The present invention relates to a method and an apparatus for manufacturing press molded bodies having at least two separate layers of material.
Manufacturing of briquettes (press-formed bodies of agglomerated particulate material) using roller compaction (briquetting) is a well-known manufacturing process, and briquetting presses for compacting particulate material in complementary cavities disposed about the peripheries of a pair of cooperating rollers have been in use for many years. The rollers are disposed horizontally and are rotated in opposite directions about vertically spaced axes, so that the peripheries of the rollers are disposed in substantial rolling contact with each other. Powder is then fed above the zone where the rollers come into closer contact, the powder being compacted in the nip defined by the facing cavities of the rollers.
Different systems for feeding particulate material into the nip of the rollers have been proposed. The simplest feeding system is a gravity hopper where powder is allowed to fall by gravity onto the required zone between the rollers. This method is simple but will only work adequately if the fed powder has a sufficiently high density and flowability. In case of lighter or less flowable powder it is necessary to effect a pre-compression of the powder being fed to deliver the same uniformly under constant pressure to the briquetting rollers to ensure the formation of consistent high quality briquettes.
To effect the pre-compression of particulate material or powder, feed screws have been proposed (U.S. Pat. No. 2,977,631 and U.S. Pat. No. 3,269,611). Alternatively, an axially reciprocating shaft disposed within a feeding funnel has been proposed (U.S. Pat. No. 4,389,178).
However, known briquetting machines are not well adapted for the manufacturing of briquettes or tablets made of two or more compositions, which remain physically separated in the briquette, i.e. in the form of separate layers.
Shaped bodies having separate layers of material have been manufactured in the past, an example of a solution for manufacturing two-layer shaped bodies being described in GB 2 332 387. Two independent feeding systems are provided for dosing the compositions into cavities of the rollers remotely from the nip of the machine. This process is only applicable to solidifiable liquid compositions or more generally to compositions that will cling to the cavities where they have been deposited when the cavities are moved into a vertical position shortly before forming the compaction nip. Thus, this solution cannot be used for briquetting free-flowing granular material.
Another solution for manufacturing press-shaped bodies is described in DE 1 230 523. In this specification, a rotary press machine is used for manufacturing tablets comprising different compositions incompatible with each other.
The object of the present invention is to provide an improved method and apparatus for manufacturing in an easy and cost effective way press molded bodies having at least two separate layers of material, starting from free-flowing granular or particulate material.
Accordingly, the present invention provides a method for manufacturing press molded bodies having at least two separate layers of material, comprising
Preferably, the particulate material is fed substantially vertically from above.
At least one of the separate streams can be fed by gravity.
At least one of the separate streams may be fed by a feeding device, for example a feeding screw.
It is preferred that a compact overall stream of particulate material having a total cross sectional area is fed, each separate stream forming part of the total cross sectional area.
Two separate streams having rectangular cross section may be fed.
Two separate streams can be separated from each other along a substantially vertical dividing plane parallel to the axes of the rollers.
By use of the term substantially horizontally we prefer that the rollers are within 10° of the horizontal.
At least one of the separate streams of material can be pre-compressed before entering the die means.
Preferably, the separate streams have different colours and/or different compositions and/or different granulometries.
In a further aspect, the invention provides an apparatus for manufacturing press molded bodies having at least two separate layers of material, in particular to be used in the method according to the invention, comprising
Preferably, the feeding means comprises a feeding hopper, the feeding hopper being divided along at least one substantially vertical plane that is parallel to the axes of the rollers.
Conveniently, the feeding hopper is divided by a substantially vertical blade of sheet material. By substantially vertical we mean that the blade is placed within 10° of vertical.
Preferably, the substantially vertical blade extends through all the height of the hopper.
Conveniently, the vertical position of the blade is adjustable.
Conveniently, the feeding hopper is divided into two halves.
Preferably, a pre-compressing means is provided for pre-compressing at least one of the separate streams before the same enters the die means.
Conveniently, at least one feeding device is provided for feeding at least one of the separate streams. At least one feeding screw can be provided inside the feeding hopper. Preferably, the at least one feeding screw tapers toward an open discharge end of the hopper.
Preferably, the feeding hopper has an open discharge end extending inwardly between the nip.
Other objects and advantages of the invention will become apparent from the following description and accompanying drawings in which:
Referring now to
A drive means (not shown) is provided for rotating the rollers in opposite directions indicated by arrows 8, 9.
A feeding hopper 10 is arranged vertically above the nip 3. According to the invention, a division is made in the hopper with a substantially vertically extending blade 11 of sheet material, the blade extending along the entire vertical height of the hopper 10. The orientation of the blade 11 can depart slightly from the vertical direction, e.g. within a range of +/−20°. An elongated slot-like discharge opening at a bottom end 14 of hopper 10 extends substantially over the axial length of the rollers in order to fill a plurality of axially adjacent cavities simultaneously.
By provision of the division in the hopper, substantially vertically extending flow channels are created through which two different granular materials (“A” and “B”) can be fed separately to the hopper as indicated by arrows 12, 13, and these two materials will flow by gravity towards the nip 3 in a substantially vertical flow. In the embodiment shown in
The claims which follow are to be considered an integral part of the present disclosure. Reference numbers (directed to the drawings) shown in the claims serve to facilitate the correlation of the integers of the claims with illustrated features of the preferred embodiment(s) but are not intended to restrict in any way the language of the claims to what is shown in the drawings, unless the contrary is clearly apparent from the context.
Number | Date | Country | Kind |
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0023055.7 | Sep 2000 | GB | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/GB01/04137 | 9/18/2001 | WO | 00 | 8/20/2003 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO02/24440 | 3/28/2002 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
2977631 | Komarek et al. | Apr 1961 | A |
3269611 | Komarek | Aug 1966 | A |
4389178 | Komarek | Jun 1983 | A |
5271319 | Plagemann | Dec 1993 | A |
5630202 | Bergendahl | May 1997 | A |
5935496 | Waatti | Aug 1999 | A |
6120802 | Breitenbach et al. | Sep 2000 | A |
Number | Date | Country |
---|---|---|
1230523 | Jan 1962 | DE |
2258580 | Jun 1974 | DE |
3806398 | Sep 1989 | DE |
0923875 | Jun 1999 | EP |
2332387 | Jun 1999 | GB |
Number | Date | Country | |
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20050035479 A1 | Feb 2005 | US |