CA2064507C - Retractable stage safety device - Google Patents
Retractable stage safety deviceInfo
- Publication number
- CA2064507C CA2064507C CA 2064507 CA2064507A CA2064507C CA 2064507 C CA2064507 C CA 2064507C CA 2064507 CA2064507 CA 2064507 CA 2064507 A CA2064507 A CA 2064507A CA 2064507 C CA2064507 C CA 2064507C
- Authority
- CA
- Canada
- Prior art keywords
- stage
- platform
- lowering
- rate
- safety device
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 238000006073 displacement reaction Methods 0.000 claims abstract description 14
- 230000003100 immobilizing effect Effects 0.000 claims description 3
- 238000000034 method Methods 0.000 claims 2
- 230000009975 flexible effect Effects 0.000 description 3
- 230000001133 acceleration Effects 0.000 description 2
- 230000000875 corresponding effect Effects 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04H—BUILDINGS OR LIKE STRUCTURES FOR PARTICULAR PURPOSES; SWIMMING OR SPLASH BATHS OR POOLS; MASTS; FENCING; TENTS OR CANOPIES, IN GENERAL
- E04H3/00—Buildings or groups of buildings for public or similar purposes; Institutions, e.g. infirmaries or prisons
- E04H3/10—Buildings or groups of buildings for public or similar purposes; Institutions, e.g. infirmaries or prisons for meetings, entertainments, or sports
- E04H3/22—Theatres; Concert halls; Studios for broadcasting, cinematography, television or similar purposes
- E04H3/24—Constructional features of stages
- E04H3/26—Revolving stages; Stages able to be lowered
Landscapes
- Engineering & Computer Science (AREA)
- Architecture (AREA)
- Multimedia (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Emergency Lowering Means (AREA)
- Refuge Islands, Traffic Blockers, Or Guard Fence (AREA)
Abstract
A retractable stage for use such as a school stage in an auditorium and the like is normally stored in an upright, retracted position against an end-wall of the auditorium, and when deployed, is lowered such that the bottom that forms the front of the stage advances outwardly into the room, while the top is lowered vertically down the wall, to its operative position, to form the back of the stage. A
retaining safety device attached to the stage incorporates a brake such that, in the event the stage "runs away", at any point of its deployment/retraction cycle, the movement of the stage is limited to a predetermined maximum displacement, and is then automatically braked to a fast stop.
retaining safety device attached to the stage incorporates a brake such that, in the event the stage "runs away", at any point of its deployment/retraction cycle, the movement of the stage is limited to a predetermined maximum displacement, and is then automatically braked to a fast stop.
Description
2~ 5-~7 RETRACTABLE STAGE SAFETY DEVICE
Technical Field This invention is directed to a safety device, and in particular to a run-away prevention device, to prevent the running away of an upwardly retractable stage, during the deployment/retraction cycle thereof.
Background Art A retractable stage, well known in Canada as the "MADSEN" (T.M.) retractable stage, has been widely used in school auditoriums and the like for many years, particularly in the Province of Ontario.
The manner of deployment/retraction of this vertically stowed stage provides that the bottom of the vertically stowed stage advances outwardly, into the room as the top of the stage is lowered vertically down the wall against which it is stowed, to form the rear of the stage when fully deployed to a lowered position.
While the safety history of the subject stage is enviable, in that runaways, during the deployment/retraction cycle are virtually unknown, the possibility does exist that component failure could lead to the run-away of a stage, with dangerous and even tragic consequences. Thus, with the stage in an inclined position, having the bottom or foot thereof ~' ~b45~ 7 displaced outwardly from its stowed position, release of the from its hoisting mechanism would permit rapid outward acceleration of the bottom portion, on its supporting rollers, as the raised portion accelerates freely downwardly under gravity.
The MADSEN (T.M.) stage incorporates folding legs, on which it stands, when deployed. In the case of a 20 x 12 foot stage, weighing some 2,000 pounds, a test was carried out wherein the bottom end of a stowed stage was pulled outwardly, so as to incline the stage against its supporting wall. The securing cable by which the stage is lowered was slacked off, to permit unrestricted vertical movement of the inclined stage, and the bottom was then released.
The stage bottom accelerated forwardly into the room and the top accelerated downwardly until it impacted the floor. The impact drove the supporting legs upwardly, destructively. Anyone standing in the floor space taken up by the stage would inevitably have been injured, with little chance to save themselves.
Disclosure of the Invention In accordance with the present invention, in a plat-form stowed vertically, for lowering to a horizontally deploy-ed position, having a first, deployment means for lowering and raising the platform between a vertical and a horizontal 2064507 `
orientation, there is provided a safety device having fixed pulley means, attachment means connecting the the pulley means to a displaceable portion of the platform, brake means for immobilizing the pulley means and rate responsive brake control means to apply the brake and immobilize the pulley means and the platform upon the occurrence of platform dis-placement at a rate in excess of a predetermined deployment rate.
It will be understood that the subject safety device is operative at all times of platform displacement, regardless of whether the platform is in course of being deployed or retracted.
It will also be understood that the present invention may be used with a retractable stage of the well-known MADSEN (T.M.) type, having articulated and retractable supporting legs which support the stage when lowered in the horizontal deployed condition, as well as with other types of stage wherein different stage support systems may exist.
In a preferred embodiment the present invention com-prises a retractable stage in combination with a safety device comprising an anchored inertia reel, wherein, during opera-tion, the downward and outward displacement of the platform at normal lowering speed results in operation of the reel drum in an unchecked, freely unreeling fashion, under the tensile load applied by the attachment means interconnected between the platform and the reel drum; and wherein displacement of the platform at an appreciably higher rate brings inertia means into play, to brake the reel drum to a standstill, thereby immovably tethering the platform by way of the att~chment means to the anchored reel. It will however be understood that safety devices alternative to the above-referred to inertia reel may be used, such as disclosed herein.
Brief Description of Drawings Certain embodiments of the invention are described by way of example, without limiting the invention thereto, reference being made to the accompanying drawings, wherein;
Figure 1 is a perspective view of a retractable stage in co-mbination with the safety system in accordance with the present invention;
Figure 2 is a side elevation of the Figure 1 embodi-ment;
Figure 3 is a diametrical section of an inertia reel embodiment of a safety device for use in the co-mbined system;
Figure 4 is a side view of the Figure 3 embodiment;
and Figure 5 is a schematic arrangement of a further embodiment of a safety device in accordance with the present invention.
-- ~064507 Best Mode of Carrying out the Invention Referring to Figures 1 and 2, the retractable stage 10 includes a platform 12. A stage housing 14 is secured to a back wall 15 of a suitable hall or auditorium.
The stage retracting mechanism 16 comprises a motor driven reduction gear and pulley having a cable 18 trained over pulleys 20, 22 and attached by hook and eye 21 to the platform 12.
A safety device 22, firmly anchored to adjacent sup-port structure such as the rear wall, is attached by a flex-ible strap 24 to the platform 12. A series of wedges 28 mounted upon floor 26, within the housing 14 engage dolley wheels 30 when the platform 12 is retracted.
Referring to Figure 3, the safety device 22 is illustrated as an inertia type reel. The device 22 has a main housing 32 containing drum spindle 34 on which the flexible strap 24 is coiled.
A side housing 36 contains a coiled spring 38 having an end 40 thereof anchored to pin 42.
The other, inner end of spring 38 is secured at 44 to an extension portion of drum spindle 34.
An oppositely located side housing 46 contains inertia anchor 48.
The inertia anchor 48 has an outer driving member 50 secured to the drum spindle 34, for rotation therewith.
A driven member 52, slideably mounted upon drum spindle 34 has peripheral cam surfaces 54 that can contact adjacent peripheral cam surfaces 56 of driving member 50.
Respective buttress surfaces 55, 57 of members 50, 52 also provide driving connection therebetween.
A light spring 58 tends to press the driven member 52 axially outwardly into a connecting relation with driving member 50, somewhat as shown.
The driven member 52 has an inner annulus of axially projecting ratchet teeth 60 in facing relation with a corres-ponding fixed annulus of ratchet teeth 62 projecting axially outwardly of housing wall portion 64 of main housing 32.
In operation, lowering of cable 18 permits the dolley wheels 30 to deploy down the ramps 28, leading the front of platform 12 outward. With the flexible strap 24 being deployed outwardly as indicated by the directional arrow as the platform 12 lowers, the driving member 50 of safety device 22 is rotated in the arrowed direction. This causes the cam surface 56 of driving member 50 to contact the corres-ponding cam surfaces 54 of driven member 52.
In the event of a sudden acceleration outwardly of the platform 12, the driving member 50 is correspondingly accelerated. The inertia of driven member 52 generates an axially inward reactive force, due to the inclination of cam faces 54, 56.
This force overcomes the spring 58 and drives the teeth 60 into locking engagement with the fixed teeth 62, thus abruptly halting rotation of driven mem~ber 52. This in turn halts rotation of the driving member 50, thereby halting drum spindle 34, to preclude further unwinding of strap 24, thus immobilizing the platform 12.
The reactive force between cam faces 56, 54 main-tains the driven member 52 in its inwardly displaced position, with the ratchet teeth 60 thereof firmly engaged with the fix-ed ratchet teeth 62.
While not illustrated, as not forming a part of the present invention, the platform 12 may have retractable legs, in order to m;n;m;ze space requirements when stowed.
Figure 4 shows a side view of the safety device 22, anchored by way of mounting flange 64 to leg bolts 66. Refer-ring to the Figure 5 e-m-bodiment a safety device 72 has a main housing 74 containing the strap 24 coiled upon drum spindle 34 for connection to platform 12. An electro/mechanical brake 76 has brake shoe 78 that is powered by spring 80 to the "on"
position, in which a portion 34' of drum spindle 34 (not shown) is engaged. An electromagnet 82, when energized, holds the brake 76 in an "off" or disengaged position.
A motion rate detector 84, illustrated as reading from the strap 24, the rate of displacement of the platform 12, transmits a rate signal to rate discriminator 86 connects by way of amplifier 88 to relay 90 which is coupled to the electromagnet 82.
In operation, in the event that the rate of dis-placement of strap 84 exceeds a predetermined upper limit, the discriminator 86 transmits a signal, by way of amplifier 88 to the relay 90, causing it to open.
This disconnects the electromagnet 82 from supply, thereby permitting the spring 80 to apply the brake shoe 78, so as to stop the unwinding of strap 24. Motion rate detector 84 may be a proximity sensor or may utilize dynamic or static magnetic coupling means.
While illustrated with reference to the strap 24, the motion rate detector 84 may conveniently be located within the housing of the safety device 72, to read-off the motion of a portion of the rotating drum.
Also, it will be recognized that the brake 76 may be of the dogged type, for positive braking, as opposed to the illustrated friction brake.
It is evident that the electro/mechanical brake is made fail-safe, in that failure of the power supply will auto-matically apply the brake 76.
Technical Field This invention is directed to a safety device, and in particular to a run-away prevention device, to prevent the running away of an upwardly retractable stage, during the deployment/retraction cycle thereof.
Background Art A retractable stage, well known in Canada as the "MADSEN" (T.M.) retractable stage, has been widely used in school auditoriums and the like for many years, particularly in the Province of Ontario.
The manner of deployment/retraction of this vertically stowed stage provides that the bottom of the vertically stowed stage advances outwardly, into the room as the top of the stage is lowered vertically down the wall against which it is stowed, to form the rear of the stage when fully deployed to a lowered position.
While the safety history of the subject stage is enviable, in that runaways, during the deployment/retraction cycle are virtually unknown, the possibility does exist that component failure could lead to the run-away of a stage, with dangerous and even tragic consequences. Thus, with the stage in an inclined position, having the bottom or foot thereof ~' ~b45~ 7 displaced outwardly from its stowed position, release of the from its hoisting mechanism would permit rapid outward acceleration of the bottom portion, on its supporting rollers, as the raised portion accelerates freely downwardly under gravity.
The MADSEN (T.M.) stage incorporates folding legs, on which it stands, when deployed. In the case of a 20 x 12 foot stage, weighing some 2,000 pounds, a test was carried out wherein the bottom end of a stowed stage was pulled outwardly, so as to incline the stage against its supporting wall. The securing cable by which the stage is lowered was slacked off, to permit unrestricted vertical movement of the inclined stage, and the bottom was then released.
The stage bottom accelerated forwardly into the room and the top accelerated downwardly until it impacted the floor. The impact drove the supporting legs upwardly, destructively. Anyone standing in the floor space taken up by the stage would inevitably have been injured, with little chance to save themselves.
Disclosure of the Invention In accordance with the present invention, in a plat-form stowed vertically, for lowering to a horizontally deploy-ed position, having a first, deployment means for lowering and raising the platform between a vertical and a horizontal 2064507 `
orientation, there is provided a safety device having fixed pulley means, attachment means connecting the the pulley means to a displaceable portion of the platform, brake means for immobilizing the pulley means and rate responsive brake control means to apply the brake and immobilize the pulley means and the platform upon the occurrence of platform dis-placement at a rate in excess of a predetermined deployment rate.
It will be understood that the subject safety device is operative at all times of platform displacement, regardless of whether the platform is in course of being deployed or retracted.
It will also be understood that the present invention may be used with a retractable stage of the well-known MADSEN (T.M.) type, having articulated and retractable supporting legs which support the stage when lowered in the horizontal deployed condition, as well as with other types of stage wherein different stage support systems may exist.
In a preferred embodiment the present invention com-prises a retractable stage in combination with a safety device comprising an anchored inertia reel, wherein, during opera-tion, the downward and outward displacement of the platform at normal lowering speed results in operation of the reel drum in an unchecked, freely unreeling fashion, under the tensile load applied by the attachment means interconnected between the platform and the reel drum; and wherein displacement of the platform at an appreciably higher rate brings inertia means into play, to brake the reel drum to a standstill, thereby immovably tethering the platform by way of the att~chment means to the anchored reel. It will however be understood that safety devices alternative to the above-referred to inertia reel may be used, such as disclosed herein.
Brief Description of Drawings Certain embodiments of the invention are described by way of example, without limiting the invention thereto, reference being made to the accompanying drawings, wherein;
Figure 1 is a perspective view of a retractable stage in co-mbination with the safety system in accordance with the present invention;
Figure 2 is a side elevation of the Figure 1 embodi-ment;
Figure 3 is a diametrical section of an inertia reel embodiment of a safety device for use in the co-mbined system;
Figure 4 is a side view of the Figure 3 embodiment;
and Figure 5 is a schematic arrangement of a further embodiment of a safety device in accordance with the present invention.
-- ~064507 Best Mode of Carrying out the Invention Referring to Figures 1 and 2, the retractable stage 10 includes a platform 12. A stage housing 14 is secured to a back wall 15 of a suitable hall or auditorium.
The stage retracting mechanism 16 comprises a motor driven reduction gear and pulley having a cable 18 trained over pulleys 20, 22 and attached by hook and eye 21 to the platform 12.
A safety device 22, firmly anchored to adjacent sup-port structure such as the rear wall, is attached by a flex-ible strap 24 to the platform 12. A series of wedges 28 mounted upon floor 26, within the housing 14 engage dolley wheels 30 when the platform 12 is retracted.
Referring to Figure 3, the safety device 22 is illustrated as an inertia type reel. The device 22 has a main housing 32 containing drum spindle 34 on which the flexible strap 24 is coiled.
A side housing 36 contains a coiled spring 38 having an end 40 thereof anchored to pin 42.
The other, inner end of spring 38 is secured at 44 to an extension portion of drum spindle 34.
An oppositely located side housing 46 contains inertia anchor 48.
The inertia anchor 48 has an outer driving member 50 secured to the drum spindle 34, for rotation therewith.
A driven member 52, slideably mounted upon drum spindle 34 has peripheral cam surfaces 54 that can contact adjacent peripheral cam surfaces 56 of driving member 50.
Respective buttress surfaces 55, 57 of members 50, 52 also provide driving connection therebetween.
A light spring 58 tends to press the driven member 52 axially outwardly into a connecting relation with driving member 50, somewhat as shown.
The driven member 52 has an inner annulus of axially projecting ratchet teeth 60 in facing relation with a corres-ponding fixed annulus of ratchet teeth 62 projecting axially outwardly of housing wall portion 64 of main housing 32.
In operation, lowering of cable 18 permits the dolley wheels 30 to deploy down the ramps 28, leading the front of platform 12 outward. With the flexible strap 24 being deployed outwardly as indicated by the directional arrow as the platform 12 lowers, the driving member 50 of safety device 22 is rotated in the arrowed direction. This causes the cam surface 56 of driving member 50 to contact the corres-ponding cam surfaces 54 of driven member 52.
In the event of a sudden acceleration outwardly of the platform 12, the driving member 50 is correspondingly accelerated. The inertia of driven member 52 generates an axially inward reactive force, due to the inclination of cam faces 54, 56.
This force overcomes the spring 58 and drives the teeth 60 into locking engagement with the fixed teeth 62, thus abruptly halting rotation of driven mem~ber 52. This in turn halts rotation of the driving member 50, thereby halting drum spindle 34, to preclude further unwinding of strap 24, thus immobilizing the platform 12.
The reactive force between cam faces 56, 54 main-tains the driven member 52 in its inwardly displaced position, with the ratchet teeth 60 thereof firmly engaged with the fix-ed ratchet teeth 62.
While not illustrated, as not forming a part of the present invention, the platform 12 may have retractable legs, in order to m;n;m;ze space requirements when stowed.
Figure 4 shows a side view of the safety device 22, anchored by way of mounting flange 64 to leg bolts 66. Refer-ring to the Figure 5 e-m-bodiment a safety device 72 has a main housing 74 containing the strap 24 coiled upon drum spindle 34 for connection to platform 12. An electro/mechanical brake 76 has brake shoe 78 that is powered by spring 80 to the "on"
position, in which a portion 34' of drum spindle 34 (not shown) is engaged. An electromagnet 82, when energized, holds the brake 76 in an "off" or disengaged position.
A motion rate detector 84, illustrated as reading from the strap 24, the rate of displacement of the platform 12, transmits a rate signal to rate discriminator 86 connects by way of amplifier 88 to relay 90 which is coupled to the electromagnet 82.
In operation, in the event that the rate of dis-placement of strap 84 exceeds a predetermined upper limit, the discriminator 86 transmits a signal, by way of amplifier 88 to the relay 90, causing it to open.
This disconnects the electromagnet 82 from supply, thereby permitting the spring 80 to apply the brake shoe 78, so as to stop the unwinding of strap 24. Motion rate detector 84 may be a proximity sensor or may utilize dynamic or static magnetic coupling means.
While illustrated with reference to the strap 24, the motion rate detector 84 may conveniently be located within the housing of the safety device 72, to read-off the motion of a portion of the rotating drum.
Also, it will be recognized that the brake 76 may be of the dogged type, for positive braking, as opposed to the illustrated friction brake.
It is evident that the electro/mechanical brake is made fail-safe, in that failure of the power supply will auto-matically apply the brake 76.
Claims (8)
1. A platform lowering system having a vertically stow-able platform, hoisting means for selectively raising and low-ering a rear edge of the platform relative to said vertically stowed position;
lateral displacement means for moving a lower portion of said platform forwardly, upon lowering of the stow-ed platform, to incline the platform rearwardly upward;
at least one safety device having fixed pulley means;
attachment means connecting the pulley means to a displaceable portion of said stowed platform;
brake means for immobilizing said pulley means;
and rate responsive brake control means, responsive to the rate of displacement of said platform to apply said brake and immobilize said pulley upon the occurrence of plat-form displacement at a rate in excess of a predetermined deployment rate.
lateral displacement means for moving a lower portion of said platform forwardly, upon lowering of the stow-ed platform, to incline the platform rearwardly upward;
at least one safety device having fixed pulley means;
attachment means connecting the pulley means to a displaceable portion of said stowed platform;
brake means for immobilizing said pulley means;
and rate responsive brake control means, responsive to the rate of displacement of said platform to apply said brake and immobilize said pulley upon the occurrence of plat-form displacement at a rate in excess of a predetermined deployment rate.
2. The system as set forth in Claim 1, said at least one safety device comprising an inertia reel wherein operation at normal lowering speeds results in normal deployment of said platform, and wherein displacement of said platform in the direction of deployment at a significantly increased speed terminates rotation of said reel and said pulley, to secure said platform by said attachment means.
3. The system as set forth in Claim 1 or Claim 2, wherein said platform is a stage.
4. The system as set forth in Claim 1 or Claim 2, said platform having rotatable wheel means in supporting relation with a lower portion of said platform.
5. The system as set forth in Claim 1 or Claim 2, wherein said platform is a stage, said lateral displacement means comprising ramp means to cant said stage outwardly upon lowering thereof along said ramp means.
6. The system as set forth in Claim 1, said at least one safety device comprising a fail safe electrically operated braking device.
7. The method of deploying a stage from an edge-stowed position to a horizontal, deployed position, including the steps of providing a first lowering means securely anchored above said stage when in said stowed position, for selectively raising and lowering the rear of said stage at a predetermined normal value; providing a first securement means securely anchored to a support structure and attached to a portion of said stage and operable in an unloaded lowering sense at a rate not exceeding a predetermined maximum deployment value slightly in excess of said predetermined normal value, whereby upon displacement of said stage portion at a rate in excess of said normal value said stage is secured by said first secure-ment means independently of said first lowering means.
8. The method as set forth in Claim 7, including pro-viding lateral displacement means, to displace said stage into a inclined position, upon lowering thereof from a normally stowed position.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2064507 CA2064507C (en) | 1992-03-31 | 1992-03-31 | Retractable stage safety device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2064507 CA2064507C (en) | 1992-03-31 | 1992-03-31 | Retractable stage safety device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2064507A1 CA2064507A1 (en) | 1993-10-01 |
| CA2064507C true CA2064507C (en) | 1995-07-18 |
Family
ID=4149531
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2064507 Expired - Fee Related CA2064507C (en) | 1992-03-31 | 1992-03-31 | Retractable stage safety device |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2064507C (en) |
-
1992
- 1992-03-31 CA CA 2064507 patent/CA2064507C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2064507A1 (en) | 1993-10-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |