GB2446808A

GB2446808A - Overhead door system having safety brake

Info

Publication number: GB2446808A
Application number: GB0703646A
Authority: GB
Inventors: Michael Edward Deasley
Original assignee: INDUPART Ltd
Current assignee: INDUPART Ltd
Priority date: 2007-02-26
Filing date: 2007-02-26
Publication date: 2008-08-27
Also published as: GB0703646D0

Abstract

An industrial overhead door system has a frame for guiding and supporting a sectional door 12, at least two cables 20 from which the sectional door 12 hangs, and a drive unit for rotatingly driving an axle 16 to unwind or to wind the cables 20 to lower or raise the door 12. The drive unit includes a safety brake which is responsive to a change in speed of the rotational drive and which locks the drive against further rotation. In the event of a failure of the door system whilst the door is opening or closing, the locking of the drive prevents the door from falling, dispensing with the need for a counter-balance arrangement. The safety brake may comprise at least one locking bar 54, preferably two, for locking a rotational portion of the drive unit to a housing. The locking bars 54 may be retained in a disengaged position by projections 48 of a collar 44 engaging in slots in locking rods 54. Upon failure of the motor the weight of the door causes relative movement between collar 44 and a drive cog 40 which disengages retention tabs 48 and releases locking bars 54 which are biased by springs into engagement with the motor housing and prevent further rotation of axle 16.

Description

OVERHEAD DOOR SYSTEM

The present invention relates to an overhead door and in particular to an industrial sectional overhead door of the type used in industrial storage facilities, for example for doorways providing access for heavy freight vehicles.

Existing sectional overhead doors used in industrial storage facilities include a counter balance spring arrangement in order to comply with health and safety standards. However, such counter balance arrangements are expensive to install and require continued maintenance once installed.

According to a first aspect of the present invention there is provided an industrial overhead sectional door system comprising: a frame for supporting and guiding a sectional door between a lowered closed position and a raised opened position; at least two cables from which the sectional door hangs; and a drive unit for rotatingly driving an axle in a first direction so as to unwind each cable to lower the sectional door and in a second direction so as to wind each cable to raise the sectional door, wherein the drive unit comprises a safety brake responsive to a change in speed, for example sudden change in speed of the rotational drive so as to lock the drive unit against further rotation. The door system is configured so that the point of failure for the system is the drive unit, which if it does fail, locks up to prevent the sectional door from falling. Accordingly, the door system according to the present invention has the required safety level of existing sectional overhead doors,

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without the complexity of the counter balance arrangement and its associated disadvantages.

The industrial overhead sectional door system according to the present invention does not include a counterbalanced spring system. Such counterbalance spring systems are located between the axle and the cables, more specifically between the axle and at least two cable drums wherein each cable is wound onto an associated cable drum. According to the present invention there is a direct drive between the axle and the cable drums, in that the cable drums are non-rotatably mounted on the axle.

The drive unit may comprise a rigid housing and the safety brake may comprise at least one locking bar for locking a rotational portion of the drive unit to the housing. Preferably there will be two locking bars. It will be apparent to the person skilled in the art that many locking arrangements responsive to an unexpected and sudden change of rotational speed of the drive unit can be used to lock the drive unit against further rotation. In particular, the drive unit may comprises a motor, an output socket for rotatingly driving the axle and a gear train between the motor and the output socket, in which case the safety brake may be made responsive to a sudden change in the rotational speed of the gear train, or a part thereof, so as to lock the gear train against rotation.

The frame may comprise a pair of upright supports, one to either side of the sectional door, in which case the axle may be mounted for rotation between the upright supports at a level above the top of the sectional door in its closed position. The uprights may be fixed one to either side of an opening which the sectional door forms a closure for. In particular, the axle may be mounted below the top of the sectional door in its open position. In this arrangement, the drive unit may be mounted on one of the upright supports at the level of the axle.

The frame may also comprise a pair of guide tracks for guiding the sectional door between its open and closed positions, wherein a first lower portion of the guide tracks is angled to the vertical by a first angle a and transitions into a second upper portion of the guide tracks which is angled to the vertical by a second angle f3, greater then the first angle a. The door system is generally mounted to the inside wall surrounding an opening, in which case the guide tracks are angled away from the inside wall, so as to provide a space for the axle and drive unit. The guide tracks may be fixed to the upright supports and the transition in the guide tracks may be located at a vertical height in the region of the top of the sectional door in its closed position.

Each cable may be fixed to a bottom panel, of a plurality of panels which form the sectional door. There may be two cables, one located at each side of the sectional door. Each cable may extend along a channel formed between an associated upright support and guide track. Each cable may wound around an associated cable drum, in which case, each cable drum may be non-rotationally mounted on the axle, for example, adjacent and within an associated portion of the frame. a

According to a second aspect of the present invention there is provided kit of parts for making an industrial overhead door system according to the first aspect of the present invention, which kit of parts may comprise the frame, the sectional door, at least two cables, the drive unit and the axle. In particular, the frame may comprise a pair of upright supports and a pair of guide tracks.

The kit may also comprise at least two cable drums.

The invention will now be described by way of example only and with reference to the accompanying schematic drawings, wherein: Figure 1 shows a longitudinal cross-section through a sectional overhead door system according to the present invention; Figure 2 shows a transverse cross-section through line BB of Figure 1; Figure 3 shows a perspective view of an upper portion of a frame of the door system of Figure 1 fitted with a cable drum arrangement; Figure 4 shows in more detail one of the cable drums of the cable drum arrangement of Figure 3; Figure 5 shows a drive unit with an integral gear train safety braking system suitable for driving the cable drum arrangement of Figure 3; Figure 6 shows a perspective view of an end portion of a sectional door suitable for fitment within the frame of Figure 3; and Figure 7 shows details of the safety braking system of the drive unit of Figure 5.

The industrial sectional overhead door system comprises a frame incorporating a pair of upright supports (2) and a pair of door guide tracks (6).

A pair of upright supports (2) are fixed, with one to either side of an entrance opening (8) to a building, so that the upright supports (2) extend substantially vertically. The upright supports (2) are fixed inside the building and extend vertically to a height at least twice the height of the opening (8). A resilient side sealing strip (10) is fixed between each upright support (2) and the wall portion to which the upright support is fixed to, so that the sealing strip extends vertically along either side of the opening. When a sectional door (12) is fitted within the frame, the sealing strip (10) extends from the edge of the opening (10)to a front surface of the sectional door (12) so as to provide a weather proof seal between the edge of the opening and the sectional door, as shown in Figure 2. As can be seen from Figure 2, each upright support (2) has an L-shaped transverse cross-section, with a first leg of the L fixed to the wall portion, entrapping the sealing strip (10) therebetween and a second leg extending inwardly of the opening, to either side of the sectional door (12).

Each upright support (2) has a hole formed therethrough at a predetermined height, above the top of the opening (8) through which an axle (16) of a cable drum arrangement can be fitted for rotation.

The door tracks (6) are fixed, one to each upright support (2), as can be seen in Figure 2. They are fitted to the door side of the second leg of the associated upright support (2). Each door track has a lower length (6a) which inclines from the vertical at a first angle a to the upright support (2) from the base of the frame to a level slightly higher than the top of the opening (8), as shown in Figure 1. The lower length of each door track then transitions into an upper length (6b) which inclines from the vertical at a second angle greater than the first angle a. The inclination of the upper length (6b) of each door track guides the sectional door (12) out of the way of the cable drum arrangement (described below) when the door (12) is lifted. The door guide (6) tracks incline away from the inside wall surrounding the opening, to which the frame is attached.

Each door track (6) has a U-shaped transverse cross-section, as is shown in Figure 2, with the U-shape comprising a planar base (6c), a planar sidewall extending normal to a first end of the base (6d) and a convex sidewall (6e) extending from a second opposite end of the base. The base (6c) of each U-shaped track (6) is fitted against the second leg of the upright support (2) to the door side of the upright support, along the lower length (6a) of the door track. The upper length (6b) of each door track is fixed at its upper end to the associated upright support (2) by a connecting bar (14). The door track (6) is fitted to the upright support (2) with its planar sidewall facing the opening (8) and its convex sidewall (6b) facing away from and bulging away from the opening (8).

A cable drum arrangement is fitted to the frame, at a height substantially half way between the top of the opening (8) and the top of the upright supports (2).

The cable drum arrangement comprises an axle (16) on which are non-rotatably mounted a pair of cable drums (18). The cable drums (18) are mounted on the axle (16), with one of the cable drums adjacent to the second

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leg of an associated upright support (2). The cable drums are mounted to the door side, ie. the inside, of each upright support (2). A cable (20) is wound onto each cable drum (18), with a first end of the cable (20) fixed to the cable drum (18) and a second opposite end of the cable (20) fitted to a base panel of the sectional door (12). A portion of the cable (20) is wound off the cable drum (18) so that it extends along the space between the door track (6) and the first leg of the upright support (2) as shown in Figures 1 and 2. The second end of the cable (20), at the end of the wound off portion is fixed to an associated bracket (22) fixed to an associated end of the bottom panel (1 2a) of the sectional door (12), as is shown in Figure 2. The bracket (22) is formed with a secondary brake. When the cable (20) is taut, the cable counteracts a biasing force on the secondary brake so as to release it. However, when the cable (20) is not taut, the secondary brake is biased into an engaged position so as to brake movement of the sectional door (12).

The sectional door (12) is shown in more detail in Figure 6 and comprises a plurality of articulated door panels (12a-e) connected together by articulated brackets (24) to form a door panel. The brackets (24) enable sufficient movement between adjacent door panels to enable the sectional door (12) to bend so that it can move slowly between the lower length (6a) and upper length (6b) of the door track (6). Each bracket (24) comprises a spur (26) which extends laterally from the side of the sectional door (12) and fits within the door track so as to guide the movement of the door panels (12a-e) along the door track (6) when the sectional door is raised and lowered.

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The base bracket (22) is fixed at either side of the base panel (12a) of the sectional door, as is shown in Figures 2 and 6. A guide roller (28) extends laterally of the base panel and fits within the door track (6) so as to guide the movement of the base of the sectional door, within the door track. The cable (20) is also fixed to the base bracket (22), as is shown in Figure 2.

A drive unit mounting bracket (30) is fixed to the side of the second leg of the upright support, facing away from the sectional door, as is shown in Figures 3 and 4. A drive unit (32) is mounted on the mounting bracket (30) via the mounting plate (34) fixed to the base of the drive unit (32) shown in Figure 5.

The drive unit comprises a motor located within a housing (36) and an output socket (38) driven by the motor via a gear train arrangement. The end of the axle (16) of the cable drum arrangement adjacent to the drive unit (32) is fitted non-rotatably within the output socket (38) so that the axle is rotatably driven by the drive unit (32). The motor operates at a substantially constant rotations per minute (rpm) and so generates an output drive at the output socket (38) which has a substantially constant rpm.

Starting from the closed position shown in Figure 1 with the base panel (1 2a) of the sectional door adjacent the ground and the sectional door (12) covering the opening (8). The operation of the drive unit (32) to drive the output socket in a first rotational direction, acts to rotate the axle (16) and also the cable drums (18) mounted thereon so as to wind more of the cables (20) onto the cable drums. The winding of the cables (20) onto the cable drums (18) causes the sectional door (12), the bottom end of which is fixed to the cables,

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to move upwardly, guided by the rollers (28) and projections (26) moving along the door tracks (6). The drive unit operates until the upper panel (12e) of the sectional door approaches the top of the door tracks (6), so that the opening (8) is exposed and the sectional door system is in its open position.

The operation of the drive unit (32) to drive the output socket in a second rotational direction, opposite to the first rotational direction, acts to rotate the axle (16) and also the cable drums (18) mounted thereon so as to unwind the cables (20) from the cable drums. The unwinding of the cables (20) from the cable drums (18) causes the sectional door (12), the bottom end of which is fixed to the cables, to move downwardly, under the weight of the sectional door (12), guided by the rollers (28) and projections (26) moving along the door tracks. The drive unit operates until the base panel (12a) of the sectional door approaches the bottom of the door tracks (6), so that the opening (8) is closed by the sectional door and the sectional door system is in its closed position, shown in Figure 1.

When the sectional door system is installed, the drive unit (32) is configured to operate only for a number of revolutions required to move the sectional door (12) between the open and closed end positions. End stop restrictions are imposed on the drive unit to prevent further drive from the drive unit once the door has reached an end position.

The drive unit (32) when powered up, operates to generate a rotary drive, via the gear train, from the output socket (38) at a substantially constant speed, as measured for example by rotations per minute (rpm) and so drives the axle at a substantially constant rpm. This substantially constant rpm is maintained for both lowering and lifting of the sectional door, that is, for both rotational directions of drive. The drive unit (32) comprises a safety locking arrangement sensitive to a sudden change in the speed of the rotary drive or a pert of the rotary drive.

If the motor of the drive unit (32) fails, this will affect the substantially constant rpm. The pull of the sectional door (12) on the cable (20), due to the weight of the sectional door, will apply a rotational drive to the output socket (38) of the drive unit (32), via the axle (16). Thus, the failure of the motor disrupts the constant rpm of the drive unit, giving rise to a sudden change in rotational speed. In response to this a safety brake within the drive unit (32) locks the rotational drive, for example, locking the motor, gear train or output socket (38) of the drive unit (32) against further rotation. For example, the motor, gear train or output socket (38) may be locked to the housing of the drive unit (32) to prevent their further rotation. Two locking bars may be released in response to a change in the rpm which locks a rotational portion of the drive unit to the housing. The drive unit safety brake arrangement, thus prevents the sectional door (12) from falling under its own weight, should there be a failure of the drive unit (32). Such falling of the sectional door could be highly dangerous to anyone standing in the vicinity of the door or occupying a vehicle in the vicinity of the door.

There are many such safety brake arrangements available which are sensitive to changes in rpm to lock a motor, or a gear train or a part of a rotational drive train against rotation. The safety brake may be re-settable, for example, once the failure of the motor has been rectified. The safety brake arrangement may be constructed so that the drive unit (32) has to be sent back to its manufacturer or to the supplier of the overhead door for repair or replacement.

One example of a suitable safety brake is shown in Figure 7. The gear train of the drive unit (32) comprises a cog (40) for driving a drive shaft (42) (lower half of Figure 7. A ring shaped thrust collar (44) shown in more detail in the upper half of Figure 7), is formed with a series of peripheral teeth (46) corresponding in shape and spacing to the teeth formed on the cog (40). The thrust collar (44) overlies the cog (40) with the teeth aligned in the lower half of Figure 7 and can rotate with respect to the cog (40). The thrust collar (44) is formed with two pairs of opposing inwardly extending tabs (48) at its inner edge. The cog (40) is formed with two pairs of opposing spurs (50), which extend transversely of the cog (upwards out of the paper in the lower half of Figure 7). Each spur (50) has formed within it a pin receiving channel (52), which channel extends substantially parallel to the axis of rotation of the cog (40). In addition each spur (40) is formed with a slot in its outer periphery at the level of the thrust collar (44) so that the tabs (48) of the thrust collar can be received within the slots in the spurs. For each spur (50) the slot intersects with the channel (52). A pin (54) is slideably located within each channel (52) and a spring extends between the base of each channel (52) and each pin (54) so as to bias the forward ends of the pins out of the corresponding channels. Each pin (54) is formed with a circumferential slot. When the drive unit is assembled, the pins (54) are pressed into corresponding channels (52) against the biasing force of the springs until the circumferential slot in the pins is level with the slots in the spurs (50). Then the thrust collar (44) is laid over the cog and rotated until the tabs (48) engage the slots in the spurs (50) and the slots in the pins so as to hold the pins (54) within the channels (52) against the biasing force of their associated springs.

The housing of the drive unit (32) facing the channels (52) is formed with a series of, for example eight, receiving recess which can receive the forward end of the pins (54) should the forward ends of the pins be biased out of the channels by the springs.

A worm gear transmits drive from the motor of the drive unit (32) to the teeth of the cog (40) and also to the aligned teeth of the thrust collar (44). The drive unit (32) is designed so that its first point of failure would be the teeth on the cog (40).

While the sectional door (12) is being towered, if a tooth were to fail on the cog (40) the cog would slip in its direction of rotation due to the weight of the sectional door, via the cables (20), cable drums (18), axle (12) and output (38) of the drive unit (32). If one of the teeth on the cog (40) shears, the slippage of the cog (40) in this way generates additional forces on the next tooth of the cog as it engages the worm gear and can lead to failure of other cog teeth.

The thrust collar (44) is prevented from slipping with the cog (40) by the engagement of its teeth (46) with the driving worm gear. This causes a relative rotation between the cog (40) and the thrust collar (44).

While the sectional door (12) is being raised, if a tooth were to fail on the cog (40) the cog would slip in a direction opposite to its direction of rotation due to the weight of the sectional door, via the cables (20), cable drums (18), axle (12) and output (38) of the drive unit (32). If one of the teeth on the cog (40) shears, the slippage of the cog (40) in this way generates additional forces on the next tooth of the cog as it engages the worm gear and can lead to failure of other cog teeth. The thrust collar (44) is prevented from slipping with the cog (40) by the engagement of its teeth (46) with the driving worm gear. The thrust collar (44) continues to be rotated at a constant speed by the worm gear while the cog (40) slips back. This causes a relative rotation between the cog (40) and the thrust collar (44).

Relative rotation between the thrust collar (44) and the cog (40) due to failure of the cog, draws the tabs (48) of the thrust plate (44) out of the slots in the pins (54), causing the springs to urge the upper ends of the pins out of the channels (52) to engage one of the receiving recesses in the casing of the drive unit (32). This locks the drive unit (32) against further rotation and ensures that the drive unit does not fail catastrophically. The drive unit (32) can then be repaired or replaced.

Claims

1. An industrial overhead sectional door system comprising: a frame for supporting and guiding a sectional door between a towered closed position and a raised opened position; at least two cables from which the sectional door hangs; and a drive unit for rotatingly driving an axle in a first direction so as to unwind each cable to lower the sectional door and in a second direction so as to wind each cable to raise the sectional door, wherein the drive unit comprises a safety brake responsive to a change in speed of the rotational drive so as to lock the drive unit against further rotation.

2. An industrial overhead door system according to claim I wherein the drive unit comprises a rigid housing and the safety brake comprises at least one locking bar for locking a rotational portion of the drive unit to the housing.

3. An industrial overhead door system according to claim I or claim 2 wherein the drive unit comprises a motor, an output socket for rotatingly driving the axle and a gear train between the motor and the output socket and the safety brake is responsive to lock the gear train against rotation.

4. An industrial overhead door system according to any one of the preceding claims wherein the frame comprises a pair of upright supports, one to either side of the sectional door and the axle is mounted for rotation between the upright supports at a level above the top of the sectional door in its closed position.

5. An industrial overhead door system according to claim 4 wherein the axle is mounted below the top of the sectional door in its open position.

6. An industrial overhead door system according to claim 4 or claim 5 wherein the drive unit is mounted on one of the upright supports at the level of the axle.

7. An industrial overhead door system according to any one of the preceding claims wherein each cable is fixed to a bottom panel of the sectional door.

8. An industrial overhead door system according to any one of the preceding claims wherein the frame comprises a pair of guide tracks for guiding the sectional door between its open and closed positions, wherein a first lower portion of the guide tracks is angled to the vertical by a first angle a and transitions into a second upper portion of the guide tracks which is angled to the vertical by a second angle f3, greater then the first angle a.

9. An industrial overhead door system according to claim 8 when dependent on any one of claims 4 to 6 wherein the guide tracks are fixed to the upright supports.

10. An industrial overhead door system according to claim 8 or claim 9 wherein the transition in the guide tracks is located adjacent to the top of the sectional door in its closed position.

11. An industrial overhead door system according to any one of claims 8 to wherein each cable extends along a channel formed between an associated upright support and guide track.

12. An industrial overhead support system according to any one of the preceding claims, wherein each cable is wound around an associated cable drum and each cable drum is non-rotationally mounted on the axle adjacent.

13. A kit of parts for making an industrial overhead door system according to any one of claims I to 12, comprising the frame, the sectional door, at least two cables, the drive unit and the axle.

14. A kit of parts according to claim 13 wherein the frame comprises a pair of upright supports and a pair of guide tracks.

15. A kit of parts according to claim 13 or claim 14 additionally comprising at least two cable drums.