[0001] The present invention refers to a braking device for lifting means, such as lifts
or goods lifts.
[0002] 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.
[0003] As known, lifts or goods lifts of the abovementioned type are generally equipped
with Jaw brakes.
[0004] This type 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] The object of the present invention is to eliminate the abovementioned problems.
[0011] According to the present invention, the abovementioned problems are solved using
a braking device comprising two coupled braking systems with simultaneous action.
[0012] In particular, of these two braking systems, one exercises a braking action at the
first stage, which then decreases according to the square of the. speed, and the other
acts intermittently and with variable braking force.
[0013] Preferably, a first braking system may be an asynchronous alternate current motor,
with one speed, supplied with direct current.
[0014] A second braking system to be used in combination with the first may be an electromagnetic
brake with intermittent action on the jaws.
[0015] 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.
[0016] The constructive and operative characteristics of 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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 of 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.
[0021] 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.
[0022] 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.
[0023] . 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.
[0024] . 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 brak- . ing interventions with the jaws of brake 3
are more moderate, with the advantage of less wear on said brake.
1) Braking device for lifting means, such as lifts or goods lifts, characterized by
the fact that it comprises two braking systems (1,3) coupled and with simultaneous
action.
2) Braking device according to claim 1, characterized by the fact that a braking system
exercises a braking action at the first stage, which then drops according to the square
of the speed and the other braking system acts intermittently and with variable braking
force.
3) Braking device according to claim 1 or 2, characterized by the fact that a first
braking system comprises an asynchronous alternate current motor (1), with one speed,
supplied with direct current.
4) Braking device according to any one of the previous claims, characterized by the
fact that a second braking system comprises an electromagnetic brake (3) which exercises
an action of intermittent intervention.
5) Braking device according to any one of the previous claims 3 and 4, characterized
by the fact that the asynchronous alternate current motor (1), with one speed, supplied
with direct current, is connected to the manoeuvring winch (2) of the lift (6) or
goods lift, by the electromagnetic brake (3).
6) Braking device according to any one of the previous claims, characterized by the
fact that the simultaneous control of intervention of the two braking systems (1,3)
is given by the push-button strip (9) applied inside the elevator car (6) or by means
of the push-button strips (9') present on the stop levels (8), through a selector
switch (10).
7) Braking device according to any one of the previous claims, characterized by the
fact that the simultaneous action of the two braking systems (1,3) has a constant,
regular braking effect, independent from load.