US2168075A - Compressing machine - Google Patents

Description

Aug. 1, 1939.

F. J. sToKEs coMPREssINq MACHINE Filed 0012.114, 1935 2 Sheets-Sheet 1 Aug- 1 1939 F. J. sToKEs 2,168,075

COMPRESSING MACHINE 2 Sheets-Sheet 2 Filed Oct. 14, 1935 Patented Aug. 1, 1939 UNITED STATES PATENT OFFICE COMPRESSING MACHINE Application October 14, 1935, Serial No. 44,906

This invention pertains to improvements in tablet-compressing machines and particularly to machines used in the manufacture of perforated tablets from pulverulent, granular or plastic material such as sugars, ceramics, Bakelite,

etc.

When producing tablets from materials containing reinforcing fillers, such .as asbestos fibres, etc., it is impossible to obtain the uniform lill required for the production of tablets having equal density throughout the run. This is particularly true when the mold--cell is partly obstructed by a hole-forming punch, hereafter referred to as the core-rod. Through my invention this handicap has been eliminated and the obstructing core-rodis made use of as the means for producing the needed agitation settling the material uniformly in the .mold-cell.

The difficulties recited above with fibrous materials are also present when attempting to manufacture tablets from pulverulent or finely divided powders. Such material not only produces tablets of varying density but capping also prevents the successful use of these types of machines vin tablet manufacture. By the term capping is to be understood the cracking or splitting of the tablet as it is being ejected after compression, caused by the re-expansion of the air trapped within the tablet. The agitation produced by vibration helps the air to escape and thus uniform lls are obtained and capping eliminated.

In general, the invention is embodied in a machine having a fixed frame and base with arrangement for the reciprocatio-n of a pair of opposed punches; a table fastened to the frame and provided with a recess and seat for the die and an aperture aligned with this recess, there being a corresponding aperture in the frame through which the lower punch reciprocates; an automatic material feeding device synchronized with the movement of the punches; and a core-rod supported on the base and extending up Vthrough -f the hollow center of the lower punch.l The masociation Aof parts in a preferred construction embodying my invention. The frame 30 may be fastened to a xed base 3 I, which rests on a suitable foundation 44. Table I8 is fixed to the frame 3U and mounted in` this is the die or mold I5. On top of table I8 and oscillating over die I5 is the usual feed shoe I 1, which conveys the material to be compressed from the feed hopper I6 to the mold-cell v2IJ. There is an upper punch II mounted in the usual reciprocating punch holder (not shown). A corresponding lower punch 22 is mounted in punch holder 23, which is slidably guided aty the punch end by an aperture in table I8 aligned with the die I5, and at the other end movably arranged in a sleeve 29 movable through an aperture in frame 30. The function of sleeve 29, its yieldable support 33, as well as the means (elements 26, 2'I and 28) for adjusting the position of punch holder 23 with respect to the desired charge of material to be compressed, is de'- scribed in U. S. Letters Patent No. 1,786,637, granted to me on December 30, 1930.

A `core-rod 2|, usually rigidly fixed to base 3| at 36, extends slidably through the hollow punch holder 23 and punch 22 a suitable distance into mold-cell 20 of die'l5. It is evident that corerod 2| forms a considerable obstruction in the mold-cell 20 whenl the charge is delivered, particularly if the material is stringfy or brous. Such a material has a tendency to hang up or bridgeV as it drops into thecell, causing voids in the charge with the result of varyingdensities in the tablets compressed. When attempting to compress pulverulentfmaterials, the air in the mold-cell is trapped under the charge and mixed or dispersedinlpthe fine powder being compressed Within thetablet as this is being made and as the pressure from the punches isV removed this:

compressed air expands, causing the tabletto flake or crack.

. Heretofore, the difficulty referred to above prevented the use of standardcompressors in the manufacture of tablets from fibrous material or fromi fine powders.

To overcome this difficulty, I vibrate the corerod and have found that this produces a very effective agitation and settling of the charge resulting in uniform lls and thus tablets of uniform density are obtained.

The vibration may be produced by any suitable means such as, for example, by means of an Yauxiliary vibrator suitably xed onto the corerod. While the oscillating feed shoe I4' may be subjected to vibration in addition to its oscillating motion and, while this vibration is helpful, it is not sufficiently effective on the material in the mold-cell to overcome the diiiiculties recited. A preferred method of construction is shown in the drawings, in which 40 represents a vibrator-body, such` as an electric vibrator, fixed to the core-rod 2| in any suitable manner, for example, by means of brackets 39 with holes threaded to iit on the end of the corerod. The vibrator may be locked securely in place by means of lock-nut 43.

Another type of vibrator which may be used consists merely of a hammer placed in a suitable position to pound on the core-rod, or on an anvil fixed to the core-rod, so as to impart vibrations to the core-rod. Y

Yet another type of vibrator susceptible of use is an eccentric or cam suitably mounted so that a lever actuated by the eccentricor cam would cause the core-rod to vibrate or oscillate. The frequency of Vibration depends upon the outline of the cam surface as well as the speed of the cam.

As mentioned above, the core-rod is usually rigidly iixed to some support, like 36 on the base 3|, but when using a vibrator it may be of advantage to give the core-rod some freedom so as to make it sensitive enough to reproduce the Vibrations imparted to it. This freedom or endplay of the core-rod may be obtained by some such arrangement of parts as shown where the core-rod is held in position by lock- nuts 34 and 38. This may be adjusted to support core-rod 2| at any desired height with relation to the face of die |5 and at the same time may be locked in place so as to give a suitable freedom or endplay to the core-rod. Should a resilient action be preferred, cushions or pads 35 and/or 31 of suitable shape and material can be provided.

One of the lock-nuts 38 has been made slightly longer than in the modification shown in Fig. 1 so as to act as an anvil 46. Against this anvil strikes the hammer 49 which is part of a lever fulcrumedat 50 and having one arm 5| actuated by a ratchet or toothed wheel 52. The lever is 'pressed against the teeth of the wheel 52 by means of a spring 41 extending between an extension. 48 of arm 49 and a pin 45 fastened to the base\of the press. The'toothed wheel 52 is fastened onthe shaft 53 with bearings in the base of the prss, and having at one side a pulley 54 driven through a belt 55 from one of the cam shafts (not shown) of the machine. The proportionsare such that, when the end of lever 5| drops off the top of a tooth, it imparts a blow on Vthe anvil 46, there being suflient clearance so that the lever end 5| will not touch the wheel at that point. The frequency of vibration depends, of course, entirely on the speed at which the toothed wheel 52 is operated. This speed, of course, is adjustable by the ordinary means of changing the drive.

It is to be understood that my invention is not to be limited save as the scope of the prior art and of the attached claims may require.

I claim:

1. In a tablet-compressing machine having a pair of co-operating punches mounted for movement towards and away from each other and having a mold located to receive the operating ends of said punches therein, a, xed part of said machine, a core-rod projecting through said fixed part and into said mold, lock-nuts adjustably securing said core-rod in said fixed part, and a vibrator rigidly secured to said core-rod for oscillating said core-rod to fill said mold uniformly and to produce tablets of uniform density.

2. In a tablet-compressing machine having a pair of cro-operating punches mounted for movement towards and away from each other and having a, mold located to receive the operating ends of said punches therein, a fixed part of said machine, a core-rod projecting through said fixed part and into said mold, cushions of resilient material interposed between said corerod and said xed part, lock-nuts bearing on said cushions and adjustably securing sair core-rod in said fixed part, and a vibrator rigidly secured to said core-rod for oscillating said core-rod to ll said mold uniformly and to produce tablets of uniform density. Y

3. In a tablet-compressing machine having a pair of co-operating punches mounted for movement towards and away from each other and having a mold located to receive the operating ends of said punches therein, a fixed part of said machine, a core-rod projecting into said mold and mounted on said xed part for limited movement relative thereto, and a vibrator for oscillating said core-rod to lill said mold uniformly and to produce tablets of uniformV density.

4.In a tablet-compressing machine having a pair of co-operating punches mounted for movement towards and away from each other and having a mold located to receive the operating ends of said punches therein, a iixed part of said machine, a core-rod projecting through said fixed part and into said mold, lock-nuts adjustably securing said core-rod in said fixed part, and a vibrator for oscillating said core-rod to fill said mold uniformly and to produce tablets of uniform density.

FRANCIS J. STOKES.

Images