An anti-choke blender fitting used in a pneumatic conveyor system utilizing a negative pressure to transport milling stock material, the fitting including a body with a top surface joined by downwardly extending side walls terminating in an open bottom with a channel-shaped relief gate with upwardly extending side walls hingedly mounted to the body with a closed position of the relief gate closing the open bottom of the body in a non air-tight relationship with the side walls of the gate extending above the spout of the inlet conduit, thereby minimizing the leakage of milling stock around the periphery of the relief gate in its closed position.

BACKGROUND OF THE INVENTION 
The invention relates to pneumatic conveying and more specifically to 
conveying milled materials such as flour from one point to another by 
means of negative pressure. The invention, which is a blender fitting, is 
utilized in pneumatic conveying systems for blending high volumes of 
suction air with the milled stock as a means of conveying the milled stock 
from one location to another. Blender fittings also have the function of 
an overload release means, also referred to as an anti-choke dump valve, 
which automatically releases the milled material in the system when it 
chokes or clogs. 
DESCRIPTION OF THE PRIOR ART 
Blender fittings of the prior art generally perform these functions. They 
have been available in the pneumatic conveying industry for many years and 
a typical example is applicant's own U.S. Pat. No. 3,198,584. There are 
also two blender fittings currently on the market, one of which is 
manufactured by the Henry Simon, Ltd. Company of Cheshire, England, and 
the second being a Swiss company by the name of Buhler. The basic problem 
which all of the above-mentioned blender fittings have, and the present 
invention has resolved, is the elimination of mill stock leakage around 
the joints of the relief gate. This leakage of milling stock, which takes 
place through joints in the fitting, is at a slow rate; however, in time 
it creates a substantial build-up on the floors and must be eventually 
dealt with. 
Conveying milled materials such as flour from one point to another is best 
done by a negative pressure pneumatic conveying system since it is the 
most sanitary way of transporting a solid product. This is because all of 
the components of the system are in a negative pressure condition. 
Negative pressure in pneumatic systems of this type are well known in the 
art. The main components of such a system include a vacuum producer in the 
form of a centrifugal fan which draws the milled material from a source 
which could be grinding or sifting apparatus or merely a storage bin. 
Typically the storage bin feeds the material to be conveyed into the inlet 
conduit of a blender fitting for transmission. The material is then 
transmitted through the tubes of the system by the flow of large amounts 
of air induced or sucked into the blender fitting. Once the material is 
transported to its final location, a device such as a cyclone separator 
will separate the material from the negative pressure air for deposit in a 
storage bin. The suction means is provided by a centrifugal fan or the 
like which is connected to the cyclone separator. The milling stock 
materials thus are transported through the system in a stream of high 
velocity air which is allowed into the system through a blender fitting, 
such as the present invention. The milling stock is blended with the high 
velocity air stream, transmitting the product to its destination, 
whereupon the product and air are separated. 
One of the major problems with pneumatic conveyers involves the stoppage or 
clogging of the conduits due to a variety of factors. If the milled 
material is fed at a too rapid rate, the system will clog, whereupon all 
flow ceases and the suction is lost. The conveying capacity rate of 
systems varies with factors such as moisture content of the material being 
conveyed, the atmospheric pressure, humidity, particle size and irregular 
product flow, as well as many other factors. Clogging can also occur with 
the momentary drop in air pressure within the system. This could be caused 
from a variety of reasons, including power failure or flow variations in 
the system. When pneumatic systems of this type become clogged or choked, 
the function of the blender fitting is to automatically dump the clogged 
material which has collected in the blender. Due to the weight of the 
clogged material, along with the lack of suction in the system, the relief 
gate will automatically open and dump all of the clogged milling stock in 
the blender and upstream thereof to the ground. Without the weight of the 
milling stock, the gate is so counterweighted that it will again close 
once the material has been dumped and the suction in the system will 
return since the point of clogging has now been removed. 
SUMMARY OF THE PRESENT INVENTION 
The blender fitting of the present invention eliminates this gradual 
leakage problem of the prior art blenders. This is accomplished by 
providing a channel-shaped relief gate which has side walls which 
substantially overlap with the side walls of the blender body to the 
extent that the inlet spout of milled material entering the blender body 
is below the upper edge of the relief gate side walls, thereby preventing 
any leakage in a relatively loose fitting negative pressure design. 
Another method of solving this leakage problem is to create an air-tight 
machined joint between the edges of the relief gate and the blender body, 
such as taught in the above mentioned Buhler blender. From a cost 
standpoint, precision made parts with machine edges cost substantially 
more to produce than the less expensive sheet metal design of the present 
invention. Applicant's blender body and relief gate are both constructed 
of fabricated steel sheet with a loose tolerance fit therebetween. In U.S. 
Pat. No. 3,198,584, the butt joint between door 28 and the edge of the 
blender body allows leakage whenever the pressure fluctuates. In the 
relief gate of the present invention, the product leakage is eliminated 
since the inlet spout enters below the side walls of the relief gate. The 
relief gate of the present invention also has a very compact, eccentric 
counterweight means which is adjustable to keep the gate closed under 
normal operating conditions and yet opens in the event of a clogging. When 
a conveying line is choked or an overload condition arises, the relief 
gate opens, dumping the milling stock until the line purges itself and is 
unplugged. The counterweight then returns the gate to the closed position. 
The positioning of the inlet conduit and spout directly over the relief 
gate prevents the stock from backing up at the spout, preceding the return 
of suction in the system. At the toe of the relief gate, there is a 
secondary fixed opening of air inlet which improves acceleration and lift 
of the product passing into the conveying line immediately downstream. 
Located at the upper end or heel of the relief gate is an adjustable 
butterfly valve which adjusts the amount of inlet air for equipment 
preceding the blender, such as rollstands, sifters, or purifiers, since 
each of these require varying amounts of air flow. Closing the valve 
diverts air to the equipment. This adjustable air inlet opening provides 
for improved acceleration of the milled product across the gate and 
therefore decreases the pressure drop across the entire blender fitting. 
Therefore, the principal object of the present invention is to provide a 
blender fitting which eliminates product leakage with a design which is 
simple and inexpensive to build, while providing an improved performance 
over the blender fittings of the prior art. 
Another object of the present invention is to provide a blender fitting 
which localizes the area of blockage in a pneumatic system and is capable 
of automatically relieving and correcting said blockage. 
Another object of the present invention is to provide a new blender fitting 
in a pneumatic system which provides improved air stream velocities 
therethrough to enhance its anti-clogging capability. 
Other objects and advantages of the blender fitting will become apparent to 
those skilled in the art upon reading this disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings, and specifically to FIG. 1, the negative 
pressure pneumatic system of the present invention is generally described 
by the reference numeral 12. The system 12 includes a vacuum producer in 
the form of a centrifugal fan or the like, not shown in the drawing, 
connected to vacuum suction conduit 54. The suction produced in the line 
54 draws air through the entire pneumatic system 12 which enters the 
system through blender fitting 10, the subject matter of the present 
invention. The milled product, such as flour, is initially stored in 
storage bin 50 or processed in a machine, and falls by gravity into the 
blender fitting 10 through inlet conduit 16. Blender fitting 10, shown in 
detail in FIGS. 2 and 3, provides an opening in the negative pressure 
system for sucking in atmospheric air through a variable air gap of 38, as 
best seen in FIG. 3. A secondary fixed air gap 36 is provided at the end 
of the relief gate 14 as best seen in FIGS. 2 and 5. The vacuum placed on 
the system draws air through the last mentioned gaps 38 and 36 which 
produce a high velocity and volume of air for transporting the milled 
product entering inlet conduit 16 through the entire system 12. At the end 
of the system, just upstream of the vacuum source, is a cyclone type 
separator 52 which separates the mill product from the air. Cyclone 
separators, well known in the art, basically swirl the air with the 
entrained material in a circular motion, causing the heavier milled 
material to move outward against the wall and settle in the bottom of the 
separator, while the lighter air is evacuated through conduit 54. The 
transported milled product can be withdrawn from the bottom of separator 
52 through a conventional airlock 62 by gravity flow. 
The negative pressure pneumatic system 12 of the present invention is used 
in the various milling operations since it is the most sanitary way to 
transport a milled material. They will transport the milled material 
through various runs of the system 12, including horizontal sections 56, 
elbows 64, vertical sections 58 and sightglass 60, before entering a 
cyclone separator 52 at the end of the line. The blender fitting 10, 
located basically at the beginning of the pneumatic system, performs two 
important functions, the first being controlling the volume of air moving 
through the system, and the second being a dump valve when the system 
clogs. While in the trade this fitting 10 is referred to as a blender 
fitting, it might likewise be called a dump valve in light of its 
automatic dumping function when the blender becomes clogged with milled 
material. These blender fittings have also been referred to as an 
"accelerator", a "pickup shoe", or a pneumatic boot. 
The blender valve 10 of the present invention includes a blender body 20 
positioned in a generally inclined angle with a vertically positioned 
inlet conduit 16 which passes through the planar top surface 30 of the 
blender body, as seen in FIG. 3, and extends downward into the body 20, 
terminating in spout 17. The blender body 20 further includes a 
horizontally positioned outlet conduit 18 of lesser diameter than the 
inlet conduit connected to the body through a transition section 19 while 
the bottom 28 of the blender body is open. Positioned in the open bottom 
28 is a relief gate 14 which is hingedly mounted by pivot pin 22 to the 
body 20 at its upper or heel end. Relief gate 14 is channel-shaped in 
cross-section with a bottom 15 and a pair of upwardly standing side walls 
26 and 27. The side walls 26 and 27 have upper edges 32. The side walls 26 
and 27 are tapered from their heel end of gate 14 toward the toe end 34 to 
provide a gradually decreasing interior cross-section area of the blender 
body, when the gate is in its closed position as seen in FIG. 2. The toe 
34 of the relief gate 14 has a slightly upturned bottom portion 35, as 
best seen in FIG. 3, to slightly deflect the high velocity air and 
entrained product as it reaches the end of the gate and flows out conduit 
18. Also adjacent the toe 34 of the gate is a fixed air gap 36 as seen in 
FIGS. 2 and 6. This secondary air gap 36 provides additional high velocity 
air which improves acceleration and lift of the product into the system. 
Located at the heel end of the relief gate 14 is a counterweight 46 
releasably held by a bolt 48 which passes through both side walls 26 and 
27. The counterweight 46 comprises an eccentrically mounted metal bar. By 
rotating counterweight 46 closer to or farther away from pivot pin 22, the 
closing moment on gate 14 can be adjusted for the particular application. 
Also positioned in the heel end of relief gate 14 is a damper means or 
damper valve 40 of the butterfly type which is rotatably mounted to the 
side walls 26 and 27 of the relief gate 14 on shafts 42 which in turn 
carry handles 44. Damper valve 40 has variable air gaps 38 on both sides 
thereof to regulate the amount of suction air which is transmitted into 
the system 12. Damper valve 40 can be adjustably positioned as illustrated 
in FIGS. 2 and 3 to vary the amount of air entering the system, depending 
upon the particular requirements of the system. With the gate 14 in its 
closed position, as best seen in FIG. 6, the spout 17 on the end of inlet 
conduit 16 extends below the upper edge 32 of the side wall 26 of the gate 
14. The spout 17 extends below the upper edge 32 of the side wall 27 with 
the gate 14 in its closed position. With the gate 14 in the closed 
position the upper edges 32 of the side walls 26 and 27 are in close 
proximity with the top surface 30 of the blender body 20. This particular 
geometry avoids the gravity leakage which takes place in other blender 
valves during operation and shut-down times. The tolerance fit between the 
blender body 20 and the relief gate 14 is quite loose as can best be seen 
in FIG. 6 wherein the side wall 26 completely overlaps the blender body 
side wall 24. The side wall 27 overlaps the blender body side wall 25. 
This overlap joint along the sides of the gate prevent any gravity leakage 
which might otherwise occur. The toe 34 of the gate 14 in its closed 
position extends slightly past the lower edge 29 of the blender body 20. 
The side walls 26 and 27 of the relief gate 14 in the closed position are 
located inside the side walls 24 and 25 of the blender body 20. 
OPERATION 
The counterweight 48 on relief gate 14 is adjustably positioned so that the 
closing moment provided by the counterweight provides enough moment to 
swing the gate 14 back to its closed position as seen in FIG. 2. Once 
milled material begins to build up in gate 14, the additional weight, if 
there is no air suction across the gate, would be adequate to swing the 
gate to its open position, as shown in FIG. 3, and dump the milled 
material collected both in gate 14 and inlet conduit 16. Once the milled 
material is fully dumped, the action of counterweight 46 will swing the 
gate 14 in a counter clockwise direction, as seen in FIG. 2, to its closed 
position. 
The amount of air passing through the pneumatic system 12 can be adjusted 
by damper valve 40. For example, if an increased amount of milled material 
is desired to be moved through the system, the air flow through the system 
can be increased and the damper valve 40 opened wider. One of major 
problems in pneumatic systems of the present type involves clogging of the 
conduits with the material being conveyed. This is caused by various 
factors such as moisture content of the milled material, atmospheric 
pressure, humidity, particle size, irregular product flow, as well as 
other factors. Clogging also is effected by drops in negative pressure 
within the system which can be caused by a variety of reasons, including 
the opening and closing of various valves in the system. The system 12 is 
designed so that clogging will first take place in the horizontal pipe 56 
and in the blender fitting 10 as the interior of blender body 20 begins to 
clog and fill the interior of the body. As this happens, the air flow 
ceases and the suction effect holding the gate 14 closed is lost and the 
weight of the milled material in gate 14 backed up in conduit 16 overcomes 
counterweight 46 and swings gate 14 to the open position as seen in FIG. 
3. This dumps all of the milled material backed up in the blender and 
inlet conduit 16, and once it is fully dumped, gate 14 will swing back to 
its closed position of FIG. 2 due to the counter clockwise moment of 
counterweight 46 and increased negative pressure acting on the gate 14. 
With the blender valve now unclogged, the system 12 is again ready to draw 
milled product through conduit 16 and air through gaps 38 and 36 as the 
system returns to its normal operating condition. 
While the invention has been described with a certain degree of 
particularity, it is manifest that many changes can be made in the details 
of construction and the changing of certain components without departing 
from the spirit and scope of this disclosure. It is understood that the 
invention is not limited to the embodiment set forth herein for purposes 
of exemplification, but is to be limited only by the scope of the attached 
claim or claims, including the full range of equivalency to which each 
element thereof is entitled.