U.S. patent application number 10/316951 was filed with the patent office on 2003-07-10 for device for closing a pot-like digestion vessel.
This patent application is currently assigned to MILESTONE S.r.l.. Invention is credited to Lautenschlager, Werner.
Application Number | 20030127313 10/316951 |
Document ID | / |
Family ID | 27219640 |
Filed Date | 2003-07-10 |
United States Patent
Application |
20030127313 |
Kind Code |
A1 |
Lautenschlager, Werner |
July 10, 2003 |
Device for closing a pot-like digestion vessel
Abstract
A pot-like digestion vessel (1), which is closed by a cover (3),
is provided with adjustable automatic internal pressure relief by
means of a pressure applying plunger (6) which is held in a
screwing part (7) via a resilient pressure generating mans (8) to
press against the cover (3). In another embodiment the plunger (6)
holds a valve body (33) in an outlet channel (31) which extends
through the cover (3).
Inventors: |
Lautenschlager, Werner;
(Leutkirch, DE) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
MILESTONE S.r.l.
SORISOLE (BG)
IT
|
Family ID: |
27219640 |
Appl. No.: |
10/316951 |
Filed: |
December 12, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10316951 |
Dec 12, 2002 |
|
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|
10099443 |
Mar 15, 2002 |
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Current U.S.
Class: |
202/96 |
Current CPC
Class: |
B01J 3/03 20130101; B01J
2219/1209 20130101; G01N 1/44 20130101 |
Class at
Publication: |
202/96 |
International
Class: |
C10B 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2001 |
DE |
201 20 649.8 |
May 3, 2002 |
DE |
202 07 013.1 |
Claims
1. A device for closing a pot-like digestion vessel having an
opening which is covered by a cover, said device comprising a
pressure applying plunger; a screwing part arranged coaxially with
said pressure applying plunger; and a resilient pressure generating
means arranged between the pressure applying plunger and the
screwing part, said screwing part and said pressure-applying
plunger being configured such that one fits around the other in a
socketed arrangement.
2. A device according to claim 1, wherein an annular wall fits
around said pressure-applying plunger and is integrally connected
to said screwing part to extend from said screwing part.
3. A device according to claim 2, wherein an annular seal is
arranged between said annular wall and said pressure-applying
plunger.
4. A device according to claim 3, wherein said annular seal is
formed by a sealing ring of resilient material which is mounted in
an annular groove in the inner circumferential surface of said
annular wall or in an outer circumferential surface of said
pressure-applying plunger.
5. A device according to claim 1, wherein said screwing part has an
external thread.
6. A device according to claim 5, wherein said screwing part is
screwable into an abutment which is supported at a location such
that a digestion vessel is disposed below said screwing part and
said pressure-applying plunger, said abutment being formed by an
upper wall of a box-like housing for containing a digestion
vessel.
7. A device for closing a pot-like digestion vessel having an
opening which is covered by a cover, said device comprising: a
pressure-applying plunger; an abutment arranged to surround a
digestion vessel; and a screwing part which fits around said
pressure-applying plunger in the manner of a cap and which includes
a lower edge portion formed with a screw-thread and arranged such
said lower edge portion can be screwed to said abutment, said
abutment being formed by a supporting ring which can be fixed to a
digestion vessel at its circumference.
8. A device according to claim 7, and further including: a
digestion vessel having a flange at an edge thereof; said
supporting ring being fastened to an outer circumferential surface
of said digestion vessel and/or fits under the flange and/or is
formed on the flange.
9. A device according to claim 1, wherein said pressure-applying
plunger is axially guided by a cylindrical sliding face of an
internal hollow cylinder, which is formed in said screwing part, to
move slidingly along said face.
10. A device according to claim 9, wherein at least one annular
groove is formed in said cylindrical sliding face of said
pressure-applying plunger.
11. A device according to claim 1, wherein said pressure-applying
plunger has a U-shaped cross-sectional shape and wherein said
resilient pressure-generating means is arranged in a recess created
by said U-shaped cross-sectional shape.
12. A device according to clam 1, wherein said resilient
pressure-generating means is formed by at least one of a disc
spring and a helical spring.
13. A device according to claim 1, wherein a coaxial hole is formed
in said pressure-applying plunger
14. A device according to claim 1, wherein said screwing part
includes in an upper region thereof, a guidance section which
guides an extension of said pressure-applying plunger.
15. A device according to claim 1, wherein said screwing part is
provided at its upper end with an element for applying rotation
thereto.
16. A device according to claim 1, wherein said pressure-applying
plunger forms a cover of a digestion vessel.
17. A device according to claim 1, wherein a position-indicating
marking, is arranged between said screwing part and said
abutment.
18. A device for closing a pot-like digestion vessel, said device
comprising: a cover which closes an opening in such digestion
vessel; said cover being formed with an outlet channel extending
therethrough a closing part which bears against said cover to hold
said cover over an opening of a digestion vessel; a closing part
which bears against said cover; and a valve which closes said
outlet channel, said valve being arranged to open automatically in
response to an internal pressure in such digestion vessel exceeding
a given value.
19. A device according to claim 18, wherein said outlet channel is
disposed axially of said cover, and wherein said valve includes a
valve body which is larger than said outlet channel, said valve
body being preloaded by means of a spring against an edge of said
outlet channel.
20. A device according to claim 19, wherein said edge of said
outlet channel is formed by the step surface of a widened portion
of said outlet channel.
21. A device according to claim 20, wherein a section of said
outlet channel branches off inside said cover above said step
surface.
22. A device according claim 19, wherein said closing part is a
screwing part which is screwed into an abutment and which is also
arranged to be screwed against said cover.
23. A device according to claim 22, wherein said screwing part
forms a guide for said valve body.
24. A device according to claim 23, wherein said screwing part is a
sleeve into which said valve body extends.
25. A device according to claim 24, wherein said spring is arranged
in said sleeve.
26. A device according to claim 24 or 25, and further including a
stop arranged to limit outward extension movement of said valve
body, said stop being arranged at a lower edge of said sleeve, said
stop being formed by a flange which is detachably fixed to said
lower edge.
27. A device according to claim 19 wherein said valve body is
detachably connected to a valve body base by means of a screw
connection.
28. A device according to claim 19, and further including a valve
body spigot arranged to fit into said outlet channel with a small
clearance for movement, said valve body projecting downwardly from
said valve body.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation-in-part of application Ser. No.
10/099,443, filed Mar. 15, 2002.
BACKGROUND OF THE INVENTION
[0002] Field of the Invention
[0003] This invention relates to a device for closing a pot-like
digestion vessel and more particularly it concerns novel closing
arrangements by which excessive internal pressure in such vessels
is relieved.
[0004] To perform an analysis of materials, it is known for one or
more materials, e.g. a solid or liquid sample material, to be
heated in a digestion vessel, whereby in most cases a pressure
above atmospheric is produced in the digestion vessel and this in
turn promotes the digestion of the sample material or the like.
[0005] A device of the type to which this invention may be applied
is described in EP 0 830 891 A1. In this generic design a resilient
pressure-generating means acting between a screwing part and a
pressure-applying plunger is formed by a stack of metal disc
springs arranged one above the other, the pressure-applying plunger
taking the form of a U-shaped component in which is arranged a
dome-like cage part which is of metal and forms a Faraday cage for
the disc springs. This device has a large number of parts and is
structurally large and in particular tall.
[0006] A device for closing a pot-like digestion vessel is also
described in GB 2 184 040 A. In this known device the
pressure-applying plunger, the screwing part and the resilient
pressure-generating means arranged therebetween are contained in a
hat-like screwed cover of a pot-like supporting vessel into which
is fitted a holding vessel against the cover of which the
pressure-applying plunger acts. The screwing part is mounted to be
vertically displaceable with a pressure-applying piece in a
vertical guide hole in the screwed cover and is in the form of a
nut which is screwed on to a pressure-applying piece extending
coaxially upwardly from the pressure-applying plunger and having a
threaded shaft which passes through a guide hole. Arranged in the
annular wall of the hat-like screwed cover in the screwed-on state
is at the same level as the upper edge of the supporting vessel an
internal annular groove from which a venting passage extends
radially outwards through the annular wall. This known design has a
large number of parts, is structurally large, is complicated and
costly to manufacture and is time-consuming to manipulate. There is
also the risk that the pressure-applying piece and the nut will
move away from one another owing to fouling, for example, as a
result of which different pressure ranges will arise when the cover
of the holding vessel is opened and closed.
[0007] It is the object of the invention to simplify a device of
the above-mentioned types and to design it in such away that a
small or low construction is obtained. Furthermore, the device is
to be improved with respect to its operation. An attempt is also
made to reduce the number of separate parts in the device and the
amount of material it consumes.
[0008] This object is achieved by means of the features described
and claimed hereinafter.
[0009] In a device according to one aspect of the invention, a
pressure-applying plunger and a screwing part fit around one
another in a socketed arrangement by means of at least one annular
wall which may be part of the pressure-applying plunger and which
extends upwardly therefrom preferably as an integral part thereof
and fits around the screwing part like a socket, or which may be
part of the screwing part and extends downwardly therefrom
preferably as an integral part thereof and fits around the
pressure-applying plunger like a socket. It is also possible for
two circumferential walls to be provided of which one annular wall
extends upwardly from the pressure-applying plunger and the other
extends downwardly from the screwing part and for the annular walls
to fit around one another in a socketed arrangement. Not only does
this allow guidance and/or radial support to be obtained for the
pressure-applying plunger but the interior space between the
pressure-applying plunger and the screwing part which holds the
resilient pressure-generating means is closed by the at least one
annular wall, so that contaminants cannot enter the interior space
for the resilient pressure-generating means from the holding space
of the holding vessel in case of lifting of the cover of the
holding vessel through an overpressure reaction, nor can other
contaminants enter from the surroundings of the device. In this way
the interior space is also protected against aggressive treating or
digesting chemicals, whereby the movement function of the device is
protected and long service life is achieved. If screw-thread
guidance is used, positive guidance is provided in both axial
directions of movement, so that in case of an adjustment a secure
adjustment of the screwing part is achieved even if a certain
stiffness is present in the guidance means.
[0010] The seal between the pressure-applying plunger and the
screwing part can be improved by arranging between the guidance
faces which co-operate in a socketed arrangement a seal, preferably
an annular seal, which may, for example, be an O-ring which can be
inserted in an external annular groove in the part around which the
other part fits or in an internal annular groove in the part which
fits around the other.
[0011] Within the scope of the invention there are many possible
ways for the screwing part to be supported against an abutment.
Such an abutment may be formed, for example, by a supported disc
which fits over a location for the digestion vessel in a space to
which microwaves can be applied. If a disc of this kind is open in
all directions it can also be used to cover a plurality of
circumferentially distributed locations for digesting vessels which
include the device. In this case the disc may, in a manner known
per se, be a turntable which is mounted to be rotatable in the
microwaving space together with the locations.
[0012] The abutment may also be formed by the upper wall of a
pressure-absorbing body which delimits a location for the digestion
vessel on both sides, at the bottom and at the top. In this
embodiment the digestion vessel with the device may be placed on
the location and removed therefrom optionally from one side.
[0013] It is also possible, in accordance with one aspect of the
invention, for the abutment to be formed on or supported against
the circumferential surface of the digestion vessel. For this
purpose the screwing part may be formed by the upper wall of a cap,
the annular wall of which can be connected, in its free edge
region, for example, to the digestion vessel, e.g. by screws. It is
particularly advantageous in this case if an externally threaded
ring is fitted on to the circumferential surface of the digestion
vessel and is supported against said vessel, preferably against the
underside of a flange in the edge region of the digestion vessel,
so that the flange absorbs the reaction forces of the device and
ensures positioning of the threaded ring by contact. This
embodiment is distinguished in particular by its small structure
which takes up little space, is handy, consumes little material and
is also of low weight.
[0014] It is possible and advantageous in all embodiments for a
marking or scale to be so arranged between the screwing part or
parts attached thereto and the abutment that, with respect to the
resilient closing force of the pressure-generating means, the
screwing part can be preset in steps or steplessly in such a way
that a given opening pressure is obtained in the interior space of
the digestion vessel, above which pressure the cover of said vessel
automatically lifts and thus opens. This allows the operator to
preset desired maximum internal pressures in the holding space of
the holding vessel while taking account of the material or
materials to be treated.
[0015] If, in a device of the present type, the cover of the
digestion vessel forms a valve body of a valve which opens at a
predetermined internal pressure of the vessel as a result of the
elasticity of the resilient pressure-generating means, a relatively
large pressure surface is available on the inner face of the cover
and a relatively large pre-loading force is therefore required to
retain the cover in its closed position on the digestion vessel.
Consequently, a relatively large expenditure of force is required
to change the pre-loading force and thereby to adjust the internal
pressure value above which the cover is automatically to open.
Moreover, it can be regarded as disadvantageous that when such
opening of the cover by overpressure takes place the actual point
of opening and venting is uncertain and can extend over an
indeterminate portion of the circumference or over the entire
circumferential portion.
[0016] It is a further object of the invention to provide a device
in which the digestion vessel can be opened with a small
expenditure of force. It is also to be achieved that the device is
so configured that on venting of the digestion vessel at an
internal pressure exceeding a given value the venting takes place
at a precisely specified point.
[0017] This object is met by means of a digestion vessel cover
which is formed with an outlet channel extending therethrough and a
valve which closes the outlet channel. The valve is arranged to
open automatically in response to an internal pressure in such
digestion vessel exceeding a given value.
[0018] Advantageous refinements of the invention are also described
and claimed herein.
[0019] In the device according to an aspect of the invention, the
cover has passing through it an outlet channel closed by a valve
which automatically opens at an internal pressure in the digestion
vessel which exceeds a given value.
[0020] Present in the area of the cover in this embodiment is a
special valve which automatically opens at an internal pressure in
the vessel which exceeds a given value, while the cover remains in
its closed position. In this embodiment the size of the opening of
the digestion vessel is not relevant; what is relevant is the size
of the outlet channel which is considerably smaller than the size
of the opening of the digestion vessel or the size of the cover. A
considerably lower pre-loading force is therefore required to close
the valve, and changes to this pre-loading force can be carried out
with a relatively small expenditure of force and with ease of
operation, so that the handling convenience of the device according
to the invention is considerably improved.
[0021] Furthermore, in the embodiment of the invention according to
a specific embodiment, the venting point is restricted to the end
aperture of the outlet channel. Because sample material can escape
during a venting process and fouling can thereby take place,
measures for preventing or eliminating fouling can be arranged or
taken more simply and precisely in this embodiment.
[0022] Further refinements of the invention give rise to simple,
small and operative structures and serve to prevent fouling of the
valve mechanism and to permit precise and easily operated setting
of different pressure values at which the valve opens.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Advantageous embodiments of the invention will be explained
in detail below with reference to a plurality of embodiments and
drawings.
[0024] FIG. 1 is a vertical section through a digestion vessel
having a device according to the invention for closing the
vessel;
[0025] FIG. 2 is an enlarged view of a detail marked X in FIG.
1;
[0026] FIG. 3 is a vertical section through a modified vessel
arrangement having a device for closing a digestion vessel, which
is also modified;
[0027] FIG. 4 is a vertical section through a digestion vessel
arrangement having a modified device for closing the vessel,
according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] A pot-like digestion vessel 1 having a circumferential wall
1a which is in the form of a hollow cylinder and is, for example,
relatively thin, and a flat bottom wall 1b, is surrounded, and
supported in the radially outward direction, by a supporting shell
2 in the form of a hollow cylinder which may extend up to a flange
1c on the upper edge of the circumferential wall 1a, so that the
flange 1c rests on the upper end face of the supporting shell
2.
[0029] The upper opening of the digestion vessel 1 is to be closed
and opened by means of a cover 3 which is, for example, flat and in
the form of a stepped cylinder of which, in the embodiment shown, a
lower cylindrical cover extension 3a fits into the digestion vessel
1 with little play and is sealed, preferably by an annular seal 4.
The latter may be formed by an O-ring 4a which is mounted in an
annular groove in the circumferential surface of the cover
extension 3a. The shoulder face 3b of the cover 3 thus rests on the
flange 1c.
[0030] The device, designated as a whole by reference numeral 5,
for closing the digestion vessel 1 even when a pressure above
atmospheric is present in the interior space 1d of said digestion
vessel, consists of three main parts, namely a pressure-applying
plunger 6, a screwing part 7 at least part of which is arranged
above the latter, and a resilient pressure-generating means 8 which
is arranged between an upwardly directed supporting face 6a on the
pressure-applying plunger 6 and a downwardly directed supporting
face 7a on the screwing part 7 and which in functional operation is
preloaded with a given compressive force. In the embodiment shown
the pressure-generating means 8 comprises a plurality of disc
springs stacked on top of one another in opposite directions. The
screwing part 7 has at least in its upper portion an external
thread 7b with which it is screwed into a threaded bore 9a of an
abutment 9 as a screwing part. To allow the screwing part 7 to be
turned an element 11 for applying rotation is arranged in its upper
face and is intended for a rotation tool which can be positively
engaged therewith in rotation. In the embodiment shown the element
11 for applying rotation is formed by a noncircular socket.
[0031] To cover the space 12 occupied by the pressure-generating
means and thus to protect it from fouling, there is provided an
annular wall 7c which surrounds the space 12 and which fits at
least partially around the pressure-applying plunger 6 and/or the
screwing part 7 in a socketed arrangement. In the embodiment shown
the annular wall 7c, which is preferably in the form of a hollow
cylinder, extends downwardly from the screwing part 7 as an
integral part thereof, fitting at least partially over the
preferably cylindrical circumferential surface of the
pressure-applying plunger 6 with clearance for movement and thus
making the space 12 inaccessible from the sides.
[0032] The amount of the vertical overlap a can be sufficiently
large to allow a guidance function to be performed between the
pressure-applying plunger 6 and the screwing part 7 and/or an
annular seal 13 when the device 5 telescopes in a manner which has
yet to be described. Preferably arranged in the gap at the overlap
is a sealing ring 13a, e.g. an O-ring, which is mounted in an
annular groove in the circumferential surface of the
pressure-applying plunger 6 and is covered by the inner surface of
the annular wall 7c in any telescoped position. The maximum amount
of telescoping movement b in the vertical direction is determined
in the present embodiment by the distance between the annular wall
7c and the cover 3. If the pressure-applying plunger 6 is formed to
have a flange 6b as indicated in ghost lines, the maximum amount of
telescoping movement b is determined by the distance from the
flange 6b. The flange 6b allows the area over which the
pressure-applying plunger 6 acts against the cover 3 to be enlarged
and the pressure per unit area effective in operation to be
reduced.
[0033] The pressure-generating means 8, or the spring discs, may be
centered by the inner circumferential surface of the annular wall
7c. However, to avoid the frictional wear which occurs between the
two during telescoping, the preferably annular pressure-generating
means 8 is centered internally with a small amount of clearance for
movement by means of the centering spigot 6c which in the
embodiment shown extends upwardly from the pressure-applying
plunger 6 as an integral part thereof and may then engage in, or
terminate shortly before, a guide hole 7d present between the
supporting face 7a and the element 11 for applying rotation, thus
providing additional guidance, which, however, is not absolutely
essential, for the pressure-applying plunger 6.
[0034] Arranged in the pressure-applying plunger 6, preferably
coaxially therewith, is a through hole 14 which may, for example,
be lined with an annular wall 15 which may have at its lower end a
flange which allows it to be inset into a recess in the
pressure-applying face. To allow it to be secured axially in the
pressure-applying plunger 6, the annular wall 15 may be a press-fit
therein.
[0035] The hole 14 may be used to hold functional elements, e.g.
sensor elements, which pass through the screwing part 7 and which
are functionally connected via said hole to associated control or
regulating devices. A temperature sensor, for example, may the
provided, which is inserted in the hole 14. A pressure measuring
element may also be inserted in the hole 14, the vertical position,
or rather the change in position, of which pressure measuring
element, on lifting of the cover 3, serves as an indication of the
level of the internal pressure prevailing in the digestion space 1d
in operation.
[0036] In the embodiment shown in FIG. 1 the abutment 9 is formed
by the upper wall 16a of a supporting housing 16 which may be of
box-like configuration with a bottom wall 16b and two side walls
16c and forms a holding space 17 for the digestion vessel 1, which
space is open at the front or is horizontally continuous and in
which said vessel can be installed and removed again from the
appropriate side. In its installed state the digestion vessel 1
rests with its bottom wall 1b, which is flat in the embodiment
shown, on the bottom wall 16b of the supporting housing 16, whereby
the first bottom wall 1b is supported against the internal
pressure. An intermediate layer 18, which is preferably made of a
thermally insulating material, e.g. plastics material, is arranged
between the bottom walls 1b and 16b to reduce the dissipation of
heat from the digestion vessel 1.
[0037] The relatively great length of the annular wall 7c, which
extends downwardly from the screwing part 7, enables the screwing
part 7 to have a large range of vertical adjustment and thus to be
adapted to digestion vessels 1 of different heights, if the
external thread 7b extends at least to the lower end region of the
annular wall 7c or, for example, over its entire vertical
length.
[0038] To prevent the pressure-applying plunger 6 from dropping out
of the position in which it overlaps the screwing part 7 when there
is no digestion vessel 1 under the device 5, a limiting device 21
is provided between the pressure-applying plunger 6 and the
screwing part 7 or the annular wall 7c to limit the maximum
extension movement of the pressure-applying plunger 6 and which in
the embodiment shown is formed by a stop device having a stop
element 22a in the lower end portion of the annular wall 7c. The
opposing stop element 22b is preferably formed by the sealing ring
13a which projects somewhat from the circumferential surface of the
pressure-applying plunger 6 in the radial direction and can thus
form the opposing stop element 22b without the need for any special
opposing stop element. As a result, the sealing ring 13a performs a
sealing and stopping function. The stopping element 21 is formed by
an internal annular bead on the inner circumferential surface of
the annular wall 7c. To allow a small clearance for movement or
sliding, the diameter of the annular bead is made larger than the
diameter of the pressure-applying plunger 6, thus enabling the
latter to move in the annular bead. The internal diameter d1 of the
annular bead is made somewhat smaller than the internal diameter d2
of the rest of the annular wall 7c, thus enabling the internal bead
to be formed. At the same time, the internal diameter d2 is made
only sufficiently large for the sealing ring 13a to form a
resilient seal against the inner circumferential surface 7e of the
annular wall 7c. In the embodiment the outer flank of the stop
element 22 or the annular bead is formed by an oblique or rounded
lead-in face 23. The inner flank 24 is the face of a step which
preferably extends approximately at right angles to the center axis
of the pressure-applying plunger 6. In the embodiment the internal
annular bead is pointed in cross-section, producing a pointed
annular edge. The sealing ring 13a will thereby be sheared off if
the pressure-applying plunger 6 is forcibly extracted from its
socketed connection and protection is provided against dismantling
in view of the damage that would be caused to the sealing ring
13a.
[0039] In the embodiment shown in FIG. 3, in which the same or
comparable parts are designated by the same reference numerals, the
screwing part 7 with its annular wall 7c has been made so large
that it fits around at least the upper edge portion of the
digestion vessel 1 like a cap and is screwed thereto, so that the
circumferential wall 1a or the flange 1c or an optionally present
supporting shell 2, to any of which the annular wall 7c may be
screwed, forms the abutment 9. In the embodiment a supporting ring
25 is fitted on to the digestion vessel 1, preferably in the upper
region of the digestion vessel 1, and in particular is arranged to
rest against the flange 1c and to be connected to the outer
circumferential surface of the digestion vessel 1, e.g. by pressing
on or bonding. A connection of this kind ensures that the forces
applied to the abutment are transmitted to the digestion vessel 1.
If the supporting ring 25 rests against the flange 1c a connection
to the outer circumferential surface can be omitted as the flange
1c absorbs the forces from the abutment. However, in this case too
it is advantageous for the supporting ring 25 to be retained on the
digestion vessel 1, e.g. by bonding or pressing on, so that it
cannot be lost.
[0040] The screw connection between the screwing part 7 and the
supporting ring 25 preferably comprises an internal thread 7f in
the end portion of the annular wall 7c and a matching external
thread on the supporting ring 25.
[0041] In the two embodiments described above, the
pressure-applying plunger 6 can form the cover 3, as shown in FIG.
3. In the embodiment shown in FIG. 1 the cross-sections of the
pressure-applying plunger 6 and the screwing part 7 would have to
be enlarged as appropriate to allow the pressure-applying plunger 6
to form the cover 3. The hole 14 would also have to end at a
distance from the end of the pressure-applying plunger 6 which
faces towards the digestion vessel 1.
[0042] In all the embodiments it is also possible for the
pressure-applying plunger to have a U-shaped configuration in
cross-section as shown in FIG. 3 and thus to be provided with a
circumferential wall 6d which, owing to its axial length, ensures
that the pressure-applying plunger 6 is guided in such a way as to
be secure against tilting and which can also ensure sufficient
sealing. It is also advantageous for one or more grooves 6e spaced
at an axial distance from one another to be arranged in the
circumferential surface of the circumferential wall 6d, which
grooves both improve the seal and, in view of the differing thermal
expansions, prevent any harmful tensions from arising in the fit
when the material of the pressure-applying plunger, in particular
at fairly high digestion temperatures, is relatively soft or
yielding.
[0043] In the embodiment shown in FIG. 3 the resilient
pressure-generating means 8 is formed by a helical spring which is
supported against the upper wall of the screwing part 7 and bears
against the pressure-applying plunger 6, at the bottom of a recess
in the present case.
[0044] In the embodiment shown in FIG. 3, too, there may be
provided a centering spigot 6c which likewise is preferably
circular in cross-section and can be guided longitudinally or
vertically in the guidance hole 7d in the upper wall of the
cap-like screwing part 7 with clearance for movement. At its lower
end the centering spigot 6c preferably has a flange to reduce the
pressure per unit area, against which the pressure-generating means
8 can bear.
[0045] In all the embodiments it is advantageous to apply a marking
between the screwing part 7 and a part positioned on the digestion
vessel 1 or on the cover 3 or on the pressure-applying plunger 6,
which marking shows the axial position of the screwing part 7 with
respect to the positioned part and preferably allows the screwing
part 7 to be preset in a defined manner. The marking may, for
example, be formed by a scale and a pointer which are located in
each case on one of the two parts to be compared. In the embodiment
according to FIG. 1 the marking 27 can be arranged, for example, on
the upper faces of the screwing part 7 and of the abutment 9,
preferably close to or at the threaded joint in the screwed
assembly, e.g. in the form of an annular scale on the upper wall
16a and a pointer on the screwing part 7.
[0046] In the embodiment shown in FIG. 3 the marking 27 may be
formed, for example, by the front end of the centering spigot 6c
and the lower or upper edge of the guide hole 7d. It is also
possible for the markings or scale divisions to be applied to the
inner wall face of the guide hole at axial distances from one
another, which allow the position of the centering spigot 6c and
therefore the open or closed position of the pressure-applying
plunger 6, and optionally also of the cover, to be seen or read off
against the free end of the centering spigot 6c.
[0047] In the embodiment shown in FIG. 1 the digestion vessel 1 is
made of a corrosion-resistant material, in particular plastics
material and preferably polytetrafluoroethylene (PTFE). The other
parts of the digestion vessel 1 including the supporting housing 16
are made preferably of material which is permeable to microwaves
and preferably plastics material. This may also be true of the
device 5. In the embodiment, the spring forming the resilient
pressure-generating means 8 or the resilient elements are made of
metal, in particular of spring steel or special steel. The screwing
part 7 can also be made of metal, e.g. special steel, in which case
it acts as a Faraday cage with respect to the spring. Operation is
improved if the cage has a polished surface and its edges are
rounded. It is also advantageous for the dimensions of the cage,
i.e. its diameter and axial length, preferably to be sized at
between a quarter and one complete wavelength of the microwave
radiation used. In addition, the surface of the metal cage may be
coated with a material, such as e.g. PTFE, which is resistant to
corrosive chemicals, to prevent the surface of the metal from being
attacked by the chemicals.
[0048] For a digestion process a sample material is placed in the
digestion vessel 1' and the digestion vessel 1 is closed with the
device 5. As this is done the screwing part 7 is screwed in (FIG.
1) or on (FIG. 3) sufficiently far for the resilient
pressure-generating means 8 to exert a closing force which
corresponds to a given internal pressure. If the internal pressure
rises in operation to more than a given value or the set value, the
cover 3 or the pressure-applying plunger 6 automatically opens, in
which case the pressure-generating means 8 yields and the internal
pressure can escape. In this case the device 5 acts as a
pressure-release valve, the opening pressure being adjustable by
screwing in the screwing part 7.
[0049] The embodiment shown in FIG. 3, where the same or comparable
parts are designated by the same reference numerals, differs from
the embodiment described above with respect to a plurality of
arrangements.
[0050] Firstly, the abutment 9 is not part of a supporting housing
16 which holds the entire digestion vessel 1 but of a small
cap-like supporting housing 22 which, although it similarly
transmits the reaction forces to the digestion vessel 1, fits
around only the upper portion of the digestion vessel 1, is
supported directly or indirectly against this upper portion and
therefore transmits the reaction forces to this portion of the
digestion vessel 1. The direct or indirect connection to the upper
portion of the digestion vessel 1 is effected by a screw
connection. A radial venting aperture 7g is provided in the annular
wall 7c above the flange 1c or the supporting ring 25. The bottom
wall 1b of the preferably cylindrical holding vessel 1 preferably
has a hemispherical configuration, thus enabling the wall to be
evenly stressed.
[0051] In the embodiment shown in FIG. 4, in which the same or
comparable parts are designated by the same reference numerals, the
digestion vessel 1 (apart from the cover 3) and the supporting
housing 16 can have substantially the same or in principle the same
configuration. The important differences are the following.
[0052] Firstly, the screwing part 7 which forms a closing part is
made sufficiently long for it to extend as far as the cover 3 and
therefore to be able to be braced against the cover 3, whereby the
digestion vessel 1 can be closed in a tightly-sealed manner and the
cover 3 rigidly closed.
[0053] Secondly, an outlet channel 31 which is closed by a valve 32
is arranged in the cover 3, the valve 32 opening automatically if
the internal pressure in the digestion vessel 1 exceeds a
predetermined value. The outlet channel 31 can have an angled
configuration, the first section 31a of the outlet channel which
leads from the interior space 1d preferably extending coaxially in
the cover 3 and passing over into a laterally extending outlet
channel section 31b in the upper portion of the cover 3. A valve
body 33 is used to close the outlet channel 31 in an arrangement
comparable to the pressure-applying plunger 6 of the previous
embodiment. The valve body 33, which is, for example, cylindrical,
closes the outlet channel 31 with its bottom face; in the
embodiment said valve body fits into an upper widened portion 31c
of the channel which has a step face 31d forming, for example, a
right angle, which step face forms a stop for a downwardly directed
movement of the valve body 33. The lateral outlet channel section
31b branches off from the widened channel section 31c above the
step face 31d. A spigot 33a which is dimensioned to fit the outlet
channel section 31a with clearance for movement, and which closes
the outlet channel section 31a with small clearance for movement,
may project from the underside of the valve body 33. The length c
of the spigot 33a is shorter than the length a of the widened
portion 31c of the channel.
[0054] The valve body 33 extends downwardly from a valve body base
33b which has an enlarged cross-section and which is dimensioned to
fit, with clearance for movement, the internal cross-sectional
shape and size of the screwing part 7, which in this area has a
hollow cylindrical configuration, and thus is guided to be
vertically displaceable therein. A stud 33c can extend
concentrically upwardly from the valve body base 33b, which stud
can for example be formed integrally with the valve body base 33b
and passes through an upper end wall 7f of the screwing part 7 via
a hole 34 and can close said hole at the upper end or project
beyond it. Located between the end wall 7f and the valve body base
33b is a spring 35, e.g. a helical spring, surrounding the stud
33c, which spring is supported against the end wall 7f and preloads
downwardly the closing part designated as a whole by reference
numeral 36. The upper end of the stud 33c can form with the upper
end face of the screw part 7 an indicator for the pressure
prevailing at any time within the movement range of the length c,
or for the opening pressure.
[0055] The closing part 36 is formed preferably in two parts with
the valve body 33 and is detachably connected to the latter by
means of a screw connection. In the embodiment a threaded pin 33d
projects downwardly from the valve body base 33b, on to which pin
the valve body 33 is screwed by means of a threaded bore 33e and is
thereby retained detachably and exchangeably. For the purpose of
adaptation to different covers 3 a plurality of different valve
bodies 33 adapted in each case to the associated cover 3 and which
can be exchangeably attached to the valve body base 33, can be
provided.
[0056] A stop 37 to limit the downward movement of the closing part
36 can be arranged at the lower end of the screwing part 7. In the
embodiment a disc flange 38 is preferably detachably fixed to the
lower portion of the screwing part 7, which disc flange has a
coaxial bore 39 by means of which the valve body 33 passes through
the disc flange 38 and can also, for example, be guided therein,
and projects downwardly beyond the disc flange 38.
[0057] For a digestion process the filled digestion vessel 1 is
placed below the valve body 33 and the screwing part 7 is screwed
manually against the cover 3 using a rotation tool 41 which is
positively connectable by means of a non-circular socket connection
or two socket connections 42 to the upper end of the screwing part
7, whereby the digestion vessel 1 is rigidly closed with an axial
loading. In this case the screwing part 7 bears against the cover 3
with its disc flange 38, the pressure per unit area being lower
because of the relatively large area of the disc flange 38. When
the screwing part 7 is moved towards the cover 3 the valve body 33
contacts the valve seat 33a, and the valve body base 33b or the
closing part 36 is preloaded by the preload distance V against the
spring 35, the spring 35 pressing against the valve seat with a
given preload, e.g. 200 N/mm. In the embodiment the first section
33a of the outlet channel has a diameter of approx. 8 mm.
[0058] In the embodiment the valve body 33 is made of a
corrosion-resistant material e.g. ceramic or plastics material,
preferably PTFE. The valve body base 33b can be made e.g. of
stainless steel or ceramic material. The screwing part 7 and the
disc flange 38 are made preferably of corrosion-resistant metal, in
particular special steel. This also applies to the spring 35, which
may be made e.g. of spring steel.
[0059] To protect the interior space of the screwing part 7 against
fouling an annular seal 42, preferably comprising a sealing ring
42a mounted in an annular groove in one component, in particular in
the valve body base 33b, is arranged between the valve body base
33b and the wall of the screwing part 7 and cooperates sealingly
with the opposing wall of the other component. An annular seal 42
of this kind can also be provided between the disc flange 38 and
the valve body 33.
[0060] For a digesting operation the vessel arrangement is placed
in a microwave oven and microwaves are applied thereto. If the
internal pressure in the digestion vessel 1 exceeds a predetermined
value because of internal heating and, if applicable, a reaction of
the material contained in the digestion vessel, the valve body 33
automatically lifts from the valve seat, whereby the outlet channel
31 is opened and the internal pressure is limited by means of
venting through the outlet channel 31.
[0061] In all the embodiments it is advantageous for the device 5
or the valve 32 to be configured to be so adjustable that the cover
3 or the valve 32 opens at different pressures in the digestion
vessel 1. By this means the opening pressure and therefore the
pressure effective during treatment or digestion of the material
can be changed and adjusted to a predetermined requirement. This
can be achieved, for example, in that a plurality of resilient
pressure-generating means 8 or a plurality of springs 35 of
differing compressive force which are optionally usable by
exchange, are provided. The device 5 or the valve 32 can thereby be
adapted to opening pressures of different values.
* * * * *