GB2334752A

GB2334752A - A barrier drive mechanism

Info

Publication number: GB2334752A
Application number: GB9904297A
Authority: GB
Inventors: Patrick Doherty; John Alphonsus Walsh; Kevin Michael O'brennan
Original assignee: ELECTRO AUTOMATION RESEARCH
Current assignee: ELECTRO AUTOMATION RESEARCH
Priority date: 1998-02-26
Filing date: 1999-02-25
Publication date: 1999-09-01
Anticipated expiration: 2019-02-25
Also published as: GB2334752B; IE990142A1; IES990143A2; GB9904297D0; IES81183B2

Abstract

An upwardly pivotable barrier beam is driven by a conrod (11) connected to a crank wheel (10) which is in turn driven by a drive wheel (21) by virtue of frictional engagement. The drive wheel (21) is driven by a combined motor/gearbox unit (17) having a common casing and which is secured to a connector (25) which in turn pivotally connects the unit to a fixed support (6) at a pivot pin (30). The arrangement is simple, compact and inexpensive.

Description

"A Barrier Drive Mechanism" The invention relates to a barrier drive mechanism for a barrier of the type comprising a beam which moves in a substantially vertical plane, and in which the drive mechanism comprises: a fixed support for anchoring to the ground, a crank wheel for driving the beam, and a drive wheel engaging the crank wheel and being driven by a motor, the drive wheel being mounted such that weight bears on the crank wheel to provide frictional engagement of the drive wheel with the crank wheel.

Such a mechanism is described in PCT Patent Specification No. WO 92/05314 (Sine Engineering Limited). In this prior art mechanism, when the friction or drive wheel is driven to rotate the crank wheel to raise the beam, the frictional force between the drive wheel and the crank wheel is increased, whereas the frictional driving force is reduced when the drive wheel is rotated in the reverse direction. This is a very effective arrangement. A major advantage is the fact that the mechanism slips when an obstruction is encountered by the beam.

However, referring to Fig. 2 of the above specification, the drive or friction wheel is driven by a motor having an output worm shaft, which in turn drives a gear, which in turn drives the drive wheel. The motor is supported by a support plate 8, which is connected by a pivot pin 9 to a fixed support. It is clear from this specification that the motor (11) is supported by the plate 8 by virtue of a bracket. It is not, however, clear how the gear wheel between the motor output worm shaft and the drive wheel 7 is supported.

However, it is stated that the weight of the motor (11) bears down on the crank wheel (6) via the drive wheel (7). Therefore, it appears that there is a coupling between the intermediate wheel and the drive wheel (7) which causes the weight of the motor (7) and the intermediate wheel to be transferred via the plate (8) to the drive wheel (7). It appears that such an arrangement is relatively expensive because such couplings are expensive to purchase and to install in the drive mechanism. It also appears that over time the engagement between the motor (11) and the intermediate wheel may slip to some extent after thousands of cycles.

It is therefore an object of the invention to provide a drive mechanism which is of simpler construction.

According to the invention, there is provided a barrier drive mechanism for a barrier of the type comprising a beam which moves in a substantially vertical plane, the drive mechanism comprising: a fixed support for anchoring to the ground; a crank wheel for driving the beam; a drive wheel engaging the crank wheel and being driven by a motor, the drive wheel being mounted such that weight bears on the crank wheel to provide frictional engagement of the drive wheel with the crank wheel, wherein the motor and the drive wheel are supported as an assembly by a common support which is in turn pivotally connected to the fixed support.

Because the motor and the drive wheel are supported by a common support, the drive wheel and the motor are connected together as a unitary assembly which need only be supported directly by the common support. This is a much simpler and less expensive arrangement than the prior art.

In one embodiment, the assembly support is a casing for the motor. Such an arrangement is possible if the distance between the drive wheel and the motor is sufficiently small to avoid an excessive turning moment arising at the wheel.

In one embodiment, the motor incorporates a gearbox at its output. Such a unit is readily available "off the shelf".

In one embodiment, the assembly support is pivotally connected to the fixed support by a connector.

Preferably, the connector comprises a flange which extends around the motor output shaft and is secured to the assembly support. This provides excellent balance and helps to avoid fatigue stresses arising in the drive assembly.

In one embodiment, the connector comprises a sleeve which receives a pivot pin extending through the fixed support.

Preferably, the sleeve extends from the flange in a direction orthogonal to the plane of the flange.

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which: Fig. 1 is a front view of a barrier drive mechanism of the invention; Fig. 2 is a perspective view of part of the mechanism; Fig. 3 is a diagrammatic front view showing parts of the mechanism; and Figs. 4 and 5 are perspective views from different angles of a connector of the mechanism.

Referring to the drawings, there is shown a drive mechanism 1 for a barrier of the type having a beam which moves in a substantially vertical plane. The mechanism is indicated generally by the numeral 1 and is shown in Fig. 1 connected to drive a beam 2.

The beam 2 is pivotally connected by a beam pivot joint 3, to which is also connected a lever 4. A counter-balancing spring 5 is connected to the lever 4. The beam pivot joint 3 is between the beam 2 and the lever 4 and a fixed support 6 which is anchored to the ground by a base plate 7. A base pin 8 is connected to the base plate 7 and this supports the counter balancing spring 5.

The mechanism 1 comprises a crank wheel 10 which rotates in 1800 sweeps to rotate the lever 4 via a con rod 11. The crank wheel 10 is pivotally connected to the fixed support 6 by a pivot pin 12, shown in Fig. 3.

The mechanism 3 also comprises a drive assembly 15 which is electrically driven via a cable 16 by a power supply, not shown. The assembly 15 comprises a motor and a gearbox unit 17 having a motor section 17(a) and a gearbox section 17(b). A flange 19 is connected to the casing 18 at the end of the gear box section 17(b). A motor output shaft 20 extends through this flange and terminates at a drive wheel 21 which rests on the crank wheel 10 with frictional engagement.

The drive assembly 15 is pivotally connected by a connector 25 to the fixed support 6.

The connector 25 comprises a flange 26 which has bolt holes 27 and it is bolted at these holes to the casing flange 19. The flange 26 also includes an extension 28 for use as a handle to allow the assembly to be removed for maintenance The connector 25 also comprises a sleeve 29 through which extends a pivot pin 30 which engages a bearing in the fixed support 6, shown most clearly in Fig. 2.

The drive assembly 15 is a single physical unit which is supported on the pivot pin 30 in a manner whereby its weight bears against the crank wheel 10 via the drive wheel 21.

This provides a strong frictional engagement between the drive wheel 21 and the crank wheel 10. The connector 25 engages the casing 18 of the motorlgearbox unit 17 in a balanced and symmetrical manner so that it effectively becomes part of the casing 18 so that the whole drive assembly 15 is supported by a single common support which is directly pivotally connected to the fixed support 6. There is no need for a drive coupling and it will also be appreciated that the connector 25 is very simple. Because there is no need for a drive coupling and also because the connector is very simple, the drive mechanism 1 is relatively simple and inexpensive to produce. Also, because of the inherant balance provided by the configuration of the connector 25, there is little wear on the motor output shaft and internal bearings and the rnechanism is very reliable.

The invention is not limited to the embodiments described but may be varied in construction and detail within the scope of the claims.

Claims

Ciaims 1. A barrier drive mechanism for a barrier of the type comprising a beam which moves in a substantially v vertical plane, the drive mechanism comprising:- a fixed support for anchoring to the ground; a crank wheel for driving the beam; a drive wheel engaging the crank wheel and being driven by a motor, the drive wheel being mounted such that weight bears on the crank wheel to provide frictional engagement of the drive wheel with the crank wheel, wherein the motor and the drive wheel are supported as an assembly by a common support which is in turn pivotally connected to the fixed support.
2. A mechanism as claimed in claim 1, wherein the assembly support is a casing for the motor.
3. A mechanism as claimed in claim 2, wherein the motor incorporates a gearbox at its output.
4. A mechanism as claimed in any preceding claim, wherein the assembly support is pivotally connected to the fixed support by a connector.
5. A mechanism as claimed in claim 4, wherein the connector comprises a flange which extends around the motor output shaft and is secured to the assembly support.
6. A mechanism as claimed in claim 5, wherein the connector comprises a sleeve which receives a pivot pin extending through the fixed support.
7. A mechanism as claimed in claim 6, wherein the sleeve extends from the flange in a direction orthogonal to the plane of the flange.
8. A mechanism substantially described with reference to the drawings.