US 3751854 A
A cover lifting- and swinging mechanism for a tiltable crucible smelting or oven-type furnace wherein the cover is first caused to lift and then swing to an open position for completely emptying the furnace pot after the furnace charge has been drawn off in the usual manner through a pouring spout. The combined lifting and swinging motions imparted to the cover are effected and controlled by means of a hydraulic cylinder secured at the side of the tiltable furnace structure. The piston component of the cylinder is connected to a cylindrical housing having a swing arm that is secured to the cover and the housing is provided with a cam groove associated with a stationary guide roll so as to exercise positive control over the cover and piston movement.
Description (OCR text may contain errors)
United States Patent [191 Huwyler et al.
[ Aug. 14, 1973 Inventors: Ernst Huwyler, Wettingen; Heinrich Wenzel, Baden, both of Switzerland Aktlengesellschaft Brown, Boveri & Cie, Baden, Switzerland Filed: Feb. 1, 1972 Appl. No.: 222,562
 Foreign Application Priority Data Feb. 5, 1971 Switzerland 1698/71 References Cited UNITED STATES PATENTS 11/1950 Thys 263/33 A X 3,684,261 8/1972 Wynne 263/33 A Primary Examiner-John J. Camby Attorney-Ralph E. Parker et a1.
[ ABSTRACT A cover liftingand swinging mechanism for a tiltable crucible smelting or oven-type furnace wherein the cover is first caused to lift and then swing to an open position for completely emptying the furnace pot after the fumace charge has been drawn OK in the usual manner through a pouring spout. The combined lifting and swinging motions imparted to the cover are effected and controlled by means of a hydraulic cylinder secured at the side of the tiltable furnace structure. The piston component of the cylinder is connected to a cylindrical housing having a swing arm that is secured to the cover and the housing is provided with a cam groove associated with a stationary guide-roll so as to exercise positive control over the cover and piston movement.
2 Claims, 3 Drawing Figures COVER LllFTllNG-AND SWlNGllNG MECHANISM FOR A TllLTABLE FURNACE The present invention relates to an improved cover lifting-and swinging mechanism for a crucible smelting or oven-type furnace, whereby the cover is operated through a swinging arm by means of a hydraulic cylinder which is fastened to the furnace.
The covers of known cover liftingand swinging systems for crucible smelting furnaces are first lifted vertically and then swiveled by means of a cam groove which is engaged by a fixed guide roll, whereby the cam groove is connected with the piston of the hydraulic cylinder. However, such devices wherein the cover of the furnace is lifted and swung laterally for the charging, the removal of slag or specimen, are disadvantageous because they offer no safeguard against a selfacting opening of the cover and a forward shifting of the hydraulic cyliner piston whenever the furnace is tilted to its extreme position, for example in excess of 90. Such tilting of the furnace is a general practice of all foundries in order to empty completely the furnace pot, its inner surface not being smooth.
Furthermore, most foundries employ for economic reasons a suspension trolley, consisting of a track and traveling crane with cable line, whereby the melting pot can be moved across the smelting furnace while the distance to the furnace is not variable, being set on the basis of the mean value of the pouring jet at the various tilting positions of the furnace. Due to the above discussed self-acting shifting of the hydraulic piston and the opening of the cover, the cover will, by necessity, come in contact with the cable line which supports the melting pot. For this reason there is the possibility that molten metal will excape from the melting pot and endanger the service personnel. Furthermore, the collision between furnace cover and cable line can cause portions of the ceramic lining of the furnace cover to drop down because the lining will become red-hot during the smelting operations, thus becoming impactsensitive. I
The self-acting forward shifting of the hydraulic cylinder piston will lead to an increase in the cylinder displacement but this space can not be filled with pressure fluid because the supply line to the cylinder is blocked; a vacuum can not be generated either because conditions will not permit this, with the result that air will flow from outside between piston and seal into the bore of the hydraulic cylinder. An air cushion will thus form within the hydraulic system which can be removed only by a time-consuming and work-interfering bleeding of the hydraulic cylinder after each tilting of the furnace.
it is the primary object of the present invention to provide an improved cover liftingand swinging mechanism for a crucible smelting or oven-type furnace whereby the cover is operated through a swinging arm by means of a hydraulic cylinder fastened to the furnace, and whereby any self-acting opening of the cover will be prevented during the furnace-tilting operation, i.e. at the extreme position of the furnace for discharge of the contents.
In accordance with the invention the cover is retained against opening by a movable arrangement at the upper end of the hydraulic cylinder comprising a cylindrical housing which is fixedly connected on one side to the swinging arm and detachably connected on the other side to the piston of the hydraulic cylinder,
the outside of said housing being provided with a cam groove which is engaged by a roll that is fastened at the furnace or at a platform connected to the furnace, whereby the upper portion of the cam groove, which actuates the lifting of the cover, inclines slightly relative to the housing axis, gradually merging into a cam portion which inclines steeply relative to the housing axis, the latter cam portion serving to generate the swinging motion of the cover.
A preferred embodiment of the invention is described below in detail and is illustrated by the accompanying drawings wherein:
FIG. 1 shows a crucible smelting furnace in side view, also depicting by means of dot and dash lines the furnace in tilting position (angle of tilt approx.
FIG. 2 provides a top view of the tilted furnace; and
FIG. 3 shows a diagram of the housing, with the cam groove illustrated at an enlarged scale.
With reference now to the drawings, a tiltable crucible smelting furnace 11 is provided with a platform 2, and the melting pot is closed off against the outside by means of a heat-blocking cover 5. This cover 5 is fastened to a supporting arm 6, the arm being welded to a cylindrical housing 7 which is arranged movably at the upper end of a hydraulic cylinder 8 and which is detachably connected with the piston of the hydraulic cylinder. At the outer surface of the housing 7 there is provided a cam groove 9, engaged by a roll 10 which is arranged at the furnace platform 2. This roll is balanced by a block 11, provided at the platform 2 which supports the cover 5. The furnace is also equipped with a pouring lip 12 and a hydraulic cylinder 15 which generates the tilting motion of the furnace. Numeral 16 denotes a pan which is suspended from a line 17.
3 Shows tlxths uppetpqrtiqnqf th c graav's', arranged at the housing 7 and provided with a very small angle of inclination, approximately 3 to 5, relative to the axis X)( of the housing 7, this portion of the groove serving for the lifting of the cover 5. This upper groove portion merges gradually into the lower groove portion which has a steep angle of inclination, for example at least 45, relative to the housing axis X-X, this portion of the groove being used to generate the swiveling motion of the furnace cover 5.
The cover liftingand swinging mechanism operates in the following manner:
For the purpose of pouring off its contents, the furnace l is tilted by the hydraulic cylinder 15 in known manner, and the molten metal then flows in accordance with the angle of tilt from the furnace 1 over the pouring lip 12 into the pan to which is suspended from the line 17. The latter is connected in known manner with a, not illustrated, traveling crane which moves along a track across the furnace. Normally, the furnace cover 5 will be closed during this tilting operation.
Whenever the furnace needs to be emptied completely, the angle of tilt must be at least close to 100 from the vertical, as depicted in FIG. 1, and it will then be necessary to prevent the cover 5 to open by itself in this specific tilting position through gravitational force as will happen in case of the above discussed conventional cover liftingand swing'ng devices. This is accomplished by the mechanism proposed in accordance with the invention characterized in that due to the small angle of inclination throughout the upper portion of the cam groove 9 a rise in the center of gravity M, of the cover is forcibly accomplished, and the wedging effect, so generated, will thus prevent a forward sliding of cylinder 7 or cover respectively in the direction of arrow P (see FIG. 1). In order to open the cover 5, it is necessary to actuate the, not illustrated, controls of the hydraulic cylinder 8, with the result that first the center of gravity of the cover will shift by an angle a to M the cover is thus lifted up and will then perform a lateral swing through an additional movement by the angle (a B) to point M If the cover is to be opened toward the rear, its center of gravity is moved hydraulically first by an angle a from M to M and then by an angle B to M' In this case the lower portion of the cam groove 9 must be provided with an inclination which is opposite to the direction depicted in FIG. 3.
The above described mechanism has the substantial advantage that the furnace cover will be kept closed in a positive manner when the furnace is in its discharge position and will never unseat itself during this position. The housing with this specific cam groove, locking the furnace cover in its closed position, can also be used in connection with presently existing furnaces; it is only necessary to provide the hydraulic cylinder which is already present and causes the lifting and swinging of the cover with such a housing 7, and to connect the housing with the arm supporting the cover and with the piston of the hydraulic cylinder.
The cam groove and the roll can be interchanged as to their position without altering the essence of the invention. Likewise, the hydraulic cylinder which operates the furnace cover can be replaced by a pneumatic lifting device.
1. A combined cover lifting and swinging mechanism for a tiltable crucible smelting or oven type furnace comprising a hydraulic cylinder secured to the tiltable furnace structure, said hydraulic cylinder being located at the side of and parallel with the furnace structure so that the piston thereof extends vertically upward when said furnace structure occupies a vertical position, a movable cylindrical housing connected to the piston of said hydraulic cylinder and with its longitudinal axis parallel to said piston, a swingable arm rigidly connected at the opposite ends thereof to the furnace cover and cylindrical housing respectively, the outer side of said cylindrical housing being provided with a cam groove engaged by a roll secured to the tiltable furnace structure, said cam groove including an upper portion having a slight inclination to the longitudinal axis of said cylindrical housing which serves to impart a lifting movement to said arm and cover from the mouth of the furnace when the piston of said hydraulic cylinder is initially actuated, said upper portion of said cam groove merging with a lower portion having a steep inclination relative to the longitudinal axis of said cylindrical housing and which serves to thereafter impart a swinging movement to said lifted arm and cover away from the furnace mouth as said piston is further actuated.
2. A combined lifting and swinging mechanism as defined in claim 1 for a tiltable crucible smelting or oven type furnace wherein said upper portion of said cam groove has an inclination of from 3 to 5 and said lower portion of said cam groove has an inclination of approximately 45.
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