Braking device for lifting means, such as lifts or goods lifts

Abstract: Braking device for lifting means, such as lifts or goods lifts, comprising two braking means (1,3), acting simul­ taneously. One of said braking means (1) is an asynchronous alter­ nate current motor, with one speed, supplied with direct cur­ rent. The other braking means (3) is an electromagnetic brake which exercises an action of intemittent intervention. The asynchronous motor (1) is connected to the manoeuvring winch (2) of the lift (6) by the electromagnetic brake (3).

Description: The present invention refers to a braking device for lifting means, such as lifts or goods lifts. More in particular, the present invention refers to a braking device for lifting means, such as lifts or goods lifts normally used in blocks of flats of co-ownership, buildings assigned to dwelling-houses and/or offices and similar. A braking device comprising two coupled braking systems is disclosed in DE-C-1007041. US-A-4232768 discloses an improved brake for winches comprising a first main brake, a second emergency brake, first means for actuating the first brake, second means for actuating the second brake in emergency and means for delaying operation of the second means relating to the first means to apply first and second braking force in sequence in an emergency. An electromagnetic brake is described in DE-A-3003148. Jaw brakes are well known and generally used in the lifting means. These types of brakes, while corresponding to all safety guarantees, is not very precise in the sense that the stop of the elevator cars at the floors takes place with a certain approximation, leaving visible differences in level between the openings of the cars and those of the floors. This is due to the fact that the intervention and action of the jaw brakes, at each stop request, are not always constant and therefore the stop of the cars takes place slightly before or after the times foreseen, so that the floor of the cars is never perfectly aligned with the floor of the stop levels. Due to this imperfect operation, it very often happens that, during entry or exit of the lifts, with the floor not level with respect to that of the stop levels, users trip, injuring themselves. Another problem is due to the fact that lifts equipped with jaw brakes, even if cheaper to build than other braking means, like, for example, two-speed direct current motors or two-pole motors, are subject to frequent maintenance, to keep the imperfect stopping position of the cars within restricted limits and check the wear state of the braking jaws. To overcome these problems various solutions have been proposed; in particular, tests have been made provoking braking by inserting direct current in the asynchronous alternate current lifting motors. However, since the braking effect depends on the square of the speed of the motor, its efficiency rapidly decreased, becoming practically nil the moment the lifts had effectively to stop. Other attempts were made using intermittent braking means acting on the standard jaws, but results were not positive as there was no improvement in either the precision of the stopping of the lifts or the wear on the jaws. The object of the present invention is to eliminate the abovementioned problems. According to the present invention, this object is achieved by the features in the characterizing part of claim 1. Particular embodiments of the invention are set forth in dependent claims 2 to 3. Particularly, the subject matter of the present invention is a lift comprising an asynchronous alternate current motor, an electromagnetic braking device, provided with braking jaws, a manoeuvring winch comprising a traction pulley of cables supporting an elevator car, at one end, and a counterweight, at the other end, and means for controlling the braking device, characterized in that the means for controlling the braking device consists in supplying the asynchronous alternate current motor with direct current and, simultaneously, the electromagnetic braking device with sequential pulses intermittently acting on the jaws. The asynchronous alternate current motor, with one speed, supplied with direct currents is the first braking system. The electromagnetic braking device with intermittent action on the jaws is the second braking system. The first braking system exercises a braking action at the first stage, which then decreases according to the square of the speed, and the second braking system acts intermittently and with variable braking force. The braking device of the present invention permits us to obtain, in first place, a more regular, precise braking effect since the two coupled braking systems, with simultaneous action, intervene on both the traction motor and on the braking jaws of traditional type. Moreover, the braking action exercised on the motor is of continuous type, while that exercised on the jaws is of intermittent type or with variable force. Through the use of the braking device of the present invention, the following advantages are obtained: the double simultaneous braking action consents a better regulation of the system and the stop of the elevator cars takes place in the required time and space; the jaws of the traditional braking system are subject to less wear, permitting advantageous savings on spare parts and maintenance; the double coupled braking system gives greater safety guarantees to the lifting means. The constructive and operative characteristics or the braking device for lifting means, such as lifts or goods lifts, of the present invention will be easier to understand from the following detailed description, in which reference is made to the attached figure 1, which shows a schematic view of the cross-section of a lifting plant equipped with the braking device of the present invention in a form of construction given by way of illustration and example, but not binding. With reference to the figure, the braking device for lifting means, like lifts or goods lifts, of the present invention, comprises essentially an asynchronous alternate current motor 1, with one speed, connected to the manoeuvring winch 2 by an electromagnetic brake 3. The manoeuvring winch 2 comprises the traction pulley 4 of the cables 5, which support, at one end, elevator car 6 and, at the other end, is suspended the counterweight 7. In operation, when a stop is booked from elevator car 6 or from any floor 8, by means of the traditional push-button strips 9 or 9', selector switch 10 presets and automatically intervenes to supply the various parts with the controls necessary to make the manoeuvre. In particular, said controls are sent to the braking device sufficiently in advance to guarantee the slowing down and stopping of car 6 exactly in front of space 11, corresponding to the door of each floor 8, so that the level 12 of its floor is perfectly aligned with that or the levels 13. According to the device of the present invention, the braking control is sent simultaneously to the asynchronous alternate current motor 1 and the electromagnetic brake 3. The braking action on the asynchronous alternate current motor 1 is obtained by inserting direct current in it, while sequential pulses are sent to the electromagnetic brake 3 which cause its intervention intermittently or with variable force. The coupling of the two braking systems acting simultaneously permits us to obtain a perfectly controlled stop of the elevator cars 6, to such a point that it is possible to determine with extreme precision the total time of braking, slowing down and stopping, So that it is possible to regulate with precision alignment of the abovementioned levels 12 and 13. This is possible thanks to the different behaviours of the two braking systems: the effect produced by insertion of direct current in the asynchronous alternate current motor 1 causes, as noted, a considerable braking action the first instant, which then drops according to the square of the speed of the motor rotor while slowing down; the simultaneous intermittent action of intervention, exercised simultaneously on brake 3, assists the first action, so that its braking effect, added to the first, permits us to obtain a substantially constant total braking, independent from load and other factors. The intermittent braking action on brake 3 is therefore directed at regulation of the stop run, especially in the final phase, since the real braking action is carried out very efficiently by motor 1 in the first phase, as soon as the direct current is inserted in it. The two braking systems acting simultaneously therefore exercise actions of mutual compensation, giving as final result a constant, regular braking, independent from load. Moreover, thanks to the vigorous initial effect of the braking produced by motor 1, the subsequent intermittent braking interventions with the jaws of brake 3 are more moderate, with the advantage of less wear on said brake.

Claims: A lift comprising an asynchronous alternate current motor (1), an electromagnetic braking device (3), provided with braking jaws, a manoeuvring winch (2) comprising a traction pulley (4) of cables (5) supporting an elevator car (6), at one end, and a counterweight (7), at the other end, and means for controlling the braking device, characterized in that the means for controlling the braking device consists in supplying the asynchronous alternate current motor (1) with direct current and, simultaneously, the electromagnetic braking device (3) with sequential pulses intermittently acting on the jaws. The lift according to claim 1, characterized in that the asynchronous alternate current motor (1) is connected to the manoeuvring winch (2) by the electromagnetic braking device (3). The lift according to claim 1 or 2, characterized in that the braking power of the jaws of the electromagnetic braking device (3) is intermittent and with variable force.-

Inventors: MARTINI ANGELO, MARTINI, ANGELO
Applicants: GMV SERVICE SRL, G.M.V. SERVICE S.R.L.
Application year: 1987
Main classification: B66D5
IPC codes: B66B11, B66D5