GB1582257A

GB1582257A - Sampling cell for spectroscopy

Info

Publication number: GB1582257A
Application number: GB33698/76A
Authority: GB
Original assignee: BECKMAN RIIC Ltd
Current assignee: BECKMAN RIIC Ltd
Priority date: 1977-08-23
Filing date: 1977-08-23
Publication date: 1981-01-07

Description

(54) SAMPLING CELL FOR SPECTROSCOPY (71) We, BECKMANN-RIIC LIMITED, a British Company of Eastfield Industrial Estate, Glenrothes, Fife, Scotland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to sampling cells for use with spectrophotometers, especially infrared spectrophotometers.

Such sampling cells generally include a pair of windows between which a sample can be introduced and through which electromagnetic radiation can be passed.

It has previously been proposed for the cell to be held together in its assembled form by means of a top plate clamped and located by locating bolts which pass through the top plate. Removal and replacement of windows, however, can prove troublesome with this form of cell.

The invention provides a sampling cell comprising a support, a pair of spaced-apart body members positioned on opposed sides of the support and defining two parallel surfaces for locating parts therebetween, a stack positioned adjacent to the support and comprising a plate and a pair of windows, the plate having an aperture therein for the passage of electromagnetic radiation and being at least partly positioned between the locating surfaces and the pair of windows each being positioned between the locating surfaces with a pair of opposed sides in contact with the locating surfaces and located in the stack between the plate and the support, and clamping means for applying a force to the plate to clamp the windows in position against the support, the windows and the plate being located against movement perpendicular to the locating surfaces and in the plane of the windows but being permitted, when not clamped, to move parallel to the locating surfaces in the plane of the windows, The fact that the plate is located by the body members enables the need for clamping bolts passing through the plate to be obviated, which in turn makes for much easier removal and replacement of the windows: the latter can be achieved simply by loosening the clamping means and sliding the plate and windows parallel to the locating surfaces until they are clear of the body members.

Advantageously, an end stop is provided at one end of a body member for locating the windows and plate against movement parallel to the locating surfaces in the plane of the windows. Thus, accurate assembly of the parts of the cell is achieved simply by sliding those parts between the locating surfaces until they meet the end stop. The end stop may, for example, be a plate rivetted onto one end of one of the body members.

Advantageously, the clamping means consists of a plurality of bolts which extend into threaded holes in the body members and the heads of which bear against the plate. This provides an inexpensive and convenient form of clamping means.

Advantageously, the body members form the arms of a U-shaped mass of metal, the base of which supports the windows and is apertured for the passage of radiation. Such a design gives good heat transfer between the windows and the U-shaped mass of metal; if desired means for heating or cooling the mass of metal may be provided. The U-shape also has the advantage that it lends itself well to extrusion which provides accurate yet inexpensive manufacture.

The windows are advantageously rectangular.

The cell may be a mull cell, in which a paste is sandwiched between the windows. Alternatively, the cell may be adapted for liquid or gaseous samples. Thus, a spacer (for example, of P.T.F.E or lead) may be provided between the windows defining a region into which the sample can be introduced, and one or both windows may be provided with passageways through which the sample may be introduced.

Advantageously, the window nearer the top plate is provided with a pair of passageways communicating with the centre of the spacer and the top plate has a pair of filling ports in register with the passageways. The construction of cell according to the invention is of particular advantage with the latter design of cell, since accurate alignment of different parts is particularly necessary. The construction of cell according to the invention also facilitates changing from a cell adapted for examining one form of sample to another form, and for changing windows of one material for those of another.

A sampling cell constructed in accordance with the invention will now be described, by way of example, with reference to the drawings accompanying the Provisional Specification in which: Figure 1 is a plan view of the cell; Figure 2 is a section taken on the lines 2-2 of Figure 1; and Figure 3 is a side view, partly in section, of the cell in disassembled state.

Referring to the drawings, the sampling cell comprises a pair of windows 1, 2 positioned between a pair of spaced-apart body members 3 which are formed by the arms of a U-shaped member, indicated generally by the reference numeral 4. The window 1, 2, cushioned by a rubber washer 5, rest on the base 6 of the Ushaped member, and a plate 7 is positioned on top of the windows with a gasket 8 in between.

The base 6, the top plate 7, the washer 5 and the gasket 8, are all formed with a rectangular apertures to allow the passage of radiation therethrough. Clamping bolts 9, the heads of which bear on the top plate 7, hold the assembly together.

The interior of the cell is defined by a thin spacer 10 which is located between the win dows 1, 2. The aperture in the spacer has two parallel sides 11 extending along the length of the cell, and tapers at each end to points on the centre-line of the cell. The window 1 has two passageways 12 therein which communicate with the interior of the spacer in the tapering regions, and the top plate 7 is provided with two filling ports 13 in register therewith. The top plate 7 and the gasket 8 both have suitable apertures to provide communication between the filling ports 13 and the passageways 12.

An end stop is formed by a plate 14 rivetted onto the end of an arm of the U-shaped member4.

The U-shaped member 4 is secured by bolts 15 to an apertured holder plate 16, which is of a standard size to fit into conventional spectrophotomers. For simplicity, the clamping bolts 9 are in line with the bolts 15, so that three threaded holes through the U-shaped member 4 serve for both sets of bolts. The Ushaped member is of extruded aluminium. The sides 17 of the arms of the U-shaped member which face each other are parallel.

The windows 1, 2, the top plate 7, and gasket 8 and washer 5 all contract the surfaces 17 of the U-shaped member 4, and are thus located against movement perpendicular to the surfaces 17. When the clamping bolts 9 are loosened, however, all these parts are free to slide in a direction parallel to the surfaces 17 in the plane of the windows (away from the end stop 14) The windows 1, 2, gasket 8, and top plate 7 can thus be easily removed. Further, the windows 1, 2 need only be touched over their end surfaces, for example, between thumb and forefinger, in this process. Since the windows of sampling cells are often forward of a material that is damaged by moisture from the hands, the facts that the area handled is kept to a minimum, and is only on the edge of the windows, is important. Re-assembly of the cell is equally easy.The windows 1, 2, gasket 8, and top plate 7 are stacked together, grasped at the ends between thumb and forefinger, and slid between the surfaces 17 until they meet the end stop 14. In this way, all the passageways for communicating with the interior of the cell will be aligned. (If desired, the parts can be of course be slid in separately). The clamping bolts 9 are then tightened and assembly is complete.

The easy removal and replacement of the windows makes it easy to change the type of the cell. Thus, initially, the spacer 10 may be of polytetrafluoroethylene, the cell being a semipermanent cell. This spacer may then be replaced by one of lead, when the cell is a sealed cell. Instead a special spacer may be used for examination of a paste sample, or the spacer may be omitted altogether for this purpose. In such a case when a paste sample is used and the filling ports 13 will not be utilized, the gasket 8 may be replaced by one that does not have apertures in line with the filling ports so as to seal off the filling ports.

Means for heating or cooling the U-shaped member 4 may be provided.

The aperture of the cell is smaller than hitherto since modern infra-red spectrophotometers have a smaller aperture at the sampling position. The compact window clamping design and smaller aperture enables a reduction of size of, and therefore cost of, the windows.

WHAT WE CLAIM IS: 1. A sampling cell comprising a support, a pair of spaced-apart body members positioned on opposed sides of the support and defining two parallel surfaces for locating parts therebetween, a stack positioned adjacent to the support and comprising a plate and a pair of windows, the plate having an aperture therein for the passage of electromagnetic radiation and being at least partly positioned between the locating surfaces and the pair of windows each being positioned between the locating surfaces with a pair of opposed sides in contact with the locating surfaces and located in the stack between the plate and the support, and clamping means for applying a force to the plate to clamp the windows in position against the support, the windows and the plate being located against movement perpendicular to the locating surfaces and in the plane of the windows but being permitted, when not clamped, to move parallel to the locating surfaces in the plane of the windows.

2. A cell as claimed in claim 1, wherein an end step is provided at one end of a body member for locating the windows and plate against movement parallel to the locating surfaces in the plane of the windows.

3. A cell as claimed in claim 1 or claim 2, wherein the clamping means consists of a plurality of bolts which extend into threaded holes

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. with the invention will now be described, by way of example, with reference to the drawings accompanying the Provisional Specification in which: Figure 1 is a plan view of the cell; Figure 2 is a section taken on the lines 2-2 of Figure 1; and Figure 3 is a side view, partly in section, of the cell in disassembled state. Referring to the drawings, the sampling cell comprises a pair of windows 1, 2 positioned between a pair of spaced-apart body members 3 which are formed by the arms of a U-shaped member, indicated generally by the reference numeral 4. The window 1, 2, cushioned by a rubber washer 5, rest on the base 6 of the Ushaped member, and a plate 7 is positioned on top of the windows with a gasket 8 in between. The base 6, the top plate 7, the washer 5 and the gasket 8, are all formed with a rectangular apertures to allow the passage of radiation therethrough. Clamping bolts 9, the heads of which bear on the top plate 7, hold the assembly together. The interior of the cell is defined by a thin spacer 10 which is located between the win dows 1, 2. The aperture in the spacer has two parallel sides 11 extending along the length of the cell, and tapers at each end to points on the centre-line of the cell. The window 1 has two passageways 12 therein which communicate with the interior of the spacer in the tapering regions, and the top plate 7 is provided with two filling ports 13 in register therewith. The top plate 7 and the gasket 8 both have suitable apertures to provide communication between the filling ports 13 and the passageways 12. An end stop is formed by a plate 14 rivetted onto the end of an arm of the U-shaped member4. The U-shaped member 4 is secured by bolts 15 to an apertured holder plate 16, which is of a standard size to fit into conventional spectrophotomers. For simplicity, the clamping bolts 9 are in line with the bolts 15, so that three threaded holes through the U-shaped member 4 serve for both sets of bolts. The Ushaped member is of extruded aluminium. The sides 17 of the arms of the U-shaped member which face each other are parallel. The windows 1, 2, the top plate 7, and gasket 8 and washer 5 all contract the surfaces 17 of the U-shaped member 4, and are thus located against movement perpendicular to the surfaces 17. When the clamping bolts 9 are loosened, however, all these parts are free to slide in a direction parallel to the surfaces 17 in the plane of the windows (away from the end stop 14) The windows 1, 2, gasket 8, and top plate 7 can thus be easily removed. Further, the windows 1, 2 need only be touched over their end surfaces, for example, between thumb and forefinger, in this process. Since the windows of sampling cells are often forward of a material that is damaged by moisture from the hands, the facts that the area handled is kept to a minimum, and is only on the edge of the windows, is important. Re-assembly of the cell is equally easy.The windows 1, 2, gasket 8, and top plate 7 are stacked together, grasped at the ends between thumb and forefinger, and slid between the surfaces 17 until they meet the end stop 14. In this way, all the passageways for communicating with the interior of the cell will be aligned. (If desired, the parts can be of course be slid in separately). The clamping bolts 9 are then tightened and assembly is complete. The easy removal and replacement of the windows makes it easy to change the type of the cell. Thus, initially, the spacer 10 may be of polytetrafluoroethylene, the cell being a semipermanent cell. This spacer may then be replaced by one of lead, when the cell is a sealed cell. Instead a special spacer may be used for examination of a paste sample, or the spacer may be omitted altogether for this purpose. In such a case when a paste sample is used and the filling ports 13 will not be utilized, the gasket 8 may be replaced by one that does not have apertures in line with the filling ports so as to seal off the filling ports. Means for heating or cooling the U-shaped member 4 may be provided. The aperture of the cell is smaller than hitherto since modern infra-red spectrophotometers have a smaller aperture at the sampling position. The compact window clamping design and smaller aperture enables a reduction of size of, and therefore cost of, the windows. WHAT WE CLAIM IS:

1. A sampling cell comprising a support, a pair of spaced-apart body members positioned on opposed sides of the support and defining two parallel surfaces for locating parts therebetween, a stack positioned adjacent to the support and comprising a plate and a pair of windows, the plate having an aperture therein for the passage of electromagnetic radiation and being at least partly positioned between the locating surfaces and the pair of windows each being positioned between the locating surfaces with a pair of opposed sides in contact with the locating surfaces and located in the stack between the plate and the support, and clamping means for applying a force to the plate to clamp the windows in position against the support, the windows and the plate being located against movement perpendicular to the locating surfaces and in the plane of the windows but being permitted, when not clamped, to move parallel to the locating surfaces in the plane of the windows.

in the body members and the heads of which bear against the plate.

4. A cell as claimed in any one of claims 1 to 3, wherein the body members form the arms of a U-shaped mass of metal, the base of which supports the windows and is apertured for the passage of radiation.

5. A cell as claimed in any one of claims 1 to 4, wherein the cell is a mull cell.

6. A cell as claimed in any one of claims 1 to 4, wherein a spacer is provided abetween the windows defining a region into which a sample may be introduced, and one of both windows is provided with passageways through which the sample may be introduced.

7. A cell as claimed in claim 6, wherein the window nearer the plate is provided with a pair of passageways communicating with the centre of the spacer, and the plate has a pair of filling ports in register with the passageways.

8. A cell substantially as hereinbefore described with reference to, and as shown in, the drawings accompanying the Provisional Specification.