US3016572A

US3016572A - Tabletting machines

Info

Publication number: US3016572A
Application number: US25045A
Authority: US
Inventors: Stott Frank Thomas
Original assignee: John Holroyd and Co Ltd
Current assignee: John Holroyd and Co Ltd
Priority date: 1959-05-21
Filing date: 1960-04-27
Publication date: 1962-01-16
Anticipated expiration: 1979-01-16

Description

Jan. 16, 1962 F. T. STOTT 3,016,572

TABLETTING MACHINES Filed April 27, 1960 4 Sheets-Sheet 1 FIG].

INVENTOR FRAN K THOMAS STOTT ATTORNEY Jan. 16, 1962 F. T. STOTT 3,016,572

TABLETTING MACHINES Filed April 27, 1960 4 Sheets-Sheet 2 FIG.4.

INVENTOR FRANK THOMAS STOTT ATTORNEY Jan. 16, 1962 F. T. STOTT TABLETTING MACHINES 4 Sheets-Sheet 3 Filed April 27, 1960 FIGS.

INVENTOR FRANK THOMAS SCOTT ATTORNEY Jan. 16, 1962 Filed April 27, 1960 F. T. STOTT 3,01

TABLETTING MACHINES 4 Sheets-Sheet 4 3 58 4 '5 29 as IE2 i. |9 13 D11 FIG.5.

INVENTOR.

FRANK THOMAS STOT'II' ATTORNEY.

3,016,572 TABLETTKNG MACHINES Frank Thomas Statt, 'Rochdale, England, assignor to John Holroyd 8: Company Limited, Milnrow, England Filed Apr. 27, 1960, Ser. No. 25,045 Claims priority, application Great Britain May 21, 1959 8 Claims. (Cl. 18-20) This invention concerns tabletting machines, that is to say machines for compressing powdered or granular materials into tablets which may be an ordinary tablet or a so-called layer tablet of two or more layers.

The invention is more particularly concerned with tabletting machines of the type (hereinafter called of the type described) including a rotary die table wherein are a plurality of dies, there being an upper and lower punch associated with each die and adapted to com-press material fed to the die.

Hitherto, it has been conventional to feed materials to the dies by means of a stationary feed frame, this being a skeletal or openwork frame which is disposed upon the die table, and a hopper which discharges into the feed frame. Thus, as the die table rotates, the dies pass successively under the feed frame and material in the frame falls, under the influence of gravity, into the dies.

Such prior arrangements have one important disadvantage.

The rate of flow of material to the feed frame depends directly upon the distance between the hopper outlet and the surface of the die table, and, therefore, it is necessary to prouide for vertical adjustment of the hopper in order to correlate the amount of material fed, to the rate at which it is taken up by the dies. This adjustment is very difficult, and in practice it is found that frequent resetting must be made.

One object of the invention is to provide a feed arrangement wherein the need to make this adjustment is eliminated, the arrangement serving to feed automatically sufiicient material to replenish that used by operation of-the machine, irrespective of the speed of output.

Another disadvantage of the prior described arrangement resides in the fact that it is essential for the feed frame to be open, so as to avoid the possibility of packing or compacting of the material in the feed frame, and to pass excess material to the next or back to the same feed frame and this results in free material finding its way onto the die table and into the other parts of the machine, so necessitating frequent cleaning and maintenance thereof. Similar disadvantages arise in prior known rotary-type feeders.

An additional object of the invention is to provide an arrangement which is substantially enclosed but wherein packing or compacting of the material is avoided, and from which escape of material except to the dies is eliminated, so that, in use, there is little or no loose or stray material on the die table. The die table remains clean and the necessary cleaning and maintenance of the machine is accordingly reduced considerably.

. With these objects in view, the present invention provides, in a tabletting machine of the type described, a material feed mechanism comprising a stationary housing disposed on the die table, there being, within the housing, a pair of vaned rotors (namely an input and metering rotor and an excess control rotor) which are rotatable about vertical spaced-apart axes with the vanes of the input/ metering rotor disposed at a higher level than and overlapping the vanes of the excess control rotor, the housing defining, around the rotors, a material feed chamber which provides, above the excess control rotor, a free space wherein is a guide disposed so as to direct any excess material which in use will be circulated in States Patent Patented Jan. 16, 1962 the free space above the excess control rotor by the latter, back to the input/metering rotor, there being an inlet in the top of the housing for feeding material to the input/metering rotor, one or more outlet apertures in the base of the housing, and means for rotating the rotors.

The vanes of each rotor are preferably radial, and there may advantageously be a single arcuate outlet aperture beneath the excess control rotor, and a plurality of apertures beneath the input/metering rotor.

Both rotors may conveniently be geared together and the arrangement may advantageously be such that the excess control rotor rotates at a slightly faster speed than the input/metering rotor.

The housing may, if desired, be mounted so as to be swingable about a vertical axis between its operative position on the die table and an inoperative position wherein it is clear of the die table, and the arrangement may advantageously be such that it will be swung to its inoperative position should it be engaged by an obstruction, such as a broken or dropped upper punch, on the die table. To achieve this, there may be spring-loaded retaining means for holding the housing in its operative position, there being an inclined surface, on the housing, so disposed that an obstruction as aforesaid will abut the inclined surface and swing the housing to the inoperative position, the spring-loaded retaining means permitting this.

In order that the invention may be fully understood, it Will be described further, by way of example, with reference to the accompanying drawings which illustrate one practical embodiment thereof as applied to a tabletting machine for making ordinary tablets.

In the drawings:

FIG. 1 is a fragmentary part-sectional side elevation of the tabletting machine showing the location of the feed mechanism thereon,

FIG. 2 is a fragmentary, part-sectional plan view corresponding to FIG. 1, with certain parts removed,

FIG. 3 is a cross-sectional elevation taken on line IIIIII of FIG. 1,

FIG. 4 is a crosssectional plan view taken on the line IV-IV of FIG. 3, and

FIG. 5 is a front elevational view of a complete molding app aratus.

The tabletting machine illustrated comprises a die table 10 (FIG. 1) rotatable about a vertical axis 11, there being a plurality of dies 12, of which one only is shown, in said table 10. Entering into each of said dies 12 from below the table is a lower punch 13, and guided in an annular flange 14 above the table 10 are a plurality of upper punches 15, one for each die 12.

Cams (shown diagrammatically at 16, 17 respectively) of known form are provided for moving the

punches

13, 15, as the die table 10 rotates, so as successively and sequentially to move the

punches

13, 15 towards one another to compress material in the dies 12 into tablet form, then to raise the upper punch 15 clear of the die table It) and simultaneously move the lower punch 13 to a raised position to eject the tablet, the lower punch 13 then lowering to receive a fresh supply of powdered or pulverulent material whereafter the upper punch 15 is lowered onto the material and the sequence of operations is repeated. The path of movement of the dies 12 is indicated at 12a in the various figures.

Adjacent the die table 19 and at the same level as the table 10 is a platform 18, carried by suitable stationary supports 19 secured to the machine frame, and this platform 18 incorporates a vertical pivot 20 on which is mounted a feed mechanism housing 21 which, in its operative position rests partly on the platform 18 and extends partly over the die table 10, as shown.

A vertical stud 22 (FIG. 3) projects downwards from the underside of the housing 21 and is accommodated in a slot 23 in the platform 18, there being a spring 24 on the stud 22 and biasing a tapered collar 25 into a shallow recess 26 associated with the slot 23, so as to maintain the housing 21 in its aforementioned operative position. The housing 21 can, however, be swung about its pivot pillar 20 to an inoperative position clear of the dietable It), in the direction indicated by arrow 27 of FIG. 4, by application of an external force thereto, and when this occurs, the tapered collar 25 rides out of the recess 26 and does not hinder the housing movement, although it will, normally hold the housing 21 in its correct operative position.

The housing 21 has a top 28 and secured to the top 28 of the housing 21 are two

vertical tubes

29, 39, these being spaced apart, and each enclosing a

drive shaft

31, 32 journalled in a suitable bearing 33, 34 in the top 28 of the housing 21. At their upper ends, these two

tubes

29, 39 enter a

guard

35, 36 which encloses

rotor gear wheels

37, 38 provided on the two

drive shafts

31, 32 respectively and a two-gear

intermediate train

39, 40 with which bout the

rotor gear wheels

37, 38 mesh. The guard has an opening in its upper part 36 and a driving gear 41, driven through a worm wheel 42 meshing with a worm 43 on shaft 44 of an electric motor 45 mounted upon a stationary machine part 4s above the die table 10, is carried upon a shaft 47 which projects into the opening to engage the driving gear 41 with the rotor gear Wheel 38. With this arrangement, movement of the housing 21 to its inoperative position just described disengages the driving gear 41 from the rotor gear wheel 38, and therefore arrests rotation of the

shafts

31, 32.

The

rotor gear wheels

37, 38 are chosen so that the shaft 31 is driven very slightly faster than the shaft 32.

Secured to the lower ends of the

shafts

31, 32 are two rotors, namely an input/metering rotor 47 and an excess control rotor 48, the latter being arranged on the shaft 31 which rotates at the faster speed. Each

rotor

47, 48 comprises a disc 47a, 48a having

radial vanes

47b, 48b projecting therefrom. T he input/ metering rotor 47 is disposed above the excess control rotor 48, and the

vanes

47b, 48b of these two rotors 47. 48 overlap one another.

The housing 21 defines, around these

rotors

47, 48 a material compartment 49. This compartment is shaped around the input/ metering rotor 47, so as to provide (except 'where the two rotors overlap) only a small clearance on all sides of the rotor 47. Thus, in the area of the input/metering rotor 47, the material chamber 49 is only very slightly greater in depth than the depth of the rotor 47.

In the region of the excess control rotor 48, the chamber 49 is of depth equal to the combined depth of the two

rotors

47, 48, the chamber 49 providing only a very small clearance at the ends of the vanes 4%, however. The chamber 49, is, thus, shaped to provide, above the excess control rotor, a free space occupied by the disc 48a of the excess control rotor 48 and, optionally a filling fillet 51 whose perimeter has been shown diagrammatically by shading in FIG. 4. Also provided in this free space is a deflector or guide 50 which is positioned so that any excess material which may enter the free space above rotor 48 whilst the

rotors

47, 48 are rotating will be guided towards the input/metering rotor 47.

The bottom of the housing 21 has a number of outlet apertures therein. Below the excess control rotor 48 is a single long arcuate aperture 52 and below the input/ metering rotor 47 are a plurality of apertures 53, 54, 55 separated from each other by narrow webs 56, 57.

Inthe top of the housing above the input/metering rotor is an inlet 58 the position of which is indicated in FIG. 4, this connecting with a material feed hopper whose position is indicated at 59 in FIG. 3.

In use, with the tabletting machine operating and the rotors '47, 48 being driven, powdered or granular 4 material to be tabletted is filled into the hopper 59, and passes by gravity or by agitation into the housing 21.

Rotation of the vanes 47b of the input/metering rotor 47 causes the material to be carried around the space occupied by such rotor. As the die table 10 rotates under the housing 21, the dies 12 are successively filled by powder which falls through the various outlet apertures 52 to 55.

The amount of material fed to the housing 21 does not have to be controlled. When no material is being fed to the dies 12, the space occupied by the input/metering rotor 47 becomes filled by the material from the hopper 59, and such material is continuously circulated by the rotation of the input/metering rotor 47 which keeps it in a constant state of movement.

Some of the material from the input/metering rotor 47 is transferred to the excess control rotor 48 and tends to build up above the vanes 48b of the latter, so that there is a small excess of material occupying the free space above the excess control rotor 48. This excess, however, is deflected back to the input/metering rotor 47 by the deflector 50 so that there is a constant recirculation of the material from and to the input/metering rotor 47, maintaining the space occupied by the latter constantly full so that no further material can enter from the hopper 59, and packing or compacting of the material is avoided.

When the dies 12 accept material from the outlet aperture 52 to 55, this results in reduction of the amount of material in the space occupied by the input/metering rotor 47, so that material will flow into the housing 21 automatically from the hopper 59 to compensate for the material being used.

The invention is not confined to the precise details of the foregoing example, which serves only to illustrate the invention in one practical form. The enclosed form of the housing 21 described reduces the possibility of loss or scattering of the tabletting material, and if desired suitable exhaust channels 68 (FIG. 1) and 61 (FIG. 3) may be provided in the platform 18 of the housing 21 particularly where this confronts the die table 10, except where the dies pass under the housing 12, these channels being connected to a suitable exhauster (not shown) so as to suck away any material which may possibly enter between the housing 21 and the die table 10.

The pivoted arrangement of the housing 21 permits it to be swung away from the die table 10, if desired, for cleaning or maintenance purposes, simultaneously disconnecting the drive to the rotors 4'7, 48. Should an upper punch 15 of the tabletting machine break or drop onto the die table It the housing 21 will be engaged thereby at the point 62 (FIG. 4) but with the described arrangement no damage will be done since the housing 21 is merely deflected in the direction of arrow 27 to its inoperative position.

As shown in FIG. 4, the housing 21 is provided with a rearward wall which inclines outwardly from its point of adjacency with the input/metering rotor 47 to its point of adjacency with the excess control rotor 48 thus presenting an inclined surface upon which the broken punch may ride, whereby the housing is deflected as described above.

'FIG. 5 illustrates a complete rotary molding apparatus with which the principles of the invention may be advantageously employed. Same is presented only that a better understanding of the invention may be obtained.

Since the various components of the molding apparatus are well known to the-art, further discussion thereof will not be made.

The invention can, of course, be applied to any form of tabletting machine having a rotary die table, and is not confined to the specific form described.

Thearrangement of the invention provides the following additional advantages, namely: there is more consistent filling of the dies as compared with prior known filling arrangements; the material is totally enclosed, thereby preventing contamination; higher outputs are possible; materials unsuitable for open feed frames can be handled; and it helps to eliminate separation of the granules, thereby assisting towards better tablet weight consistency.

I claim:

1. A tabletting machine including a rotary die table, a plurality of dies in said table, an upper punch and a lower punch associated with each said die, means for displacing said punches into their respective ones of said dies to compress material in said dies into tablets, and a feed mechanism for feeding said material to said dies, said feed mechanism comprising a stationary housing disposed on said die table, a vaned input/metering rotor disposed within said housing and rotatable about a first vertical axis, a vaned excess control rotor disposed also within said housing and rotatable about a second vertical axis spaced away from said first axis so that the vanes of said input/metering rotor are disposed above and overlap the vanes of said excess control rotor, said housing defining, around said rotors, a material feed chamber providing above said excess control rotor a free space, guide means in said free space for deflecting such material as may be disposed therein towards said input/metering rotor upon rotation of said excess control rotor, an inlet in said housing permitting tabletting material to be fed to said inlet/metering rotor, outlet apertures, in the underside of said housing, permitting material from said housing to pass to said dies in said die table, and means for rotating said rotors.

2. A tabletting machine including a rotary die table, a plurality of dies in said table, an upper punch and a lower punch associated with each said die, means for displacing said punches into their respective ones of said dies to compress material in said dies into tablets, and a feed mechanism for feeding said material to said dies, said feed mechanism comprising a stationary housing disposed on said die table, a vaned input/metering rotor disposed within said housing and rotatable about a first vertical axis, a vaned excess control rotor disposed also within said housing and rotatable about a second vertical axis spaced away from said first axis so that the vanes of said input/metering rotor are disposed above and overlap the vanes of said excess control rotor the vanes of both said rotors being radial, said housing defining, around said rotors, a material feed chamber providing above said excess control rotor at free space, guide means in said free space for deflecting such material as may be disposed therein towards said input/metering rotor upon rotation of said excess control rotor, an inlet in said housing permitting tabletting material to be fed to said inlet/metering rotor, outlet apertures, in the underside of said housing, permitting material from said housing to pass to said dies in said die table, and means for rotating said rotors.

3. A tabletting machine including a rotary die table, a plurality of dies in said table, an upper punch and a lower punch associated with each said die, means for displacing said punches into their respective ones of said dies to compress material in said dies into tablets, and a feed mechanism for feeding said material to said dies, said feed mechanism comprising a stationary housing disposed on said die table, a radially-vaned input/metering rotor disposed within said housing and rotatable about a first vertical axis, a radially-vaned excess control rotor disposed also within said housing and rotatable about a second vertical axis spaced away from said first axis so that the vanes of said input/metering rotor are disposed above and overlap the vanes of said excess control rotor, said housing defining, around said rotors, a material feed chamber providing above said excess control rotor a free space, guide means in said free space for deflecting such material as may be disposed therein towards said input/metering rotor upon rotation of said excess control rotor, an inlet in said housing permitting tabletting material to be fed to said inlet/metering rotor, at single outlet aperture in the underside of said housing beneath said excess control rotor, a plurality of arcuate outlet apertures in said underneath of said housing beneath said input/ metering rotor, said outlet apertures permitting material from said housing to pass to said dies in said die table, and means for rotating said rotors.

4. A tabletting machine including a rotary die table, a plurality of dies in said table, an upper punch and a lower punch associated wih each said die, means for displacing said punches into their respective ones of said dies to compress material in said dies into tablets, and a feed mechanism for feeding said material to said dies, said feed mechanism comprising a stationary housing disposed on said dio table, a radially vaned input/metering rotor disposed within said housing and rotatable about a first vertical axis, a radially vaned excess control rotor disposed also within said housing and rotatable about a second vertical axis spaced away from said first axis so that the vanes of said input/metering rotor are disposed above and overlap the vanes of said excess control rotor, said housing defining, around said rotors, a material feed chamber providing above said excess control rotor a free space, guide means in said free space for deflecting such material as may be disposed therein towards said input/metering rotor upon rotation of said excess control rotor, an inlet in said housing permitting tabletting material to be fed to said inlet/ metering rotor, outlet apertures, in the underside of'said housing, permitting material from said housing to pass to said dies in said die table, and means for rotating said rotors such that said input/metering rotor rotates at a faster speed than said excess control rotor.

5. A tabletting machine including a rotary die table, a plurality of dies in said table, an upper punch and a lower punch associated with each said die, means for displacing said punches into their respective ones of said dies to compress material in said dies into tablets, and a feed mechanism for feeding said material to said dies, said feed mechanism comprising a stationary housing disposed on said die table, a radially-vaned input/metering rotor disposed within said housing and rotatable about a first vertical axis, a radially-vaned excess control rotor disposed also within said housing and rotatable about a second vertical axis spaced away from said first axis so that the vanes of said input/metering rotor are disposed above and overlap the vanes of said excess control rotor, said housing defining, around said rotors, a material feed chamber providing above said excess control rotor a free space, guide means in said free space for deflecting such material as may be disposed therein towards said input/ metering rotor upon rotation of said excess control rotor, an inlet in said housing permitting tabletting material to be fed to said inlet/metering rotor, a feed hopper terminating at and connecting with said inlet, outlet apertures, in the underside of said housing, permitting material from said housing to pass to said dies in said die table, and means for rotating said rotors.

6. A tabletting machine including a rotary die table, a plurality of dies in said table, an upper punch and a lower punch associated with each said die, means for displacing said punches into their respective ones of said dies to compress material in said dies into tablets, and a feed mechanism for feeding said material to said dies, said feed mechanism comprising a stationary housing swingable about a vertical axis between an operative position disposed on said die table and an inoperative position clear of said die table, a vaned input/metering rotor disposed within said housing and rotatable about a first vertical axis, a vaned excess control rotor disposed also within said housing and rotatable about a second vertical axis spaced away from said first axis so that the vanes of said input/metering rotor are disposed above and overlap the vanes of said excess control rotor, said housing defining, around said rotors, a material feed chamber providing above said excess control rotor a free space,

guide means in said free space for deflecting such material as may be disposed therein towards said input/metering rotor upon rotation of said excess control rotor, an inlet in said housing permitting tabletting material to be fed to said inlet/metering rotor, outlet apertures, in the underside of said housing, permitting material from said housing to pass to said dies in said die table, and means for rotating said rotors.

7. A tabletting machine as set forth in claim 6 wherein said housing is provided with a rearward vertically-disposed wall adjacent said input/metering rotor and said excess control rotor, said rearward wall being angularized outwardly from its point of adjacency with said input/ metering rotor to its point of adjacency with said excess control rotorto present an inclined surface engageable by an obstruction on said die table to swing said housing to said inoperative position.

8. A tabletting machine as set forth in claim 7 further including spring loaded retaining means for holding said housing in its operative position, said spring-loaded retaining means comprising a stud depending from the underside of said housing being receivable in an aligned slot in a platform disposed below said housing, and having a spring disposed for biasing a collar into said slot, the action of said retaining means being overcome by engagement of an obstruction against said inclined rearward surface of said housing.

References Cited in the file of this patent UNITED STATES PATENTS 565,291 Meyers Aug. 4, 1896 2,481,101 Francis Sept. 6, 1949 FOREIGN PATENTS 818,450 Germany July 8, 1949