U.S. patent number 3,763,968 [Application Number 05/233,053] was granted by the patent office on 1973-10-09 for electro-magnetic braking device.
Invention is credited to Jean Noly.
United States Patent |
3,763,968 |
Noly |
October 9, 1973 |
ELECTRO-MAGNETIC BRAKING DEVICE
Abstract
The electro-magnetic braking device includes two coils
concentrically disposed about a magnetizable core having a high
residual magnetism capable of holding a brake armature in
non-braking position against a spring bias even when the current is
removed form the coils. When it is desired to have the brake
armature spring biased into braking position when the current is
removed from the coils a demagnetization circuit is connected to
one of said coils to demagnetize the core.
Inventors: |
Noly; Jean (La Clayette,
FR) |
Family
ID: |
9073564 |
Appl.
No.: |
05/233,053 |
Filed: |
March 6, 1972 |
Foreign Application Priority Data
Current U.S.
Class: |
188/171; 310/77;
361/210 |
Current CPC
Class: |
F16D
55/02 (20130101); F16D 59/02 (20130101); F16D
2121/22 (20130101); F16D 2065/383 (20130101); F16D
2123/00 (20130101) |
Current International
Class: |
F16D
59/02 (20060101); F16D 59/00 (20060101); F16D
65/14 (20060101); F16D 55/02 (20060101); B60t
013/04 () |
Field of
Search: |
;188/163,164,171,173
;335/268,266 ;517/DIG.4,155.5 ;310/77,78,75,93 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Duggan; D. F.
Claims
I claim:
1. An electro-magnetically controlled brake comprising a rotatable
disc, a movable armature, support means guiding said armature
non-rotatably toward and away from said disc, coil means mounted on
said support means, a stationary component having high residual
magnetism disposed in the magnetic circuit of said armature and
said coil means, resilient means normally biasing said armature
into engagement with said disc to prevent rotation of said disc and
control circuit means including said coil means and relay means for
magnetizing said component upon energization of said relay means to
overcome the force of said resilient means and for automatically
de-magnetizing said component upon deenergization of said relay
means.
2. An electro-magnetically controlled brake as set forth in claim 1
wherein said resilient means is comprised of a compression spring
and means on said support means for adjusting the force of said
spring.
3. An electro-magnetically controlled brake as set forth in claim 1
wherein said coil means is comprised of two separate windings
concentrically arranged around said component, one of said windings
being arranged to magnetize said component and the other of said
windings being arranged to de-magnetize said component.
4. An electro-magnetically controlled brake as set forth in claim 3
wherein said relay means includes a first normally open switch
connected in series with said one of said windings, a second
normally open switch and a third normally closed switch connected
in series with said other of said windings.
5. An electro-magnetically controlled brake as set forth in claim 4
further comprising capacitor means connected in parallel with said
third normally closed switch and said other of said windings and
connected in series with said second normally open switch whereby
upon energization of said relay said second switch will close to
charge said capacitor means while said third switch opens to
prevent energization of said other of said windings and upon
de-energization of said relay said second switch will open and said
third switch will close to allow discharge of said capacitor
through said other of said windings to de-magnetize said
component.
6. An electro-magnetically controlled brake as set forth in claim 4
further comprising a manually operated switch connected in toto
with said first normally open switch to selectively energize said
one of said windings to magnetize said component.
Description
The present invention relates to an electrically controlled two
position brake, which is particularly useful for fitting to a tower
crane to allow the crane to behave as a weather vane when it is out
of service. It is to be understood however that the brake is not
limited in its field of application to cranes.
Known cranes comprise a fixed part (generally the mast) surmounted
by revolving part (jib and counter-jib). In certain circumstances,
it is required that the revolving part can turn on the fixed part;
in other circumstances, it is required that this revolving part
shall be immobilised. The cases usually met with in practice are as
follows:
A. When the crane is out of service, it is generally allowed to
behave as a weather vane to ensure its stability in a wind above 80
kilometres per hour; for this purpose the brakes of the directional
mechanism must be free in order that the jib can itself take up the
direction of the wind;
B. When the crane out of service is in addition not under voltage
the brake must be held in the locked position;
C. If the crane is in ordinary service, the brake must be locked
when the operator decides to stop the directional movement of the
revolving part in the chosen position;
D. Finally, when the electric current is cut off whilst the crane
is in service, the brake must automatically be locked to avoid the
jib continuing its rotary movement under the force of the wind or
of its own inertia.
The systems known up to the present to ensure that the crane is
allowed to behave as a weather vane are mechanically controlled. In
certain cases the crane operator has to activate the directional
mechanism directly which releases the brake through a system of
screws and nuts (the operator is then obliged to go into the
revolving part, that is to say on the top of the crane). In other
cases, the crane operator can actuate the directional mechanism
from the base of the crane, by means of cables and levers.
None of the known systems offers sufficient reliability, especially
if the directional mechanism is positioned on the revolving part of
the crane.
The present invention has the aim of avoiding these disadvantages
by providing an electrically controlled brake which possesses the
characteristic of being two position, that is to say that both in
the rest position and after the current is cut off, it can remain
as required either locked or freed.
An electrically controlled two position brake according to the
invention, intended for fitting between a stationary part and a
moving part comprises a moving armature subject to the action of at
least one electro-magnet and a component in a material of high
residual magnetism interposed in the magnetic circuit so that the
electric control of the electro-magnet permits the component of
high residual magnetism to be either magnetised or
de-magnetised.
According to a preferred feature of the invention, the component
with high residual magnetism is constituted by a stationary heavy
ring against which the armature can be attracted by overcoming a
resilient load, such as that of a spring, when this remanent
component is magnetised, the brake being then released; whilst on
the other hand when the remanent component is de-magnetised, the
action of the resilient loading repels the armature against a
braking disc and the brake is locked.
In one construction a single winding is used arranged around the
highly remanent ring. This winding can be fed by direct current
with a given polarity when it is required to magnetise the ring and
with current of the opposite polarity when it is desired to
de-magnetise the ring.
In another construction two separate windings are arranged around
the remanent ring, namely one winding used for magnetisation, and
another used only for de-magnetisation.
If the brake is used on a crane, it will be understood that if the
crane is taken off current when the remanent component is
magnetised, the residual magnetism will hold the armature attracted
to the remanent component the brake will remain stably in the free
position. If on the other hand the crane is taken off current when
the remanent component is demagnetised the brake will remain locked
under the action of the resilient loading.
In a preferred arrangement, three separate contacts are used,
namely a first contact in series with the magnetisation winding, a
second contact in series with the de-magnetisation winding, and a
third contact controlling the charge of a condenser which is
arranged in parallel on the de-magnetising winding. Owing to this
arrangement, when the direction movement of the crane is stopped,
opening of the third contact isolates the condenser which, because
the second contact is closed, discharges through the
de-magnetisation winding where it produces a sufficient impulse to
de-magnetise the remanent ring so that the brake remains locked
from then on. This system has the advantage of remaining unchanged
in the case of a break in the current supply.
One construction of a brake and its arrangement in accordance with
the invention, will now be described, by way of example only, with
reference to the accompanying drawings, in which:
FIG. 1 is an axial section through a brake in the locked (i.e.
brake applied) position,
FIG. 2 is a section similar to FIG. 1, but showing the parts in the
unlocked position,
FIG. 3 shows diagrammatically the electrical connection of three
control contacts in relation to the general three phase circuit of
a crane, and
FIG. 4 is a diagram of the direct current electric circuit
controlled by the three contacts and illustrating both a
magnetisation winding and a de-magnetisation winding.
The brake shown in FIGS. 1 and 2 comprises a wound yoke formed by a
circular component 1 made in mild steel, and a central core 2 in
the form of a ring, manufactured from some strongly remanent
material, identical to that which is used for example for the
manufacture of permanent magnets, and two circular electro-magnetic
windings 3 and 4, both concentric with and placed around the
central core 2.
This wound yoke acts in co-operation with a moving armature 5 made
of mild steel and fitted with an annular friction pad 6, on its
underside. The armature 5 possesses two lugs 7 which project
radially and which can slide respectively in two longitudinal slots
8 in a fixed support 9 of the brake assembly. The support is made
of a substantially non-magnetic material. Thus the armature 5 can
be displaced freely in the axial direction (as indicated by the
double arrow 10) but it is immobilised against rotation.
Below the friction pad 6 there is placed a brake disc 11 fixed to a
shaft 12 which it is desired to brake.
A compression spring 13, intended to apply the lining 6 of the
armature 5 on to the braking disc 11, is mounted in the centre of
the heavy ring 2, and acts between the armature 5 and a support
screw 14 located in a screw-threaded hole in the top of the frame
9. The regulation of this screw allows the braking effort which
will be applied to the lining 6 to be the adjusted.
The operation of the brake is as follows:
For the first stable position, that is to say when the brake is
locked (FIG. 1), the force of the spring 13 applies the lining 6 to
the brake disc 11, and this locks the disc 11 and the shaft 12
against rotation. To pass the second stable position (brake feed),
it is necessary to supply an electric current to the winding 3,
which is called the magnetisation winding. When the magnetisation
winding is energised, there is an attraction of the mobile aramture
5 towards the ring 2 of the yoke and this frees the brake disc 11.
The current can then be cut off, but the central core 2 remains
magnetised due to its residual magnetism, and holds the mobile
armature 5 firmly against the wound yoke (FIG. 2).
To return the brake to the first stable position (the brake
locked), it is only necessary to feed into the winding 4, which is
called the de-magnetised winding, an electric current of short
duration this current flowing in such a way that it nullifies the
remanent magnetisation of the central core 2. The spring 13 then
repels the armature 5 and applies the direction lining 6 against
the brake disc 11.
The control of these various operations can be carried out from a
relay (FIG. 3) operating simultaneously a first (normally open)
contact K1, a second (normally closed) K2 and a third (normally
open) contact K3. This relay is connected in the three phase feed
line of the directional motor M of the crane.
The contacts K1 and K3 close automatically as soon as the control
for the setting in rotation of the revolving part of the crane is
operated. They open as soon as the control for the cessation of
movement has been operated. They likewise open in the case of a
breakdown in the electrical current supply. On the other hand, the
second contact K2 being normally closed, opens as soon as the
directional movement is begun and closes as soon as this movement
ceases. It likewise closes in the case of a breakdown in
current.
These three contacts are incorporated in a direct current brake
control (FIG. 4). The first contact K1 is arranged in series with
the magnetisation winding 3, so that when the contact K1 is closed,
the winding 3 is energised. The contact K2 is arranged in series
with the demagnetisation winding 4. A condenser C is mounted in
parallel with the contact K2 and the winding 4. These two parallel
connections are fed through the third contact K3.
Finally there is connected in parallel with the first contact K1, a
button B which is positioned at the control position of the crane,
and which allows the brake to be unlocked to allow the crane to
behave as a weather vane.
In particular it will be seen that when the contact K3 is open and
the contact K2 is closed, if the condenser C has previously been
charged, it can discharge through the de-magnetisation winding 4
which allows the freeing of the armature 5 which passes from the
position shwon in FIG. 2 to that in FIG. 1 under the thrust of the
spring 13.
When the operator starts the crane in directional movement, the
following operations take place:
i. the contact K1 feeds the magnetisation winding 3 which releases
the brake;
ii. the contact K3 charges the condenser C, and
iii. the contact K2 isolates the de-magnetisation winding 4.
To cause the movement to stop;
iv. the contact K1 opens the circuit of the magnetisation winding
3, and
v. the contact K2 connects the condenser C which discharges through
the de-magnetisation winding. The brake is then locked.
It will be noticed that the process is carried out in exactly the
same way in the case of a breakdown in the supply of current.
To cause the crane to act as a weather vane, it is sufficient to
press the button B which puts the magnetisation winding 3 under
voltage. The brake is then released. When the button B is released
the brake remains unlocked because of the effect of the residual
magnetiisation of the central core 2 (the de-magnetisation winding
4 is inoperative, since the condenser C has not been charged during
this operation).
Naturally, a signal lamp may also be included in the electrical
circuit to allow the position (locked or unlocked) of the brake to
be observed.
Finally, the brake may be provided with a single winding replacing
the windings 3 and 4. Magnetisation would then be obtained by
passing the current in one direction, demagnetising being produced
when the current passes in the opposite direction in the same
winding, its itensity being limited to a predetermined value by the
insertion of a resistance in the circuit.
* * * * *