Pivot assembly for connecting a cover member to a housing of a sliding closure unit

A pivot assembly for pivoting a cover member to a housing of a sliding closure unit includes a pivot shaft supported by the housing and connected to the cover member with play therebetween, such that upon pressing the cover member toward refractory plates of the sliding closure unit, respective sliding surfaces of the refractory plates are free of binding and are maintained substantially in uniform surface-to-surface contact. An auxiliary pivot is formed on the cover member to define a pivot axis parallel to the axis of the pivot shaft. Control members connect the pivot shaft to the auxiliary pivot to maintain a constant spacing between the pivot axis and the axis of the pivot shaft in directions parallel to the direction of movement of a movable refractory plate of the sliding closure unit. As a result, displacement of the cover member relative to the housing due to friction between the sliding surfaces of the refractory plates is prevented.

BACKGROUND OF THE INVENTION 
The present invention relates to a pivot assembly for connecting a cover 
member to a housing of a sliding closure unit employed for controlling the 
discharge of molten metal from a metallurgical vessel and of the type 
including a housing fixed to the metallurgical vessel, at least one 
stationary refractory plate positioned within the housing, a movable 
refractory plate mounted within the housing for movement relative to the 
stationary refractory plate, a cover member for pressing together the 
refractory plates to urge respective abutting sliding surfaces thereof 
into sealing contact, and a pivot shaft pivotally connecting the cover 
member to the housing so that the sliding closure unit may be opened for 
replacement of the refractory plates. 
In this type of sliding closure unit, there must be provided play in the 
pivot assembly to ensure that, in the operating position of the sliding 
closure unit, the movable plate will be pressed, free from tilting or 
binding, against the bottom stationary refractory plate, or in the case of 
a three-plate sliding closure unit, against the stationary bottom plate 
and the stationary stay plate. That is, it is necessary during operation 
of the sliding closure unit that the sliding surfaces of the refractory 
plates are free of binding and are maintained in substantially uniform 
surface-to-surface contact under the influence of the pressure exerted by 
the cover member. 
West German DE-OS No. 21 61 368 discloses an arrangement whereby play is 
provided by the cover member having therethrough a hole or opening which 
fits over a pivot shaft supported by the housing, the hole or opening 
having a larger diameter than the diameter of the shaft. Thus, play is 
provided to enable the cover member, and thereby the refractory plates 
supported thereby, to accommodate forces such as expansion, etc., during 
operation to ensure that the sliding surfaces of the refractory plates are 
free of binding and are maintained in substantially uniform 
surface-to-surface contact while being pressed together by the cover 
member. However, this arrangement is effective only up to a certain point, 
since during movement of the movable refractory plate, during which time 
friction is generated between the abutting sliding surfaces, the loose 
pivot assembly enables displacement of the cover member relative to the 
housing. To prevent this disadvantage, the above known arrangement 
provides abutment surfaces extending transverse to the direction of 
movement of the movable refractory plate to thereby prevent displacement 
of the cover member relative to the housing and to guide the pressing 
movement of the cover member toward the refractory plates. 
West German DE-OS No. 24 59 568 discloses another arrangement wherein the 
pivot shaft of the assembly is mounted on the cover member and guided in 
slots provided in the housing and extending in the direction in which the 
refractory plates are pressed, or perpendicularly to the respective 
sliding surfaces thereof. These slots thereby provide free play to the 
cover member to uniformly urge the refractory plates against one another. 
A disadvantage of this known arrangement however is the relatively 
elaborate fabrication of the slots compared to a single hole or opening. 
Furthermore, in an arrangement whereby the pivot assembly extends 
transverse to the direction of movement of the movable refractory plate, 
the pivot shaft can be pressed onto the guiding surfaces of the slots due 
to the frictional forces generated during movement of the movable 
refractory plate, thereby eliminating the play of the cover member. 
SUMMARY OF THE INVENTION 
With the above discussion in mind, it is an object of the present invention 
to provide an improved pivot assembly between a housing and a cover member 
of a sliding closure unit, whereby it is possible to overcome the above 
and other prior art disadvantages. 
It is a further object of the present invention to provide such a pivot 
assembly whereby it is possible to ensure that the sliding surfaces of the 
refractory plates are free of binding and are maintained in substantially 
uniform surface-to-surface contact under the influence of pressing by the 
cover member, while at the same time preventing displacement of the cover 
member relative to the housing due to friction generated between the 
sliding surfaces of the refractory plates upon movement of the movable 
refractory plate. 
It is a specific object of the present invention to provide such a pivot 
assembly employable especially in sliding closure units of the type 
wherein the pivot shaft between the housing and the cover member extends 
transverse to the direction of movement of the movable refractory plate. 
It is an even further object of the present invention to provide an 
improved sliding closure unit incorporating such pivot assembly. 
These objects are achieved in accordance with the present invention by the 
provision of means connecting the cover member to the pivot shaft with 
play therebetween, thereby ensuring that the sliding surfaces of the 
refractory plates are free of binding and are maintained in substantially 
uniform surface-to-surface contact under the influence of pressure exerted 
by the cover member, means forming an auxiliary pivot on the cover member 
and defining a pivot axis parallel to the axis of the pivot shaft, and 
control means connecting the pivot shaft and the auxiliary pivot for 
maintaining a constant spacing between the pivot axis and the axis of the 
pivot shaft. Thus, the pivot shaft and the auxiliary pivot are mounted and 
positioned in a manner to be free of relative play, thereby preventing 
displacement of the cover member relative to the housing due to friction 
between the sliding surfaces of the refractory plates upon movement of the 
movable refractory plate. 
The pivot shaft is supported by at least one boss, preferably two bosses, 
formed on the housing, and the connecting means comprises a hinge portion 
of the cover member having therethrough an opening, the pivot shaft 
extending through the opening with clearance between the pivot shaft and 
the hinge portion, preferably the hinge portion being positioned between 
the two bosses. The control means comprises at least one plate, preferably 
two plates, each having a first end connected to the pivot shaft and a 
second end pivoted to the auxiliary pivot. The two plates are connected to 
opposite ends of the pivot shaft. The auxiliary pivot comprises a pair of 
pivot pins fixed to the cover member and having pivoted thereto the second 
ends of respective of the plates. Preferably, one of the plates is fixed 
to the respective end of the pivot shaft, thereby forming a mounting unit, 
and the other plate is removably connected to the other end of the pivot 
shaft. In the operating position of the sliding closure unit, the 
auxiliary pivot and the longitudinal dimensions of the two plates extend 
in a single plane parallel to the sliding surfaces of the refractory 
plates.

DETAILED DESCRIPTION OF THE INVENTION 
In FIG. 1 is partially shown the bottom of a metallurgical vessel, for 
example a steel ladle, including a refractory lining 2 and a metal outer 
casing 1 having therethrough a nozzle brick 3 through which is to be 
discharged molten metal. For this purpose, mounted on metal jacket 1 is a 
sliding closure unit 4 of the three-plate rectilinearly movable type. 
Thus, the sliding closure unit includes a housing 6 fixed to the jacket 1, 
for example by bolts 5, an upper or bottom stationary refractory plate 7 
positioned within housing 6, a lower stationary refractory plate 11 
mounted within a housing cover member 12, and a movable refractory plate 
10 surrounded by a frame 8 and movable by a control member 9 in opposite 
rectilinear directions to thereby control the discharge of molten metal 
from the metallurgical vessel. The cover member 12 is pivotally connected 
to housing 6 by means of a pivot shaft 16, and cover member 12 presses the 
refractory plates upwardly, for example by means of bolts 14, such that 
the refractory plates 7, 10, 11 are pressed together to urge respective 
abutting sliding surfaces 15 thereof into sealing contact. The structure 
described above is intended to be substantially conventional and therefore 
is not described in more detail. 
It is essential that, during upward pressure by the cover member 12 due to 
bolts 14, the cover member 12 and the sliding surfaces 15 of refractory 
plate 7, 10, 11 be relatively adjustably movable in directions 
perpendicular to the directions of pressure exerted by bolts 14, and this 
must be achieved without hindrance by the pivot assembly 13 between the 
housing 6 and the cover member 12. At the same time however, due to the 
upward pressure tending to urge the refractory plates together, upon 
movement of movable refractory plate 10 there tends to be frictional 
forces generated between the sliding surfaces 15, and this friction tends 
to cause cover member 12 to be moved in the direction of movement of the 
movable refractory plate 10. This relative displacement of cover member 12 
must however be prevented. 
In accordance with the present invention, the above is accomplished by an 
arrangement such that pivot shaft 16 is supported by spaced apart bosses 
17 formed on housing 6. A hinge portion 21 of the cover member 12 is 
positioned between bosses 17. Hinge portion 21 has therethrough an opening 
through which extends the pivot shaft 16. The opening is of a size to 
provide a clearance 22 between pivot shaft 16 and hinge portion 21. 
Accordingly, the pivot assembly 13 is constructed such that play exists 
between the cover member 12 and the housing 6 in directions to ensure that 
the sliding surfaces 15 are free of binding and are maintained in 
substantially surface-to-surface contact under the influence of pressing 
by bolts 14 and during movement of movable refractory plate 10. 
Additionally, auxiliary pivot pins 19 are attached to cover member 12 in 
coaxial alignment and define a pivot axis which is parallel to the axis of 
pivot shaft 16. Control members in the form of rods or plates 18 are 
connected to pivot shaft 16 and are pivoted to respective pins 19 to 
thereby maintain a constant spacing between the pivot axis of pins 19 and 
the axis of pivot shaft 16. In other words, control members 18 maintain a 
fixed spacing between pivot shaft 16 and pivot pins 19 in the direction of 
movement of movable refractory plate 10. In the specifically illustrated 
arrangement, one plate 18 is fixed to one end of pivot shaft 16 and the 
other plate 18 is removably connected to the opposite end of pivot shaft 
16, for example by means of a nut 23. Opposite ends of plates 18 are 
pivoted to respective pins 19 and retained thereon, for example by means 
of cotter pins 20, or the like. As shown particularly in FIG. 3, the pivot 
axis of pivot pins 19 and the longitudinal axes or dimensions of rods or 
plates 18 extend in a single plane parallel to the sliding surfaces 15 of 
the refractory plates. 
By the above structure of the present invention there is formed essentially 
a double pivot assembly which enables cover member 12 to move without 
hindrance in directions perpendicular to the sliding surfaces 15, while 
maintaining cover member 12 fixedly positioned relative to housing 6 in 
the directions of movement of movable refractory plate 10, i.e. in 
directions parallel to sliding surfaces 15. 
The above arrangement of the present invention particularly is useful in 
the illustrated arrangement wherein the axis of pivot shaft 16 extends 
transverse to the direction of movement of movable refractory plate 10. 
This arrangement provides maximum advantage of the structural features of 
the present invention. However, the present invention equally is 
applicable to arrangements wherein the pivot shaft 16 extends other than 
perpendicular to the direction of movement of the movable refractory 
plate. 
Although the present invention has been described and illustrated with 
respect to a preferred embodiment thereof, it is to be understood that 
various changes and modifications may be made to the specifically 
described and illustrated features without departing from the scope of the 
present invention. It particularly is to be understood that the present 
invention is applicable to two-plate rectilinear sliding closure units as 
well as to rotary and swivelly movable sliding closure units.