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Title:
PELLET PRESS COMPRISING A SINGLE ROLLER
Document Type and Number:
WIPO Patent Application WO/2016/195484
Kind Code:
A2
Abstract:
The invention relates to a pellet press (1) with a supporting shaft (2) and a perforated drum mounted rotatably thereon via a drive member (8) having two spaced-apart bearings (9, 11). A single roller (15) is provided on the shaft within the drum. The first bearing (11) of the drive member (8) is a radial bearing, the second bearing (9) of the drive member (8) is an axial-radial bearing situated at a larger radial distance Bi from the drum rotation axis (6) than the radial bearing. An axially movable locking bushing (12) is placed around the shaft (2) between the bearing housings (10, 13) of the axial and the axial-radial bearings, the bushing (12) engaging both casings (10, 13).

Inventors:
BENTHUM, Martinus Antonius Julius (Langstraat 11, 5481 VN Schijndel, 5481 VN, NL)
CLEVEN, Arnold Peter Theodoor (Nachtegaallaan 15, 5692 PA Melderslo, 5692 PA, NL)
Application Number:
NL2016/050369
Publication Date:
December 08, 2016
Filing Date:
May 24, 2016
Export Citation:
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Assignee:
PELLETING TECHNOLOGY NEDERLAND B.V. (Duinweg 18, 5482 VR Schijndel, 5482 VR, NL)
International Classes:
B30B11/20
Domestic Patent References:
1998-04-30
Foreign References:
EP0238147A11987-09-23
CN201189726Y2009-02-04
CN201220163Y2009-04-15
DE29705321U11997-05-22
Attorney, Agent or Firm:
NEDERLANDSCH OCTROOIBUREAU (P.O. Box, 2502 LS The Hague, 2502 LS, NL)
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Claims:
Claims

1. Pellet press (1) comprising a supporting shaft (2) with a drum rotation axis (6), the shaft being fixed in a frame (4) at a shaft mounting side (3) and having at a roller supporting side (7) a roller shaft part, a roller (15) being rotatably mounted around a roller axis (16) of the roller shaft part, the roller axis (16) being situated parallel to and at a distance Δ from the drum rotation axis (6), wherein a drive member (8) is rotatably mounted on the shaft (2) via a first bearing (11) near the shaft mounting side (3) and second bearing (9) near the roller supporting side (7), the drive member (8) being attached to a perforated annular drum (5) coaxial with the drum rotation axis (6), for rotating the drum (5) around this axis (6), an inner drum surface (18) being situated near a roller outer surface (17), characterised in that a single roller (15) is provided , wherein an outer roller diameter (Dr) is larger than a radius (Rd) of an inner drum surface (18), the first bearing (11) being a radial bearing, the second bearing (9) being an axial-radial bearing that is situated at a larger radial distance Bi from the drum rotation axis (6) than the radial bearing, each bearing (9, 11) comprising a bearing casing (10, 13) and a roller member, an axially movable locking bushing (12) being placed around the shaft (2) between the bearing housings (10,13) of the axial and the axial-radial bearings, the bushing (12) engaging both casings (10, 13).

2. Pellet press (1) according to claim 1, wherein the axial-radial bearing (9) comprises a two-row spherical bearing.

3. Pellet press (1) according to claim 1 or 2, wherein the roller (15) is mounted on a bushing (20) around the roller shaft part, the bushing (20) being eccentric relative drum rotation axis (6) and can be fixed on the roller shaft part at different angular positions for changing the distance of the roller outer surface (17) from the inner drum surface(18).

4. Pellet press (1) according to any of the preceding claims, wherein the drive member (8) is formed of one piece.

5. Pellet press (1) according to claim 4,wherein the drive member (8) is formed of cast iron.

6. Pellet press (1) according to any of the preceding claims, wherein an axial distance (A) between the radial bearing (11) and the axial-radial bearing (9) is equal or larger than the distance (B) between the axial-radial bearing (9) and an axial mid position of the roller (15).

7. Pellet press (1) according to any of the preceding claims, comprising a product inlet at the roller supporting side (7) of the shaft (2).

8. Pellet press (1) according to any of the preceding claims, wherein the axial bearing (11) and the axial-radial bearing (9)have closed casings (10,13).

9. Pellet press (1) according to any of the preceding claims, wherein the roller (15) comprises a surface (17) having distributed thereon a number of cavities (19).

Description:
Pellet press comprising a single roller

Filed of the invention The invention relates to a pellet press comprising a supporting shaft with a drum rotation axis, the shaft being fixed in a frame at a shaft mounting side and having at a roller suspension side a roller shaft part, a roller being rotatably mounted around a roller axis of the roller shaft part, the roller axis being situated parallel to and at a distance from the drum rotation axis, wherein a drive member is rotatably mounted on the shaft via a first bearing near the shaft mounting side and second axial- bearing near the roller suspension side, the drive member being attached to a perforated annular drum coaxial with the drum rotation axis, for rotating the drum around this axis, an inner drum surface being situated near a roller outer surface Background of the invention

Such a pellet press is known from EP 238 147 and from WO 98/17464 both in the name of the applicant. In the known pellet press, a kneadable compound can be extruded as pellets by rotation of one or more rollers along an internal surface of a perforated drum. Either the known rollers or the drum rotate about the supporting shaft , and the material placed in the drum -such as for instance animal feed- is kneaded and forced through the apertures in the drum wall. In order to obtain the optimum roller setting, which depends on internal friction, humidity and the material which is being pelletized, the rollers may be driven so that they rotate about their axis. A distance between the rollers and the inside wall of the drum can be varied, to control the gap width between the internal surface of the drum and the roller by displacing the drum axis by means via a cam mechanism. For this purpose, a shaft extends along the drum axis from outside the drum into the pelletizing space. The shaft for driving the roller about the drum axis is formed by a second, hollow shaft which extends around the adjustment shaft and is mounted on bearings thereon.

From CN 201 189 726 a pellet press is known having a single roller and two axial-radial bearings engaging the central shaft at equal radial distances CN 201 220 163 discloses a pellet press using multiple rollers and having a spaced-apart axial and axial-radial bearing, situated at different radial distances around the central shaft. In the known devices in which multiple rollers are utilised in a symmetric arrangement around the drum axis, the large forces that during operation act on the rollers are balanced. This however results in a relatively complex construction and results in a time consuming exchange and maintenance procedure. Use of a single roller results in a simplified construction but results in a large concentration of forces which are accommodated by a more complex bearing structure.

It is an object of the present invention to provide a relatively simple pellet press which can be easily inspected and maintained. It is a further object of the invention to provide a pellet press which results in effective and controllable product treatment during the pelletizing process.

Summary of the invention Hereto a pellet press according to the invention is characterized in that a single roller is provided wherein an outer roller diameter is larger than a radius of an inner drum surface, the first bearing being a radial bearing, the second bearing being an axial-radial bearing that is situated at a larger radial distance from the drum rotation axis than the radial bearing, each bearing comprising a bearing casing and a roller member, an axially movable locking bushing being placed around the shaft between the bearing casings of the axial and the axial-radial bearing, the bushing engaging both casings.

By the use of a single, large size roller which is mounted at the free end of the supporting shaft, journalled in the spaced-apart axial bearing and axial-radial bearing, a stable construction is obtained which is easily accessible via the roller side of the pellet press for maintenance and inspection. The distance between the single roller and the drum wall can be rapidly and accurately adjusted in a simple manner, which results in good product quality of the products that are extruded through the apertures in the drum wall. Also the in feed of the device according to the invention can be situated at the roller side of the shaft, which is supported at the opposite side.

It is noted that a pellet press having a single large-size roller is also described in DE 297 05 321 Ul . In this document no details are given about the bearing construction and how the roller is mounted on the shaft.

In the pellet press according to the invention, the large radial forces resulting from the use of a single roller are accommodated by the axial-radial bearing, which may be a two- row spherical bearing. The axial bearing can be for instance a CARB bearing marketed by SKF in The Netherlands. By use of the axial and axial/radial bearings, the construction is kinematically determined and no internal forces can arise from temperature gradients and thermally induced expansion or contraction. By the use of the locking bushing, the bearings are easily mounted and released. Axial play may be removed from both bearing casings by exerting an axial force on the rearmost bearing (seen from the side of the drum) which force is transmitted to the foremost bearing via the axially movable locking bushing, resulting in accurate positioning of the two bearings. In the axial-radial bearing it is preferred to utilize a tight fitting in the housing and around the shaft in order to prevent the bearing rolling into the shaft.

In an embodiment of a pellet press according to the invention, the roller is mounted on a bushing around the roller shaft part, the bushing being eccentric relative to the roller shaft part and can be fixed on the roller shaft part at different angular positions for changing the distance of the roller outer surface from the drum. Easy adjustment of the gap between the roller and the drum surface results by rotation of the eccentric bushing around the shaft end part and fixing the bushing in the desired angular position that results in an controlled gap width.

The large forces acting on the drum are accommodated by forming the drive member in one piece from cast iron. A good load distribution on the bearings is obtained for an axial distance between the radial bearing and the axial-radial bearing that is equal to or larger than the distance between the axial-radial bearing and an axial mid position of the roller. For an optimal load distribution it is desirable to locate the rollers as close as possible to the axial/radial bearing and to have a large distance between the axial and the axial/radial bearing, whereas for compactness purposes both distances should be as small as possible. An optimal balance is found for the situation in which the inter-bearing distance is equal to or larger than the distance of the front bearing from the roller. In the pellet press according to the invention, a product inlet is situated at the suspension side of the shaft, for easy accessibility.

Both the axial bearing and the axial-radial bearing may have closed casings so that lubrication is only provided during mounting and no lubrication during operation has to be carried out.

In the pellet press of the invention it is preferred to provide a roller that comprises a surface having distributed thereon a number of dimples. The dimples may have the shape of a number of blind cavities, or holes and prevent a product film being formed flowing away in the gap between the roller and the drum surface.

An embodiment of a pellet press according to the invention will be explained in detail with reference to the accompanying sole drawing, that is shown by way of non-limiting example.

Detailed description of the invention

Fig. 1 shows a pelleting press 1 having a supporting shaft 2 with a shaft mounting side 3 supported by a machine frame 4 that has only been schematically indicated. The shaft 2 carries at a roller supporting side 7, a perforated drum 5 that is rotated around a drum rotation axis 6 via drive member 8. For providing a rigid construction, the drive member 8 is formed in one piece of cast iron. The drive member 8 is mounted on the shaft 2 via a two-row spherical bearing 9 having a casing 10 and an axial bearing 11 with a casing 13. The radial distance Bl of the axial- radial bearing 9 from the drum rotation axis 6 is larger than the radial distance B2 of the axial bearing 11. A bushing 12 locks both bearings 9, 11 in place and can be easily mounted around the drum rotation axis 6.

At the roller supporting side 7, a roller 15 is mounted on the shaft 2 to be rotatable around the roller axis 16 that is spaced at a distance Δ from the drum rotation axis 6. The roller 15 is driven by frictional engagement between the outer roller surface 17 and the inner drum surface 18 via the product that is squeezed in the gap between the roller and the drum. The diameter D r of the roll 15 is larger than the radius R d of the drum 5. A number of blind holes, cavities or "dimples" 19 is schematically shown in the outer surface 17 of the roller 15. A bushing 20 is mounted on the shaft 2 and is eccentrically movable around drum rotation axis 6. The roller 15 is supported via pairs of spherical bearings 22,23 on the bushing 20. The angular position of the bushing 20 sets the gap width between the outer roller surface 17 and the inner drum surface 18. The bushing 20 is fixed via conical clamping devices 25 that are locked front and back via two rings and two sets of bolts.

The distance A between the bearings 9, 11 is larger than or equal to the distance B between the bearing 9 and the center of roller 15.