Patent Description:
Plasma sources are commonly used in optical emission and mass spectrometers. In a plasma source, such as in inductively coupled plasma (ICP) sources, plasma is generated at a high heat, in which atoms and molecules can be ionized. In such a plasma, extremely high temperatures may occur, such as temperatures of <NUM>,<NUM> or even <NUM>,<NUM>.

In optical emission spectrometry, vaporized atoms and ions in a plasma are brought to high energy states. The atoms and/or ions subsequently relax to their ground state, during which process they give off electromagnetic radiation with wavelengths that are characteristic of the elements involved and depend on the quantized energy level structure of each atom or ion.

Detection of emitted photons can be performed by radial or side-on viewing of the plasma or by axial or end-on viewing of the plasma. Radial viewing is the classical operational mode of optical emission spectrometers. The optical path towards the detector typically involves an optical periscope that directs the incoming radiation towards the detector. The periscope has an internal mirror that deflects incoming electromagnetic radiation towards the detector. Due to the close proximity of the periscope to the plasma and the intense heat and radiation from the plasma, the optical mirror within the periscope may need to be replaced. Also, the plasma source needs regular maintenance. Thus, a user will need to be able to regularly access the inside of the plasma source chamber. Care must be taken whenever handling the ICP source or source chamber after the source has been in use due to the high temperatures involved. Thus, any mechanism for opening and closing the source chamber must be protective against heat, not only during use but also when opening the chamber for any type of maintenance or adjustment after use, and all parts that the user interacts with, such as a door handle and outer surfaces, should be thermally isolated from the heated interior. Further, the source chamber and door mechanism must protect also against UV light and electromagnetic radiation, outgoing as well as ingoing, so that the instrument as a whole complies with the electromagnetic compatibility requirements of laboratory standards.

An example of an ICP chamber is disclosed in <CIT>. This prior art ICP chamber has a hinged door door, which is less practical as the opened door, which may be hot, extends towards the operator of the instrument.

<CIT> discloses a vacuum lock on a vacuum chamber, the vacuum lock having a sliding plate with a driving rod. The mechanism is designed so as to press the gate on to a seal when blockage of the plate occurs. The vacuum chamber is designed for semiconductor wafers and may be used to pass substrates from one atmosphere to another.

<CIT> discloses a safety casing for an X-ray apparatus with a sliding door in a pivotable frame. The door has a protective element, a lead glass pane, which is impenetrable for X-ray radiation This door mechanism either slides or pivots; when the pivot function is active, the sliding function is disabled, as shown by the lock signs in figure 3a-3e in the document, and vice versa.

The present invention seeks to provide a solution to the above challenges by providing a sliding door assembly for use with an ICP torch box / source chamber. The sliding door assembly reduces the risk of heat related injuries as it eliminates the possibility of inadvertently touching the inner surface of the door. It further provides a smooth and secure opening and closing of the torch box and improves the accessibility of the chamber as the door moves out of the way when fully opened and does not limit the space in front of the opening for operations and access.

In one aspect, the invention relates to a sliding door assembly as defined in claim <NUM> for use with an inductively coupled plasma (ICP) torch box. The door assembly comprises a door, a guiding mechanism for allowing movement of the door in a first direction along at least one access opening of the ICP torch box so as to allow opening and closing the torch box, and allowing movement of the door or at least a part thereof in a second direction, substantially perpendicular to the first direction, so as to move the door or at least a part thereof towards the at least one access opening when closing the torch box.

By using a sliding door for closing off the access opening of the torch box, space is saved in front of the torch box and the risk of touching hot door parts is significantly reduced. By using a sliding door which is capable of moving both parallel to the opening and towards (and away from) the opening, preferably in a single movement, a good sealing of the opening can be achieved in a simple manner. The sliding door assembly of the present invention is preferably arranged for an essentially linear movement in two directions. In addition, the sliding door assembly of the present invention preferably lacks hinges and may be arranged for avoiding rotational movements of the door parts.

Accordingly, the guiding mechanism is preferably arranged for providing a substantially linear movement in both the first direction and the second direction.

Typically, a torch box has a single opening, which may be referred to as access opening as it provides access to the torch. However, embodiments can be envisaged in which the torch box has two or more openings which may be closed off by a single sliding door or by multiple sliding doors.

The second direction may be completely perpendicular to the first direction, thus defining an angle of <NUM>°, but smaller or larger angles may also be used, such as angles of, for example, <NUM>°, <NUM>° or <NUM>°.

The sliding door assembly can comprise a sealing mechanism for sealing the door to the torch box, in a properly and fully closed position. Preferably, the sliding door assembly comprises at least one resilient element for causing pressure to be applied to the door or door part in the second direction when the door is closed. The sealing mechanism can advantageously be resilient, such as comprising a silicon strip protruding from a groove circumscribing the at least one access opening of the torch box or a door frame surrounding the at least one opening that is being closed with the door mechanism, and/or protruding from a groove on the inside of the door.

The sliding door assembly preferably comprises a locking mechanism for locking the door in a closed position. 'Locking' as used herein indicates that the door slides into a particular final closed position and a force is required to bring it out of the locked position, thus it"locks" into the designated final closed position, preferably with a click and/or noticeable haptic feedback that indicates to the user that the position has been reached.

The door of the door assembly comprises an inner door panel and an outer door panel, which are interconnected so that the inner door panel is moved by the outer door panel. The configuration of an inner and an outer door panel provides enhanced thermal insulation, ensuring that the outside of the door does not get too hot. The guiding mechanism is preferably arranged so that it allows movement of the outer door panel in the first direction only (back and forth) parallel to the plane of the opening of the torch box, while allowing and guiding movement of the inner door panel in both the first direction and the second direction (and the respective opposite directions). The outer door panel is engaged with a first sliding mechanism, for allowing longitudinal movement in the first direction of the outer door panel back and forth (opening and closing directions), with the inner door panel following the outer door panel, and wherein the inner and outer door panels are interconnected via a second sliding mechanism for allowing movement of the inner door panel relative to the outer door panel in both the first and the second direction. With this mechanism, the distance between the inner and outer door panels can be increased as the door is put in a fully closed and locked position so that the door is pressed against the chamber, giving an effective seal. Preferably, moving the outer door panel in the first direction will cause the inner door panel to simultaneously in the second direction. In some embodiments, the inner door panel moves over part of its trajectory simultaneously in the first direction and in the second direction.

In one embodiment, the inner door panel is configured so that the door assembly has a first closed position that is achieved by longitudinal movement in the first direction of the door along the first sliding mechanism towards an inner door stopper, and a second closed position that is achieved, after reaching the first closed position, by simultaneous longitudinal and transverse movement (i.e. in the first and second direction respectively) within the door assembly of the inner door panel relative to the outer door panel, along the second sliding mechanism. This can be suitably arranged such that when the inner door panel reaches the inner door stopper it cannot move further in the first direction (longitudinal direction) but the outer door panel can be moved further and by doing so, the second sliding mechanism guides the inner door panel in the second direction. Thus, the inner door panel moves not only in the perpendicular (or second) direction relative to the plane of the opening of the torch box, but in both directions relative to the outer door panel, as the outer door panel moves further in the first, longitudinal, direction.

Accordingly, in one embodiment of the door assembly of the invention, the outer and inner door panels are interconnected such that after the door has reached a first closed position, the space (distance) between the outer and inner door panels increases as the outer door panel is moved further in the first direction / closing direction and simultaneously the inner door panel moves inwardly towards the torch box opening. In other embodiments both the outer door panel and inner door panel move inwardly after the door has reached a first closing position, leading to the same functional result that the inner door panel moves closer to the torch box opening. Thus, if a sealing is placed between the inner door panel and torch box, the sealing is compressed as the inner door panel moves closer to the opening.

A second closed position is defined as a final position when the inner door panel is in a desired final position having moved inwardly towards the torch box opening to create a seal. Typically, the door cannot move further when the second closed position has been reached.

The inner door stopper can suitably be situated on the ICP torch box on which the door assembly is to be mounted, or on a door frame of the assembly or associated with the assembly that is to be mounted on the torch box. Such a door frame can be considered as a part of the door assembly but can also be seen as a separate optional part associated with the torch box but configured to operate with the door assembly.

As understood from the above, the second sliding mechanism can suitably be actuated by application of force in the first direction to the outer door panel following the inner door panel meeting the inner door stoppers. This is arranged by providing the second sliding mechanism by at least a pair of parallel inner guide members that are arranged longitudinally (along the first direction) between the inner and outer door panels, and at least two pairs of bearings that interconnect with the inner guide members. The inner guide members are fastened to the outer door panel and the pairs of bearings mounted on support fastened to the inner door panel, or vice versa, meaning that the inner guide members are in an alternative embodiment fastened on the inner door panel and the supports holding the bearings in that case mounted on the outer door panel. Thus, when a force in the first direction is applied to the outer door panel, after it has reached the first closed position where the inner door panel stops at the stopper, further moving the outer door panel will force the bearings to move along the inner guide members (as the inner guide members, or the bearings, are moving along with the outer door panel in the first direction but the inner door panel cannot move further in that direction), thereby exerting a transverse force on the inner door panel and thereby moving the inner door panel in an inward direction, towards the opening of the torch box, and eventually into the second closed position.

The inner guide members can preferably be provided with slots and the supports holding the bearings being situated so that the bearings are placed in and mate with the slots and can move within the slots when the door panels move relative to each other, the slots each having an opening end and a closing end and being shaped such that when the door is moved towards the second closed position, the bearings move along the slots in a longitudinal and inward direction, towards the closing end of the slots, until they reach the closing end and the door is in the final closed position. The closing end of the slot is further away from the outer door panel than the opening end of the slot, such that when the bearing is in the closing end the door panels are further apart than when the bearings are in the opening ends of the slots. In the embodiment where the inner guide members are fastened on the inner door panel and the supports holding the bearings are arranged on the outer door panel the same applies, but in that embodiment the bearings have a fixed distance to the outer door panel and thus the slots are shaped so that the closing ends of the slots are further away from the outer door panel than the opening ends, such that the distance between the inner and outer door panels is greater when the bearing is in the closing end than in the opening end of the slot.

The slots can suitably have a gradient geometry so that the inward movement of the inner door panel decreases in magnitude relative to the simultaneous (relative) movement in the first direction, as the door is moved towards a second closed position. In other words, this means that as the outer door panel is moved towards the second or final closed position, the inner door panel moves inwardly, with gradually less movement per unit-length of movement of the outer door panel, as the outer door panel approaches the final closed position. Typically, the force required to move the door from the first to the second position gradually decreases as a result.

The sealing mechanism mentioned above can advantageously be provided on the inner door panel, for securely sealing the inner door to the ICP torch box or door frame thereof. The sealing mechanism can be provided by a heat resistant elastic sealing that extends around or near the outer periphery of the inner door panel, so that when in a closed position, the elastic sealing meets an outer surface of an IPC torch box (the surface having the opening to be closed by the door assembly) or a door frame that is tightly secured to the torch box, to generate a seal therebetween.

Preferably, during the movement of the inner door panel by the guidance of the second sliding mechanism, the elastic sealing is compressed by the inward movement of the inner door panel. It follows that the outer door panel is connected with the guiding mechanism such that it cannot move transversely, and thus as the second guiding means act to push the outer door panel and inner door panel apart as the outer door panel is moved towards the final closed position, the inner door panel is pressed inwardly as the outer door panel remains essentially fixed in its plane, not able to move transversely.

Preferably, a locking mechanism as mentioned above is arranged in the door assembly for locking the door assembly in the second closed position which is described above. The locking mechanism can be arranged with a groove in the inner guide members' slots, near the closing ends of the slots, so that when the door is moved towards its second closed position, the respective bearing that mates with the slot is pushed into the groove, thereby locking the door in the second closed position.

The locking mechanism can also be of other type, such as any of various suitable latch embodiments or a spring-function male-female locking mechanism that becomes engaged as the door is pushed into a locking position. It is preferred that the locking mechanism provides a haptic sensation when it locks and preferably "clicks" into position, such that it cannot be inadvertently almost but not fully closed.

In some embodiments the door assembly is further provided with an electronic closing sensor that senses if the door is fully and properly closed or not and connected to the instrument system such that the torch box cannot be operated unless the sensor gives a positive signal that the door is closed.

It follows that the slots are preferably shaped so as to have a generally tilted main direction relative to the opening/closing moving direction (first direction) of the door, this forces the bearings (and inner door panel) downwardly as the door is moved from the first closed position to the second closed position and upwardly when the door is opened from the second closed position to the first closed position.

Preferably, the mentioned grooves of the slots, providing the locking function, hold the bearings in a position slightly closer to the outer door panel than in an intermediate position where the bearing has to pass an edge point defining a boundary point between the groove and the main area of the slot. Thus, the edge point is the point of highest sealing pressure and is preferably shaped so as to form a haptic barrier, i.e. providing a haptic sensation as the bearing falls in the groove and the door thus falls in the locked-in position.

In useful embodiments the slots and grooves thereon are shaped and interact with the bearings such that the bearing will pivot away from the edge point when being pushed not sufficiently to pass over the edge point, meaning that if the door is not fully closed and does not attain the locked position (the bearings not pushed over the edge points) the bearings will pivot back and thus the door slide back. In some embodiments one or more springs are arranged to provide a force pulling back from an almost closed position to a more open position spring. Similarly, if the door is slightly pushed from a closed locked position but not sufficiently to push the bearings out of the grooves and over the edge point, they will pivot back, and the door will regain a fully closed and locked position.

In some embodiments one or more spring is provided and arranged between the inner and outer door panel to provide force pulling the door into a final closed position or provide force pulling the door open from a not fully closed position. Thus, in some embodiment one or more spring provides additional force in a direction pulling the door open if it has not reached a locking position, e.g. if a slot is provided as described above, such one or more spring can provide force to pull back the door if it has not been pushed beyond the edge point into a locked position.

The invention further provides an ICP torch box having a sliding door assembly as described herein.

Another aspect of the invention provides an inductively coupled plasma optical emission spectrometer comprising an ICP torch box provided with at least one sliding door assembly as described herein.

Yet another aspect of the invention provides the use of an ICP torch box provided with at least one sliding door assembly as described herein. Such use may comprise opening and/or closing the torch box by a movement substantially parallel to the front surface of the torch box.

The skilled person will understand that the drawings, described below, are for illustration purposes only.

In the following, exemplary embodiments of the invention will be described, referring to the figures. These examples are provided to provide further understanding of the invention, without limiting its scope.

In the following description, a series of steps are described. The skilled person will appreciate that unless required by the context, the order of steps is not critical for the resulting configuration and its effect. Further, it will be apparent to the skilled person that irrespective of the order of steps, the presence or absence of time delay between steps, can be present between some or all of the described steps.

The sliding door in accordance with the invention can be arranged on an ICP torch box, such as an ICP torch box for an ICP emission spectrometer. The sliding door allows for easy and safe access to the interior of the torch box and can have a two-step mechanism for closing the door, so as to provide a secure closing and sealing mechanism of the torch box interior from its surroundings.

Thus, the sliding door can be adapted to move along an opening of an ICP torch box, which opening may be provided in a wall of the torch box. When the door is moved from an open to a closed position, the door moves in two directions; a first direction along the opening of the ICP torch box, and a second direction that is approximately perpendicular to the first direction, towards the opening and thus towards the ICP torch box. As the door moves in the second direction, the door is sealed in a locked position, thereby isolating the interior of the box. The movement in the second direction preferably follows the movement in the first direction, i.e. there is first a movement in the first direction to close the ICP torch box, followed by movement in the second direction to lock the door in a closed position and simultaneously provide a seal between the door and the torch box.

The sliding door can be provided as an assembly that constitutes two door panels, an inner door panel and an outer door panel. During the first movement of the door assembly, the inner and outer door panels move in a concerted fashion; the movement in the second direction is preferably effected by the inner door panel only. Thereby, the inner door panel provides the seal between the door assembly and the torch box.

An exploded view of the main parts of a door assembly in accordance with an embodiment is shown in <FIG>, together with guiding means of such a door assembly. <FIG> shows how guide blocks <NUM> are fastened with screws <NUM> to the outer door panel <NUM>. Adhesive fasteners <NUM> are fastened to the outer door panel to hold an optional outer front shield <NUM> (not shown).

A window frame <NUM> is arranged on the outer door panel <NUM> to expose a window on the inner door panel <NUM> that comprises a window <NUM> (preferably made of thermal welding glass to block UV light) and a grid <NUM> formed by a drilled hole pattern in the inner door panel <NUM> (which makes it possible to observe plasma without creating an opening for electromagnetic radiation). The glass <NUM> may be held by, for example, two or four clamps. Handle <NUM> is fastened to the outer door panel with screws <NUM>. Second guiding members <NUM> are fastened to the outer door panel with screws <NUM>. The second guiding members have slots <NUM> that interact with bearings <NUM> which are held by support members <NUM>. The support members <NUM> are fastened to the inner door panel <NUM> with screws <NUM>. A sealing <NUM> is adhered to the inside of the inner door panel. The guide blocks <NUM> can slide along rails <NUM>. Outer door stoppers <NUM> stop the sliding motion of the door when the door is moved towards a fully open position.

<FIG> shows a side view of the door assembly showing the outer door panel <NUM> which is interconnected with the inner door panel <NUM>. An optional front shield <NUM> is fixed to the outer door panel <NUM> and a handle <NUM> is also fixed to the outer door panel <NUM>, for operating the door. The outer door panel <NUM> is connected to parallel guide rails <NUM>. Support members <NUM> are fixed to the inner door panel <NUM>; attached to the support members are bearings (not seen in this figure) that mate with slots in second guiding members <NUM> that form part of the second guiding means. The second guiding members <NUM> are fixed to the outer door panel <NUM>. Inner door stoppers <NUM> stop the sliding motion of the inner door panel <NUM> when it has reached the desired closed position.

The door assembly is assembled so that the inner and outer door panels can move in a concerted fashion as the door slides along guide rails <NUM>. Stoppers <NUM>, <NUM> provide limits for the movement of the inner door panel <NUM> along the torch box side (i.e. parallel to the torch box opening), while inner guides <NUM>, in particular slots <NUM> in the inner guides <NUM> and bearings <NUM> provide for the mechanism that forces the inner door panel <NUM> inwardly as the door is closed.

During use, the door assembly moves along guide rails <NUM> in a first direction, along an opening on a side wall of a torch box. As the door moves towards a closed position (from right to left in <FIG>), the inner door panel <NUM> will reach the inner door stoppers <NUM>. As a result, the inner door panel <NUM> can no longer move in the first direction, in front of the opening of the torch box, substantially perpendicular to the direction of access to the opening. Continued application of force to the door assembly, e.g. by application of force to handle <NUM> towards the closed position will apply force to the outer door panel <NUM> and attached slots <NUM> in guiding members <NUM>. Simultaneously, the bearings <NUM> that are fixed to the inner door panel will be forced to move along the slots <NUM>. As a consequence, the outer door panel <NUM> will continue to move along the torch box opening (in the first direction) and simultaneously, the inner door panel <NUM> will be forced in a second direction that is perpendicular to the first direction. When the outer door panel <NUM> has been moved so far that the bearings <NUM> have reached the end of the slots <NUM>, continued movement of the outer and inner door panels is prevented, and the door has reached a closed and locked position.

<FIG> shows a perspective view of the door assembly with the front shield <NUM> fixed to the outer door panel <NUM> and handle <NUM>. A window frame <NUM> is arranged in the outer door panel <NUM> (and the front shield <NUM>) to expose a window <NUM> arranged in the inner door panel <NUM> through which the plasma can be observed.

<FIG> shows details of the door assembly by removing from the figure the outer door panel <NUM>. The door assembly is here in a fully open position. The first direction of movement (opening/closing direction) is shown with an arrow X and the second direction, transverse direction, with an arrow Z. A first sliding mechanism is shown, comprising guide rails <NUM> and guide blocks <NUM> that can slide along the rails <NUM>. The guide blocks <NUM> are fastened to the outer door panel <NUM> (not shown in <FIG> for the sake of clarity) with screws <NUM>. The rails and guide blocks mate together such that the guide blocks can only move back and forth along the rails but cannot move transversely to the sliding direction, up from the guide rails. The guide rails <NUM> are fastened either to a front surface of the ICP torch box (the surface with the opening of the torch box which the door assembly is to close and open) or onto a door frame <NUM> which is fastened to the front surface of the torch box. A pair of parallel second guiding members <NUM> are shown which are fixed with screws <NUM> to the outer door panel <NUM> (not shown in this figure). Support members <NUM> are fixed to the inner door panel <NUM>. At the ends of the support members <NUM> bearings <NUM> are attached that mate with guiding slots <NUM> of the second guiding members <NUM>. When the door is moved towards a closed position, by pushing the handle <NUM> in the first direction, the outer door panel <NUM> moves with the handle (as these are connected) and the inner door panel <NUM> moves along as the slots <NUM> pull the bearings <NUM> that are fixedly arranged to the inner door panel <NUM> via the support members <NUM>. The inner door panel <NUM> will eventually meet inner door stoppers <NUM> (which may also be referred to as inner stoppers) and cannot move further. If the handle is pushed further, the outer door panel <NUM> will move further along with its fixed second guiding members <NUM>, thus the slots <NUM> move also in the longitudinal direction and due to the shape of the slots <NUM>, the bearings <NUM> are forced inwardly (towards the torch box opening) until they reach the ends of the slots <NUM>. The inner door panel <NUM> moves with the bearings <NUM> and is thus pressed inwardly towards the door frame <NUM> of the torch box.

At the closing ends of the slots <NUM>, the bearings <NUM> may lock into a groove (<NUM> in <FIG>) of the slot <NUM>, if such grooves or other means are provided to define an end position of the bearings <NUM>. In general, end position defining surfaces may be provided, which may be constituted by a groove and/or at least one ridge, and which may assist the bearings <NUM> in reaching a stable predetermined end position.

Springs <NUM> are arranged in between the inner and outer door panels. These springs <NUM> exert a force pulling back the door from an almost closed position (if the bearings <NUM> have not reached the grooves or edges in the slots to come into a defined closed position). The springs <NUM> thus aid in providing a movement of the bearings <NUM> such that the door will not be left in an almost but not fully closed position.

The closed and "locked" position is shown in <FIG> (also in this figure the outer door panel <NUM> is not shown, for purpose of clarity). The handle <NUM> has been moved all the way until first the inner door panel <NUM> hits the inner stoppers <NUM> and then further, pulling the outer door panel with the fixed second guiding members <NUM> such that the slots <NUM> move in the closing direction and the bearings <NUM> remain put in this direction (as the inner door panel cannot move further) but the bearings <NUM> are forced inwardly as the slots <NUM> move, until the bearings <NUM> meet the closing ends of the slots. At the closing ends the slots <NUM> may have a slight groove and/or recess which is arranged such that the bearings <NUM> can move slightly outwards to rest against the end position defining surfaces.

As the bearings <NUM> approach the edge point (point P in <FIG>) of the slots <NUM> during the closing motion, the point after which the bearings rest against the end position defining surfaces, which may comprise a groove or recess, the sealing <NUM> on the inner door frame is being compressed against the door frame <NUM>. As the bearings fall into the grooves the pressure is slightly released as the bearings move slightly outwardly (away from the torch box). In order to move the door in the opposite direction to open it again, the bearings have to move back over the point of higher pressure (the edge point P in <FIG>), and this creates a locking position of the door, as the bearings <NUM> rests in the grooves or recess of the slots <NUM>. The edge points (P in <FIG>) of the grooves or recesses <NUM> are shaped suitably sharp to provide a haptic click-sensation as the door reaches the locked position.

The slots <NUM> are shaped to have a general tilted main direction relative to the opening/closing moving direction of the door. This forces the bearings <NUM> (and inner door panel <NUM>) inwardly as the door is moved to the second closed position and outwardly when the door is opened from the second closed position to the first closed position. The angle of the slots <NUM> can have a gradient, meaning that in the closing motion, the angle gradually decreases, to compensate for the increased pressure needed as the door is moved further and the sealing is being pressed. Thus, per unit of distance in the X-direction (main opening/closing direction of the door, see <FIG>) the movement in the Z-direction (transverse direction) is reduced, to reduce the force needed for the closing motion.

<FIG> shows a close-up view of one of the slots <NUM>. In this embodiment the inclination of the slot varies substantially stepwise. On the right-hand side is the opening end of the slot <NUM>, where the bearing <NUM> is located when the door is open. When the bearing <NUM> is positioned in the opening end, the spacing between the inner door panel <NUM> and the outer door panel <NUM> is at its minimum and there is no pressure applied by the sealing <NUM> against the door frame <NUM> or any other surface (the sealing <NUM> does not touch or barely touches the door frame <NUM> when the bearing <NUM> is in this position). As the bearing <NUM> moves from the opening end towards the opposite closing end, it passes point O, at which point the sealing <NUM> may touch the door frame <NUM>. Beyond this point O the inclination of the slope of the slot <NUM> is smaller such that the transverse movement of the inner door panel <NUM> is less per unit of movement of the outer door panel <NUM>. As the outer door panel <NUM> (and the slot <NUM> thereby) is pushed further, moving the bearing relative to the slot from point O towards point P, the sealing <NUM> is more compressed and the force required to move the door incrementally increases. Then, as the bearing <NUM> reaches point P, the sealing pressure is at its maximum, and as the bearing <NUM> moves beyond point P the sealing pressure is slightly reduced as beyond the point P the inclination of the slope of the slot <NUM> is reversed, thus slightly decreasing the spacing between the inner door panel <NUM> and the outer door panel <NUM>.

<FIG> shows a door frame <NUM> of the door assembly onto which the rails <NUM> (not shown) and internal stoppers <NUM> are to be mounted. The door frame <NUM> can be provided as a separate component to be attached to a torch box. Alternatively, the door frame can be internal to the torch box, so that the additional door assembly components can be attached directly to the torch box.

<FIG> shows an alternative embodiment of the door assembly (shown with the outer door panel removed), with differently shaped slots <NUM> and a stopping panel <NUM> serving the role as a stopper for door movement along the torch box opening. Two second guiding members <NUM> (one is shown transparent for clarification) are fastened on the outer door panel (not shown) and have guiding slots <NUM>. Support members <NUM> are mounted on the inner door panel <NUM>, these support members <NUM> are provided with bearings <NUM> that interact with the slots <NUM>. The slots <NUM> have a groove <NUM> into which the bearings <NUM> lock in a second closed position of the door. In this embodiment the inner door panel <NUM> has depressions <NUM> for receiving parts of the second guiding members <NUM> when the door panels are closer together (in an open position). Two grooves <NUM>, <NUM> circumscribe the opening of the door frame <NUM>. These grooves <NUM>, <NUM> are designed for receiving sealings (not shown) that create a seal between the door frame <NUM> and the door.

This embodiment therefore also provides a two-step closing mechanism of the torch box door assembly, by movement in a first direction, along the torch box opening, and by movement in a second direction, that forces the inner door panel towards the torch box, providing a seal between the closed door and the torch box.

In <FIG>, there is shown a schematic view of a torch box having a sliding door in accordance with the invention. An axial and a radial viewer <NUM>, <NUM> of an ICP emission spectrometer are shown in dotted lines, indicating that the torch box can be configured as a single or dual view instrument. It will be understood that a torch can be mounted horizontally or vertically in the torch box.

In <FIG> there is shown a torch box <NUM> and a sliding door assembly <NUM>, with the door being in an open position, showing the access opening <NUM> of the torch box <NUM>. Only the front shield <NUM>, handle <NUM>, window frame <NUM> and window <NUM> of the door assembly <NUM> can be seen in this view, together with parts of guide rails <NUM> and inner door stopper <NUM>.

In <FIG>, the door assembly <NUM> is shown in a closed position, exposing parts of guide rails <NUM> and outer door stoppers <NUM>. During use, the plasma torch can be viewed through the window <NUM>, allowing for inspection of the plasma torch without opening the torch box.

As is schematically shown in <FIG>, the door assembly <NUM> allows complete or almost complete access to the opening <NUM> in the torch box, as is also shown in <FIG> & <FIG>. That is, the door assembly <NUM> allows close to <NUM>% of the opening <NUM> to be accessed, preferably at least <NUM>%, more preferably at least <NUM>%. The entire opening <NUM> is preferably closed off using a single door, however, the use of two doors can also be envisaged. Conversely, a single door could be used to close off two (or more) openings. If the torch box <NUM> comprises two or more openings that require temporary closing, a separate sliding door for each opening is preferred.

As used herein, including in the claims, singular forms of terms are to be construed as also including the plural form and vice versa, unless the context indicates otherwise. Thus, it should be noted that as used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

Throughout the description and claims, the terms "comprise", "including", "having", and "contain" and their variations should be understood as meaning "including but not limited to" and are not intended to exclude other components.

The present invention also covers the exact terms, features, values and ranges etc. in case these terms, features, values and ranges etc. are used in conjunction with terms such as about, around, generally, substantially, essentially, at least etc. (i.e., "about <NUM>" shall also cover exactly <NUM> or "substantially constant" shall also cover exactly constant).

The term "at least one" should be understood as meaning "one or more", and therefore includes both embodiments that include one or multiple components. Furthermore, dependent claims that refer to independent claims that describe features with "at least one" have the same meaning, both when the feature is referred to as "the" and "the at least one".

It will be appreciated that variations to the foregoing embodiments of the invention can be made while still falling within the scope of the invention. Features disclosed in the specification, unless stated otherwise, can be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless stated otherwise, each feature disclosed represents one example of a generic series of equivalent or similar features.

Use of exemplary language, such as "for instance", "such as", "for example" and the like, is merely intended to better illustrate the invention and does not indicate a limitation on the scope of the invention unless so claimed. Any steps described in the specification may be performed in any order or simultaneously, unless the context clearly indicates otherwise.

Claim 1:
A sliding door assembly (<NUM>) for use with an inductively coupled plasma torch box (<NUM>), the door assembly comprising a door and a guiding mechanism for allowing a movement of the door in a first direction (X) along an opening (<NUM>) of a torch box so as to allow opening and closing the torch box, and in a second direction (Z), substantially perpendicular to the first direction, so as to move the door or at least a part thereof towards the opening when closing the torch box, wherein the door comprises an inner door panel (<NUM>) and an outer door panel (<NUM>), wherein the outer door panel (<NUM>) is engaged with a first sliding mechanism, for allowing movement of the door in the first direction and wherein the inner door panel and the outer door panel are interconnected via a second sliding mechanism so that the inner door panel is moved by the outer door panel and allowing movement of the inner door panel (<NUM>) in both the first and the second direction,
wherein the second sliding mechanism is provided by at least a pair of parallel inner guide members (<NUM>) that are arranged substantially in the first direction between the inner and outer door panels, and at least two pairs of bearings (<NUM>) that interconnect with the inner guide members (<NUM>), where said inner guide members (<NUM>) are fastened to either of the inner and outer door panels, and said bearings are mounted on support fastened to the other of said inner and outer door panels.