US2312726A - Hydraulic calender - Google Patents

Description

March 2, 1943. G. c. MUNRO HYDRAULIC CALENDER Filed March 1, 1939 3 Sheets-Sheet 1 INVENTOR fim, 3M a -2M4 'ATTORNEYS March 2, 1943. G. c. MUNRO BYDRAULIC CALENDER Filed March 1, 1959 5 Sheets-Sheet 2 INVENTOR 6- ATTORNEYS March 2, 1943. G. c. MUNRO 2,312,726

HYDRAULIC CALENDER Filed March 1, 1959 s Sheets-Sheet 3 Patented ltlar. 2, 1943 UNITED STATES Search Room PATENT OFFICE HYDRAULIC CALENDER Application March 1, 1939, Serial No. 259,156

3 Claims.

This invention relates to calender devices and means for exerting, adjusting and controlling the pressure thereon. It has a particular field of utility on paper machines and supercalenders and is especially useful in connection with automatic pressure control mechanism as, and for the purposes described in a copending application, Serial No. 259,154, filed concurrently herewith by Donald B. Bradner and George C. Munro, and entitled "Paper making.

The use of fluid pressure in calender devices, though offering many advantages, has heretofore found little favor in the industry because of the numerous difliculties involved, such as the necessity for a separate pump and accumulator for each calender, and frequently for each side of each calender where it is desired to have different pressures on the two sides, the short life of the usual type of pumping equipment at the high pressures and severe service incident to this use, the lack of adequate controls, etc.

The primary object of the present invention is to provide simple, dependable and durable means for applying and for easily, accurately and continuously controlling the pressure, for adjusting the pressure simultaneously on both sides of the calender, or on one side independently of the other. A further object is to provide means for applying and for independently adjusting fluid pressure on the opposite sides of one calender or a plurality of calenders from a single source of fluid pressure whereby only one of the expensive high duty pumping units will be required, and the costs of installation and maintenance will be brought within practical limits. Other objects will be apparent from the further description of the mechanism involved.

For the accomplishment of these objects I employ, according to the present invention, a novel combination of elements, a novel valve mechanism, and a novel arrangement of controls, in connection with the application of hydraulic pressure to one of the rolls in a single calender or in each of the calenders in a group.

The novel valve mechanism which forms a part of the pressure control devices is advantageously a duplex type of valve which provides a separate control for each side of the calender (each end of the rolls) and which can be adjusted to vary the pressure on the two sides simultaneously or independently, as desired. The valve mechanism is so constructed and arranged as to maintain the pressures for which it is set regardless of variations in thickness of the material passing between the rolls and regardless of variations in the hydraulic pressure supply so long as the supply pressure does not fall too low. Each part of the duplex valve mechanism is further preferably arranged to give a reduced and controlled pressure in the fluid supplied to the calender while maintaining the higher pressure in the supply line substantially undiminished.

By the use and proper arrangement of this valve and other elements, as hereinafter more particularly described, I have been able to provide a system for applying any desired pressure to each side of one or more calenders from a single supply of fluid under high pressure under conditions which require extremely small fluid flow and so make it possible to use a durable pump and control without unduly increasing the cost per calender.

The present invention will be better understood by reference to the accompanying drawings, in which one embodiment thereof has been illustrated. In the drawings;

Figure 1 is a front elevation of a supercalender equipped with my hydraulic pressure control devices, in which the fluid circulating system and the pressure control valves are shown diagrammatically and to a distorted scale with parts omitted or displaced for the sake of clarity in the drawing;

Figure 2 is a side elevation of the same calender with a part of one frame broken away;

Figure 3 is a vertical section of the cross head and pressure cylinder, taken on line 3-3 of Figure 2;

Figure 4 is a wiring diagram showing how the pressure control valves may be electrically adjusted;

Figure 5 is an end view of the hydraulic pressure control valve mechanism drawn to a much larger scale, showing the preferred location of the handwheel and pressure adjusting gears, shafts, etc., and showing diagrammatically a power drive mechanism for the adjusting devices;

Figure 6 is a side view of the valve mechanism shown in Fig. 5 with parts broken away to show the construction more clearly;

Figure '7 is a plan view, partly in section taken on line 1-1 of Figure 6, of the same valve mechanism; and

Figure 8 is a fragmentary view showing a modified form of the structures shown in the adjacent portion of Figure 7.

Referring to Figures 1, 2 and 3, a plurality of calender rolls I I, which may be of metal or alternately of metal and other suitable material, are

mounted in frames I3 and I4 which are rigidly held together by tie rods l5. The frames are slotted to form guides wherein the journal boxes l8 are slidably mounted. The lowest of the rolls is journaled in fixed bearings I1 and I8 and the uppermost roll H in slidable bearings i9 and 20. In order to increase the calender pressure beyond the weight of the rolls themselves hydraulic cylinders 2| and 22 are mounted on cross heads 23 and 24 at the top of frames I3 and I4, so that hydraulic pressure on pistons 25 and 26 may be transmitted to the journals of the uppermost roll through rods 21 and 28 and bearing blocks l9 and 20.

Fluid, advantageously oil, under pressure is admitted to cylinders 2| and 22 through conduits 3| and 32 respectively which may be provided with strainers 33 and 34 to prevent passage of solid or abrasive material which might damage the pistons or cylinders. The fluid pressure in cylinders 2| and 22 is indicated on gauges 35 and 36 respectively which are connected to conduits 3| and 32, advantageously through pressure snubbers 35--A and 36--A which may be in the form of small orifices and are adapted to prevent damage to the gauges by sudden changes in pressure.

Any fluid which leaks past the pistons 25 and 26 is drained away through conduits 31 and 38 which are joined together in conduit 39 which is free from fluid pressure. Leakage around rods 21 and 28 is prevented by suitable seals or packing rings 40, which, being immediately below drain openings 31 and 38, are practically free from pressure tending to cause leakage.

Fluid under pressure is supplied from any suitable source which may be an accumulator or other means for furnishing fluid at constant pressure. Particularly in cases where a number of calenders are to be served and the amount of fluid required is subject to considerable variation, as more or fewer calenders are used, I prefer the devices illustrated in Figure 1. As there shown, these consist of a supply tank 50 and a suitable pump which may be of a known variable delivery type, driven by a motor 52 and equipped with a known type of control for adjusting the pump discharge as required to give any pressure for which the control devices may be set by means of hand wheel 53. A known type of pressure control valve 55 may also be used. This valve may be adjusted to deliver fluid at a predetermined pressure into pressure main 56 and return excess fluid through pipe 5'| to reservoir 50. The valve 55 is adjusted to maintain the hydrostatic pressure in main 55 at or somewhat above the maximum pressure required in cylinders 2| and 22 in order to give the maximum pressure which should be applied to the calender, and serves to maintain this predetermined pressure in the pipe line on both sides of valve 55.

Fluid which is returned from the calender pressure control devices, as hereinafter described, passes into a return main 60, which may, when necessary, be provided with a continuously driven pump 6| to prevent back pressure in the main. This pump delivers the returned fluid, advantageously through a filtering device 62, into pipe 63 which returns the used fluid to supply tank 50.

In order to adjust the calender pressure to the requirements of any particular calendering operation, the pressure in main 56 must be reduced and properly controlled before it is introduced into cylinders 2| and 22 through conduits 3| and 32. For this purpose fluid passes from main 56 through conduit 10 and branch conduits H and 12 into pressure control valves 13 and 14 which are adjusted to supply predetermined pressures into conduits 3| and 32, as hereinafter more particularly described, by turning screws 15 and 16 respectively by means of the gears I1 and 18 fixed thereon. The gears 11 and 18 are driven by gears 19 and 80 mounted on shaft 8| which may be turned by a hand wheel 82 which may be provided with a crank handle 82-A as illustrated in Fig. 1, or by a motor as hereinafter described. Gear I8 is turned by gear 80 through an intermediate gear 84 mounted on a stub shaft 83 (see also Figures 5, 6 and 7) supported in a bearing 85 on the body of valve 13. By turning shaft 8| by means of hand wheel 82 (or a motor I50 as hereinafter described) the valves 13 and 14 are simultaneously adjusted to effect a simultaneous adjustment of the pressures in cylinders 2| and 22.

In some cases it may be desirable to have greater pressure on one end of the calender rolls than on the other. If this is desired the structure may be arranged as illustrated in Figure '7 so that by pressing inward on hand wheel 82 gear 19 is displaced along shaft 8|, compressing spring 81, and thrown out of mesh with gear ll. Shaft 8| may then be turned and will through gears 80, 84 and 18 turn screw 16 which serves to adjust valve 14 without changing the adjustment of valve 13, thereby securing an independent adjustment of the pressures on the two sides of the calender, when this is required. If independent adjustment is not desired gear 19 may be fixed instead of slidable on shaft 8|.

Screws I5 and 16 are threaded into adjusting nuts 9| and 92 respectively which are prevented from turning by feet 95 and 96 respectively which slide on the surface of the bodies of valves 14 and 13. Properly calibrated tension springs 93 and 94 are attached to adjusting nuts 9| and 92, as shown in Figures 6 and '7 so that turning screws 15 or 16 in one direction increases and in the other direction decreases the tension on the corresponding spring. Springs 93 and 94 are attached at their opposite ends by clevises 91 and 98 to levers 0| and I02, which are pivoted at I03 and 14 to the respective valve bodies.

The construction of the valves and the manner in which they function to maintain a predetermined hydrostatic pressure will be best understood by reference to Figure '7, in which valve 14 is shown in section, it being understood that valve 13 is of similar construction. The valves are of the piston type in which piston III is accurately fitted into a smooth bore in valve body 14. Piston I is provided with a portion 2 of reduced diameter from which a hole I I3 communicates with a central bore 4. Conduit 32 which transmits hydrostatic pressure to cylinder 22 opens into the bore in valve 14 at a point which is always in communication with the space surrounding the smaller diameter portion 2 of piston I. It is thus apparent that the hydrostatic pressure ln space 5 at the end of piston III will always be the same as that in cylinder 22 which applies pressure to the corresponding side of the calender.

The pressure of the fluid in space 5 on the one end of piston I is thus opposed to the pressure applied to the other end of piston by spring 94 acting through lever I02. As long as these pressures are equal, piston III will rethe piston reaches the limit of its movement.

Movement in this direction brings the reduced diameter 2 opposite, the opening of high pressure conduit 12 from pressure main 55 and permits high pressure fluid to'passthrough the valve into conduit 52 and thence to cylinder 22. When the pressure in cylinder 22 and space 5 reaches the required value, piston III is moved back by this pressure to the position shown in Figure 'l and prevents further increase in pressure in cylinder 22.

If, on the other hand, the fluid pressure exceeds the spring pressure, piston III will be moved to the left in Figure 7 thus bringing reduced diameter II2 opposite the opening leading into exhaust conduit I20, to permit escape of fluid from cylinder 22 and conduit 92 through the valve into exhaust conduit I20 which leads through conduit I22 into return main 60 and back into supply tank 50. When the pressure in cylinder 22 and space II5 hasdecreased to the required amount, spring 94 acting through lever I02 moves piston III back to the position shown in Figure 7 to prevent further decrease in pressure in cylinder 22. g

It may be noted that the movement of pistons 25 and 26 in cylinders 2| and 22 is very small, being equal only to the'small thickness of the paper threadedbetween the rolls, and the slight compression of the non-metallic rolls, when used, under the applied pressure. Consequently only a small amount of fluid need pass through valves 15 and 14 to cause even the maximum required change in pressure, which therefore takes place with corresponding rapidity.

Any fluid whichmay tend to escape aroundpiston III in spite of its accurate fit in the bore of valve body 14 will be caught in annular groove :25 which opens into drain conduit I26 which is free from hydrostatic pressure and which in turn leads through conduit I22 and return main 60 to reservoir 50 or may, if desired, return through a separate drain line to the reservoir in order to avoid any pressure which might exist in exhaust lines I20 and I22. An oil seal or packing rin'g I28 is also provided to prevent escape of oil during movement of piston III.

In the operation of calenders it is frequently desirable to quickly release the pressure without disturbing the adjustment. To accomplish a quick release and reapplication of pressure, a handle I5l is provided. This is adapted to rock on shaft I32 from the on" position illustrated in solid lines to the"ofi position indicated by broken lines in Figure 6. Rigidly attached to handle I3I are cams I33 and I34 which when the handle is rocked to the off" position serve to rock levers I35 and I36 on their pivots I31 and I50 and thereby to press plungers MI and I42 respectively, as shown in Fig. 6, or to press these plungers directly in a manner which will be evident by reference to Fig. 1. As will be apparent from Figure 7, this movement of plunger I42 moves piston II I to the left, bringing reduced diameter II2 opposite exhaust opening I20 thereby releasing the pressure in cylinder 22. This will rock lever I02 and extend spring 94, but will not alter the setting of adjusting nut 92 which controls the pressure which will be maintained in cylinder 22 when handle Ill is returned to the "on" position. Plunger I4I operates in the same manner to open valve 15 and release the pressure in cylinder 2|. Leakage around plungers HI and I42 is prevented by suitable packing glands I45 and I44.

Operation of the valve mechanism by a reversible electric motor I may in some cases be preferable to manual operation by hand wheel 62 and crank 62-A as indicated in Figure l.

The motor I50 is advantageously connected through a suitable speed reduction unit I49 to a gear I49 which is arranged to drivejgear 11, and will then operate to simultaneously adjust the tension on springs 95 and 94. Depression of hand wheel 92 disengages gear 19 from gear 11 and permits the motor to rotate screw 15 to adjust spring 95 while gear 19, shaft II; gears 80, 04, and 16, and screw 16 remain stationary and the adjustment of spring 94 consequently remains unchanged.

Operation of motor I50 to adjust the pressure control valves may be controlled as illustrated in Figure 4. Power is advantageously supplied from a three phase line a; h. 9., while the operation of the motor and its direction of rotation is controlled by switches I5I and I52 which are closed by energizing coils I and I54 respectively. An interlock illustrated diagrammatically at I55 prevents either switch from being closed unless the other is open. The motor is operated in a direction to increase the tension on springs 95 and 94 and consequently the pressure incylinders 2I and 22 by means of push button "I which closes a circuit energizing coil I55 thereby closing switch I5l. The motor is operated in the other direction to decrease the tension on springs 95 and 94 and the pressure in cylinders 2| and 22 by means of push button I54 which closes a circuit energizing coil I54 thereby closing switch I52. The switches I5I and I52 are normally open switches of convention type held open, when coils I55 and I54 are not energized, by any suitable means such as springs I51 and I56 connected to a common anchorage I59, so that they remain closed and cause the motor to operate only so long as the appropriate push button is depressed. Release of the push button immediately stops operation of the motor and further change in the adjustment.

It is apparent that the adjusting mechanism would be damaged by adjustment too far in either direction. When the adjustment is made manually by turning hand wheel 62 there is little danger of damage due to over adjustment but in the case of electrical. adjustment, I prefer to positively prevent over adjustment by the provision of limit switches I55, I66, I61 and Ill. These switches are normally closed, but are opened by contact with the feet 95 and on adjusting nuts 9| and 92 when these reach the high or low limits of their respective adjustments (see also Figure 7). Thus when either spring adjusting nut 9| or 92 reaches the low limit of its adjustment the corresponding low limit switch I65 or I65 is opened, breaking the circuit through cell I54, and opening switch I52, thus preventing further adjustment in this direction. or 92 reaches the upper limit of its adjustment the corresponding high limit switch I61 or I55 is opened breaking the circuit through coil I55, and opening switch I'5I thus preventing further adjustment in this direction.

In case it should for any reason be desired to Similarly when either adjusting nut 9| screwed a duplicate gear I11. 19 on shaft 8| a wide faced gear I19 is substiprevent changes in the pressure adjustment while the pressure is turned of! and gauges 35 and 88 are at zero and will not indicate the changes, a similar switch I10 may be provided to hold circuits through coils I53 and I54 open while handle I II is in the off position. Switch I10 may be connected for operation by handle I3I in any suitable manner.

' In the case of supercalenders, some of the rolls are non-metallic and may be damaged by too great a difierence in pressure from one end of the roll to the other. Thus in these cases, though a diiference in pressure may be necessary to secure proper calendaring action, it may be deslrable to prevent the pressure difference from exceeding predetermined limits. While this may be accomplished by relief valves set to operate at the desired maximum pressure differential and inserted between conduits 3| and 32, I prefer a positive mechanical interlock on the adjusting means, as illustrated in Figure 8.

For this purpose gear 11 on screw 15 may be provided with a threaded hub I18 on which is In place of gear tuted. When gear I19 is pressed inward by hand wheel 82 against spring 81 it is disengaged from gear 11, but remains in mesh with gear I11. Then as gear 11 is rotated by the motor I50, gear I19 remains stationary and holds gear I11 against rotation so that the rotation of gear 11 with its threaded hub I16 causes gear I11 to move along the hub towards or away from gear 11 which limits its motion in one direction, while a collar I18, which may be adjustable if desired, limits its movement in the other direction. To prevent a wedging action of the screw, positive stops I80, I8I and I82 may be provided respectively on gears 11, I11 and collar I18, so that when gear I11 has been moved to the limit in either direction and the engagement of the stops I8I with stops I80 or I82 prevents further turning, of threaded hub I16 in gear I11, the teeth of gears 11 and I11 will be in alignment and stops I8I will drive gear I11 along with gear 11 causing gear I19 to rotate the same as if it were in mesh with gear 11. Since when the stops are in contact, the teeth on gears 11 and I11 are in alignment, spring 81 can readily return gear I19 into mesh with gear 11 when pressure on hand wheel 82 is released. It-may thus be seen that the amount of movement from its normal position allowed to gear I11, before it contacts gears 11 or collar I18, determines the limits of difference between the pressure adjustments of the two valves, and consequently the maximum pressure differential from one side of .the calender to the other.

When the invention is applied to a plurality or system of caienders, each of the several valve mechanisms may be individually adjusted to supply and vary the pressure applied to the corresponding calender and to regulate the relative pressures applied to the two sides of such calender, all without affecting the pressure on any other calender in the connected group. The valve mechanisms quickly and accurately provide pressure changes of small or large magnitude in response to changes in adjustment and in calender pressure, and the volume of fluid flow incident to such pressure changes is very small.

The mechanism as herein described makes possible for the first time a calender system in which fluid pressure can be supplied with little fluid flowto one or a group of calenders from a single high pressure source of supply, and in which the valve pressures on one or both sides of any calender can be varied at the will of the operator, by small or large increments, without affecting the pressure on any other calenders in the group or on the other side of the same calender.

I claim:

1. In combination, a calender comprising a plurality of rolls, a source of fluid under pressure not less than a predetermined minimum, means for pressing one roll in said calender against another roll therein comprising a pressure cylinder at each end of said roll for receiving fluid under pressure and applying mechanical pressure to the corresponding end of said roll and a conduit for each of said cylinders for connecting said cylinder to said source of fluid under pressure, means for maintaining the pressure between said rolls at a predetermined value comprising a valve in each of said conduits, each of said valves having associated therewith means for exerting a mechanical force, and including balancing means for comparing the fluid pressure in the connected cylinder with said mechanical force, said balancing means respondingto conditions of unbalance by movement which admits fluid to said cylinder when the pressure in the cylinder is less than that corresponding to said force and releases fluid from said cylinder when said pressure exceeds that corresponding to said force, means for adjusting the pressure between the rolls in said calender comprising means for simultaneously adjusting by substantially equal amounts the mechanical forces with which the fluid pressures in the cylinders are compared, and means for quickly removing pressure from the calender roll while maintaining the pressure adjustment undisturbed comprising a movable part for simultaneously mechanically moving both of said balancing means in opposition to the forces exerted by said mechani-- cal force exerting means to release fluid from said pressure cylinders.

2. In apparatus of the character described, in combination, a calender comprising a plurality of rolls, a source of fluid under pressure not less than a predetermined minimum, means for applying pressure at each end of a roll in said calender including a hydraulic pressure cylinder associated with each end of said roll, a conduit connecting each of said cylinders with said source of fluid under pressure, means for separately controlling the pressure at each end of said roll comprising a valve housing in each of said conduits having an adjustable spring associated therewith and containing a movable piston balanced between the force exerted thereon .by the fluid pressure in the associated cylinder and a mechanical force exerted thereon by said spring, said piston acting when said forces are in balance to prevent pressure fluid from entering or leaving the associated pressure cylinder and when said forces are out of balance to admit pressure fluid to said cylinder if the force exerted by said spring overbalances that exerted by the fluid and to permit escape of pressure fluid from said cylinder if the force exerted by said spring is overbalanced by that exerted by the fluid, separate means for adjusting the pressure maintained by said control means at'the opposite ends of said roll, each of said adjusting means comprising screw means for adjusting the force exerted by said spring on the corresponding piston, and means for providing either independeat or simultaneous and substantially equal adjustment of the pressure exerted at opposite ends oi the roll comprising a separable driving connection between said screw means whereby operation of one may also operate the other.

3. In apparatus of the character described, in combination, a calender comprising a plurality of rolls, a source of fluid under pressure not less than a predetermined minimum, means for applying pressure at each end of a roll in said caiender including a hydraulic pressure cylinder associated with each end of said roll,- a conduit connecting each of said cylinders with said source of fluid under pressure, means for separately controlling the pressure at each end of said roll comprising a valve housing in each of said conduits having an adjustable spring associated therewith and containing a movable piston balanced between the force exerted thereon by the fluid pressure in the associated cylinder' and a mechanical force exerted thereon by said spring, said piston acting when said forces are in balance to prevent pressure fluid from entering or leaving the associated pressure cylinder and when said forces are out of balance to admit pressure fluid to said cylinder ii' the force exerted by said spring overbalances that exerted by the fluid and to permit escape of pressure fluid from said cylinder if the force exerted by said spring is overbalanced by that exerted by the fluid, separate means for adjusting the pressure maintained by said control means at the opposite ends of said roll, each of said adjusting means comprising screw means for adjusting the force exerted by said spring on the corresponding piston, mean for providing either independent or simultaneous and substantially equal adjustment of the pressures exerted on opposite ends of said roll comprising a separable driving connection between said screw means whereby operation of one may also operate the other, and means for preventing the pressure at one end of said roll from being adjusted to dif- 'Ier by more than a predetermined amount from that at the other end thereof comprising means for re-establishing said driving connection when one of said screw means has been adjusted to cause the force exerted by one of said springs to differ by more than a predetermined amount from that exerted by the other spring.

GEORGE C. MUNRO.

Images