Apparatus for compressing tablets

High-speed, rotary tablet-forming apparatus wherein dies are filled with product material to be compressed on one turntable and are thereafter transferred to one or more turntables where the said product material is formed into tablets between upper and lower punches. The dies are then returned to the filling table in a closed-loop arrangement. Vacuum is introduced under empty dies on the filling turntable to facilitate rapid filling and elimination of tablet capping and laminating. Further means are provided for direct-die lubrication, eliminating the need for incorporating a lubricant into the product itself, to further enhance cohesiveness of material being compressed and increase the life of the punches and dies involved.

BACKGROUND OF THE INVENTION 
As is known, conventional rotary tablet-making machines comprise a rotary 
turntable which carries near its periphery an annular series of die 
cavities in which the dies are clamped. Above and below the die turntable 
are upper and lower punches carried for rotation with the turntable, there 
being one upper and one lower punch for each die cavity. The heads of the 
punches may be guided by raising and lowering camming surfaces to control 
their reciprocating movements into or out of the die cavities as the die 
turntable rotates through filling, weight adjusting, compression and 
ejection stations all spaced around the single turntable. 
The production rate of a prior art machine of the type described above is 
limited by the diameter of the rotary die turntable and its speed of 
rotation. Furthermore, such presses have relied upon gravity feed of 
free-flowing materials in order to obtain uniform tablet weight, hardness 
and size. The gravity flow system often affects the mechanical production 
rate of the tablet press, the tablet weights, hardness, friability and 
resultant disintegration time. Furthermore, prior art tablet presses 
utilizing the aforesaid type die turntable generally require that a 
lubricant be mixed into the product to be compressed. This is sometimes 
undesirable and sometimes affects the ultimate efficacy of ingredients 
such as those found in pharmaceuticals, as well as requiring higher 
pressures to overcome the lack of cohesiveness caused by the addition of 
lubricant to the product itself. Prior art tablet presses also use 
close-tolerance bores to guide the upper and lower punches which are 
actuated by raising and lowering cams. Unless cleanliness and lubrication 
of the cams and punches are scrupulously observed, stickiness, gumming, 
binding and scoring of these parts occur; and the punches must be removed 
frequently for cleaning and relubricating. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, new and improved high-speed, 
tablet-forming apparatus is provided wherein filling of the dies occurs on 
one turntable, the filled dies being transferred to one or more other 
turntables where the product material is compressed into tablets by upper 
and lower punches. The turntables, which lie in an essentially common 
plane, rotate about parallel axes and are provided on their peripheries 
with generally semicircular notches for receiving and locating the dies. 
Apparatus in the form of idler wheels is provided for transferring filled 
dies from the filling table to the pressing table. After being 
transferred, the filled dies, carried in the aforesaid semicircular 
notches, travel around the axis of the pressing table; while upper and 
lower punch sets compress the product material in each die and eject the 
formed tablet. Continued travel of the dies in a pressing turntable brings 
them in succession to a second idler wheel where they are transferred back 
to the filling turntable. A plurality of pressing turntables, each 
provided with upper and lower punch sets, can be spaced around the filling 
turntable such that dies from one pressing turntable return to the filling 
turntable, then travel to a second pressing turntable and back to the 
filling turntable, and then travel to possibly a third pressing turntable, 
and so on. 
An important feature of the invention resides in the provision of means for 
creating a vacuum under the empty dies on the filling turntable during the 
filling operation. This facilitates faster filling than is possible with 
prior art gravity feed systems and, at the same time, acts to exhaust any 
entrapped air in the product material to be compressed, practically 
eliminating tablet capping and laminating due to air entrapment which may 
occur with conventional prior art presses. Beneath each of the dies on the 
filling turntable is a filter, the underside of the filter being connected 
to a vacuum pump. Before each die filling operation, the filter material 
underneath each die is purged with compressed air to clear the filter and 
prevent it from being clogged. Vacuum-assisted filling of the dies also 
makes lower punch dropaway unnecessary, without puffing material out of 
the die as the upper punch enters, since essentially no air is introduced 
into the die cavity due to the fill level being flush with the top of each 
die. 
Another important feature of the invention is the provision of means for 
injecting wall lubricant into each die before filling. This eliminates the 
requirement for mixing lubricant into the product to be compressed which, 
as explained above, is undesirable and sometimes affects the ultimate 
efficacy of the product. Furthermore, mixing a lubricant with the product 
material to be compressed usually requires more pressure from the press in 
order to form a cohesive tablet and increases the cost of the product 
because of the initial blending step required. Die wall lubrication of 
this type also reduces wear between the punches and the dies and also is 
more effective in facilitating tablet release from the dies at the time of 
ejection, resulting in less wear and better tablet finish. 
Instead of using cams for actuating the punches as in prior art machines, 
the present invention utilizes an inclined disc which rotates with the 
punches such that there is no relative movement between the punches and 
the disc. This reduces wear on both the actuating disc and the punches 
themselves. 
The present invention also eliminates the need for die-lock screws required 
by prior art machines. The dies are carried in notches spaced around the 
peripheries of the turntables along with flexible restraining cords. The 
punches are held in the same manner. This reduces the wall contact in 
guiding punches, simplifies inspection, and facilitates the use of 
spray-dry lubricants or wet-atomized fog applied while the machine is in 
operation. Removing and replacing punches and dies requires only a 
fraction of the time required with prior art machines.

With reference now to the drawings, and particularly to FIG. 1, the 
apparatus shown includes a frame 10 on which is mounted a main drive shaft 
12 connected through a pulley 14 and drive belt 16 to a drive motor, not 
shown, mounted on the frame 10 beneath the apparatus shown in FIG. 1. Also 
mounted beneath the apparatus shown in FIG. 1 is a vacuum pump. 
Drive shaft 12 carries at its opposite ends worms 18 and 20 which mesh with 
worm gears 22 and 24 carried on vertical shafts 26 which are mounted in 
bearings 30 for rotation about parallel axes. The shafts 26, in turn, 
carry pressing turntables 32 and 34 which, as shown in FIG. 3, are 
provided with generally semicircular notches 36 which receive 
tablet-forming dies, generally indicated by the reference numeral 38. 
Above and below the dies 38 carried on the turntables 32 and 34 are upper 
and lower sets of punches 40 and 42, respectively, These are adapted to be 
guided vertically and horizontally by an arcuate vertical wall portion of 
their respective pressure tables 32 and 34. The lower ball bearing thrust 
discs 46 and 48 are carried on bearing block 50 supported by the frame 10 
while the upper disc 44 is carried by a second bearing block 52 which can 
be adjusted upwardly or downwardly by screws 54 which are interconnected 
for synchronous movement by means of a chain 56. 
Also carried on the frame 10 is a third upstanding shaft 58 which carries a 
die filling platform 60 having die-receiving notches 62 FIGS. 2 and 3) 
which lie in essentially the same horizontal plane as the notches 36 which 
carry the dies 38 on the platforms 32 and 34. The shaft 58 is connected 
through pulleys 64 and 66 (FIG. 1) and belt 68 to the shaft 26. Pulleys 64 
and 66 are proportioned such that the rotational speed of the turntable 60 
is equal to that of the turntables 32 and 34, assuming that their 
diameters are the same. If the diameters of the turntables should not be 
the same, the dimensions of the pulleys 64 and 66 must be such that the 
circumferential speed of the platform 60 is equal to that of the platforms 
32 and 34. 
With specific reference to FIGS. 2 and 3, two idler wheels or sprockets 70 
and 72 are disposed between the turntables 60 and 32. Similarly, idler 
wheels 74 and 76 are disposed between the turntables 60 and 34. The idler 
wheels 72 and 74 serve to transfer dies from the filling turntable 60 to 
the forming turntable 32 or 34, and 70 and 76 from forming to filling 
table 60. In this respect, it will be noted from an examination of FIG. 3 
that when dies 38 on the turntable 60, for example, approach idler wheel 
74 and are essentially tangential thereto, they engage an arcuate guide 77 
which causes the dies to be transferred from the semicircular notches in 
turntable 60 to similar semicircular notches 78 in the idler wheel 74. 
They then travel around the axis of the idler wheel until they are picked 
up by the semicircular notches 36 in the turntable 34. 
Extending around the idler wheel 74 is a flexible band 80. As shown in FIG. 
2, the band 80 passes around the idler wheel 74, then around the idler 
wheel 82 and the idler wheel 84 where it engages the peripheries of dies 
38 carried on turntable 34. As shown in FIG. 4, the dies are provided with 
annular indentations or notches 86 into which the band 80 fits. This is 
perhaps best shown in FIG. 10. Similar bands 80 are provided for each of 
the three remaining idler wheels 70-76 as are idler wheels 82 and 84. 
With the arrangement shown, it will be appreciated that if all of the 
turntables 32, 34 and 60 rotate in clockwise directions, dies on turntable 
60 will be transferred by idler wheel 74 to turntable 34 where they are 
held in place within the semicircular indentations 36 by the flexible band 
80 until they reach an eject chute 88 which guides them to the band 80 for 
idler wheel 76. At this point, they are held on the periphery of the 
turntable 34 until they reach the idler wheel 76 where they are 
transferred back to the filling turntable 60. Once on the filling 
turntable 60, they are filled with product material during their advance 
through an arc of approximately 110.degree. where they engage the idler 
wheel 72 which transfers them to compression turntable 32 in the manner 
described above. The dies travel around turntable 32 in the same manner as 
they traveled around turntable 34 until they reach the idler wheel 70 
where they are transferred to the filling turntable, filled with product 
material, and then advanced to the idler wheel 74, whereupon the cycle 
repeats. Thus, each die travels in succession around a continuous 
closed-loop path of travel; and during its travel in one complete cycle it 
is filled twice and a tablet is twice formed and ejected therefrom. 
It will be appreciated that as the upper punches 40 travel around the axis 
of the turntable 32, they will engage the lower periphery of the disc 44, 
which forces them into the die cavities. Similarly, as the lower punches 
42 travel around the periphery of the turntable 32, they will be engaged 
by an arcuate segment of the disc 46 to force them upwardly into die 
cavities. 
A timing diagram showing the positions of the punches 40 and 42 as they 
travel around the turntable 32, for example, is shown in FIGS. 5 and 6. It 
will be noted from FIG. 5 that each of the punches comprises an upper 
barrel portion 90 having a curved head surface 92 adapted to engage the 
lower periphery of the disc 44, and a tapered transition portion 94 which 
merges into a stem 96 adapted to enter the cavity 97 formed in each of the 
dies 38. For the purposes of explanation, and to correlate the 
relationship between the dies in FIGS. 2, 5 and 6, the first die at the 
right side of FIG. 5 is identified by the reference numeral 38-8. By 
reference to FIG. 2, it will be seen that this die is carried by the idler 
wheel 72 intermediate the turntables 60 and 32. Movement of the dies in 
FIGS. 5 and 6 is from right to left; and it will be noted that the die 
38-22 shown in FIG. 5 is immediately adjacent the discharge chute 88 for 
the turntable 32. The positioning of the upper and lower punches 40 and 42 
beyond the discharge chute is shown in FIG. 6 where die 38-23 at the right 
side of FIG. 6, is just past the discharge chute 88 and die 38-37 has been 
picked-up by the idler wheel 70. Extending around the punches 40 is an 
arcuate bar 98 which is adapted to engage the tapered portion 94 on each 
punch and hold it in an elevated position. Similarly, a second arcuate bar 
100 extends around the lower punches 42 and is adapted to engage the 
tapered portion 94 on each of the lower punches 42 so as to pull it out of 
an associated die 38. As each punch is transferred from the idler wheel 72 
to the turntable 32, for example its tapered portion 94 will engage the 
upper surface of the bar 98 such that it is held in an elevated position 
until it reaches the location of die 38-14 shown in FIG. 5, at which point 
the bar 98 terminates. At this point, the head 90 of each punch is engaged 
by the lower periphery of the disc 44. Thereafter, the upper punches 40 
are forced downwardly into the cavities of the dies. At the same time, the 
lower punches 42, which are restrained by bar 100 at die location 38-8, 
are thereafter forced upwardly by the lower disc 46. At the approximate 
location of the die 38-11 shown in FIG. 5, the die cavity, which is filled 
with product material, receives the shank portion 96 of a lower punch 
which continues upward movement to approximately die location 38-13. Near 
this point, an adjustable scraper bar 104 scrapes off any excess powder 
and insures that a predetermined product material charge exists in the 
die. Thereafter, the upper punches 40 begin their downward movement while 
the lower punches 42 continue to move upwardly to compress the product 
material into a tablet which is finally ejected at die location 38-22 and 
deflected onto the exit chute 88 by a scraper or other means, not shown. 
At this point, the upper punches 40 are engaged by the other end of bar 98 
and held in their uppermost positions until they travel around the axis of 
the turntable (FIG. 6) to the location of die 38-14 shown in FIG. 5. At 
the same time, the lower punches 42 engage the bar 100 which curves 
downwardly so as to move the lower punches out of their associated die 
cavities preparatory to a succeeding compression stroke. 
With reference to FIG. 7, it will be noted that the barrel portions 90 of 
the upper and lower punches are carried within V-shaped or semicircular 
slots 106 formed in the back-up wall of the turntable 32 or 34 and are 
held in place by means of elastic or the like bands 108 and 110, best 
shown in FIG. 10. The bands 108 and 110 do not leave the turntable 32 or 
34 in contrast to the bands 80 which do and which engage the outer 
peripheries of the dies only as they move through a portion of the arcuate 
travel of an associated turntable. It can thus be appreciated that while 
dies are being loaded on the turntable 60, tablets are being formed on 
each of the turntables 32 and 34 with a resultant high production rate. 
Referring again to FIG. 1, above the filling turntable 60 is a rotating 
hopper 111 which contains material to be compressed and which has arcuate 
openings in its bottom surface extending approximately through the arcs 
112 and 114 shown in FIG. 2. Beneath the arcuate portions 112 and 114, as 
best shown in FIG. 4, is a circular filter cavity 116 which rotates with 
turntable 60 and is bounded at the top and bottom by perforated stainless 
steel plates 118 and 119. Beneath the plate 119 is a stationary plenum 
chamber 121 connected to the aforesaid vacuum pump, not shown, through a 
conduit 120. As the lower stainless steel plate 119 moves over the 
stationary plenum chamber 121, any air within the die cavities is drawn 
downwardly through the filter cavity, thence to the vaccum pump. During 
this time, die cavities are being filled from the hopper 111 with product 
material; and since the die cavities are evacuated during the filling 
operation, filling occurs faster than when gravity along is relied upon 
and most of the entrapped air in the product material to be compressed is 
exhausted. This substantially eliminates tablet capping and laminating and 
allows faster filling and compressing as explained above. The upper 
perforated stainless steel plate 118 will assist in retaining the major 
portion of the product material within the die cavities and act as wear 
plate support for the dies. However, some of the product material will 
inherently pass through the perforated stainless steel plate 118 and into 
the filter within cavity 116. Accordingly, in the arcuate portions 122 and 
124 shown in FIG. 2, and beneath the rotating filter cavity 116, is a 
separate stationary segment for forcing compressed air upwardly through 
the filter and cavity 116, thereby purging it of any finer particles 
entrained therein during the vacuum-charging operation just described. 
This purged product will be drawn off by the vacuum from the above table 
at this point. Clogging of the filter is, therefore, eliminated. The means 
for forcing compressed air upwardly may, for example, comprise a simple 
jet manifold segment which forces air upwardly through the lower 
perforated stainless steel plate 119. 
It will be appreciated that as the dies travel around the axes of idler 
wheels 72 and 74, they are filled with product material to be compressed; 
while those traveling around idler wheels 70 and 76 are empty. As the dies 
travel around the wheel 70 or 76, their internal peripheries are 
lubricated by an arrangement such as that shown in FIG. 8 where the idler 
wheel 76 is shown. A hopper 122, filled with a dry fine powder lubricant, 
is disposed above each of the idler wheels 70 and 76 and is provided with 
a nozzle 124 which sprays the lubricant into a chamber 126 above each of 
the idler wheels 70 the 76. From chamber 126, the lubricant passes 
downwardly through the die cavities to a lower chamber 128 where it is 
exhausted or is otherwise recovered. Lubrication of the internal 
peripheries of the dies in this manner eliminates the necessity for mixing 
a lubricant with the product material to be compressed with all of its 
attendant difficulties, as explained above. 
An alternative embodiment for lubricating this die is shown in FIG. 9. In 
this case, the idler wheel 76, for example, can be enclosed within a 
casing 134. Beneath the idler wheel is a fan 132 which sucks air 
downwardly through the die cavities and returns it upwardly through an 
annular passageway 134 formed by annular wall 136 surrounding the idler 
wheel. After passing upwardly through the passageway 134, the air then 
moves downwardly; however as it moves downwardly it picks up lubricant 
from a trough 138 and carries it through the die cavities. If desired or 
necessary, an auxiliary jet source of air under pressure passing through 
the pipes 140 can be utilized to blow the atomized lubricant from the 
trough 138 and entrain it within the downwardly-moving air. 
Although the invention has been shown in connection with a certain specific 
embodiment, it will be readily apparent to those skilled in the art that 
various changes in form and arrangement of parts may be made to suit 
requirements without departing from the spirit and scope of the invention. 
In this regard, it will be appreciated that a single forming turntable can 
be used with a single filling turntable; and that three or even four 
forming turntables can be spaced around a single filling turntable rather 
than the two shown herein.