GB2184936A - Grating device - Google Patents

Abstract

A grating device inter alia for grating manioc tubers or similar vegetables, comprises a hopper, a rotary drum 2 disposed at the bottom of the hopper and a pressing means 3 in the form of a halfshell having an approximately part-cylindrical surface 5 disposed at the bottom of the hopper opposite the drum. The generatrices of the surface 5 are parallel to those of the drum. Rods 9 and 12 articulated to the pressing means enable the latter to be pivoted towards and away from the drum. Screw means 14, 16 are provided for adjusting the space between the bottom edge 15 of the pressing means and the drum. The grating drum comprises a cylinder formed along its generatrices with a number of deep grooves 21 each holding a blade 22. The blades are secured in the grooves via two plates 24 having turned-down edges 25 disposed one at each end of the drum with the turned-down edges 25 covering the ends 23 of the blade. <IMAGE>

Description

SPECIFICATION Grating device The invention relates to the fragmentation of vegetable material, more particularly to a device for grating tubers ofmaniocorsimilarvegetables.

The purpose ofthe grating operation isto reduce tubers or roots to pulp. During the operation the product loses its structure and becomes a homogeous mass. The cell walls are broken, giving easier access to the constituents, inter alia starch. Manioc is grated mainly in processes for preparing products known as "farinha de mandioca" or "farinha de mesa" in Brazil, "couac" or" kuako" among the Amazonian and Guianese Indians, "gari" in Nigeria, Benin, Togo and Ghana, "attieke" in the Ivory Coast and "musseques" and "malanje" flour in Angola. Manioc also has to be grated to produce starch for food or industrial use.

In one traditional method of manual scraping, use is made of a galvanized or other metal sheet roughened with a nail and hammer. The indented side is used for scraping and the edges of the sheet are bent back if required. This method, in addition to a low flow rate, wastes considerable amounts of manioc since it is impossible to grate the end ofthe root. It is also difficult to clean the scraper, and this increases the risk of infection.

There are also a numberofexisting forms of rudimentary drum graters. These comprise a supply chute, or hopper, and a rotor. The chute can be above oralongsidethe rotor. The rotorcan be a wooden drum which, likethemanual grater,iscovered bya perforated galvanized-metal sheet and, as before, has the disadvantage of clogging. Alternatively the drum bears regularly-spaced toothed blades The latter version is the most suitableforefficient cleaning and maintenance.However existing rudimentary cylindrical graters cannot grate the entire product or adjust the fineness and particle size ofthe pulp, and have no satisfactory mechanism for pushing the roots against the rotor and regulating the flow rate.

An object of the invention isto propose a grating machine ofthe aforementioned drum kind which efficiently operates continuously, with a high constant flow rate, and can completely grate the entire product, whether wet or dry, to a given degree of fineness without risk of clogging.

An embodiment ofthe invention comprises a grating device intended interalia forgrating manioc tubers or similar vegetables, the device comprising a hopper, a cylindrical grating means or drum disposed at the bottom ofthe hopper, a pressing means in the form of a half-shell having an approximatelycylindric- al surface disposed atthe bottom ofthe hopper opposite the grating means, the generatrices ofthe shell being parallel to those ofthe grating drum, and the pressing means being pivotable around an axis parallel to the drum axis and disposed slightly out of vertical alignment therewith.

Preferably the pressing means has a cylindrical sealing surface or apron at its top, centred on the pivoting axis. A rod for pivoting the pressing means is joined thereto nearthe apron.

Preferably also, screw means are provided for progressively moving the drum towards or away from the pivoting axis. Thisfeature is for adjusting the fineness of the grating operation.

According to the embodiment also, the grating drum is a cylinder formed along its generatrices with a number of deep grooves, each holding a blade. The blades are preferably saw blades, e.g. hacksaw blades, and are secured in the grooves via two plates having turned-down edges each disposed at one end of the drum, the turned-down edges covering the ends of each blade.

The invention will be better understood and the detailswill beclearerfromthefollowing description of a preferred embodimentwith reference to the accompanying drawings, in which: Fig. is a diagrammatic section in a vertical plane through a grating machine; Fig.2 is a corresponding partial top view, and Fig. 3 is an illustration in longitudinal section of a grating drum as perthe previous drawings.

In Fig. 1 and/or 2, a grating device or machine comprises a hopper 1, a rotary cylindrical grating means 2 and means3for pressing tubers in the hopperagainstthedrumforgrating.

According to a feature ofthe device, means 3 comprise a pressing means 4 in the general shape of a half-shell having an approximately cylindrical surface 5. Means 4 is disposed at the botton ofthe hopper opposite the grating means. The generatrices of its cylindrical surface 5 are parallel to those of drum 2.

Means4 is pivotable around an axis or shaft 6 parallel to the drum axis 7. At its top it has a cylindrical sealing surface 8 or apron centred on axis 6.

An operating rod 9 is pivoted at 10 to the presser near apron 8. Rod 9 is also pivoted to the end of the short arm 11 of a lever 12 pivoted at 13 and operated e.g. by hand.

The shaft 6 on which presser4 pivots is held by a screw 14for bringing the bottom edge 15 ofthe presser nearthe grating surface. The screw engages in a threaded bearing 16 secured to a frame. As a result of this feature, the space between the bottom edge 15 and the grating surface can be gradually increased or decreased as required, so that the fineness ofthe grating operation can be accurately increased or reduced. The connection between shaft 6 and screw 14 is elastic (telescopic) so that foreign bodies which have not been ground can be removed in transit.

Fig. 3 shows a drum2 as in the preceding drawings, comprising a solid shaft 20to which a preferably plastics cylinder 17 is keyed, the cylinder periphery being formed with a number of radial grooves 21 (compare Fig. 1). Each groove holds a saw blade 22; the saw teeth have been ground atthe ends to leave a small straight part 23. The blades are held in the grooves by end plates 24 having a turned-down edge 25 covering the ground parts 23 ofthe blades. Plates 24 are held against the ends ofcylinderl7, e.g. by screws 26. As a result ofthis method of mounting the grating cylinder, the blades can be held on the drum without accurate adjustment and can be easily replaced. The drawing also shows the bearings 27 of shaft 20 and a drive pulley 28 in thecase where the drum is motor-driven.

Although only one preferred embodiment of the invention has been described and shown, it should be understoodthatthescope ofthe invention us not limited to this embodiment but extends to all devices comprising the aforementioned general features, taken separately or in combination.

Claims (10)

1. A grating device inter alia for grating manioc tubers or similar vegetables, the device comprising a hopper; a rotary grating drum disposed atthe bottom ofthe hopper, which grating drum comprises a cylinder formed along its generatrices with a number of deep grooves each holding a blade, the blades being secured inthe grooves via-two plates each disposed one at each end of the drum, and having turned-down edges covering the ends ofthe blades; a pressing means having an approximately part-cylindrical su rface d isposedat the bottom ofthe hopper opposite the drum, the generatrices ofthe part- cylindrical surface being parallel to those ofthe drum; means for pivoting the pressing means towards and awayfrom the drum about a pivot axis, and means for progressively moving the pressing means towards or awayfrom the drum.

2. A device according to claim 1, wherein the blades disposed inthe grooves are saw blades.

3. Adeviceaccordingtoclaim 1 or2,whereinthe pressing means has a cylindrical sealing surface or apron at its top, centred on the pivoting axis.

4. Adevice according to claim 1,2 or3, wherein said pivot axis is parallel to the drum axis and slightly out of vertical alignmenttherewith.

5. A device according to any one of claims 1 to 4, wherein said meansforpivoting the pressing means comprises rod means articulated thereto.

6. A device according to any one of claims 1 to 5, wherein said means for progressively moving the pressing means comprises a screw means.

7. A grating device substantiaíly as herein de- scribed with reference to the accompanying drawings.

8. A drum for a grating device, comprising a cylinderformed along its generatrices with a number of deep grooves each holding a blade, the blades being secured in the grooves via two plates each disposed one at each end ofthe drum, and having turned-down edges covering the ends ofthe blades.

9. A drum fora grating device and substantially as herein described with refernce to the accompanying drawings.

10. A grating device interaliaforgrating manioc tubers orsimilarvegetables, the device comprising a hopper; a rotary grating drum disposed at the bottom ofthe hopper, a pressing means having an approximate part-cylindrical surface disposed at the bottom ofthe hopper opposite the drum, the generatrices of the part-cylindrical surface being parallel to those of the drum; means for pivoting the pressing means towards and away from the drum about a- pivot axis, and means for progressively moving the pressing meanstowards or awayfrom the drum.