GB1559201A - Dispersing or grinding mill - Google Patents

Description

(54) A DISPERSING OR GRINDING MILL (71) We, OLIVER Y BATLLE, S.A., a company organised under the laws of Spain, of Avenida Martin Pujol, 278-284, Badalona (Barcelona), Spain, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a dispersing or grinding mill.

According to the invention, there is provided a dispersing or grinding mill having a generally cylindrical grinding chamber containing a generally horizontal drivable shaft carrying milling members, in which the chamber has a double-walled jacket through which coolant can be circulated, and has a product exit constructed to allow milled product to be discharged but to retain milling elements within the chamber, in which the chamber is mounted solely by one of its ends upon a frame of the mill in such a way that it projects freely from the frame, and in which the inner wall of the chamber is free to move relative to the mounting to allow for expansion or contraction arising from temperature variations during use.

In a preferred version of the invention.

the inner wall is generally cylindrical and of a corrosion-resistant and abrasion-resistant material, and is mounted so that its inner end is free to slide relative to a complementary generally cylindrical surface of the frame.

The shaft may carry interchangeable agitator discs. It may be hollow and coolant liquid may be circulated therethrough.

In an advantageous version of the invention, the shaft may have integral therewith a cylindrical discharge screen which allows the milled product to pass but which does not allow the milling elements to be discharged therewith.

The product exit may be formed by an annular gap defined between rotatable and stationary annular discs.

An advantageous cooling system may be included, in which coolant is fed to the interior of the shaft as well as to a cooling jacket of the grinding chamber. To cool the shaft, the end of the shaft remote from the free end of the chamber has a double-pass rotatable fluid connection and sealing means whereby the coolant fluid can be introduced into and removed from the interior of the shaft.

In a preferred version of the invention an adjustment means for the longitudinal position of the shaft which includes a threaded boss engaging a shaft bearing, the bearing being urged towards the boss by a resilient biassing means.

The invention will better understood from the following description of examples thereof, given with reference to the accompanying drawings in which: Figure 1 is a side elevation, partly in section, of an example of the invention including a screen-type discharge exit for the milled product; Figure 1A is an enlargement of part of Figure 1; Figure 2 is a similar view of a second example of the invention in which the exit for the milled product is formed by an annular gap or slot; and Figure 2A shows part of Figure 2 on a larger scale.

Referring firstly to Figure 1, the illustrated mill includes a generally cylindrical grinding chamber 10, a generally horizontal driven bored shaft 12 carrying milling members 14, a frame 16 which supports the chamber 10 from one end, and means for rotating the shaft 12 generally indicated at 18. As will readily be understood, in use of such a machine, the product to be milled or to be subjected to a dispersing action, such as paint, is fed into the grinding chamber 10 together with milling elements which, conventionally, may be balls or granules or flat chips of hard material. The chamber 10 has an inlet 1 8a for the substance to be milled, and the milling elements, if not already within the chamber, are charged via this inlet. The inlet pipe may have a pres sure gauge 20.The milled product is dis charged via a pipe 22, and the pressure in an exit chamber 24 (Figure 1A) is measured and indicated by a pressure gauge 26. The detailed construction of the mounting of the grinding chamber 10 and the sealing of the shaft 12 will be described later, with par tc-11rr ref-re ce to Figure 1A.

The shaft 12 at its outer end carries two pulleys 30, 32, each driven via endless belts generally indicated at 36. Naturally any suitable motor may be provided to drive the belt 36. The drive is taken to the shaft 12 via one or other of the pulleys 30, 32, allowing one to choose a selected rotation speed. Of course means may be provided for varying the speed of the motor, if de sired, to allow greater variation. The shaft 12 is hollow, and secured to its outer end is a double pass rotary fluid connection, of a known design, indicated at 38. This allows a liquid coolant such as water to be fed into the interior of the hollow shaft 12 via a pipe 40, the coolant liquid then being dis charged via pipe 42.The shaft 12 is mounted in the housing 16 by bearings 44 and 46, the bearing 44 being urged in a leftward direction as seen in the drawing by a resili ent biassing means constituted by a stack of annular disc washers some of which are indicated by 48.

The shaft 12 is hollow over at least the portion of it which extends within the grind ing chamber 10, and it carries grinding members formed by discs 14. Although not shown, the discs 14 can be removed from and replaced on the shaft 12, their relative positions being determined by tubular spacers. Access to the interior of the grind ing chamber 10 to enable this to be done is obtained by removal of an end wall 50.

The wall 50 has a drain plug 52.

The grinding chamber 10 is mounted on the frame 16, and for this nuroose the frame 16 broadens out into a housing 54 which terminates in a flange 56. The housing 54 encloses an inner end wall 60, which partly defines the exit chamber 24 and which car ries an inner end wall 62 of the grinding chamber 10. The shaft 12 passes through the wall 62 and is sealed by an O-ring seal 64. The construction is such that the seal 64 can be replaced by removing an annular retaining ring 66 held by bolts 68.

Part of the shaft wall is constituted by a cylindrical screen 70. This forms the part of the shaft wall adjacent to the inner end wall 62. It provides the exit path for the milled product, and the size of the screen mesh is such that the milling elements can not pass therethrough. According to an ad vantageous feature, the apertures in the screen have an increasing cross-sectional area in the direction of movement of the product being discharged, that is to say in a radially inward direction. An adjacent portion of the shaft wall has radial apertures 72 therein, which permit the milled product to pass radially outwardly into the exit cham- ber 24, and thence to the exit 22.It will be seen that the seal 64 need only be such as to prevent passage of tlle milling elements past it, and an advantageous feature of the present invention is that the shaft 12, where it passes through the wall 60, is sealed by a seal of elegant and efficient design. A pair of annular flap seals 80 are retained by retaining rings 82 and 84, the latter being held in position by bolts one of which is shown at 86. The ring 82 together with the wall 60 defines an annular chamber to which any suitable lubricant liquid, which may also be a coolant liquid, is fed by a pipe 88.

The lubricant may be the solvent liquid corresponding to that in the substance to be milled.

The wall 62 is connected to the housing 60 by any suitable means, such as bolts 90.

These pass through a radially extending flange 92 of the housing 60, the flange 62 having a cut away portion to receive an O-ring seal 94. The inner cylindrical wall 96 of the grinding chamber 10 has a radial flange 98 at its inner end, the flange defining a confronting flat surface which engages the O-ring 94 and faces the flange 92. A clearance between the flanges 92 and 98 allows thermal expansion of the wall 96, due to changes in temperature during operation. This construction can be regarded as a unique "floating" type of mounting of the inner wall 96, and it has been found after extensive tests to be of great advantage in dealing with the problem of expansion and contraction of the wall 96 during operation of the machine. A flange 100 is bolted by bolts 102 to the flange 56, thereby supporting the grinding chamber 10 by one end thereof. Inner and outer walls 104, 105 define a cooling jacket to which a coolant fluid is fed via an inlet pipe 108 and from which it is removed via an outlet pipe 110.

An O-ring seal 112 is provided in a suitable recess in the retaining ring 100.

An advantage arising from the positioning of the cylindrical screen 70 is that its rapid rotation provides a centrifugal force on any particles or material which may tend to be lodged in the apertures, throwing this rnaterial radially outwards and thus effecting a "self-clearing" action. In addition, the rubbing of the milling elements on the outer surface of this screen also has a cleaning action. The mill may readily be disassembled for cleaning or for maintenance.

In addition, the grinding chamber wall, coolant jacket, and retainer ring 100 can all be removed bodily merely by unscrewing the bolts 102. This provides ready access to the shaft 12 and permits one to clean or change the milling members 14. The seal formed by the pair of annular flaps 80 has been found effective to virtually preclude any leakage of milled product from the exit chamber 24.

The grinding and dispersing mill illustrated in Figure 2 is in many respects identical to that illustrated in Figure 1, and accordingly attention will be concentrated on the differences. In the two Figures, like parts bear like reference numerals, and to avoid repetition the identical parts will not be described again. In the Figure 2 version of the mill, the exit path for milled products is defined by an annular gap or slot existing between a fixed annular disc 120 carried by the housing 60, and a rotary annular disc 122 carried by the mixer shaft 12. As can be seen, the disc 122 is secured to a disc 124 which is in turn bolted by bolts 126 into a boss 128 forking part of the shaft 12.

As illustrated in this version of the invention, the wall 96 of the grinding chamber is fixed by means of its flange 98 between the flange 92 of the housing 60 and the retainer ring 100. The clearance to provide the "floating" mounting of the wall 96 is not illustrated, but naturally it will be understood that it can be included if desired.

O-rings 94, 112 are provided as in the Figure 1 embodiment of the invention.

The clearance in an axial direction between the fixed annular disc 120 and the rotary annular disc 122 is adjusted by means of a threaded boss 130, mounted within a threaded ring 132 and engaging the bearing 44. By screwing up the boss 130 the bearing 44 is moved to the right, against the pressure of the discs 48, thereby moving the shaft and the annular ring 122 carried thereby in a direction to the right as seen in the drawing. It will be understood that this increases the width of the annular gap, and similarly by screwing the boss 130 in an opposite direction, the width of the annular gap can be reduced, for example if it is desired to utilise a grinding medium of smaller particle size.

The shaft 12 is sealed where it passes through the housing 60 by a double annular flap seal construction similar to that previously described, It will be seen that the "floating" mounting of the wall 96 of the grinding chamber as illustrated permits it to expand and contract relative to the cooling jacket defined by walls 104, 106. In addtion, the mounting avoids the use of welds which might be fractured due to expansion and contraction and allows easy access to the interior. The wall 96 is preferably made of a high alloy steel especially resistant to abrasion, and this wall can readily be replaced if desired.

The support of the wall is from one end only, which makes access and cleaning easier.

WHAT WE CLAIM IS: 1. A dispersing or grinding mill having a generally cylindrical grinding chamber containing a generally horizontal drivable shaft carrying milling members, in which the chamber has a double-walled jacket through which coolant can be circulated, and has a product exit constructed to allow milled product to be discharged but to retain milling elements within the chamber, in which the chamber is mounted solely by one of its ends upon a frame of the mill in such a way that it projects freely from the frame, and in which the inner wall of the chamber is free to move relative to the mounting to allow for expansion or contraction arising from temperature variations during use.

2. A mill according to Claim 1 in which the inner wall is generally cylindrical and of a corrosion-resistant and abrasion-resistant material, and is mounted so that its inner end is free to slide relative to a complementary generally cylindrical surface of the frame.

3. A mill according to Claim 1 or 2 in which the shaft carries interchangeable agitator discs.

4. A mill according to Claim 1, 2 or 3 in which the shaft is hollow and provided with means whereby a coolant liquid can be circulated therethrough.

5. A mill according to any preceding claim in which the shaft has integral therewith a cylindrical discharge screen which allows the milled product to pass but which does not allow the milling elements to be discharged therewith.

6. A mill according to any one of Claims 1-4 in which the product exit is formed by an annular gap defined between rotatable and stationary annular discs.

7. A mill according to Claim 4 or any claim dependent thereon wherein the end of the shaft remote from the free end of the chamber has a double-pass rotatable fluid connection and sealing means whereby the coolant fluid can be introduced into and removed from the interior of the shaft.

8. A mill according to any preceding claim including an adjustment means for the longitudinal position of the shaft which includes a threaded boss engaging a shaft bearing, the bearing being urged towards the boss by a resilient biassing means.

9. A mill according to Claim 8 in which

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. be removed bodily merely by unscrewing the bolts 102. This provides ready access to the shaft 12 and permits one to clean or change the milling members 14. The seal formed by the pair of annular flaps 80 has been found effective to virtually preclude any leakage of milled product from the exit chamber 24. The grinding and dispersing mill illustrated in Figure 2 is in many respects identical to that illustrated in Figure 1, and accordingly attention will be concentrated on the differences. In the two Figures, like parts bear like reference numerals, and to avoid repetition the identical parts will not be described again. In the Figure 2 version of the mill, the exit path for milled products is defined by an annular gap or slot existing between a fixed annular disc 120 carried by the housing 60, and a rotary annular disc 122 carried by the mixer shaft 12. As can be seen, the disc 122 is secured to a disc 124 which is in turn bolted by bolts 126 into a boss 128 forking part of the shaft 12. As illustrated in this version of the invention, the wall 96 of the grinding chamber is fixed by means of its flange 98 between the flange 92 of the housing 60 and the retainer ring 100. The clearance to provide the "floating" mounting of the wall 96 is not illustrated, but naturally it will be understood that it can be included if desired. O-rings 94, 112 are provided as in the Figure 1 embodiment of the invention. The clearance in an axial direction between the fixed annular disc 120 and the rotary annular disc 122 is adjusted by means of a threaded boss 130, mounted within a threaded ring 132 and engaging the bearing 44. By screwing up the boss 130 the bearing 44 is moved to the right, against the pressure of the discs 48, thereby moving the shaft and the annular ring 122 carried thereby in a direction to the right as seen in the drawing. It will be understood that this increases the width of the annular gap, and similarly by screwing the boss 130 in an opposite direction, the width of the annular gap can be reduced, for example if it is desired to utilise a grinding medium of smaller particle size. The shaft 12 is sealed where it passes through the housing 60 by a double annular flap seal construction similar to that previously described, It will be seen that the "floating" mounting of the wall 96 of the grinding chamber as illustrated permits it to expand and contract relative to the cooling jacket defined by walls 104, 106. In addtion, the mounting avoids the use of welds which might be fractured due to expansion and contraction and allows easy access to the interior. The wall 96 is preferably made of a high alloy steel especially resistant to abrasion, and this wall can readily be replaced if desired. The support of the wall is from one end only, which makes access and cleaning easier. WHAT WE CLAIM IS:

1. A dispersing or grinding mill having a generally cylindrical grinding chamber containing a generally horizontal drivable shaft carrying milling members, in which the chamber has a double-walled jacket through which coolant can be circulated, and has a product exit constructed to allow milled product to be discharged but to retain milling elements within the chamber, in which the chamber is mounted solely by one of its ends upon a frame of the mill in such a way that it projects freely from the frame, and in which the inner wall of the chamber is free to move relative to the mounting to allow for expansion or contraction arising from temperature variations during use.

2. A mill according to Claim 1 in which the inner wall is generally cylindrical and of a corrosion-resistant and abrasion-resistant material, and is mounted so that its inner end is free to slide relative to a complementary generally cylindrical surface of the frame.

3. A mill according to Claim 1 or 2 in which the shaft carries interchangeable agitator discs.

4. A mill according to Claim 1, 2 or 3 in which the shaft is hollow and provided with means whereby a coolant liquid can be circulated therethrough.

5. A mill according to any preceding claim in which the shaft has integral therewith a cylindrical discharge screen which allows the milled product to pass but which does not allow the milling elements to be discharged therewith.

6. A mill according to any one of Claims 1-4 in which the product exit is formed by an annular gap defined between rotatable and stationary annular discs.

7. A mill according to Claim 4 or any claim dependent thereon wherein the end of the shaft remote from the free end of the chamber has a double-pass rotatable fluid connection and sealing means whereby the coolant fluid can be introduced into and removed from the interior of the shaft.

8. A mill according to any preceding claim including an adjustment means for the longitudinal position of the shaft which includes a threaded boss engaging a shaft bearing, the bearing being urged towards the boss by a resilient biassing means.

9. A mill according to Claim 8 in which

the resilient biassing means is formed by a stack of annular spring washers.

10. A mill according to Claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.