Vision panel

Abstract

A vision panel 100 is for use in a door leaf and includes first and second polarising filters with polarisation directions. The vision panel has first and second configurations. In the first / second

Description

Technical Field The present disclosure relates to a vision panel, and in particular a vision panel having controllable optical transmittance. Background Vision panels having controllable optical transmittance are known. Such vision panels are used in psychiatric hospitals and other institutions for providing controllable privacy of a room. In a first example of a known vision panel having controllable optical transmittance, two optical panes each having alternating transparent and opaque portions are arranged parallel to one another. In a first configuration, in which the transparent portions of each optical pane are aligned with one another, a user can see through the vision panel. In a second configuration, in which the transparent portions of each optical pane are aligned with the opaque portions of the other optical pane, the vision panel provides privacy. A problem with vision panels of this type, however, is that only an incomplete view through the vision panel is available. In particular, when the transparent portions are aligned, the opaque portions are also aligned, thus partially obstructing the view through the vision panel. In a second example of a known vision panel having controllable optical transmittance, a pane of glass is provided which is electrically switchable between an opaque state and a transparent state. For example, the pane of glass may comprise electrochromic glass. A problem with vision panels of this type, however, is that they are comparatively expensive, may have a limited lifespan of the switchable glass, may be prone to malfunction, and require a power source to operate. There is therefore a need for an improved optically switchable vision panel. Summary According to a first aspect of the present disclosure, there is provided a vision panel for use in a door leaf, the vision panel comprising: a first polarising filter having a polarisation direction; a second polarising filter having a polarisation direction; wherein the vision panel comprises a first configuration in which the polarisation directions of the first and second polarising filters are aligned, and a second configuration in which the polarisation directions of the two filters are perpendicular; the vision panel further comprising an actuation mechanism configured to rotate at least one of the polarising filters to thereby operate (e.g. switch) the vision panel between the first and second configurations. When the polarising filters are aligned such that their polarisation directions are parallel, the vision panel may appear completely transparent, with no occluded portions. When the polarising filters are aligned such that their polarisation directions are perpendicular, the vision panel may appear completely opaque. Further, because the vision panel is operated by simple mechanical means it is comparatively inexpensive to manufacture, is robust, may not be not prone to malfunction or degradation over time, and can as required be operated without an external power source. Without wishing to be bound by theory, a polarising filter is an optical surface which only transmits linearly polarized light of a given polarisation direction. Polarising filters therefore have an inherent polarisation direction, defined as the polarisation direction of light which will be transmitted through the filter. The polarisation direction of a polarising filter is therefore rotatable by simply rotating the polarising filter. Where two polarising filters are overlapped with one another such that their respective polarisation directions aligned, they will therefore transmit light having the same polarisation direction. However, where two polarising filters are overlapped with one another such that their respective polarisation directions are perpendicular, a first of the filters will transmit light having the same polarisation direction as the first of the filters, but this light will be blocked by the polarising filter having the perpendicular polarisation direction. Accordingly, in this configuration, the filters will transmit no light. The first configuration may correspond to an optically transmissive state of the vision panel. The second configuration may correspond to an optically opaque state of the vision panel. The first polarising filter and the second polarising filter may be identical to one another. They may further be arranged so as to perfectly overlap one another. They may further each be circular in shape, and may be concentrically arranged on top of one another. Accordingly, as they rotate, the first and second polarising filters may remain perfectly overlapped with one another. The vision panel may therefore also be circular, for example may comprise a generally circular housing which encases the first and second polarising filters. The vision panel may be operable between the first and second configurations by rotating the second polarising filter through an angle of 90 degrees relative to the first polarising filter. In an example, one of the first polarising filter and the second polarising filter may be fixed relative to a housing of the vision panel, and the other of the first polarising filter and the second polarising filter may be moveable through an angle of 90 degrees relative to the housing. In other examples, each filter may be rotatable, e.g. counter-rotatable, relative to the housing. The vision panel may comprise a housing which encases the polarising filters and the actuation mechanism. The first polarising filter may be rotatable through an angle of 45 degrees (e.g. one eighth of a full rotation) between a first rotational position and a second rotational position. The second polarising filter may be rotatable through 45 degrees (e.g. one eighth of a full rotation) between a third rotational position and a fourth rotational position. The polarisation directions of the two filters may be aligned when the first filter is in the first position and the second filter is in the third position. The polarisation directions of the two filters may be perpendicular when the first filter is in the second position and the second filter is in the fourth position. Where each filter moves by an angle of 45 degrees as described above, operation of the vision panel by means of a handle which controls the actuation mechanism may be simplified. In particular, in such examples, the required travel of the handle to operate the vision panel between the first and second configurations may be half that required where one of the polarising filters is fixed relative to the housing and the other is moved through an angle of 90 degrees by the actuation mechanism. The first configuration of the vision panel may comprise the first polarising filter in the first position and the second filter in the third position. The second configuration of the vision panel may comprise the first polarising filter in the second position and the second polarising filter in the fourth position. The first polarising filter may move in a first (e.g. clockwise) direction from the first position to the second position. The second polarising filter may move in a second (e.g. anti-clockwise) direction from the third position to the fourth position. The actuation mechanism may be configured in a first mode of operation to move the first polarising filter from the second position to the first position, and to move the second polarising filter from the fourth position to the third position. That is to say, the first mode of operation may move the polarisation directions of the filters from perpendicular alignment (e.g. the second configuration of the vision panel), to parallel alignment (e.g. the first configuration of the vision panel). The first mode of operation may comprise rotation of a handle for controlling the actuation mechanism in a first direction. The actuation mechanism may be configured in a second mode of operation to move the first polarising filter from the first position to the second position, and to move the second polarising filter from the third position to the fourth position. That is to say, the second mode of operation may move the polarisation directions of the filters from parallel alignment (e.g. the first configuration of the vision panel), to perpendicular alignment (e.g. the second configuration of the vision panel. The second mode of operation may comprise rotation of a handle for controlling the actuation mechanism in a second direction. Herein, a first direction may comprise a clockwise direction, and a second direction may comprise an anticlockwise direction. The handle may comprise a thumb turn. In another example, the handle may comprise a key and follower. The actuation mechanism may comprise a first geared wheel. The first polarising filter may comprise a first geared surface. Teeth of the first geared wheel may engage teeth of the first geared surface such that rotation of the first geared wheel causes rotation of the first polarising filter. The first geared surface may span one eighth of the circumference of the first polarising filter. The remaining seven eighths of the circumference of the first polarising filter may be free from a geared surface. The actuation mechanism may comprise a second geared wheel. The second polarising filter may comprise a second geared surface. Teeth of the second geared wheel may engage teeth of the second geared surface such that rotation of the second geared wheel causes rotation of the second polarising filter. The second geared surface may span one eighth of the circumference of the second polarising filter. The remaining seven eighths of the circumference of the second polarising filter may be free from a geared surface. The actuation mechanism is configured such that the first geared wheel rotates in an opposite direction to that of the second geared wheel. The actuation mechanism may for example comprise a gearbox. The gearbox may comprise the first geared wheel, the second geared wheel, an input geared wheel, and an intermediate geared wheel. The teeth of the input geared wheel may directly engage the teeth of the second geared wheel. The teeth of the input geared wheel may further directly engage the teeth of the intermediate geared wheel. The teeth of the intermediate geared wheel may further directly engage the teeth of the first geared wheel. In short, counter-rotation between the first and second geared wheels (and accordingly between the first and second polarising filters) may be achieved by the intermediate geared wheel, which operates the first geared wheel but not the second geared wheel. Accordingly, rotation of the input geared wheel in the first (clockwise) direction may cause rotation of the second polarising filter in the clockwise direction, and rotation of the first polarising filter in the anticlockwise direction. Similarly, rotation of the input geared wheel in the second (anticlockwise) direction may cause rotation of the second polarising filter in the anticlockwise direction, and rotation of the first polarising filter in the clockwise direction. The input geared wheel may be directly coupled to the handle, such that rotation of the handle in the first direction causes rotation of the input geared wheel in the first direction, and such that rotation of the handle in the second direction causes rotation of the input geared wheel in the second direction. The input geared wheel may comprise a first engagement surface, which may also be considered a first sub-wheel or cog, configured to cause the first geared wheel to rotate (whether directly or via the intermediate geared wheel). The input geared wheel may comprise a second engagement surface, which may similarly be considered a second sub-wheel or cog, configured to cause the second geared wheel to rotate. In such an arrangement, the first and second engagement surfaces of the input geared wheel may be provided on a single input pin such that both the first and second engagement surfaces can be simultaneously rotated via the single input pin. This advantageously prevents one of the engagement surfaces from being jammed, as may be possible if the engagement surfaces are provided on separate input pins. According to a second aspect there is provided a door leaf having a vision panel according to the first aspect. According to a third aspect there is provided a door system comprising a door frame, and a door leaf according to the second aspect, wherein the door leaf is pivotally mounted to the door frame. In alternative examples, the vision panel may be installed in a wall. Brief Description of the Drawings Specific embodiments of the present disclosure will now be described, with reference to the accompanying drawings, in which: Fig. 1 shows a vision panel according to the present disclosure; Fig. 2 shows a thumb turn from the vision panel of Fig. 1; Fig. 3 shows a door leaf comprising a vision panel according to Fig. 1; Fig. 4 shows a first polarising filter from the vision panel of Fig. 1; Fig. 5 shows a second polarising filter from the vision panel of Fig. 1; Fig. 6 shows a first actuation ring for attachment to the first polarising filter of Fig. 4, the first actuation ring having a first geared surface at an external edge thereof; Fig. 7 shows a second actuation ring for attachment to the second polarising filter of Fig. 5, the second actuation ring having a second geared surface at an external edge thereof; Fig. 8 shows a close-up of a geared surface; Fig. 9 shows an internal structure of the vision panel of Fig. 1; Fig. 10 shows a front view of a close-up of an actuation mechanism from the vision panel of Fig. 1; Fig. 11 shows a front view of a simplified version of the actuation mechanism of Fig. 10; Fig. 12 shows a perspective view of the actuation mechanism of Fig. 11; Fig. 13 shows a front view of a first portion of the actuation mechanism of Fig. 11; Fig. 14 shows a rear view of the actuation mechanism of Fig. 11; Fig. 15 shows a rear perspective view of the actuation mechanism of Fig. 11; Fig. 16 shows a rear view of a second portion of the actuation mechanism of Fig. 11. Like reference numerals are used for like components throughout the drawings. Detailed Description Fig. 1 shows a vision panel 100 according to the present disclosure. Vision panel 100 comprises a viewing pane 102, a housing 104 surrounding the viewing panel 102, and a thumb turn 106 embedded in a protruding side surface 108 of the housing 104. The viewing pane 102 may comprise a sheet of glass, under which the polarising filters (described below) are secured. As shown, the housing 104 is generally circular, save for the protruding side surface 108. Fig. 2 shows a close-up of the thumb turn 106. Fig. 3 shows a door leaf 300 comprising the vision panel 100. As stated above, two polarising filters are secured behind the sheet of glass of the viewing pane 102. Fig. 4 illustrates a first of the polarising filters 400. Fig. 5 illustrates a second of the polarising filters 500. Polarisation directions of the polarising filters 400, 500 are illustrated using crosshatching in figs. 4 and 5. As the skilled reader will understand, the polarization directions will not be visible to the naked eye. The cross-hatching is however used for illustrative purposes in Figs. 4 and 5. In the depicted arrangement, the first polarising filter 400 is arranged with its polarisation direction perpendicular to that of the second polarising filter 500. By rotating one of the polarising filters by 90 degrees relative to the other, the polarisation directions would be aligned. Fig. 6 shows a first actuation ring 600 for attachment around the outer edge the first polarising filter 400. Fig. 7 shows a second actuation ring 700 for attachment around the outer edge of the second polarising filter 500. As shown, the first actuation ring 600 comprises a first geared surface 602 at an external surface thereof, and the second actuation ring 700 comprises a second geared surface 702 at an external surface thereof. As shown in the close-up of Fig. 8, each geared surface 602 / 702 comprises a plurality of teeth 800, for engagement by teeth of a corresponding geared wheel, as will be described below. As shown, the first geared surface 602 occupies 45 degrees of (equivalent to one eighth of) the circumference of the first actuation ring 600. The second geared surface 702 occupies 45 degrees of (equivalent to one eighth of) the circumference of the second actuation ring 700. Fig. 9 shows an actuation mechanism (gearbox 900) for rotating the actuation rings (and accordingly rotating the filters 400, 500) so as to operate the vision panel 100. Fig. 10 shows a close-up of the gearbox 900. Gearbox 900 comprises an input wheel 902, an intermediate wheel 904, a stabilising wheel 906, a first wheel 908, and a second wheel 910. Thumb turn 102 is attached to the input wheel 902 for driving the input wheel 902. The input wheel 902 is coupled directly to the intermediate wheel 904, which itself is coupled directly to the first wheel 908. The input wheel 902 is further coupled directly to the second wheel 910 (as can be seen from Fig. 14). Finally, the input wheel 902 is coupled directly to the stabilising wheel 906. The stabilising wheel 906 may be provided to stabilise rotation of the input wheel 902. Additionally, stabilising wheel 906 may ensure that rotation of thumb turn 102 causes a rotation of both engagement surfaces 902a, 902b of input wheel 902 (visible in Fig 12) even in the case that these engagement surfaces 902a, 902b are provided on or attached to separate input pins. Provision of stabilising wheel 906 in this case is advantageous because it means that an occupant of a room cannot prevent vision panel 100 from being opened by jamming the input pin to the input wheel engagement surface on their side of the door. That is, even if the input pin on the occupant’s side of the door has been jammed, stabilising wheel 906 may still enable both engagement surfaces 902a, 902b of input wheel 902 to be turned by rotation of thumb turn 102, thereby maintaining the ability of a person on the other side of the door to operate vision panel 100 and see into the room. In some examples, however, the input stabilising wheel 906 may be dispensed with. In some such implementations, engagement surfaces 902a, 902b of input wheel 902 may be provided on or attached to a single input pin, ensuring that both engagement surfaces 902a, 902b can be rotated using thumb turn 102 and obviating the need for stabilising wheel 906. An example of such an arrangement is shown in Fig. 11. The gearbox 1100 of Fig. 11 is in all other respects the same as the gearbox 900 of Fig. 9 and 10. The stabilising wheel 906 will therefore not be further described, and the following description applies equally to the gearbox 900 and to the gearbox 1100. Herein, a first mode of operation is defined as switching of the vision panel from a non-transmissive (opaque) configuration to a transmissive configuration. The first mode of operation in the exemplary example comprises rotation of the thumb turn 102 in the clockwise direction. By extension, a second mode of operation is defined as a switching of the vision panel from a transmissive configuration to a non-transmissive (opaque) configuration. The second mode of operation in the exemplary example comprises rotation of the thumb turn 102 in the anticlockwise direction. The first mode of operation of the gearbox 900 / 1100 will now be described. The first mode of operation constitutes rotation of the thumb turn 102, and therefore the input wheel 902, in a clockwise direction. As the skilled reader will understand, the second mode of operation is the exact opposite of the first mode of operation, and is achieved by rotating the thumb turn 102, and therefore the input wheel 902, in an anti-clockwise direction. For brevity, therefore, only the first mode of operation will be described, on the basis that the second mode of operation is simply the reverse of the first mode of operation. When the input wheel 902 is rotated in the clockwise direction, the intermediate wheel 904 is caused to rotate in the anticlockwise direction, which in turn causes the first wheel 908 to rotate in the clockwise direction. Finally, the rotation of the first wheel 908 in the clockwise direction causes the first actuation ring 600, and by extension the first polarising filter 400, to rotate in the anticlockwise direction. Therefore, the gearbox 900 / 1100 ensures that rotation of the thumb turn in the clockwise direction causes rotation of the first polarising filter in the anti-clockwise direction, e.g. from a second position to a first position, through an angle of 45 degrees. Further, when the input wheel is rotated in the clockwise direction, the second wheel 910 is caused to rotate in the anticlockwise direction, which in turn causes the second actuation ring 700, and by extension the 8 second polarising filter 500, to rotate in the clockwise direction. Therefore, the gearbox 900 / 1100 ensures that rotation of the thumb turn in the clockwise direction causes rotation of the first polarising filter in the clockwise direction, e.g. from a fourth position to a third position, through an angle of 45 degrees. Moreover, the gearbox ensures counter-rotation of the first polarising filter 400 relative to the second polarising filter 500 when the thumb turn 102 is rotated. When the first filter 400 is in the second position and the second filter 500 is in the fourth position, the polarisation directions of the filters are perpendicular to one another, such that the vision panel is in the non-transmissive (opaque) configuration. Further, when the first filter 400 is in the first position and the second filter 500 is in the third position, the polarisation directions of the filters are parallel to one another, such that the vision panel is in the transmissive configuration. Moreover, rotation of the input wheel 902 in the clockwise direction changes the vision panel from non-transmissive (opaque) configuration to the transmissive configuration; and rotation of the input wheel 902 in the anticlockwise direction changes the vision panel from the transmissive configuration to the non-transmissive (opaque) configuration. Fig. 12 shows a perspective view of the gearbox 1100. As can be seen, the first wheel 908 engages the first geared surface 602 of the first actuation ring 600, and the second wheel 910 engages the second geared surface 702 of the second actuation ring 700. As can be more clearly seen from Fig. 12, the input wheel 902 comprises a first engagement surface 902a which engages the intermediate wheel 904, and a second engagement surface 902b which engages the second wheel 910; and the first wheel 908 comprises a first engagement surface 908a which engages the intermediate wheel 904, and a second engagement surface 908b which engages the first geared surface 602. The intermediate wheel 904 includes a single actuation surface which engages both the first engagement surface 902a of the input wheel 902 and the first engagement surface 908a of the first wheel 908. As shown in Fig. 15, which is a reverse perspective view of the gearbox 1100, the second wheel 910 includes a first engagement surface 910a which engages the second engagement surface 902b of the input wheel 902, and a second engagement surface 910b which engages the second geared surface 702. Each engagement surface comprises a respective plurality of teeth. Also shown in Fig. 15 is a follower 1500 which extends through the thumb turn 102 and the input wheel 902. Fig. 13 shows a partial front view of the gearbox 1100, with the second wheel 910 removed for illustrative purposes. Fig. 14 shows a rear view of the gearbox 1100. Fig. 16 shows a partial rear view of the gearbox 1100, with the intermediate wheel 904 and the first wheel 908 removed for illustrative purposes. Accordingly, the gearbox provides for operation of the vision panel from the non-transmissive 5 state to the transmissive state (first mode of operation), and from the transmissive state to the non-transmissive state (second mode of operation), through operation of the thumb turn. It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other implementations will be apparent to those of skill in the art upon reading and 10 understanding the above description. Although the present disclosure has been described with reference to specific example implementations, it will be recognized that the disclosure is not limited to the implementations described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense. The scope of the 15 disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. A vision panel for use in a door leaf, the vision panel comprising:a first polarising filter having a polarisation direction;a second polarising filter having a polarisation direction;wherein the vision panel comprises a first configuration in which the polarisation directions of the first and second polarising filters are aligned, and a second configuration in which the polarisation directions of the two filters are perpendicular;the vision panel further comprising an actuation mechanism configured to rotate at least one of the polarising filters to thereby operate the vision panel between the first and second configurations.

2. The vision panel of claim 1, wherein the first polarising filter, the second polarising filter, and optionally the vision panel, are circular in shape.

3. The vision panel of claim 1 or claim 2, wherein the vision panel is operable between the first and second configurations by rotating the second polarising filter through an angle of 90 degrees relative to the first polarising filter.

4. The vision panel of any preceding claim, further comprising a housing which encases the polarising filters and the actuation mechanism;wherein the first polarising filter is rotatable through 45 degrees between a first position and a second position;wherein the second polarising filter is rotatable through 45 degrees between a third position and a fourth position;wherein the polarisation directions of the two filters are aligned when the first filter is in the first position and the second filter is in the third position; andwherein the polarisation directions of the two filters are perpendicular when the first filter is in the second position and the second filter is in the fourth position.

5. The vision panel of claim 4, wherein the first configuration comprises the first polarising filter in the first position and the second polarising filter in the third position; and wherein the second configuration comprises the first polarising filter in the second position and the second polarising filter in the fourth position.

6. The vision panel of claim 4 or claim 5, wherein the first polarising filter moves in a second direction from the second position to the first position, and wherein the second polarising filter moves in a first direction from the fourth position to the third position.

7. The vision panel according to any of claims 4 to 6, wherein the actuation mechanism is configured in a first mode of operation to move the first polarising filter from the second position to the first position, and to move the second polarising filter from the fourth position to the third position.

8. The vision panel according to any of claims 4 to 7, wherein the actuation mechanism is configured in a second mode of operation to move the first polarising filter from the first position to the second position, and to move the second polarising filter from the third position to the fourth position.

9. The vision panel according to any preceding claim, wherein the actuation mechanism is operable by means of a handle, for example by means of a thumb turn.

10. The vision panel according to claim 9, wherein operating the handle in a first direction moves the first and second polarising filters into the first configuration, and wherein operating the handle in a second direction moves the first and second polarising filters into the second configuration.

11. The vision panel according to any preceding claim, wherein the actuation mechanism comprises a first geared wheel, wherein the first polarising filter comprises a first geared surface, and wherein teeth of the first geared wheel engage teeth of the first geared surface such that rotation of the first geared wheel causes rotation of the first polarising filter.

12. The vision panel according to claim 11, wherein the actuation mechanism further comprises a second geared wheel, wherein the second polarising filter comprises a second geared surface, and wherein teeth of the second geared wheel engage teeth of the second geared surface such that rotation of the second geared wheel causes rotation of the second polarising filter.

13. The vision panel of claim 12, wherein the actuation mechanism is configured such that the first geared wheel rotates in an opposite direction to that of the second geared wheel.

14. A door leaf having a vision panel according to any preceding claim installed therein.

15. A door system comprising a door frame and a door leaf according to claim 14, whereinthe door leaf is pivotally mounted to the doorframe.13

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