An elevator braking device

Abstract: A braking device for an elevator, wherein a cage (3) moves along a guide rail. The braking device includes a wedge braking device (10) a speed governor (20) and a linking mechanism. The wedge braking device (10) has wedges (14) which are pressed against the guide rail (2) thereby stopping the cage (3) when the speed governor (20) senses an excess speed or when a weight responsive mechanism senses a fall in weight. The wedge braking device (10) has an hydraulic release mechanism.

Description: This invention relates to an elevator braking device provided with the function of preventing the cage free falling in the event of a malfunction. In recent years types of self running elevator have been proposed wherein the cage runs freely within the ascending/descending path under a drive provided by a linear motor instead of the traction-type elevator wherein the cage is raised and lowered by a winch drive using a conventional suspension rope. Hereinafter the non-winch type elevator is known as a self propelled elevator. A self propelled elevator has a construction, as shown for example in JP-A-02261789, wherein a primary coil and secondary conductor of a linear motor are provided facing each other with a small gap between them on the left and right side faces of the cage and on left and right inside wall faces of the ascending/descending path, whereby the cage runs along guide rails within the ascending/descending path under a propulsive force generated between the primary coil and secondary conductor of the linear motor. Self propelled elevators have various advantages as described below. Since a winch is not employed there is no restriction on the length of the ascent/descent. Its transportation capabilities can be improved by having more than one cage run along a single elevator path. The need to provide a machinery room directly above the ascending/descending path is eliminated. In the self propelled elevators of this type provided with no suspension rope, the linear motor generates a propulsive force so as to raise, lower or stop the cage. There is a risk that the cage could fall in the event of a malfunction. For this reason, safety measures to prevent the cage falling are essential. A braking device is disclosed in JP-A-02261789, and comprises a pair of left and right levers having brake shoes at their ends that are free to open and close to clamp the guide rails. Compression coil springs bias the left and right levers such that the brake shoes at their ends press against the guide rails. Solenoids and links act to open the left and right levers against these compression coil springs. During running of the cage, the solenoids are excited by an applied voltage so that the left and right levers are opened thereby releasing the brake. In braking, voltage to the solenoids is cut off, causing the left and right levers to be closed by the spring force so that the brake shoes are pressed against the guide rails and braking of the cage is effected. Since the self propelled elevator braking device described above employs a system wherein the braking force is provided by contact pressure of the brake shoes with the guide rail produced by the compression spring force extremely powerful compression coil springs are required. In order to release the braking against the compression coil springs, the solenoids themselves must be of large size so as to provide an attractive force of around 1000 kg. This greatly increases the cage weight. EP-A2-0432634 discloses an elevator braking device, wherein a cage moves along a guide rail, comprising: a wedge braking means mounted on said cage; a speed governor means; and a linking means for linking said wedge braking means and said speed governor means; said wedge braking means including, a resilient support member, a wedge guide means, supported by said resilient support member, a wedge member, provided between said guide rail and said wedge guide means, to be pressed against said guide rail by a biasing force generated by said resilient support member, thereby stopping said cage by means of a first frictional force between said guide rail and said wedge member, a releasing means for releasing said resilient support member such that said wedge member separates from said guide rail when a releasing force is generated; and said linking means being linked such that the speed governor pulls up said wedge members along said wedge guide means when said speed governor means detects that a speed of said cage exceeds a rated speed, thereby pressing said wedge member against said guide rail and effecting an emergency stop of said cage by means of a second frictional force between said guide rail and said wedge member, wherein: said wedge braking means includes, a balancing spring means provided under said wedge member for supporting said wedge member, a spring force thereof being set such that said spring force balances the weight of said wedge member so that said wedge member is supported in a positiion with a suitable clearance with respect to said guide rail. The present invention provides an elevator braking device which alleviates at least some of the previously described technical problems. Accordingly the present invention seeks to alleviate the aforesaid technical problems by the provision of a braking device for an elevator wherein a wedge braking means is mounted on an elevator cage and arranged to be engageable with a guide rail to brake the elevator when actuated by a speed governor when the governor senses that the elevator speed exceeds a safe speed. Accordingly the present invention provides an elevator braking device, wherein a cage moves along a guide rail, comprising: a wedge braking means mounted on said cage; a speed governor means provided on said cage for detecting a running speed of said cage; and a linking means for linking said wedge braking means and said speed governor means; said wedge braking means including, a resilient support member, a wedge guide means, supported by said resilient support member, a wedge member, provided between said guide rail and said wedge guide means, to be pressed against said guide rail by a biasing force generated by said resilient support member, thereby stopping said cage by means of a first frictional force between said guide rail and said wedge member, a releasing means for releasing said resilient support member such that said wedge member separates from said guie rail when a releasing force is generated; and said linking means being linked such that the speed governor pulls up said wedge members along said wedge guide means when said speed governor means detects that a speed of said cage exceeds a rated speed, thereby pressing said wedge member against said guide rail and effecting an emergency stop of said cage by means of a second frictional force between said guide rail and said wedge member, wherein: said wedge braking means includes, a balancing spring means provided under said wedge member for supporting said wedge member, a spring force thereof being set such that said spring force balances the weight of said wedge member so that said wedge member is supported in a positiion with a suitable clearance with respect to said guide rail, characterised in that said speed governor means is provided on said cage for detecting a running speed of said cage, said balancing spring is arranged to push up said wedge member along said wedge guide means when the balance betwwen said weight of said wedge member and said spring force is lost by excessively rapid descent of said cage, thereby pressing said wedge member against said guide rail and effecting an emergency stop of said cage by means of a third frictional force between said guide rail and said wedge member. With such an elevator, during ordinary running of the cage, the release mechanism which may comprise an hydraulic ram, releases the resilient support body, and the wedges are thus maintained in a braking-released condition in which the wedges are separated from the guide rail. The cage therefore runs along the guide rails in the ascending/descending path. For stopping at the target floor the release mechanism goes into a no-load condition. As a result, the resilient support body presses the wedges against the guide rail through the wedge guides, so that braking is performed by the resulting frictional force. The cage is thereby held in position stopped at the required floor. In this way the cage running and stopping at the required floor are performed under normal conditions. If the cage runs with a speed exceeding its rated speed due to some malfunction, this excess speed of the cage is detected by the speed governor, which pulls the wedges up between the wedge guides and the guide rail. The wedges are thereby jammed between the wedge guides and the guide rail, generating a powerful braking force, to reliably emergency stop the cage. An embodiment of an elevator braking device constructed in accordance with the present invention, will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a front view of a wedge braking device showing an embodiment of a self propelled elevator according to this invention; Figure 2 is a plan cross-sectional view along the line X-X in Figure 1; Figure 3 is a perspective view of a cage fitted with wedge braking devices and a speed governor of a self propelled elevator according to the above embodiment; Figure 4 is a side view of the speed governor used in the above embodiment; and Figure 5 is a side view, partially sectioned, of a lifting rod hanging down from a safety link of the speed governor. Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, figure 3 is a view of a self propelled elevator driven by a linear motor. A pair of vertical guide rails 2 are provided on the inside wall of an ascending/descending part 1. A cage 3 is arranged so that it can be moved vertically along the guide rails 2. The cage 3 is provided with four guide mechanisms 5 disposed at the upper and lower left and right sides of the cage 3 so that the three guide wheels 4, of each guide mechanism 5 are in rolling contact from three directions with the guide rails 2. As a means for driving the cage 3, secondary conductors 6 of the linear motor are provided on the left and right side faces of the cage 1, and primary coils (not shown) of the linear motor are arranged over the entire length on the left and right wall faces within ascending/descending part 1. Cage 3 can be made to move up or down along guide rails 2, or to stop, within the ascending/descending path 1, by the propulsive force generated between the primary coils of the linear motor and the secondary conductors 6 at the side of the cage 3, by supplying current to the primary coil. An alternative arrangement for the drive system of this linear motor would be to provide the primary coils of the linear motor on the cage 3 and to arrange the two secondary conductors of the linear motor on the inside wall of ascending/descending path 1. In this case, a current collection device is required to supply current from the ascending/descending path side to the primary coils of the linear motor provided on cage 3. As a means of providing braking and preventing falling of the cage 3 of such a linear motor-driven self propelled elevator, wedge braking devices 10 are mounted on the left and right at the bottom of cage 3, as shown in figure 3. A speed governor 20 is provided on one side of and at the top of the cage 3. Balancing springs 40 (see figure 1) are provided in the wedge braking devices 10. As shown in figure 1 and figure 2, each of the wedge braking devices 10 is equipped with; a frame such as a braking device block 11 mounted at the bottom of the cage 3, a resilient support body 12 mounted on the block 11, a pair of left and right wedges 14 arranged to be biased via wedge guides 13 from the leading ends on both sides of the resilient support body 12, so that they are pressed against guide rails 2, and a release mechanism 15 to push open the resilient support body 12 in order to separate the wedges 14 from the guide rail 2 during running of the cage 3. Braking device block 11 of the wedge braking device 10 is provided by an I-section member 11a and upper and lower plates 11b and 11c fixed to the upper and lower ends of the I-section member 11a. The resilient support body 12 consists of a U-shaped plate spring when seen in plan view, and is fixed to the back face of the I-section member 11a, with its two side portions 12a projecting forwards (towards guide rail 2). A pair of left and right wedge guides 13 are provided with grooves in which the ends of the left and right side plate portions 12a respectively engage. The wedge guides 13 are provided with relatively inclined faces 13a arranged opposite each other in an inverted V configuration. Each left and right wedge 14 is provided by a trapezoidal block inside faces of which are disposed vertically in parallel with the guide rail 2. The opposite outside faces are inclined in parallel with inclined faces 13a of guides 13. The left and right wedges 14 are arranged inside the left and right wedge guides 13, and supported on a speed governor 20, and balancing springs 40, so as to clamp guide rail 2 from the left and right. A large number of rollers 16 of small diameter are interposed between the opposite inclined faces of the wedges 14 and wedge guides 13. Release mechanism 15 is comprised of a pair of left and right levers 18 each having an upper end swingably pivoted about a fulcrum 18a provided one each, by a pair of brackets 17. The brackets 17 are supported on the bottom face left and right portions of the upper plate 11b. A single hydraulic cylinder 19 is interposed between the bottom ends of the left and right levers 18. By supplying pressurised oil from an oil pressure source (not shown) mounted on the cage 3 to this hydraulic cylinder 19, the two side plate portions 12a of the resilient body 12 are pushed apart to the left and right, by the motion of the left and right levers 18. Thus the wedges 14 are separated, with a suitable clearance, from the guide rails 2. The speed governor 20 is shown in figures 3 to 5 and has a mounting base 21 fixed to the top of the cage 3, a pressure contact roller 23 is supported on a rocking lever 22 mounted on the base 21 so that a pressure-contact spring 24 forcefully urges the pressure contact roller 23 in rolling contact with the guide rail 2. A governor sheave 26 is freely rotatably journalled on a stand 25 at the inner end of the mounting base 21. The governor sheave 26 is coupled with the pressure contact roller 23 and belt 27. A pair of fly-weights 28 are provided on the governor sheave 26. The fly-weights 28 are arranged such that, at high rotational speed resulting from excess speed of the cage 2, they move outwards in the radial direction so as to kick a sensing lever 29. The sensing lever 29 is arranged to be rotatable about a fulcrum 30 in the mounting base 21, and is linked at its lower end with a rod 31 to linearly move the rod 31. A spring 32 opposes the linear movement of the rod 31. A rotary lever (crankarm) 33 is mounted on the mounting base 21 to pivot about a fulcrum 33a in such a way that a leading end thereof is forced upwards as the rod 31 moves. A long connecting rod 34 extends downwards from the leading end of the rotating lever 33 and a safety link 35 is journalled at the bottom of cage 3 linked to the bottom end of the connecting rod 34. A pair of lifting rods 37 extend downwards from a pair of safety links 36 that are co-axially linked to the safety link 35, and are linked to the left and right wedges 14, respectively. The speed governor 20 is arranged so that when the speed of cage 3 is excessive it is detected by fly-weights 28 linked with pressure contact roller 23 and sensing lever 29, by means of a linkage consisting of rods, levers and links the left and right wedges 14 of wedge-type braking device 10 are drawn in along the inclined faces 13a of wedge guides 13 between wedge guides 13 and guide rail 2. As shown in figure 5, lifting rod 37 that hangs down from safety link 36 is constituted by a tubular member 37a and a rod member 37b slidably received in the tubular member, so that only a lifting force is transmitted to the wedge 14, thereby making it possible to lift wedge 14 by the action of the balancing springs 40. Balancing springs 40 consist of a pair of compression coil springs that support the left and right wedges 14 from below with the aid of a carrier plate 41, as shown in figure 1. The spring force of the two springs 40 is set such that, during normal operation, the spring force is in balance with the weight of wedges 14 and rod members 37b so that the wedges 14 are supported in a position with suitable clearance from the guide rail 2. In the event of excessive acceleration (fast free-fall) of cage 3 due to cut-off of the power or some other malfunction, the balance between the inertial weight of wedges 14 and rod members 37b and the spring force is lost, causing the wedges 14 to be pushed in between the wedge guides 13 and guide rail 2. During normal running of the cage 3, the release mechanism 15 separates the resilient support body 12 using the hydraulic cylinder 19 of the wedge braking device 10 so that the left and right wedges 14 are maintained in a brake-released condition, separated from the guide rail 2, As a result, cage 3 runs along the guide rails 2 in the ascending.descending path 1 under the propulsive force provided by the linear motor drive. When the elevator is to be stopped on reaching the desired floor, braking is applied by the linear motor, and the release mechanism 15 goes into the no-load condition. This causes the left and right wedges 14 to be pressed against the guide rail 2 by means of the wedge guides 13 and the action of the resilient support 12, thereby performing braking due to the frictional force. This stops the cage 3 at the desired floor and holds the cage 3 in position. In this way, running and stopping of the cage 3 at the desired floor are performed under ordinary conditions. If some malfunction occurs so that the cage 3 exceeds the rated speed, the excess speed of the cage 3 is detected by speed governor 20, causing the left and right wedges 14 of the wedge type braking device 10 to be pulled between the wedge guides 13 and the guide rail 2. The wedges 14 are thus jammed between the wedge guides 13 and the guide rail 2, generating a powerful braking force, which reliably performs an emergency stop of the cage 3. If the cage 3 falls with excessive speed due to free fall by diminution or loss of the propulsive force of the linear motor because of a power cut-off or some fault during running of the cage 3, the balance between the spring force of the balancing spring 40 and the inertial weight of the wedges 14 and rod members 37b is lost, with the result that the wedges 14 are pushed in between the wedge guides 13 and guide rail 2. Wedges 14 thereby become jammed between the wedge guides 13 and the guide rail 2, generating a powerful braking force, resulting in reliable emergency stopping of the cage. Thus safety is guaranteed in that if, during running of the cage 3, cage 3 starts to run with abnormal excess speed or free fall, due to power cut or to some malfunction, at least one the speed governor 20 and balancing spring 40 acts to cause wedges 14 to be reliably jammed in between wedge guides 13 and guide rail 2, thereby generating a powerful braking force and reliably performing emergency stopping of the cage 3. The weight of the wedge braking devices 10, is reduced, in comparison with the prior art braking devices. The wedge braking device according to the present invention can be applied to elevators of other types such as the traction elevator.

Claims: An elevator braking device, wherein a cage (3) moves along a guide rail (2), comprising: a wedge braking means (10) mounted on said cage (3); a speed governor means (20); and a linking means for linking said wedge braking means (10) and said speed governor means (20); said wedge braking means (10) including, a resilient support member (12), a wedge guide means (13), supported by said resilient support member (12), a wedge member (14), provided between said guide rail (2) and said wedge guide means (13), to be pressed against said guide rail (2) by a biasing force generated by said resilient support member (12), thereby stopping said cage (3) by means of a first frictional force between said guide rail (2) and said wedge member (14), a releasing means for releasing said resilient support member (12) such that said wedge member (14) separates from said guide rail (2) when a releasing force is generated; and said linking means being linked such that the speed governor (20) pulls up said wedge members (14) along said wedge guide means (13) when said speed governor means (20) detects that a speed of said cage exceeds a rated speed, thereby pressing said wedge member (14) against said guide rail (2) and effecting an emergency stop of said cage (3) by means of a second frictional force between said guide rail and said wedge member (14), wherein: said wedge braking means (10) includes, a balancing spring means (40) provided under said wedge member (14) for supporting said wedge member (14), a spring force thereof being set such that said spring force balances the weight of said wedge member (14) so that said wedge member (14) is supported in a positiion with a suitable clearance with respect to said guide rail (2), characterised in that said speed governer means (20) is provided on said cage for detecting a running speed of said cage (3), said balancing spring (40) is arranged to push up said wedge member (14) along said wedge guide means (13) when the balance between said weight of said wedge member (14) and said spring force (40) is lost by excessively rapid descent of said cage (3), thereby pressing said wedge member (14) against said guide rail (2) and effecting an emergency stop of said cage (3) by means of a third frictional force between said guide rail (2) and said wedge member (14). An elevator braking device according to claim 1, wherein: said elevator is a self propelled elevator. An elevator braking device according to claim 2, wherein said cage (3) moves along said guide rail (2) under a propulsive force generated by a linear motor. An elevator braking device according to any preceding claim wherein: said wedge braking means (10) includes a frame (11) mounted on the bottom of said cage (3); said resilient support member (12) includes a plate spring with a U-shaped cross-section which covers said guide rail (2) inside thereof, said plate spring being mounted on said frame (11); a pair of said wedge guide means (13) include a pair of blocks, each retained on the resilient support member (12) by one of a pair of side plate portions (12a) received in a groove formed in said wedge guide means (13) and having a wedge guide face (13a) inclined with respect to the rail (2) to converge inward and upward; a pair of said wedge members (14) having a trapezoidal shape, each inside face thereof being vertical and parallel with said guide rail (2), and each of the outside faces thereof being inclined in parallel with an associated one of said inclined faces of said wedge guide means (13); and said releasing means including an hydraulic cylinder (19), which, when pressurised oil is supplied to said hydraulic cylinder (19) pushes open the two side plate portions (12a) of said plate spring to release said resilient support member (12). An elevator braking device according to claim 4, wherein: said balancing spring means includes a pair of compression coil springs (10), each of which supports one of said wedge members (14), said spring force of each of said compression coil springs being in balance with the weight of the supported said wedge member. An elevator braking device according to claim 4, wherein: said linking means includes a pair of lifting means (37) connected between said speed governor means (20) and said wedge members (14), each of said lifting means (37) functioning such that only a lifting force from said speed governor means (20) is transmitted to said wedge members (14) and a pushing force from one of said wedge members (14) is not transmitted to said speed governor means (20). An elevator braking device according to claim 6, wherein: each of said lifting means (37) includes a tubular member (37a) and a rod member (37b); a top end of said tubular member (37a) is connected to said speed governor means (20); a bottom end of said rod member (37b) is connected to said wedge member (14); and a top end of said rod member (37b) is inserted in a bottom end of said tubular member (37a) and slides inside said tubular member (37a) such that only a lifting force from said tubular member (37a) is transmitted to said rod member (37b) and a pushing force from said rod member (37b) is not transmitted to said tubular member (37a).

Inventors: OSADA AKIRA, OSADA, AKIRA, OSADA, AKIRA, C/O INTELLECTUAL PROPERTY DIVISION
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1993
Main classification: B66B5
IPC codes: B66B9, B66B5, B66B11