GB2480303A

GB2480303A - Window unit

Info

Publication number: GB2480303A
Application number: GB1007981A
Authority: GB
Inventors: Robert Steven Drohan
Original assignee: Intastop Ltd
Current assignee: Intastop Ltd
Priority date: 2010-05-13
Filing date: 2010-05-13
Publication date: 2011-11-16
Anticipated expiration: 2030-05-13
Also published as: GB2480303B; GB201007981D0

Abstract

A window unit comprising a first sheet 301, a second sheet (304 Fig 7), an obscuring element 305 positioned between the first and second sheets and a cam 511. The first sheet defines first transparent regions 302A and first non-transparent regions 303A, and the second sheet comprises a transparent material arranged substantially parallel to the first sheet. The obscuring element 305 defines second transparent regions (306A Fig 3) and second non-transparent regions 307A and is arranged to slide with respect to the first sheet. The cam 511 is slidable along a first direction and has a first cam surface (510 Fig 9) configured to push the obscuring element along a different second direction when the cam is pushed in the first direction. The cam may have sloping surfaces and a plateau that engage with corresponding surfaces on the obscuring element. In a first position a person can see through the window (Fig 10a) whereas in a second position the window is opaque and viewing is not permitted (Fig 10c).

Description

Window Unit

CROSS REFERENCE TO RELATED APPLICATIONS

This application represents the first application for a patent directed towards the invention and the subject matter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a window unit, and a door comprising such a window unit.

2. Description of the Related Art

In locations such as hospitals, it is known to have doors with windows that contain a mechanism allowing vision through the window to be temporarily obscured and so provide privacy. One such type of window comprises a pair of static outer panes and a slidable third pane sandwiched between the outer pair. The third pane and one of the outer panes are each provided with a series of horizontal opaque stripes. The third pane is moveable to a position in which its opaque stripes are aligned with those of the outer pane to allow viewing through the window, and moveable to a second position in which its opaque stripes are aligned with transparent stripes of the outer pane to prevent viewing through the window.

The third pane is moved by means of a rotating cam mechanism that is partially located within holes formed in the outer panes. The cam mechanism, which operates the third pane, includes a handle, or a handle on each side of the door, which must be turned to operate the cam and slide the third pane.

One problem of this prior art arrangement is that the hole formed in the outer panes provide a weakness in the panes. As these outer panes are formed of glass, it is prone to breakage, both during use and during transportation before use. Furthermore, as the third pane is loosely supported by only one cam, vibrations during by transport, or impact forces on the handle, can cause breakage of the third pane.

Another problem with the prior art arrangement is that the handle may be difficult to grasp and rotate for some people whose grip has been affected by injury, arthritis, etc.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a window unit, comprising: a first sheet defining first transparent regions and first non-transparent regions; a second sheet comprising a transparent material arranged substantially parallel to said first sheet; and an obscuring element positioned between said first sheet and said second sheet, said obscuring element defining second transparent regions and second non-transparent regions, and said obscuring element being arranged to slide with respect to said first sheet, wherein said window unit comprises a cam that is slidable along a first direction and has a first cam surface configured to push said obscuring element along a different second direction when said cam is pushed in said first direction.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Figure 1 shows a door 101 comprising a window unit 102 embodying the present invention; Figure 2 shows the door 101 and window unit 102 with the window unit 102 in its closed configuration; Figure 3A shows a cross-section of a middle portion of the window unit 102, with the window unit in its open configuration; Figure 3B shows a central portion of the window unit 102 in its closed configuration Figure 4 shows the process of assembling the window unit 102 into the door 101; Figure 5 shows initial stages of the assembly of the window unit 102; Figure 6 shows the components of the window unit 102 shown in Figure assembled together, along with additional components that are still to be assembled; Figure 7 shows a partial cross-sectional view of the window unit 102; and Figure 8 shows a partial cross-sectional view of the door 101 with the window unit 102 fitted Figure 9 shows an enlarged view of the cam 511 and support member 507; and Figures IOA, lOB and 1OC each show the window unit 102 with the U-shaped channels 620 and 621 and the guide block 604 removed, and also with the first sheet 301 partially cut away.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 A door 101 comprising a window unit 102, embodying the present invention, is shown in Figure 1. The window unit 102 is shown in Figure 1 in an open configuration, and consequently a person 103 is able to see through the window unit 102. When in the open configuration, the window unit defines a plurality of transparent portions in the form of transparent horizontal stripes, alternating with non-transpareht portions in the form of non-transparent horizontal stripes.

The window unit has a handle 104, which may be operated to place the window unit in to its closed configuration. In the present embodiment, this is achieved by sliding the handle 104 horizontally.

Figure 2 The door 101 and window unit 102 is shown again in Figure 2 after a person 201 has pushed the handle 104 sideways in order to place the window unit 102 in its closed configuration. Consequently, the person 103, previously shown in Figure 1, can no longer see, or be seen, through the window unit.

It should be noted that the sliding action of the handle 104 is considered to be advantageous, when compared to prior art rotating handles, because the handle can be pushed without being firmly gripped, as would be required by a rotating handle. Thus, the sliding handle is easier to operate for people whose grip has been adversely affected by injury or disease, such as arthritis.

Figures 3A and 3B A middle portion of the window unit 102 is shown in cross-section in Figure 3A, with the window unit in its open configuration. Similarly, a central portion of the window unit 102 is shown in Figure 3B in its closed configuration.

The window unit 102 comprises a first sheet 301 defining transparent regions, such as regions 302A and 302B, as well as non-transparent regions, such as regions 303A and 303B. In the present embodiment, the first sheet 301 is formed of a pane of toughened glass on which the non-transparent regions (such as 303A and 303B) have been formed. In the present embodiment, the non-transparent regions form a series of equally spaced horizontal stripes of an opaque paint. However, as is known in the art, the non-transparent regions may be formed by other processes such as etching. In the present embodiment, each stripe, such as opaque region 303A, has a width of 14mm and is spaced from its neighbouring non-transparent regions by a transparent stripe (such as 302A and 302B) having a width of 10mm.

The window unit 102 also comprises a second sheet 304, comprising a transparent material, which is arranged substantially parallel to the first sheet 301. In the present embodiment, the second sheet is also formed of a pane of toughened glass, like the first sheet. However, unlike the first sheet, the second sheet is substantially free of non-transparent regions.

The window unit 102 further comprises an obscuring element 305 located between the first sheet and the second sheet. The obscuring element defines a second set of transparent regions, such as regions 306A and 306B, and a second set of non-transparent regions such as regions 307A and 307B.

The non-transparent regions on the obscuring element 305 are formed in the same manner as the first non-transparent regions on the first sheet 301, and they also have a similar format. i.e., the second set of transparent regions also define a series of parallel horizontal stripes.

As shown in Figure 3A, the obscuring element 305 may be positioned such that the second set of non-transparent regions are aligned with the first set of non-transparent regions on the first sheet 301. Consequently, the transparent regions of the first sheet and the obscuring element are also aligned and it is possible for light to pass through the window and for a person to see through the window.

In the present embodiment the obscuring element 305 comprises a sheet of transparent material to which non-transparent regions are applied, and in the present embodiment, the sheet of transparent material is formed of poly(methyl methacrylate), as sold under the trademark Perspex. However, other alternative embodiments are envisaged in which other transparent polymeric materials are used. In addition, other embodiments are also envisaged in which the obscuring element comprises a pane of toughened glass, or float glass.

By operation of the handle 104 of the window unit 102 the obscuring element 305 may be positioned such that the non-transparent regions of the obscuring element 305 are aligned with the transparent regions of the first sheet 301, and the transparent regions of the obscuring element 305 are aligned with the non-transparent regions of the first sheet 301, as shown in Figure 3B. For example, the non-transparent stripe 307A of obscuring element 305 is aligned with the transparent stripe 302A of the first sheet 301, and the transparent stripe 306B of the obscuring element 305 is aligned with the non-transparent stripe 303A of the first sheet 301. As may be understood from Figure 3B, with the obscuring element positioned as shown, viewing through the window unit 102 is prevented.

It may be noted that the non-transparent regions of the first sheet and the obscuring element have a width (in this case 14 millimetres) that is larger than the width (in this case 10 millimetres) of the transparent regions.

Consequently, the non-transparent regions of the first sheet and the obscuring element overlap (in this case by 2 millimetres) to ensure that viewing through the window unit is prevented.

Figure 4 The assembly of the window unit 102 into the door 101 is illustrated in Figure 4.

The door 101 is provided with a rectangular hole 401, which in the present embodiment is substantially square. The window unit 102 also has a substantially square shape and is dimensioned to be a good fit within the hole 401. Beading 402 is applied to the door 101 around the perimeter of the hole 401 on one side of the door. The unit 102 is fitted into the hole 401 and then a second set of beading material 403 is fixed to the second side of the door around the perimeter of the hole 401, thereby fixing the window unit 102 in place.

In one embodiment, which provides improved fire resistance, intumescent strips of material (not shown in Figure 4) are fitted between the beading 402 and the window unit 102 and between the beading 403 and the window unit 102.

In alternative embodiments the window unit is not square. For example, in one embodiment the window unit is rectangular and has a height that is approximately three times its width.

It should be noted that, in the present example, the window unit is located within a door, but in other examples the window unit is located within a wall.

Figure 5 The manufacture and construction of the window unit 102 is illustrated in Figures 5 and 6, with the initial stages of the assembly being illustrated in Figure 5.

Firstly, strips 501A and 501 B of a plastics material having a low co-efficient of friction are attached to one side of the rectangular second sheet 304. The strips 501A and 501B are arranged parallel to and spaced from vertical edges 500A and 500B of the second sheet 304. A pair of spacers 502A and 502B are attached to the same surface of the second sheet 304, spacer 502A being located between the strip 501A and the edge 500A and spacer 502B being located between the strip 501 B and the edge 500B.

Strips 503A and 503B of similar material to strip 501A and 501B are affixed to one surface of a first guide block 504. The guide block 504 has an elongated slot 505 for receiving a spindle of the handle 104.

In the present embodiment, the strips 501A, 501B, 503A and 503B are each formed of a PTFE film that is provided with a self adhesive surface, the adhesive being used to stick the strips to the second sheet 304 and first guide block 504 respectively. The guide block 504 is itself formed of glass in the present embodiment.

In the present embodiment, the obscuring element 305 is formed of two components. Namely a third sheet 506 and a supporting member 507.

The third sheet 506 is formed of a sheet of poly(methyl methacrylate) as mentioned above. The supporting member 507 is formed of a sheet of nylon material and defines a u-shape configured to receive the bottom edge 508 of the third sheet 506. The supporting member 507 also defines a cam surface 509, which during use co-operates with a cam surface 510 of a sliding cam 511. The sliding cam 511, in the present embodiment, is formed of similar material to the supporting member 507 and is provided with a hole 512 for receiving the spindle of the handle 104.

In alternative embodiments, the cam 511 and supporting member 507 are formed of other types of materials, but as will be understood upon further reading of this description, the materials are preferably formed of a relatively low friction material so that the first cam surface 510 of the cam 511 may easily slide over the second cam surface 509 of the supporting element 507.

In a further alternative embodiment, the obscuring element 305 is formed of one component only. In this embodiment, a third sheet, similar to sheet 506, is provided with a profiled bottom edge providing a cam surface for interaction with the cam surface 510 of cam 511.

It should be noted that in each of these embodiments, the third sheet is a continuous sheet that does not define any holes, which might cause a weakness in its structure. This differs from the known prior art window units that require the central pane to define a hole for co-operation with the handle mechanism.

Figure 6 The components of the window unit 102 previously shown in Figure 5 are shown assembled together in Figure 6 along with additional components of the window unit 102. Thus, in Figure 6 the spacers 502A and 502B have been attached by an adhesive to the second sheet 304, the third sheet 506 has been located within the supporting member 507 and positioned between the spacers 501A and 501 B, the guide block 504 has been positioned along the bottom edge of the second sheet 304 and the cam 511 located alongside the guide block 504 with its cam surface 510 alongside the cam surface 509 of support member 507. It may be noted that the non-transparent regions, such as 307A, are positioned on the side of the third sheet 506 that faces away from the second sheet 304. (This arrangement minimises the distance between the non-transparent regions on the third sheet and the non-transparent regions on the first sheet in the completed window unit. However, in an alternative embodiment, the non-transparent regions on the third sheet are on the side facing the second sheet.) The first sheet 301 is also shown in Figure 6. A pair of low friction strips 601A and 601B, of the same type as strips 501A and 501B have been attached to the first sheet 301 on the same side as its non-transparent regions such as region 303A.

The other components of the window unit 102 shown in Figure 6 are a second guide block 604, a lower U-shaped channel 620 and an upper U-shaped channel 621. The second guide block 604 is of a similar construction to the first guide block 504 having a slot 605 similar to slot 505 of the first guide block. Strips 603A and 603B, similar to strips 503A and 503B, are attached to one side of the second guide block 604, above and below its slot 605.

The lower U-shaped channel 620 has a flat floor 622 and a pair of walls 623 and 624 extending perpendicularly from the floor 622 to form the U-shape of the channel. The walls 623 and 624 are provided with similar slots 625 configured to be aligned with the slots 505 and 605 of the guide blocks 504 and 604 in the assembled window unit 102. The ends 626 and 627 of the U- shaped channel 620 are shaped to butt up against edges of the upper U-shaped channel 621 in the assembled window unit.

The upper U-shaped channel 621 has a floor 632 that is folded at right angles at two locations to form two corners 633 and 634. Thus, the upper U-shaped channel is divided by the corners 633 and 634 into three sections, namely a left side section 635, a top side section 636 and a right side section 637. Each of these three sections has a pair of walls, such as walls 638 and 639, extending perpendicularly from the floor 632 to form the U-shape of the channel, It may be noted that the floor 632 of the upper U-shaped channel 621 has the same width as the floor 622 as the lower U-shaped channel 620.

In the present embodiment, the U-shaped channel is formed from stainless steel, and the upper U-shaped channel 621 is formed of mild steel.

However, in other embodiments other materials providing the necessary strength and rigidity are used to form the two U-shaped channels.

To complete the assembly of the window unit 102, the first sheet 301 is attached to the spacers 501A and 501 B by adhesive, such that the first sheet 301 is arranged substantially parallel to the second sheet 304. The guide block 604 may then be laid alongside the cam 511 and the first sheet 301. This assembly is then slid inside the lower U-shaped channel 620 so that the guide blocks 504 and 604 are located within the U-shaped channel 620. This assembly is then slid within the upper U-shaped channel between the left side section 635 and right side section 637 until the upper edges of the first sheet 301 and the second sheet 304 reside between walls of the upper side portion 636. The upper U-shaped channel 621 is then attached to the lower U-shaped channel 620 by screws (not shown in Figure 6).

To complete the assembly the spindle of the handle 104 is passed through the slots 625 and 605, hole 512 of the cam, and slots 505 and 625 and, in the present embodiment, handles are attached to either end of the spindle.

Figure 7 A partial cross-sectional view of the window unit 102 is shown in Figure 7. The cross-section is taken through a horizontal plane, and consequently a portion of the second sheet 304 adjacent to its side edge 500A, and a corresponding portion of the first sheet 301 are shown fitted within the left side portion 635 of the upper U-shaped channel 621.

Figure 7 also shows the spacer 502A separating the two sheets 301 and 304, and also the third sheet 506 located between the two sheets 301 and 304. An end portion of the third sheet 506 is located between the low friction strips 501A and 601A. Thus, the low friction strips 501A and 601A provide spacers to space the third sheet 506 from both the first sheet 301 and second sheet 304. In addition, because the strips 501A and 601A are formed of a low friction material, the third sheet 506 is able to slide between the strips easily with respect to the two outer sheets 301 and 304.

In the present embodiment, additional strips 701 of similar material to strips 501A and 601A are fixed to the inside faces of the spacers 502A and 502B to provide a low friction surface over which the edge of the third sheet 506 is able to slide.

Figure 8 A partial cross-sectional view of the door 101 with the window unit 102 fitted is shown in Figure 8. For the purposes of clarity, a central portion of the window unit 102 has been omitted, as indicated by lines 800.

The components of the window unit 102 have been labelled up using reference numerals used in previous drawings.

As illustrated by Figure 8, the upper U-shaped channel 621 is dimensioned such that it is hidden behind beading 402 and 403. In the present embodiment, intumescent strips 801 extend along each portion of the beading 402 and 403, between the beading and the lower U-shaped channel 620 and upper U-shaped channel 621 respectively, so that the window unit 102 provides improved fire resistance. (Alternative embodiments do not include these intumescent strips.) As mentioned previously, the spindle 802 of the handle 104 extends through the slots 625, 605 and 505 in the lower U-shaped channel and the guide blocks 604 and 504. In addition, it is rigidly attached to the cam 511 within its hole 512. In the present embodiment, the spindle 802 extends all the way through the U-shaped channel 620, and it has the handle 104 on one end and a second handle 804 on its other end. Thus, the window unit 102 may be operated by manually pushing either the handle 104 or the handle 804.

In an alternative embodiment, the spindle 802 terminates at the cam 511 and has only a single handle, such as handle 104. Thus, the window unit can only be operated from one of its sides.

As illustrated by Figure 8, the cam 511 is positioned between the guide blocks 504 and 604 and rests upon the floor of the lower U-shaped channel 620. Thus, the guide blocks in combination with the floor define a means of guiding the cam as it is slid during use. In the present embodiment, the sliding action of the cam is made easier by the strips 503A, 503B, 603A and 603B that are fixed to the guide blocks 504 and 604, because they are formed of a material having a lower coefficient of friction than that of the guide blocks themselves.

As illustrated by Figure 8, the beading 402 and 403 define planes 805 and 806 at front face and said rear face of the door 101, and the handles 104 and 804 are entirely located between these two planes. As a consequence of this, the handles 104 and 804 are less likely to receive impacts, that could potentially damage the window unit, both when the door is in use an also during transport before the door is installed.

Figure 9 The cam 511 and support member 507 are shown in further detail in Figure 9.

The cam 511 has a straight bottom edge 901 and an upper edge that is contoured to provide the cam surface 510. The cam surface 510 defines a pair of straight sections 902 that are parallel with the bottom edge 901 and a respective sloping surface 903 extending up from the straight sections 902 to a respective plateaux 904. The plateaux are also defined by straight edges that are parallel with the bottom edge 901.

The supporting member 507, in the present embodiment, has a cam surface 509 of complimentary shape to the cam surface 510 of cam 511.

Consequently, it has a pair of plateaux 905 configured to rest on the straight sections 902 of cam 511 when the plateaux 904 of the cam 511 rests on straight sections 906 of the support member. The support member 507 also has a pair of sloping surfaces 907 that extend between its plateaux 905 and straight portions 906. The sloping surfaces 907 are arranged at an angle to the plateaux 509 and 906, and the angle also corresponds to the angle of the sloping surfaces 903 with respect to the plateaux 904 and straight sections 902 of the cam 511.

Figures bA, lOB and bC The window unit 102 is shown in each of Figures bA, lOB and 1OC with the U-shaped channels 620 and 621 and the guide block 604 removed, and also with the first sheet 301 partially cut away.

In Figure 1 OA, the cam 511 is in its right most position and consequently the obscuring element 305 is in its lowest position. In the present embodiment, the non-transparent regions, such as region 307A, of the obscuring element 305 are arranged such that they are aligned with the non-transparent regions, such as 303A, of the first sheet 301. Consequently, the window unit 102 is in its open configuration in Figure 1OA.

It may be noted that in this position the plateaux 905 of the supporting member 507 are resting on the straight portions 902 of the cam 511, the straight portions 906 of the supporting member 507 are resting on the plateaux 904 of the cam 511, and the sloping surfaces 907 of the supporting member 507 are resting on the sloping surfaces 903 of the cam 511.

The window unit 102 is shown in Figure lOB after the cam 511 has been linearly slid to an intermediate position. As the cam 511 is pushed leftwards, the sloping surfaces 903 of the cam 511 act upon the sloping surfaces 907 of the supporting member 507 causing the obscuring element 503 to be lifted up from its lowest position. Advantageously, the cam 511 has got two sloping surfaces 903 that are spaced apart, and consequently, because the obscuring element is being supported at two positions it is pushed upwards in a stable manner, i.e., there is not a tendency for the obscuring element 305 to be tilted as there might be if it were only acted upon at one point (as is the case in known prior art window units).

The window unit 102 is shown in Figure 1OC after further linear movement of the cam 511 to its leftmost position. In this position, the plateaux 905 of the supporting member 507 are resting upon the plateaux 904 of the cam 511. As the plateaux 904 are arranged to be perpendicular. to the motion of the obscuring element 305, the obscuring element 305 is stably supported in this raised position.

As illustrated in Figure lOG, with the obscuring element in the raised position the non-transparent regions, such as 307A, of obscuring element 305 are aligned with the transparent regions, such as 302A, of the first sheet 301.

Consequently, the window unit 102 prevents light from passing through it and prevents people from seeing through it.

Of course, the window unit 102 may be returned to its open figuration by sliding the cam 511 to the rightmost position shown in Figure bA, and allowing the obscuring element 305 to slide back down to its lower most position under the force of gravity.

In the present embodiment, the non-transparent regions of the obscuring element 305 are aligned with the non-transparent regions of the first sheet 301 when the obscuring element is in its lower most position as shown in Figure 1OA. However, in alternative embodiments the non-transparent regions of the obscuring element 305 and/or the non-transparent regions of the first sheet 301 are positioned such that the non-transparent regions of the obscuring element are aligned with the non-transparent regions of the first sheet when the obscuring element 305 is raised to its uppermost position.

In the present embodiment, the cam 511 is moved to both the left and to the right under manual force, and it is stable in both its open and closed configuration. However, in alternative embodiments the cam 511 is biased by a spring such that the obscuring element 305 is urged by the action of the spring and the cam 511 into its closed position. For example, with the present arrangement of non-transparent regions, the spring is used to urge the cam to the position shown in Figure bC. Thus, it is only possible to see through the window unit 102 when the handle is pushed against the force of the spring.

When the manual force is removed, the window unit is returned to its closed configuration by the spring.

In the present embodiment, the handle 104 is rigidly attached to the cam 511 and the cam 511 is slid sideways by a corresponding sideways movement of the handle. However, an alternative embodiment is envisaged in which the handle is pivotally mounted and is attached to a gear wheel that interacts with a toothed track on the cam 511. Thus, rotation of the handle causes teeth of the gear wheel to push the cam sideways and thereby push the obscuring element upwards.

Claims

Claims 1. A window unit, comprising: a first sheet defining first transparent regions and first non-transparent regions; a second sheet comprising a transparent material arranged substantially parallel to said first sheet; and an obscuring element positioned between said first sheet and said second sheet, said obscuring element defining second transparent regions and second non-transparent regions, and said obscuring element being arranged to slide with respect to said first sheet, wherein said window unit comprises a cam that is slidable along a first direction and has a first cam surface configured to push said obscuring element along a different second direction when said cam is pushed in said first direction.
2. A window unit in accordance with claim 1, wherein said cam surface is configured to act upon said obscuring element at two separate locations.
3. A window unit in accordance with claim I or claim 2, wherein said cam surface comprises a sloping surface which acts on said obscuring element during movement and a plateau which acts on said obscuring element to retain said obscuring element in a stable position.
4. A window unit in accordance with any one of claims I to 3, wherein said cam surface defines at least two sloping surfaces each acting on said obscuring element during movement of said obscuring element to maintain said obscuring element in a stable orientation during movement of said cam.
5. A window unit in accordance with any one of claims I to 4, wherein said cam is located below said obscuring element so that said cam pushes said obscuring element against the force of gravity.
6. A window unit in accordance with any one of claims I to 5, wherein said obscuring element comprises a third sheet formed of a transparent material and having a first surface facing towards said first sheet, and said non-transparent regions are defined on said first surface.
7. A window unit in accordance with any one of claims I to 6, wherein said obscuring element comprises a third sheet and a supporting member supporting said third sheet, said third sheet defining said second transparent regions and second non-transparent regions, and said supporting member defining a second cam surface co-operating with the cam surface of said cam.
8. A window unit in accordance with claim 6 or claim 7, wherein said third sheet comprises a sheet of a transparent polymeric material.
9. A window unit in accordance with claim 8, wherein said polymeric material is poly(methyl methacrylate).
10. A window unit in accordance with any one of claims I to 9, wherein said first and second sheets each comprise a sheet of glass.
II. A window unit in accordance with claim 10, wherein said first and second sheets each comprise a sheet of toughened glass.
12. A window unit in accordance with any one of claims I to II, wherein said second direction is substantially perpendicular to said first direction.
13. A window unit in accordance with any one of claims I to 12, wherein said obscuring element is separated from said first sheet and said second sheet by spacers formed of a material having a lower coefficient of s friction than said obscuring element.
14. A window unit in accordance with claim 13, wherein said spacers are attached to a respective one of said first and second sheets by an adhesive.
15. A door having a front a face and a rear face and an opening containing a window unit as claimed in any preceding claim, wherein said window unit comprises a handle attached to said cam for allowing manually operation of said cam, and said handle is entirely located between two planes defined by said front face and said rear face of said door.
16. A method of manufacturing a window unit, comprising: obtaining a first sheet defining first transparent regions and first non-transparent regions; arranging a second sheet comprising a transparent material substantially parallel to said first sheet; and obtaining an obscuring element defining second transparent regions and second non-transparent regions positioning said obscuring element between said first sheet and said second sheet such that said obscuring element is arranged to slide with respect to said first sheet; and mounting a cam to slide between guide surfaces in a first direction such that when said cam is slid along said first direction said obscuring element is pushed along a different second direction. * 18Amendments to the claims have been filed as follows Claims 1. A window unit, comprising: a first sheet defining first transparent regions and first non-transparent regions; a second sheet comprising a transparent material arranged substantially parallel to said first sheet; and an obscuring element positioned between said first sheet and said second sheet, said obscuring element defining second transparent regions and second non-transparent regions, and said obscuring element being arranged to slide with respect to said first sheet, wherein said window unit comprises a cam that is slidable along a first direction and has a first cam surface configured to push said obscuring element along a different second direction when said cam is pushed in said first direction, and said cam surface is configured to act upon said obscuring element at two separate locations.2. A window unit in accordance with claim 1, wherein said cam surface comprises a sloping surface which acts on said obscuring element during movement and a plateau which acts on said obscuring element to retain said obscuring element in a stable position.S*....I S * 3. A window unit in accordance with claim I or claim 2, wherein said cam surface defines at least two sloping surfaces each acting on said * obscuring element during movement of said obscuring element to maintain said obscuring element in a stable orientation during movement of said cam. * S. * S S..*:*. 4. A window unit in accordance with any one of claims I to 3, wherein said cam is located below said obscuring element so that said cam pushes said obscuring element against the force of gravity.5. A window unit in accordance with any one of claims I to 4, wherein said obscuring element compnses a third sheet formed of a transparent material and having a first surface facing towards said first sheet, and said non-transparent regions are defined on said first surface.6. A window unit in accordance with any one of claims I to 4, wherein said obscuring element comprises a third sheet and a supporting member supporting said third sheet, said third sheet defining said second transparent regions and second non-transparent regions, and said supporting member defining a second cam surface co-operating with the cam surface of said cam.7. A window unit in accordance with claim 5 or claim 6, wherein said third sheet comprises a sheet of a transparent polymeric material.8. A window unit in accordance with claim 7, wherein said polymeric material is poly(methyl methacrylate).9. A window unit in accordance with any one of claims I to 8, wherein said first and second sheets each comprise a sheet of glass.10. A window unit in accordance with claim 9, wherein said first and **** second sheets each comprise a sheet of toughened glass. ** .4 * S S11. A window unit in accordance with any one of claims I to 10, wherein said second direction is substantially perpendicular to said first : direction. S.. I. S * *I* 30 12. A window unit in accordance with any one of claims I to 11, wherein said obscuring element is separated from said first sheet and said second sheet by spacers formed of a material having a lower coefficient of friction than said obscuring element.13. A window unit in accordance with claim 12, wherein said spacers are attached to a respective one of said first and second sheets by an adhesive.14. A door having a front a face and a rear face and an opening containing a window unit as claimed in any preceding claim, wherein said window unit comprises a handle attached to said cam for allowing manually operation of said cam, and said handle is entirely located between two planes defined by said front face and said rear face of said door.15. A method of manufacturing a window unit, comprising: obtaining a first sheet defining first transparent regions and first non-transparent regions; arranging a second sheet comprising a transparent material substantially parallel to said first sheet; and obtaining an obscuring element defining second transparent regions and second non-transparent regions positioning said obscuring element between said first sheet and said second sheet such that said obscuring element is arranged to slide with *:** respect to said first sheet; and mounting a cam to slide between guide surfaces in a first direction such that when said cam is slid along said first direction a cam surface of said cam acts upon said obscuring element at two separate locations to push said obscuring element along a different second direction. e ** *s. . * ** * *j