EP0197210B1

EP0197210B1 - Apparatus for charging scrap into a furnace

Info

Publication number: EP0197210B1
Application number: EP19850302310
Authority: EP
Inventors: Toshio Nanjo; Fumio Tomizawa
Original assignee: IHI Corp
Current assignee: IHI Corp
Priority date: 1985-04-02
Filing date: 1985-04-02
Publication date: 1989-07-05
Also published as: DE3571330D1; EP0197210A1

Description

The present invention relates to apparatus for charging scrap into a furnace, in particular a steelmaking 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 including a bucket carriage adapted to carry the scrap bucket and normally positioned at a stand-by position adjacent the furnace, a support structure supporting the bucket carriage, a set of beams which are situated directly adjacent the furnace and along which the bucket carriage may be moved between the stand-by 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.
Figure 1 is a schematic side elevation of a known apparatus for loading scrap into a steel making arc furnace. When scrap a is loaded 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 tnust 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 into the arc furnace b.
However, this known method has various disadvantages: The crane operator e must move the bucket d very slowly into 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.
DE-A-2300849 discloses apparatus for loading material into an electric furnace comprising a carriage 22 running on a track 15. The carriage carries two depending guide plates 27, 28 which define a space accommodating a bucket 25. The bucket is supported by cables 31, 32 by means of which the bucket may be raised and lowered by a motor 37.
FR-A-2435684 discloses apparatus for loading material into a furnace 1 including a scrap iron bucket 3 which is moved from a trolley 2 running on rails 28 to a position above the furnace. The bucket 3 is lifted from the trolley 2 by means of two spaced arms 29 having detents which engage trunnions formed on the outside of the bucket. The arms are pivotally secured to an overhead frame 4 which is arranged to run on rails 5. Actuating rams 32 are controlled to raise the bucket on the end of the arm from the stand-by position on the trolley 2 and then to move it on the rails 5 to the position above the furnace 1. The bucket is then tilted to deposit its load of scrap iron into the furnace.
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.
According to the present invention apparatus of the type referred to above is characterised by 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 supports 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.
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 stand-by position.
Further features and details of the present invention will be apparent from the following description of one specific embodiment of apparatus for automatically charging scrap into an arc furnace which is given by way of example only with reference to Figures 2 and 3 of the accompanying drawings, in which:-

Figure 2 is a schematic end elevation of an apparatus in accordance with the invention; and
Figure 3 is a plan view, partly in section, of the apparatus of Figure 2.

Referring now to Figures 2 and 3, 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 2, a structure including a beam 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.
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 2) end of the bucket carriage 8. The other end of the rope 11 on the drum 10 passes over sheaves 16and 17, a guide sheave 26 and a sheave 18 and is connected to the rear (1eft in Figure 2) 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.
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.
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 37, 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 stopper 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 3 indicates the furnace cover.
The mode of operation of the apparatus 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 2 so that the rope 11 is maintained under tension.
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 place 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 bucker 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.
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.
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 (not shown). The bucket is then refilled with scrap by a scrap crane or replaced by a fresh bucket filled with scrap and the cycle is repeated.
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 by about 19 heats/day. This means that the productivity can be increased by about 5.5%.
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.
The waiting time required for charging scrap into the furnace while the scrap bucket is suspended from the scrap-charging crane can be eliminated. In addition, when the apparatus is appropriately designed, the scrap-charging crane itself can be eliminated.
Elimination of the large overhead crane allows the meltshop building to have a reduced height and a low structural strength and to have a smaller pillar foundation.

Claims

1. Apparatus for sequentially charging scrap into a furnace including a scrap bucket (21), means for transporting the scrap bucket to a position above the furnace including a bucket carriage (8) adapted to carry the scrap bucket (21) and normally positioned at a stand-by position (38) adjacent the furnace, a support structure supporting the bucket carriage (8), a set of beams which are situated adjacent the furnace and along which the bucket carriage may be moved between the stand-by position (38) and a charging position situated directly above the furnace, means (10, 11, 27, 29-34) for moving the bucket carriage (8). along the beams and means (10, 11, 27, 29-34) for lifting and lowering the scrap bucket (21) relative to the bucket carriage (8), 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 (33, 34) 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).

2. Apparatus as claimed in claim 1 characterised in that the arresting means comprises two plates (33, 34) which may be moved by an actuator (29) towards and away from one another to trap or release the counterbalance means (26, 27).

3. Apparatus as claimed in claim 1 or claim 2 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 (38).