GB2179795A

GB2179795A - Speed-responsive shutdown device

Info

Publication number: GB2179795A
Application number: GB08612516A
Authority: GB
Inventors: Anton Niederberger; Christian Mathys; Hans Kocher
Original assignee: Inventio AG
Current assignee: Inventio AG
Priority date: 1985-08-29
Filing date: 1986-05-22
Publication date: 1987-03-11
Also published as: FR2586664B1; NL193279B; JPH0339951B2; SE468432B; DK162211B; GB8612516D0; ES2000722A6; HUT45219A; DK403986D0; NO163766B; IT8621501A0; HU198651B; PT82764B; FI80661B; FI863292A; FR2586664A1; DE3615270A1; BE905003A; SE8603635D0; NO863452L

Abstract

The speed of travel of a lift cage is monitored by a shutdown device, comprising a cable-driven pulley with integrated ratchet wheel (4) and cam wheel. The cam wheel sets a rocker (5) with a rocker lug (5.21) into rocking movement. Rotatably mounted on the rocker (5) is an actuating lever (6.2) held in a rest position relative to the rocker by a restraining device (8) which may be a restoring spring, spring detent or a magnet. The upper end of the lever (6.2) is constructed as an actuating bracket (6.21) and its lower end as a tripping lug (6.22) projecting further than the rocker lug. Both lugs lie between two adjacent ratchet wheel teeth (4.1), when the roller (5.11) of the rocker stands on a cam lobe (3.1). When the roller (5.11) is between two cam lobes, the lugs are lifted out of the path of the teeth (4.1) and the teeth move past the lugs without effect. In the case of excess speed, the roller (5.11) lifts off the cam wheel (3). The tripping lug remains in the path of the ratchet wheel teeth. The next arriving tooth engages the tripping lug and deflects the lever (6.2), whereby the bracket (6.21) switches off the drive by way of a switch (9.1). On further rise in the speed, the rocker lug (5.21) enters the path of the ratchet wheel teeth (4.1) and leads to blocking of the cable pulley. <IMAGE>

Description

SPECIFICATION Speed-responsive shutdown device The present invention relates to a speed-responsive shutdown device, especially for a lift drive.

Lifts must be equipped with an arresting device which is tripped at least during downward travel by a speed limiter when the normal travel speed is exceeded by a predetermined value. When the arresting device is tripped, the cage is stopped with high negative acceleration, which is unpleasant for the passengers and moreover requires appreciable work to restore the operational readiness of the lift. It is therefore advantageous, in the case of low excess speeds of the lift cage, to slow down the travel of the lift cage up to standstill through switching-off the drive and tripping the brake. If the cage speed rises further in spite of switching-off of the drive, then the speed limiter trips the arresting device. As a result, the cage is held in the guide rails.

For switching-off of the drive in the case of excess speed of the lift cage and for the tripping of the arresting device on further rise in speed, ratchet wheel speed limiters are frequently used. They are simple in construction, cheap to manufacture and because of their simplicity have few faults.

Such cam wheel speed limiters operate with a double-armed rocker which is rotatably mounted on a frame and set into rocking motions by a rocker roller. That end of the rocker which is opposite to the roller is constructed as a dog which, in the case of excess speed, engages into the path of the ratchet wheel. For the preliminary switchingoff of the drive, equipment actuating a switch is mounted on the lever.

Equipment of that kind is disclosed in CH-PS 387 902. One form of equipment for preliminary switching-off consists of a compression spring, an inertia body and a switch fastened to the frame. An inertia force produced by the rocker movement acts with continuously changing magnitude and direction on the inertia body. The dimensions of the compression spring and of the inertia body are chosen so that, when a certain lift speed is exceeded, the inertia force acting on the inertia body is greater than the sum of the body weight and the compression spring force. The force component resulting therefrom displaces the inertia body upwardly out of the rest position, which by way of a pin actuates the switch fastened to the frame.In another form, the equipment for preliminary switching-off consists of a tension spring, an inertia body and a contact at the rocker, and, in a third form of a compression spring, a magnet and a contact at the rocker. All three forms of construction have the same mode of operation in principle. They operate as described above with a movable inertia body on which acts a force resulting from an inertia force, inertia body weight and spring force so as to displace the inertia body out of its rest position in the case of excess speed of the lift.

A disadvantage of this known equipment resides in the high mechanical complexity and the manufacturing costs connected therewith.

A further disadvantage is the effort involved in setting-up and maintenance operations. The tripping point for the electrical and mechanical switching must be set individually and is not entirely simple, due to mutual influencing. An alteration or adaptation of the nominal lift speed also requires a two-fold adjustment of the tripping points, wherein the setting of the electrical switching-off depends not only on the newly chosen nominal lift speed, but also on the setting of the mechanical switching.

Equipment for the preliminary switching-off, disclosed in DE-GM 7238999.2, is mechanically separated from the rocker. Thereby, the tripping points can be set separately and independently. Apart from the simplified setting operations, this equipment for preliminary switchingoff has the same disadvantages as those according to CH-PS 387 902.

The main disadvantage in both forms of equipment lies in the tripping directly through inertia force of moved masses. If the frictional forces of the moved parts increase, then the inertia force is no longer sufficient for secure tripping. A further factor is the wear of the constantly moving parts. High mechanical, setting and maintenance work, increased susceptibility to faults and correspondingly reduced reliability can be disadvantages of the known equipment for preliminary switching-off.

It would thus be desirable to provide preliminary switching-off of, for example, the drive of a lift installation at a predetermined excess speed by means of equipment which has a simple mechanical construction and low susceptibility to faults and which only requires a relatively simple setting.

According to the present invention there is provided a speed-responsive shutdown device comprising a rotatable toothed ratchet wheel, a cam-driven rocker provided on one arm thereof with a dog co-operable with the ratchet wheel teeth when the wheel exceeds a first predetermined rotational speed, an actuating lever mounted on said one arm of the rocker to be pivotable relative thereto between a rest position and an actuating position, restraining means acting between the rocker and the lever to exert a restraining force resisting movement of the lever out of the rest position, and shutdown switching means actuable by the lever in the actuating position, the lever being provided with a lug which in the rest position of the lever projects further towards the path of movement of the ratchet wheel teeth than the rocker dog and which is so cooperable with the teeth when the wheel exceeds a second predetermined speed lower than the first speed as to cause the lever to be pivoted into the actuating position against the restraining force.

In a preferred embodiment the device comprises a cam wheel speed limiter, which includes a switch fastened to a frame of the speed limiter and actuable to stop an associated drive. Actuating equipment, which is arranged on the rocker, actuates the switch when the normal speed of travel of the lift is exceeded and at a predetermined lift travel speed lying below the tripping speed of the speed limiter. When the drive is for a lift, the lift cage drives a cable pulley with integrated ratchet wheel by way of a wire cable. A rocker roller transmits the cam movement to a double-armed rocker. The rocker end opposite the roller is constructed as a dog. Sitting on this rocker end is the actuating equipment with a double-armed actuating lever which is rotatably mounted on the rocker lever and fixed by a holding-back device.

In a device embodying the invention, the force for tripping of the equipment for the preliminary switching-off is exerted directed by the ratchet wheel, the actuating equipment has no sliding parts, the construction of the preliminary switching-off mechanism is relatively simple and thereby contributes to reduction in manufacturing costs, setting of the tripping speed of the preliminary switching-off is no longer necessary and thereby a source of faults is excluded and the functional reliability is increased correspondingly, and that due to the simple mechanical construction fewer parts are exposed to the wear, whereby susceptibility to faults is significantly reduced.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a schematic elevation of a first device embodying the invention; Fig. 2 is a plan view of the device of Fig. 1; Fig. 3 is an enlarged scale elevation of the device of Fig. 1, showing restraining means consisting of a spring and ball catch; Fig. 4 is a view similar to Fig. 3, but of a second device embodying the invention; and Fig. 5 is a plan view of part of the device of Fig. 4.

Referring now to the drawings, there is shown a shutdown device comprising a frame 1 carrying an axle 1.1 on which are rotatably mounted a cable pulley 2 provided with a cable groove 2.1, a cam wheel 3 with a cam 3.1 and a ratchet wheel 4 with ratchet wheel teeth 4.1 provided with notches 4.11, the pulley and wheels being fastened to each other.

Pivotably mounted on a further axle 1.2 at the frame 1 is a double-armed rocker 5, at one arm 5.1 of which is mounted a rotatable roller 5.11 and the other arm 5.2 of which has a rocker lug 5.21 and carries actuating equipment 6. Designated by 7 is a holding-back spring which at one end is fastened to the frame 1 and at the other end to the rocker arm 5.1 and draws the roller 5 onto the surface of the cam wheel 3. Setting of the tension of the spring 7 takes place by way of an adjusting device 7.1 mounted at the frame 1.

The actuating equipment 6 consists of a double-armed actuating lever 6.2, which is rotatably mounted on an axle 6.1 and has a Vshaped actuating bracket 6.21 at the upper end and a tripping lug 6.22 at the lower end.

Arranged between the lever 6.2 and the rocker 5 is a restraining device 8 which in a first embodiment consists of a spring and ball detent catch. In a further embodiment, the device 8 consists of a restoring spring 8.1, which is held by aspring fastening 8.1.1 and a fastening screw 8.1.2 and which together with an abutment 8.2 is mounted on the rocker 5. An actuating setting of the spring 8.1 is designated by 8.3.

Fastened to the frame 1 is a switching-off device 9 having a switch 9.1 with switch head 9.11. The switch head 9.11 is co-operable with the bracket 6.21, as subsequently described.

The afore-described device operates as follows: A lift cage drives the cable pulley 2 with integrated ratchet wheel 4 and cam wheel 3 in known manner by way of a wire cable. The roller 5. 11 follows the path of the cam wheel 3. The spring 7 is so set that the roller 5.11 follows the cam 3.1 of the cam wheel 3 up to the nominal lift speed. The rocker 5 is set by way of the cam 3.1 and roller 5.11 into rocking movement, whereby the lug 5.21 moves into and out of the gaps between the teeth 4.1. When the lift speed exceeds a certain tripping value preset by the spring 7, then the roller 5. 11 lifts off the cam wheel 3. The inertia moment of the rocker 5 becomes greater than the restoring moment of the spring 7. The rocker lug 5.21 remains in the path of the teeth of the ratchet wheel 4, which leads to blocking of the cable pulley 2.

The force for the engagement of the device is created by the friction in the cable groove 2.1.

The actuating equipment 6 serves for preliminary switching-off of the lift drive. The device 8 holds the actuating equipment in a rest position relative to the rocker 5. The lug 6.22 in the rest position lies more closely at the path or enters more deeply into the path of the ratchet wheel 4 than the lug 5.21. 8oth lugs in this embodiment always lie between two ratchet wheel teeth 4.1 when the roller 5.11 stands on a lobe of the cam 3.1. When the roller 5.11 is in a cam valley, the two lugs are lifted by way of the rocker 5 out of the path of the ratchet wheel teeth 4.1. Thereby, the teeth 4. 1 move past the lugs without effect. In the case of excess speed, as already described, the roller 5.11 lifts off the cam wheel 3.One of the ratchet wheel teeth 4.1 engages the tripping lug 6.22 and brings the actuating equipment 6 into an actuating position. In the rest position of the lever 6.2, the bracket 6.21 does not touch the switch head 9.11, the bracket 6.21 pushing over the switch head 9.11 only in the actuating position and thereby changing the switching state of the switch 9.1. During the movement of the rocker 5, no risk of actuation exists in the rest position of the lever 6.2. In the first embodiment, the lever 6.2 must be turned back to the rest position for restoration of operation after a deflection. In the second embodiment, the device 8 resets the deflected lever 6.2 back automatically into the rest position.

In the case of excess speed of the lift cage in upward direction, the tripping lug 6.22 engages into the notch 4.11 of the ratchet wheel teeth 4.1. Due to the ieftward rotation of the ratchet wheel 4, the lever 6.2 with the bracket 6.21 is pivoted in clockwise sense and the drive is thereby stopped by way of the switch head 9.11 and the switch 9.1.

In the first embodiment, the device 8 can be a commercially available spring and ball catch. Thus, a spring guide let into the rocker 5 houses a spring which presses a ball against the lever 6.2. The ball diameter is smaller than the diameter of the guide. At the side of the lever 6.2, the guide is closed by a ring having an internal diameter so dimensioned that the ball cannot pass through the ring. At most, the ball can project out of the guide by about half the ball diameter. In the actuated setting of the equipment 6, the lever 6.2 presses the ball into the guide. A bore with a diameter which is smaller than the ball diameter lies adjacent to the ball in the rest setting of the equipment 6. In the rest setting, the ball is pushed into the bore by the spring force until the diameter of the entering ball portion is equal to the diameter of the bore.

The ball thus acts as a detent between the rocker 5 and the lever 6.2. On deflection of the lever 6.2, the bore moves away from the ball and the ball comes out of the bore and is pressed by the lever 6.2 into the guide.

In place of a spring and ball catch, a small magnet could be mounted on the rocker 5. A countermagnet would then be mounted on the lever 6.2 at the place of a bore.

As illustrated in the Figs. 4 and 5 in the second embodiment, in place of a spring and ball catch the equipment 8 is constructed to be able to automatically reset the lever 6.2.

The equipment 8 comprises a U-shaped restoring spring 8.1 which is biassed by way of the abutment 8.2 and holds the lever 6.2 in the rest position by limb ends engaging on either side of the bracket 6.21. In the case of excess speed of the lift cage in downward direction, the lever 6.2 with the bracket 6.21 is pivoted in counterclockwise sense. In that case, one limb of the restoring spring 8.1 is entrained by the bracket 6.21 and deflected against a spring force into the actuating setting 8.3. When, on restoration of the shutdown device to operational condition, the ratchet wheel teeth 4.1 no longer engage the lug 6.22, the spring 8.1, which in the actuating setting 8.3 stores a spring energy, resets the lever 6.2 to the rest position. In the case of excess speed of the lift cage in upward direction, the deflection of the other limb of the restoring spring 8.1 and the resetting of the actuating equipment 6 take place in analogous manner.

Claims

1. A speed-responsive shutdown device comprising a rotatable toothed ratchet wheel, a cam-driven rocker provided on one arm thereof with a dog co-operable with the ratchet wheel teeth when the wheel exceeds a first predetermined rotational speed, an actuating lever mounted on said one arm of the rocker to be pivotable relative thereto between a rest position and an actuating position, restraining means acting between the rocker and the lever to exert a restraining force resisting movement of the lever out of the rest position, and shutdown switching means actuable by the lever in the actuating position, the lever being provided with a lug which in the rest position of the lever projects further towards the path of movement of the ratchet wheel teeth than the rocker dog and which is so co-operable with the teeth when the wheel exceeds a second predetermined speed lower than the first speed as to cause the lever to be pivoted into the actuating position against the restraining force.

2. A device as claimed in claim 1, the restraining means comprising a spring detent.

3. A device as claimed in claim 1, the restraining means comprising a magnetic means.

4. A device as claimed in claim 1, the restraining means comprising a U-shaped restoring spring which is carried by the rocker and biassed by an abutment, the spring being arranged to hold the lever in the rest position and to be able to pivot the lever from the actuating position back to the rest position.

5. A speed-responsive shutdown device substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings.

6. A speed-responsive shutdown device substantially as hereinbefore described with reference to Figs. 4 and 5 of the accompanying drawings.

7. A lift drive comprising drive means and a device as claimed in any one of the preceding claims to provide safety shutdown of the drive means.