GB2236142A

GB2236142A - Gate operating mechanism

Info

Publication number: GB2236142A
Application number: GB8919158A
Authority: GB
Inventors: Cheong Bian Ng
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-08-23
Filing date: 1989-08-23
Publication date: 1991-03-27
Also published as: GB8919158D0

Abstract

An operating mechanism suitable for gates, doors and turnstiles, and which may be embedded in the ground, includes a motor 15 driving a gear box 17 whose output shaft 16 turns arm 19 linked to gate 20 by a cylinder 31. The cylinder is pivotable, under bias of spring 33, on the arm between a horizontal position in which it is disengaged from the gate and an upright position in which it is freely engaged in a gate channel 36. Arm 19 has a clamp end which is secured to sleeve 21 rotatable on the shaft 16. Drive is transmitted from shaft 16 to sleeve 21 by a plate 23 having projection 24 biased by adjustable springs 26 into grooves 25 in shaft 16 and sleeve 21. The drive connection is interrupted if projection 24 is cammed out of grooves 25 against springs 26 by high torque on arm 19. The clamped arm end may also slip on sleeve 21. <IMAGE>

Description

Gate Operating Mechanism This invention relates to mechanisms for operating gates, especially gates which swing about an axis of rotation, including turnstiles. The term "gate is to be understood as including doors, and a wide variety of types of gate may be operated by means of the invention.

Knawn gate operating mechanisms include a motor and an output drive means, the latter being operatively attached to the gate. In the event of a breakdown or power failure, therefore, the mechanism can be detached from the gate only by partial disassembly.

Furthermore, a high degree of precision during installation is required, to ensure correct alignment of moving parts and thus smooth operation throughout the range of movement. In particular, it is often necesbary to mount the motor so that its output shaft is mounted coaxially with the axis of rotation of the gate.

It is an object of the present invention to provide a gate operating mechanism which can readily be disconnected from the gate and which may be installed with a wide degree of tolerance.

According to the invention., a gate operating mechanism includes a motor having an output drive shaft and an operating arm operatively connected thereto, the operating arm and gate being linked by means of an element which is movable between gate/arm engagement and disengagement positions.

Preferably, the element is carried by the operating arm and the gate carries a housing for receiving the element in the engagement position. The housing may comprise an elongate channel or slot whereby the element can slide in relation thereto when in the engagement position, thus permitting relative sliding motion between the element and the gate on operation of the mechanism and enabling the rotational axis of the operating arm to be spaced from that of the gate. The element may comprise a cylinder which is pivotably mounted at or towards the end of the operating arm remote from the motor, for pivotal movement between a substantially upright or vertically-oriented engagement position and a substantially horizontally-oriented disengagement position.The element is preferably a relatively loose fit in the housing, to accommodate slight misalignment during installation, for example, with lateral clearance of up to about lmm, and furthermore preferably has vertical clearance within the housing, of about lmm or more. The element may be retained in the selected engagement or disengagement position by means of a biassing pressure acting on a selected part or face thereof, the element being pivotal between the said positions against the biassing pressure by causing retraction thereof and presenting a camming profile thereto such that on pivoting from one position to the other the element passes through a medial position of maximum retraction following which it is biassed to the said other position.The element may be provided with a drive head coaxial with its pivot axis by means of which and with the aid of a lever the element may be pivotted from one position to the other.

Preferably the operating arm is connected to the drive shaft via an adjustable clamp. The clamp may be tightened to a predetermined tightness so that it acts as a slip means to protect the motor in the event of the gate being physically prevented from moving or to provide means for moving the gate manually in the event of a motor failure, without or before moving the element from the engagement to the disengagement position to disconnect the drive. More preferably, the drive shaft and operating arm are connected via a releasable coupling to provide additional or alternative slip means. The releasable coupling may be adjustable so that the parts thereof become disengaged in the release position, thus disconnecting the drive between the motor and gate, at a predetermined torque.

One advantage of the adjustable clamp on the drive shaft connection of the operating arm is that, in installation of a gate operating mechanism which includes such a feature, there is no need for accurate setting of limit switches on the motcr. In contrast, the installation can be made with one limit switch pre-set and the operating arm is then connected to the drive shaft with the gate in the appropriate fully open or fully closed position; the clamp is then tightened to the specified tightness and the limit switch is then automatically set to this gate position thereafter.

Furthermore, if the releasable coupling becomes disengaged, such that the drive shaft becomes positioned out of registration with the operating arm, the correct registration will automatically be assumed on re-engagement of the releasable coupling following removal of the cause of disengagement.

Preferably, limit switches are activated by cam means carried by the output drive shaft, although alternatively servo control and/or speed control may be provided by Hall-effect sensors, optical sensors, tacho generators and the like attached to the drive or other shaft.

The releasable coupling preferably comprises a sleeve member which is rotatable about the drive shaft and to which the operating arm is clamped, and biassed connection means whereby, under the biassing pressure, the sleeve member is constrained to rotate with the drive shaft but may be released therefrom on application of a differential torque to overcome the effect of the biassing pressure.The ends of the drive shaft and sleeve member may be substantially co-planar and the connection means may comprise a circular or annular plate urged into contact with the said ends to transmit turning force from the drive shaft to the sleeve member, preferably via one or more projections on either the plate or the drive shaft and sleeve member ends, and which engage with corresponding recesses in the other part or parts such that the projections can ride out of engagement on application of sufficient differential torque. Preferably two projections/recesses are provided, disposed at angular separations between their centres of 1800, to equilibrate transmissions of turning force while maximising disengaged angular movement. The biassing force may be provided by a spring, preferably a disc spring for reliability and economy of space.

The motor may be connected to the output drive shaft via a gear train and clutch means which is preferably adjustable to suit the particular gate application.

The gear train preferably comprises a worm gear on the primary motor shaft which drives a worm wheel to give an initial reduction ratio of between 20:1 and 60:1.

The clutch pressure plate may be constituted by a further gear a face of which is biassed into contact with the face of the worm wheel and the further gear may drive a main rotary gear wheel which transmits drive to the output drive shafts via planetary gears.

The purpose of the clutch is to provide protection to the motor in the event of a seizure of the gate mechanism which is not accommodated by either the adjustable clamp on the operating arm or the releasable coupling. However, manual over-riding of the mechanism would be accomodated either by the adjustable clamp or releasable coupling, if the operating arm was not disconnected from the gate, since the overall gearing ratio between the clutch and the output drive shaft would in most cases not permit any manual movement at the output shaft being accommodated at the clutch; physical failure of a mechanical component would more probably result.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a side elevation, partly in cross-section, of a gate operating mechanism according to the invention, and Figure 2 is a side elevation, partly in cross-section, on a larger scale than Figure 1, of the gear train of the Figure 1 mechanism.

Referring firstly to Figure 1, a gate operating mechanism is contained within a box housing 11 of steel, which can be embedded in the ground, closed by a cover 12 of diecast aluminium, secured by bolts 13 and a resilient seal 14. A motor 15 drives an output drive shaft 16 via a clutch and gear train arrangement contained in gearbox 17 (see Figure 2). The shaft rotates within seal 18 and drives an operating arm 19 and thence a gate 20 (part of bottom rail only shown).

Rotatably mounted about the shaft 16 is a sleeve member 21, around which is clamped the boss of the gate operating arm 19. The tightness of the clamp is determined according to the torque to which clamp bolt 22 is set, so that the arm under normal operating conditions will move with the sleeve member 21 but will slip around the sleeve member under conditions imposing a differential force greater than a predetermined torque. Drive is transmitted from the drive shaft 16 to the sleeve member 21 by a releasable coupling comprising an annular plate 23 having a D-section or wedge-section transverse projection 24 which is biassed into engagement with a V-shaped groove formed in the upper end of the drive shaft 16 and with a corresponding groove formed across the sleeve member 21. In the drawing, the grooves are in alignment and form a common groove indicated as 25.Drive is therefore transmitted while the plate 23 is in the engagement position with both drive shaft and sleeve member grooves but can be interrupted by the transverse projection being forced out of engagement against the bias force by a differential torque greater than a predetermined value, according to the pressure exerted by the biassing force. Preferably the biassing force is provided by a spring 26, preferably a disc spring the pressure of which is adjusted by nut 27 and locked by cotter pin 28, the nut 27 being screw-threadedly engaged with screw-threaded mandrel 29 locked in position coaxially with and upstanding from the drive shaft 16. The assembly of parts 16, 18, and 21-29 is protected by a domed plastics cover 30.

The distal end, with respect to the boss, of the gate operating arm 19 is bifurcated and has pivotally attached between the bifurcated arms thereof a cylinder 31; the cylinder is pivotal between an upright position, as shown in solid outline, and a horizontal position, as shown in dashed outline. The cylinder is fixed to pin 32 which is journalled between the arms and is provided with a triangular end formation whereby the pin can be turned between the said positions by means of a key having a correspondingly-shaped head. A helical compression spring 33 is carried within an axial bore formed in the web between the bifurcated arms and bears on either the side or the end of the cylinder via plunger 34.The corner 35 of the cylinder therefore acts as a camming surface to cause retraction of the spring on pivoting from one position to the other, whereby the cylinder is biassed to one or other of the positions depending on the location of the apex of the corner with respect to the spring.

When in the upright position, the cylinder engages in a channel member 36 located in the lower edge of the gate 20, the cylinder having a lateral clearance within the channel of approximately lmm. Furthermore, there should be a clearance of approximately lmm between the top of the cylinder and the top of the channel. The cylinder in this position pushes on a wall of the channel member with the ability to slide therein if necessary to accommodate relative motion longitudinally of the operating arm in the event that the rotational axis of the output drive shaft is not in alignment with that of the gate. It is to be understood that the gate 20 and channel member 36 are shown at 900 to the position they would assume in practice; this is to show the relationship between the ' channel member and cylinder 31 in the engaged position.Pivoting to the position shown by the dashed line would therefore take place within and longitudinally of the channel member.

Referring to Figure 2, the motor is indicated 15 and the output drive shaft 16, the top of which is formed with a V-shaped groove 25, as in Figure 1. The motor drives a worm gear which meshes with a worm wheel 40 mounted on rotatable shaft 41. A friction pad 42 is secured to the upper surface of the worm wheel and a gear wheel 43 is mounted for free rotation around the shaft 41, the lower part of the gear wheel 43 having an annular flange 44 which is urged into contact with the friction pad 42 by disc spring 45. The pressure exerted by the disc spring is adjustable via a screw 46 acting on pin 47 carried within a slot in the shaft 41, the desired pressure being set by locknut 48.

The gear wheel 43 meshes with a main rotary gear 49 which in turn drives three planetary gear wheels 50 which rotate around a central fixed cog 51. The planetary gears are carried by shafts 52 which also carry upper planetary gears 53 which mesh with and drive the output drive shaft via gear teeth 54.

The use of a rotary gear gives improved gear engagement and torque transmission and allows flexible change of gear ratio to suit particular operating requirements.

Furthermore, the use of a worm gear in combination with the planetary gears gives a wide range of gear ratios.

Claims

1. A gate operating mechanism including a motor having an output drive shaft and an operating arm operatively connected thereto, in which the operating arm and gate are linked by means of an element which is movable between gate/arm engagement and disengagement positions.

2. A mechanism according to Claim 1, in which the element is carried by the operating arm and the gate carries a housing for receiving the element in the engagement position.

3. A mechanism according to Claim 2, in which the housing comprises an elongate channel or slot.

4. A mechanism according to any preceding claim, in which the element comprises a cylinder which is pivotably mounted at or towards the end of the operating arm remote from the motor for movement between a substantially upright or vertically-oriented engagement position and a substantially horizontally-oriented disengagement position.

5. A mechanism according to any of Claims 2 to 4, in which the element is a relatively loose fit in the housing.

6. A mechanism according to Claim 4, in which the cylinder is retained in the engagement and disengagement positions by a spring which exerts a biassing pressure on a respective face of the cylinder in each position, the cylinder having a camming profile between the said faces so that, as the cylinder is v pivoted from one position to the other, it passes through a medial position in which the profile causes the retraction or compression of the spring, following which the spring biasses the cylinder to the said other position.

7. A mechanism according to any preceding claim, in which the operating arm is connected to the motor output drive shaft via an adjustable clamp which acts as slip means.

8. A mechanism according to any preceding claim, in which the operating arm and motor output drive shaft are connected together via a releasable coupling.

9. A mechanism according to Claim 8, in which the releasable coupling comprises a sleeve member which is rotatable about the drive shaft and to which the operating arm is clamped, and biassed connection means, whereby the sleeve member is constrained to rotate with the drive shaft but is releasable therefrom on application of a differential torque to overcome the biassing pressure.

10. A mechanism according to Claim 9, in which the ends of the drive shaft and sleeve member are substantially co-planar and the connection means include a plate urged into contact with the said ends to transmit turning force from the drive shaft to the sleeve member via a projection on the plate which engages a common groove in the said ends, such that the projection is disengageable from the groove against the biassing pressure on application of sufficient differential torque.

11. A mechanism according to any preceding claim, in which the motor is connected to the output drive shaft via a gear train and adjustable clutch means, the gear train comprising a worm gear on the primary motor shaft which drives a worm wheel to give an initial reduction ratio of between 20:1 and 60:1.

12. A mechanism according to Claim 10, in which the pressure plate of the clutch means is constituted by a further gear a face of which is biassed into contact with the face of the worm wheel, the further gear driving a main rotary gear wheel which transmits drive to the output drive shaft.

13. A gate operating mechanism substantially as herein described with reference to, and as shown in, the accompanying drawings.