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Title:
RETRACTABLE OR REMOVABLE BOLLARD APPARATUS AND SYSTEM
Document Type and Number:
WIPO Patent Application WO/2013/081474
Kind Code:
A1
Abstract:
A bollard apparatus (100) has a housing (1) and a barrier member (2) disposed at least partially within the housing(1). The barrier member (2) is slidable relative to the housing (1) between a first, extended position, and a second, retracted position. The apparatus (100) has an electrical connection means (10), at least one electrically actuable locking means (4) and an electrical path between the electrical connection means and the electrically actuable locking means. The electrically actuable locking means (4) is operable to prevent relative movement between the barrier member (2) and the housing (1) when the barrier member (2) is in at least one of the first and second positions. A system comprising the bollard apparatus (100) and an unlocking means (20) is also described.

Inventors:
BROADHURST ROBERT CHARLES (NZ)
BROADHURST DAVID EDWARD CHARLES (NZ)
Application Number:
PCT/NZ2012/000218
Publication Date:
June 06, 2013
Filing Date:
November 26, 2012
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
BULLY BOY LTD (NZ)
International Classes:
E01F9/646; E01F13/04
Foreign References:
US4715742A1987-12-29
EP1277884A22003-01-22
Other References:
See also references of EP 2798124A4
Attorney, Agent or Firm:
BALDWINS INTELLECTUAL PROPERTY (Wellesley StreetAuckland, 1141, NZ)
Download PDF:
Claims:
CLAIMS

1. A bollard apparatus comprising:

a housing and a barrier member disposed at least partially within the housing, the barrier member slidable relative to the housing between a first, extended position, and a second, retracted position;

an electrical connection means, at least one electrically actuable locking means and an electrical path between the electrical connection means and the electrically actuable locking means; wherein

the electrically actuable locking means is operable to prevent relative movement between the barrier member and the housing when the barrier member is in at least one of the first and second positions.

2. The bollard of claim 1 wherein the electrically actuable locking means is operable to prevent relative movement between the barrier member and the housing when the barrier member is in the first position and when it is in the second position.

3. The bollard of claim 1 or 2 wherein the apparatus comprises a control means. 4. The bollard of claim 3 wherein the control means is operable to electrically disconnect the electrical connection means from the electrically actuable locking means.

5. The bollard of claim 3 or 4 wherein the control means is operable to receive user

verification information.

6. The bollard of claim 5 wherein the control means receives the user verification

information via the electrical connection means.

7 The bollard of claim 5 wherein the bollard is provided with a separate communications or data input means for transfer of the user verification information to the control means.

8. The bollard of claim 7 wherein the separate communications or data input means

comprises an RF receiver or an optical receiver.

9. The bollard of any one of the preceding claims, further comprising biasing means to bias the barrier member towards the first, extended position.

10. The bollard of claim 9 wherein the biasing means comprises a counter weight.

11. The bollard of claim 9 or 10 wherein the biasing means comprises a gas spring or strut.

12. The bollard of claim 9, 10 or 11 wherein the bollard is absent any actuating means for moving the barrier member relative to the housing, other than the biasing means.

13. The bollard of claim 2 wherein the housing comprises a locking member having a first end which is rotatably connected to the housing and a magnetic portion which is spaced apart from the first end. 14. The bollard of claim 13 wherein the rotatable connection is located, in use, below the magnetic portion.

15. The bollard of claim 14 wherein the electrically actuable locking means comprises a magnetic member provided adjacent an outer surface of the barrier member.

16. The bollard of claim 15 wherein the electrically actuable locking means comprises

means to change the magnetic polarity of the portion of the magnetic member closest to the surface of the barrier member. 17. The bollard of claim 15 wherein the electrically actuable locking means comprises

means for rotating the magnetic member.

18. The bollard of claim 15 wherein the magnetic member attracts the magnetic portion of the locking member when the portion of the magnetic member closest to the surface of the barrier member has a first polarity.

19. The bollard of claim 18 wherein the magnetic member repels the magnetic portion of the locking member when the portion of the magnetic member closest to the surface of the barrier member has a second polarity. The bollard of claim 13 wherein the housing is provided with a second said locking member which is located, in use, below the first locking member.

The bollard of claim 20 wherein the second locking member has a first end which is rotatably connected to the housing and a magnetic portion which is spaced apart from the first end, wherein, in use, magnetic portion is located below the rotatable connection.

The bollard of claim 21 wherein polarity of the magnetic portion of the first locking member is opposite to that of the magnetic portion of the second locking member.

The bollard of any one of the preceding claims, wherein the electrical connection means comprises at least one socket.

The bollard of any one of claims 1 to 22 wherein the electrical connection means comprises an inductive power transfer receiver.

A bollard system comprising:

a bollard apparatus comprising:

a housing and a barrier member disposed at least partially within the housing, the barrier member slidable relative to the housing between a first, extended position, and a second, retracted position,

a first electrical connection means, at least one electrically actuable locking means and an electrical path between the electrical connection means and the electrically actuable locking means, wherein

the electrically actuable locking means is operable to prevent relative movement between the barrier member and the housing when the barrier member is in at least one of the first and second positions,

the system further comprising an unlocking means comprising a portable electrical power source and a second electrical connection means adapted for removable electrical connection with the first electrical connection means, to thereby supply electrical power to the first electrical connection means, electrical path and electrically actuable locking means.

26. A bollard apparatus substantially as herein described with reference to Figures 1 and 2, Figures 3 to 4A, or Figure 5.

Description:
RETRACTABLE OR REMOVABLE BOLLARD APPARATUS AND SYSTEM

Field of the invention

The present invention relates to the field of retractable or removable bollards, and in particular to bollards which require an external power source to activate an electrically actuated locking means.

Background

In their most basic form bollard apparatus comprise a housing, which is to some extent buried in the ground, and a barrier member (often also referred to as a "bollard") which is engaged with the housing. When in an extended position the barrier member prevents movement of a vehicle over the top of the housing, and so one or more of the apparatus may be used to block vehicular access to an area. The barrier member is usually locked or otherwise connected to the housing to prevent unauthorised users from changing its position.

Presently available retractable or removable bollards may be grouped into two broad groups. The first group are manually retractable and/or removable. This type of bollard typically requires physical assistance from the user to change between a raised and a lowered position. Such bollards are typically provided with a manual locking mechanism, such as a padlock, to stop unauthorised users adjusting or removing the barrier. This system may be relatively low cost, but may have problems with reliability due to corrosion problems with the lock, as well as ingress of dirt and water. An additional problem may be that the locking means may be too easily circumvented.

The second broad group are apparatus which use some form of actuator to change the position of the barrier. The applicant's New Zealand patent No. 560731 describes such a system.

These systems typically require installation, usually underground, of a permanent connection to an energy source (electrical, compressed air or the like). While systems of this type are often provided with some form of electronic user verification system, they may be uneconomic for many installations, particularly if only one or two barriers are required, or if the barriers do not need to be raised or lowered frequently. The reference to any prior art in the specification is not, and should not be taken as, an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge in any country. Object of the Invention

It is an object of a preferred embodiment of the invention to provide a bollard system and/or a bollard apparatus which will overcome or ameliorate problems with such systems and/or apparatus at present, or which will at least provide the public with a useful choice. Other objects of the present invention may become apparent from the following description, which is given by way of example only

Brief Summary of the Invention According to one aspect of the present invention there is provided a bollard apparatus comprising:

a housing and a barrier member disposed at least partially within the housing, the barrier member slidable relative to the housing between a first, extended position, and a second, retracted position;

an electrical connection means, at least one electrically actuable locking means and an electrical path between the electrical connection means and the electrically actuable locking means; wherein

the electrically actuable locking means is operable to prevent relative movement between the barrier member and the housing when the barrier member is in at least one of the first and second positions.

Preferably, the electrically actuable locking means is operable to prevent relative movement between the barrier member and the housing when the barrier member is in the first position and when it is in the second position.

Preferably, the apparatus comprises a control means.

Preferably, the control means is operable to electrically disconnect the electrical connection means from the electrically actuable locking means. Preferably, the control means is operable to receive user verification information.

Preferably, the control means receives the user verification information via the electrical connection means.

Preferably, the bollard is provided with a separate communications or data input means for transfer of the user verification information to the control means.

Preferably, the separate communications or data input means comprises an RF receiver or an optical receiver.

Preferably, the bollard further comprises biasing means to bias the barrier member towards the first, extended position. Preferably, the biasing means comprises a counter weight.

Preferably, the biasing means comprises a gas spring or strut.

Preferably, the bollard is absent any actuating means for moving the barrier member relative to the housing, other than the biasing means.

Preferably, the housing comprises a locking member having a first end which is rotatably connected to the housing and a magnetic portion which is spaced apart from the first end. Preferably, the rotatable connection is located, in use, below the magnetic portion.

Preferably, the electrically actuable locking means comprises a magnetic member provided adjacent an outer surface of the barrier member. Preferably, the electrically actuable locking means comprises means to change the magnetic polarity of the portion of the magnetic member closest to the surface of the barrier member.

Preferably, the electrically actuable locking means comprises means for rotating the magnetic member. Preferably, the magnetic member attracts the magnetic portion of the locking member when the portion of the magnetic member closest to the surface of the barrier member has a first polarity.

Preferably, the magnetic member repels the magnetic portion of the locking member when the portion of the magnetic member closest to the surface of the barrier member has a second polarity.

Preferably, the housing is provided with a second said locking member which is located, in use, below the first locking member.

Preferably, the second locking member has a first end which is rotatably connected to the housing and a magnetic portion which is spaced apart from the first end, wherein, in use, magnetic portion is located below the rotatable connection. Preferably, the polarity of the magnetic portion of the first locking member is opposite to that of the magnetic portion of the second locking member.

Preferably, the electrical connection means comprises at least one socket. Preferably, the electrical connection means comprises an inductive power transfer receiver.

According to a second aspect of the present invention there is provided a bollard system comprising:

a bollard apparatus comprising:

a housing and a barrier member disposed at least partially within the housing, the barrier member slidable relative to the housing between a first, extended position, and a second, retracted position,

a first electrical connection means, at least one electrically actuable locking means and an electrical path between the electrical connection means and the electrically actuable locking means, wherein

the electrically actuable locking means is operable to prevent relative movement between the barrier member and the housing when the barrier member is in at least one of the first and second positions,

the system further comprising an unlocking means comprising a portable electrical power source and a second electrical connection means adapted for removable electrical connection with the first electrical connection means, to thereby supply electrical power to the first electrical connection means, electrical path and electrically actuable locking means.

Preferably, the electrically actuable locking means is operable to prevent relative movement between the barrier member and the housing when the barrier member is in the first position and when it is in the second position.

Preferably, the apparatus comprises a control means. Preferably, the control means is operable to electrically disconnect the electrical connection means from the electrically actuable locking means.

Preferably, the control means is operable to receive user verification information. Preferably, the control means receives the user verification information via the electrical connection means.

Preferably, the bollard is provided with a separate communications or data input means for transfer of the user verification information to the control means.

Preferably, the separate communications or data input means comprises an RF receiver or an optical receiver.

Preferably, the bollard further comprises biasing means to bias the barrier member towards the first, extended position.

Preferably, the biasing means comprises a counter weight.

Preferably, the biasing means comprises a gas spring or strut.

Preferably, the bollard is absent any actuating means for moving the barrier member relative to the housing, other than the biasing means.

Preferably, the housing comprises a locking member having a first end which is rotatably connected to the housing and a magnetic portion which is spaced apart from the first end. Preferably, the rotatable connection is located, in use, below the magnetic portion.

Preferably, the electrically actuable locking means comprises a magnetic member provided adjacent an outer surface of the barrier member.

Preferably, the electrically actuable locking means comprises means to change the magnetic polarity of the portion of the magnetic member closest to the surface of the barrier member. Preferably, the electrically actuable locking means comprises means for rotating the magnetic member.

Preferably, the magnetic member attracts the magnetic portion of the locking member when the portion of the magnetic member closest to the surface of the barrier member has a first polarity.

Preferably, the magnetic member repels the magnetic portion of the locking member when the portion of the magnetic member closest to the surface of the barrier member has a second polarity. Preferably, the housing is provided with a second said locking member which is located, in use, below the first locking member.

Preferably, the second locking member has a first end which is rotatably connected to the housing and a magnetic portion which is spaced apart from the first end, wherein, in use, magnetic portion is located below the rotatable connection.

Preferably, the polarity of the magnetic portion of the first locking member is opposite to that of the magnetic portion of the second locking member. Preferably, the electrical connection means comprises at least one socket.

Preferably, the electrical connection means comprises an inductive power transfer receiver.

The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

According to a still further aspect of the present invention, a bollard apparatus and/or a bollard system is substantially as herein described, with reference to the accompanying drawings.

Further aspects of the invention, which should be considered in all its novel aspects, will become apparent from the following description given by way of example of possible embodiments of the invention.

Brief Summary of the Figures

Figure 1 Is a diagrammatic cross-section of a bollard apparatus of the present invention, with the barrier member in a retracted position.

Figure 2 Is a diagrammatic cross-section of the bollard apparatus of Figure 1 , with the barrier member in an extended position.

Figure 3 Is a diagrammatic cross-section of a bollard apparatus according to another embodiment of present invention, with the barrier member in a raised position.

Figure 3A Is an enlarged diagrammatic view of the electrically actuable locking means of the apparatus shown in Figure 3.

Figure 4 Is a diagrammatic cross-section of the bollard apparatus of Figure 3, with the barrier member in a lowered position.

Figure 4A Is an enlarged diagrammatic view of the electrically actuable locking means of the apparatus shown in Figure 4.

Figure 5 Is a diagrammatic cross-section of a bollard apparatus according to a third

embodiment of present invention, with the barrier member in a raised position. Brief Description of Preferred Embodiments δ

Referring first to Figures 1 and 2, a bollard apparatus of the present invention is generally referenced by arrow 100. The apparatus 100 comprises a housing 1 , and a barrier member 2 disposed at least partially within the housing 1. The barrier member 2 is slidably engaged with the housing 1. In a preferred embodiment the barrier member 2 is able to withdraw completely into the housing 1 , as shown in Figure 1. A suitable sealing means 3 is preferably provided between the mouth 1 A of the housing 1 and the barrier 2 to prevent ingress of water or dirt into housing 1. The housing 1 is preferably substantially sealed apart from the mouth 1A. The exterior of the housing 1 around the mouth 1 A is preferably formed into a top collar or flange 1 B. In use, the bollard apparatus 100 is preferably buried up to the level of the lower surface of the top collar 1 B.

The barrier means 2 is preferably substantially cylindrical in shape, as is typical of retractable bollards, but other cross-sectional shapes may be used. The housing 1 preferably has a substantially cylindrical inner chamber which is closed at the end distal to the mouth 1A.

Relative movement between the housing 1 and barrier means 2 can be prevented though the use of electrically actuable locking means 4. The locking means 4 may be electromechanical, for example a solenoid lock. In a preferred embodiment each locking means 4 defaults to a locked state (that is, with the bolt 4A extended), when unpowered. However, in other embodiments the lock may be of a latching type, whereby power is applied to the lock to change its state from locked to unlocked, or from unlocked to locked, but where the lock can remain in the locked state and in the unlocked state when the locking mechanism is not powered.

Examples of such a mechanism include a permanent magnet based latching solenoid or an electric motor which rotates a locking mechanism.

In a preferred embodiment the electrically actuable locking means 4 may be mounted to the barrier means 2, and may engage a suitable lock engaging formation 5 provided on the inner wall 6 of the housing. The lock engaging formation 5 may take a number of forms, and in some embodiments may simply be an aperture in the housing (not shown), but in a preferred embodiment comprises an inwardly projecting formation 7. It is preferred that the inwardly projecting formation has an annular shape and extends around substantially the entire circumference of the inner wall 6, so as to be functional regardless of the angular orientation of the barrier member 2 relative to the housing 1. If other lock engaging formations are used (for g example a simple aperture in the housing), it may be necessary to restrain rotation of the barrier 2 relative to the housing 1 to ensure that the bolt 4A can engage with the formation.

The housing 1 is provided with at least one, and preferably with at least two lock engaging formations. A lower formation 5A is used to hold the barrier means 2 in a retracted position (as shown in Figure 1), and an upper formation 5B is used to hold the barrier means 2 in an extended position (as shown in Figure 2). In some embodiments (not shown), intermediate lock engaging formations may be provided to allow the barrier means 2 to be held in an intermediate, semi-retracted position.

If inwardly projecting formations 7 are used, as shown in Figures 1 and 2, then these are preferably provided with ramp formations 8 adapted to urge the bolt 4A of the electrically actuable locking means 4 back to a withdrawn position when the bolt 4A is slid over them. This allows the barrier member 2 to be moved from a position in which the electrically actuable locking means 4 are between the lock engaging formations 5A, 5B to a position in which one of the lock engaging formations 5A, 5B engages the electrically actuable locking means 4, without the need to power the electrically actuable locking means 4 while the change of position is being made. The bollard apparatus 100 is provided with an electrical power connection means 10. The power connection means 10 may be configured to provide a physical connection, such as suitably arranged electrical contacts (possibly with a removable cover) or an electrical socket provided at the top of the barrier 2. However, in another embodiment the power connection means 10 may be an inductive power transfer receiver which is adapted to receive electrical power from a suitable inductive power transmitter. Where an inductive power receiver is used it is preferably located beneath the top surface of the barrier means 2.

In a basic example of the invention the electrical power connection means 10 may be connected directly to the electrically actuated locking means 4 by a direct electrical path, for example suitable wiring, such that connection of a suitable power source to the electrical power connection means 10 unlocks the electrically actuated locking means 4. In such embodiments the configuration of the socket or inductive power transfer receiver may be of an unusual or proprietary design in order to limit the ability of unauthorised persons from unlocking the electrically actuated locking means 4 and thereby changing the position of the barrier means 2. In a more preferred embodiment the apparatus 100 is provided with a control means 11 which disconnects the electrical connection between the electrical power connection means 10 and the electrically actuated locking means 4 until a piece of user verification information is received. In some embodiments the control means 11 may be microprocessor based. However, simpler electromechanical control means may also be used in some embodiments.

A number of methods of transmitting the user verification information to the control means 1 1 are possible, including: radio frequency transmission; modulation of the electrical power transfer through an inductive power transfer system; modulation of an electrical signal though a physical connection; data transmission via a dedicated separate physical connection, for example a separate electrical connection or an optical connection; and RFID style inductive coupling. In this way only authorised users may unlock the barrier means 2 from the housing 1 and change its position.

The control means 1 1 is preferably microprocessor based, and may store a list of authorised unlocking means identification codes or IDs. Only unlocking means with an ID on the list may be used to unlock the bollard. In some embodiments the ID may be encrypted and the control means may execute a suitable decryption algorithm. In some embodiments a "rolling code" type of algorithm may be used.

In a preferred embodiment the electrically actuable locking means 4, power connection means 10 and control means 1 1 are mounted on, to, or within the barrier means 2. However, in some embodiments (not shown) one or more of these components may be mounted on, to or within the housing means 1. In embodiments which have the electrically actuable locking means 4 mounted to the housing, the barrier member may be provided with lock engaging formations.

In embodiments of the invention in which a control means 1 1 is used and/or in which the power connection means 10 is configured to prevent unauthorised users from applying power to the electrically actuable locking means, the apparatus 100 is preferably part of a system which further comprises an unlocking means 20. In some embodiments the unlocking means 20 may comprise a combined electrical power source and connection means for supplying power to the electrical connection means 11 (for example a portable battery with a suitable connector), which is separate to the apparatus which provides the verification information (for example a cellular phone). In other embodiments the unlocking means may have an integrated power source and source of verification information, for example, but not exclusively, embodiments which transmit an ID over an inductive power link.

It is a feature of preferred embodiments of the present invention that the motive power for energising the electrically actuated locking means 4 is provided by a remote power source. This may reduce the cost of the system, as well as improving its reliability. In preferred embodiments the bollard apparatus 100 does not itself have any power storage components, although in some embodiments a small capacity battery may be provided if required by the control means 11.

In some embodiments the position of the barrier means 2 relative to the housing 1 may be changed manually, that is, without any mechanical assistance. However, in the embodiment shown in Figures 1 and 2 a biasing means such as a coil spring, or more preferably a gas spring 12, may be provided to at least partially offset the weight of the barrier means 2. In a preferred embodiment the biasing means may provide sufficient force to move the barrier means 2 most or all of the way to the extended position without the need for any additional lifting force.

Referring next to Figures 3 and 3A, an alternative embodiment of the invention is generally referenced by arrow 101 , with similar reference numerals referring to similar features as in Figures 1 and 2.

In the embodiment shown in Figure 3 the electrically actuable locking means 21 comprises an electric motor 22 connected to a magnet 23. The magnet 23 is substantially horizontally orientated when the bollard 101 is in use (that is, the magnetic north-south axis of the magnet is substantially horizontal) and is located adjacent an outer surface of the barrier member 2.

Referring in particular to Figure 3A, an elongate locking member 24 is provided inside the housing 1. A first end 25 of the locking member 24 is magnetised or is provided with a permanent magnet 26. An opposite second end 27 of the locking member 24 is rotatably connected to the housing 1 , such that the first end 25 of the locking member 24 can move towards or away from the barrier member 2. The elongate locking member 24 is preferably disposed above the rotatable connection 28 to the housing 1.

In order to lock the barrier member 2 in its raised position, the magnetised portion 26 of the locking member 24 is attracted towards the barrier member 2 by operating the electric motor 22 until the magnetically opposite pole of the magnet 23 is adjacent the magnetised portion 26. When in this position, the locking member 24 engages an engaging portion provided toward the bottom of the barrier member 2, thereby preventing the barrier member 2 from being lowered. In a preferred embodiment the engaging portion may take the form of a rebate 29 in the side of the barrier member.

In order to disengage the locking member 24, thereby allowing the barrier member 2 to be lowered, the user places the unlocking means 20 near the power connection means 10, and operates the unlocking means 20 to send an unlocking signal to the controller 11. If the signal is verified by the controller 11 , the controller operates the motor 22 to rotate the magnet 23 (typically by 180°), thereby reversing the polarity of the portion of the magnet nearest the magnetised portion 26 of the locking member 24. This repels the magnetised portion 26, forcing it out of engagement with the top surface of the rebate 29, and allowing the barrier member 2 to be lowered (against the force of any biasing means 12 present).

Referring next to Figures 4 and in particular 4A, a similar locking member 30 may be provided toward the bottom of the housing 1.

The second locking member 30 is rotatably connected such that the member 30 is disposed below the rotatable connection 31. The locking member 30 is also provided with a magnetised portion 32 (which may comprise a permanent magnet).

The magnetised portion 32 preferably has an opposite polarity to the magnetised portion 26 of the first locking member, so that an orientation of the magnet 23 which repels one of the magnetised portions 26, 32 will attract the other of the magnetised portions 26, 32.

In embodiments in which the barrier member 2 is provided with a biasing means 12 to bias the barrier member 2 upward, the repellent force created between the magnet 23 and magnetic portion 32 of the locking member 30 may not be sufficient to overcome the engagement between the end of the locking member 30 and the lower surface of the rebate 29. In such embodiments it may be necessary to provide an opposing downward force on the barrier member 2 (for example by standing on the upper surface of the barrier member 2) to move the barrier member 2 slightly downward, in order to allow disengagement of the locking member 30 from the rebate 29. This may be advantageous, as it allows the bollard to stay in the lowered position even after it has been "unlocked". Similarly, the barrier member will remain in the raised position even after the upper locking member has been "unlocked", until the barrier member is lowered into the lowered position. This means that an authorised user may use the unlocking means 20 to change the state of the electrically actuated locking means 21 , but may leave the actual change of position of the barrier member 2 from lowered to raised, or from raised to lowered, to be done at a later time, possibly by a different user.

In the embodiment shown in Figures 3-4A, the barrier member 2 may be prevented from rotating relative to the housing, so that the alignment of magnet 23 and the magnetic portion(s) 26, 32 of the locking means is maintained. In some embodiments this may be achieved by the use of barrier members having non-circular transverse cross sections. In other embodiments the barrier member may have a substantially circular cross-section, but may be restrained from rotation in another way.

The embodiment described above may be less susceptible to damage from water and other contaminants than the embodiment shown in Figure 1 and 2, particularly since the motor 22 and magnet 23 can be provided inside a sealed case 33 and so are not exposed to the atmosphere inside the housing 1.

In a preferred embodiment the barrier is provided with a gas spring 12 to bias the barrier member towards the raised position. However, in other embodiments a counterweight 34 may be used, as shown in Figure 5. In this embodiment, generally referenced by arrow 102, the housing 1 is provided with a substantially columnar support means 35 which extends upwardly from the centre of the base 36 of the housing. An upper region of the column 35 is provided with at least one, and more preferably a pair of spaced apart pulleys 36.

The counterweight 34 is provided below the pulleys 36. In a preferred embodiment the counterweight 34 is substantially cylindrical in shape, and has a central passage 37 which is dimensioned to allow the counterweight 34 to slide up and down the column 35. The barrier member 2 is provided with a central void space 38 which can accommodate the pulleys 36 and column 35 when the barrier member 2 is in the lowered position.

Suitable flexible connectors 39, for example a steel braided wire, connect the counterweight 34 to the barrier member 2. In a preferred embodiment the wire is connected to an internal surface 40 of the barrier member toward, but not necessarily adjacent, the base 41 of the barrier member 2. The counterweight 34 may be provided with a second passage or rebate 42 to accommodate the electrically actuable locking means 21 when the barrier member 2 is in the lowered position. Those skilled in the art will appreciate that the downward force exerted by the counterweight 34 will tend to counter the weight of the barrier member 2, thereby reducing or eliminating the force required to lift the barrier member 2 to the raised position (depending on the relative weights of the counterweight and the barrier member 2). An advantage of using a counterweight 34 rather than a gas spring is that the lifting force on the barrier member 2 is the same regardless of the position of the barrier member 2.

All of the embodiments described above require a means of venting air which is trapped between the barrier member 2 and the housing 1. In the embodiment shown in Figure 5, this may take the form of a simple aperture 43 in the side wall of the barrier member 2. However, in other embodiments (not shown) the barrier member 2 is provided with an internal vent passage which extends from a position adjacent the base of the barrier to one adjacent the top of the barrier. In a preferred embodiment the vent opens to a side wall of the barrier member 2. In preferred embodiments the vent opening is below the upper seal when the barrier is in the lowered position, in order to minimise ingress of contaminants into the vent passage. In a particularly preferred embodiment the portion of the vent passage immediately adjacent the opening in the barrier side wall 2 may slope upward, in order to prevent water from flowing into the vent.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to".

Where in the foregoing description, reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are herein incorporated as if individually set forth.

Although this invention has been described by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the spirit or scope of the appended claims.