ring 25 preferably has an internal thread 7f in the end region of the ring wall 7c and a matching external thread on the support ring 25.

In both of the above-described embodiments, the pressure stamp 6 can form the lid 3, as shown in Fig. 3. In the embodiment according to Fig. 1, the cross sections of the pressure stamp 6 and the screw part 7 would have to be enlarged accordingly so that the pressure stamp 6 can form the lid 3. In addition, the hole 14 would have to end at a distance from the end of the pressure stamp 6 facing the digestion container 1.

In all embodiments, it is also possible to form the pressure stamp in a U-shaped cross section according to Fig. 3 and thus to provide it with a peripheral wall 6d which, due to its axial length, ensures that the pressure stamp 6 is guided in a way that prevents it from tipping over and can also ensure adequate sealing. It is also advantageous to arrange one or more grooves 6e in the outer surface of the peripheral wall 6d which are axially spaced from one another, which both improve the sealing and, taking into account different thermal expansions, avoid harmful stresses in the fit, especially when the material of the pressure stamp is relatively soft or flexible, especially at higher decomposition temperatures.

In the embodiment according to Fig. 3, the elastic pressure medium 8 is formed by a helical spring which is supported on the top wall of the screw part 7 and acts on the pressure stamp 6, here in the recess base.

In the embodiment according to Fig. 3, a centering bolt 6c can also be provided, which is preferably also circular in cross section and can be guided lengthwise or vertically with play in the guide hole 7d in the top wall of the cap-shaped screw part 7. The centering bolt 6c preferably has a flange at its lower end to reduce the surface pressure, on which the pressure medium 8 can rest.

In all embodiments, it is advantageous to apply a marking between the screw part 7 and a part positioned on the digestion container 1 or on the lid 3 or on the pressure stamp 6, which allows the axial position of the screw part 7 to be recognized with respect to the positioned part and preferably enables a defined presetting of the screw part 7. The marking can be formed, for example, by a scale and an index, each of which is located on one of the two comparative parts. In the embodiment according to Fig. 1, the marking 27 can be arranged, for example, on the upper sides of the screw part 7 and the abutment 9, preferably near or on the thread groove of the screw lock, e.g. as a ring scale on the top wall 16a and as an index on the screw part 7.

In the embodiment according to Fig. 3, the marking 27 can be formed, for example, by the front end of the centering bolt 6c and the lower or upper edge of the guide hole 7d. It is also possible to apply the markings or scale lines to the inner wall surface of the guide hole at axial distances from one another, which, with the free end of the centering bolt 6c, enable the position of the centering bolt 6c and thus also the opening or closing position of the pressure stamp 6 and, if applicable, also the cover to be recognized or read.

1, the digestion container 1 is made of a corrosion-resistant material, in particular plastic and preferably PTFE. The other parts of the digestion container 1, including the support housing 16, are preferably made of microwave-permeable material, preferably plastic. This can also apply to the device 5. In the exemplary embodiment, the spring or spring elements forming the elastic pressure medium 8 are made of metal, in particular spring steel or stainless steel. The screw part 7 can also be made of metal, e.g. stainless steel, where it acts as a Faraday cage with regard to the spring. The function is improved if the cage has a polished surface and its edges are rounded. In addition, it is advantageous to determine the dimensions of the cage, i.e.

The metal cage should be dimensioned to be of a certain thickness, i.e. its diameter and axial length, preferably between a quarter and a whole wavelength of the microwave radiation used. In addition, the surface of the metal cage can be coated with a material such as PTFE that is resistant to aggressive chemicals in order to prevent the metal surface from being attacked by the chemicals.

For a digestion process, a sample material is placed in the digestion container 1 and the digestion container 1 is closed with the device 5. The screw part 7 is screwed in (Fig. 1) or unscrewed (Fig. 3) so far that the elastic pressure medium 8 applies a closing force that corresponds to a certain internal pressure. If the internal pressure rises above a certain value or the set value during functional operation, the lid 3 or the pressure stamp 6 opens automatically, the pressure medium 8 gives way and the internal pressure can escape. The device 5 functions like a pressure relief valve, whereby the opening pressure can be adjusted by screwing in the screw part 7.

The embodiment according to Fig. 3, in which identical or comparable parts are provided with identical reference numerals, differs from the previously described embodiment with regard to several configurations.

·

On the one hand, the abutment 9 is not part of a support housing 16 that accommodates the entire digestion container 1, but rather a small cap-shaped support housing 22, which also directs the support forces into the digestion container 1, but only extends over the upper region of the digestion container 1, is supported directly or indirectly on this upper region and thus directs the support forces into this region of the digestion container 1. The connection directly or indirectly to the upper region of the digestion container 1 is made by a screw connection. A radial blow-off opening 7e is provided in the ring wall 7c above the flange 1c or the support ring 25. The bottom wall 1b of the preferably cylindrical receiving container 1 is preferably hemispherical, which ensures that the wall is evenly stressed.

Claims (17)

1. Device ( 5 ) for closing a pot-shaped digestion container ( 1 ), the opening of which is covered by a lid ( 3 ), with - a printing stamp ( 6 ), - a screw part ( 7 ) arranged coaxially to the pressure stamp ( 6 ), - and an elastic pressure means ( 8 ) arranged between the pressure stamp ( 6 ) and the screw part ( 7 ), characterized ,
that the screw part ( 7 ) and the pressure stamp ( 6 ) overlap each other in a sleeve-like manner. 2. Device according to claim 1, characterized in that an annular wall ( 7 c) extending from the screw part ( 7 ) overlaps the pressure stamp ( 6 ) and is preferably connected in one piece to the screw part ( 7 ). 3. Device according to claim 1 or 2, characterized in that an annular seal ( 13 ) is arranged between the annular wall ( 7 c) and the pressure stamp ( 6 ). 4. Device according to claim 3, characterized in that the ring seal ( 13 ) is formed by a sealing ring ( 13a ) made of elastic material, which sits in an annular groove in the inner surface of the ring wall ( 7c ) or in the outer surface of the pressure stamp ( 6 ). 5. Device according to one of the preceding claims, characterized in that the screw part ( 7 ) has an external thread ( 7b ). 6. Device according to claim 5, characterized in that the screw part ( 7 ) is screwed or can be screwed into a stationary supported abutment ( 9 ), wherein a stand for the digestion container ( 1 ) is located under the screw part ( 7 ) and the pressure stamp ( 6 ), and wherein preferably the abutment ( 9 ) is formed by the top wall ( 16a ) of a box-shaped housing ( 16 ) having the stand. 7. Device ( 5 ) for closing a pot-shaped digestion container ( 1 ), the opening of which is covered by a lid ( 3 ), with - a printing stamp ( 6 ), - a screw part ( 7 ) which overlaps the pressure stamp ( 6 ) in the form of a cap and which has a screw thread in its lower edge region with which it can be screwed to an abutment ( 9 ) which surrounds the decomposition container ( 1 ), characterized,
that the abutment ( 9 ) is formed by a support ring ( 25 ) which is fixed to the circumference of the digestion vessel ( 1 ). 8. Device according to claim 7, characterized in that the digestion container ( 1 ) has a flange ( 1c ) on its edge and the support ring ( 25 ) is fastened to the outer surface of the digestion container ( 1 ) and/or engages under the flange ( 1c ) and/or is formed on the flange ( 1c ). 9. Device according to one of the preceding claims, characterized in that the pressure stamp ( 6 ) is guided in an axially sliding manner with a cylindrical sliding surface on a hollow cylindrical sliding surface of the screw part ( 7 ). 10. Device according to claim 9, characterized in that one or more annular grooves ( 6e) having an axial distance from one another are arranged in the cylindrical sliding surface of the pressure stamp (6 ) . 11. Device according to one of the preceding claims, characterized in that the pressure stamp ( 6 ) has a U-shaped cross-sectional shape and the elastic pressure means ( 8 ) is arranged in the recess formed by the U-shaped cross-sectional shape. 12. Device according to one of the preceding claims, characterized in that the elastic pressure means ( 8 ) is formed by one or more disc springs stacked on top of one another or a coil spring. 13. Device according to one of the preceding claims, characterized in that a preferably coaxial hole ( 14 ) is arranged in the pressure stamp ( 6 ). 14. Device according to one of the preceding claims, characterized in that the screw part ( 7 ) has in its upper region a guide section ( 7d ) for an extension ( 6c ) extending in one piece from the pressure stamp ( 6 ) or arranged thereon. 15. Device according to one of the preceding claims, characterized in that the screw part ( 7 ) has a rotary engagement element at its upper end, e.g. a non-circular recess ( 11 ) open on the upper side for a rotary tool. 16. Device according to one of the preceding claims, characterized in that the pressure stamp ( 6 ) forms the cover ( 3 ). 17. Device according to one of the preceding claims, characterized in that a position marking, e.g. a scale and an index, is arranged between the screw part ( 7 ) and the abutment ( 9 ).