Gate for storage-tank outlet

A gating mechanism for selectively opening and closing the bottom outlet of a container such as a tank, bunker or silo, serving for the storage of bulk material, comprises a metallic slider shiftable along the underside of a metallic sealing frame surrounding the outlet, the slider being urged upwardly against that frame by strong compression springs or fluidic jacks counteracting the internal pressure of the goods. The slider, which has a cutout registering with the outlet aperture upon being aligned with the sealing frame, is displaceable between this alignment position and a closure position by a rack on its underside engaged by a driving pinion. A base supporting the slider and forming a channel for the discharged bulk material carries a funnel of rectangular cross-section which defines the outlet and has a flange vertically separated from a discharge port in the container bottom by an interposed spacer frame which can be replaced by a shutter plate of like thickness, e.g. during temporary removal of the slider, upon a raising of the empty tank and a lifting of the spacer frame to a lesser extent with the aid of respective nuts on a set of vertical bolts passing through bores in an external apron of the container body and through slotted lugs of the spacer frame.

My present invention relates to a gating mechanism for the selective 
blocking and unblocking of an outlet of a container, such as a tank, 
bunker or silo, forming part of a facility for the storage of bulk 
material (e.g. grain or coal). 
BACKGROUND OF THE INVENTION 
Conventionally, such outlets--usually provided at the bottom of the 
container--are closable by a slider having a cutout which conforms to the 
outlet opening and is alignable therewith in an unloading position, the 
outlet being obstructed by a solid portion of the slider upon displacement 
thereof to a closure position. The slider is sandwiched between upper and 
lower gaskets respectively carried on the rim of the outlet and on a 
downward extension thereof, these gaskets being intended to insure an 
airtight seal when the outlet is closed. In the closure position, the 
weight of the stored goods bears upon the slider with resulting 
compression of the lower gasket; this may lead to a separation of the 
slider from the upper gasket, with particles of the bulk material 
penetrating into the resulting gaps. The subsequent shifting of the slider 
causes these particles to rub against the upper gasket which is therefore 
subjected to considerable wear. Thus, the desired airtight seal will no 
longer be maintainable. 
OBJECTS OF THE INVENTION 
The general object of my present invention, accordingly, is to provide an 
improved gating mechanism for the selective blocking and unblocking of 
such container outlets with avoidance of the aforestated drawbacks. 
A related object is to provide means for temporarily shutting off such an 
outlet ahead of the sliding gate when the latter is inoperative for any 
reason. 
SUMMARY OF THE INVENTION 
A gating mechanism according to my invention comprises a preferably 
metallic slider which, in contradistinction to the conventional 
arrangement referred to above, is in direct fluidtight surface contact 
with a sealing frame rimming the container outlet, that frame being 
preferably also made of metal. The fluidtight contact is maintained by 
pressure means, such as strong coil springs or fluidic jacks, bearing upon 
the slider from the side opposite the outlet; it will be convenient to 
refer to that side of the slider as its undersurface. The slider is guided 
by fixed support means, independent of the aforementioned pressure means, 
on a structure (referred to hereinafter as a base) which forms a channel 
for the bulk material discharged from the container outlet; the base is 
provided with drive means for alternately displacing the slider into its 
unloading and closure positions. 
As long as the force of the pressure means is sufficient to overcome the 
opposing forces acting from within the container upon the slider, 
especially the weight of the stored goods in the case primarily here 
considered, no gaps will develop between the upper slider surface and the 
rim surface in contact therewith; evidently, these contact surfaces are to 
be carefully machined and finely honed or otherwise smoothed, possibly 
with the aid of a low-friction coating. 
On account of unavoidable manufacturing tolerances, the drive means for the 
shifting of the slider should be coupled therewith only loosely so as not 
to interfere with the action of the pressure means holding the slider 
firmly against the outlet rim, I have found that, for this purpose, it is 
advantageous to use a rack-and-pinion drive. The rack, fixedly secured to 
the underside of the slider, is engaged by the manually or automatically 
driven pinion with a certain amount of play and, preferably, at a location 
offset from the container outlet in the longitudinal direction, i.e. the 
direction of displacement. 
If the contact surfaces of the slider and the sealing frame shown signs of 
wear, they may be readily reground or recoated since they will both be 
accessible upon separation of the slider from the previously emptied 
container. In the event of prolonged removal of the slider, or if the 
gating mechanism is otherwise inoperative, it may be desirable to provide 
alternate means for temporarily sealing the container outlet until normal 
operation is resumed. For this purpose, pursuant to a further feature of 
my invention, the outlet may be formed on a preferably funnel-shaped 
downward extension of the container body, with interposition of a spacer 
frame between a discharge port of that body and its extension. Upon a 
slight lifting of the container body with reference to the base carrying 
the extension, the spacer frame can be extracted and replaced by a solid 
shutter plate of similar thickness which seals the discharge port above 
the outlet proper.

SPECIFIC DESCRIPTION 
In FIGS. 1, 2 and 2a I have shown a base 6 forming a channel for bulk 
material to be unloaded from a group of storage tanks rising above the 
base along that channel, two such tanks having been partly shown at 5 and 
5a. The nonillustrated lower part of the base may be provided with a 
lateral slot through which the bulk material discharged into the channel 
from any such tank may be extracted with the aid of an impeller wheel 
traveling along the slot, as disclosed in my copending application Ser. 
No. 855,270 filed Nov. 28, 1977. 
Tank 5, which is representative of the others, has a bottom flange 4 
surrounding a discharge port 31 (see FIG. 2) in line with an outlet 32 
which is rimmed by a rectangular sealing frame 7. This frame, rigid with 
base 6, lies at the bottom of a funnel-shaped neck 1 (also of rectangular 
cross-section) forming a downward extension of port 31. Neck 1 has a top 
flange 3 which is approximately coextensive with flange 4 and is 
vertically separated therefrom by a spacer frame 21 more fully described 
hereinafter with reference to FIG. 3. A corresponding neck 1a of tank 5a 
is shown to have a flange 3a. Neck 1 and frame 7 are secured to base 6 by 
welding, as shown. 
The highly polished undersurface of metallic sealing frame 7 is in firm 
contact with a similarly polished upper surface of an elongate metallic 
slider 8 which is pressed upwardly against frame 7 by a set of strong coil 
springs 11 arrayed in two rows along the opposite longitudinal edges of 
the slider, at locations laterally offset from outlet 32 as seen in FIG. 
2. Slider 8 has a rectangular cutout 9 which, in an unloading position, 
registers with the identically dimensioned outlet 32. The slider is guided 
by longitudinal bars 10 of base 6, in line with the lateral members of 
frame 7, and rests on skids 15 secured to the sidewalls of the base. 
The springs 11 are grouped in pairs each acting, as best seen in FIG. 2, 
upon the slider 8 through a vertically movable bracket 13 guided by fixed 
ribs 13', the bracket reaching around the corresponding longitudinal edge 
of the slider and carrying two bosses 14 serving to center the associated 
spring pair. Similar bosses 14' on shelves 12, rigid with base 6, extend 
from below into the springs 11 resting on these shelves. 
Although only two pairs of springs 11 in the immediate vicinity of outlet 
32 have been illustrated, it will be understood that these pressure 
elements may be duplicated elsewhere and especially in the region of 
outlet 32a of tank 5a. 
A rack fixedly secured to the underside of slider 8 comprises a pair of 
stringers 16' spanned by a set of pins 16 which are engageable by the 
teeth of a driving pinion 17 keyed to a transverse shaft 18. The latter, 
as shown in FIG. 2a, has a projecting extremity formed with a keyway 19 to 
which a nonillustrated crank or driving gear may be attached. Clockwise 
rotation of shaft 18 as viewed in FIG. 1 aligns the cutout 9 with outlet 
32; couterclockwise rotation aligns a similar cutout 9a with outlet 32a 
while holding the outlet 32 closed. If desired, slider 8 may be formed 
with further cutouts alignable with the outlets of other tanks not shown; 
naturally, it is also possible to provide each tank with its own slider. 
The several coil springs 11 may be replaced by different pressure elements 
in the form of fluidic jacks 111, shown in FIG. 4, with pistons 111' 
loaded by compressed air, for example, A release of the pressure in the 
cylinders of these jacks facilitates the disassembly of the gating 
mechanism, with removal of slider 8 for inspection or repair. 
In the event of such removal, the port 31 of tank 5 may be sealed by a 
shutter plate 20 replacing the spacer frame 21 as particularly illustrated 
for tank 5a. To this end it is merely necessary to elevate the tank 5 to a 
certain extent, thereby increasing the separation of flanges 3 and 4, and 
then to lift the frame 21 to a lesser extent so as to let it lie clear of 
both flanges, allowing its lateral extraction with the aid of a handle 30. 
As best seen in FIG. 3, frame 21 is provided along its minor sides with 
two pairs of external lugs 28 forming slots 27 which in its working 
position are penetrated by respective bolts 23 also passing freely through 
bores in an apron 22 welded to the outer surface of tank 5, this apron 
being supported by webs 34 (tank 5a has similar webs 34a). Bolts 23 have 
hexagonal heads 26 engageable by a wrench in order to hold these bolts 
stationary upon rotation of respective nuts 24 which lie beneeth apron 22 
and serve to raise and lower the tank 5 with reference to the base 6; 
other nuts 25 on bolts 23 underlie the lugs 28 and can be rotated to raise 
the frame 21 or the plate 20 of the flange 3 preparatorily to extraction. 
Upon reinsertion of either the shutter plate or the spacer frame, the nuts 
25 are reverse-rotated to let the insert come to rest on flange 3 
whereupon nuts 24 may also be so rotated to lower the flange 4 onto this 
insert. 
Spacer frame 21 has a number of holes 29 serving for the insertion of 
fastening screws 33, indicated schematically, to immobilize the assembly. 
Similar holes are provided in shutter plate 20 which also has a handle 
corresponding to handle 30 of frame 21.