Conveyor device for feeding lignocellulosic material to a disc-type grinding apparatus

• US 4,220,290 A
• Filed: 01/22/1979
• Issued: 09/02/1980
• Est. Priority Date: 01/24/1978
• Status: Expired due to Term

• Current Assignee: Defibrator AB
• Original Assignee: Defibrator AB
• Inventors: Johansson, Johan G. I.
• Primary Examiner(s): Rosenbaum, Mark
• Application Number:
  US06/005,378
• Time in Patent Office: 589 Days
• Field of Search: 425/207, 425/208, 425/209, 425/204, 198/662, 198/670, 198/676, 366/80, 366/81, 241/246, 241/247, 241/260.1, 241/277, 241/280, 241/261.2
• US Class Current: 241/247
• CPC Class Codes: B02C 7/11 Details

Abstract

Grinding apparatus in which lignocellulosic material such as wood chips is ground between a pair of grinding discs which rotate relatively to one another within a housing into which the material is advanced through a feed-in opening by means of a feed screw which rotates in a concentric sleeve extending between the central feed-in opening and an intake opening for the material. The feed screw comprises a series of inner screw flights mounted on a central shaft, which screw flights support and are enveloped by a series of outer ribbon-like screw flights. The inner screw flights are designed primarily to propel the material radially outwards towards the wall of the surrounding sleeve, whereas the outer ribbon-like screw flights are designed primarily to advance the material in an axial direction towards the central feed-in opening.

Claims

1. In a grinding apparatus in which lignocellulosic material is ground in a grinding space defined between a pair of grinding discs which are mounted on a shaft to rotate relatively to one another within a housing into which the material is advanced through a feed-in sleeve having a wall surrounding the shaft, from an intake opening to a feed-in zone, by conveyor means carried by said shaft to rotate within said sleeve, the improvement comprising:

(a) solid inner screw conveyor means mounted on said shaft;

(b) outer ribbon screw means supported on the crest of the flights of said inner screw means for common rotation therewith;

(c) said inner screw means having a pitch steeper than that of said outer screw means; and

(d) the flights of said inner means and said outer screw means being positioned relative to one another so that said inner screw means will propel the material mainly in a radially outward direction against the wall of said sleeve and fill the grooves of said ribbon-like screw means to be advanced axially by the latter in the form of a pipe into the feed-in zone during the common rotation of said screw means.

2. A grinding apparatus according to claim 1, in which the height of the crest of the inner solid screw means is greater than that of the outer ribbon-like screw means.

3. A grinding apparatus according to claims 1 or 2, in which the inner solid screw means comprises a greater number of screw flights than the outer ribbon-like screw means.

4. A grinding apparatus according to claim 1, in which said inner screw means are mounted on a cylinder concentrically enclosing said shaft.