FACILITY FOR HEATING A PRODUCT IN STRIP
United States Patent 3668786
A heating facility for strip product including a heating bed over which the strip travels and variable pressure devices which urge the strip toward the bed.
US Patent References:
Machine for making laminated panels
Osgood - November 1938 - 2137505
Method and apparatus for cast coating paper
Gottwald et al. - November 1963 - 3110612
Mechanism for controlling the heating of corrugated board by injection of an air film between the board and heating surface
Nitchie - March 1965 - 3175300
ELECTRICAL CONTROL DEVICE FOR A HYDRAULIC CIRCUIT
Piret - January 1970 - 3489063
Machine for making laminated panels
Osgood - November 1938 - 2137505
Method and apparatus for cast coating paper
Gottwald et al. - November 1963 - 3110612
Mechanism for controlling the heating of corrugated board by injection of an air film between the board and heating surface
Nitchie - March 1965 - 3175300
ELECTRICAL CONTROL DEVICE FOR A HYDRAULIC CIRCUIT
Piret - January 1970 - 3489063
Application Number:
04/823123
Publication Date:
06/13/1972
Filing Date:
05/08/1969
View Patent Images:
Export Citation:
Assignee:
Societe D'Etudes et de vante de Materiels Pour la Fabrication et le (Rhone, FR)
Primary Class:
Other Classes:
100/170, 100/153, 100/311, 38/8, 34/144, 100/309
International Classes:
B31F1/28; B31F1/20; F26B13/10
Field of Search:
34/43,56,143,144,145 162/359,375 38/8,11,18 144/282
Primary Examiner:
Dority Jr., Carroll B.
Claims:
I claim
1. A facility for heating a product in strip form comprising a heating surface over which the strip is movable and means for maintaining the strip in contact therewith, said means including a continuous belt loaded by evenly spaced idler rollers, each roller exerting on said belt its own weight and at least one pressure-gas-energized ram connected to each of said rollers to increase the load on said belt, said rams being pressure-fluid-energized, at least one valve controlling the fluid pressure to said rams, a servomotor controlling said valve and regulating means controlling said servomotor receiving information relating to the speed of strip movement and information relating to the position of said servomotor.
2. A facility as set forth in claim 1, said regulating means including a voltage comparator receiving a first voltage, a tachometer dynamo driven at a speed proportional to strip speed providing said first voltage, and receiving a second voltage, and a potentiometer associated with the position of said servomotor providing said second voltage.
3. A facility as set forth in claim 2, said valve including a manual control facility independent of the servomotor control, the two controls being usable simultaneously.
4. A facility as set forth in claim 1, including a solenoid actuated valve for said rams associated with a single roller, and a switch for each of said solenoid actuated valves.
5. A facility as set forth in claim 4, said switches being controlled by a cam, a servomotor rotating said cam and regulating means for said servomotor receiving information relating to the speed of strip movement.
6. A facility as set forth in claim 4, said rams being double-acting and said solenoid valves being reversible.
1. A facility for heating a product in strip form comprising a heating surface over which the strip is movable and means for maintaining the strip in contact therewith, said means including a continuous belt loaded by evenly spaced idler rollers, each roller exerting on said belt its own weight and at least one pressure-gas-energized ram connected to each of said rollers to increase the load on said belt, said rams being pressure-fluid-energized, at least one valve controlling the fluid pressure to said rams, a servomotor controlling said valve and regulating means controlling said servomotor receiving information relating to the speed of strip movement and information relating to the position of said servomotor.
2. A facility as set forth in claim 1, said regulating means including a voltage comparator receiving a first voltage, a tachometer dynamo driven at a speed proportional to strip speed providing said first voltage, and receiving a second voltage, and a potentiometer associated with the position of said servomotor providing said second voltage.
3. A facility as set forth in claim 2, said valve including a manual control facility independent of the servomotor control, the two controls being usable simultaneously.
4. A facility as set forth in claim 1, including a solenoid actuated valve for said rams associated with a single roller, and a switch for each of said solenoid actuated valves.
5. A facility as set forth in claim 4, said switches being controlled by a cam, a servomotor rotating said cam and regulating means for said servomotor receiving information relating to the speed of strip movement.
6. A facility as set forth in claim 4, said rams being double-acting and said solenoid valves being reversible.
Description:
This invention relates to an improved facility for heating a product in strip form which is moved over a heating surface, the facility being of use more particularly in the heating section of the "double-face" portion of a corrugated cardboard manufacturing machine.
The stuck-together assembly of smooth and curved sheets forming the corrugated cardboard is heated in this part of the machine to dry the sheets and produce permanent adhesion between them. Conventionally, the cardboard strip goes to this end over a number of iron or steel plates which are usually heated by an internal steam flow. An endless belt whose bottom run bears on the cardboard strip keeps the same in engagement with the heating plates. The pressure applied by the belt to the cardboard is amplified by idler rollers disposed freely in slide-ways or on pivoted levers so as to bear on the belt, the latter therefore providing an at least rough distribution of their weight over the cardboard strip.
The length of an installation of this kind is so devised that the dwell of the cardboard on the heating plates at the maximum speed of the machine is long enough for there to be a satisfactory heat exchange between the plates and the cardboard. However, when the speed has to be reduced for any reason, the dwell time of the cardboard increases and it overheats. Because of the heat inertia of the heating-plate system, the temperature of the plates cannot be varied rapidly in correlation with the variations in the speed of strip movement.
Also, the normal practice is to use a single machine to corrugate boards having a very wide range of quality and compressive strength. Pressure-roller weight is calculated for working the heaviest and strongest boards and is excessive for lightweight boards; to process the latter, some of the rollers, for instance, one out of every two, must be cut out to reduce the overall pressure, but this elimination does not reduce the local pressure of a roller on the board in the same proportion.
To obviate these disadvantages, it is an object of this invention to enable the roller pressure on the board to be varied immediately and steplessly. Another object of the invention is to enable the heat exchange between the board and the heating plates to be varied without plate temperature having to be changed but by varying in dependence upon speed the contact heat resistance transmission, by varying the contact pressure between the board and the plates.
According to the invention, each roller experiences its own weight plus the action of at least one pressure-gas-energized ram.
The invention will now be described in greater detail with reference to an exemplary embodiment shown in the drawings wherein:
FIG. 1 is a partial simplified view of a double-face heating section in a conventional corrugating machine;
FIG. 2 shows a similar section but in accordance with the invention;
FIG. 3 shows simultaneous manual and servomotor control of a ram supply expander; and
FIG. 4 is a block diagram showing how such a servomotor can be controlled;
FIG. 5 is a view similar to that of FIG. 2 showing solenoid actuated valves for energizing the rams;
FIG. 6 is a view similar to that of FIG. 2 showing cam actuated switches for the solenoid valves; and
FIG. 7 is a view similar to that of FIG. 2 showing double acting rams and two way solenoid valves for energizing the rams.
Referring now to FIG. 1, a conventional heating section of a corrugating machine comprises a bearing frame in the form of longitudinal members 1 and ground support legs 2. Disposed transversely on members 1 are heating plates 3 to which piping (not shown) for the supply of a hot fluid, such as steam, is connected. A corrugated cardboard strip 4 is moved in the direction indicated by an arrow 5 by elements disposed downstream of the zone shown and rests on plates 3. The endless belt 6 is shown in FIG. 1 and passes over driving drum 50 and drum 51 as is well known in the art; the width of belt 6 is equal to or greater than the width of the strip 4. Idler rollers 7, whose length is equal to or slightly greater than the width of the belt 6, are mounted at each end to rotate freely, in the ends of rods 8 connected by way of a pivot 9 to an auxiliary longitudinal member 10.
Referring to FIG. 2, which shows a similar portion of a corrugating machine but devised in accordance with the invention, presser rollers 11 are disposed at the end of links 12 pivoted by way of pivots 13 on a top auxiliary longitudinal member 14. Each of pneumatic rams 15 has its casing articulated to member 14 by way of a pivot 16 and its rod connected by way of a pivot 17 to the respective links 12 and is energized through a flexible pipe 18 connected to a general air line 19.
Referring now to FIG. 3, a pneumatic control valve 20 to which compressed air is supplied through a line 21 energizes the ram distribution line 19 at a controlled pressure. Valve 20 has an adjusting rod which is connected to a combined servomotor and reducer 22 via gearwheel 23, an annulus 24 and satellites 25-27 of a planetary gear system, and gearwheels 28, 29. Satellite carrier arm 30 is rigidly secured to a manual adjustment spindle 31 having a calibrated dial 32. Spindle 31 has known locking means (not shown) for immobilizing the arm 30 when the same is not being used for manual adjustment. A potentiometer 33 is disposed on the same shaft as the gearwheel 28.
Referring to FIG. 4, the servomotor 22 is connected to a power supply 40 via a reversing contactor 41. The strip 4 is driven by a motor 42 having mounted on the end of its shaft a tachometer dynamo 43 which delivers a voltage proportional to the speed of strip movement. The two voltages produced by the dynamo 43 and potentiometer 33 are input to an electronic voltage comparator 44. Depending upon the sign of the difference between the two voltages, comparator 44 outputs a signal which operates contactor 41 one way or the other, either via amplifier 45 and relay 47 or via amplifier 46 and relay 48.
In a machine thus devised, when the speed of the strip 4 increases the voltage produced by the dynamo 43 also increases and the regulator 44 starts the servomotor 22 to the hand corresponding to an increase in the pneumatic pressure in the rams 15, until the potentiometer 33 connected to the servomotor 22 has restored the balance between the voltages. Increasing the pressure in the rams 15 increases the pressure with which the cardboard 4 bears on the plates 3, and the correspondingly increased heat transfer therefrom to the cardboard 4 compensates for the reduction of the dwell time of the cardboard 4 on the plates 3.
The range of pressure variation in the rams 15 can be altered by means of the manual control to cope with different board qualities and strengths. Action on the spindle 31 causes, via the satellites 26, an alteration of the initial compressed air pressure delivered by the valve 20 without altering the position of the potentiometer 33.
The invention is not of course limited by the exemplary embodiment hereinbefore described. For instance, placing the rams the opposite way round as compared with the description falls under this invention, the force which the rams produce then opposing the weight of the rollers. An increase in machine speed would then be associated with a gradual reduction of the air pressure in the rams, such pressure vanishing when the machine was running at maximum speed.
Also, a solenoid valve 52 (FIG. 5) can be provided in the supply line to each group of two rams associated with a roller so that the rams act only on some of the rollers. The number of rollers affected is selected by manual operation of switches 53 controlling the energizing solenoid valves. If required, the number of rollers with and without ram loading can be varied automatically by the switches of the solenoid valves being operated by an appropriately shaped cam 54 (FIGS. 3 and 6) driven by a servomotor of the same kind as used for the valve, such servomotor being connected to a similar strip-speed-dependent regulating facility.
Another possibility would be to use double-acting rams 55 (FIG. 7) combined with reversing solenoid valves 56 actuated by two-way switches 57, in which event the rollers could have a weight greater than or less than their self-weight.
The stuck-together assembly of smooth and curved sheets forming the corrugated cardboard is heated in this part of the machine to dry the sheets and produce permanent adhesion between them. Conventionally, the cardboard strip goes to this end over a number of iron or steel plates which are usually heated by an internal steam flow. An endless belt whose bottom run bears on the cardboard strip keeps the same in engagement with the heating plates. The pressure applied by the belt to the cardboard is amplified by idler rollers disposed freely in slide-ways or on pivoted levers so as to bear on the belt, the latter therefore providing an at least rough distribution of their weight over the cardboard strip.
The length of an installation of this kind is so devised that the dwell of the cardboard on the heating plates at the maximum speed of the machine is long enough for there to be a satisfactory heat exchange between the plates and the cardboard. However, when the speed has to be reduced for any reason, the dwell time of the cardboard increases and it overheats. Because of the heat inertia of the heating-plate system, the temperature of the plates cannot be varied rapidly in correlation with the variations in the speed of strip movement.
Also, the normal practice is to use a single machine to corrugate boards having a very wide range of quality and compressive strength. Pressure-roller weight is calculated for working the heaviest and strongest boards and is excessive for lightweight boards; to process the latter, some of the rollers, for instance, one out of every two, must be cut out to reduce the overall pressure, but this elimination does not reduce the local pressure of a roller on the board in the same proportion.
To obviate these disadvantages, it is an object of this invention to enable the roller pressure on the board to be varied immediately and steplessly. Another object of the invention is to enable the heat exchange between the board and the heating plates to be varied without plate temperature having to be changed but by varying in dependence upon speed the contact heat resistance transmission, by varying the contact pressure between the board and the plates.
According to the invention, each roller experiences its own weight plus the action of at least one pressure-gas-energized ram.
The invention will now be described in greater detail with reference to an exemplary embodiment shown in the drawings wherein:
FIG. 1 is a partial simplified view of a double-face heating section in a conventional corrugating machine;
FIG. 2 shows a similar section but in accordance with the invention;
FIG. 3 shows simultaneous manual and servomotor control of a ram supply expander; and
FIG. 4 is a block diagram showing how such a servomotor can be controlled;
FIG. 5 is a view similar to that of FIG. 2 showing solenoid actuated valves for energizing the rams;
FIG. 6 is a view similar to that of FIG. 2 showing cam actuated switches for the solenoid valves; and
FIG. 7 is a view similar to that of FIG. 2 showing double acting rams and two way solenoid valves for energizing the rams.
Referring now to FIG. 1, a conventional heating section of a corrugating machine comprises a bearing frame in the form of longitudinal members 1 and ground support legs 2. Disposed transversely on members 1 are heating plates 3 to which piping (not shown) for the supply of a hot fluid, such as steam, is connected. A corrugated cardboard strip 4 is moved in the direction indicated by an arrow 5 by elements disposed downstream of the zone shown and rests on plates 3. The endless belt 6 is shown in FIG. 1 and passes over driving drum 50 and drum 51 as is well known in the art; the width of belt 6 is equal to or greater than the width of the strip 4. Idler rollers 7, whose length is equal to or slightly greater than the width of the belt 6, are mounted at each end to rotate freely, in the ends of rods 8 connected by way of a pivot 9 to an auxiliary longitudinal member 10.
Referring to FIG. 2, which shows a similar portion of a corrugating machine but devised in accordance with the invention, presser rollers 11 are disposed at the end of links 12 pivoted by way of pivots 13 on a top auxiliary longitudinal member 14. Each of pneumatic rams 15 has its casing articulated to member 14 by way of a pivot 16 and its rod connected by way of a pivot 17 to the respective links 12 and is energized through a flexible pipe 18 connected to a general air line 19.
Referring now to FIG. 3, a pneumatic control valve 20 to which compressed air is supplied through a line 21 energizes the ram distribution line 19 at a controlled pressure. Valve 20 has an adjusting rod which is connected to a combined servomotor and reducer 22 via gearwheel 23, an annulus 24 and satellites 25-27 of a planetary gear system, and gearwheels 28, 29. Satellite carrier arm 30 is rigidly secured to a manual adjustment spindle 31 having a calibrated dial 32. Spindle 31 has known locking means (not shown) for immobilizing the arm 30 when the same is not being used for manual adjustment. A potentiometer 33 is disposed on the same shaft as the gearwheel 28.
Referring to FIG. 4, the servomotor 22 is connected to a power supply 40 via a reversing contactor 41. The strip 4 is driven by a motor 42 having mounted on the end of its shaft a tachometer dynamo 43 which delivers a voltage proportional to the speed of strip movement. The two voltages produced by the dynamo 43 and potentiometer 33 are input to an electronic voltage comparator 44. Depending upon the sign of the difference between the two voltages, comparator 44 outputs a signal which operates contactor 41 one way or the other, either via amplifier 45 and relay 47 or via amplifier 46 and relay 48.
In a machine thus devised, when the speed of the strip 4 increases the voltage produced by the dynamo 43 also increases and the regulator 44 starts the servomotor 22 to the hand corresponding to an increase in the pneumatic pressure in the rams 15, until the potentiometer 33 connected to the servomotor 22 has restored the balance between the voltages. Increasing the pressure in the rams 15 increases the pressure with which the cardboard 4 bears on the plates 3, and the correspondingly increased heat transfer therefrom to the cardboard 4 compensates for the reduction of the dwell time of the cardboard 4 on the plates 3.
The range of pressure variation in the rams 15 can be altered by means of the manual control to cope with different board qualities and strengths. Action on the spindle 31 causes, via the satellites 26, an alteration of the initial compressed air pressure delivered by the valve 20 without altering the position of the potentiometer 33.
The invention is not of course limited by the exemplary embodiment hereinbefore described. For instance, placing the rams the opposite way round as compared with the description falls under this invention, the force which the rams produce then opposing the weight of the rollers. An increase in machine speed would then be associated with a gradual reduction of the air pressure in the rams, such pressure vanishing when the machine was running at maximum speed.
Also, a solenoid valve 52 (FIG. 5) can be provided in the supply line to each group of two rams associated with a roller so that the rams act only on some of the rollers. The number of rollers affected is selected by manual operation of switches 53 controlling the energizing solenoid valves. If required, the number of rollers with and without ram loading can be varied automatically by the switches of the solenoid valves being operated by an appropriately shaped cam 54 (FIGS. 3 and 6) driven by a servomotor of the same kind as used for the valve, such servomotor being connected to a similar strip-speed-dependent regulating facility.
Another possibility would be to use double-acting rams 55 (FIG. 7) combined with reversing solenoid valves 56 actuated by two-way switches 57, in which event the rollers could have a weight greater than or less than their self-weight.