GB2485414A - Shear friction brake for an access control barrier - Google Patents

Abstract

A braking mechanism for an access control barrier, comprising two bodies 10 11 constrained to move relative to each other in a generally linear manner A with a fictional shear force generated between the two bodies for restricting movement and a method of attaching one of the bodies to the barrier. Preferably the force is a magnetic force, for example an electromagnetic force wherein one of the bodies is an electromagnet and the other is a magnetic material. One of the bodies 10 is preferably connected to a rotary to linear convertor, for example a crank mechanism 14 which is then connected to a rotatable shaft 4 connected to the barrier. Preferably the shear force is a maximum value when the two bodies are most in register and decrease as the two bodies are displaced. Preferably rails, barriers, runners or rollers are used to cause the linear movement of the bodies. The brake mechanism locks the access gate in a locked position until the electromagnet is deactivated allowing movement of the barrier.

Description

Access Control Barriers This invention relates to access control barriers. In particular, it relates to braking system for access control barriers.

Figure 1 shows one example of an access control barrier. This comprises a pair of planar barriers 1, 2 being connected to a respective shaft 3, 4 so that the respective physical bathers can rotate about the vertical axis of the shaft in order to allow a person entry through the passageway defined between the shaft, or to block the passage when the two barrier generally face one another (in the position shown in Figure 1). The barriers are arranged to open when a person is allowed access and this may be done by a security card or other person operating suitable electronic means for causing the barriers to open, or by the pass itself having perhaps having machine readable ID, entering a PIN at a suitable location or otherwise which causes the barriers to open.

The shafts includes a motor mechanism for causing them to rotate and thus bring the bathers with them.

The bathers will often be of glass or other transparent or translucent material.

A braking system is usually required so that when the barriers are in the closed position as shown in Figure 1, a person cannot simply push them open without using a high degree of force. The amount of force necessary to force them open should be balanced however so that one cannot simply break the bathers or their connection or their joint at the shafts. Up to now, the braking mechanism has often been a friction magnetic brake and this is shown schematically in Figure 2. This comprises an electromagnet 5 which is positioned in register with a metal or other plate 6 mounted to the drive mechanism of the shaft and which can rotate therewith. When the plate is drawn towards the electromagnet it is prevented from relative rotational movement therewith until certain force is applied, after which it will generally rotate. This therefore acts as a brake. The force required to overcome the brake will of course depend largely upon the relative size of the braking area and therefore the diameter of the plate 6 and electromagnet 5. With typical practical implementations, this force may be around 100 N. S It is becoming more common to desire that a greater force is required before the friction brake is overcome and present systems cannot cope with this easily. The present invention arose in an attempt to provide an improved braking system.

According to the present invention there is provided an access barrier including at least one rotatable shaft enabling a barrier to rotate, a means for converting rotary motion of the shaft to a linear motion, a body constrained to move in a generally linear manner relative to a second body and connected to the rotary to linear converter, whereby the first and second plates are adapted to generate a frictional shear force between them, the amount of which is determined at least partially by the relative amounts of each which overlap.

Preferably, the bodies are subject to a magnetic force. The magnetic force may be generated by one of the bodies having means for generating an electromagnetic force and the other being of a material which is attracted to a magnetic surface.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which: Figure 1 shows an access control barrier; Figure 2 shows a friction brake; Figure 3 shows a linear friction brake; Figure 4 shows a cross-sectional side view; Figures 5(a) to 5(c) show respective different relative positions of part of a linear brake; and Figures 6(a and 6(b) show alternate positions of an access barrier and linear brake.

An access control barrier embodying the invention may be generally as shown in Figure 1, although of course it may have many other types of configuration.

In some embodiments, there may only be one shaft 4 and bather 2 and the shaft and bather may be of many different types. They may be of an integral construction and the bather may simply be a relatively thin member or of any other shape or construction.

Electromagnetic beams may be arranged to be transmitted and received across the passageway and many other types of configuration will be apparent.

Figures 3 and 4 show a linear brake assembly. A metal plate 10 (or alternatively a plate or other structure which may be of or comprise or includes a material which is attractive to a magnet) is positioned generally in register with an electromagnetic member 11. Figure 3 shows a top view of the plate 10 and Figure 4 shows a side view or cross-section. The plate is constrained by barriers 12 and 13 to move in a generally linear manner in a direction of its axis A. The electromagnetic member 11 may be turned ON and OFF to generate an electromagnetic force which attracts the plate 10. Alternatively, of course, the plates 10 may be electromagnet and the member 11 magnetically attracted thereto.

The plate 10 is constrained to move generally in linear direction A. This may be by bather 12, 13 which can be simply walls or rails constraining the motion of the plate. In some embodiments, only one such barrier may be required or in other embodiments different types of constraining methods may be used. Of course, there will be generally be a tolerance resulting in a small gap between the outside edge l0a of plate 10 and inside edge 12a of a barrier and thus the motion may not be strictly linear but will generally be in the linear direction or at least have a component, preferably a major component, in that direction. Otherwise, the plate is preferably allowed to move freely relative to the electromagnetic body 11. Note that the electromagnetic body may alternatively be a permanent magnet and might even have some other way of achieving a shear force, or a shear resistance with the plate 10. The shear force is of course caused by frictional properties of the materials.

The plate is connected to the shaft 4 of an access barrier by means of a linkage or other means which can convert rotary motion of the shaft into linear motion. This may be by a crank arrangement as shown generally in Figures 3 and 4. In this arrangement, a crank comprises a first arm 14 and a second arm 15. The first ann is connected to a pivot point 16 mounted on the plate 10. This will typically be at a central position both longitudinally and laterally but may be in any other position. The pivoting may be achieved by means of a pivot pin 16 which locates within a slot 17 at one end of arm 14, or by any other convenient means of achieving a pivoting motion.

A further pivot 18 is arranged remote from first pivot 16, typically at the end of arm 14 although it may be positioned at any position along arm 14. One end of arm 15 (or another part of arm 15) is connected to this pivot point such that the two arms 14 and 15 can pivot relative to one another. The other end of arm 15 is then connected to (or may be integral with) a shaft 14. It need of course not be physically connected to the shaft 14 and could be mounted via a bracket or any other means to the shaft or any other suitable connection or mechanism which allows the end of arm 15 which is closest to the shaft 4 to rotate with shaft 4.

The arm arrangement 14 and 15 therefore forms a crank. Because this is held at a fixed pivot point 16 at one end rotates with shaft 4 at the other end has parts able to pivot relative to one another about pivot 18, thus causes rotary motion of the shaft to be converted into linear motion moving the pivot point 16 away from or towards the shaft 4.

Since the pivot point is fixed relative to plate 10, movement of the pivot point thus causes plate 10 to move backwardly and forwardly.

The degree of movement is of course dependent upon the amount of rotary movement of the shaft, and the relative size and dimensions of the various parts of the crank arrangement.

The apparatus is most preferably arranged such that when the barriers 1, 2 are in the closed position shown in Figure 1 (where their ends are closest to one another) the plate 10 is in register, or at least overlies to a greatest extent, the magnetic body 11. Thus, if the magnetic body is actuated, the fullest magnetic attraction force is exerted upon plate 10. A large shear force is then exerted which means that if a user tries to push upon one or other S of the barriers 1 and 2 the shear force between bodies 10 and 11 resist this. Since body 10 is connected to the bather via the crank mechanism and shaft, there will be a braking force but the force, for a similar surface area of plate 10 to the surface area involved in the prior art braking arrangement as shown in Figure 2, will be much more, perhaps five times as greater. Thus, a much greater force must be exerted to overcome the magnetic shear force in embodiments of the invention, for a similar sized braking mechanism, to that of the prior art.

When an access barrier is released to open, the electromagnet is switched off and therefore the plate 10 can freely slide in a general relative to plate 10.

However, if the electromagnetic force is kept applied, then there will be an automatic compensation as the barriers move from the closed position to the fully open position by virtue of the fact that, as shown in Figures 5(a) to (c) when the barrier is rotated in one direction the plate 10 is caused to move in one direction relative to the body 11 and when it is rotated in the other direction it is pulled in the respective opposite direction.

Thus, as shown in Figure 5(a) when in a closed position the plate 10 is in register with body 11 and so the greatest amount of its surface area is acted upon directly by the magnetic force, leading to the greatest magnetic shear force. If the barrier is moved towards an open position the plate is moved, say to the left in Figure 3, leading to a situation as shown schematically at Figure 5(b) where the plate extends beyond the edge of the magnetic body 11. Thus, the actual amount of surface area of the plate which is directly affected by the magnet shown as S2 is less than Si of Figure 5(a). Hence, the shear force acting upon plate is less and therefore the force required to overcome this is less. Similarly, if the plate is moved in the other direction, then the affected surface area S is also less Si.

Note that in embodiments the plate 10 need not be exactly the same size as body II.

It is the relative surface area which is directly affected by the shear force that is relevant.

Figure 6(a) and (b) illustrates this in a little more detail. Figure 6(a) shows a position where a bather arm 2 is in the closed position and the plate 10 is in a first position 10(a). As the barrier arm and shaft are rotated to an open position shown in Figure 6(b) where a person may pass through a passageway, the rotary to linear mechanism causes the plate 10 to move to position 10(b) which is linearly displaced relative to position 10(a).

Note that the means for constraining the plate to move in a generally linear direction may be rail bars, runners, rollers or many other configurations. There may be constraining means on just one side or both sides, eg 12 or 13 in Figure 3 may be omitted. A rising or retracting barrier may be used.

In some embodiments, the magnetic lock armature (ie electromagnetic body) may be fitted to a chassis of the access control mechanisms. The metal plate is then retained or constrained for linear motion using bathers, rollers, wheels or other means. The angular rotation of the barrier shaft is then translated into a linear motion using a suitable rotary to linear linkage.

At the barrier closed position, the metal plate is most preferably positioned in the optimum position for maximum shear force when the armature is energised.

The invention may of course be applied to one or to more linear friction brake systems.

In some embodiments, a conventional rotary braking system may be used in addition to the present invention.

In general much improved braking performance for a given width space envelope is achieved with linear arrangement than with prior art arrangements, eg for a given width of linear moving element, the system provides greater braking force for a conventional rotary braking system of the same width or diameter. That is, compared to a simple rotary brake, an arrangement embodying the present invention occupies less physical space in the direction of the opening which allows the pivot point to be moved towards the lane opening, which can enable smaller amounts of closure glass to be used (ie smaller barriers) and overall smaller enclosure width.

Claims (9)

1. Claims 1. A braking mechanism for an access control barrier, comprising two bodies constrained to move relative to each other in a generally linear manner and means for generating a fictional shear force between the two bodies, and means for connecting one of said bodies to a barrier.
2. 2. An access barrier including at least one rotatable shaft enabling a barrier to rotate, a means for converting rotary motion of the shaft to linear motion, a body constrained to move in a generally linear manner relative to a second body and connected to the rotary to linear converter, whereby the first and second bodies are adapted to generate a frictional shear force between them, the amount of which is determined at least partially by the relative amounts of each which overlap.
3. 3. Apparatus as claimed in Claim 1 or Claim 2, wherein the frictional shear force is a magnetic force.
4. 4. Apparatus as claimed in any preceding claim, wherein the magnetic force is generated by one of the plates having an electromagnetic force generating means and the other being of a material which is attracted to a magnetic surface.
5. 5. Apparatus as claimed in any of Claims 2 to 4, wherein the rotary to linear converter is a crank mechanism.
6. 6. Apparatus as claimed in any preceding claim, wherein the arrangement is such that the shear force between the two bodies is at a maximum value when the two bodies are most in register and decrease as the two bodies are displaced to a position less in register.
7. 7. Apparatus as claimed in any preceding claim, wherein the bodies are constrained for generally linear movement by rail means, one or more barriers, one or more runners or rollers or other means.
8. 8. Apparatus as claimed in any preceding claim, wherein for a given width linear moving body the apparatus provides a greater braking force than a rotary brake of the same width.
9. 9. Access control apparatus substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.