DRIVE SYSTEM

Abstract: A drive system for a roller door comprises a motor; an output shaft from the motor; and a drive flange drivably connected to the output shaft and adapted to be mounted within the barrel of the roller door in driving engagement therewith. The drive assembly further comprises a braking surface mounted for rotation with the output shaft of the motor and auxiliary drive means for driving the output shaft of the motor, comprising a friction disc having a first frictional contact surface selectively engageable with the braking surface mounted for rotation with the motor output shaft and a second frictional contact surface, and an electromagnetic brake assembly including a contact pad for contacting the second frictional contact surface of the override drive means, which contact pad is movable between a release position when electrical energy is being supplied to the motor and to the electromagnetic brake assembly and a braking position when the supply of electrical energy to the motor and to the electromagnetic brake assembly is interrupted. When the supply of electrical energy to the motor and to the electromagnetic brake assembly is interrupted, the first frictional contact surface is engaged with the braking surface and the second frictional contact surface is engaged with the second contact surface of the auxiliary drive means.

Description: Title: Drive System The present invention relates to a drive system, in particular a drive system for a roller door, in particular a roller shutter door or a rubber door. Roller shutter doors and rubber doors are widely used in commercial and industrial application, as security doors and/or for protection against fire. In such applications, the door is mounted on a barrel and is raised by rotating the barrel in a first direction and hence winding the door onto the barrel and lowered by rotating the barrel in the opposite direction and hence unwinding the door from the barrel. Known manual override systems may have the disadvantage that they require an electromechanical interlock. This means that, in order to engage the manual drive it is necessary to engage the manual drive mechanically, allow a microswitch to detect that the manual drive is engaged and then to switch off power to the motor. It is a disadvantage of such a system that, in the case of failure of the microswitch to operate, power is still switched to the main motor. In an alternative design of known manual override system, it is necessary for the operator to pull the manual drive into engagement which has the disadvantage that the manual override can be engaged even when it is not required. It is known to rotate the barrel manually or by means of a motorised drive system, generally using an electric motor. It is also known to provide a manual override for a motorized drive system, in case of power failure or failure of the motor. In a motorised drive system, it is necessary to provide means for driving the barrel to raise the door, and also to hold the door in the open, or raised position, against the weight of the door, i.e. to prevent what is known as "back drive". In a conventional motorised drive system, friction is added to the system in order to prevent back drive. The frictional forces operate at all times, against the motor, to hold the door in a braked position. This means that when the motor is operating to rotate the barrel and raise the door, it is not only lifting the door, but also working against the friction. Typically, if an output of 180w would be required to raise the door, then a further output of 180w is required to overcome the frictional forces. This has the disadvantage that it is necessary to use a more highly rated motor than would otherwise be required, and excess heat is generated. As a practical requirement, the motor must be able to operate for a reasonable period, typically for at least 8 minutes before thermal cut out, which means in practice that, in order to achieve this performance, it has been found desirable to use a motor which can operate at a high temperature. In practice, an F-class motor is generally used, but even with such a motor the working temperature is close to the temperature at which the thermal cut out will operate, which is clearly disadvantageous. If it were not necessary to overcome the added frictional forces, then it would be possible either to use a cheaper B-class motor or to use an F-class motor operating well within its temperature range. The use of a motor to overcome excessive frictional forces leads to increased energy consumption and may reduce the life of the motor. For applications where the door only has to be raised and lowered infrequently, for example fire doors or security doors which are typically only raised and lowered at the beginning and end of the working day, this increased energy consumption may not be a significant problem. In other applications, where the doors are raised and lowered frequently, the increased energy consumption and restricted operating time are significant disadvantages. It is an object of the present invention to provide a drive system for a roller door in which the above disadvantages are reduced or substantially obviated. It is a further object of the present invention to provide a drive system for a roller door in which it is not possible for the power to the main motor to be switched on while an operator to be operating the manual drive. The present invention provides a drive system for a roller door, which drive system comprises a motor; an output shaft from the motor; and a drive flange drivably connected to the output shaft and adapted to be mounted within the barrel of the roller door in driving engagement therewith characterised in that the drive assembly further comprises a braking surface mounted for rotation with the output shaft of the motor, auxiliary drive means for driving the output shaft of the motor and comprising a friction disc having a first frictional contact surface selectively engageable with the braking surface mounted for rotation with the motor output shaft and a second frictional contact surface, and an electromagnetic brake assembly including a contact pad for contacting the second frictional contact surface of the override drive means, which contact pad is movable between a release position when electrical energy is being supplied to the motor and to the electromagnetic brake assembly and a braking position when the supply of electrical energy to the motor and to the electromagnetic brake assembly is interrupted and the first frictional contact surface is engaged with the braking surface and the second frictional contact surface is engaged with the second contact surface of the auxiliary drive means. In a preferred embodiment of the drive system according to the invention, the auxiliary drive means is manually powered. In a further preferred embodiment of the drive system according to the invention the auxiliary drive means is powered by means of an auxiliary motor which auxiliary motor is preferably powered by a battery, in particular a rechargeable battery. The auxiliary motor can be programmed to drive the door into the closed state in a controlled manner if, for example, there is a power failure when the door is in the open or partially open state. This embodiment is particularly suitable for use where the roller door operates as a fire door, since if there is a failure of mains power, the door can be lowered automatically in a controlled manner using the auxiliary motor and thus providing an effective fire barrier. An embodiment of a drive system for a roller door will now be described with reference to the accompanying drawings, in which: Figure 1 is a view of a shutter door assembly; Figure 2 is a longitudinal sectional view of an embodiment of a drive system. As can be seen from Figure 1, a roller door assembly shown generally at 10 comprises a door 2 mounted on a barrel 4 by means of fixings 6. The assembly 10 is mounted in a fixed framework 8. An axle 12 projects from one end 14 of the barrel 4 and is received in a bearing 16 mounted on the framework 8. A drive assembly shown generally at 18 is located at the other end 20 of the barrel 4 in driving engagement therewith. The door 2 may be of any suitable flexible construction, such as interlinked metal laths or rubber sheeting. As the barrel 4 is rotated in a first direction, the door 2 is wound onto the barrel 4 and the door 2 is raised and hence is opened. Rotation of the barrel 4 in the opposite direction unwinds the door 2 from the barrel 4, and the door is lowered and hence closed. An embodiment of a drive assembly is shown generally at 18 in Figure 2. A motor 22 which is of the squirrel cage or induction type is located within a housing 24. The motor 22 comprises a rotor assembly 26 mounted within a stator 28. A hollow rotor shaft 30 is mounted in the rotor 26 for rotation therewith. A first end 32 of the shaft 30 engages the first stage 34 of a three stage planetary gear box 36. The first stage 34 of the gear box 36 is connected via a second stage 38 to an output or third stage 40 of the gear box 36. The output stage 40 is drivingly connected to a drive bung 42 by means of a drive pin 44. The shaft 30 is supported by a bearing 46, which is itself retained by a ring gear end cap 48 fixedly mounted within the housing 2. The drive bung 42 is adapted to be mounted inside the barrel 4 of the door assembly 10 in driving engagement therewith. The second end 50 of the shaft 30 of the motor 22 extends from the rotor 26 away from the gearbox assembly 36. A brake disc 52 is mounted on the end 50 of the shaft 30 for rotation therewith. The brake disc 52 is supported by a ball bearing 54 and is provided with a polished contact surface 56 on its face remote from the motor 22. An electro magnetic brake assembly shown generally at 60 comprises a pair of electromagnets 62, compression springs 64 and a polished contact surface 66, and is mounted within the housing 24 in axial alignment with the motor 22 and shaft 30. The contact surface 66 of the electromagnetic brake assembly 60 faces towards the contact surface 56 of the brake disc 52 and is spaced therefrom. A clutch/brake assembly shown generally at 68 comprises a friction disc 70 provided with friction pads 72, 74 mounted on an auxiliary drive shaft 76 for rotation therewith and is mounted within the housing 24. The shaft 76 is axially aligned with the shaft 30 of the motor 22 and extends through the hollow centre of the electromagnetic brake assembly 60 effectively to form a split spine shaft assembly. The end of the shaft 76 remote from the friction disc 70 is connected to an auxiliary drive system 78, which may be operated manually or by means of an auxiliary motor. The clutch/brake assembly 68 is located so that the friction disc 70 is positioned between the brake disc 52 and the brake surface 66. The friction disc 70 is provided on each face thereof with a friction surface 72, 74. In normal operation of the drive assembly shown generally at 18, when the power supply to the motor 22 and to the electromagnetic brake assembly 60 is interrupted, and there is no current flow, the electromagnets 62 do not exert any magnetic force, and the contact surface 66 is urged by the biassing force of the compression springs 64 towards the friction disc 70. The contact surface 66 engages and brakes the braking surface 72 of the friction disc 70 and the opposed brake surface 74 engages and brakes the contact surface 56 of the brake disc 52. The drive flange 42 is thus braked against rotation. Power can be selectively supplied to the motor 22, and to the electromagnetic brake assembly 60 by means of a conventional switch mechanism (not shown). As power is supplied to the electromagnetic brake assembly 60, the magnets 62 operate against the biassing force of the compression spring 64 and the contact surface 66 is disengaged from the facing brake surface 72 of the friction disc 70. The brake surface 74 disengages from the contact surface 56 and the shaft 30 is thus free to rotate. At the same time as power is supplied to the electromagnetic brake assembly 60, it is also supplied to the motor 22. The shaft 30 is driven by the motor 22 and drive is transmitted to the drive flange 42 via the three stage planetary gear box 36. In the event that there is an interruption in the power supply, due to a mains failure, fire or other reason, the interruption in power supply to the electromagnetic brake assembly 60 causes the brake assembly to engage and allows the door 2 to be held in the position, either open, closed or partially open, in which it was when the supply failed. An auxiliary drive 78 may be incorporated to allow the door to be opened or closed either manually or automatically in the case of an interruption to the power supply. In the case where it is desired to be able to either open or close the door 2 manually, then the shaft 76 is rotated in the appropriate direction and the friction disc 70 rotates with the shaft 76. The friction surface 72 slips against the contact subrace 66 of the brake assembly 60 which is prevented from rotating, but the friction surface 74 engages the surface 56 of the brake disc 52 and hence drive the shaft 32, as the friction disc 70 is rotated. The materials from which the friction pads 72 and 74 are manufactured may be selected so that the friction between the pad 74 and the surface 56 is greater than the friction between the pad 72 and the surface 66, suitably by a factor of 2:1. If the roller shutter door is intended primarily as a security door, for example as the entrance door to commercial premises then the auxiliary manual drive 78 may be designed so that it is operable only to lower and close the door 2. Alternatively, if the roller shutter door is intended as a fire control door, then the auxiliary drive 78 may be an auxiliary motor (not shown) powered by rechargeable battery. The auxiliary drive 78 in such a case may be designed in known manner so as to operate in response to a signal either that there has been a mains power failure or that a fire has been detected, to lower the door and thus provide an effective fire barrier.

Claims: CLAIMS 1. A drive system for a roller door, which drive system comprises a motor; an output shaft from the motor; and a drive flange drivably connected to the output shaft and adapted to be mounted within the barrel of the roller door in driving engagement therewith characterised in that the drive assembly further comprises a braking surface mounted for rotation with the output shaft of the motor, auxiliary drive means for driving the output shaft of the motor and comprising a friction disc having a first frictional contact surface selectively engageable with the braking surface mounted for rotation with the motor output shaft and a second frictional contact surface, and an electromagnetic brake assembly including a contact pad for contacting the second frictional contact surface of the override drive means, which contact pad is movable between a release position when electrical energy is being supplied to the motor and to the electromagnetic brake assembly and a braking position when the supply of electrical energy to the motor and to the electromagnetic brake assembly is interrupted and the first frictional contact surface is engaged with the braking surface and the second frictional contact surface is engaged with the second contact surface of the auxiliary drive means. 2. A drive system according to claim 1 characterised in that the auxiliary drive means is manually powered. 3. A drive system according to claim 1 characterised in that the auxiliary drive means is powered by means of an auxiliary motor. 4. A drive system according to claim 1 characterised in that the auxiliary motor is powered by a battery. 5. A drive system according to claim 4 characterised in that the battery is a rechargeable battery. 6. A drive system according to any of claims 3 to 5 characterised in that the auxiliary motor can be programmed to drive the door into the closed state in a controlled manner, open or partially open state.

Inventors: BARRACLOUGH DOMINIC WILLIAM, BARRACLOUGH, DOMINIC, WILLIAM
Applicants: BARRACLOUGH DOMINIC WILLIAM, SECUREDRIVE SYSTEMS LTD, BARRACLOUGH, DOMINIC, WILLIAM, SECUREDRIVE SYSTEMS LIMITED
Application year: 2001
Main classification: E06B9
IPC codes: E06B9