US2050749A - Pulp grinder temperature control system - Google Patents

Description

Aug. 11, 1936. c. D. DE MERS 2,050,749

I PULP GRINDER TEMPERATURE CONTROL SYSTEM Filed. July 25, 1933 'INVENTOR U605 ton D. DeMers Patented Aug. 11, 1936 PULP GRINDER TEMPERATURE CONTROL SYSTEM Clayton D. De Mers, Rochester, N. Y., assignor to.

Taylor Instrument Companies, Rochester,

N. Y., a corporation of New York Application July 25, 1933, Serial No. 682,095

6 Claims. (ores-15) This invention relates to an improvement in the method of, and means for controlling the operation of pulp grinders.

The applicants prior Patent #1,806,238, a novel and practical arrangement was disclosed for controlling the temperature of the grinding stone or other abrasive roll in a wood pulp grinder, to maintain the stone at a predetermined temperature so that scorching or burning of the pulp fiber was prevented. Furthermore, severe strains on the stone due to wide variations in temperature were prevented so that there was less chance of surface-shelling" of the stone or outright fracture of the same. However in the operation of the arrangement of the patent, it has been noted that the consistency of the resulting wood pulp or stock varies due to the fact that as the surface of the stone becomes duller during use, a greater amount of water must be applied to'it to hold its temperature at a predetermined value, with the result that the stock becomes thinner as the stone becomes more dull.

It has been found in producing a uniform quality of ground wood pulp, that the proper operating temperature for a wood pulp grind ing stone when it is sharp, is different from the proper operating temperature of the same when it is dull, and that the operating temperature of the grinding stone should gradually be permitted under proper regulation to become higher as the grinding surface becomes duller. Furthermore, this progressive change in controlled temperature of the grinding stone should be effected without increasing the average amount of cooling water to the stone, thereby maintaining a grinding temperature best suited to the cutting surface of the stone during the period between the times when it is sharpened or burred, as well as maintaining a uniform consistency of the resultant ground wood pulp.

In accordance with one feature of the present invention, it is proposed as the grinding stone becomes duller, automatically to adjust the control point of a temperature regulator for the samefso that the normal demand for cooling water will be controlled to an average uniform rate of flow with resultant wood pulp of a uniform consistency, as distinguished from prior arrangements where the temperature of the grinding stone is maintained at a fixed value, in which arrangements the flow of cooling water to the stone increased as the stone became more dull. Another feature of the invention relates to an arrangement in which a time cycledevice trol.

progressively changes the amount of the response of the regulating valve in the water cooling line to 'a given change in temperature. A further feature of the invention relates to an arrangement responsive to the average pressure applied to a regulating valve in the water supply line, to vary the set point of a controlling device for determining the operation of the regulating water valve of the stone cooling system in response to a change in temperature.

These and other features of the invention will appear from the detailed description and claims when taken with the drawing in which Fig. 1 is an elevation partly in section of a wood pulp grinding installation embodying the present'in- 5 vention; and Fig. 2 illustrates a portion of a modified form of regulator which may be substituted for the corresponding equipment within the broken line rectangleof Fig. 1, in order to provide a different method of controlling the I temperature.

engaging the threaded lugs 8a formed on a part of the frame. The side of each magazine adjacent the stone is open, while through the opposite side of the magazine there extends a pressure foot l which is operated by the rod 5a of a piston 5 forming a part of a hydraulic motor 6 whereby the logs at the bottom of each magazine are pressed against the stone. The specific type of magazine feed as herein shown ismerely given by way of example, since other kinds of magazines are known with which the present invention will function equally well.

In order to control the surface temperature of the stone I, a cooling medium such as water is sprayed on the surface of the stone through the pipe 9 independently of temperature con- Besides the cooling water supplied through the pipe 9, additional cooling water is supplied through the pipe 9a and 9e for application to the stone under the control of the temperature-regulated diaphragm valve 91). The-water applied to the stone, as well as the wood pulp ground thereby, collects'in a stone pit III which discharges into trough II. It will be understood that while it is preferred to spray the cooling water on the surface of the stone,

the water may be introduced into the mass of ground wood pulp about the stone.

As in the arrangement disclosed in the mentioned patent, a thermo-responsive bulb |2 of a temperature regulator R is mounted close to the surface of the stone and close to but above the plane where the surface of the stone emerges from the water in the pit. This bulb prefrably extends approximately from one end of the stone to the other and is supported on the adjustable plate 1 near the edge thereof so that as the surface of the stone wears down and the plate I is adjusted toward the stone, the bulb I2 is moved simultaneously therewith to preserve-the desired spacing between the bulb and the stone.

In the present invention the bulb l2 communicates through a capillary tube |3 with a capsular diaphragm 4 which is mounted on a bracket i5 of the instrument R. The bulb l2, capillary tube I3 and the capsular diaphragm M are preferably filled with a thermo-responsive medium such as a vapor, although a liquid such asmercury may be used. A stud I6 carried on the free surface of the diaphragm |4 engages the periphery of a cam I! which is mounted for rotation on a vertically moving floating 'pivotJ The construction of the floating pivot is not illustrated since it is wellknown in the art. The cam is driven clockwise from the starting point A of its cycle by suitable reduction gearing IB of a clock l9, containing a clock. motor 20. stood that this cam is so geared tothe clock that it makes one revolution in the interval that the stone I normally remains in service before it is reburred. A stem 2| engaging the upper edge of cam .ll is connected to the valve disc of a relay valve 22 which controls the flow of compressed air or other pressure fiuid from the conduit 23 to the conduit 24 leading to the diaphragm top of the regulating valve 91). This regulating valve which controls =the flow of cooling water through pipe 90 to the stone, is of the type that tends to open under .the action .of its spring when air pressure on its actuating diaphragm is reduced.

In the operation of this form of the invention, as the surface of the grinding stone I becomes heated, the material thrown off thereby likewise becomes heated, with the result that the vapor in the bulb l2 expands and causes the capsular diaphragm -|4 to expand. This expansion of the diaphragm lifts stud l6 which raises the floating cam I1. elevates the valve stem 2| of the relay valve 22 tending to close it, thereby reducing the compressed air supplied through the conduit 24 to the diaphragm top of the regulating valve 9b.

At the beginning of the cycle, when the surface of the stone I is sharp the valve stem 2| movement of the diaphragm H in response to a given change in the temperature of the bulb |2 at the beginning of the cycle when the stone issharp, the relay valve will close farther than It will be underislifted ittends to close the relay valve 35,

Cam I1, in turn,

the fact that the distance between the upper end of the stud I6 and the lower end of stem 2| changes as the cam l1 rotates. In other words, the set point of the regulator R is progressively changed in accordance with the passage of time, which passage of time is proportional to the reduced cutting action of the stone due to its becoming more dull.

In Fig. 2 there-is illustrated a portion of a modified regulator which may be substituted for the portion of the regulator within the broken line rectangle of Fig. 1, to provide a modified arrangement-of the invention. In this arrangement, instead of using a time-actuated cam which changes progressively the set. point of the regulator R to compensate for increasing dullness of the stone, the average decrease in air pressure supplied 'to'the regulating valve 912, due to the increasing temperature resulting from the increasing dullness of the stone, is used to go change the set point of the regulator. It is believed that this form of the invention' will best be understood by describing its method of operation in controlling the surface temperature of the stone I. In this arrangement, when 25 the temperature of the bulb l2 increases due to the increasing temperature of the liquid thrown off from the rotating stone, the vapor in the bulb |2 expands through the capillary tube |3 causing the capsular diaphragm to 30 expand. The lower surface of this diaphragm is supported at the end of an arm 3|! which is thereby reducing the air pressure in the conduit 24 and consequently in the diaphragm chamber. of the regulating valve 9b. In response to the reduction in air pressure in this diaphragm chamber, the regulating valve tends to open thereby applying more cooling medium to the stone. It will be noted that the conduit 240 communicates through the branched conduit 24!) restriction 3G and reservoir 31, with the'capsular diaphragm 38. This capsular diaphragm, which" has its lower surface secured to the bracket 3! forming a part of the frame 32,. is provided'on its upper surface with a centrally located stud 40 to engage the underside of the arm 3| for the purpose of controlling the vertical move--' ment of the capsular diaphgram M. In this form of the invention, as the air pressure is reduced in the conduit 24a due to the gradually increasing temperature resulting from the increaso0 ing dullness of the surface of the stone, this reduced pressure gradually permits the air stored in the'reservoir 31 to leak away through the restriction 36, conduits 24b and 24a and through the opening about the valve stem 34 of the 65 relay valve 35.- As the pressurein the reservoir 31 is reduced, the capsular diaphragm 38 tends to collapse and its-stud 40 permits the arm 3. to lower the capsular diaphragm l4. This lowering of the capsular diaphgram requires a greater change in temperature at the bulb I! to effect a corresponding opening of the relay valve 35 as compared with the former position of this valve; In other words, as the surface of the stone becomes more dull with the consequent 15 gradual increase in the surface temperature thereof, aside from the variations in temperature due to the varying degree of hardness of the wood, the capsular chamber I4 will tend to reduce gradually the air pressure in the conduit 24, thereby opening the regulating valve 9b in order to supply more cooling medium to the stone. This reduced air pressure inthe-conduits 24a. and 241) causes the capsular chamber 38 to lower the capsular diaphragm IS in effect resulting in a change in the setpoint of the regulator.

From the foregoing it will be seen that methods of controlling the temperature of a wood pulp grinder are provided in which the consistency of the resulting pulp is maintained substantially uniform, irrespective of the dullness of the stone. In one case the changing cutting action of the stone is compensated for by changing the set-point of the regulating instrument in accordance with the passage of time, and in the second casethe compensation is effected by changing the set point of the instrument in response to the diminishing air pressure supplied to the regulating valve in the water line to the grinder which diminishing air pressure reflects the cutting condition or dullness of the stone.

I claim:

l. The method of producing wood pulp of uniform quality and of a consistency varying within a negligible range by grinding the wood on a water-cooled stone, which comprises holding pieces of wood against the grinding surface of said stone, applying cooling water to the stone in amounts proportional to the increase in surface temperature of the stone and inversely proportional to the decreasing sharpness of the stone.

2. The method of producing wood pulp of uniform quality and of a consistency varying within the stone, and means actuated jointly byisaid mechanism for controlling the application of cooling liquid to the stone.

4. In a pulp grinder, in combination with a grinder stone, means for forcing the material to be ground into contact with the stone, means for applying a cooling liquid to the stone including a receptacle below the stone for maintaining the cooling liquid in flowing contact with the lower portion of the stone, a temperature-sensitive bulb disposed above the level of the liquid in the receptacle and in the path of the liquid thrown off from the rotating stone, a pressure-responsive member in communication with said bulb, a cam rotated in accordance with time on an axis determined by said member, said cam having a gradually decreasing diameter from a high point thereon, a regulating valve controlling the application of the cooling medium to said stone, and a relay valve controlling the application of pressure fluid to the motor of said regulating valve, said relay valve being controlled from the periphery of said cam.

x 5. In a pulp grinder, in combination with a grinder stone, means for forcing the material to be ground into contact with the stone, means for applying a cooling liquid to the stone ,including a receptacle below the stone for maintaining the cooling liquid in flowing contact with the lower portion of the stone, 9. temperature-sensitive bulb disposed above the level of the liquid in the receptacle in the path of the liquid thrown off from the rotating stone, a pressure-responsive member in communication with said bulb, a pressure-fluid operated regulating valve controlling the application of cooling medium to said stone, a relay valve controlling the application of pressure fluid to the motor of said regulating valve, said relay valve being actuated by a negligible range by grinding the wood on a said member, and means responsive to the presstone, which comprises holding pieces of wood against the surface of said stone, applying a cooling medium to the stone in amounts proportional to the increase in temperature thereof and inversely proportional to the lapse of operating time since the stone was sharpened.

3. In a pulp grinder, a grinding stone, means for forcing the material to be ground into contact with the stone, means for applying a cooling liquid to the stone, mechanism responsive to the surface temperature of said stone, mechanism responsive to the decreasing sharpness of sure fluid applied to said regulating valve to modify the relation between said member and said relay valve.

6. In a pulp grinder, a grinder stone, means for forcing the material to be ground into contact with the stone, means for apply a cooling liquid to the stone, time schedule mechanism and thermosensitive mechanism responsive to the surface temperature of the stone, controlled jointly by said mechanisms for regulating the application of cooling liquid to the stone.

CLAYTON D. De MERS.

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