GB2282173A - Service hatch - Google Patents

Abstract

A window assembly (30) for providing a service hatch to the exterior of a building comprises a closure (32) which is movable between an open and closed position and a service counter (36) comprising a step (38) which is adjacent the closure when it is in the closed position, and provides security by inhibiting inward movement of the closure. A fixed external window casing can be positioned outwardly of the counter step (38) and inhibits outward movement of the closure. The closure can comprise two sliding windows (32 and 34, Fig 4) which are separated to open by a drive mechanism operated by a control system (Fig 1) which incorporates safety means. A guide rail (Figs 6 and 7) is provided together with bearing means for the closures. <IMAGE>

Description

PUK5962 WINDOW MECHANISM AND ASSEMBLY This invention relates to a mechanism for operating a window assembly such as an automatic window used for serving food to customers at a drive-through restaurant, for example. The invention also relates to a window assembly.

It is known to provide a window assembly which includes glazed panels which automatically open and close without being directly manually manipulated by an operator. GB 2155541A discloses a mechanism comprising a push rod which is actuated to open a window when the push rod is pressed for example by a serving attendant's hip, for example. Also, Ready Access (a division of Ready Metal Manufacturing of Chicago, USA) disclose in their 1991 brochure (08665/REA, By- Line 4235) use of a light beam to monitor the position of an attendant such that when the beam is broken a window automaticall!- is opened by a cable drive system and such that when the beam is recreated, the window automatically closes.

Various problems exist with window mechanisms and window assemblies in the known art including poor weather proofing against the ingress of rain. Additionally, it is known for the windows to be relatively heavy and undergo substantial vibration during movement thus being noisy and of a poor standard. Further, it is a problem in the known art for window assemblies to be easily broken by intruders thus enabling access to a restaurant through its service hatch.

The invention seeks to avoid or at least mitigate these and other problems of the known art and to provide a secure window assembly and a reliable operating mechanism.

According to one aspect of the invention, there is provided a window assembly providing an exterior service hatch, for use at a drive-through restaurant for example, wherein a movable closure such as a window can be opened outwardly or laterally to enable use of the service hatch but wherein the closure is prevented by step means from being openable inwardly.

Another aspect provides a window assembly for providing a service hatch to the exterior of a building comprises a closure uhicil is movable between an open and closed position and a service counter comprising a step which is adjacent the closure when it is in the closed position, which step acts to inhibit inward movement of the closure.

Preicrablv the window assembly comprises a iied external window casing position outwardly of the counter step and providing means which inhibits outward movement of the closure.

More preferably a channel is provided between the counter step and window casing in which channel the closure is able longitudinally to move between the open and closed positions.

Further cooperating means can be provided in the channel and the base of the closure to guide the closure during movement.

The bearing means can be provided by said cooperating guide means to bear some of the load of closure.

Preferably a sill is provided outwardly of the step to enable water to fall away from the step.

Another aspect of the invention provides a window assembly independent of or according to the immediately preceding paragraphs wherein the closure comprises two windows which are separable to provide an opening at the service hatch.

Preferably the pair of windows are positioned in an abutting closed position wherein the abutment is off-centre of the service hatch.

A preferred feature is a sensor for detecting whether a window is closed, the sensor being positioned substantially at the centre of the service hatch adjacent one of the windows.

A further preferred feature is that a second window sensor is provided to detect when the one window is in an open position.

Another aspect of the invention provides a window assembly independent of or according to any immediately preceding paragraphs comprising a drive mechanism for opening and closing a closure wherein the mechanism is attached to the closure by endless means.

Preferably the endless means is a toothed belt.

Another aspect of the invention provides a window assembly for providing an attended service hatch to the exterior of a building independent of or according to any preceding claim comprising a control system which communicates with a drive mechanism for opening and closing a closure and an attendant sensor, such that on detection of an attendant at the service hatch the control system operates to open the closure, wherein the control system has means for setting the delay period for closing the closure after the sensor no longer detects an attendant.

Preferably the delay period can be set bx an attendant using input means which communicates with the control system.

blore preferably the attendant sensor comprises a light emitter and detector positioned such that an attendant is detected when a beam between the emitter and detector is broken and the delay period begins when the beam is re-established.

Another aspect of the invention provides a window assembly independent of or according to any immediately preceding paragraph which comprises safety means which is operable to prevent movement of a closure which is driven between an open and closed position when an anomalous event occurs.

Preferably the safety means comprises means for detecting movement of the closure such that if the movement is inhibited at a position intermediate a recognised open and closed position the closure is stopped.

More preferably the safety means comprises a pulse generator which provides a continuous series of pulses during movement of the closure thereby indicating movement of the closure such that said safety means stops movement of the closure if said series of pulses stops.

In a preferred form the pulse generator comprises an infra-red emitter and detector which operably detects movement of reflective means attached to a drive mechanism.

In a preferred form of this aspect of the invention the window assembly comprises a control system which communicates with the safety means, which system resets to normal operation following an anomalous safety event when the closure is moved in the opposite direction to the direction of travel when it was stopped.

In another form of this aspect of the invention the safety means comprises a timer which is triggered when the closure starts to move from an open to closed or closed to open position, the system is configured such that if the closure does not reach either of the closed or open positions before a predetermined period in excess of the normal time for opening or closing the closure, then the system inhibits the drive mechanism used to drive the closure. In a preferred form the closing time is approximately 2.8 seconds and the predetermined period is about 3.5 seconds. If an arm is trapped in the middle of a dual window mechanism for example, then the time to stop the window will be less that or in the order of 1 second.

Yet another aspect of the invention provides a kit of parts for making a window assembly according to any of the immediately preceding aspects of the invention, comprising a frame having a base and header projection, a service counter, a closure, a window casing and modular panelling for the base and header projections.

Another aspect of the invention provides use of a window assembly according to any preceding claim to provide an exterior service hatch at a drive-through restaurant.

A further aspect of the invention provides a guide rail for guiding movement of a closure for a service hatch to the exterior of a building, which guide rail comprises a first member for attachment to the closure and second member for attachment to a support means above the operating position of the closure. a cooperating bearing means is provided which operably acts to enable smooth movement of the first member relative to the second member.

Preferably said bearing means comprises a rotatable wheel journalled on an axle attached to one of said members.

More preferably the other of said members comprises a groove which cooperates with said wheel to restrict movement of the wheel transverse to the movement of travel of the first member relative to the second member.

In a preferred form the guide rail comprises four wheels wherein the axles of a lower pair of wheels are in substantially the same horizontal plane whilst the axles of an upper pair of wheels are also in a common substantially horizontal plane which is upwardly displaced from the other plane.

Another aspect of the invention provides use of an AC synchronous motor as part of the drive mechanism for a window assembly according to any of the earlier aspects of the invention.

A yet further aspect of the present invention provides a closure assembly having a window wherein the closure and window assembly form a substantially flush fit with the exterior wall to a building in which the assembly is to be fitted.

Another aspect of the invention provides a closure assembly for a service hatch having a heater mechanism which operates to heat the service area especially when the closure is in an open position.

Another aspect of the invention provides a closure assembly for a service hatch comprising a heater mechanism which is operable to prevent frosting of part of the service hatch. Preferably the heater is operable to prevent frosting of a service counter provided adjacent a service opening in the service hatch.

An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 is a schematic block diagram of a control system for operating a window; FIGURE 2 is a schematic cross-sectional view of a side elevation of a window assembly according to the invention; FIGURE 3 is a schematic front elevational view of the window shown in Figure 2 from the exterior; FIGURE 4 is a plan view in cross-section of the window shown in Figures 2 and 3; FIGURE 5 is a side elevational view of the window shown in Figures 2, 3 and 4 from the exterior; FIGURE 6 is a schematic cross-section of pr!rt of the window guide rail mechanism; FIGURE 7 is a schematic front elevational view of part of the guide rail shoulne Figure 6; FIGURE 8 is a perspective view of the second embodiment of a service hatch according to the invention; and FIGURE 9 is a schematic cross sectional view of the window assembly shown in Figure 8.

Referring to Figure 1 there is shown a control system 10 for controlling the operation of a service window such as an automatic service hatch for a drive-through restaurant, for example, such as shown in Figures 2 to 5. Principally, a controller 12 is provided to communicate with a sensor which detects the presence of an operator (or attendant) at a service hatch and to actuate a drive mechanism 20 to open and close the windows at a service hatch as required. For example controller 12 could comprise a microprocessor or alternatively hard wired logic clips connected to provide the necessary control operations.

The system includes many additional features to the standard operation which enables a much more beneficial and user friendly automatic service hatch operation compared to the known art. System 10 comprises an input 16 which can comprise an alphanumeric keypad for example and possibly other input means such as a key operated lock andior smart card actuated mechanism which can be used to start up the overall system 10. Altematively, a simple on/off switch can be provided. The system could for example draw its power from a mains supply and compnse various transformers and regulators as necessary to provide power to the various electrical and electronic components.

The system 10 can be programmed at the time of installation of the overall mechanism to operate in a fixed manner upon initialisation. For example, depending on the user and the application, it might be desirable for the service hatch closure such as sliding windows to open automatically where a light beam is broken or other similar operator sensor 14 is actuated but to delay closing the window for a fixed period after deactivation of the operator sensor (e.g. re-establishment of light beam) for a period of, say, half a second up to thirty seconds in selectable increments of one second. Thus an installer can program a system 10 to the user's requirement, e.g.

having an eight second delay before closing the window.

Alternatively, input device 16 can comprise an alpha-numeric keypad which enables the user to select such a delay period before the window closes. Display 18 might for example comprise a liquid crystal, or other display to which the controller 12 communicates providing prompts to a user for preferred operating conditions.

Display 18 could comprise a simple series of LED's for example, each one of which indicates a given state of the system such as power on or off. Further there is provided a window sensor which operates to provide a signal to controller 12 indicating the position of the windows. For example, window sensor 22 can comprise niicros" itches positioned in the zlndo assenlh3s such that a given mtcro- switch Is depressed if the window is open and another rrticro-suitch is depressed if the window is closed. Preferably however, window sensor 22 comprises a light sensor having a light emitter and detector such that when the beam is broken it is known that the window is placed between the emitter and detector. Thus, a number of such detectors can be used in combination to determine the position of a window, for example, if it is desired to have multiple open positions of the window. Preferably however, two windows are provided which are movable as shown in Figures 2 to 5 from a closed to an open position by a drive mechanism 20. Preferably the pair of windows are caused to abut in a closed position slightly off-centre of the actual serving hatch or serving aperture. Thus, a single sensor can be provided centrally of the serving hatch to indicate when the windows are closed and a second sensor can be located at a second position to indicate when one of the windows is open. Thus, only two sensors are required to indicate an open and closed state of both windows which are preferably operated using a single endless belt drive such that if one window is open the other is too.

Drive mechanism 20 can comprise an electrical motor for example having a toothed drive wheel to cooperate with a toothed drive belt connected to the movable windows.

Preferably the motor is an AC synchronous motor such as a Rapidsyn AC synchronous motor which operates at a constant speed and is able to stop and start and change directions rapidly.

Further, a safety sensor 24 is provided which operates to stop the drive mechanism when, for example, the window closes and trapping an arm. Safety sensor 4 could comprise a number of devices to detect such an eventuality and wherein controller 12 is operable to deactivate drive mechanism 20. ','here the drive mechanism is the preferred AC synchronous motor type the motor free wheels in the absence of power such that the window can easily be opened manually to allow the trapped arm to be freed.

Preferably, the safety sensor 24 comprises a sensor such as an infra-red sensor positioned to detect the movement of a drive shaft between the motor and a drive belt in mechanism 20. The motor shaft could comprise a series of black and white stripes such that the infra-red detector provides a continuous pulse output when the motor is running. In the event that the windows are not closed but the motor stops running, the controller 12 detects this as a failure and shuts off power to the drive mechanism 20 thus preventing a further closing force against a trapped arm, for example.

Alternatively, timers can be used to monitor the expected position of a closure between open and closed positions. If the closure does not reach a closed or open position when expected, for example due to an obstacle, then the drive mechanism can be deactivated until reset, e.g. by moving the closure in the opposite direction.

A description will now be given of a preferred window assembly according to the invention as shown schematically in Figures 2 to 5.

Window assembly 30 comprises sliding windows 32 and 34 S.lc': open to provide a sen ing hatch in the overall assembly. As shown In Figure 3 the assembly gerlorallv compnses a substantially 180 visibility through ".inJo' placement 42 which Is housed in a frame supported on a base projection 44 and covered by a header projection 46. Thus, there is provided an easily assembled protruding window assembly 30 wherein features such as the casing of the base projection 44 are easily replaced, for example, if need be when it is driven into by a vehicle.

A particular benefit of the present invention is the provision of serving counter 36, step or lip 38 and sill 40 which in combination provide the benefits of a suitable work surface at the service hatch as well as weather proofing and security. Sill 40 is sloping to enable rainwater to run away from the service hatch whilst lip 38 prevents any rain which might be blown in underneath the sliding windows from being able to contact the counter surface 36. This thus enables the counter to be kept clean amongst other benefits. Additionally, lip 38 provides the benefit that windows 32 and 34 cannot be pushed in at their lower end without breaking the window frames.

Thus, by making the window frames from a suitably strong, for example metallic material, an anti-burglar device is provided by the present invention. By firmly attaching the window guide rail system in the header 46 and by making the window panels double glazed, for example, a very secure overall window assembly 30 can be provided.

A channel 39 is thus provided between step 38 and the front of window placement 42 in which the slidable windows 32 and 34 move. Channel 39 can comprise a keying member (not shown) to cooperate with a groove (not shown) in the base of the movable windows thereby to control the line of movement of the windows. The keying member can also comprise bearings to cooperate with the running surface of a groove in the base of the windows thereby to enable the weight of the windows to be carried on the wedge. Beneficially, this produces a smoother movement of the window. Of course, the bearing can be carried in the base of the window to act on a flat race elements at the top of a keying member.

To provide further for smooth running and other beneficial properties of the invention, a preferred form of clutchless motor 52 is provided. As described earlier this can be an AC synchronised motor carrying a drive shaft connected to a tooth cog which in turn causes the rotation of a tooth drive belt connected to window carriers 54 attached to the tops of the windows.

Figures 6 and 7 show a preferred form of window carrier which further provides for smooth running of the windows and restricts the possible vibration of the window due to the confined runner mechanism provided and dual, vertically displaced axes about which the window might pivot. The window carriers 54 comprise rotatable wheels 60 which key into grooves 58 in a support assembly 56 rigidly attached in the header projection 46. As can be seen from the cross-sectional view in Figure 6, the wheels 60 are located in a close-fit in grooves 58 so as to minimise possible oscillation of the window about this load bearing, pivotal position.

As can be seen in Figure 7, four wheels or rollers 60 are provided for each of the window carriers 54 thus providing good distribution of the load of the window onto the support rail 56. Thus, the windows 32 and 34 can be made of relatively heavy materials thus enabling greater security in the window assembly 30. Of course, anv number of rollers 30 could be provided to take the weight off a suitable window.

In a preferred form two pairs of rollers 60 are provided where vertically displaced rollers are aligned in order to minimise angular displacement of the window, for example, due to a frictional dragging at the base of the window or conversely a motive force being applied at the top of the window. In a preferred form the windows are approximately 1 metre high. Use of a separable rail 59 which carries the groove rails 58 is found to be beneficial in terms of machining the rail carrier 59 and assembling it as part of the support assembly 56 in the header 46.

A further benefit of the invention is seen from the combination of Figures 2 and 4 wherein the compact nature of the operator sensor devices 62 and 64 and input pad 66 together with control system 10 and motor 52, (i.e. the principal electrical and electronic system), can be seen to form a compact and discreetly located system. For example, control system 10 can be easily located in the header projection 46 which is easily accessed by lowering a shutter flap 48. The operator sensor 14 shown in Figure 1 can comprise an emitter 62 and detector 64 shown in Figure 4 which are connected to controller 12 housed in the header projection 46.

The safety features described earlier can easily be incorporated in the header unit also adjacent the drive shaft of motor 52. Further, the window sensor not shown in the drawings can easily be located in the header unit and are therefore easily connected to the control system 10.

A further benefit of the header unit 46 described here is that it reduces the amount of high level sunlight entering a restaurant in the kitchen and/or service area. This sunlight is found to be a particular nuisance in that it can be detrimental to the electric cash tills, for example, causing them to malfunction.

A further operating feature of the system in a preferred form is that when the safety sensor is actuated to stop the drive mechanism, the system is easily re-set by reversing the direction in which the windows were travelling, for example, either by leaning into the beam or operating a manual switch on the keypad. A feature of the system being that the keypad comprises an automatic mode on/off and an open/close switch for use in a manual key-push mode. Further, the window can be provided with handles for completely manual opening i.e. by an attendant using his or her hands to physically open the windows. Furthermore, the windows can be provided with a lock or any number of locks for securing the window in a closed position when the restaurant is closed, for example. Furthermore, the windows 32 and 34 can carry magnetic catches 68 at their abutting edges in order to secure them in a closed position during operation of the system. Naturally, such a magnetic catch is only useful for temporary closure of the windows and should not provide sufficient force to prevent opening of the windows by the motorised mechanism.

Feature 26 of system 10 shown in Figure I represents a heater mechanism which can be controlled by controller 12 such that for example a heater can be turned on when controller 12 detects via a window sensor 22 that a ulndou is open. Alternatively a heater can be turned on or off using a user operated input device 16 which, as described previously, could be a key pad. Controller 12 can be operable to provide questions to a user via display 18 to request the type of operation required for a given heater mechanism. As described later, various heater mechanisms can be provided in the service hatch assembly. For example, an operator could select via input 16 to have an overhead fan heater automatically operate when window sensor 22 indicates that the closures, or windows, are open. Alternatively, a user might disable such an automatic mode and have an overhead heater such as 26b shown in Figure 2 operate continuously, not at all, or via manual on/off switching.

Referring to Figure 2 there is shown a side view of a window assembly according to the invention wherein controller 12 is located in an overhead cabinet or header projection 46 having a shutter flap 48. A motor 52 is provided to drive window 32 between its open and closed positions. The window assembly 30 comprises, in this embodiment, an overhead heater 26b mounted in header projection 46 and also a heater 26a for heating counter surface 36 at the bottom of the assembly.

Heater 26a can, for example, comprise a self-regulating process heating tape which is connected to controller 12. Alternatively, other heating devices could be used where preferably a thermo-couple is attached to the part of the assembly which is being heated, such as to counter surface 36, in order to provide a feed back mechanism to controller 12 thereby to enable regulation of the temperature of the heated component. A suitable heater can be a self-regulating process heating tape such as RS Auto Trace (registered trade mark of Raychem Chemelex) type 5BTV2- C. A length of such tape can be adhered to the undersurface of counter 36, for example, by winding a length of the wire in a curved pattern to provide even heating of surface 36. Alternatively, or as well, the tape could be positioned adjacent step 38 which is near the exterior of the assembly. Preferably the temperature of the service counter 36 is regulated to prevent frosting thereof and, for example, a temperature of say 5"C could be maintained. Figure 4 shows how a heating wire type assembly can be attached to service counter 36.

Other parts of the window assembly 30 could, of course, be heated such as the region of the guide rail 39 or outside lip 40 of the window assembly, or indeed the window structures 32, 34 or 42, the header projection 46, or the base section 44.

Controller 12 can be programmed to enable a user to select the temperature at which a given component of the window assembly is to be maintained, for example, from say 1"C to 20"C. A user could be asked a series of questions using display 18 and could input answers using input 16. Preferably the antifrost type heaters are continuously operated when the service hatch area is in use, that is during opening hours of the service hatch function such as at a drive-through restaurant.

A second heater 26b is shown in this embodiment which can be a fan type blower, which can be again controlled by controller 12 using a pre-programmed logic sequence or alternatively using a manual switch provided. for example. in the vicinity of the service hatch. Heater 26b could comprise known electrically conductive filanlents to provide heat and a fan thereby t(' circulate heated air thn'ugh vents 27 which can be positioned to direct the air into the region of the ulrldou opening.

Heater 26b could, for example, operate when optical switch 64 detects the presence of an attendant at the service hatch. Alternatively, 26b could be operated continuously, for example. In a further alternative, a thermo-couple or other temperature sensor could be provided at an appropriate position in or near window assembly 30 to monitor the temperature and provide feed-back to controller 12 thereby to enable regulation of the temperature in the vicinity of window assembly 30.

Referring to Figures 8 and 9, there is shown a window assembly which is mounted flush with the walls W a building to which it is fitted. This has the advantage that the service hatch can be completely flush with the walls or have minimal amount of protrusion therefrom. This is particularly advantageous since it is found that drivers of vehicles approaching hatches at take-away restaurants are prone to drive into protruding service hatches.

The flush fitting window assembly can, of course, comprise any one or all of the integers described in relation to the first embodiment. For example, a step 38 is provided on the inside of the window to prevent inward movement of closure 32.

Additionally, a heater 26b is provi bolt type which require a particular type of key in order to be released. Additionally, the window fittings in windows 32 and 34 are preferably at least double glazed thereby again to provide a security feature for the overall assembly 30. Of course, dead bolts could also be provided in other locations on the windows, for example, at the bottom of the central part of each of the windows 32 and 34.

Claims (33)

1. A window assembly for providing a service hatch communicating the interior and exterior of a building comprises a closure which is movable between an open and closed position and a service counter comprising a step which is adjacent the closure when it is in the closed position, which step acts to inhibit inward movement of the closure.

2. A window assembly according to claim 1 comprising a fixed external window casing positioned outwardly of the counter step and providing means which inhibits outward movement of the closure.

3. A window assembly according to claim 2 therein a channel is provided between the counter step and window casing in which channel the closure is able longitudinally to move between the open and closed positions.

4. A window assembly according to claim 3 wherein cooperating means are provided in the channel and the base of the closure to guide the closure during movement.

5. A window assembly according to claim 4 wherein bearing means is provided by said cooperating guide means to bear at least some of the load of the closure.

6. A window assembly according to any preceding claim wherein a sill is provided outwardly of the step to enable water to drain from the step.

7. A window assembly independent of or according to any preceding claim wherein the closure comprises two windows which are separable to provide an opening at the service hatch.

8. A window assembly according to claim 7 wherein the pair of windows are positioned in an abutting closed position wherein the abutment is off-centre of the service hatch.

9. A window assembly according to claim 8 comprising a sensor for detecting whether a window is closed, the sensor being positioned substantially at the centre of the service hatch adjacent one of the windows.

10. A window assembly according to claim 9 uherinsl a second X ulndou sensor is provided to detect when the one u indoz is In an open position.

11. A window assembly independent of or according to any preceding claim comprising a drive mechanism for opening and closing a closure wherein the mechanism is attached to the closure by endless means.

12. A window assembly according to claim 11 wherein the endless means is a toothed belt.

13. A window assembly for providing an attended service hatch to the exterior of a building independent of or according to any preceding claim comprising a control system which communicates with a drive mechanism for opening and closing a closure and an attendant sensor, such that on detection of an attendant at the service hatch the control system operates to open the closure, wherein the control system has means for setting the delay period for closing the closure after the sensor no longer detects an attendant.

14. A window assembly according to claim 13 wherein the delay period can be set by an attendant using input means which communicates with the control system.

15. A window assembly according to claim 13 or 14 wherein the attendant sensor comprises a light emitter and detector positioned such that an attendant is detected when a beam between the emitter and detector is broken and the delay period begins when the beam is re-established.

16. A window assembly independent of or according to any preceding claim comprises safety means which is operable to prevent movement of a closure which is driven between an open and closed position when an anomalous event occurs.

17. A window assembly according to claim 16 wherein the safety means comprises means for detecting movement of the closure such that if the movement is inhibited at a position intermediate a recognised open and closed position the closure is stopped.

18. A window assembly according to claim 17 wherein the safety means comprises a pulse generator which provides a continuous series of pushes during movement of the closure.

19. A window assembly according to claim 18 wherein the pulse generator comprises an infra-red emitter and detector which operably detects movement of reflective means attached to a drive mechanism.

20. A window assembly according to any of claims 16 to 19 comprising a control system which communicates with the safety means, which system resets to normal operation following an anomalous safety event, when the closure is moved in the opposite direction to the direction of travel when it was stopped.

21. A window assembly according to claim 16 wherein the safety means comprises a timer which is triggered when the closure starts to move from an open to closed or closed to open position, the system is configured such that if the closure does not reach either of the closed or open positions before a predetermined period in excess of the normal time for opening or closing the closure, then the system inhibits the drive mechanism used to drive the closure.

22. The window assembly of claim 21 wherein the closing time is approximately 2.8 seconds and the predetermined period is about 3.5 seconds.

23. A kit of parts for making a window assembly according to any of claims 1 to 22 comprising a frame having a base and header projection, a service counter, a closure, a window casing and modular panelling for the base and header projections.

24. Use of a window assembly according to any preceding claim to provide an exterior service hatch at a drive-through restaurant.

25. A guide rail for guiding movement of a closure for a service hatch to the exterior of a building, which guide rail comprises a first member for attachment to the closure and second member for attachment to a support means above the operating position of the closure, a cooperating bearing means is provided which operably acts to enable smooth movement of the first member relative to the second member.

26. A guide rail according to claim 25 wherein said bearing means comprises a rotatable wheel journalled on an axle attached to one of said members.

27. A guide rail according to claim 25 wherein the other of said members comprises a groove which cooperates with said wheel to restrict movement of the wheel transverse to the movement of travel of the first member relative to the second member.

28. A guide rail according to claims 26 or 27 comprising four wheels wherein the axles of a lower pair of wheels are in substantially the same horizontal plane whilst the axles of an upper pair of wheels are also in a common, substantially horizontal plane which is upwardly displaced from the other plane.

29. Use of an AC synchronous motor as part of the drive mechanism for a window assembly according to any of claims 1 to 22.

30. A closure assembly for a service hatch comprising a closure and a frame wherein the assembly is adapted to fit substantially flat against a wall in which it is operably fitted.

31. A closure assembly for a service hatch having a heater mechanism for heating the service area.

32. A closure according to claim 31 wherein the heater mechanism is adapted to be operable when the closure is in an open position.

33. A closure assembly for a service hatch wherein the closure compnses one. and preferably two or more, devices for securing ii in a closed position.