The apparatus for moving a load includes a carrier cable having a first end connected to the load, and a second end connected to a movement device, the movement device including an operating line connected to a movement carriage. An electric motor is configured to move the carriage as a function of a force exerted on the operating line.

The present invention relates to apparatus for moving a load, and more particularly but not exclusively, to apparatus for moving theatre scenery.

BACKGROUND OF THE INVENTION

In order to change the scenery in a theatre, it is common practice to use moving apparatus comprising an operating line having its end fastened to a carriage that is connected to the load by a carrier cable. With theatre scenery, the apparatus has a plurality of carrier cables, each having one end connected to the carriage, with their opposite ends being connected at various points to a beam carrying the scenery. In order to make moving easier, it is known to use counterweights that are fastened to the carriage and that are of weight equal to the weight of the load. That structure makes it easy to move the load manually by means of the operating line. Nevertheless, when it is necessary to change scenery of given weight, for other scenery of weight that is different from that of the preceding scenery, it is necessary to adapt the counterweight correspondingly so that the counterweights and the load have the same weight. That operation is arduous and requires several people to be present.

In order to avoid that drawback, it is known to replace the operating line and its counterweight with an electric motor that is fastened to the floor. Nevertheless, the weight of a piece of theatre scenery can be very high (up to 300 kilograms (kg)), such that replacing counterweights by an electric motor involves using an electric motor of large size, which is generally not compatible with the space available, and which is of high cost.

OBJECT OF THE INVENTION

An object of the invention is to provide apparatus for moving a load that can easily be adapted to variation in the weight of the load, while complying with the space available.

BRIEF SUMMARY OF THE INVENTION

In order to achieve this object, there is provided an apparatus for moving a load relative to a carrier structure, the apparatus comprising a carrier cable having a first end connected to the load, and a second end connected to a movement device. The movement device includes: an electric motor and a carriage that is mounted to move relative to the carrier structure and that is configured to move relative to the carrier structure during rotation of the motor; an operating line having its two ends connected via respective attachment points to the carriage so as to form a loop around two pulleys mounted on the carrier structure; and a control member associated with a member for measuring movement of the attachment point relative to the carriage in order to control rotation of the electric motor as a function of that movement.

In an advantageous version of the invention, the electric motor has an outlet shaft carrying at least one drive sprocket wheel co-operating with at least one roller chain. Also preferably, the apparatus includes deflector sprocket wheels arranged on either side of the drive sprocket wheel in order to press the roller chain against the drive sprocket wheel along a sinuous path.

In a preferred embodiment of the invention, the electric motor is carried by the carriage.

Like the other elements carried by the carriage, the electric motor acts as a counterweight.

Preferably, the apparatus includes an additional counterweight carried by the carriage. For equal performance of the electric motor, this increases the load capacity of the apparatus.

Furthermore, in certain circumstances, in particular in the theatre, it is preferable for the personnel in charge of putting scenery into place to become familiar with the new equipment as quickly as possible. In particular, it is desirable for structure of the apparatus to be as close as possible to the structure of prior apparatus, and for the force to be delivered for moving scenery to be as close as possible to the force that used to be delivered with prior equipment.

In another aspect of the invention, the carriage is movably mounted on reference member including the attachment points, the control member for controlling the electric motor issuing a control signal as a function of the relative position of the carriage and of the reference member.

In a preferred version of the invention, the apparatus includes a resilient member fastened both to the reference member and to the carriage, and configured to return the reference member and the carriage to a neutral position relative to each other in which the control signal is zero.

According to another advantageous aspect of the invention, the apparatus comprises a sensor for detecting the relative position of the reference member and of the carriage, and for causing the electric motor to rotate as a function of the signal delivered by the sensor. Preferably, the sensor is a potentiometer having a slider having a zero point at the middle of the stroke of the slider and delivering opposite voltages on either side of the zero point. Also preferably, the device includes a snap-opening switch that opens when the reference member and the carriage pass through the neutral position.

In another aspect of the invention, the movement measurement member comprises a first angular position sensor associated with one of the two pulleys of the operating line, and a second angular position sensor associated with a return pulley of the carrier cable or with an outlet shaft of the electric motor in order to detect the relative position between the reference member and the carriage.

In another aspect of the invention, the movement measurement member comprises a bidirectional strain gauge extending between an attachment point of the operating line and the carriage.

Advantageously, the movement measurement member comprises two strain gauges, each extending between one of the two attachment points of the operating line and the carriage.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIGS. 1 to 4, the moving apparatus in the first embodiment of the invention comprises a reference member1that comprises a top plate2and a bottom plate3that are connected to each other by tie-rods4.

An operating line11has one end connected to an attachment point2.1of the top plate2and an opposite end connected to an attachment point3.1of the bottom plate3. At both ends of the loop formed in this way, the operating line passes over a pulley15that is carried to rotate freely by cheekplates16having holes17for fastening them to the wall. In a variant, the bottom pulley15need not be fastened to the wall so that the weight of said pulley exerts tension on the operating line11.

The apparatus includes a movement device comprising a carriage5mounted to slide relative to the reference member1by means of tubes6engaged on the tie-rods4. The carriage5also has two plates7fastened to the tubes6on either side of the plate1and two plates8fastened to the tubes6and supporting a counterweight23. The carriage5also has forks9engaged astride on a guide rail10that is fastened to the wall.

Carrier cables18, only one of which is shown in the figures, each have one end connected to a load19, in this example a segment of a carrier beam, and an opposite end attached to a stud20carried by the plate7and passing over a deflector pulley21fastened in conventional manner vertically relative to the load19and over a deflector pulley22carried by an angle bar13. In order to balance loads, the carriage preferably has two studs20, one on each main face of the carriage5.

Furthermore, the movement device includes an electric motor24carried axially by the carriage5(i.e. the electric motor24has a rotor of axis that extends parallel to the sliding direction of the carriage5). The electric motor24is associated with reduction gearing25having an outlet shaft26that extends perpendicularly to the axis of the carriage5and that has each of its ends carrying a respective drive sprocket wheel27having a roller chain28engaged thereover. This serves to balance the forces to which the outlet shaft26is subjected. The roller chain28is held engaged on the drive sprocket wheel27along a sinuous path by means of idler sprocket wheels29. This makes it possible for the force to which the drive sprocket wheel is subjected while it is being rotated by the motor24to be shared over a plurality of teeth.

Threaded rod segments30are fastened to the top end of the roller chain28. The threaded rod segments30pass through the bottom portions of brackets44fastened to the angle bar13. The roller chains28are tensioned by nuts45screwed onto the threaded rod segments30and bearing against the bottom portions of the brackets44. At their bottom ends, the roller chains28are fastened to a plate that is fastened to the floor by using mounting analogous to that used at their top ends. The angle bar13, the plate31, and the roller chains define a carrier structure.

A counterweight23, which adds to the weight of the motor24and of the other elements carried by the carriage5, is fastened to the plate8in order to compensate in part for the weight of the load, e.g. a counterweight of 150 kg for a load of 300 kg. A damper31is fastened to the reference member1and also to the carriage5so as to damp relative movements between the reference member1and the carriage5. A counterweight32for balancing the weight of the reference member is mounted to slide on the body of the damper31and is held suspended by flexible ties33fastened both to the counterweight32and to the plate3, passing over deflector pulleys carried by the carriage5.

The reference member1and the carriage5are returned towards a neutral position by a resilient member, in this example two helical springs35, each carried by cups36engaged in the ends of the springs. Furthermore, the cups36bear against the edge of a window in the plates2, and on the edges of identical windows in the plates34that are secured of the plates7on either side of the plates2so that the springs35are put into compression regardless of the travel direction of the reference member and of the carriage relative to each other.

The device also has an electronic unit associated with a linear potentiometer37fastened to one of the plates34. The potentiometer37has a neutral point at half-stroke and inverting circuits on either side of the neutral point. It has a slider38engaged in an opening39of a plate40fastened to the plate2of the reference member1.

A snap-opening switch41is also mounted on the plate of the carriage5and has a control toggle43of position that is controlled by a fork42carried by the plate2of the reference member1and passing through a slot46in the plate34. The control toggle43is movable between a neutral position in which the switch41is open, and an upwardly or downwardly tilted position in which the switch41is closed.

Starting from the position shown inFIG. 1in which the assembly comprising the carriage and the reference member is in its low position and the load is high, downward traction exerted on the front strand of the operating line11gives rise, as a result of compressing the spring35, to upward movement of the reference member1relative to the carriage5. The relative movement between these two components is measured by the position of the cursor of the potentiometer37, thereby triggering rotation of the electric motor24in the direction for raising the assembly comprising the carriage and the reference member.

In conventional manner, the signal delivered by the potentiometer37may be interpreted as a setpoint for position, for speed, or for acceleration. When moving theatre scenery, the preferred setpoint that is used is an acceleration setpoint since that is a closer match to earlier mechanical devices.

The setpoint for moving continuously exists so long as the user exerts a force on the line that causes the springs to be compressed. The value of the setpoint is proportional to the force exerted.

If the user holds the operating line11stationary, the movement of the carriage5naturally brings the potentiometer37and the switch41back towards the neutral position.

If the user lets go of the operating line11, it is the springs35that act to return the potentiometer37and the switch41towards the neutral position.

The damper31serves to avoid this return movement being too violent and ensures that it takes place without bouncing.

When the neutral position is reached and the carriage5has stopped or is moving at low speed, the electricity is switched off and the brake of the electric motor24is applied.

FIG. 5shows a second embodiment of the invention that, like the above embodiment, relates to apparatus for moving a load relative to a carrier structure. The movement apparatus shown inFIG. 5is similar to that shown inFIGS. 1 to 4with the exception that the reference member in this embodiment is hinged.

The movement apparatus thus has a reference member101having a top plate102and a bottom plate103that are connected together by a single tie-rod104, and each of which is connected to the carriage105via a pivot hinge102.2,103.2so as to form a deformable parallelogram. The top plate102and the bottom plate103are weighted behind their pivot points102.2,102.2in order to balance their weights.

More precisely, an operating line111has one end connected to an attachment point102.1of the top plate102and an opposite end connected to an attachment point103.1of the top plate103. The apparatus includes a movement device comprising the carriage105mounted to slide along the tie-rod104of the reference member by means of a tube106engaged on said tie-rod. The apparatus also has an electric motor124carried by the carriage105and arranged in identical manner to the above-described first embodiment.

A strain gauge150is mounted between the carriage and the tie-rod104in order to measure the rectilinear relative movements between the reference member and the carriage and thus control rotation of the electric motor as a function of this movement.

FIG. 6shows a third embodiment of the invention that is similar to the first embodiment shown inFIGS. 1 to 4, except that the carriage carrying the electric motor in this embodiment is mounted to be stationary relative to the reference member.

Thus, the movement apparatus has a reference member201connected at one end to an operating line211via a first strain gauge250and connected at an opposite end to the operating line211via a second strain gauge251. A carriage205is mounted stationary relative to the reference member201and carries an electric motor224.

Downwardly exerted traction on the operating line211causes the first strain gauge250to deform, which then delivers a signal causing the electric motor224to be operated in a direction to cause the assembly comprising the carriage and the reference member to move upwards. Conversely, upwardly exerted traction on the operating line211causes the second strain gauge251to be deformed, which delivers a signal causing the electric motor224to be rotated in a direction for lowering the assembly comprising the carriage and the reference member.

Naturally, the invention is not limited to the embodiment described and variant embodiments may be applied thereto without going beyond the ambit of the invention as defined by the claims.

Although the invention is described with reference to moving theatre scenery, the invention applies to any device for moving a load. The symmetrical operation of the force compensation motor makes it possible to use a counterweight to increase the load capacity of the system.

Although the invention is described with a motor assembly comprising an electric motor associated with a roller chain, the invention may be implemented with any motor assembly.

Although the invention is described with the carriage sliding relative to the reference member, the invention may be implemented with parts that are hinged relative to one another.

The invention may include additional control means, in particular manual control means, and for example pushbuttons or a remote control. These additional control means may also include a computer unit controlling the motor with a programmed sequence.

Although in the first embodiment of the invention relative movement between the reference member and the carriage is measured by the slider38of a potentiometer37, it is also possible to determine this movement, e.g. by using firstly a first angular position sensor associated with one of the pulleys15of the operating line in order to measure the movement of the reference member, and secondly a second angular position sensor associated with one of the deflector pulleys21,22of the carrier cable18or with the outlet shaft26of the electric motor in order to measure the movement of the carriage5. Simple comparison between the measurements taken by the first and second angular position sensors serves to determine the relative movement between the reference member and the carriage.

Another solution for measuring the relative movement of the reference member and the carriage may also be to use a bidirectional strain gauge connecting the attachment point2.1of the operating line to the carriage. The sensor used for detecting the movements of the attachment point may be of any type suitable for measuring movements that are relatively large (such as the movement of the carriage relative to the reference member) or relatively small (such as the deformation of the part carrying the attachment points). The sensor may be a digital sensor.

The sensor may be any force sensor that delivers a signal that can be used for controlling the motor.

In an embodiment in which the electric motor is stationary, the movement device is preferably a looped line having its ends fastened to the reference member, and the carriage is preferably driven by a chain that has ends fastened to the carriage in order to form a loop around deflection gearwheels that mesh with an outlet gearwheel of the stationary motor.