Screw feeder

A screw feeder is provided having a lower screw shaft and an upper drive shaft which are detachably connected to each other. The drive shaft includes an outer tubular member, with an inner, generally solid, connecting member positioned within the drive shaft. The lower end of the tubular member of the drive shaft includes a generally tapered recess which is adapted to mate with a lower end of the connecting rod positioned therein. The lower end of the connecting rod has a plurality of generally axially arranged slits which make the lower rod end flexible, with the lower end having a generally frustoconical outer surface. The upper end of the screw shaft is adapted to be attached to the lower end of the drive shaft by at least one annular member which engages one of the shafts. The annular member has two inwardly protruding pins, with the lower end of the drive shaft having a portion with two generally L-shaped opposed recesses which are adapted to engage the pins. An upper end of the screw shaft has a throughbore which is adapted to be aligned with two opposed holes in the annular member, in order to attach the annular member to the top of the screw shaft by inserting a truncated frustoconical pin therein.

DESCRIPTION OF THE INVENTION 
1. Technical Field of the Invention 
The present invention generally relates to a screw feeder which is adapted 
to be installed, e.g., in a bag producing, filling and packaging machine 
for transporting food, medicine or other products in a sanitary fashion. 
The present invention more particularly relates to a screw feeder which 
can be used with an apparatus having an outer pipe which is positioned 
vertically at the lower end of a hopper; wherein the screw feeder includes 
a screw shaft positioned in the outer pipe so as to transport, e.g., a 
particulate substance or a gel-like substance by rotating a driving shaft 
which is connected to the screw shaft 
2. Discussion of Background Information 
Conventional types of screw feeders, as noted above, have a screw shaft and 
a driving shaft, with a driving shaft end and the screw feeder base end 
being connected to each other along an axis by means of a screw. Each time 
the particulate substance or the gel-like substance to be transported is 
changed, or the amount of material fed at any given moment is changed, the 
screw can be loosened, and the screw shaft can then be separated from the 
driving shaft, so that the screw shaft can be replaced or cleaned. 
OBJECTS OF THE INVENTION 
However, when utilizing a conventional screw feeder as described above, 
because the screw shaft and the driving shaft are connected to each other 
by a screw, it is possible that the screw can become untightened and/or 
come off upon rotation of the two shafts. It is thus also possible for 
trouble to occur when the loosened screw is mixed into a particulate 
substance or a gel-like substance which is being transported. Additional 
problems arise in that, since the head of the screw can partially extend 
into the space between the hopper, the screw shaft and the driving shaft, 
a particulate substance or gel-like substance will likely stick around the 
screw; as a result, such screws have inferior sanitary properties. 
Further, in such a case, in order to turn the screw, it is necessary to 
move a tool into the hopper, with the resultant relatively low 
operability. In other words, it is difficult to rotate the screw (when 
necessary or desired) without an awkward placement of a tool into the 
hopper. 
It is, therefore, an object of the present invention to detachably connect 
a screw shaft and a driving shaft to each other without using a detachable 
screw. 
SUMMARY OF THE INVENTION 
In order to solve the above-noted problems, the present invention includes 
a driving shaft shaped in the form of a tube, with a connecting rod 
positioned within the tube. The connecting rod is provided for reciprocal 
movement along the axial direction of the driving shaft. The driving shaft 
also includes a recessed portion in which a base end of the screw shaft 
will be fitted, with the connecting rod having slit portions which divide 
a circumferential wall of a recessed portion thereof in a generally 
circumferential direction, the slit portions being formed in an axial 
direction at one end of the connecting rod. A frustoconical face portion 
is formed on an outer circumferential face of the circumferential wall of 
the recessed portion so that the diameter of the frustoconical portion 
will gradually increase, in a direction as viewed towards the screw shaft. 
Further, a tapered, frustoconical portion is formed, in opposed 
relationship to the frustoconical face portion, along an inner 
circumferential face of the driving shaft tube, in order to engage the 
frustoconical outer surface portion of the connecting rod, along the axial 
direction. 
In the present invention, if the base end of the screw shaft is pushed into 
the recessed portion, the connecting rod moves towards the screw shaft 
until the frustoconical surface portion and the tapered surface portion 
are no longer engaged with each other, but instead include a gap between 
them. In this case, the circumferential wall of the recessed portion of 
the connecting rod will expand so that the base end of the screw shaft 
will fit into the recessed portion; and, if the connecting rod is moved in 
an opposite direction in this situation, the frustoconical face portion 
will become engaged with the tapered portion to compress and tighten the 
circumferential wall of the recessed portion so that the driving shaft and 
the screw shaft wall are then attached integrally to each other. 
In a first aspect of the present invention, a screw feeder has an outer 
pipe and a hopper, with the outer pipe being positioned vertically below a 
lower end of the hopper. The outer pipe includes a screw shaft adapted to 
transport a substance in the hopper in response to rotation of a driving 
(i.e., drive) shaft which is connected to the screw shaft. The driving 
shaft comprises a tube, with a connecting rod being positioned on the 
inside of said tube, said connecting rod being adapted to reciprocate 
along the axial direction of the driving shaft. The driving shaft further 
comprises a recessed portion into which a base end of said screw shaft is 
positioned, with the connecting rod having slit portions which comprise 
means for dividing a circumferential wall of said recessed portion in a 
generally circumferential direction. The slit portions are formed in a 
generally axial direction at an end of said connecting rod, with a 
frustoconical face portion being provided along an outer circumferential 
surface of said circumferential wall of said recessed portion, wherein the 
diameter of said frustoconical portion gradually increases in a direction 
towards said screw shaft. A tapered portion is also formed, in opposed, 
generally complementary relationship to said frustoconical portion, along 
an inner circumferential face of said tubular driving shaft, said tapered 
portion being adapted to engage said frustoconical portion in an axial 
direction. 
In a second aspect, the present invention provides a screw feeder for 
feeding material in a hopper, the screw feeder including a driving shaft, 
a screw shaft, and means for detachably connecting one end of the screw 
shaft to one end of the driving shaft, wherein said connecting means 
includes a detachable connection means having elements which can be 
separably attached to both said driving shaft and said screw shaft. 
In yet a third aspect of the present invention, a screw feeder includes an 
elongated driving shaft having a first end and a second end, and an 
elongated screw shaft having a first end and a second end, said first end 
of said screw shaft being detachably connected to said second end of said 
driving shaft by a detachable connection, said screw shaft having a 
generally continuous screw positioned about its periphery, which screw is 
adapted to transport a substance located in a hopper or other container. 
The driving shaft comprises a tube, with a generally cylindrical connecting 
rod being positioned within said tube; and the screw feeder further 
comprises means for moving said connecting rod generally axially within 
said tube. 
The connecting rod includes a recessed portion at said second end, said 
recessed portion having a plurality of generally axial slits which 
separate a circumferential wall portion of said connecting rod into a 
plurality of substantially parallel circumferential portions. The recessed 
portion includes a generally frustoconical lower surface, wherein the 
diameter of said frustoconical lower surface portion gradually increases, 
in a direction towards said second end of said drive shaft. 
The first end of said screw shaft comprises a base end which is adapted to 
be inserted into said recessed portion, said first end of said screw shaft 
also comprising a tapered generally frustoconical portion which has a 
diameter which decreases in a direction towards said first end of said 
screw shaft. The tapered portion of said screw shaft is adapted to engage 
said frustoconical portion of said driving shaft. 
The screw feeder further comprises a pulley positioned adjacent an upper 
end of said driving shaft for transmitting power from a driving source to 
rotate said driving shaft and said screw shaft when said screw shaft is 
connected to said driving shaft; and the screw feeder can be used in 
combination with a hopper adapted to retain a particulate substance or 
gel-like substance, wherein said second end of said screw shaft is 
positioned within an upper portion of said hopper, and within a pipe 
connected to said hopper. 
The screw feeder can further comprise a nut adapted to engage an outer 
circumferential face of a second end of said connecting rod, said nut 
comprising rotatable means for moving said screw shaft axially via 
connection of said screw shaft with said connecting rod. 
The screw feeder driving shaft tube has a tapered inner portion with a 
minimum inner diameter which is substantially equal to a minimum outer 
diameter of a frustoconical lower portion of said connecting rod, said 
frustoconical lower portion and said tapered portion each having an angle 
of inclination which is substantially the same. The tapered portion of 
said outer tube has a length which is greater than the length of the 
frustoconical portion of said connecting rod; and a radial gap can be 
provided between the outer surface of said tapered portion and the 
frustoconical portion. 
The detachable connection for connecting said second end of said driving 
shaft to said first end of said screw shaft comprises at least one annular 
member adapted to surround one of said shafts. The threadless connection 
can comprise two generally annular members, with a first generally annular 
member being formed by a lower end of said driving shaft, said first 
annular member having opposed generally L-shaped slots at a lower end of 
said first annular member, and a second generally annular member having 
two inwardly projecting pins protruding radially inwardly from the inner 
peripheral surface of said second annular member, said two inwardly 
directed pins being adapted to be detachably engaged and retained by 
respective L-shaped slots. The second annular member comprises first and 
second opposed generally cylindrical openings which are adapted to be 
aligned with a generally cylindrical bore located in said first end of 
said screw shaft, said feeder further comprising an elongated locking pin 
which is adapted to be inserted through said opposed openings and said 
bore in order to position said second annular member on said screw shaft. 
The driving shaft includes an outer tubular member, with an inner 
connecting rod positioned inside the tube, said inner connecting rod 
comprising a generally solid cylindrical first member having a lower end 
with an opening extending therethrough, and a second member having a 
plurality of generally axially arranged slits, wherein a top end of said 
second member and a bottom end of said solid member are connected to each 
other by a generally frustoconical pin inserted into aligned openings in 
said solid member and said open tubular member.

DETAILED DESCRIPTION OF THE DRAWINGS 
Referring to the drawings in further detail, one embodiment of the present 
invention will be described with specific reference to the drawings. 
As shown in FIG. 1, a pulley P is provided along an upper portion of a 
driving shaft 1 which is formed in a cylindrical shape. Power from a 
driving source is transmitted by belt B to rotate driving shaft 1 and a 
screw shaft 2 which is adapted to be detachably connected to a lower end 
of the driving shaft 1, so that a particulate or a gel-like substance, 
e.g., in hopper 3 can be transported, in a fixed amount, through the 
spacing which exists between the screw shaft 2 and the cylindrical outer 
pipe 4. 
A connecting rod 5 is mounted for upward and downward reciprocating 
movement along the inside of a tubular portion of driving shaft 1; and a 
tapered inner surface portion 1a of the tube (see FIG. 2) is provided for 
engaging an outer frustoconical surface of a lower portion of the 
connecting rod 5, the tapered portion being formed on an inner 
circumferential surface of a lower portion of the driving shaft 1, so that 
the inner diameter of the tapered portion will gradually increase in a 
downwardly viewed direction. A nut 6, for engaging an outer threaded 
circumferential face 5f of an upper portion of connecting rod 5, is 
provided at an upper end of drive shaft 1. The nut can be rotated/turned, 
but cannot be moved either upwardly or downwardly. As shown in FIG. 2, an 
upper solid portion 5i of the connecting rod is attached to lower portion 
5g by a frustoconical locking pin 5h, which extends through aligned 
openings (unreferenced) in the two portions 
A recessed portion 5a of rod 5, having substantially the same diameter as 
base end 2a of shaft 2, i.e., the upper end of screw shaft 2, is provided 
axially at a lower end of connecting rod 5, while slits 5c, which divide 
circumferential wall 5b of recessed portion 5a into a plurality of axially 
extending portions, are axially provided at the lower end of connecting 
rod 5. A frustoconical surface portion 5d is formed along an outer 
circumferential surface of recessed portion 5a in opposed relation to the 
tapered portion 1a of the drive shaft, such that the outer diameter of the 
frustoconical portion gradually increases in a direction viewed 
downwardly. 
Tapered portion 1a and frustoconical surface portion 5d are formed so that 
the minimum inner diameter of the tapered portion 1a, and the minimum 
outer diameter of the frustoconical face portion 5d, are substantially the 
same; and so that the inclination angle of tapered portion 1a and the 
inclination angle of frustoconical face portion 5d are made substantially 
the same. This is achieved by forming the tube to have an inner diameter 
tubular portion 1b which is provided contiguously above the tapered 
portion 1a, which is adapted to slideably contact outer tubular portion 
5e, which is provided contiguously above conical face portion 5d. The 
outer diameter of the tubular portion 5e is substantially equal to the 
inner diameter of tube portion 1b, with a small (Vertical) gap between the 
ends of these sections (see FIG. 1) in order to permit upward and downward 
sliding movement. The vertical length of the tapered portion 1a in the 
upward and downward directions is made greater than the length of the 
conical face portion 5d in upward and downward directions, so that the 
maximum inner diameter of tapered portion 1a will be greater than the 
maximum outer diameter of frustoconical face portion 5d. 
Accordingly, when the maximum outer diameter position of the frustoconical 
surface portion 5d reaches the same height as the maximum inner diameter 
portion of the tapered portion 1a, during downward movement of connecting 
rod 5, a gap S is formed between the conical surface portion 5d and the 
tapered portion 1a in order to allow the circumferential wall 5b of 
recessed portion 5a to be expanded, due to the existence of slits 5c. 
Further, a threaded portion 5f, adapted to engage an inner circumferential 
face of nut 6, is provided on an outer circumferential face of an upper 
portion of connecting rod 5 (see FIG. 1); and threaded portion 5f is moved 
either upwardly or downwardly by operating/turning nut 6. 
Further, a temporary, i.e., detachable fastening mechanism 7 for driving 
shaft 1 and screw shaft 2, is provided at a lower end of driving shaft 1. 
The temporary fastening mechanism 7 comprises two annular members 2b, 1c, 
as shown in FIG. 3. Pins 7a of member 2b extend in a direction 
perpendicular to the direction of the axes of driving shaft 1 and screw 
shaft 2. Each pin is adapted to engage a corresponding recess 7b on member 
1c. 
Annular member 1c includes an internally threaded portion 7f, which is 
adapted to be threaded onto the exterior lower threaded portion of driving 
shaft 1 (see FIGS. 1 and 2). The lower annular member 2b includes two 
inwardly protruding locking pins 7a,7a, and two through holes 7g,7g which 
are diametrically aligned and which are adapted to receive a frustoconical 
locking pin 7h, which extends through holes 7g, 7g and through bore 2g in 
screw shaft 2, as shown in FIGS. 1 and 2. 
In the present invention, a pair of inverted L-shaped recesses 7b,7b are 
formed along a diagonal/diametric line in a circumferential wall of the 
lower portion of pipe body 1c, which pipe body is screwed onto a lower end 
of driving shaft 1 as shown in FIG. 3; and a cylindrical body 2b, adapted 
to be interfit, along the axial direction, with a lower end of pipe body 
1b, is securely mounted on an upper portion of screw shaft 2 by locking 
pin 7h. Horizontal pins 7a of member 2b, project inwardly along a diagonal 
line from an inner surface of a circumferential wall of cylindrical body 
2b, and towards recesses 7b,7b (when the driving shaft and screw shaft are 
attached). 
Subsequently, a method of mounting and detaching driving shaft 1 and screw 
shaft 2 will be described in detail. 
Initially, if nut 6 is manually turned so as to move connecting rod 5 
downwardly when the screw shaft 2 is not connected to driving shaft 1, 
then a gap S is formed between the frustoconical face portion 5d and the 
tapered portion 1a of shaft 1, as shown in FIG. 2. 
If, in this condition, base end 2a of screw shaft 2 is then inserted into 
recessed portion 5a, and pins 7a,7a are individually fitted into recesses 
7b,7b, whereafter screw shaft 2 is pushed upwardly, then the 
circumferential wall 5b of recessed portion 5a will be expanded so that 
the base end 2a is fitted along an inner circumferential surface of 
circumferential wall 5b. Further, if screw shaft 2 is then turned, pins 
7a,7a are individually moved in a circumferential direction along recesses 
7b,7b, are then engaged in an axial direction, and are temporarily 
fastened within the recesses. 
Thereafter, if nut 6 is turned manually so as to move connecting rod 5 
upwardly, conical face portion 5d will be moved upwardly via an upward 
movement so that it will be fit in a wedge-like fashion between the outer 
circumferential face of base end 2a of screw shaft 2, and the tapered 
portion 1a, as shown in FIG. 1; and screw shaft 2 and driving shaft 1 will 
be connected to each other by way of circumferential wall 5b of recessed 
portion 5a so that the "three," i.e., the screw shaft, driving shaft, and 
connecting rod, will be integrally connected to one another. 
Accordingly, if driving shaft 1 is then rotated, both connecting rod 5 and 
screw shaft 2 will be rotated so as to transport/move a particulate or 
gel-like substance which may be present in the form of a gel in hopper 3. 
Conversely, screw shaft 2 will come off of driving shaft 1 and connecting 
rod 5, and can be separated therefrom, if the above-noted procedure is 
followed in a reverse fashion. 
It should be noted that temporary fastening mechanism 7 need not be the 
only one which must necessarily be provided, and that the structure of the 
present invention is not necessarily limited to that which is shown in the 
attached drawings. 
With the above-noted structure, the present invention has numerous 
advantages over the prior art. Because when the base end of the screw 
shaft is pushed into the recessed portion in such a way that the 
connecting rod is moved toward the screw shaft, and the frustoconical face 
portion and the tapered portion are not engaged with each other but 
instead have a gap between them, then the circumferential wall of the 
recessed portion will be expanded so that the connecting rod will be 
fitted into the recessed portion of the drive shaft. Then, if the 
connecting rod is moved in an opposite direction, the frustoconical face 
portion will be engaged with the tapered portion so as to compress and 
tighten the circumferential wall of the recessed portion so that the 
driving shaft and the screw shaft will be integrated with each other, with 
the screw shaft and the driving shaft being removably connected to each 
other without using a screw. 
Accordingly, when compared to a conventional screw feeder in which a screw 
shaft and a driving shaft are connected to each other by a screw, the 
present invention avoids the problems of having the attaching screw 
loosening and coming off upon rotation, as well as avoids the problem of 
the screw being mixed into a particulate or gel-like substance which is 
being transported. As a result, the screw feed of the present invention is 
safer than that of the prior art. Additionally, no screw will fall between 
the hopper and the screw shaft, and the substance in the hopper will thus 
not likely stick to the screw, thereby improving the sanitary properties 
of the invention. No additional tools are needed to separate the drive and 
screw shafts, and the operation of the system will become enhanced. 
While the present invention has been described with respect to a specific 
embodiment thereof, other embodiments and features are contemplated which 
would be within the scope of the claims appended hereto.