US2835928A

US2835928A - Removing the outer skin from bark containing fibres

Info

Publication number: US2835928A
Application number: US543775A
Authority: US
Inventors: Johnson Philip Henry
Original assignee: SUDAN GEZIRA BOARD
Current assignee: SUDAN GEZIRA BOARD
Priority date: 1955-10-31
Filing date: 1955-10-31
Publication date: 1958-05-27
Anticipated expiration: 1975-05-27

Description

May 1953 P. H. JOHNSON 2,835,928

REMOVING THE OUTER SKIN FROM BARK CONTAINING FIBRES Filed Oct. 51, 1955 WEN inventor United States Patent Ofiice 2,835,928 Patented May 27, 1958 REMOVING THE OUTER SKIN FROM BARK CONTAINING FIBRES Philip Henry Johnson, Hounslow, England, assignor to The Sudan Gezira Board, Barakat, Sudan, a Sudanese body corporate Application October 31, 1955, Serial No. 543,775

3 Claims. (CI. 19-31) This invention relates to a process and apparatus for removing the outer skin from bark which contains useful fibres. Certain barks, for instance the bark of cotton stalks, contain an inner layer of useful fibres. The bark can be stripped from the stalks quite easily, but the bark itself is covered on the outside with a skin which adheres tenaciously to the underlying layer of fibres. The removal of the outer skin is particularly desirable when the fibres are to be subjected to a chemical retting process, because if the skin is present it adsorbs a substantial proportion of the chemicals used in the retting process. Thus, removing the skin affords considerable savings in the retting process. However, the removal of the skin without harm to the underlying layer of fibres has hitherto been difficult, and it is an object of the present invention to provide an improved process, and an apparatus suitable for carrying out this process, for removing the skin.

According to one aspect of the present invention, a process for removing the outer skin from bark containing fibres comprising drying the bark until the skin is in a brittle, crackable condition, subjecting the dry bark to a crimping process as hereinafter defined for cracking the skin into small pieces, and removing these pieces from the underlying fibres.

By the term crimping is meant the application of pressure to limited areas of the skin to such an extent that the skin is cracked in these areas, the applied pressure being such as not to damage the underlying fibres.

The crimping process may consist, for instance, of passing bark between rotating crimping rolls. Preferably the bark is passed successively between crimping rolls in at least two different directions to produce crossing cracks in the skin. This can be done, for instance, by passing the bark between the crimping rolls not only at right angles to the line of the nip but also in at least one direction which is oblique to the line of the nip. This produces a criss-cross formation of cracks.

Many of the small pieces of skin between the cracks become detached during the crimping, while the remaining pieces can easily be removed by other methods such as become clogged, as might occur if solid fluted rolls were used.

Preferably the rolls are geared together to rotate in opposite directions and so that the bars of one roll re main in the same relationship to the bars of the other roll.

It is desirable that the distance apart of the rolls should be adjustable so that the degree of crimping effect given to the bark can be adjusted to the point at which, though the skin is cracked, the underlying fibres remain undam aged.

One form of apparatus embodying the invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a side view of the apparatus partly in section; and

Figure 2 is a sectional plan view of the apparatus.

in the apparatus shown in the drawing two crimping rolls 10 and 11 are mounted in

bearings

12 and 13 respectively on a frame 14 with their

shafts

15 and 16 parallel, the positions of the bearings 13 being adjustable on the frame by means of adjusting screws 17 for the purpose of permitting adjustment of the distance between the rolls. The shafts have flats 18 on one end so that either of the shafts can receive a driving handle or a coupling for a mechanical drive. The rolls are geared together, through gearing comprising

spur gears

19 and 20,

sprockets

21 and 22 and a chain 23, so that they rotate at the same speed in opposite directions.

Each roll is of squirrel-case form and consists of two

end discs

24 and 25 mounted on the

shaft

15 or 16 as the case may be, between which extend parallel bars consisting of stretched wires 26 each provided with a screw tensioning device 27. In addition to the individual tensioning devices 27 all the wires of each roll can be adjusted collectively by providing a threaded tensioning sleeve 28 which when rotated relatively to the shaft adjusts the axial position of the disc 24 on the shaft, the sleeve 28 being constrained against axial movement on the shaft. If sufliciently taut, wires 26 of up to about a foot in length can be used without intermediate support. If longer rolls are required, intermediate supporting discs (not shown) may be provided.

In stead of bars consisting of tensioned wires 26, untensioned bars of a cross-section which provides suflicient rigidity may be provided.

In using the apparatus, dried bark is passed between the rotating crimping rolls 10 and 11 and the distance between them is adjusted by means of the screws 17 until the skin is effectively cracked but the underlying fibres are not harmed. When the correct adjustment has been achieved, dried bark can be passed between the rolls continuously, preferably at least three passes being made, either between the same pair of rolls or between different pairs of rolls. One pass may be at right angles to the line of the nip while the other passes may be oblique to this line in opposite directions, so as to produce a criss-cross formation of cracks on the bark. The bulk of the small pieces between these cracks will come away during the crimping, but any small pieces that may still remain can be removed by one of the methods mentioned above.

What I claim as my invention and desire to secure by Letters Patent is:

1. Crimping apparatus for producing cracks in the ski'nof dried bark in which said skin is in a brittle crackable condition, comprising two crimping rolls disposed with their axes parallel and means for rotating said rolls in opposite directions, said rolls each comprising two spaced end discs, wires extending between said end discs parallel with the axis of said roll and spaced from one another and means for maintaining the said wires in tension.

2. Crimping apparatus according to claim 1 in which each of said rolls include means for adjusting the distance between the end discs thereof.

3. Crimping apparatus according to claim 1 in which each of said wires is provided with an individual tensioning device. a

References Cited in the file of this patent 8 UNITED STATES PATENTS Wheaton Mar. 7, 1882 McBride Sept. 16, 1890 Schlichten Mar. 26, 1912 Lacroix Oct. 25, 1913 Colahan Aug. 12, 1915- Burkardt Nov. 19, 1937 FOREIGN PATENTS Great Britain Sept. 29, 1857 Great Britain Feb. 7, 1929 Great Britain Oct. 28, 1940