ACCESS CONTROL SYSTEM

Abstract

An access control system for restricting access through a passageway includes a shaft rotatable about a central axis; a barrier fixed to the shaft to rotate therewith; and a brake assembly. The brake assembly includes a sun gear rotatable about the central axis, a carrier, and a ring gear, wherein one of the carrier or the ring gear is fixed against rotation and the other of the carrier or ring gear is connected to the shaft to rotate therewith. A plurality of planet gears are rotatably connected to the carrier, each planet gear being disposed between and engaging with each of the sun gear and the ring gear. The armature of an electromagnetic brake comprising an electromagnet and an armature is connected to or integral with the sun gear to rotate therewith. At least one of the electromagnet or the armature is moveable between an operative and an inoperative position.

Claims

1. An access control system for restricting access through a passageway, the access control system comprising: a shaft which is rotatable about a central axis, a barrier fixed to the shaft to rotate therewith, and a brake assembly for applying a braking force to the shaft, wherein the brake assembly comprises: a sun gear which is rotatable about the central axis of the shaft; a carrier and a ring gear, wherein one of the carrier or the ring gear is fixed against rotation and wherein the other of the carrier or the ring gear is connected to the shaft to rotate therewith; a plurality of planet gears rotatably connected to the carrier so as to permit rotation relative to the carrier, each planet gear being disposed between the sun gear and the ring gear and engaging with each of the sun gear and the ring gear; and an electromagnetic brake comprising an electromagnet and an armature, the armature being connected to or integral with the sun gear to rotate therewith, wherein at least one of the electromagnet or the armature is moveable upon energization of the electromagnet between an operative position in which the electromagnet and the armature are in contact, and an inoperative position in which the electromagnet is spaced from the armature.

2. The access control system as claimed in claim 1, wherein the electromagnet is fixed against axial movement and wherein the armature is biased to the inoperative position.

3. The access control system as claimed in claim 2, wherein the brake assembly further comprises a spring positioned between the armature and the sun gear.

4. The access control system as claimed in claim 3, wherein the spring is arranged to bias the armature to the inoperative position.

5. The access control system as claimed in claim 4, wherein the spring is a disc spring or spring plate.

6. The access control system as claimed in claim 1, wherein the sun gear is centered on the shaft and is rotatable relative to the shaft.

7. The access control system as claimed in claim 6, wherein the sun gear is moveable relative to the shaft in an axial direction of the shaft.

8. The access control system as claimed in claim 1, further comprising a bearing located in a body of the electromagnetic brake and holding the shaft.

9. The access control system as claimed in claim 1, further comprising a motor arranged to drive the shaft.

10. The access control system as claimed in claim 9, wherein the carrier is fixed to or integral with a pulley wheel, the pulley wheel being connected to the motor so as to transmit rotational motion of the motor to the shaft.

11. The access control system as claimed in claim 1, comprising at least eight planet gears.

12. The access control system as claimed in claim 1, wherein one or more of the sun gear, ring gear and planet gears is formed of a plastic material.

13. The access control system as claimed in claim 1, further comprising a control unit configured to control the movement of the armature between the operative and inoperative positons.

14. The access control system as claimed in claim 13, wherein the control unit is programmed to: receive a signal providing an instruction to move the barrier; control the electromagnetic brake to move the armature into the inoperative position, in response to receipt of said signal; and control the shaft to rotate once the armature has been moved into the inoperative position.

15. The access control system as claimed in claim 14, further comprising an authorisation unit configured to generate said signal providing an instruction to move the barrier.

16. The access control system as claimed in claim 15, wherein the authorisation unit is an identification card reader.

17. The access control system as claimed in claim 13, further comprising a sensor for detecting movement of the barrier or pressure applied to the barrier when the armature is in the operative position.

18. The access control system as claimed in claim 17, further comprising an alarm, wherein the control unit is programmed to activate the alarm in response to the detection of movement of the barrier and/or pressure applied to the barrier when the armature is in the operative position.

Description

DESCRIPTION OF THE DRAWINGS

[0040] Non-limiting embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0041] FIG. 1A is a perspective view of an access control system in accordance with the present invention;

[0042] FIG. 1B shows the access control system of FIG. 1, with the brake assembly in exploded view;

[0043] FIG. 2 is enlarged view of the exploded brake assembly of FIG. 1B;

[0044] FIG. 3 is a vertical cross section of the brake assembly;

[0045] FIG. 4 is a horizontal cross section of the brake assembly through line IV-IV shown in FIG. 3;

[0046] FIG. 5 is a plan view of an access control system according to the present invention; and

[0047] FIG. 6 is a cross-section of the access control system of FIG. 5 through line VI-VI indicated in FIG. 6.

DETAILED DESCRIPTION

[0048] With reference to FIGS. 1A and 1B, there is shown an access control system 1, comprising a shaft 10, which is rotatable about a central axis A, and a barrier 12 fixed to the shaft 10 to rotate therewith. In use, the barrier 12 is arranged to extend across a passageway to restrict access through the passageway. In order to permit access through the passageway, the shaft 10 is rotated causing the barrier 12 to move out of the passageway. The passageway may be any entry portal or gate through which a person must pass to enter a building or any other restricted area. Typically, persons requiring access through the passageway must be authorised, with the authorisation process either being automated, for example by means of an identification card reader or facial recognition system, or may be manually operated by a user, such as a porter or guard, upon presentation of appropriate authorisation.

[0049] In order to prevent the barrier 12 from being forced open, for example by a person pushing the barrier 12, a brake assembly 14 is provided, which, when active, applies a braking force to the shaft 10 thus preventing the barrier 12 from being moved. FIG. 1B shows the access control system 1 with the components of the brake assembly 14 in exploded view.

[0050] The brake assembly 14 is shown in more detail in FIGS. 2 and 3. The brake assembly 14 comprises a carrier 16 fixed to the shaft 10 such that the carrier 16 rotates with the shaft 10, and vice versa. Accordingly, in some embodiments such as that shown in FIG. 2, the carrier 16 is a pulley wheel having an outer circumferential surface 16a arranged to engage with a belt (not shown) for transferring rotational motion of a motor (not shown) to the carrier 16 and, therefore, also to the shaft 10. Accordingly, the shaft 10 is driven by the motor via the carrier 16. Alternative embodiments may comprise other means for driving the shaft 10.

[0051] The brake assembly 14 further comprises a planetary gear train including a sun gear 18 arranged coaxially with the shaft 10 and rotatable about the central axis A of the shaft 10 and a ring gear 20 which is fixed against rotation by means of mounting bracket 21, which can be secured to a frame or surround of the access control system, or any other appropriate fixed structure. A plurality of planet gears 22 are rotatably connected to the carrier 16 so as to permit rotation of each planet gear 22 relative to the carrier 16 about an axis parallel to the central axis A of the shaft 10.

[0052] As shown most clearly in FIG. 4, each planet gear 22 is disposed between the sun gear 18 and the ring gear 20 and engages with each of the sun gear 18 and the ring gear 20 via the teeth thereof. In use, the planet gears 22 are driven between the fixed ring gear 20 and rotatable sun gear 18 when the shaft 10 and carrier 16 are rotated. Rotation of the shaft 10 and carrier 16 is therefore transferred to the sun gear 18 via the planet gears 22, with the sun gear 18 rotating at a greater speed than the shaft 10.

[0053] Referring again to FIGS. 2 and 3, an electromagnetic brake 24 comprising an armature 26 is provided to apply a braking force to the sun gear 18. In the illustrated embodiment, the armature 26 of the electromagnetic brake 24 is connected to the sun gear 18 via an adaptor plate 28 and a disc spring 30 such that the armature 26 rotates with the sun gear 18. The disc spring 30 is arranged to bias the armature to an inoperative position, that is, a position in which there is an operation clearance between the armature 26 and a friction surface 32a of an electromagnet 32. The friction surface 32a is therefore a friction member which is fixed against rotation. This operational clearance permits free rotation of the armature 26, and thus the sun gear 18, relative to the electromagnet 32, which is fixed against rotation. This position of the armature 26 is referred to as the inoperative position i.e. there is no braking force applied to the sun gear 18 by the armature 26.

[0054] The armature 26 is magnetic. When the electromagnet 32 is energised, the armature 26 is pulled under electromagnetic attraction toward the electromagnet 32, which includes an electromagnetic coil (not shown). This movement of the armature is permitted by the disc spring 30. The biasing force of the disc spring 30 towards the sun gear 18 and adaptor plate 28 is overcome by the electromagnetic attraction towards the electromagnet 32, such that the armature 26 is brought into frictional contact with the friction surface 32a against the bias of the disc spring 30. Accordingly, a braking force is applied to the armature 26 by means of the frictional contact between the armature 26 and the friction surface 32a, and the magnetic force pulling the armature 26 towards the electromagnet 32. The armature 26, in turn, provides a braking force to the sun gear 18 via the disc spring 30 and adaptor plate 28. This position of the armature 26 is referred to as the operative position i.e. the armature 26 is brought into contact with the electromagnet 32 such that a braking force is applied to the sun gear 18 by the armature 26. In the above arrangement, the brake is actuated by energising the electromagnet 32 (a so-called “power-on” electromagnetic brake), meaning that in the event of a power failure the electromagnetic brake 32 will release permitting the barrier to be opened (i.e. the access control system is “fail-safe”).

[0055] The arrangement described above is preferred due to its uncomplicated construction and the strong braking force which it provides, whilst ensuring that the access control system remains fail-safe. However, it will be appreciated that other arrangements would be conceivable to the skilled person, in which an armature and an electromagnet are relatively movable between an operative position in which the armature is in contact with the electromagnet to provide a braking force to the sun gear, and an inoperative position in which the armature is spaced from the electromagnet, such that the armature provides no braking force to the sun gear. For example, the electromagnet may be fixed against rotation but permitted to move axially upon energisation of the electromagnet so as to make contact with the armature and apply a braking force to the sun gear. Further alternative arrangements of the brake assembly will be conceivable to the skilled person, without deviating from the scope of the present invention.

[0056] Referring again to the embodiment shown in FIG. 4, a shaft bearing 34 is housed within the body of the electromagnet 32. The sun gear 18 is centred on the shaft 10 and is rotatable relative to (i.e. around the shaft). Accordingly, rotational movement of the shaft 10 is not transferred directly to the sun gear 18 or vice versa (such rotational movement only being transferred by means of the planetary gear train, as described above). The sun gear 18 rotates at a greater speed than the shaft 10 at a speed ratio corresponding to the gear ratio of the planetary gear train.

[0057] The gear ratio of a planetary gear train is dependent upon the number of teeth of the sun gear and the ring gear. Where the ring gear is fixed against rotation, the gear ratio can be determined according to the equation:

R=1/(1+N.sub.R/N.sub.s)

where R is the gear ratio, N.sub.R is the number of teeth of the ring gear and N.sub.s is the number of teeth of the sun gear.

[0058] In the illustrated embodiment, the gear train comprises a ring gear having 60 teeth, a sun gear having 36 teeth and eight planet gears each having 12 teeth. Therefore, this arrangement provides a gear ratio of 1:2.67. Accordingly, the sun gear 18 rotates 2.67 times faster than the shaft 10.

[0059] The torque of the sun gear 18 is reduced by the same ratio, relative to the torque of the rotating shaft 10. Accordingly, the braking force required to prevent rotation of the sun gear 18 at a given torque is significantly reduced. A person attempting to force the barrier 12 open will apply a force to the barrier 12 at a given perpendicular distance from the central axis A of the shaft 10, which results in a potentially very large torque being generated about the central axis A of the shaft 10. If a person attempts to force the barrier 12 open when the brake is actuated (i.e. the electromagnet 24 is energised and the armature 26 is in the operative position), the necessary braking force that must be applied to the to the sun gear 18 in order to withstand this potentially very large torque applied to the shaft 10 is greatly reduced. This means that the overall dimensions of the electromagnetic brake (in particular, the surface area of the engaging surfaces of the armature 26 and electromagnet 32) can be minimised, as can the required strength of the magnetic field induced by the electromagnet 24. Thus, not only can the brake be reduced in size, the power consumption of the electromagnetic brake can also be reduced.

[0060] Due to the spline effect of the gears, the sun gear 18 is able to move relative to the shaft 10, the ring gear 20 and the planet gears 22 in an axial direction of the shaft 10 (vertically as shown in FIG. 3). Accordingly, the working gap of the electromagnetic brake 24 (i.e. the operational clearance between the engaging surfaces of the armature 26 and the electromagnet 32) can be adjusted independently of the position of the shaft 10. This allows easy and reliable optimisation of the brake gap. This may be achieved, by way of example, using simple sprung components (not shown). The armature 26 can thus be easily positioned so that it is clear of the friction surface 32a of the electromagnet 32 when the electromagnet 32 is de-energised, but also such that the operational clearance is sufficiently small to ensure that the armature 26 moves to engage with the friction surface 32a when the electromagnet 32 is energised.

[0061] With reference to FIGS. 5 and 6, there is shown a further embodiment of an access control system 1 in accordance with the present invention, with corresponding features being indicated with like numerals. The access control system 1 comprises two walls 34, 36 defining a passageway 38 between them. The barrier 12 extends across the passageway 38 from one of the walls 34, substantially perpendicularly to said wall 34. Alternative embodiments of the present invention may comprise two or more barriers, with at least one barrier extending across the passageway from each of the walls. The barrier 12 is attached to the shaft 10, which is rotatably mounted within the wall 34, such that the barrier 12 is capable of movement within the passageway in a first direction D1 and a second direction D2.

[0062] FIG. 6 shows a schematic cross section of the access control system 1 through line VI-VI indicated in FIG. 5. The barrier 12 is attached to the shaft 10 by means of brackets 40. The access control system 1 comprises a brake assembly 14 as described in detail above. A motor 42 is provided for controlling the rotation of the shaft 10 via a pulley belt 44. The pulley belt 44 may be connected to the carrier 16 of the brake assembly 14, as described above, or may alternatively be connected to any other component in a manner which enables the motor 42 to drive the shaft 10. In alternative embodiments the shaft 10 may be driven directly by a motor.

[0063] The access control system 1 comprises an authorisation unit 46 in the form of an identity card reader positioned on the upper surface of the wall 34. Alternative embodiments may comprise any appropriate means for authorising access through the passageway, such that the passage of people through the passageway is permitted only for authorised persons. The means may be automatic (for example, a facial recognition system), permitting passage of an authorised person without the need for interaction by any other person, or may be controlled by, for example, a porter guard who authorises access manually. Multiple means for authorising access may be provided.

[0064] The access control system 1 further comprises a control unit 48 which is electronically connected to each of the brake assembly 14, the motor 42 and the identity card reader 46. Whilst the control unit 48 is shown externally of the wall 34, it will be appreciated that the control unit 48 may be housed within the wall 34 together with the other components of the access control system 1.

[0065] An exemplary procedure for controlling access through the passageway will now be described. At first, the access control system 1 is configured such that the barrier 12 extends across the passageway 38 so as to prevent a person passing through the passageway 38 without first opening the barrier 12. The brake assembly 14 is configured such that the armature 26 is in the operative position as described above, such that the brake assembly 14 is in an actuated state. Accordingly, in the operative state, if a person attempts to push or pull the barrier 12 open in either direction D1 or D2, the braking force applied to the sun gear 18 of the brake assembly 14 by the armature prevents the shaft 10 from rotational movement and thus prevents the barrier 12 from being opened.

[0066] In order to gain access, an authorised person presents an identity card to the identity card reader 46, which transmits information relating to the owner of the identity card to the control unit 48. The control unit 48 processes said information in order to determine whether or not the owner of the identity card is an authorised person and, if so, send a signal to the brake assembly 14 to move the armature 26 from the operative position to the inoperative position. Accordingly, the braking force to the sun gear 18 is released and the sun gear 18 and shaft 10 are free to rotate. The control unit 48 also sends a signal to the motor 42 to drive the shaft 10 such that the barrier 12 opens, allowing access through the passageway 38. The control unit 48 is further configured the send a signal to the motor 42 to drive the shaft 10 so as to close the barrier 12, either after a predetermined time period, or alternatively once it has been determined that the authorised person has passed through the passageway 38, for example using additional sensors configured to detect the presence of a person within the passageway 38.

[0067] The invention has been described above with reference to specific embodiments, given by way of example only. It will be appreciated that different arrangements of the system are possible, which fall within the scope of the appended claims.