FALETO LUCIANO (IT)
| US1641957A | 1927-09-13 | |||
| US2270441A | 1942-01-20 |
| Claims 1. An elevator comprising a cage (2) and a balancing element (3) slidable on vertical guides, connected with each other by suspension elongated elements (9) driven by at least a driving pulley, c h a ra c te riz e d by th e fa c t th a t said cage (2) and said balancing element (3) are further connected with each other by monitoring elongated elements (4), at least partially wound on transmission elements (5), arranged in order to switch status of control devices (6, 7) when the tension within said elements (4) is outside a predetermined range, the switching of the status of said control device (6, 7) stopping the operation of said elevator. 2. The elevator according claim 1, wherein said elongated elements (4) are connected at a first end to said cage (2) and at the other end to said balancing element (3). 3. The elevator according claim 1, wherein said internal tension is measured by dynamometric devices. 4. The elevator according claim 3, wherein said dynamometric devices are springs (8) connected to said control devices (7). 5. The elevator according claim 1, wherein said control devices (6, 7) are safety- switches. 6. The elevator according to one or more of the preceding claims, wherein said transmission elements (5) are movable pulleys under the action of said tension within said elongated element (4). 7. The elevator according to claim 6, wherein said pulleys are movable along a vertical guide. 8. The elevator according to claim 6, wherein said pulleys and said controlling devices (6) are supported by an automatic compensator device (18) able to constrain the movement of said control devices (6) to the movement of said pulleys when they move due to the permanent elongation in said elongated elements (4) and to stop the movement of said control devices (6) when said pulleys are dragged by said internal tension when the tension is out of said predetermined range. 9. The elevator according to the preceding claim, wherein said automatic compensator device (18) comprises at least a pair of arms (11, 12) hinged with each other each at its first end and one of said pair hinged at its second end to said pulley and the other of said pair hinged at its second end to a fixed position of the elevator shaft, said pair being further connected to supporting elastic elements (13) and provided with devices (14) adapted to prevent the retrograde motion thereof. |
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The present invention relates to a safety device for lift plants having a balancing weight, and particularly to a safety device able to control the occurred blocking of the lift and/ or the balancing weight in order to operate the stop of the lift plant.
One of the issues often being faced during the design of electric lifts with traction pulley is a suitable dimensioning of the friction features between the traction pulley and the Hfting elongated elements which have to be driven by the same pulley, so as to assure the right movement of the cage and the counterweight coupled thereto. The friction, for example, has to be enough to assure the driving of the Hfting elongated elements under the all loading conditions, but the risk of Mting the cage, when the counterweight is blocked during its down stroke, has also to be avoided. Furthermore, it has to be avoided Kfting the counterweight even in the case wherein the down stroke of the cage is obstructed for some reason. The Kfting elongated elements can be ropes or flat belts or grooved belts or timing belts, but hereinafter for sake of description simplicity the lifting elongated elements will be referred as "lifting ropes".
One of the known technical solutions consists in reducing the maximum attainable friction between the drive pulley and the lifting ropes. Such solution, on the other hands, has drawbacks since there would be reasons, such as a change in the friction characteristics, or the geometric modification of the contact surfaces between the pulley grooves and the ropes caused by wear or other phenomenon, such as to cause hfting of the not blocked element for a length enough to endanger people or things in case of subsequent fall thereof. Another known technical solution consists in limiting the maximum attainable torque of the motor so as not to aEow to lift one of the two elements if it is not at least partially balanced by the other element, such as, for example, when the down stroke is obstructed. Even in this case some reasons, such as for example a variation of the motor supply voltage or a failure of the torque control device, etc., may occur which could cause the lifting capability to keep lifting the not blocked element so as to endanger people or things due to the subsequent sudden fall, if the undesired lifting has allowed it to reach enough height.
Main object of the present invention is therefore to provide for carrying out of a safety device within a lift plant provided with a cage and a upright sKding counterweight, which avoids lifting of one of these two elements whenever the other element is blocked or its down stroke is obstructed, for example when it leans on the lift pit shock absorbers, or for any other reason not clearly identifiable, thus also helping in making the friction characteristic dimensioning less critical in these kind of lifts.
These problems are solved by a safety device as claimed i the characterizing part of the independent claim 1. Preferred embodiments are recited in the dependent claims.
A detailed description according to a preferred embodiment of the present invention, with reference to the annexed drawings wherein like or corresponding elements are indicated by the same reference numerals and wherein:
fig. 1 is a lateral cross-sectional view of a lift plant according to two preferred embodiments of the present invention,
fig. 2 is a perspective view of a third embodiment of the traction control device according to the present invention,
fig. 3 shows the control device in fig. 2 installed on a lift plant with balancing weight, and fig. 4 is a perspective view of a simplified modification of the traction control device according to the present invention.
The safety contacts can be: electric safety contacts, electric safety circuits, electronic safety circuits or equivalent electronic safety devices, which hereinafter for sake of description simplicity will be referred as "safety contacts".
With reference now to fig. 1, a first preferred embodiment according to the present invention consists of a electric safety device 7 comprising an electric safety contact, or other electronic safety device. Said electric safety device 7 further comprises one or more springs 8 for tightening the suspension ropes 9: in all the cases in which a loosening of the tension limiting ropes 4 on the side of the cage 2 or counterweight or balancing weight 3 the actuation of the safety device 7 causes the lift stop.
With reference now to fig. 1, a second preferred embodiment according to the present invention is shown consisting in an electric safety device 6 able to monitor the vertical position of a pulley 5, driven in a vertical plane a placed at the lower end of the pit 10 in the lift shaft 1, around which the rope 9, whose ends are fixed on one side to the cage 2 and on the other side to the counterweight or balancing weight 3, is wrapped. In a case in which one of the two upright sHding elements, i.e. the cage 2 and the counterweight or balancing weight 3, stops its movement downwards whilst the other element keeps going upwards, the pulley 5 is raised upwards and actuates the safety contact 6, or equivalent electronic device, which stops the plant operation and prevents any other raising.
With reference now to fig. 2, a third preferred embodiment consists of a pulley 5 which is supported by a tension limiting device 18 constituted by a frame 11 having an approximatively vertical movement, in turn movable in respect of a second frame 12 the downwards vertical movement of which is limited by some springs 13 which keeps it hooked to the frame 11 of the pulley 5. The upwards movement is instead limited by a ratchet device 14, or freewheel, which allows the descent of the frame 12 but does not allow the ascent thereof, or allows it in a very limited amount. In such manner the vertical position of the control contact 6 of the pulley 5 fits automatically to the elongation of the tension limiting or monitoring rope 4 connecting the cage 2 and the counterweight or balancing weight 3. As shown in fig. 3, the mount point of the monitoring rope 4 on the cage 2 is provided with a compression spring 15 or equivalent device and a safety contact 16. In a case in which the rope 4 is loosened or broken the spring 15 actuates the safety contact 16 and stops the lift. The frame 12 carrying the stop contact 6 actuates a safety control device 17 when it leans on the fixed stop at the pit. The safety control device 17 causes the stop of the lift at the first service stop and the lift can be normally operated only after the intervention of an authorized and qualified operator, which provides for suitably adjusting the length of the monitoring rope 4.
As shown in fig. 4, the tension limiting device 18 according to the present invention can be formed also in an easier manner by eliminating the springs 13 and the ratchet device 14 from the embodiment in fig. 2, obtaining, on the other hands, a less accurate control of the tension on the tension limiting rope 4.