WO2007010554A2 - A system for mounting feeder over a rotating die-table of tablet press and method thereof - Google Patents

A system for mounting feeder over a rotating die-table of tablet press and method thereof Download PDF

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Publication number
WO2007010554A2
WO2007010554A2 PCT/IN2006/000107 IN2006000107W WO2007010554A2 WO 2007010554 A2 WO2007010554 A2 WO 2007010554A2 IN 2006000107 W IN2006000107 W IN 2006000107W WO 2007010554 A2 WO2007010554 A2 WO 2007010554A2
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WO
WIPO (PCT)
Prior art keywords
feeder assembly
die
rotating die
mounting
feeder
Prior art date
Application number
PCT/IN2006/000107
Other languages
French (fr)
Other versions
WO2007010554A3 (en
Inventor
Jasjit Singh
Prakash Deshmukh
Sundaresh Naik
Original Assignee
Scitech Centre
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Scitech Centre filed Critical Scitech Centre
Publication of WO2007010554A2 publication Critical patent/WO2007010554A2/en
Publication of WO2007010554A3 publication Critical patent/WO2007010554A3/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B11/00—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses
    • B30B11/02—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses using a ram exerting pressure on the material in a moulding space
    • B30B11/08—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses using a ram exerting pressure on the material in a moulding space co-operating with moulds carried by a turntable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B30—PRESSES
    • B30B—PRESSES IN GENERAL
    • B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
    • B30B15/30—Feeding material to presses
    • B30B15/302—Feeding material in particulate or plastic state to moulding presses

Definitions

  • the present invention relates to a tablet press machine, particularly to a mounting of a feeder assembly of the tablet press.
  • a tablet press machine is used to fill the powdered medicament into a die of a particular shape to press into tablets.
  • a table press machine comprises a feeder assembly; a rotating die-table provided with peripheral dies; and series of upper and lower punches slidably fixed to the die-table and arranged to compress the product introduced in said dies.
  • the feeder assembly introduces the powder into the die pockets of the rotating die-table and said powder is pressed into a form of a tablet by the said upper and lower punches.
  • the rotating die-table carries the tabletting material such as medicament powder in the die pockets and cooperates respectively with the said lower and upper punches to form tablets.
  • the feeder assembly is located on the periphery of the die-table and said feeder assembly introduces the powdered medicament to the die by gravity.
  • the feeder assembly generally has an inlet duct, a rotating paddle placed at the lower end of the inlet duct; and a feeder shoe for receiving the powder from the rotating paddle and to introduce the powder into the dies on the rotating die-table.
  • the feeder assembly is generally heavy and fixed over the rotating die- table.
  • the feeder assembly is generally mounted at a fixed distance from the rotating die-table to avoid friction that may cause wear and tear of the under side of the feeder and the die-table. Generally, a clearance i.e. said fixed distance between the feeder and rotating die-table is required to be kept minimum in order to reduce powder loss from the feeder assembly and dusting.
  • the clearance of 0.02 to 0.05mm is maintained between the feeder assembly and the rotating die-table. Although, a minimum clearance is maintained, it is noted that considerable powder loss and dusting takes place during the tabletting operation. Further, the dusting may result in the jamming of the punches.
  • the feeder assembly is required to be removed frequently for cleaning, repairing and/or replacing of the feeder. Therefore, the adjustment of the feeder assembly to accurate clearance becomes a main criteria that consumes more time and also requires skilled labour to dismantle and reset the feeder assembly with clearance.
  • the powder loss can be reduced by minimizing the clearance between the feeder assembly and the rotating die-table.
  • the clearance is reduced, there occur friction between the feeder assembly and the rotating die-table, resulting in wear and tear of the machine thereby decreasing the life of the machine.
  • the inventors of the present invention observed that the major frictional loss takes place due to the weight of the feeder assembly if a zero clearance is maintained between the contacting surfaces of the feeder assembly and rotating die-table and also tablet press consumes more electric-power to rotate the die-table. Therefore, there is a need in the art for a tablet press that provides less powder loss during the process.
  • An object of the present invention is to provide a system for mounting a feeder assembly over the rotating die-table of the tablet press.
  • Another object of the present invention is to provide a tablet press that reduces the powder loss during tabletting operation.
  • the inventors solved the problem of reducing the powder loss during the feeding of the tabletting material such as medicament powder into the die pockets on the rotating die-table by maintaining a substantially 'Zero' clearance and substantially reducing the friction caused due to the weight of the feeder assembly by providing a mounting to said feeder assembly.
  • the present invention provides a system for mounting a feeder assembly over a rotating die-table of tablet press comprising a biasing force means positioned at center of gravity of the feeder compensating weight of the feeder assembly thereby enabling a substantially zero clearance between the contacting surfaces of the feeder assembly and the rotating die-table.
  • the system for mounting a feeder assembly over a rotating die-table comprises a resilient means positioned at the center of gravity of the feeder assembly, said resilient means exerts a force against the gravity force compensating weight of the feeder assembly; and a supporting member exerting a force in such a way the force is applied at the center of contact area between the feeder assembly and the rotating die-table thereby enabling a substantially zero clearance between contacting surfaces of the feeder assembly and the rotating die- table.
  • the system comprises three supporting members exerting force on the feeder assembly and positioned below the feeder assembly in such a way that resultant force is applied at the center of contact area between the feeder assembly and the rotating die-table. Further, one of the supporting members exerts force against the gravity or downward force of the feeder assembly and is adapted near the center of gravity of the feeder assembly.
  • said resilient means is a spring preferably compression spring and said supporting members are pneumatically or hydraulically operated cylinders exerting force on the feeder assembly.
  • the present invention provides a method for mounting a feeder assembly on a die-table of tablet press comprising steps of: mounting the feeder assembly on a resilient means at the center of gravity and above a rotating die-table; balancing weight of the feeder assembly by a force exerted by the resilient means; providing supporting member exerting a resultant force at the center of the contact area between the feeder assembly and the rotating die-table; wherein said forces allows to achieve a zero clearance between the contacting surfaces of the feeder assembly and the rotating die-table.
  • the present invention provides a rotary tablet press comprising a feeder assembly for feeding powder; a rotating die-table driven to rotate about its own axis and provided with peripheral dies; series of upper and lower punches slidably adapted to said die-table and arranged to compress the powder in the dies to produce tablet; and a system of the first embodiment of the present invention for mounting said feeder assembly over the rotating die-table to obtain a zero clearance between the contacting surfaces of the feeder assembly and the die-table.
  • the feeder assembly is mounted over the rotating die-table by a method of the second embodiment of the present invention.
  • a feeder shoe with a rim is provided on the underside of the feeder assembly to reduce the frictional area between die-table and feeder assembly.
  • Fig 1 shows a top view of a tablet press with a feeder mounted over a die- table with the help of mounting according to the present invention.
  • Fig 2 shows a perspective view of the feeder mounted over a die-table according to the present invention.
  • Fig 3 shows a cross section view of the tablet press with the cylinder mountings according to the present invention.
  • Fig 4 shows a perspective bottom view of the feeder shoe according to the present invention.
  • Figure 1 shows a rotary tablet press (100) having a feeder assembly (10) mounted on a rotating die-table (30).
  • the rotating die-table (30) is provided with peripheral die pockets (32) and series of upper and lower punches (34) as shown in Fig 3 slidably fixed to said rotating die-table (30) and arranged to compress the product introduced in said die pockets (32).
  • the feeder assembly (10) has a hopper (not shown) for introducing the powder to the inlet duct (12) of the feeder assembly (10); a rotating paddle (14) placed below the inlet duct (12) receives the tabletting material such as powdered medicament and a feeder shoe (16) placed below said rotating paddle receives the powder and feeds to the die pockets (32) on the rotating die-table (30).
  • the feeder assembly (10) mounted on a mounting system according to the present invention is shown in Fig 1 , 2 and 3.
  • the feeder assembly is first removably fitted on a plate (26) and the feeder assembly (10) is then mounted on the mounting system of the present invention.
  • a part of the feeder assembly (10) having the feeder shoe (16) as shown in Fig 4 is positioned outside the plate (26) to enable the feeder shoe (16) to be in contact with the die pockets (32) of the rotating die-table (30).
  • the mounting system comprises a biasing force means or resilient means (24) and at least three supporting members (22) (herein after referred to as cylinder/s) arranged and adapted to said plate (26).
  • the cylinders (22) and resilient means (24) exert force and enable to move the feeder assembly (10) to float in upward and/or downward direction in order to achieve a substantially Zero clearance between the feeder-shoe (16) of the feeder assembly (10) and the rotating die-table (30) along with compensating the weight of the feeder assembly (10) and said plate (26).
  • the resilient means (24) is a spring and preferably is a compression spring.
  • the compression spring (24) is preferably mounted at the center of gravity (CG.) of the feeder assembly (10) and exerts the force (F4) on the feeder assembly that compensates the downward force due to weight of the feeder assembly (10) with plate (26) acting on the rotating die-table (30) and also enables the movement of the feeder assembly (10) upwards by exerting an upward force (F4).
  • the compression spring (20) adapted at the center of gravity enables a weightless contact of the of the feeder assembly (10) with the rotating die table (30).
  • more than one spring/resilient means can be used and mounted away from the center of gravity of the feeder such that the resultant force of the springs/resilient means acts at the center of gravity of the feeder assembly.
  • a nut (25) is provided below the compression spring (20) for adjusting the upward force (F4) of the compression spring (20) in order to compensate the weight of the feeder.
  • Alternative arrangements can be used for adjusting the upward force of the resilient means such as hydraulically/pneumatically-operated cylinders to adjust the force (F4).
  • An up-stop limit (not shown) is also provided to the compression spring (20) to limit the travel of the compression spring (20) when feeder assembly (10) is removed for cleaning, repairing and/or replacing purpose.
  • One (22c) of the three cylinders (22) is preferably placed substantially near the compression spring (20) i.e. the center of gravity exerting a force (F3).
  • the cylinder (22c) exerts force (F3) in an upward direction thereby providing an additional upward force (F3) along with compression spring (24).
  • Remaining cylinders (22a) and (22b) are positioned away from the center of gravity exerting a force (F1) and (F2) respectively.
  • the cylinders (22a) and (22b) exerts the force downwards i.e. in the direction of the gravity, thereby moving the feeder assembly downward.
  • the cylinders (22) are positioned along with their forces F1 , F2 and F3 in such a way that the resultant force (not shown) of the cylinders is applied at the center (not shown) of the contact area of the feeder and rotating die-table thereby obtaining a prefect and substantial zero clearance between contacting surfaces of the feeder (10) and rotating die-table (30) along with a substantially zero weight of the feeder (10) on the rotating die-table (30).
  • less or more than three supporting members can be used to provide a resultant force at the center of contacting surfaces in order to provide a perfect and substantial zero clearance between the feeder assembly and rotating die-table.
  • the center of the gravity (CG.) is calculated for the feeder assembly (10) along with the plate (26) according to a principle method of the center of gravity.
  • a compression spring is provided on the press at center of gravity (CG.) of the feeder assembly (10) and the feeder is mounted on the compression spring (20) and over the rotating die-table (30). Tightening or lessening the said nut (25) of the compression spring, the pressure in the compression spring (20) is adjusted to compensate the weight of the feeder assembly (10) and allows feeder assembly (10) to float over the rotating die table (30).
  • three supporting member i.e. cylinders (22) operating on pneumatic pressure are adapted below the feeder assembly (10).
  • Cylinder (22c) exerting force (F3) in upward direction i.e. against the gravity of earth is adapted near the center of gravity (CG.) of the feeder assembly (10) and other two cylinders (22a & 22c) are adapted away from the center of gravity (CG.) exerting forces F1 and F2 respectively in downward direction.
  • the air pressure in each cylinder (22) is adjusted in such a way that the resultant force (not shown) of the forces exerted by the cylinders (22) on the feeder assembly (10) acts in downward direction and at the center (not shown) of the contact area (not shown) between the feeder assembly (10) and the rotating die-table (30).
  • the resilient means (24) i.e. compression spring can be replaced by any similar or suitable element performing a similar or substantially similar function i.e. compensating weight of the feeder assembly (10).
  • the cylinders (22) are operated on the pneumatic pressure -and the air pressure applied on the cylinders (22) is adjusted to minimize the vertical downward force acting at the center of the contact area of the feeder so as to maintain substantially zero clearance between the feeder assembly (10) and rotating die-table (30) with minimum friction.
  • the cylinders (22) are adapted below the plate using a resilient means to absorb the shocks.
  • the cylinders can be adapted above the feeder assembly in such a way that the resultant force acts at the center of contact area of the feeder assembly and the rotating die-table.
  • the cylinder may also be arranged using a link mechanism.
  • the resilient force exerted on the cylinder may also be adjusted using a pressure regulator.
  • the tabletting material is fed through the feeder shoe (16) of the feeder assembly (10) in the die pockets (32) of the rotating die-table (30).
  • the feeder shoe (16) is provided with a rim (17) on the underside of the feeder shoe (16) along the openings (18) as shown in Fig 4; said rim rest on the die-table (30).
  • the advantage of the invention is that it enables a substantially zero clearance between the feeder shoe of the feeder assembly and the die pockets of the die-table and minimizes the downward force of the feeder assembly at the center of the feeder contact area along with compensating the weight of the feeder assembly by the inventive mounting system that minimizes the wear and tear of the tablet press.
  • the feeder assembly which is heavy complex mechanical assembly to be removed and replaced on the machine without any necessity of setting a particular clearance value as there is a zero clearance between the feeder shoe and the die pockets.
  • the zero clearance achieved by the present invention solves the problem of tabletting material loss; dusting during the feeding of tabletting material into the die pockets of the rotating die-table thereby minimizes jamming of the punches.
  • the friction caused due the zero clearance is solved by the mounting system of the present invention that substantially reduces the friction caused due to the downward weight of the feeder assembly resulting in reduction in the maintenance cost of the rotary tablet press.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Medical Preparation Storing Or Oral Administration Devices (AREA)
  • Encapsulation Of And Coatings For Semiconductor Or Solid State Devices (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

Abstract

The present invention relates to tablet presses and preferably to mounting of a feeder assembly over a die-table of the tablet press. The present invention provides a system and method for mounting a feeder over a rotating die table of the tablet press that enable maintaining a substantially zero clearance between the contacting surfaces of the feeder assembly and the rotating die-table with reduction in wear and tear of the contacting surfaces of the feeder assembly and the rotating die-table by compensating weight of the feeder assembly.

Description

TITLE
A SYSTEM FOR MOUNTING FEEDER OVER A ROTATING DIE-TABLE OF TABLET PRESS AND METHOD THEREOF.
TECHNICAL FIELD
The present invention relates to a tablet press machine, particularly to a mounting of a feeder assembly of the tablet press.
BACKGROUND QF INVENTION
Conventionally, a tablet press machine is used to fill the powdered medicament into a die of a particular shape to press into tablets. Generally, such a table press machine comprises a feeder assembly; a rotating die-table provided with peripheral dies; and series of upper and lower punches slidably fixed to the die-table and arranged to compress the product introduced in said dies. The feeder assembly introduces the powder into the die pockets of the rotating die-table and said powder is pressed into a form of a tablet by the said upper and lower punches. The rotating die-table carries the tabletting material such as medicament powder in the die pockets and cooperates respectively with the said lower and upper punches to form tablets.
The feeder assembly is located on the periphery of the die-table and said feeder assembly introduces the powdered medicament to the die by gravity. The feeder assembly generally has an inlet duct, a rotating paddle placed at the lower end of the inlet duct; and a feeder shoe for receiving the powder from the rotating paddle and to introduce the powder into the dies on the rotating die-table. The feeder assembly is generally heavy and fixed over the rotating die- table. The feeder assembly is generally mounted at a fixed distance from the rotating die-table to avoid friction that may cause wear and tear of the under side of the feeder and the die-table. Generally, a clearance i.e. said fixed distance between the feeder and rotating die-table is required to be kept minimum in order to reduce powder loss from the feeder assembly and dusting. Typically, the clearance of 0.02 to 0.05mm is maintained between the feeder assembly and the rotating die-table. Although, a minimum clearance is maintained, it is noted that considerable powder loss and dusting takes place during the tabletting operation. Further, the dusting may result in the jamming of the punches.
Further, the feeder assembly is required to be removed frequently for cleaning, repairing and/or replacing of the feeder. Therefore, the adjustment of the feeder assembly to accurate clearance becomes a main criteria that consumes more time and also requires skilled labour to dismantle and reset the feeder assembly with clearance.
It is known in the prior art that the powder loss can be reduced by minimizing the clearance between the feeder assembly and the rotating die-table. However, if the clearance is reduced, there occur friction between the feeder assembly and the rotating die-table, resulting in wear and tear of the machine thereby decreasing the life of the machine. The inventors of the present invention observed that the major frictional loss takes place due to the weight of the feeder assembly if a zero clearance is maintained between the contacting surfaces of the feeder assembly and rotating die-table and also tablet press consumes more electric-power to rotate the die-table. Therefore, there is a need in the art for a tablet press that provides less powder loss during the process.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a system for mounting a feeder assembly over the rotating die-table of the tablet press.
Another object of the present invention is to provide a tablet press that reduces the powder loss during tabletting operation.
The inventors solved the problem of reducing the powder loss during the feeding of the tabletting material such as medicament powder into the die pockets on the rotating die-table by maintaining a substantially 'Zero' clearance and substantially reducing the friction caused due to the weight of the feeder assembly by providing a mounting to said feeder assembly.
According to the first embodiment, the present invention provides a system for mounting a feeder assembly over a rotating die-table of tablet press comprising a biasing force means positioned at center of gravity of the feeder compensating weight of the feeder assembly thereby enabling a substantially zero clearance between the contacting surfaces of the feeder assembly and the rotating die-table.
The system for mounting a feeder assembly over a rotating die-table according to the present invention comprises a resilient means positioned at the center of gravity of the feeder assembly, said resilient means exerts a force against the gravity force compensating weight of the feeder assembly; and a supporting member exerting a force in such a way the force is applied at the center of contact area between the feeder assembly and the rotating die-table thereby enabling a substantially zero clearance between contacting surfaces of the feeder assembly and the rotating die- table.
According to the present invention, the system comprises three supporting members exerting force on the feeder assembly and positioned below the feeder assembly in such a way that resultant force is applied at the center of contact area between the feeder assembly and the rotating die-table. Further, one of the supporting members exerts force against the gravity or downward force of the feeder assembly and is adapted near the center of gravity of the feeder assembly.
According to present embodiment of the invention said resilient means is a spring preferably compression spring and said supporting members are pneumatically or hydraulically operated cylinders exerting force on the feeder assembly.
In second embodiment, the present invention provides a method for mounting a feeder assembly on a die-table of tablet press comprising steps of: mounting the feeder assembly on a resilient means at the center of gravity and above a rotating die-table; balancing weight of the feeder assembly by a force exerted by the resilient means; providing supporting member exerting a resultant force at the center of the contact area between the feeder assembly and the rotating die-table; wherein said forces allows to achieve a zero clearance between the contacting surfaces of the feeder assembly and the rotating die-table.
In third embodiment, the present invention provides a rotary tablet press comprising a feeder assembly for feeding powder; a rotating die-table driven to rotate about its own axis and provided with peripheral dies; series of upper and lower punches slidably adapted to said die-table and arranged to compress the powder in the dies to produce tablet; and a system of the first embodiment of the present invention for mounting said feeder assembly over the rotating die-table to obtain a zero clearance between the contacting surfaces of the feeder assembly and the die-table. The feeder assembly is mounted over the rotating die-table by a method of the second embodiment of the present invention.
According to an embodiment of the present invention, a feeder shoe with a rim is provided on the underside of the feeder assembly to reduce the frictional area between die-table and feeder assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which:
Fig 1 shows a top view of a tablet press with a feeder mounted over a die- table with the help of mounting according to the present invention.
Fig 2 shows a perspective view of the feeder mounted over a die-table according to the present invention.
Fig 3 shows a cross section view of the tablet press with the cylinder mountings according to the present invention.
Fig 4 shows a perspective bottom view of the feeder shoe according to the present invention. DETAILED DESCRIPTION QF THE INVENTION
Figure 1 shows a rotary tablet press (100) having a feeder assembly (10) mounted on a rotating die-table (30). The rotating die-table (30) is provided with peripheral die pockets (32) and series of upper and lower punches (34) as shown in Fig 3 slidably fixed to said rotating die-table (30) and arranged to compress the product introduced in said die pockets (32). The feeder assembly (10) has a hopper (not shown) for introducing the powder to the inlet duct (12) of the feeder assembly (10); a rotating paddle (14) placed below the inlet duct (12) receives the tabletting material such as powdered medicament and a feeder shoe (16) placed below said rotating paddle receives the powder and feeds to the die pockets (32) on the rotating die-table (30).
The feeder assembly (10) mounted on a mounting system according to the present invention is shown in Fig 1 , 2 and 3. The feeder assembly is first removably fitted on a plate (26) and the feeder assembly (10) is then mounted on the mounting system of the present invention. Preferably, while mounting the feeder assembly (10) to the plate (26), a part of the feeder assembly (10) having the feeder shoe (16) as shown in Fig 4 is positioned outside the plate (26) to enable the feeder shoe (16) to be in contact with the die pockets (32) of the rotating die-table (30).
The mounting system according to the present invention comprises a biasing force means or resilient means (24) and at least three supporting members (22) (herein after referred to as cylinder/s) arranged and adapted to said plate (26). The cylinders (22) and resilient means (24) exert force and enable to move the feeder assembly (10) to float in upward and/or downward direction in order to achieve a substantially Zero clearance between the feeder-shoe (16) of the feeder assembly (10) and the rotating die-table (30) along with compensating the weight of the feeder assembly (10) and said plate (26).
The resilient means (24) according to the present invention is a spring and preferably is a compression spring. The compression spring (24) is preferably mounted at the center of gravity (CG.) of the feeder assembly (10) and exerts the force (F4) on the feeder assembly that compensates the downward force due to weight of the feeder assembly (10) with plate (26) acting on the rotating die-table (30) and also enables the movement of the feeder assembly (10) upwards by exerting an upward force (F4). The compression spring (20) adapted at the center of gravity enables a weightless contact of the of the feeder assembly (10) with the rotating die table (30). Alternatively, more than one spring/resilient means can be used and mounted away from the center of gravity of the feeder such that the resultant force of the springs/resilient means acts at the center of gravity of the feeder assembly.
A nut (25) is provided below the compression spring (20) for adjusting the upward force (F4) of the compression spring (20) in order to compensate the weight of the feeder. Alternative arrangements can be used for adjusting the upward force of the resilient means such as hydraulically/pneumatically-operated cylinders to adjust the force (F4). An up-stop limit (not shown) is also provided to the compression spring (20) to limit the travel of the compression spring (20) when feeder assembly (10) is removed for cleaning, repairing and/or replacing purpose. One (22c) of the three cylinders (22) is preferably placed substantially near the compression spring (20) i.e. the center of gravity exerting a force (F3). The cylinder (22c) exerts force (F3) in an upward direction thereby providing an additional upward force (F3) along with compression spring (24). Remaining cylinders (22a) and (22b) are positioned away from the center of gravity exerting a force (F1) and (F2) respectively. The cylinders (22a) and (22b) exerts the force downwards i.e. in the direction of the gravity, thereby moving the feeder assembly downward. The cylinders (22) are positioned along with their forces F1 , F2 and F3 in such a way that the resultant force (not shown) of the cylinders is applied at the center (not shown) of the contact area of the feeder and rotating die-table thereby obtaining a prefect and substantial zero clearance between contacting surfaces of the feeder (10) and rotating die-table (30) along with a substantially zero weight of the feeder (10) on the rotating die-table (30). Alternatively, less or more than three supporting members can be used to provide a resultant force at the center of contacting surfaces in order to provide a perfect and substantial zero clearance between the feeder assembly and rotating die-table.
According to the a method for mounting a feeder assembly on a die-table of tablet press, the center of the gravity (CG.) is calculated for the feeder assembly (10) along with the plate (26) according to a principle method of the center of gravity. Accordingly, a compression spring is provided on the press at center of gravity (CG.) of the feeder assembly (10) and the feeder is mounted on the compression spring (20) and over the rotating die-table (30). Tightening or lessening the said nut (25) of the compression spring, the pressure in the compression spring (20) is adjusted to compensate the weight of the feeder assembly (10) and allows feeder assembly (10) to float over the rotating die table (30). According to the present invention, three supporting member i.e. cylinders (22) operating on pneumatic pressure are adapted below the feeder assembly (10). Cylinder (22c) exerting force (F3) in upward direction i.e. against the gravity of earth is adapted near the center of gravity (CG.) of the feeder assembly (10) and other two cylinders (22a & 22c) are adapted away from the center of gravity (CG.) exerting forces F1 and F2 respectively in downward direction. The air pressure in each cylinder (22) is adjusted in such a way that the resultant force (not shown) of the forces exerted by the cylinders (22) on the feeder assembly (10) acts in downward direction and at the center (not shown) of the contact area (not shown) between the feeder assembly (10) and the rotating die-table (30). This resultant force and the compression spring allow to achieve a zero clearance between the contacting surfaces of the floating feeder assembly (10) and the rotating die-table (30) i.e. substantially weightless contact of the feeder assembly (10) with the rotating die-table (30). As the friction takes place between the feeder assembly (10) and the rotating die table (30) only due to the substantially zero clearance between contacting surfaces of the feeder assembly (10) and rotating die-table (30), wear and tear of the contacting surfaces of the feeder assembly (10) and the die-table (30) is substantially negligible.
According to the present invention, the resilient means (24) i.e. compression spring can be replaced by any similar or suitable element performing a similar or substantially similar function i.e. compensating weight of the feeder assembly (10). According to the present invention, the cylinders (22) are operated on the pneumatic pressure -and the air pressure applied on the cylinders (22) is adjusted to minimize the vertical downward force acting at the center of the contact area of the feeder so as to maintain substantially zero clearance between the feeder assembly (10) and rotating die-table (30) with minimum friction. The cylinders (22) are adapted below the plate using a resilient means to absorb the shocks. Alternatively, the cylinders can be adapted above the feeder assembly in such a way that the resultant force acts at the center of contact area of the feeder assembly and the rotating die-table. The cylinder may also be arranged using a link mechanism. The resilient force exerted on the cylinder may also be adjusted using a pressure regulator.
The tabletting material is fed through the feeder shoe (16) of the feeder assembly (10) in the die pockets (32) of the rotating die-table (30). According to another embodiment of the present invention, to achieve the object of zero clearance with minimum friction between the feeder shoe of the feeder assembly (10) and the rotating die-table (30), the feeder shoe (16) is provided with a rim (17) on the underside of the feeder shoe (16) along the openings (18) as shown in Fig 4; said rim rest on the die-table (30).
The advantage of the invention is that it enables a substantially zero clearance between the feeder shoe of the feeder assembly and the die pockets of the die-table and minimizes the downward force of the feeder assembly at the center of the feeder contact area along with compensating the weight of the feeder assembly by the inventive mounting system that minimizes the wear and tear of the tablet press. Further, the feeder assembly, which is heavy complex mechanical assembly to be removed and replaced on the machine without any necessity of setting a particular clearance value as there is a zero clearance between the feeder shoe and the die pockets. The zero clearance achieved by the present invention solves the problem of tabletting material loss; dusting during the feeding of tabletting material into the die pockets of the rotating die-table thereby minimizes jamming of the punches. The friction caused due the zero clearance is solved by the mounting system of the present invention that substantially reduces the friction caused due to the downward weight of the feeder assembly resulting in reduction in the maintenance cost of the rotary tablet press.
The other alternatives of mounting the feeder assembly to achieve zero clearance and minimizing the downward force of the feeder assembly using the mounting system of the present invention is also covered as an embodiment of the present invention.
While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.

Claims

1. A system for mounting a feeder assembly on a rotating die-table of tablet press comprising a biasing force means positioned at center of gravity of the feeder compensating weight of the feeder assembly thereby enabling a substantially zero clearance between the contacting surfaces of the feeder assembly and the rotating die-table.
2. A system for mounting a feeder assembly on a rotating die-table as claimed in claim 1 comprises
a resilient means positioned at the center of gravity of the feeder assembly, said resilient means exerts a force against the gravity force compensating weight of the feeder assembly;
a supporting member exerting force positioned below the feeder assembly in such a way that the resultant force is applied at the center of contact area between the feeder assembly and the rotating die-table thereby allowing to achieve a substantially zero clearance between contacting surfaces of the feeder assembly and the rotating die-table.
3. A system for mounting a feeder assembly on a rotating die-table as claimed in claim 2 said system comprises three supporting members exerting forces on the feeder assembly and positioned below the feeder assembly in such a way that resultant force is applied at the center of contact area between the feeder assembly and the rotating die-table.
4. A system for mounting a feeder assembly on a rotating die-table as claimed in claim 2 or 3 wherein one of the supporting members exerts an upward force.
5. A system for mounting a feeder assembly on a rotating die-table as claimed in claim 2 or 3 wherein said resultant force acts in a downward direction.
6. A system for mounting a feeder assembly on a rotating die-table as claimed in claim 2 wherein said resilient means is a spring preferably compression spring.
7. A system for mounting a feeder assembly on a rotating die-table as claimed in claim 2 or 3 wherein said supporting members are pneumatically operated cylinders.
8. A system for mounting a feeder assembly on a rotating die-table as claimed in claim 2 or 3 wherein said supporting members are hydraulically operated cylinders.
9. A method for mounting a feeder assembly on a die-table of tablet press comprising steps of:
mounting the feeder assembly on a resilient means at the center of gravity and above a rotating die-table;
balancing weight of the feeder assembly by a force exerted by the resilient means;
providing a supporting member exerting a resultant force at the center of the contact area between the feeder assembly and the rotating die-table; thereby achieving a zero clearance between the contacting surfaces of the feeder assembly and the rotating die-table.
10. A rotary tablet press comprising a feeder assembly for feeding powder; a rotating die-table driven to rotate about its own axis and provided with peripheral dies; series of upper and lower punches slidably adapted to said die-table and arranged to compress the powder in the dies to produce tablet; and a system for mounting said feeder assembly over a die-table as claimed in claim 1-5 to obtain a zero clearance between the contacting surfaces of the feeder assembly and die-table.
11. A rotary tablet press as claimed in claim 10 wherein feeder assembly is mounted on the die-table by a method as claimed in claim 9.
12. A rotary tablet press as claimed in claim 10 wherein a feeder shoe is with a rim is provided on the underside of the feeder assembly to reduce the frictional area between die-table and feeder assembly.
13. A substantially system for mounting a feeder assembly on a rotating die-table as herein described with reference to, and as shown in, the accompanying drawings.
14. A rotary tablet press substantially as herein described with reference to, and as shown in, the accompanying drawings.
PCT/IN2006/000107 2005-03-29 2006-03-28 A system for mounting feeder over a rotating die-table of tablet press and method thereof WO2007010554A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IN364MU2005 2005-03-29
IN364/MUM/2005 2005-03-29

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US949501A (en) * 1909-06-03 1910-02-15 Zeiss Carl Fa Spectacle-glass.
US4026658A (en) * 1974-07-26 1977-05-31 Barber-Greene Company Automatic support system for a screed
US4211082A (en) * 1978-10-11 1980-07-08 Bristol Robert D Internal combustion engine with free floating auxiliary piston
US6277407B1 (en) * 1998-11-10 2001-08-21 Frederick S. Marius Apparatus and method for tablet fabrication

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US949501A (en) * 1909-06-03 1910-02-15 Zeiss Carl Fa Spectacle-glass.
US4026658A (en) * 1974-07-26 1977-05-31 Barber-Greene Company Automatic support system for a screed
US4211082A (en) * 1978-10-11 1980-07-08 Bristol Robert D Internal combustion engine with free floating auxiliary piston
US6277407B1 (en) * 1998-11-10 2001-08-21 Frederick S. Marius Apparatus and method for tablet fabrication

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