Patent Publication Number: US-2012045298-A1

Title: Shaft furnace charging installation having a drive mechanism for a distribution chute

Description:
TECHNICAL FIELD 
     The present invention generally relates to a charging installation for a shaft furnace, especially for a blast furnace. More specifically, it relates to a drive mechanism that is used in this type of charging installation to operate a distribution chute for distributing bulk charge material inside the furnace. 
     BACKGROUND 
     A charging installation for a shaft furnace with a drive mechanism for a rotary and pivotable distribution chute is described in U.S. Pat. No. 3,814,403. This drive mechanism has a rotary supporting means that is supported by a fixed structure and capable of supporting the distribution chute. It includes a main drive motor and an auxiliary drive motor for respectively imparting rotation about a vertical axis to the rotary supporting means and pivotal movement about a horizontal axis to the distribution chute. For imparting rotation to the rotary support, first transmission means operationally couple the main drive motor to a first ring gear that is rigidly connected to the rotary support. An independently rotatable second ring gear is mounted on the rotary support and operationally coupled to the auxiliary drive motor by second transmission means. Third transmission means, which are supported by said rotary support, are operationally coupling the second ring gear to the distribution chute for adjusting the pivotal position of the latter. In the drive mechanism of U.S. Pat. No. 3,814,403 an epicyclic sun-and-planet gear train, colloquially called planetary gear, forms part of the second transmission means that operationally couples the auxiliary drive motor to the second ring gear. Together with the drive motors, the epicyclic sun-and-planet gear train is thus supported by the fixed structure. The sun-and-planet gear train ensures identical speeds of rotation of the second ring gear and the rotary support by sole action of the main drive motor, i.e. without the need to operate the auxiliary drive motor, while enabling a differential rotation between the second ring gear and the rotary support to be produced by operating the auxiliary drive motor. 
     With a charging installation as generally described in U.S. Pat. No. 3,814,403, it is possible to direct bulk material (burden) to virtually any point of the charging surface (stockline) by rotating the chute about the vertical furnace axis and by varying the pivotal inclination of the chute about the horizontal axis. Besides other advantages, the above type of charging installation thus enables a wide variety of charging profiles due to its versatility in distributing the burden on the charging surface. As a result, charging installations of this type have found widespread use in industry during the last decades. 
     In view of its heavy-duty and long-term use during a furnace campaign, the drive mechanism of the charging installation requires very reliable and wear-resistant parts, especially as regards the epicyclic sun-and-planet gear train, which is a key component of the mechanism. Since the drive mechanism accounts for a significant portion of the total cost of the charging installation, there is a desire for a solution that enables cost savings by putting less stringent requirements on the drive mechanism in general and on the epicyclic sun-and-planet gear train in particular. 
     BRIEF SUMMARY 
     The invention provides a drive mechanism for a shaft furnace charging installation, which is configured so that it is subjected to less stringent requirements as regards its component parts. 
     The present invention generally concerns a shaft furnace charging installation having a drive mechanism for a distribution chute, typically for a rotary and pivotable distribution chute. More specifically, this drive mechanism comprises rotary supporting means for supporting the distribution chute so that the latter can be rotated, typically about a vertical axis of rotation, and a fixed structure for rotatably supporting these rotary supporting means. It further comprises a main drive motor, used for rotating the chute, and an auxiliary drive motor, used for adjusting the position of the chute, typically the pivotal position about a horizontal axis, relative to the rotary supporting means. Both motors are mounted on the fixed structure. The drive mechanism further comprises first, second and third transmission means. The first transmission operationally couples the main drive motor to a first ring gear rigidly connected to the rotary supporting means for imparting rotational motion to the rotary supporting means about an axis of rotation, typically the vertical central axis of the shaft furnace. The second transmission operationally couples the auxiliary drive motor to a second ring gear that is independently rotatable about the axis of rotation. The third transmission is supported by the rotary supporting means and operationally couples the second ring gear to the distribution chute for adjusting the position of the distribution chute, typically the pivotal position about a horizontal axis. 
     The present invention proposes that the third transmission means comprise at least one epicyclic sun-and-planet gear train that is supported by the rotary supporting means and that is operationally coupled to a third ring gear rigidly connected to the fixed structure. The proposed epicyclic sun-and-planet gear train has an input shaft arranged to be driven by the second ring gear and an output shaft arranged to adjust the position of the distribution chute. 
     By virtue of the proposed configuration, in which the sun-and-planet gear forms part of the rotary supporting means, the overall wear off of certain mechanism components is reduced. This applies in particular to the components of the one or more epicyclic sun-and-planet gear trains themselves. Accordingly, a design with less stringent requirements as to wear-resistance is achieved. Moreover, the proposed configuration allows savings in terms of constructional space, since the sun-and-planet gear no longer needs to be arranged on top of the fixed structure. Furthermore, in case the second ring gear is rotatably supported on a stationary cylindrical support attached to the fixed structure, the rolling bearing required for the independently rotatable second ring gear is under load and in rotation only when the position of the chute is changed through the second and third transmissions by means of the auxiliary motor. 
     According to a preferred embodiment, the sun-and-planet gear train comprises a planet gear carrier that meshes with the third ring gear. In the latter case, it is further preferred for constructional reasons, that the annulus be rigidly connected to the input shaft to be driven by the latter and the sun gear be rigidly connected to the output shaft to drive the latter. This configuration enables practical gear ratios at the level of the second ring gear and the planet carrier. In order to simplify setting the gear ratio at the level of the second ring gear by selection of a readily available gearwheel design, the input shaft is preferably connected to an input gearwheel that meshes with the second ring gear. Advantageously, the gear ratio between the input gearwheel and the second ring gear and the gear ratio between the planet gear carrier and the third ring gear are used as variable design parameters so that a readily available design of planetary gear can be used to put the invention into practice. In this case, these gear ratios can easily be selected such that the sun gear remains motionless, i.e. stationary with respect to the rotary supporting means if the latter rotates while the second ring gear remains stationary with respect to the fixed structure. 
     In one embodiment of the invention, a pair of oppositely arranged pivotable mounting means are arranged on the rotary supporting means and configured to pivotally support the distribution chute for pivoting the distribution chute about a pivoting axis that is perpendicular to the axis of rotation of the rotary supporting means. In a preferred configuration of this embodiment, two planetary gear trains are supported by the rotary supporting means, the output shaft of each sun-and-planet gear train being operationally coupled to either of the pivotable mounting means. Using two smaller planetary gears dimensioned for half the normal load allows further cost savings. Preferably, the output shaft of each sun-and-planet gear train is operationally coupled to either of the pivotable mounting means by means of a self-blocking gear arrangement so that the chute maintains its pivoting position when the output shaft of the planetary gear is not transmitting torque. 
     In another embodiment of the invention, the mechanism includes an angular drive arrangement that comprises a single drive shaft and a crank and connecting rod mechanism with two opposite control levers for pivoting the distribution chute about its pivoting axis. This type of angular drive arrangement is configured to convert rotation of a single drive shaft into a pivoting movement of a distribution chute with two lateral suspensions. Accordingly, in the latter embodiment, a single sun-and-planet gear train, which is supported by the rotary supporting means and the output shaft of which is operationally coupled the single drive shaft, can be used. 
     Preferably, the second transmission means comprise a self-blocking gear arrangement in the gear train between the auxiliary drive motor and the second ring gear so that the second ring gear remains stationary with respect to the fixed structure when the auxiliary drive motor is not in operation. Furthermore, in case a stationary cylindrical support, which extends around the rotary supporting means, is provided for rotatably supporting the second ring gear, the third ring gear is preferably rigidly connected to such stationary support. 
     As will be understood, the proposed type of drive mechanism is industrially applicable in many types of shaft furnace charging installations, and especially in charging installations for metallurgical blast furnaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantages of the present invention will be apparent from the following detailed description of several not limiting embodiments with reference to the attached drawings, wherein: 
         FIG. 1  is a schematic view composed of two partial cross-sections along perpendicular vertical planes of a shaft furnace charging installation equipped with a first embodiment of the drive mechanism according to the present invention. 
         FIG. 2  is a schematic view composed of two partial cross-sections along perpendicular vertical planes of a shaft furnace charging installation equipped with a second embodiment of the drive mechanism according to the present invention; 
         FIG. 3  is a schematic view of a partial cross-section along a vertical plane of a shaft furnace charging installation equipped with a third embodiment of the drive mechanism according to the present invention; 
         FIG. 4  is a schematic view of a partial cross-section along a vertical plane of a shaft furnace charging installation equipped with a fourth embodiment of the drive mechanism according to the present invention. 
     
    
    
     Throughout these drawings, identical reference signs are used to identify identical or similar parts. 
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a first embodiment of the drive mechanism according to the present invention. This drive mechanism is part of a shaft furnace charging installation, e.g. of the type as generally known from U.S. Pat. No. 3,693,812.  FIG. 1  corresponds to a view composed of two cross-sections taken along perpendicular vertical planes that intersect in the furnace central axis A. The drive mechanism comprises a fixed structure  10  having a fixed external casing  11 . The fixed structure  10  is provided with a vertical inner feeding spout  12  through which bulk material can pass into the furnace. Accordingly, the fixed structure  10  is intended to be mounted on the throat of a shaft furnace, in particular a blast furnace, in such a way that the feeding spout  12  is substantially coaxial with the vertical central axis A of the furnace. The drive mechanism is intended to rotate and pivot a distribution chute, only partially and schematically shown at  14 , which is arranged below the feeding spout  12  in order to distribute bulk material circumferentially and radially into the furnace in a manner known per se. 
     The fixed structure  10  supports rotary supporting means  15  comprising a rotary cylindrical body  16  by means of a first rolling bearing  18 . The first rolling bearing  18  supports the rotary cylindrical body  16  in such a way that it can rotate about the central axis A. A disc-shaped protection flange  22  is attached to the lower end of the rotary cylindrical body  16 . The rotary cylindrical body  16  and the protection flange  22  together with the fixed external casing  11  form a housing delimiting an inner chamber  26  from the blast furnace atmosphere for protecting drive mechanism components. The distribution chute  14  is pivotally supported on the rotary supporting means  15  so that the distribution chute  14  can tilt about a horizontal pivoting axis B. Accordingly, circumferential distribution of bulk material is achieved by rotating the rotary supporting means  15  about axis A, whereas radial distribution is achieved by pivoting the distribution chute  14  about axis B. 
     A main drive motor  30  is mounted on the fixed structure  10  for imparting rotational movement to the rotary supporting means  15 . The main drive motor  30  has a main output shaft  32 , which is operationally coupled to the rotary supporting means  15  via first transmission means  34 . The first transmission means  34  comprise a first drive gearwheel  36  coupled to the main output shaft  32  via a first reduction gear  38 . The first drive gearwheel  36  meshes with external teeth of an annular first ring gear  40  that is rigidly fixed on the rotary cylindrical body  16 . Accordingly, rotation of the distribution chute  14  about the central axis A is controlled by operation of the main drive motor  30 . 
     An auxiliary drive motor  42  having an auxiliary output shaft  44  is provided for controlling the inclination (tilt angle) and pivotal movement of the distribution chute  14 . The auxiliary drive motor  42  is mounted on the fixed structure  10  and is operationally coupled via second transmission means  46  to a second ring gear  48 . This second ring gear  48  is rotatably supported on a stationary cylindrical support  49  by means of a second rolling bearing  50  in such a way that it can rotate about the central axis A independently of the position or movement of the rotary cylindrical body  16 . The cylindrical support  49  is attached to the fixed structure  10  and extends down inside the inner chamber  26  coaxially around the feeding spout  12  and the rotary cylindrical body  16 . The second transmission means  46  comprise a second drive gearwheel  52  coupled to the auxiliary output shaft  44  by means of a second reduction gear  53 , e.g. a self-blocking worm gear. The second drive gearwheel  52  meshes with upper external teeth of the second ring gear  48 , indicated at  64 , for transmitting torque from the auxiliary drive motor  42  to the second ring gear  48 . Accordingly, the auxiliary drive motor  42  directly controls rotation of the second ring gear  48 . 
     For controlling the inclination of the distribution chute  14 , the second ring gear  48  is operationally coupled to the distribution chute  14  via third transmission means  54  as described hereinafter. As seen in  FIG. 1 , the third transmission means  54  are supported by the rotary supporting means  15  and arranged inside the inner chamber  26 . Accordingly, the third transmission means  54  rotate together with the rotary cylindrical body  16  and the distribution chute  14  about the central rotation axis A. In the embodiment of  FIG. 1 , the third transmission means  54  comprise two epicyclic sun-and-planet gear trains  56  (also called planetary gears) arranged in opposite parts of the inner chamber  26 . For conciseness, only one of the two epicyclic sun-and-planet gear trains is described hereinafter. The other sun-and-planet gear train is configured in identical manner. 
     According to the preferred embodiment shown in  FIG. 1 , the sun-and-planet gear train  56  comprises an input shaft  58 , which is provided at a first end with an input gearwheel  60  that meshes with lower external teeth of the second ring gear  48 , indicated at  65 . The input shaft  58  is rigidly connected at its second end to an annulus  62 , which forms the outer ring gear of the sun-and-planet gear train  56 . Accordingly, the annulus  62  has internal teeth meshing with at least two planet gears  66  arranged inside the annulus  62  in such a way that the planet gears  66  can roll inside the annulus  62  and revolve about the central axis of the annulus  62 . It should be noted that, when the main drive motor  30  causes the rotary supporting means  15  to rotate about the central axis A, the input gearwheel  60  revolves together with the third transmission means  54  about the central rotation axis A. 
     The planet gears  66  are supported on a planet gear carrier  70  via carrier shafts  68  on which the planet gears  66  are rotatably mounted. The carrier  70  is provided with a toothed outer periphery that meshes with external teeth of a stationary third ring gear  71  that is rigidly attached to the fixed structure  10 . In the embodiment of  FIG. 1 , the third ring gear  71  is fixed to the feeding spout  12  so as to protrude radially into the inner chamber  26  through a gap  28  between the rotary cylindrical body  16  and the protection flange  22 . Alternatively, the third ring gear  71  can be fixed to the cylindrical support  49  as seen in  FIG. 4 , or to the casing  11  and, in the latter case, provided with internal teeth. It should be noted that, when the main drive motor  30  causes the rotary supporting means  15  to rotate about the central axis A, the carrier  70  revolves together with the third transmission means  54  about the central rotation axis A. 
     In typical manner, the sun-and-planet gear train  56  comprises an inner sun gear  72  arranged in between the planet gears  66  and having external teeth meshing with the planet gears  66  in such a way that the planet gears  66  roll on the external teeth of the sun gear  72  when revolving about the central axis of the annulus  62 . According to the preferred embodiment of the invention shown in  FIG. 1 , the sun gear  72  is rigidly connected to an output shaft  74 , which passes coaxially through the carrier  70  and is coupled to pivotable mounting means for adjusting the inclination of the distribution chute  14 . The pivotable mounting means are of known configuration and arranged on the rotary supporting protection flange  22  as part of the third transmission means  54 . For example, as described in U.S. Pat. No. 3,814,403, each pivotable mounting means can comprise a self-blocking worm gear, which includes a threaded spindle  76  and a partial ring gear  78 , and a rotatable supporting shaft  80 . Each supporting shaft  80  is rotatable about horizontal axis B and rigidly connected to either of two oppositely arranged mounting members (not shown) for removably mounting the distribution chute  14  to the rotary supporting means  15 . Accordingly, the inclination of the distribution chute  14  can be adjusted through the output shaft  74  by controlling the rotation of the sun gear  72 . 
     Operation of the drive mechanism is described hereinafter. When the main drive motor  30  causes the rotary supporting means  15  to rotate and provided that the rotational speed of the second ring gear  48  differs from the rotational speed of the rotary supporting means  15 , the input gearwheel  60  rolls on the lower external teeth  65  of the second ring gear  48  and thereby imparts rotational motion to the annulus  62 . The corresponding rotational speed ω 1  of the annulus  62  about its own axis depends on the gear ratio GR 1  between the toothing of the input gearwheel  60  and the lower teeth  65  of the second ring gear  48 . Furthermore, when the main drive motor  30  causes the rotary supporting means  15  to rotate, the carrier  70 , which engages the stationary third ring gear  71 , is caused to roll on the external teeth of the third ring gear  71  and thereby causes each planet gear  66  to revolve about the central axis of the annulus  62  and to rotate about its own axis, i.e. the axis of its respective carrier shaft  68 . The corresponding rotational speed ω 2  of the carrier  70  about its own axis depends on the gear ratio GR 2  between the toothing of the carrier  70  and the third ring gear  71 . It will be appreciated that, the drive mechanism is configured in such a way that, when the second ring gear  48  is maintained at rest with respect to the fixed structure  11  and the main drive motor  30  causes the rotary supporting means  15  to rotate, a particular ratio ω 1 /ω 2  between the rotational speed ω 1  of the annulus  62  and the rotational speed ω 2  of the carrier  70  is obtained, namely the velocity ratio ω 1 /ω 2  at which the sun gear  72  is maintained at rest with respect to the rotary supporting means  15 . This is achieved by an appropriate choice of the aforementioned gear ratios GR 1  and GR 2 . In other words, when the auxiliary drive motor  42  is stopped, no driving torque is transmitted to the sun gear  72  and thus to the output shaft  74 , whereby the distribution chute  14  maintains its pivotal position irrespectively of the actual speed of rotation of the rotary supporting means  15 . Conversely, when the auxiliary drive motor  42  causes the second ring gear  48  to rotate, the rotational speed of the annulus  62  is different from w i  such that a driving torque is transmitted to the sun gear  72  and thus to the output shaft  74 . It follows that the output shaft  74  and the rotatable supporting shaft  80  operationally coupled thereto can be driven by the auxiliary drive motor  42  to pivot the distribution chute  14  about horizontal axis B. 
     Another embodiment of the invention is illustrated in  FIG. 2 , which shows a similar drive mechanism as in  FIG. 1 , except that the sun-and-planet gear train  256  has a different configuration. Only major differences with respect to the drive mechanism of  FIG. 1  will be detailed hereinafter. In the embodiment of  FIG. 2 , the input shaft  258  of the sun-and-planet gear train  256  is connected at its lower end to the inner sun gear  272 . Accordingly, the sun gear  272  rotates with the input shaft  258  when the input gearwheel  260  rolls on the second ring gear  48  as described above in relation to FIG . 1 . The annulus  262  is rigidly connected to the output shaft  274  for adjusting the inclination of the distribution chute  14  by pivotable mounting means as described above. As in the embodiment of  FIG. 1 , the carrier  270  supporting the planet gears  266  is configured to roll on the third ring gear  71 . Consequently, when the second ring gear  48  is at rest with respect to the fixed structure  10  and the rotary supporting means  15  rotate, a particular velocity ratio ω 3 /ω 2  between the rotational speed ω 3  of the sun gear  272  and the rotational speed ω 2  of the carrier  270  is obtained. The drive mechanism of  FIG. 2 , as opposed to that of  FIG. 1 , is configured so that the annulus  262  is maintained at rest with respect to the rotary supporting means  15  at the velocity ratio ω 3 /ω 2 . Again, this can be achieved by an appropriate choice of the aforementioned gear ratios GR 1  and GR 2 . Conversely, when the auxiliary drive motor  42  causes the second ring gear  48  to rotate, the rotational speed of the sun gear  272  differs from ω 3  such that a driving torque is transmitted to the annulus  262  and thus to the output shaft  274 . It follows that the output shaft  274  and the rotatable supporting shaft  80  operationally coupled thereto can be driven by the auxiliary drive motor  42  to pivot the distribution chute  14  about horizontal axis B. 
     As will be understood, in case of restrictions concerning the choice of the gear ratios GR 1  and GR 2 , the sun gear  72 ;  272 , the planet gears  66 ;  266  and/or the annulus  62 ;  262  can be dimensioned in such a way that no driving torque is transmitted to the output shaft  74 ;  274  when the second ring gear  48  is not driven by the auxiliary drive motor  42 . 
       FIG. 3  illustrates a third embodiment of the drive mechanism according to the invention. Only major differences with respect to the above-described drive mechanisms will be detailed hereinafter. The drive mechanism of  FIG. 3  presents a single sun-and-planet gear train  356  supported on the rotary supporting means  15 . Whereas its components are dimensioned for higher load, the general configuration of this single sun-and-planet gear train  356  in itself is identical to that of one of the two sun-and-planet gear trains  56  used in the first embodiment as shown in  FIG. 1 . The input shaft  58  is also connected to an input gearwheel  60  that meshes with the lower external teeth of the second ring gear  48 . The output shaft  74  of the sun-and-planet gear train  356  is however coupled to a different arrangement for pivoting the distribution chute  14 , which is merely schematically illustrated in  FIG. 3 . More specifically, the output shaft  74  is connected to an angular drive as described in U.S. Pat. No. 6,916,146, the disclosure of which is incorporated by reference herein. This angular drive is configured to pivot the distribution chute  14  at two diametrically opposite points of application while having a single input drive shaft. Hence the angular drive according to U.S. Pat. No. 6,916,146 allows using a single sun-and-planet gear train  356 . In order to convert rotation of the output shaft  74  into a pivoting movement of the distribution chute  14 , the angular drive comprises a crank and connecting rod mechanism, schematically indicated at  382  in  FIG. 3 . The crank and connecting rod mechanism  382  has two opposite control levers for pivoting the distribution chute  14  about the horizontal pivoting axis B. Further details of the angular drive used in the embodiment of  FIG. 3  are found in U.S. Pat. No. 6,916,146. 
       FIG. 4  illustrates a fourth embodiment of the drive mechanism according to the invention. The embodiment of  FIG. 4  is generally identical to that of  FIG. 3  except that the cylindrical support  449 , which supports the second ring gear  48  through the rolling bearing  50 , has a different design and that the third ring gear  471  is rigidly fixed to the lower end of this cylindrical support  449 . Accordingly when compared to  FIG. 3 , the cylindrical support  449  extends further downward around the rotary cylindrical body  16  inside the casing  11  to support the third ring gear  471 . 
     As will be understood, in principle any of the three main components of the sun-and-planet gear train, i.e. the annulus, the planet gear carrier and the sun gear can be connected to the input shaft, the output shaft or the third ring gear respectively. It will also be understood that the present invention is not limited in its application to a shaft furnace charging installation of the type as generally known from U.S. Pat. No. 3,693,812, i.e. a charging installation providing rotation and pivoting of a distribution chute about two perpendicular axes. For example, a drive mechanism configured as described hereinbefore may also be used for improving an installation of the type as disclosed in Japanese patent application JP 63 096 205. More specifically, a single sun-and-planet gear train configured as set out above in relation to  FIG. 3  may be employed for rotating the lower rotary chute of a two-part chute according to JP 63 096 205.