The invention relates to an absorption spectrometer. Conventional spectrometers for measuring liquid samples make use of cuvettes. The cuvettes with the liquid samples are placed within the spectrometer prior to measurement and are removed after the measurement. The cuvettes have different optical path lengths for the liquid sample; typical values are 1 cm or 100 μηα. The user chooses the optical path length of the cuvettes depending on the absorption properties of the liquid sample. For a sample with a high absorption the user chooses a short optical path length and for a sample with low absorption the user chooses a long optical path length. However, when using small optical path lengths for the liquid sample the cuvettes are difficult to clean .

It is therefore an obj ect of the invention to provide a

spectrometer that is easy to clean .

The absorption spectrometer according to the invention

comprises a base, an arm and a bearing, wherein the base comprises a base window and one of a light source and a

detector, and the arm comprises an arm window and the other one of the light source and the detector, wherein the arm is pivotally mounted on the base by means of the bearing for rotating the arm relative to the base around a rotational axis that is substantially perpendicular to the windows into an open position of the arm in which the windows are separated such that they are accessible from outside and the arm can be moved by means of the bearing to a closed position of the arm in which a closed sample space between and confined by the windows is formed and light emitted by the light source can pass through the windows and the sample space and can impinge on the detector for measuring the absorption of a sample placed in the samp1e space . The absorption spectrometer according to invention can be used for measuring the absorption of a liquid sample. But it is also conceivable to measure a solid sample or a sample having a powder form. For performing the absorption measurement, the arm is moved to the open position of the arm and the sample is placed on the lower one of the two windows. The arm is then moved to the closed position of the arm and the absorption measurement is carried out . After the measurement the arm is moved again to the open position of the arm. The sample is then stuck to the two windows . Since in the open position of the arm the windows are accessible, they can advantageously be easily cleaned . For the cleaning a user can for example wipe a moist tissue manually over both windows . After cleaning the two windows another sample can be placed on the lower one of the two windows and another measurement can be performed .

It is preferred that the arm is supported by means of the bearing such that it can be moved in a direction substantially parallel to the rotational axis into the closed position of the arm. It is advantageously less likely that the windows are scratched when the arm is moved into the closed position of the arm by a translational movement in comparison to a rotational movement . The bearing preferably comprises a shaft that is fixed on the arm and that comprises a step, a bush that is attached to the base and in which the shaft is arranged for pivotally mounting the arm on the base and for supporting the arm such that it can be moved in the direction substantially parallel to the

rotational axis, and a biasing means that is supported on the inner side of a base housing of the base and on the step to biase the arm towards the base . Preferably, the biasing means comprises a spring, in particular a compression spring . The biasing means advantageously keeps the arm in the closed position of the arm and therefore keeps the samp1e space closed during the measurement . It is preferred that the absorption spectrometer comprises a locking mechanism that is adapted to lock the arm in the open position of the arm and in the closed position of the arm, wherein the arm can be unlocked by moving the arm in the direction substantially parallel to the rotational axis away from the base. The locking mechanism advantageously avoids a movement of the arm during the measurement and therefore also a difference in readings of the same sample is avoided .

Furthermore , the movement is avoided during the cleaning of the windows .

It is preferred that the locking mechanism comprises a sphere , a second biasing means and a first cylindrical hole that is arranged on one of the arm and the base , wherein the sphere is arranged within the first cylindrical hole that has

substantially the same diameter as the sphere so that the sphere can be displaced parallel to the rotational axis but substantially not perpendicular to the rotational axis and is biased by the second biasing means towards the other one of the a m and the base , wherein the locking mechanism further

comprises a second cylindrical hole that is arranged on the other one of the arm and the base , that has a diameter that is shorter than the diameter of the sphere and that is adapted to partially receive the sphere to lock the arm in the closed position of the arm. The sphere biased by the second biasing means together with the second cylindrical hole forms and interference fit that holds the arm and the base tight together in the closed position . The arm can therefore advantageously not move during performing an absorption measurement by the absorption spectrometer . Would the arm move during the

measurement, this would disadvantageously lead to an error for the absorption measurement . In particular, subsequent readings of the same sample would not be different . The locking

mechanism also allows a more accurate positioning of the emitter with respect to the detector each time the arm is opened and closed since the sphere settling into the cup negates any manufacturing tolerances which may allow the arm to wobble a little . This means if you take a reading open the arm close it again the reading will be closer to the original.

It is furthermore preferred that the second biasing means is adapted such that when the arm is moved away f om the base the biasing force acting on the sphere is so little that the sphere can be moved out of the second cylindrical hole by a rotation of the arm.

The locking mechanism preferably comprises a protrusion

protruding from the arm on a side facing towards the base, a first recess formed on the base on a side facing towards the arm and adapted to receive the protrusion to lock the arm in the closed position of the arm, and a second recess formed on the base on the side facing towards the arm and adapted to receive the protrusion to lock the arm in the open position of the arm.

It is preferred that the locking mechanism is adapted to block the rotation of the arm at a first end position of rotation that corresponds to the closed position of the arm and at a second end position of rotation that corresponds to the open position of the arm, wherein the arm can be locked by moving the arm from the first end position of rotation in the

direction substantially parallel to the rotational axis towards the base and by moving the arm from the second end position of rotation in the direction substantially parallel to the

rotational axis towards the base . The locking mechanism

preferably comprises a first flank formed on the base and adapted to block the protrusion to define the first end

position of rotation, and a second flank formed on the base and adapted to block the protrusion to define the second end position of rotation . It is preferred that the first flank is arranged flush with a side of the first recess and/or the second flank is arranged flush with a side of the second recess . It is preferred that the difference of the positions of the arm from the first end position of rotation to the second end point of rotation is substantially 90°. The step is preferably adapted to contact the bush when the arm is moved in the direction substantially parallel to the

rotational axis away from the base to block the movement of the arm away from the base so that the protrusion can be moved away from the base to a maximum distance from the base where the protrusion can still be blocked by the first flank and the second flank.

It is preferred that the base window is supported on a base housing of the base on an inner side of the base housing and extends over a through hole of the base housing, wherein the base housing is formed such that the through hole tapers towards the inside of the base and/or it is preferred that the arm window protrudes from the arm. The tapering through hole can advantageously be easily cleaned and it is unlikely that rests sample remains on the corners formed by the base window and the base housing. The protruding arm window can also be easily cleaned.

It is preferred that a base housing of the base comprises a platform on which the base window is arranged, and a concave surface arranged immediately adjacent to the platform. The concave surface advantageously avoids the formation of corners and therefore it is achieved that the base housing can be easily cleaned. Also the concave surface guides any liquids that spill out of the sample space in a preferred direction so that only certain parts of the base housing are contaminated by the liquid.

The base window is sealed with respect to the base housing and/or the arm window is sealed with respect to the arm

housing. It is therefore avoided that liquid samples can enter the inside of the base and/or the arm. It is preferred that the absorption spectrometer is adapted to be held in a hand. This makes it advantageously easier to clean the windows. The side of the arm facing away from the base is arranged flush with a side of the base. This avoids the

formation of edges and makes it more comfortable for the user to carry the absorption spectrometer.

It is preferred that the detector comprises a pyroelectric sensitive material, in particular lead-zirconate-titanate, the light source is adapted to emit light in the infrared

wavelength region and the windows are transparent for the light in the infrared wavelength region, wherein the windows in particular comprise calcium fluoride . In the following the invention is explained on the basis of schematic drawings .

Figure 1 shows a front view of an absorption spectrometer according to the invention with a closed position of an arm of the spectrometer,

Figure 2 shows the front view of the absorption spectrometer with an open position of the arm, Figure 3 shows a side view of the absorption spectrometer,

Figure 4 shows a sectional view of line A-A of Figure 1 ,

Figure 5 shows a sectional view of line B-B of Figure 1 ,

Figure 6 shows a sectional view of line C-C of Figure 1,

Figure 7 shows a sectional view of line D-D of Figure 2, Figure 8 shows a sectional view of line E-E of Figure 2 ,

Figure 9 shows a sectional view of line F-F of Figure 2 , Figure 10 shows a sectional view of line A-A of Figure 1 for an alternative absorption spectrometer according to the invention, and Fiqure 11 shows a sectional view of line F-F of Figure 2 for the alternative absorption spectrometer according to the invention .

As it can be seen in Figures 1 to 9 an absorption spectrometer 1 comprises a base 2 and an arm 3. Figures 1 to 3 show that the base 2 comprises a control element 4 for controlling an

absorption measurement and a display 5 in particular for reading out a result of the absorption measurement . As it can be seen i the Figures , the base 2 comprises a base housing 11, a base window 7 arranged on the base housing 11 and a detector 10 arranged inside the base housing 11. The arm 3 comprises an arm housing 12 , an arm window 8 arranged on the arm housing 12 and a light source 9 arranged inside the arm housing 12. It is also conceivable to arrange the light source 9 in the base housing 11 and the detector 10 in the arm housing 12.

The absorption spectrometer 1 furthermore comprises a bearing 22. The arm 3 is pivotally mounted on the base 2 by means of the bearing 22 for rotating the arm 3 relative to the base 2 around a rotational axis 21 that is substantially perpendicular to the windows 7, 8. This means also that the windows 7, 8 are substantially parallel to each other . The arm 3 can be rotated into an open position of the arm 3 in which the windows 7, 8 are separated such that they are accessible from outside for cleaning purposes . Furthermore , the arm 3 can be moved by means of the bearing 22 to a closed position of the arm 3 in which a closed sample space 20 between and confined by the windows 7, 8 is formed. Figures 1 , 3 and 4 to 6 show the absorption

spectrometer 1 with the arm 3 in its closed position, whereas Figures 2 and 7 to 9 show the absorption spectrometer 1 with the arm 3 in its open position . As it can be seen in Figure 4, when the arm 3 is in its closed position, light emitted by the light source 9 can pass through the windows 7, 8 and the sample space 20 and can impinge on the detector 10 for measuring the absorption of a sample placed in the sample space 20. The absorption spectrometer 1 according to the Figures comprises four detectors 10, two being arranged behind the plane of Figure 4 and two being arranged in front of the plane of Figure 4. Each detector 10 comprises a respective wavelength filter for letting pass a different part of the spectrum of the light emitted by the light source 9. However, it is also conceivable to use a lower or higher number of the detectors 10. Alternatively, it is conceivable to use a

detector 10 with a row or a two-dimensional array of photo elements and a linear variable filter for letting pass

different parts of the spectrum of the light emitted by the light source 9.

It is conceivable that the detectors 10 comprises a

pyroelectric sensitive material , in particular lead-zirconate- titanate (PZT) , the light source 9 is adapted to emit light in the infrared wavelength region and the windows 7, 8 comprise calcium fluoride so that the windows 7, 8 are transparent for the light in the infrared wavelength region . Figures 4 and 6 to 8 show that the arm 3 is supported by means of the bearing 22 such that it can be moved in a direction substantially parallel to the rotational axis 21 into the closed position of the arm 3. The bearing 22 comprises a shaft 13 , a step 15 , a bush 16 and a biasing means 14. The shaft 13 is fixed on the arm 3 on its one longitudinal end and comprises a step 15 on its other longitudinal end. The step 15 can for example be formed by a collar . The bush 16 is attached to the base housing 11 and the shaft 13 is arranged for pivotally mounting the arm 3 on the base 2 and for supporting the arm 3 such that it can be moved in the direction substantially parallel to the rotational axis 21 inside the bush 16. The biasing means 14 is supported on its one longitudinal end on the inner side of the base housing 11 - and on its other longitudinal end on the step 15 to biase the arm 3 towards the base 2. The biasing means 14 is a compression spring .

As it can be seen in Figures 5 and 9, the absorption

spectrometer 1 comprises a locking mechanism 25 that is adapted to lock the arm 3 in the open position of the arm 3 and in the closed position of the arm 3. The arm 3 can be unlocked by moving the arm 3 in the direction substantially parallel to the rotational axis 21 away from the base 2. The locking mechanism 25 comprises a protrusion 17 protruding from the arm 3 on a side facing towards the base 2, a first recess 18 formed on the base 2 on a side facing towards the arm 3 and a second recess 19 formed on the base 2 on the side facing towards the arm 3. The first recess 18 is adapted to receive the protrusion 17 to lock the arm 3 in the closed position of the arm 3, and the second recess 19 is adapted to receive the protrusion 17 to lock the arm 3 in the open position of the arm 3.

The locking mechanism 25 is further adapted to block the rotation of the arm 3 at a first end position of rotation that corresponds to the closed position of the arm 3 and at a second end position of rotation that corresponds to the open position of the arm 3. The arm 3 can be locked by moving the arm 3 from the first end position of rotation in the direction

substantially parallel to the rotational axis 21 towards the base 3 and by moving the arm 3 from the second end position of rotation in the direction substantially parallel to the

rotational axis 21 towards the base 3. For blocking the

rotation of the arm 3 the locking mechanism 25 comprises a first flank 23 formed on the base 2 and adapted to block the protrusion 17 to define the first end position of rotation, and a second flank 24 formed on the base 2 and adapted to block the protrusion 17 to define the second end position of rotation . As it can be seen in Figure 5 , the first flank 23 is arranged flush with a side of the first recess 18 and Figure 9 shows that the second flank 24 is arranged flush with a side of the second recess 19. As it can be seen in Figures 1 and 2 the difference of the positions of the arm 3 from the first end position of rotation to the second end position of rotation is substantially 90°.

Figures 4 and 6 to 8 show that the step 15 is adapted to contact the bush 16 when the arm 3 is moved in the direction substantially parallel to the rotational axis 21 away from the base 2 to block the movement of the arm 3 away from the base 2 so that the protrusion 17 can be moved away from the base 2 to a maximum distance from the base 2 where the protrusion 17 can still be blocked by the first flank 23 and the second flank 24, In order to achieve this, in the closed position of the arm 3, the axial distance from the step 15 to the bush 16 is shorter than the axial distance from the end of the protrusion 17 facing towards the base 2 to the end of the first flank 23 facing towards the arm 3 as well as to the end of the second flank 24 facing towards the arm 3.

In particular Figure 7 shows that the base housing 11 comprises a through hole 28 and the base window 7 is supported on the base housing 11 on inner side thereof and extends over the through hole 28. The base housing 11 comprises bevelled edges

27 that confine the through hole 28 such that the through hole

28 tapers towards the inside of the base 2. Figures 4 and 8 show that the arm 3 comprises a frame 29 that protrudes from the arm 3. The arm window 8 is arranged inside the frame 29 and protrudes from the frame 29. The base window 7 is sealed with respect to the base housing ll _f in particular by means of a sealing and/or by means of a glue that attaches the base window

7 to the base housing 11. The arm window 8 is sealed with respect to the arm housing 12, in particular by means of a sealing and/or by means of a glue that attaches the arm window

8 to the arm housing 12.

As it can be seen in particular in Figures 3, 6 and 8 the base housing 11 comprises a platform 26 that has a planar outer surface and on which the base window 7 is arranged. The base housing 11 comprises a concave surface 6 arranged immediately adjacent to the platform 26. The absorption spectrometer 1 is adapted to be held in a hand. As it can be seen in Figure 3 the side of the arm 3 facing away from the base 2 is arranged flush with a side of the base 2.

The alternative absorption spectrometer 1 according to Figures 10 and 11 differ from the absorption spectrometer according to Figures 1 to 9 in that the locking mechanism 25 of the

alternative absorption spectrometer 1 additionally comprises a sphere 30, a second biasing means 31 and a first cylindrical hole 32 that is arranged on the arm 3. The axis of the first cylindrical hole 32 is substantially parallel to the rotational axis 21. The sphere 30 is arranged within the first cylindrical hole 32 that has substantially the same diameter as the sphere 30 so that the sphere 30 can be displaced parallel to the rotational axis 21 but substantially not perpendicular to the rotational axis 21. The second biasing means 31 is supported on its one end on the arm 3 and on its other end on the sphere 30, so that the sphere 30 is biased by the second biasing means 31 towards the base 2.

The locking mechanism 25 further comprises a second cylindrical hole 33 that is arranged on the base 2. The axis of the second cylindrical hole 33 is substantially parallel to the rotational axis 21. The second cylindrical hole 33 has a diameter that is shorter than the diameter of the sphere 30 and is adapted to partially receive the sphere 30 to lock the arm 3 in the closed position of the arm 3. As it can be seen in Figure 10, the diameter of the second cylindrical hole 33 and the distance between the first cylindrical hole 32 and the second

cylindrical hole 33 in the closed position of the arm 3 are chosen such that in the closed position of the arm, when the sphere 30 is received by the second cylindrical hole 33, more than half the sphere 30 is still arranged within the first cylindrical hole 32. It is therefore advantageously achieved that the sphere 30 can not move in a direction perpendicular to the rotational axis 21 and the arm 3 is held tightly with respect to the base 2 in the closed position of the arm 2. The second biasing means 31 is adapted such that when the arm. 3 is moved away from the base 2 the biasing force acting on the sphere 30 is so little that the sphere 30 can be moved out of the second cylindrical hole 33 by a rotation of the arm 3.

Figure 11 shows that the locking mechanism 25 further comprises a third cylindrical hole 34 that is arranged on the base 2. The axis of the third cylindrical hole 34 is substantially parallel to the rotational axis 21. The third cylindrical hole 34 has the same diameter as the second cylindrical hole 33 and is adapted to partially receive the sphere 30 to lock the arm 3 in the open position of the arm 3. The distance between the first cylindrical hole 32 and the third cylindrical hole 34 in the open position of the arm 3 is the same as the distance between the first cylindrical hole 32 and the second cylindrical hole 33 in the closed position of the arm 3 , so that in the open position of the arm, when the sphere 30 is received by the third cylindrical hole 33 , more than half the sphere 30 is still arranged within the first cylindrical hole 32. It is therefore advantageously achieved that the sphere 30 can not move in a direction perpendicular to the rotational axis 21 and the arm 3 is held tightly with respect to the base 2 in the open position of the arm 2.

List of reference signs

1 absorption spectrometer

2 base

3 arm

4 control element

5 display

6 concave surface

7 base window

8 arm window

9 light source

10 detector

11 base housing

12 arm housing

13 shaft

14 biasing means

15 step

16 bush

17 protrusion

18 first recess

19 second recess

20 sample space

21 rotational axis

22 bearing

23 first flank

24 second flank

25 locking mechanism

26 platform

27 bevelled edge

28 through hole

29 frame

30 sphere

31 second biasing means

32 first cylindrical hole 33 second cylindrical hole

33 third cylindrical hole