Releasable Compression Device for Use With a Crushing Mill or the Like

1. Field of the Invention

This invention relates to a releasable compression device for use on a rolling or crushing mill and more particularly to a device which maintains a constant crushing pressure on crushing rolls of the mill while at the same time allowing one of the rollers to pivot outwardly to allow a passage of a foreign object if such is encountered.

2. Description of the Prior Art

A rolling or crushing mill for processing such hard materials as Carborundum into a finely controlled particle size has been available and known in the art for some time. Particle size of the material processed by such a mill is controlled by the dimension of the nip formed between the crushing rollers.

It has been customary in such a mill to have one roller fixed in location while a second roller is supported in a pivotable frame which allows adjustment of the nip dimension as well as a momentary increase in the nip dimension in case the supply of raw material includes a foreign object which cannot be crushed and could cause damage to the surface of the rollers if the nip were not expandable.

Initial adjustment of the nip between the rollers has been perfected by providing a pivotanble support frame fo the adjustable roller with a lever arm which is carried between two adjustable nuts on a threaded rod. By adjusting the position of the lower nut and then tightening the upper nut accordingly, the relative position of the pivotable roller is maintained to establish the desired dimension of the nip between the fixed and adjustable roller. Any force tending to increase the nip dimension is resisted by the structure of the mill.

Under these conditions, the only safety feature against overstress of the structure because of a change in conditions of the raw material entering the crusher or upon entry of a foreign body into the roller nip, is the strength of the individual components of the mill.

As an added safety feature, some mills use a breakaway or hinge bearing which fails at a certain stress point.

Additionally, hydraulic supporting devices have been incorporated for use with a rolling or crushing mill to position the adjustable roller and thereby control the dimension of the nip. Examples of such a device are disclosed in German Specification No. 1,584,592. Also, German Patent No. 946,676 discloses a controllable hydraulic pressure apparatus for a roller or crushing mill in which a friction bar is incorporated with the roller. German Patent No. 1,083,104 also discloses a hydraulic pressure apparatus for a roller or a crusher mill about which a spring loaded pressure adjusted valve apparatus is incorporated to regulate the operating pressure of the rollers.

A rolling or crushing mill incorporating the invention as disclosed includes a first roller carried in a fixed position on a rigid base or frame. Adjacent to the fixed roller is a second roller mounted in a pivotable support frame which allows a user to adjust the nip dimension formed between the fixed and the second or adjustable roller.

The adjustable roller is carried in an L-shaped frame having a substantially vertical arm which is pivotably attached to the base and a horizontal arm which is carried between two threaded nuts disposed on a substantially vertical rod also pivotably connected to the base.

The distance between the adjacent rollers or nip dimension is varied by loosening the top nut, adjusting the position of the lower nut to rotate the adjustable roller so as to provide the dimension of the nip desired, and then tightening the top nut against the horizontal arm of the L-shaped support frame to fix the position of the adjustable roller.

Because the L-shaped support bracket is pivotably mounted as is the threaded rod, any dimensional change in the nip changes the angle at which the substantially horizontal arm joins the threaded rod. To provide for this change in angle and to assure proper alignment between the threaded rod and a vertical aperture in the horizontal arm through which the vertical rod is disposed, an upper and a lower socket are incorporated between the upper and the lower nut and the arm.

Between the lower socket and the lower nut is a hydraulic cylinder having an annular groove in which a like dimensioned annular piston is dispoed to provide therein a chamber. The cylinder is provided with a fluid port into the groove, so as to allow a flow of hydraulic fluid in and out of the chamber provided therein.

A hydraulic fluid supply system connects with the fluid port of the cylinder and includes a pumping means, a gauge by which the pressure of the fluid in the system can be measured, a shut-off valve between the pumping means and the cylinder inlet and an inert gas filled accumulator located between the shut-off valve and the port cylinder. The accumulator is positioned at an elevation above the port. Using the pumping means, the piston can be subjected to a desired fluid pressure which in turn maintains the joint formed between the upper and lower nut, the socket, and the hydraulic cylinder and piston under a like pressure.

During operation, matter to be crushed is fed between the fixed roller an the adjustable roller. The crushing force in the nip between the rollers is equal to approximately the force maintained by the hydraulic fluid on the piston. Since this force is adjustable, it may be regulated with respect to the type of raw material being crushed or otherwise ground or rolled.

If a foreign object having a dimension greater than the nip becomes positoned between the fixed and adjustable roller and cannot be crushed therebetween, the adjustable roller is forced outwardly to rotate the support frame clockwise so as to cause a downward movement of the arm attached to the threaded rod which in turn causes the piston to displace hydraulic fluid from the chamber within the cylinder. A volume of hydraulic fluid equal to the volume of displaced fluid enters the accumulator where it is stored until the foreign object has passed. The hydraulic fluid then returns to the chamber to move the piston upward and restore the adjustable roller to its original position.

There are several significant advantages to the device as disclosed by this invention. First, the device may be readily adapted to existing rolling and crushing mills without extensive modification.

Second, the force on the adjustable roller to provide the crushing or rolling action in the nip is adjustable and maintained at a practically constant level. The output from the rolling or crushing mill, therefore, has an unusually uniform particle size.

Additionally, the device provides a means by which a foreign object can be passed between the crushing rollers without undue damage to the rollers. One crushing pressure has been exceeded, the dimension of the nip increases so as to allow the passage of the oversized object.

A further advantage is that the crushing pressure may be adjusted with respect to the raw material being processed and once so adjusted, maintained at that pressure by a minimum amount of human supervision.

FIG. 1 is an elevational view of a typical rolling or crushing mill according to this invention; and

FIG. 2 is an elevational view in partial cross-section of a releasable compression device as used with the mill of FIG. 1.

As best seen in FIG. 1, a rolling or crushing mill is shown generally at M and includes a base 1 which carries a fixed upright 2 supporting a rotatable crushing roller 4 on a suitable shaft 3 having an end portion journaled by the upright 2.

A second rotatable crushing roller 5 is carried by a suitable shaft 3', having an end portion journaled by an L-shaped support frame 6 which is pivotably mounted to the base 1 at pivot point 6'.

The support frame 6 has a substantially horizontal arm portion 7 having an outer end with a vertical aperture 50 therethrough at a distance H from the shaft 3. A threaded rod 9 having a bottom end pivotably joined to the base 1 at a pivot point 10 passes through the aperture with sufficient clearance to provide a space 52 therebetween (See FIG. 2).

The end of the arm 7 is positioned between a lower threaded nut 11 and an upper threaded nut 12, threaded on the rod 9. The lower theaded nut 11 has an inner cylindrial body extending upwardly through the aperture 50.

Referring to FIG. 2, between the upper nut 12 and the arm 7 of the support frame 6 is a socket assembly 13 formed with an upper portion 13a and a lower portion 13b. The upper and lower portions 13a and 13b have an upper and lower mating surfaces 54 and 56 having a complementary semi-spherical configuration respectively.

Between the lower nut 11 and the arm 7 of the support frame 6 is a like socket assembly 13' formed with an upper portion 13a' and lower portion 13b' and also having like mating surfaces 58 and 60 having a complementary semi-spherical configuration respectively.

Betwween the lower socket portion 13b' and a top support surface 14 of the nut 11 is a hydraulic assembly 15 comprising a circular piston 16 slidably disposed in suitably proportioned annular groove 16' in a circular shaped cylinder 17 to form a chamber 18 therein.

By means of a suitable fluid port 19 connecting with the chamber 18, a supply of hydraulic fluid 62 can be introduced in the chamber 18 to cause the piston 16 to move upwardly against the lower socket portion 13b' of the lower socket assembly 13'.

A movement of the hydraulic fluid 62 into and out of the chamber 18 can be accomplished by use of a suitable pumping means such as a hand pump 21 having a reservoir 22 which connects with a valving means 24 by means of a pipe 23.

The valving means 24 includes a valve handle 26 by which flow from the pump 21 to the hydraulic assembly 15 can be restricted or shut off, a pressure gauge 25 and a suitable fitting 27 for the piping 20 to connect with the valving means 24. The piping 20 further includes a T-fitting 28 allowing connection with an inert gas filled accumulator 29.

The gauge 25 can have a face plate 30 calibrated in a standard measure of force per area or custom calibrated with respect to the configuration of the apparatus M.

During operation, the dimension W of the nip formed between the rollers 4 and 5 is adjusted as required by first rotating the upper nut 12 upwardly to allow free movement of the arm 7. Next the lower nut 11 is rotated to adjust the dimension W to produce the required nip. Then the upper nut 12 is rotated to produce a firm joint between the arm 7, the sockets 13 and 13', the hydraulic assembly 15, and the lower and the upper nuts 11 and 12.

By means of the pump 21, hydraulic fluid 62 is pumped into the chamber 18 of the cylinder 17 to further increase the pressure of the joint. The amount of pressure in the chamber 18 is indicated by the gauge 25 and upon reaching a desired level, valving means 24 is closed by manipulation of the handle 26, so as to prevent any pressure drop because of the pump 21.

It should be noted that introducing the hydraulic fluid 62 into the chamber 18 of the cylinder 17 has a negligible effect on the dimension "W" since the position of the upper nut 12 sets the minimum limit of "W" while the position of the lower nut 11 sets the maximum limit of "W." To insure that the clearance space 52 is maintained, the positions 13a, 13b, and 13a', and 13b' of sockets 13 and 13' can be adjusted accordingly.

During crushing, the roller 5 is maintained in the position set by the upper nut 12 by the foce exerted by the hydraulic fluid 62 against the piston 16. It should be noted that the force remains nearly constant regardless of the position of the roller 5 between the minimum and maximum limits of "W" as determined by the lower and the upper nuts 11 and 12.

As the roller 5 moves from "W" minimum toward "W" a volume of fluid 62 is displaced from the chamber 18 and a like volume is stored in the accumulator 29 causing only a slight increase in pressure since the volume of gas displaced is only a fraction of the total volume of the gas within the accumulator.

If during crushing or rolling by the rollers 4 and 5 of the mill M a foreign object is encountered which cannot be reduced to a dimension approximting "W" minimum by the force being applied to the roller 5, then the nip dimension can be increased to equal "W" maximum by applying a force exceeding the force on piston 16. It is anticipated that by increasing the nip dimension to equal "W" maximum, the foreign object can be passed without causing undue damage to the rollers 4 and 5.

Thus, in accordance with the method and mechanism above disclosed, a crushing nip is defined between a pair of parallel rollers with the second roller position relative to the first roller by an adjustable fixed stop. Movable roll positioning means for the second roller are held against the fixed stop by a biasing force in excess of that required to hold the rolls in their relative predetermined positions during normal operating pressures. The biasing means, however, yields with excessive pressures in the nip when a foreign object passes therethrough. The biasing means is preferably provided by a pressure chamber containing a hydraulic fluid and backed by a compressible gas with the pressure of the gas being adjustably controllable to hold the roll in its operating position against the fixed stop diuring normal operation, but to compress and permit it to move away to widen the nip when a large foreign object passes therethrough. The arrangement achieves the objectives and advantages above set forth and is so constructed so as to permit opening of the nip and yet permit it to be set to a fixed width and to maintain that width during normal operating conditions. Also, the nip width can be adjusted to a predetermined desired width without changing the function of yieldability of the nip when a foreign object passes therethrough. Also, the amount of biasing force maintaining the fixed width of the nip can be adjusted so that with temporary heavy loads the nip width will remain constant, and the rolls will separate only when a predetermined adjustable pressure in the nip is received as caused by the passage of a foreign object.

It will be apparent to those skilled in the art that many modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.