CATCHING AND BRAKING DEVICE FOR LIFTS

Abstract: A clamping or braking device for lifts having a rotatable input element (15') which is directly or indirectly actuated by an actuating member (12') extending along the trajectory of the lift car (11') or the like. The input element (15') is directly or indirectly connected with a centrifugal governor (23'), which in response to the input element exceeding a predetermined angular speed connects the latter element with an actuating screw (29'), which thus is caused to rotate by the input element (15'). A flanged nut (32') is disposed on said element. The flank of the flanged nut (32') abuts against a spring means (34') acting against a brake-disc (33') which in braking situations directly or indirectly counteracts or arrests the rotation of the input element (15') and thus brakes the lift car or the like. In accordance with the invention, the flanged nut (32') is prevented from rotating by the provision in the device of a blocking device (40', 41') arranged to determine the length of travel of said flanged nut (32') along the actuating screw (29') before the flanged nut (32') is released and continued tightening of the spring mechanism (34') ceases.

Description: CATCHING AND BRAKING DEVICE FOR LIFTS The present invention relates to a lift brake or a catching or clamping device to be used in lifts, stair lifts, mobile elevating work platforms or similar hoist¬ ing mechanisms. However, the invention is applicable particularly to catching means or lift brakes intended for elevator devices known as stair lifts that may be used to move persons confined to wheel-chairs along a sloping plane between two different landings, usually a staircase. Like all other lifts such elevating devices must be equipped with an emergency or drop brake or clamping device stopping the descending movement of the carrying platform, working platform or lift car, should the speed of the descending movement for some reason increase to a value exceeding a certain limit value (for instance 0.3 m/s). This drop brake or clamping device is mounted on the carrying platform or lift car and accompanies the latter in the ascending or descending movements, and it is in¬ tended to cooperate with a guide or support rail along which the lift car, carrying platform or working platform moves. According to the present Swedish standards for elevators the device should be a mechanical or electro¬ mechanical device interrupting the descending movement within an extremely brief distance and safety securing the lift car or carrying or working platform to the lift guide or guides. In prior-art lifts various types of mechanical brakes are used for this purpose as a drop brake or clamping device, said mechanical brakes comprising a stationary brake part and a cooperating movable brake part. The movable brake part is rotatable and connected to a centrifugal governor and arranged to be moved towards and away from the stationary brake part. The movable brake part is biased in the direction towards the stationary one, usually with the aid of a spring unit, typically a cup spring assembly. The unit also comprises a tightening device which in its normal con¬ dition prevents the spring unit from urging the movable brake part against the stationary one when the speed of the ascending movement is less than a certain limit value. The tightening device comprises a centrifugal governor which is used to release the tightening device, whereby the brake will be activated, should the speed of movement become excessively high and in excess of the set limit value. Examples of such prior-art devices are described for instance in SE-B-433,485, SE-B-302,675, SE- B-308,785, SE-B-362,859, DE-A-27 53 079, GB-A-l,555621 and US-A-4,531,617. A feature common to all these devices is that in order to reset the lift brake to its normal condition active measures need to be taken by servicing personnel, and that the lift car or carrying platform is maintained in its braked or stopped position until the lift brake is reset to its normal condition. In addition, the standards for elevators specify that it must be impossible to dis¬ connect and reset the lift brake in any other way than by allowing the lift car or support platform to drift to a higher level along the elevator guide or guides. Because active measures and servicing personnel are required the prior-art structures are not particularly advantageous but rather a hindrance, particularly in the case of ele¬ vators designed for persons that are handicapped or con¬ fined to wheel-chairs. A serious drawback found in prior-art structures thus is that they force handicapped persons or persons confined to wheel-chairs to remain in the lift car or on the carrying platform and that for the entire time required to effect reset of the lift brake the lift can¬ not be used to transport these persons to an ujJper or lower landing. Another disadvantage inherent in prior- art lift brakes is that they stop the downwards movement abruptly, often accompanied by a heavy jerk with result¬ ing risks for personal injuries. The prior-art clamping devices or lift brakes thus suffer from the disadvantage that upon release in response to excess speed they lead to the unacceptable consequence of trapping the lift passengers inside the lift car, on the carrying platform or the working plat¬ form without the possibility of getting out by them¬ selves. One consequence of this disadvantage may be that trapped persons, if unlucky, may have to wait for a con¬ siderable time, perhaps for hours, for external assis¬ tance. Such delays may be fatal, should the accident occur for instance in connection with fire, since under such circumstances elevator shafts may act as chimneys. One object of the present invention thus is to eli¬ minate the deficiencies of prior-art elevator devices. A particular object is to provide a lift brake which, while arresting too rapid descending movements, after initia¬ tion of the braking process allows downward movements at a considerably lower speed, causing the carrying platform or lift car to move slowly down to an unloading position. The object of the subject invention thus is to fur¬ ther develop the braking device described in the intro¬ duction, to effect braking in a manner that is more com- fortable to the passengers, and to not block the lift car, the carrying platform or working platform complete¬ ly. The device should be of a nature making it acceptable as a deviation from the present Swedish standards for elevators because the lift brake functions both to softly arrest uncontrolled drop movements as well as to allow careful and controlled ascending movements at a reduced speed. Consequently, the device should be able to ensure that the lift car and the like, following activation of the lift brake or clamping device, moves slowly down- wards, along the guide or the guides at a predetermined low speed, until the lift reaches its lowest stop level or the bottom landing where the passengers may step out of the lift. The device should also be able to brake the rapid descending movement softly upon release, and to ensure that the subsequent descending movement is suffi¬ ciently slow not to expose the passengers to the discom- fort of sudden and abrupt stops during the initial stage of the braking, and that also the discomfort at the final stop becomes as insignificant as possible. These and other objects of the invention are obtain¬ ed with a lift brake designed in accordance with the characteristics of claim 1. The dependent claims define particularly preferred embodiments. In summary, the invention resides in a clamping or catching device designed for lifts and having a rotatable input member which is actuated directly or indirectly by an actuating member extending along the trajectory of the lift car or the like. The input member is directly or indirectly connected to a centrifugal governor which is arranged, when a predetermined angular speed of the input member is exceeded, to interconnect said input member with an actuating screw or worm which is thus caused to rotate. The actuating screw has a flanged nut mounted thereon. The flanged nut flank abuts against a spring unit acting against a braking disc which upon braking directly or indirectly counteracts or arrests the rota- tion of the input member, thus braking the lift car or the like. In accordance with the invention, a locking means in the device prevents the flanged nut from rotat¬ ing and is arranged to determine the distance of travel of the flanged nut along the actuating screw before the flanged nut is released and continued increase of the spring unit spring force ceases. The invention will be described in closer detail in the following with reference to the accompanying drawings illustrating two embodiments and wherein: Fig. 1 is an axial cross-sectional view through a preferred embodiment of the invention, Fig. 2 is a sectional view along line II-II of Fig. 1, Fig. 3 is a similar cross-sectional view as Fig. 1 but shows the device in the activated braking position, and Fig. 4 is an axial sectional view through another embodiment of a lift brake or catching device in accor¬ dance with the invention. Fig. 1 illustrates a guide or supporting rail 10 along which a lift car, a mobile elevating work platform or a carrying platform 11 (only an edge portion thereof is shown) may be displaced in the conventional manner. The guide or support rail may extend vertically in the case of a conventional elevator or be inclined in the case of for instance a stair lift. A rack 12 is mounted on the guide or support rail. The counter-acting roller 13 is arranged for free rotational movement about a shaft journal 14 which in turn is connected to the lift car, the working platform or carrying platform 11. A gear- wheel 15 travels along the rack. A corresponding device may be provided on the opposite side of the lift car 11 or on each guide or support rail. The gear-wheel 15 forms an input member in the lift brake in accordance with the invention. Instead of a rack secured to the stationary support rail 10 it is possible to use a chain arranged in paral¬ lel with the support rail, said chain being stationary and sufficiently strong to absorb the entire load from a loaded lift car, should the lift brake be released. When a chain is used, the input member could be in the shape of sprocket wheel. The rack could also be replaced by a wire which in this case is allowed to run a suitable num¬ ber of turns about a cable-drum, the latter in this case replacing the gear-wheel 15 and serving as the input mem- ber. At the outer end of the shaft journal 14 the latter is rigidly interconnected with a frame plate 16, the lat- ter thus being stationary relatively to the shaft journal 14 and thus relatively to the lift car etc. 11. A second shaft journal 17 is rigidly connected to the frame plate and is used as the shaft journal supporting the gear- wheel 15. The latter is rigidly connected to a second gear-wheel 18. A sliding sleeve 19 is slipped onto the shaft journal 17, the gear-wheels 15 and 18 thus being mounted on the shaft journal 17 for free rotation thereon via the sliding sleeve 19. The gear-wheel 18 in turn engages a further gear¬ wheel 20 which via a sleeve 21 is rigidly connected to the hub 22 of a centrifugal governor 23. The sleeve 21 and thus the gear-wheel 20 and the hub 22 are rotatably mounted on the shaft journal 14. A sleeve bearing 24 may be provided intermediate the sleeve 21 and the shaft pivot 14. A spacer sleeve 25 is inserted between the frame plate 16 and the hub 22 to hold the latter in its intended position along the shaft journal 14. A ratchet wheel 26 forming part of the centrifugal governor 22 is rotatably mounted on the sleeve 21. A sleeve bearing 50 may be inserted between the ratchet wheel 26 and the sleeve 21. The ratchet wheel is rigidly connected to yet another gear-wheel 27 which thus also is arranged to rotate about the sleeve 21. The gear-wheel 27 engages a gear-wheel 28, the latter being rotatably mounted on the shaft journal 17 and connected to a sleeve 29 so as to be non-rotatable but displaceable relatively thereto ( for instance by means of engaging splines formed on respectively the sleeve and the gear-wheel) . The sleeve 29 is mounted on the shaft journal 17 and one or several sleeve bearings 30 may be inserted between the sleeve 29 and the shaft journal 17. The sleeve 29 extends towards the frame plate 16 and is formed with external threads 31 at its end closest to the frame plate. A flanged nut 32 is screwed onto the threads 31 so as to move along the latter when the clamp¬ ing device or lift brake is activated. Cup discs 34 are held between said flanged nut and a brake-disc 33. A stop nut 35 is inserted at the end of the sleeve 29 closest to the frame plate 16. The brake-disc 33 is non-rotatable but displaceable relatively to the shaft journal 17. This is achieved by means of a guide pin 36 which is rigidly secured on the frame plate 16 and which projects into a through-hole 37 in the brake-disc 33. The brake-disc is urged by the cup springs 34 against a brake lining 38 applied to one of the lateral faces of the gear-wheel 28. To the opposite face of said wheel is applied a second brake lining 39 which is forced against the lateral face of the gear¬ wheel 18 when the brakes are applied. During normal operational conditions of the lift, the flanged nut 32 is prevented from rotating relative¬ ly to frame plate 16. This is achieved by means of a stop bolt 40, a non- hreaded end of which projects into an aperture 41 formed in the flange of the flanged nut 32. The stop bolt 40 may be screwed to various setting posi- tions with the aid of a lock nut 42. The length by which the stop bolt is screwed into the aperture determines the degree of compression of the cup springs 34 and thus the normal braking of the lift brake or clamping device under normal operational condi- tions. Should the lift car come loose or for some other reasons start moving downwards along the guide or slide track 10 under uncontrolled conditions and should the predetermined value of the allowed speed of this movement be exceeded, the gear-wheel 15 will start rotating at an increasingly higher speed. Via the gear-wheel 20 and the sleeve 21 the hub 22 of the centrifugal governor there¬ fore will also be rotated at an increasingly higher speed. When the speed reaches the set limit value the catches 43 of the centrifugal governor will pivot into engagement with the ratchet wheel 26 in response to the centripetal force. The ratchet wheel 26 is connected to the ratchet wheel 27 which thus sets the gear-wheel 28 and the sleeve 29 in a rotary motion, should a locking engagement be established between the catches 43 and the ratchet wheel 26. Since the stop bolt 40 projects into the aperture 41 formed in the flange 32, preventing the flanged nut 32 from rotating, the threads 31 on the sleeve 29 will urge the nut 32 in the direction towards the cup springs 34, whereby the latter will be compressed and the brake be activated. The braking force thus increases gradually during the very first phase of the braking, until the flanged nut 32 has been displaced sufficiently far away from the frame plate 16 to cause disengagement of the other threaded end from the stop bolt 40 and the aperture 41. In this position, the cup springs have been compress¬ ed to the degree determined by the set position of the stop bolt 40. Upon attainment of the disengagement of the set bolt from the flanged nut 32 the lift car 11 is allowed to slide slowly along the guide or support rail 10. The speed is determined by the degree of compression of the cup springs 34 of the brake mechanism formed by the brake-disc 33, the brake linings 38, 39 and the gear¬ wheels 18 and 28. Fig. 2 is a schematically sectional view taken along line II-II of Fig. 1 and showing a preferred structure of the centrifugal governor and its catches 43. The lat¬ ter are formed with a hook 44 at one of its ends and with a weight 45 at the other. The hook catches are pivotally mounted on shaft journals 46 formed on one of the lateral faces of the gear-wheel 27. Tension springs 47 are held between a spring seat 48 formed on the catch 43 and a spring seat 49 formed on the gear-wheel 27. Consequently, the catches 43 are spring-biased clockwise as seen in Fig. 2, keeping the hooked end 44 of the catches out of engagement with the ratchet wheel 26 during normal opera¬ tional conditions. When the rotational speed of the gear¬ wheel 27 increases the catches will be pivoted counter- clockwise, against the action of the springs 47, and when the rotational speed becomes excessively high the hook ends 44 of the catches will engage the ratchet wheel 26. The engagement cannot be released before interruption of the compression of the cup springs 34 as a consequence of the flanged nut 32 having been unscrewed to its original position and the stop bolt 40 again having been caused to engage the aperture 41 in the flanged nut. This reset of the clamping device may be performed only by servicing personnel. Since the lift car, the work platform or car¬ rying platform has slid to its lower stop position or the bottom landing the passengers may step out of the lift device without having to wait for the appearance of ser¬ vicing personnel. The embodiment illustrated in Fig. 1 is the prefer¬ red one, since the gear ratio between the gear-wheel pair 18, 20 increases the angular speed of the gear-wheel 27 in comparison with the angular speed of the gear-wheel 15. In addition, also the angular speed of the sleeve 29 increases owing to the gear ratio between the gear-wheels 27 and 28, in consequence of which the tightening of the flanged nut 32 against the cup springs 32 will occur rapidly. Fig. 4 illustrates another embodiment lacking the supplementary gearing. In this drawing figure the same numeral references have been used as previously with the addition of the prime sign, to denote components corresponding to those of the embodiment according to Figs 1-3. In accordance with this embodiment the gear-wheel 15' directly engages the rack 12', whereby it will roll along said rack when the lift moves up and down along the guide 10'. The gear-wheel 15' is freely rotatable about the actuating sleeve 29 ' . The catches 43 ' are mounted on one of the flanks of the gear-wheel 15' and are mounted in a manner identical to that according to the previously described embodiment of the invention. When the allowable maximum angular speed is exceeded the catches 43' will engage the ratchet wheel 26' , thus causing the actuating sleeve 29' to rotate. Accordingly, the flanged nut 32' will be moved along the actuating sleeve 29' as a conse- quence of the flanged nut 32' being held stationary by the set screw 40'. As the flanged nut 32', being in thread engagement with the actuating sleeve 29' moves along the sleeve the cup springs 34 are compressed against the brake-disc 33' which is arranged for axial displacement on the actuating sleeve 29' and thus being displaceable along said sleeve. The brake lining 38' disposed on the opposite face of the brake-disc 33' is pressed against the flank of the gear-wheel 15', thus initiating brake action. The intensity of braking power is determined by the length of penetration of the flanged nut 32' in the direction towards the cup springs 34' . This in turn is determined by the length by which the stop bolt 40' is screwed into the aperture 41' of the flanged nut 32' when the clamping device assumes its normal position and the flanged nut 32' assumes its extreme end position to the right as seen in Fig. 4. As soon as the flanged nut goes free of the stop bolt 40' , continued compression of the cup springs 34' is interrupted, allowing the lift to slowly slide downwards at a predetermined speed determin¬ ed by the set braking power. The braking power may also be set to ensure locking of the lift. Unlocking may be achieved by screwing the stop bolt 40' to the right as seen in Fig. 4 and by screwing the flanged nut 32' in the reversed direction, back to the original position. The flanged nut is then set in a position allowing the stop bolt 40' to be inserted into the aperture 41' . Finally, the stop bolt 40' is screwed back to its correct position, i.e. to the position required to produce the predetermined braking power when the catching device function is initiated and the drop of the lift car is to be arrested in order to produce a slow sliding movement thereof to the bottom landing or the lower stop level. Fig. 4 shows that the various components of the catching device are mounted directly on a beam in the lift car 11' or the like and also that there is no cor¬ respondence to the plate 16. The invention should not regarded as limited to the embodiments shown. In accordance with these embodiments the centrifugal governor is formed with tension springs conceived to maintain the catches in their normal posi¬ tions. Other types of springs could be used for this pur¬ pose. Other centrifugal governor designs could also be used. In addition, the speed sensing means of the device need not be a gear rack extending along the lift trajec- tory and a gear-wheel engaging therewith. It is equally possible to use a stationary wire or chain running in several turns over a wire or chain drum on the lift car in order both to allow the speed of movement to be sensed and to allow load absorption upon braking, should a situation of excess speed arise and the clamping device be released. A further modification of the described embodiments may involve replacing the stop bolt 40 and the aperture 41 by a rail engaging a groove in the flanged nut and formed with a recess to release the flanged nut when the latter has achieved the axial position along the threaded sleeve or actuating screw 29, 29' required to produce the intended release braking power. Also other types of braking power regulating devices are possible, as long as the inventive idea of the invention is respected, i.e. restriction of the braking power to a predetermined maximum value, ensuring that the lift car, after release of the brake, may slide slowly down to a lower stop level or to the bottom landing.

Claims: CLAIMS 1. A clamping or braking device for lifts (11), comprising a braking device (29-41) which is operative¬ ly connected to and may be activated by a speed sensor (12, 15, 18-23) designed to sense the speed of the moving lift, and which is equipped with brake parts (32, 33) arranged for movement towards and away from one another, said parts being yieldingly biased for movement towards one another against the action of a brake release device (23) which is controlled by the speed sensor (12, 15, 18-23) and which is arranged, in response to said sensor, to allow the brake parts (32, 33) to interengage, c h a r a c t e r i s e d in that the brake release device (23) comprises a braking power regulator (23, 29, 32-34) to regulate the braking power of said braking device (29-41) after release of said braking device. 2. A device as claimed in claim 1, the brake parts (32, 33) of which are biased for movement towards one another by means of a spring mechanism (34), which is adjustable in order to determine the braking power of the braking device, c h a r a c t e r i s e d in that braking power regulator (23, 29, 32-34) comprises an actuating screw (29) and a flanged nut (32), the latter being dis¬ placeable along the actuating screw to regulate the brak¬ ing power determined by the spring mechanism (34). 3. A device as claimed in claim 2, c h a r a c ¬ t e r i s e d in that the braking power regulator (23, 29, 32-34) comprises a blocking means (40, 41), which is connected to the flanged nut (34) in order to secure the latter during the rotation of the actuating screw (29) and which is arranged to release the flanged nut in response to obtainment of a predetermined braking power. 4. A device as claimed in claim 3, c h a r a c ¬ t e r i s e d in that the blocking means (40, 41) com¬ prises a blocking member (40), which may be set in dif- ferent positions relatively to the actuating screw (29 ) to release the flanged nut (32) in response to obtainment of the predetermined braking power. 5. A device as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that speed sensor (12, 15, 18-23) comprises a centrifugal governor (23). 6. A device as claimed in any one of claims 2-5, c h a r a c t e r i s e d in that the speed sensor (12, 15, 18-23) is connected to the actuating screw (29) via a gear mechanism (18, 20, 27, 28). 7. A device as claimed in any one of claims 2-6, c h a r a c t e r i s e d in that it comprises a rotatable input element (15, 15' ), which is in direct or indirect drive engagement with an actuating means (12, 12' ), which extends along the trajectory of the lift car (11, 11' ) or the like and which is connected to the centrifugal gover¬ nor (23, 23' ), said governor arranged, when a predeter¬ mined angular speed of the input element (15, 15') is exceeded, the connect said element with the actuating screw (29, 29 ' ) in order to cause said screw to turn for the purpose of displacing the flanged nut (32, 32' ) along the actuating screw and thus initiating an increasing braking power of the braking device, and in that the blocking means (40, 41, 40', 41' ) is arranged to release the flanged nut (32, 32' ) upon attainment of a predeter¬ mined braking force in order to interrupt further tight¬ ening of the spring mechanism (34, 34'). 8. A device as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the speed sen- sor (12, 15, 18-23) comprises a gear rack (12) extending along the trajectory of the lift, and a gear-wheel (15) engaging said rack and being connected to the braking power governor (23, 29, 32-34) via a gear mechanism (18, 20).

Inventors: SVEDMAN ROLF VILHELM, SVEDMAN, ROLF, VILHELM
Applicants: SVEDMAN ROLF VILHELM, SVEDMAN, ROLF, VILHELM
Application year: 1996
Main classification: B66B5
IPC codes: B66B5, B66D5