Hoisting mechanism for the cover of a furnace

A hoisting mechanism for handling the cover of an electric arc furnace comprises a pivotable gantry base and gantry arms connected thereto which extend over the furnace cover. Traverse bars overlay the gantry arms and are connected to the furnace cover by hoisting rods which pass through the gantry arms. Lifting mechanisms preferably in the form of hydraulic piston-cylinder arrangements are secured, on one end, to the gantry arms and, on the other end, to the lower side of the traverse bars. The mechanism is electrically insulated to eliminate deterioration of the equipment and the existence of electrical circuits and, in addition, the hoisting rods and the piston cylinder mechanisms are water-cooled.

BACKGROUND OF THE INVENTION 
The present invention relates to a hoisting apparatus for a cover of an 
electric arc furnace or similarly bulky object. Basically, two gantry arms 
extend across the cover. Traverse bars overlay the gantry arms and are 
provided with hoisting rods, which may selectively be lifted and lowered 
with the cover. The cover is raised by a hydraulic lifting mechanism, in 
the form of a plunger mechanism or a piston-cylinder device. The gantry 
and traverse arms are water cooled to protect the lifting rods and the 
lifting mechanisms. 
DESCRIPTION OF THE PRIOR ART 
A hoist installation of the general type is shown by German reference DE-OS 
No. 15 08 471. The gantry-type arm, there shown, is pivotal around a 
vertical axis. That hoist apparatus is equipped with many closely arranged 
joints which are above the approximately 35-t cover of the electric arc 
furnace. The gantry arm is thus exposed to a temperature of approximately 
400.degree. C., which can cause deformation of the gantry arm and damage 
to the hoist mechanism, particularly the joints. The mechanism must, to 
avoid down time, be protected from damage by electrical current by having 
the mechanism bridged by electrically conductive copper. Attempts have 
been made to limit the influence of the heat by using heat-protective 
metal sheets arranged below the cover support. This is, however, not 
satisfactory because the metal sheets hinder access to the other equipment 
arranged in or on the cover and, as the electrodes, hot to about 
1,500.degree. C., move upwardly, their heat radiation affects the metal 
sheets to the extent that they tend to bend and drop off. Subsequently, 
the copper bridges and the bearings of the many joints are detrimentally 
exposed to the high temperature. 
SUMMARY OF THE INVENTION 
The object of the present invention is, therefore, the provision of a hoist 
mechanism for a cover for an electric arc furnace which is relatively 
immune to heat and the effects of electric current. This object is 
achieved by arranging, according to the present invention, at least one 
hydraulic-type plunger device or cylinder and piston in each gantry arm 
and having it connected with a traverse bar arranged above the gantry arm. 
Pulling or hoisting rods connected to the traverse bars, passing through 
the gantry arm to the cover. The presently inventive hoisting mechanism 
has no swivel joints which would otherwise be subject to damage. Instead, 
pulling or hoisting rods, having connecting bolts made of 
temperature-resistant steel, are used. The upper connecting bolts are 
located above the gantry arm and, therefore, are in a cooler area since 
the pulling or hoisting rods are more remote from the heat source, i.e., 
they are not as close to the electric arc furnace. 
The object of the present invention, according to a further characteristic 
of the invention, is accomplished by providing protective pipes splashed, 
i.e., in contact with circulating cooling fluid. The cooling fluid 
surrounds the pulling or hoisting rods and the hoisting piston-cylinder 
mechanisms. The gantry arms of the invention and the traverse bars are 
provided with fluid-type connections for a cooling fluid feed-in and a 
cooling fluid drainage so that the coolant passes by and cools the 
hoisting mechanism and its support structure in a precise and simple 
controlled manner. The protective pipes will thus operate at the 
temperature of the coolant and can be kept below a temperature of 
approximately 50.degree. C. without any difficulty. The fact that the 
temperature may be kept down to this degree is particularly important for 
the hydraulic hoisting mechanism. The gantry arm, itself, may be provided 
with reinforcements in the area of the protective pipes for the 
hydraulics. 
In order to eliminate an electrical circuit, an insulating plate may be 
arranged in the protective pipe environment, i.e., beneath the cylinder of 
the hoisting hydraulic mechanism. An insulating sleeve is also arranged 
within the protective pipe for the pulling or hoisting rod. A guide pipe 
is also provided for the pulling or hoisting rod; it being maintained 
within the insulating sleeve. The lug of the pulling or hoisting rod is 
movable and surrounded by insulator rings mounted on a bolt located at the 
pivotal axis of the traverse bar. Therefore, the traverse bar and the 
gantry arm, with the elements contained therein, remain free from electric 
currents since they are insulated therefrom. 
In yet a further development of the present invention, a locking support 
bar passes downwardly through the gantry arm, from the traverse bar, as 
well as through the gantry base and a gantry platform to the electric arc 
furnace platform. The platform is provided with a vertical pivotal axis of 
the gantry arm and a locking mechanism or detent for the locking bar. The 
locking support bar is retracted from its locking position as the cover 
lifts up. This, therefore, makes it possible to rotate the gantry arm.

DETAILED DESCRIPTION OF THE DRAWINGS 
An electric arc furnace 1 is selectively provided with a disc-shaped cover 
2. The furnace is supported on a furnace platform 3. Located in front of 
the arc furnace 1, i.e., to the left in FIG. 1, is a gantry 4 which is 
also supported on furnace platform 3. The gantry 4 is rotatably arranged 
about support pin 20, on wheels 21. The gantry 4 has two gantry bases or 
vertical support members 5 (see FIG. 1) arranged adjacent to each other. 
The gantry bases 5 are each provided with horizontally extending gantry 
arms 6 which are made of cylindrically shaped pipes. Traverse bars 17 are 
arranged above gantry arms 6. Locking support bars 18 pass from traverse 
bars 17, through the gantry arms 6 and the gantry vertical support members 
5, as well as though the gantry 4. The locking support bars 18 also pass 
through bearing plates 19 which are themselves secured to the furnace 
platform 3. 
The furnace cover 2 has four pivot bearings 9 secured to its upper side by 
bolts 10. The pulling or hoisting rods 11 pass through protective pipes 
12a (see FIG. 5) which are welded to the gantry arm 6. A traverse bar 
support 16 has bolts 10b (see FIG. 1) passing through ears of extensions 
of piston rods 14 which are themselves guided in cylinders 15. The piston 
rods 14 and cylinders 15 are the preferred embodiment of the lifting 
mechanism. A hydraulic device can be used, in the same manner as the 
piston-cylinder units, as the lifting mechanisms. The piston rods 14 
enable the furnace cover 2 and the locking support bars 18 to be 
selectively raised once the cylinders of the piston rods 14 are charged 
with pressure from below. The cylinders 15 in which piston rods 14 operate 
are surrounded by protective pipes 12. Electrically insulating resilient 
plates 13 are maintained below cylinders 15 (see FIG. 1) or a bearing 
plate 25 when plunger element 24 is used (see FIG. 3). 
Both the gantry arms 6 and the traverse bars 17 are provided with inlets 7 
for cooling fluid and drainage connections 8 for the cooling fluid. The 
fluid flows through the traverse bars 17 and the gantry arms 6. The 
cooling fluid thus cools the protective pipes 12 and 12a and the elements 
arranged therein. 
FIG. 2 shows the arrangement of the protective pipes 12 and 12a for the 
hoist installation. As there seen, the lifting mechanisms, contained 
within protective pipes 12 and the adjacently located pulling or hoisting 
rods 11, passing through protective pipes 12a are arranged in an even 
distribution on the surface of the furnace cover 2. The cover 2 is 
provided with three apertures 21 for allowing the passage of the 
electrodes and, in addition, an aperture 22 for a vacuum draining 
apparatus. 
FIGS. 3 to 5 show the arrangement of upper and lower reinforcement plates 
23, made of smooth surfaces that serve to protect the gantry arm 6 in the 
area of the protective pipes 12 and 12a. Instead of the piston cylinder 
units shown in FIG. 1, a plunger element 24 is provided to the hoist 
installation. It is supported by a bearing plate 25 and the insulating 
resilient plate 13 located on a stop plate 26. A bore 27 in the lower 
reinforcement plate 22 allows for replacement of the plunger 24, after 
screws 28 (schematically shown) have first been loosened. The tapered 
pulling or lifting rod 11, in its lower portion, extends downwardly 
through a sliding pipe 31 (see FIG. 5) located within an insulating sleeve 
29. Insulating sleeve 29 is inserted in the protective pipe 12a. The ear 
or extension 11a of the pulling rod 11 is secured to the bolt 10a of the 
bearing pivot 16 arranged beneath the traverse bar 17. The hole of ear or 
extension 11a is lined with an electrically insulating ring 30a which 
surrounds bolt 10a. Insulator rings 30 surround bolt 10a and together with 
ring 30a electrically insulate the bolt 10a and traverse bar 17 from the 
furnace cover. The electrically insulating members 30a, 13, 29 and 30 
prevent the occurrence of the completion of an electrical circuit. A 
protective cap 33 (see FIG. 3) protects the plunger element 24 from dirt. 
The upper and lower reinforcements 23 together with the protective pipes 12 
and 12a are approximately 1 meter in height, approximately 1 m in length, 
and approximately 0.5 meter in depth. Together, the reinforcements and 
protective pipes weight approximately 2 tons. Such units are welded in 
openings 32 of the gantry arm 6, the openings having been cut out with a 
welding torch. 
It should be understood, of course, that the specific form of the invention 
herein illustrated and described is intended to be representative only, as 
certain changes may be made therein without departing from the clear 
teachings of the diclosure. Accordingly, reference should be made to the 
following appended claims in determining the full scope of the invention.