US 3323731 A
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June 6, 1967 P D ETAL 3,323,731
GRINDING APPARATUS PRIMARILY FOR LIGNOCELLULOSE CONTAINING MATERIAL 2 Sheets-Sheet 1 Filed June 22, 1964 June 6, 1967 J ASPLUND ETAL 3,323,731
' GRINDING APPARATUS PRIMARILY FOR LIGNOCELLULOS CONTAINING MATERIAL Filed June 22, 1964 2 Sheets-Sheet 2 V/l/ I. I .21 I
United States Patent 3,323,731 GRINDING APPARATUS PRIMARILY FGR LEGNO- CELLULOSE CONTAINEN G MATERIAL Arne Johan Arthur Asplund and Roif Ber-til Reinhail,
Lidingo, and Johan Gunnar Inge Johansson, Nasbypark, Sweden, assignors to Defibrator Aktieholag, Stockholm, Sweden, a corporation of Sweden Filed June 22, 1964, Ser. No. 376,779 Claims priority, application Sweden, July 1, 1963, 7,303/63 7 Claims. (Cl. 241-146) This invention relates to grinding apparatus.
More particularly this invention relates to a grinding apparatus, primarily intended for lignocellulose containing material and provided with two rotatable grinding dis-cs disposed within a casing and each co-operating with a stationary grinding disc, inlet and discharge channels for the material to be treated being provided in the casing for each pair of co-operating grinding discs.
A grinding apparatus of this type can be given the double capacity compared with that of an apparatus with one pair only of co-operating grinding discs.
One main object of the invention is to provide an improvement of this type of grinding apparatus, denominated also as double grinders so as to permit to adjust the two pairs of grinding discs to the same or different grinding pressures irrespective of whether the channels or the paths of flow pertaining to them are coupled in parallel or in series. 7
A further object of the invention is to provide an improvement of the grinding apparatus in consideration, which renders possible an adjustment of the grinding pressure between the two pairs of grinding discs from a position where only one pair is in operation to a position where both pairs are loaded equally, and to all conceivable intermediate positions between said limits.
Further objects and advantages of the invention will become apparent from the following description considered in connection with the accompanying drawings, which form part of the specification and of which:
FIG. 1 is a vertical longitudinal section through a grinding apparatus constructed according to the invention.
FIG. 2 is a sectional view of the central part of the apparatus with the paths of flow pertaining to the pairs of grinding discs coupled in parallel to one another.
FIG. 3 is the same sectional view but with the paths of flow disposed in series.
Referring to the drawings, reference numeral denotes a stationary base structure of the apparatus to which horizontally divided casings or housings 11, 12 and 13, 14 respectively, are connected. A shaft 16 passes through the casings and is at its one end mounted in a bearing 18 which preferably is of anti-friction or roller type and which is capable of absorbing beside radial thrust, also axial thrust in both directions. The two casings are separated from one another by a part 20 of the base structure 10, which on either side supports a stationary grinding disc 22, 24, respectively. Rigidly secured to the shaft 16 is a grinding disc 26 rotating with said shaft and which together with the stationary disc 22 forms a grinding interspace 28, through which the material to be disintegrated therein is passed in an upward direction.
The shaft 16 on the opposite side of the casings 11, 12 and 13, 14, viewed from the bearing 18, is concentrically surrounded by a tubular shaft 30 which is slidably supported by a radial thrust bearing 39, preferably a spherical roller bearing. Disposed between the shafts 16 and 30 are splines 34 so that said shafts are axially displaceable relatively to one another but rotate together, the outer shaft through a coupling 36 being connected to a driving motor (not shown). The shaft 30 carries a grind- Patented June 6, 1967 ing disc 38 rigidly anchored thereon and co-operating with the stationary grinding disc 24, a grinding interspace 40 being formed therebetween and through which the material to be treated is passed in a radial outward direction whereby this material becomes finely divided or disintegrated.
The material to be ground is supplied to the pairs of grinding discs 22, 26 through a channel 42 which may extend in the base part 20 to a central space 44 adjacent the inner faces of said grinding discs. The pulp ground between them is discharged through a channel 46. In the same manner, the other pair of grinding discs 24, 38 has a supply channel 48 in the base part 20 which opens into a space 50 formed centrally inside said grinding discs. The pulp ground between said discs is discharged through a channel 52. The channels 46, 52 are located in the casings '1-1, 12 and 13, 14 enclosing the grinding discs.
The parts of the radial and axial thrust bearing 18 not participating in the rotation are enclosed by a ring member 54 formed with a cylindric external face which is axially slidable on a corresponding formed face of a casing 56 rigidly secured onto the base structure 10. Connected to the ring member '54 is a disc 58 and to the latter a servo-motor piston 60 which has an outer annular flange 62 adapted to be displaced axially Within a prolongation 64 of the casing 56. Formed on either side of the flange 62 is a chamber 66, 68 respectively adapted to be connected to a pressure source or an outlet in a manner to be described later more in detail.
The supply of pressure fluid to the servo-motor 60, 64 is controlled by a pilot valve generally denoted and of the type known per se as is disclosed, for instance, by the patent specification No. 2,997,704. The pilot valve 30 is rigidly connected with the prolongation 64 of the casing 56 of the servo-motor 60, 62. The pilot valve includes a piston or valve body 82 formed with a central flange S3 and two lateral flanges 84, 85. The pilot valve 80 has a central chamber 86 and two lateral chambers 87, 88. Between the two lateral chambers 87, 88 and the central chamber 86, the inner diameter of the valve housing is reduced to correspond to the external diameter of the flanges. The flange 83 has an axial dimension which, by a small unit of measure, such as of one hundredth or a few hundredths of one millimetre, is shorter than the length of the chamber 86. In the same manner the flanges '84, have an axial dimension which is only slightly less than the length of the chambers 87, 88. In the middle position all flanges are positioned right in front of their pertaining chambers.
A pipe 89 connects the central chamber 86 of the pilot valve with an oil sump 90, a pump 91 being provided in this pipe and a spring-loaded valve 93 in a return pipe 92 connected to said pipe 89. From a space 94, having the reduced diameter corresponding to that of the flanges of the valve body 82 and located between the chambers 86 and 87 of the pilot valve 80, a pipe 95 extends to the chamber 68 on one side of the flange 62 of the servomotor. A pipe 96 connects a space 97 with the same reduced diameter of the pilot valve located on the other side of the central chamber 86 with the chamber 66 on the opposite side of the flange 62. Through a return pipe 98 the lateral chambers 87, 88 are in open connection with the sump 90.
An adjustment screw 100 is passed through a threaded passage in an arm 99 fixed to the servo-motor piston 64 said adjustment screw being coaxial with the valve body 82 of the pilot valve and adapted to act on the facing end of said valve body projecting from the valve casing. The other end of the valve body 82 is under the load of a spring member 101 tending always to keep the valve body pressed against the adjustment screw 160.
Another pilot valve 102 has for its object to control the supply of pressure fluid to the servo-motor 70, 72. This pilot valve is of the same construction as the pilot valve 80. In FIG. 1 the same reference numerals have been used for both servo-motors with the addition of a sufiix for the pilot valve 102. The casing thereof is fixed in the base structure 10. The arm 104 carrying the adjustment screw 100 is fixed in a ring member 106 surrounding the nonrotating part of the bearing32. The ring member 106 is axially displaceable within a surrounding stationary outer casing 180 and due to this feature follows the shaft 30 in the axial movements thereof.
Extending from the chamber 94 of the pilot valve 102 is a pipe 110 which is extended to the outer end of the hollow servo-motor piston 60 and here connected to a pipe 112 extending through the piston 60 and the shaft 16 to the chamber 78.
As shown in FIG. 2 the grinding apparatus may be adjusted so that the both pairs of grinding discs 22, 26 and 24, 38, respectively, operate in parallel with two fractions of pulp or material to be ground. The one fraction or stream of pulp is introduced through the channel 42 and the chamber 44, and passes radially outwards between the grinding discs 22, 26 while a disintegration of fibre bundles or fibres is effected. The ground pulp is discharged through the outlet 46. The other fraction or stream of pulp passes through the channel 48, the chamber 50, and the interspace between the discs 24 and 38 and is discharged through the outlet 52. In the two fractions the quality of the material to be treated may be dilferent prior to and/ or after the grinding operation depending on the conditions.
Disposed inthe inlet and outlet channels may be locking and/ or controlling or regulating valves 120, 122, 124 and 126.
The two pairs of grinding discs may also operate in series which means that they may be passed by the same stream of material to be treated in the apparatus. For this purpose the channel 46 is connected with the supply channel 48 by means of a connecting pipe branch or coupling 128, the valve 124 and possibly also the valve 122 being dispensed with. After the pulp fed through the channel 42 has been subjected to a grinding treatment in a first step between the discs 22, 26, it is conveyed over to the internal space between the second pair of grinding discs 24, 38 where a grinding treatment in a second step is carried out on the pulp which then will be discharged through the channel 52.
According to the invention, it is possible in both cases to adjust the pressure in the interspace between the two pairs of discs 22, 26, and 24, 38 respectively, or the width of the interspaces 28, 40 within the widest limits by means of the two servo-motors. Assuming that the piston 82 of the pilot valve 80 takes such position that pressure fluid is supplied through the pipe 96 to the chamber 66, the servomotor piston 60 will then produce over the disc 58, the ring member 54, the axial thrust bearing 18 and the shaft 16, a pressure, which will urge the disc 26 towards the stationary disc 22. If, on the other hand, the pressure fluid is fed through the pipe 95 into the chamber 68, pressure thus produced will urge the disc 38 in a direction towards the disc 24. If the piston 82 of the pilot valve 102 takes such a position that the pressure fluid is supplied through the pipes 114, 116, 118 to the chamber 76 and the second servo-motor, the shaft 16 will be displaced to the right and V the shaft 30 to the left viewed in the plane of FIG. 1,
which implies that the two grinding discs 26, 38 are urged in a direction towards the respective stationary discs 22 and 24. The pressure becomes equally great in the two 4 quently the width of the interspace 28, 40, are regulated by adjusting the pistons 82, 82 relatively to the stationary casing of the pilot valves 80, 102, which in the embodiment shown, is effected by means of the adjustment screws 100, 100 respectively. When the predetermined grinding interspace prevails, the pistons 82, 82 of the two pilot valves assume an intermediate position. With regard to the servo-motors 60, 64, this results in that the same pressure prevails in the two chambers 66, 68. If the interspace 28 between the discs 22, 26 is increased due to, for instance, increased supply of material to be ground, the piston 60 of the servo-motor is forced to the left, as will be easily understood, thus moving the arm 99.'The valve piston 82 follows with the servo-motor piston due to action of the spring 101. The chamber 97 is now connected with the chamber 86, which latter is under the pressure created by the pump 91. Instead, the pressure in the chamber 68 of the servo-motor drops as a consequence of a interspaces 28, 40 and is otherwise absorbed within the rotating system and the stationary central base part 20 of the base structure. The axial thrust bearing 18 is totally relieved from thrust. By supplying pressure fluid to the chamber 78 of the servo-motor 70, 72 both rotating grindcommunication being established in the pilot valve between the portion 94 and the chamber 87 which is without pressure. The result will be that the servo-motor piston 60 is subjected to a pressure forcing it to the right, causing the disc 26 to be moved closer to the disc 22 and thus the predetermined Width of the interspace 28 Will be restored.
If, instead, the shaft 16 is displaced to the right, for instance, due to the stream of pulp passing through the interspace 28 being reduced for some reason, the pilot piston 82 is moved in the same direction. The result will be that pressure fluid is forced from the pump 98 through the chambers 86, 94 to the chamber 68 of the servomotor 60, 64. The shaft 16 moves'nowto the left so that a metallic contact between the grinding discs is avoided.
The description applies also to the pilot valve'102. The pilot piston 82 follows'the axial movements of the shaft 130 through intersection of the arm 104, the ring member .106 and the bearing 32. At the displacement of thejshaft A 30 and together therewith the piston 82 to the right, a
pressure fluid is fed from the pump 91 through the pipe 89 the chambers 86 97 and the pipes 114, 116 and 118 ment screws 100, all conceivable values for the grind- 7 ing pressure between the two pairs of grinding discs can be created from only one pair being loaded until both are loaded equally. In the same manner the grinding pres.- sures can be varied in response to all demands set forth regarding the grinding effect. I I
While one more or less specific embodiment of the invention has been shown and described, it is to be understood that this is for purpose of illustration only, and that the invention is not to be limited thereby, but its scope is to be determined by the appended claims.
'What we claim is:
1. A grinding apparatus, primarily intended for lignocellulose containing material and provided with two rotatable grinding discs disposed within a casing and each cooperating with a stationary grinding disc, inlet and discharge channels for the 'material being provided in the casing for each pair of co-operating grinding discs. anda.
base structure for said apparatus; characterized in that each of the rotating discs is supported by a shaft of which shafts one is positioned concentrically around the other shaft and which shafts both are displaceable axially under 7 the action of pressure fluid actuated servo-motors.
2. A grinding apparatus as claimed in claim 1, characterized in that one of the servo-motors has a piston carried by the one shaft and a casing carried by the other shaft in which casing the piston is axially 'displaceable and into which conduits open for supply of pressure fluid to either side of the piston.
3. A grinding apparatus as claimed in claim 2, characterized in that the shaft carrying the piston is at its opposite end, through an axial thrust hearing which is mounted axially movable in the base structure, connected with the piston of the other servo-motor, the casing of which is fixed to the base structure and has conduits opening on either side of the last-mentioned piston for supply of pressure fluid to both sides of the piston.
4. The grinding apparatus as claimed in claim 1, characterized in that the two servo-motors are disposed to be actuated each by a pilot valve of a type known per se and controlling the supply of pressure fluid to both sides of the servo-motor in response to the magnitude of the interspace between the grinding discs.
5. The grinding apparatus as claimed in claim 1, characterized in that the casings are formed for application of the channels in parallel relation to, or by attachment of a socket, in a series with one another.
6. A grinding apparatus, primarily intended for lignocellulose containing material and provided with two rotatable grinding discs disposed within a casing and each cooperating with a stationary grinding disc, inlet and discharge channels for the material being provided in the casing for each pair of cooperating grinding discs, a base structure for said apparatus; characterized in that the said rotatable discs are supported by separate shafts, one of said shafts being positioned concentrically around the other shaft, said shafts being rotatable in one and the same direction, and being displaceable axially under the action of two servo-motors, one of said servo-motors being adapted to actuate both rotatable grinding discs simultaneously and in opposite directions, the other servo-motor being adapted to actuate only one of said grinding discs.
7. A grinding apparatus as claimed in claim 6, char acterized in that one of the servo-motors has a piston carried by one of the shafts and a casing carried by the other shaft in which casing the piston is axially displaceable and into which conduits open for supply of pressure fluid to either side of the piston, said first mentioned shaft being at its opposite end, through an axial thrust bearing which is mounted axilaly movable in the base structure, connected with the piston of the other servo-motor, the casing of which is fixed to the base structure and has conduits opening on either side of the last-mentioned piston for supply of pressure fluid to both sides of the piston.
References Cited UNITED STATES PATENTS 2,743,874 5/1956 Asplund 241286 X 2,864,562 12/1958 Eberhardt et al 241 2,982,482 5/1961 Curtis 241163 X ANDREW R. JUHASZ, Primary Examiner.