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(11) | EP 0 197 210 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Apparatus for charging scrap into a furnace |
| (57) Apparatus for charging scrap (35) into a steel-making arc furnace (1) includes a
scrap bucket (21), a bucket carriage (8) adapted to carry the scrap bucket (21) and
normally positioned at a stand-by position adjacent to the furnace and a support structure
supporting the bucket carriage (8) and including one or more beams (5) along which
the bucket carriage may be moved between the stand-by position and a charging position
situated directly and only a small distance above the furnace (1). The bucket carriage
may be moved along the beams by a winch (10) or a hydraulic actuator and the scrap
bucket (21) may be raised and lowered relative to the bucket carriage (8) by a winch
(10) or a hydraulic actuator. |
[0001] The present invention relates to apparatus for charging scrap into a furnace, in particular a steel-making arc furnace and is concerned with such apparatus of the type including a scrap bucket and means for moving the scrap bucket to a position above the furnace.
[0002] Figure 1 is a schematic side elevation of a known apparatus for loading scrap into a steel making arc furnace. When scrap a is to be charged into the arc furnace b, a scrap bucket d is moved by a large overhead scrap loading crane c to a position directly above the arc furnace b. The view of the crane operator e is very limited due to dust, smoke and the like in the vicinity of the arc furnace b and he must accomplish the fine positional and height alignment of the bucket d with respect to the arc furnace b in response to signals transmitted by an assistant g on the floor f prior to discharging the scrap a into the arc furnace b.
[0003] However, this known method has various disadvantages: The crane operator e must move the bucket d very slowly in to the required position in response to the signals transmitted by the assistant g. Charging scrap a into the arc furnace b is thus a lengthy process, i.e. the tap-to-tap time is increased and a high productivity cannot be attained. In addition, the furnace cover (not shown in Fig. 1) must be open for a long time so that a large quantity of heat escapes from the furnace b into the surrounding atmosphere. The thermal loss is therefore high. If the bucket d and the arc furnace b should be incorrectly aligned some of the scrap a to be charged fails to get into the furnace, some of it a' accumulating on the floor f and some of it a" remaining on the upper surface h of the furnace b. This residual scrap a' and a" must be manually charged into the arc furnace b by the assistant. A long time therefore elapses before the furnace cover may be replaced and the electrodes (not shown) may be switched on. This results also in an increase in the tap-to-tap time and a decrease in the productivity.
[0004] It is an object of the present invention to provide an apparatus for charging scrap into a furnace both rapidly and without the scrap overflowing or accumulating on the top of the furnace so that a saving in both energy and labour costs can be attained and the productivity improved.
[0005] According to the present invention apparatus for charging scrap into a furnace is characterised in that the means for transporting the scrap bucket includes a bucket carriage adapted to carry the scrap bucket and normally positioned at a standby position adjacent to the furnace, which standby position is preferably only a small distance above the top of the furnace, a support structure supporting the bucket carriage and including one or more beams along which the bucket carriage may be moved between the standby position and a charging position situated directly above the furnace, means for moving the bucket carriage along the beams and means for lifting and lowering the scrap bucket relative to the bucket carriage.
[0006] The apparatus preferably also includes a bucket car which is adapted to carry the scrap bucket, which runs on rails situated on the floor adjacent the furnace and from which the scrap bucket is lifted to the standby position.
[0007] The means for moving the bucket carriage along the beams and the means for lifting and lowering the scrap bucket may include a winch and/or a hydraulic actuator.
[0008] One preferred embodiment includes a single winch around which a rope passes, which rope is connected at its two ends to opposite ends of the bucket carriage and also support means for supporting the scrap bucket on the bucket carriage and is connected to movable counterbalance means associated with arresting means arranged to selectively permit or prevent movement of the counterbalance means, whereby actuation of the winch when movement of the counterbalance means is permitted results in movement of the scrap bucket relative to the bucket carriage and actuation of the winch when movement of the counterbalance means is prevented results in movement of the bucket carriage along the beams.
[0009] Further features and details of the present invention will be apparent from the following description of four specific embodiments of apparatus for automatically charging scrap into an arc furnace which is given by way of example only with reference to Figures 2 to 6 of the accompanying drawings, in which:-
Figure 2 is a schematic side elevation of a first embodiment of the invention;
Figure 3 is a schematic end elevation of a second embodiment of the invention;
Figure 4 is a plan view, partly in section, of the embodiment of Figure 3;
Figure 5 is a schematic end elevation of a third embodiment of the present invention; and
Figure 6 is a schematic side elevation of a fourth embodiment of the invention.
[0010] Referring first to Figure 2, a scrap bucket 21, which is loaded with scrap 35 in a scrap yard 39, is movable by a bucket car 4 along rails 3 into a position below a stand- by position 40 of a bucket carriage 8 adjacent to an arc furnace 1. An electrically driven winch drum 10 on the carriage 8 may be actuated to winch up the bucket 21 to the stand-by position 40. When it is needed, the bucket 21 is transported along guide rails 6 which are located on beams 5 at the stand-by position 40 and beams 5' above the furnace 1 and is automatically stopped directly above the furnace 1 by a limit switch (not shown) in the desired charging position a small distance above the furnace. Clamshell-type bucket gates 25 of the bucket 21 are then opened to discharge scrap 35 into the furnace 1. After scrap 35 has been charged into the furnace, the bucket 21 is returned onto the bucket car 4 in the reverse manner and is transported to the scrap yard 39 for re-loading with scrap. The cycle is then repeated.
[0011] In the apparatus of the present invention, not only is the large overhead crane c, as shown in Figure 1, eliminated but also the charging of scrap into the arc furnace 1 may be effected in a short time without part of the scrap failing to drop into the furnace, so that the steel-making productivity of the furnace is increased. Moreover, elimination of the large overhead crane permits the smelting building to have a relatively small height and to be structurally weak and to have smaller pillar foundations. This represents a substantial financial saving.
[0012] Referring now to Figures 3 and 4, a bucket car 4 rides on a pair of parallel rails 3 laid on the foundation floor 2 adjacent to the arc furnace 1. As seen in Figure 3, a structure including beams 5 extends above the arc furnace 1 and the rails 3 such that the axis of the beams 5 intersects extensions of the axes of the arc furnace 1 and the rails 3 at right angles. A bucket carriage 8 with a brake 7 rides on guide rails 6 which are located on the beams 5.
[0013] A winch drum 10 which is driven by a motor 9 is disposed at a suitable position on the foundation floor 2. One end of the rope 11 which is wound on or off by the winch drum 10 passes over a sheave 12 disposed at one end(i.e. the end remote from the arc furnace 1) of the beams 5, a sheave 13 disposed on the bucket carriage 8, a hook sheave 19, a sheave 14 disposed on the bucket carriage 8 and a sheave 15 disposed at the other end (i.e. the end adjacent to the arc furnace 1) of the beams 5 and is connected to the front (right in Figure 3) end of the bucket carriage 8. The other end of the rope 11 on the drum 10 passes over sheaves 16 and 17, a guide sheave 26 and a sheave 18 and is connected to the rear (left in Figure 3) end of the bucket carriage 8. The sheaves 16,17 and 18 are disposed on the beams 5. As the winch drum 10 is rotated by the motor 9, the rope 11 is wound or unwound so that the bucket carriage 8 moves along the guide rails 6 on the beams 5. There is provided a limit switch (not shown) which is actuated when the bucket carriage 8 is in the position directly above the arc furnace 1 which is so arranged that the motor 9 is switched off to stop movement of the bucket carriage 8.
[0014] The hook sheave 19 is located between the sheaves 13 and 14 on the bucket carriage 8 and a hanger 20 is suspended from the hook sheave 19 from which the scrap bucket 21 is suspended. The lower surface of the bucket carriage 8 is formed with a recess 23 which is adapted to receive an abutment 22 extending upwardly from the upper end of the frame of the hook sheave 19. When the abutment 22 engages in the recess 23 of the bucket carriage 8, further upward movement of the hanger 20 is prevented. The recess 23 is provided with a rope tension sensor (not shown) which is adapted to detect the tension in the rope 11 after the abutment 22 has entered the recess 23 to switch the motor 9 off when the tension reaches a predetermined value. An auxiliary winch 24 is mounted on the bucket carriage 8 for opening or closing the clamshell-type bucket gates 25 of the scrap bucket 21.
[0015] The guide sheave 26 is located between the sheaves 17 and 18 and carries a balance weight 27. A balance weight arresting device, generally indicated by reference numeral 28, is disposed adjacent to the balance weight 27. The balance weight arresting device comprises a pneumatic cylinder 29 vertically disposed on the foundation floor 2, a rod 30 having its lower end connected to the piston rod of the pneumatic cylinder 29, a stationary guide frame 44, links 31 which are pivotally connected at one end by pins 32 to the upper and lower ends, respectively of the rod 30 and at the other end to a stoppper plate 33 extending parallel to the rod 30, and an arresting plate 34 extending vertically between the foundation floor 2 and the beams 5 parallel to the stopper plate 33 and spaced therefrom by a predetermined distance in the horizontal direction so that the balance weight 27 is located between the stopper plate 33 and the arresting plate 34. It may be seen that the rod 30, the links 31 and the stopper plate 33 make up a parallel linkage so that when the piston rod of the air cylinder 29 is extended or retracted, the stopper plate 33 is moved away from or towards the arresting plate 34. When the piston rod of the pneumatic cylinder 29 is retracted, the stopper plate 33 is moved towards the arresting plate 34 so that the balance weight 27 is clamped between them. Reference numeral 36 in Figure 4 indicates the furnace cover.
[0016] The mode of operation of the second embodiment is as follows: The bucket 21 is charged with scrap 35 and mounted on the bucket car 4 which is moved to a position adjacent to the arc furnace 1. The bucket carriage 8 is positioned directly above the scrap bucket 21 mounted on the bucket car 4, and after engaging the hanger 20 with appropriate connecting points on the bucket 21, the motor 9 is switched on to rotate the winch drum 10 in the anti-clockwise direction X thereby lifting the bucket 21. As the bucket 21 is lifted, the abutment 22 above the hook sheave 19 engages in the recess 23 of the bucket carriage 8 thereby preventing further movement of the bucket. The tension exerted on the rope 11 is sensed by the rope tension sensor which switches the motor 9 off . When the bucket 21 is raised or lowered, the brake 7 of the bucket carriage 8 is applied so that the bucket carriage 8 is held stationary on the guide rails 6 and the balance weight arresting device 28 is released so that the balance weight 27 is free. As the bucket is raised the balance weight 27 is lowered to the position shown in chain dotted lines in Figure 3 so that the. rope 11 is maintained under tension.
[0017] When the bucket 21 has been lifted as described above, the brake 7 of the bucket carriage 8 is released and the piston rod of the air cylinder 29 is retracted so that the balance weight 27 is trapped between the stopper plate 33 and the arresting plate 34 and consequently held stationary. The winch drum 10 is then rotated in the anti-clockwise direction X and the rope 11, whose one end is connected to the front end of the bucket carriage 8, moves the latter towards the arc furnace 1. When the bucket carriage 8 is in the position directly above the arc furnace 1, the limit switch (not shown) is actuated and the motor 9 is switched off and the bucket carriage 8 is thus stopped. It will be apparent that the rope 11 whose other end is connected to the rear end of the bucket carriage 8, is unwound from the winch drum 10 by a length equal to the distance moved by the bucket carriage 8.
[0018] When the motor 9 is switched off, the brake 7 is applied and the balance weight arresting device 28 and thus the balance weight 27 are released. The balance weight 27 is therefore now free to be raised or lowered. The winch drum 10 is then rotated in the clockwise direction i.e. the direction opposite to the direction indicated by the arrow X, thereby lowering the bucket 21 to a predetermined level Y at which scrap 35 in the bucket 21 is to be charged into the furnace. Whilst this occurs the balance weight 27 is lifted to the position indicated by solid lines in Figure 3. The auxiliary winch 24 is then actuated to open the gates 25 of the bucket 21 so that the scrap 35 drops into the furnace.
[0019] After the scrap has been charged into the furnace, the steps described above are reversed to load the scrap bucket 21 onto the bucket car 4 again. More particularly, the gates 25 of the bucket 21 are closed and the bucket 21 is lifted until the abutment 22 above the hook sheave 19 engages in the recess 23 of the bucket carriage 8. The bucket carriage 8 is then moved towards the position directly above the bucket car 4 and the bucket 21 is lowered onto the bucket car 4. The bucket carriage 8 is then moved slightly towards the arc furnace 1 so that the hanger 20 is released from the bucket 21. The hanger 20 is then lifted to the upper position. The bucket 21 which is now empty is moved by the bucket car 4 toward a predetermined station 39 (Fig. 2). The bucket is then refilled with scrap by a scrap crane 43 (Fig. 2) or replaced by a fresh bucket filled with scrap and the cycle is repeated.
[0020] In the third embodiment illustrated in Figure 5 the bucket carriage 8 and the hanger 20 are not moved by the winch drum 10 as in the case of the second embodiment but instead the bucket carriage 8 is moved by a hydraulic cylinder 37 disposed at one end of the beam 5 while the hanger 20 is lifted by means of a hydraulic cylinder 38 disposed on the bucket carriage 8.
[0021] The third embodiment has a similar function and similar advantages to those of the second embodiment. It will be understood that electric winches may be used instead of the hydraulic cylinders 37 and 38. Alternatively, a combination of hydraulic cylinders with electric winches may be used.
[0022] In the fourth embodiment which is illustrated in Figure 6, the scrap bucket 21 which is loaded with scrap in the scrap yard 39, is transferred by the bucket car 4 along the rails 3 into an arc furnace yard 41 and is then lifted up by an overhead crane 42. (These operations are similar to those used with the known prior apparatus of Figure 1). The scrap bucket 21 is loaded by the crane 42 onto the bucket carriage 8 which is at the stand-by position 40 adjacent to the arc furnace 1. When required, the scrap bucket 21 is moved by the bucket carriage 8 into a position just above the arc furnace 1 and scrap 35 is charged into the furnace in the same manner as in the embodiment of Figure 2.
[0023] The effects, features and advantages of the present invention may be summarised as follows: The scrap bucket which is normally disposed adjacent to the arc furnace may be automatically and accurately brought to the desired position directly above the arc furnace. As a result, scrap can be automatically charged into the arc furnace within a short period of time and without overflowing or accumulating on the top of the furnace. As a result, the tap-to-tap times are shortened so that a high productivity may be attained. For instance, when the present invention is applied to a UHP arc furnace, the tap-to-tap time of about 80 minutes (18 heats/day) can be reduced by four minutes for three scrap buckets charging per heat. Thus, the tap-to-tap time becomes about 76 minutes so that the furnace operation can be increased to about 19 heats/day. This means that the productivity can be increased by about 5.5%.
[0024] A floor operator is not required to transmit signals to a crane operator or to manually load from the floor or the top of the furnace into the furnace. The time for which the lid of the furnace must be kept opened is reduced so that the transmission of heat from the furnace to the atmosphere is reduced to a minimum. As a result, the consumption of electric power can be reduced.
1. Apparatus for sequentially charging scrap into a furnace including a scrap bucket
and means for transporting the scrap bucket to a position above the furnace characterised
in that the means for transporting the scrap bucket includes a bucket carriage (8)
adapted to carry the scrap bucket (21) and normally positioned at a stand-by position
(40) adjacent to the furnace, a support structure supporting the bucket carriage (8)
and including one or more sets of beams (5,5') which are situated directly on or adjacent
the furnace and along which the bucket carriage may be moved between the stand-by
position (40) and a charging position situated directly above the furnace, means (10,11,27)
for moving the bucket carriage (8) along the beams (5,5') and means (10, 38) for lifting
and lowering the scrap bucket (21) relative to the bucket carriage (8).
2. Apparatus as claimed in Claim 1 characterised by a bucket car (4) which is adapted
to carry the scrap bucket (21) which runs on rails (3) situated on the floor adjacent
the furnace and from which the scrap bucket (21) is lifted to the stand-by position
(40).
3. Apparatus as claimed in Claim 1 or Claim 2 characterised in that the means for
moving the bucket carriage (8)along the beams (5,5') include a winch (10).
4. Apparatus as claimed in Claim 1 or Claim 2 characterised in that the means for
moving the bucket carriage(8) along the beams (5) include a hydraulic actuator (37).
5. Apparatus as claimed in any one of the preceding claims characterised in that the
means for lifting and lowering the scrap bucket (21) include a winch (10).
6. Apparatus as claimed in any one of Claims 1 to 4 characterised in that the means
for lifting and lowering the scrap bucket (21) includes a hydraulic actuator (38).
7. Apparatus as claimed in Claim 3 characterised by a brake (7) on the bucket carriage
(8).
8. Apparatus as claimed in Claims 3 and 5 characterised by a single winch (10) around
which a rope (11) passes, which rope (11) is connected at its two ends to opposite
ends of the bucket carriage (8) and also supports means (19,20) for supporting the
scrap bucket (21) on the bucket carriage (8) and is connected to movable counterbalance
means (26,27) associated with arresting means (34,35) arranged to selectively permit
or prevent movement of the counterbalance means (26,27) whereby actuation of the winch
(10) when movement of the counterbalance means (26,27) is permitted results in movement
of the scrap bucket (21) relative to the bucket carriage (8) and actuation of the
winch (10) when movement of the counterbalance means (26,27) is prevented results
in movement of the bucket carriage along the beams (5).
9. Apparatus as claimed in Claim 8 characterised in that the arresting means comprises
two plates (34,35) which may be moved by an actuator (29) towards and away from one
another to trap or release the counterbalance means (26,27).