GB2225308A - Arrangement for raising and lowering a load - Google Patents

Abstract

Apparatus for raising and lowering a load which is suspended from a rope or ropes (3) has a sensor (20) which, in response to slackness in the rope(s), engages a locking device (26) to prevent further movement of the rope(s). The rope passes between two rollers (21), (22) and over a roller (23) mounted on a pivoted arm (24) whose movement operates the locking device. The load may be in a theatre or studio, eg lighting scenery or loudspeakers. <IMAGE>

Description

ARRANGEMENT FOR RAISING AND LOWERING A LOAD The present invention relates to an arrangement for raising and lowering a load.

The invention is concerned, more especially, with hoist systems used predominantly in theatres and television studios for raising and lowering equipment such as lights, scenery, monitors and loudspeakers.

Known hoist systems for use in theatres or studios include a body from which a load, for example a light, is suspended by at least one rope. The body houses a rope winding drum by means of which the rope can be taken up, or fed out as required to raise or lower the load. The rope may be guided through a telescopic arm that extends downwards from the housing, the hoist then being known as a "monopole" or "telescope". Problems can arise if the load does not descend freely, for example because it encounters an obstacle, and the present invention is concerned with enabling such problems to be avoided.

The present invention provides an arrangement for raising and lowering a load, comprising means for suspending the load from at least one rope; a rope winding drum which is rotatable to raise and lower the said means, and a sensor arrangement operable, in response to slackness in the rope(s), to engage a locking member in the drum and prevent further rotation of the drum.

The locking member may be engageable in a recess in the periphery of the drum, the recess being so shaped that the drum is then locked against rotation in a direction corresponding to a lowering of the suspension means but is not locked against rotation in the reverse direction.

The sensor arrangement may comprise at least one sensor member over which rope from the drum passes and which, when the rope is taut, is held by the rope in a first position in which the locking member is held out of engagement with the drum. The sensor member may be resiliently-biased towards a second position in which the locking member engages the drum.

The arrangement may include drive means operable to rotate the drum.

Advantageously, the arrany-ement includes means operable to prevent further rotation of the drum to lower the said suspension means when only a predetermined amount of rope remains on the drum.

The drum may be located within a wheeled housing.

Rope from the drum may be guided within an arm which is arranged to telescope as the suspension means is raised or lowered.

By way of example, a studio/theatre lighting monopole constructed in accordance with the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a view of the whole monopole; Fig. 2 is a view in the direction of the arrow II in Fig. 1, but showing only the upper part of the monopole; Fig. 3 is a view in the same direction as Fig.

1, but partly in section on the line III-III of Fig. 2 and with part broken away; Fig. 4 is a view in the direction of the arrow IV of Fig. 3, partly broken away, and Fig. 5 is a scrap view showing an alternative position of certain components of Fig. 3.

The lighting monopole (or telescope) shown in the drawings is intended for use in a television studio or a theatre as, or as part of, a hoist system for raising and lowering a light. The monopole comprises a body 1 housing a rotatable drum 2 on which are wound wire suspension ropes 3. The ropes 3 run, from the drum, through a telescopic arm 4 that extends downwards from the body 1. A studio/theatre light (not shown) is suspended in any suitable manner at the lower end of the ropes 3.

The body 1 has wheels 5 on each side, which run on overhead rails (not shown) although this is not essential. By moving the body 1 along the rails (when provided) and rotating the drum 2 to raise or lower the light, the latter can be brought into a desired position. As the light is raised or lowered the length of the telescopic arm 4 will also alter. The arm 4 is formed from several tubes 6 (Fig. 2) of square crosssection, telescoped one inside another with the outermost tube secured to the body 1, and serves to provide a degree of stability to the suspended light.

The drum 2 is rotated by a worm wheel 8, mounted adjacent the drum, which is engaged by a vertical drive worm 7 located to one side of the body 1. Rotation of the worm 7 causes the wheel 8 to turn and rotate the drum 2. The worm 7 is provided with a brake 9 which, in the engaged position (shown in Fig. 3), ensures that the worm 7 does not rotate. The brake 9 comprises a brake pad 10 mounted on a plate 11 which is pivoted at one side and, at the other side, is attached to one end of a spring 12. The spring 12 pulls the plate 11 towards the "brake on" position in which, as shown in Fig. 3, the brake pad 10 engages a disc 13 at the end of the worm 7.

The brake 9 is released by actuating a striker rod 14 which passes centrally through the worm 7. When the striker rod is depressed, it pushes the brake pad 10 with its support plate 11 away from the disc 13 against the action of the spring 12 and allows the worm to rotate. The "brake off" position is shown in Fig. 5.

Actuation of the striker rod 14 and rotation of the worm 7 are effected by locating a square-section drive member 15 in a correspondingly-shaped recess 16 in the upper end of the worm. This depresses the striker rod 14 to release the brake and also connects the worm 7, through the drive member 15, to a suitable drive motor which, when operated, rotates the worm 7 to raise or lower the light at the end of the ropes 3.

The drive may, for example, be taken from a conventional hand held electric or pneumatic drill fitted with a slipping clutch (see below), which is carried to the location by the operator. When the light reaches the desired position, the drive to the worm 7 is discontinued and the latter ceases to rotate.

Removal of the drive member 15 from the recess 16 results in the brake 9 being applied to ensure that further rotation of the worm 7 does not occur.

To ensure that the drum 2 is brought to a halt before the ropes 3 are completely unwound, the drum carries a lever 17 which is normally held in the solidline position shown in Fig. 3 by the ropes 3. When the ropes 3 are almost all unwound, the lever 17 is able to move under the action of a spring (not shown) into the broken-line position shown in Fig. 3, in which position the lever engages a stop on the drum casing and prevents further rotation of the drum.

The monopole also incorporates a slack rope sensor indicated generally at 20. The sensor 20 is located in the region of the junction between the body 1 and the arm 4 and includes two rollers 21, 22 between which the ropes 3 pass as they leave the drum 2. A further roller 23 is mounted between the ends of a pair of arms 24 which are pivotally mounted on the axle of the roller 21 and, as long as the ropes 3 are taut, the roller 23 is held by the ropes in the position shown in dotted lines in Fig. 3. A link 25 is mounted at one end on the axle of the further roller 23 and, at the other end, is pivotally coupled to a stop member 26 which is rotatably mounted in the monopole body 1. One arm of a torque spring 27 acts at the pivotal coupling between the link 25 and the stop member 26 to urge the latter into the position shown in solid lines in Fig.

3.

The slack rope sensor operates as follows. When the light is being lowered, the ropes 3 should be taut and, as mentioned above, will then hold the roller 23 and arms 24 in the dotted-line position shown in Fig.

3. In this position, the arms 24 hold the link 25 down against the action of the torque spring 27 and the stop member 26 is rotated into the dotted line position shown in Fig. 3. In this position, the stop member is clear of the rotating drum 2. If, however, the ropes 3 go slack for some reason (for example because the telescoped sections 6 of the arm have become jammed or because the light has encountered an obstacle) then the roller 23, arms 24, link 25 and stop member 26 will no longer be held down in the dotted line position but will move under the action of the spring 27 towards the position shown in solid lines. The end of the stop member 26 contacts the periphery of the drum and, as the drum continues to rotate, engages in one of a plurality of indents 28 that are formed in the periphery of the drum and brings the drum to a halt.

At this stage, the rotary drive member is still engaged in the recess of the screw and, when the drum 5 becomes locked against rotation, the clutch of the drive tool will begin to slip. To clear the slack rope condition, the drum 2 is rotated in the reverse direction to wind in the ropes 3 (this rotation being permitted by the shape of the indents 28 which allows the stop member 26 to ratchet over the surface of the drum). When the slack rope has been taken up, the roller 23 is pushed down again and moves the stop member 26 clear of the drum whereupon the drum can be reversed again and a further attempt can be made to lower the lamp.

In certain circumstances, it may be desirable to provide a respective roller 23 for each of the ropes 3 so that the drum 2 will be brought to a halt in the event of one of the ropes going slack (for example, because it breaks) while the other rope remains taut.

It will be appreciated that the slack rope sensor 20 is not dependent on the nature of the drive arrangement 7 etc. provided for the drum 2 and that an alternative form of drive arrangement could be used.

Likewise, the lever 17 etc. could be replaced by any other suitable arrangement for ensuring that the drum is brought to a halt before the ropes 3 are completely unwound. It will also be appreciated that the telescopic arm 4, although it provides stability to the suspended lamp, is not essential to the operation of the basic hoist system comprising the rope winding drum 2 and the slack rope sensor 20.

Although the monopole has been described as being used for raising and lowering a light in a theatre or television studio, it could be used for raising and lowering other loads, for example scenery or a monitor or a loudspeaker. Moreover, although this particular type of hoist with its telescopic arm 4 (i.e. a monopole) is used predominantly in television studios and theatres, the basic hoist system comprising the rope winding drum 2 and the slack rope sensor 20 could be used in other locations.

Claims (9)

Claims

1. An arrangement for raising and lowering a load, comprising means for suspending the load from at least one rope, a rope winding drum which is rotatable to raise or lower the said suspension means, and a sensor arrangement operable, in response to slackness in the rope(s), to engage a locking member in the drum and prevent further rotation of the drum.

2. An arrangement as claimed in claim 1, in which the locking member is engageable in a recess in the periphery of the drum, the recess being so shaped that the drum is then locked against rotation in a direction corresponding to a lowering of the suspension means but is not locked against rotation in the reverse direction.

3. An arrangement as claimed in claim 1 or claim 2, in which the sensor arrangement comprises at least one sensor member over which rope from the drum passes and which, when the rope is taut, is held by the rope in a first position in which the locking member is held out of engagement with the drum.

4. An arrangement as claimed in claim 3, in which the sensor member is resiliently-biased towards a second position in which the locking member engages the drum.

5. An arrangement as claimed in any one of the preceding claims, including drive means operable to rotate the drum.

6. An arrangement as claimed in any one of the preceding claims, including means operable to prevent further rotation of the drum to lower the said suspension means when only a predetermined amount of rope remains on the drum.

7. An arrangement as claimed in any one of the preceding claims, in which the drum is located within a wheeled housing.

8. An arrangement as claimed in any one of the preceding claims, in which rope from the drum is guided within an arm which is arranged to telescope as the suspension means is raised or lowered.

9. An arrangement for raising and lowering a load, substantially as described herein with reference to the accompanying drawings.