GB1589073A - Hoods for the cylinder drying section of paper making machines and other cylinder drying machines - Google Patents

Description

(54) IMPROVEMENTS IN HOODS FOR THE CYLINDER DRYING SECTION OF PAPER MAKING MACHINES AND OTHER CYLINDER DRYING MACHINES (71) We, GREENBANK-CAST BASALT ENGINEERING CO. LIMITED, of Gate Street, Blackburn, County of Lancaster, a British Company; 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 improvements in hoods for the cylinder drying section of paper making machines and other cylinder drying machines.

A hood made in accordance with the present invention incorporates features occupying considerably less space than existing systems and no more space for the complete hood and heat recovery system than is normally occupied by the hood alone. In addition the initial cost is considerably lower than existing designs and the thermal efficiency is higher because of the utilisation of return passages in the hood as opposed to using external ductwork.

A further feature of the invention is the mounting of a heat exchanger in the hood in a chamber bounded by a diaphragm so that air drawn from the hood passes through the heat exchanger and gives up heat to make-up air flowing through the exchanger before passing through the hollow framework for circulation through the hood.

The object of the present invention is to house supply and exhaust fans, an exhaust heat recovery unit and a steam heater battery within the hood and to utilise the tubes for circulating heated air within the hood as the main supporting framework for the hood.

According to the invention a hood for the cylinder drying section of paper making machines and other cylinder drying machines comprises a plurality of sections or modules, a framework for supporting the hood consisting of longitudinal, transverse and vertical tubes, square or rectangular in cross section, through which heated air is circulated to pocket discharge nozzles in each section between the cylinders, a supply fan, a heat recovery unit and a steam heater battery housed in the heater chamber for each section or module of the hood, an inclined diaphragm wall dividing the hood into two chambers, comprising a heater chamber and a cylinder chamber, a duct for transferring moist air from the cylinder chamber to the heater chamber, and a damper valve to control the passage of the air between the chambers in each module, all the aforesaid features being enclosed within the compass of the hood, and an exhaust fan at intervals for withdrawing air from the modules.

The invention will be described with reference to the accompanying drawings: Figure 1 is a perspective view of a machine with part of the hood broken away and showing the air flow; Figure 2 is a transverse section of the machine; Figure 3 is a plan view of part of the machine; Figure 4 is a side elevation of Figure 3.

A hood A for enclosing the drying cylinders 1 of paper making machines or cylinder drying machines is supported on a hollow tubular framework, square in cross section, consisting of transverse tubes 2 and longitudinal tubes 2a and vertical tubes 2b through which heated air is circulated to pick up moisture from the material B being dried on the cylinders 1.

The machine is divided up into a plurality of sections or modules and air is drawn into the hood A through ducts 3 (Figure 3) by a supply fan 4 for each section or module, the length of the hood being multiples of the length of each 8 metre section or module.

The air on entering the ducts 3 is divided, one half of the air passing across a heat recovery unit 7 of one section or module and the remaining half is distributed to the heat recovery unit 7 of the adjacent section or module. The air after passing across the heat recovery unit 7 and after circulating under the hood A and framework 2, 2a, 2b, is exhausted by an exhaust fan 6. The air before reaching the exhaust fan 6 passes from the supply duct 3 as already described across the heat recovery unit 7 and is further heated by passing through a steam heater battery 10 through the fan 4 to transverse tubes 2 which meet longitudinal tubes 2a when the air divides and on meeting vertical tubes 2b passes downwards to pocket venti lators or vapour absorption nozzles 9 arranged adjacent to the cylinders 1 (Figure 4), the air being then dispersed into the hood A.

The interior of the hood A is divided into two compartments by a diaphragm wall 14 which divides the hood into the two chambers comprising a heater chamber and a cylinder chamber, a longitudinal duct 11 conducting heated air from the heat recovery unit 7.

The moist air is then drawn from the hood by the exhaust fan 6 through the longitudinal duct 11 provided with a filter 12 and a restrictor 13, through the heat recovery unit 7 and over the heater battery 10, a proportion of the air being recirculated by the supply fan 4 and the remainder being exhausted to atmosphere through an exhaust duct 15. A portion of the air for recirculation is directed into the unit 7 by a damper or flap valve 13a.

The tubes through which the air is circulated are supported on legs 16 which carry the panels forming the hood A on a framework 17 extending downwards to below the lower rows of cylinders 1 with a bottom extending horizontally below the cylinders and which assists the tubes 2, 2a, 2b in supporting the hood. A motor may be provided for lifting doors (not shown) at the front of the machine.

The dew point of the air circulating through the hood is kept at a level to prevent any condensation or precipitation and the passage of the air through the framework maintains the framework at a temperature high enough to prevent condensation.

The hood A is divided into self-contained modules or sections each section having its own steam or other heaters 10 and the supply fan 4 or fans for passing air through the framework, to maintain constant humidity. The bye pass flap or damper valves 1 3a may be utilised in each section to allow exhaust air to be recirculated and mixed with the make-up air, these flap or damper valves 1 3a being either manually or mechanically, electrically or pneumatically operated or automatically in conjunction with humidity measuring devices.

The hood incorporates the following features: 1. The employment of the supporting structure of the hood as an internal ductwork system produced from rectangular hollow tubes.

2. Incorporation of a corrugated honeycomb structure or similar air-to-air heat exchangers 7 within the structure of the hood itself and the directing of the exhaust air around the recovery unit 7 to recover heat from the exhaust.

3. The utilisation of by pass flap or damper valves 13 controlled manually or automatically to maintain constant humidity conditions in each section or modules of the hood.

4. The complete exclusion of external ductwork for supply and return air to the hood air systems by incorporating supply fans 4, steam heaters 10 and return air ducts 11 within the hood structures.

In addition to the foregoing it is also possible to incorporate air-to-water heat exchangers in certain sections of the hood if required and additional water spray units in the final exhaust air stream after the heat exchangers to utilise the last vestiges of residue heat for water heating purposes.

The hood may be of modular form and constructed in such a manner that, if required, it can be initially supplied as a simple open canopy which can be converted to a totally enclosed unit at a later date and all of the aforesaid features added in stages if necessary.

WHAT WE CLAIM IS: 1. A hood for the cylinder drying section of paper making machines and other cylinder drying machines comprising a plurality of sections or modules, a framework for supporting the hood consisting of longitudinal, transverse and vertical tubes, square or rectangular in cross section, through which heated air is circulated to pocket discharge nozzles in each section between the cylinders, a supply fan, a heat recovery unit and a steam heater battery housed in the heater chamber for each section or module of the hood, an inclined diaphragm wall dividing the hood into two chambers comprising a heater chamber and a cylinder chamber, a duct for transferring moist air from the cylinder chamber to the heater chamber, and a damper valve to control the passage of the air between the chambers in each module all the aforesaid features being enclosed within the compass of the hood and an exhaust fan at intervals for withdrawing air from the module.

2. A hood for cylinder drying machines as in Claim 1 in which the nozzles direct the heated air from the vertical tubes into the hood between the peripheries of adjacent cylinders.

3. A hood for cylinder drying machines as in Claims 1 or 2 and control means for the damper valve to maintain constant humidity conditions in the hood.

4. A hood for cylinder drying machines of paper making machines and other cylinder drying machines substantially as described with reference to the accompanying drawings.

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. lators or vapour absorption nozzles 9 arranged adjacent to the cylinders 1 (Figure 4), the air being then dispersed into the hood A. The interior of the hood A is divided into two compartments by a diaphragm wall 14 which divides the hood into the two chambers comprising a heater chamber and a cylinder chamber, a longitudinal duct 11 conducting heated air from the heat recovery unit 7. The moist air is then drawn from the hood by the exhaust fan 6 through the longitudinal duct 11 provided with a filter 12 and a restrictor 13, through the heat recovery unit 7 and over the heater battery 10, a proportion of the air being recirculated by the supply fan 4 and the remainder being exhausted to atmosphere through an exhaust duct 15. A portion of the air for recirculation is directed into the unit 7 by a damper or flap valve 13a. The tubes through which the air is circulated are supported on legs 16 which carry the panels forming the hood A on a framework 17 extending downwards to below the lower rows of cylinders 1 with a bottom extending horizontally below the cylinders and which assists the tubes 2, 2a, 2b in supporting the hood. A motor may be provided for lifting doors (not shown) at the front of the machine. The dew point of the air circulating through the hood is kept at a level to prevent any condensation or precipitation and the passage of the air through the framework maintains the framework at a temperature high enough to prevent condensation. The hood A is divided into self-contained modules or sections each section having its own steam or other heaters 10 and the supply fan 4 or fans for passing air through the framework, to maintain constant humidity. The bye pass flap or damper valves 1 3a may be utilised in each section to allow exhaust air to be recirculated and mixed with the make-up air, these flap or damper valves 1 3a being either manually or mechanically, electrically or pneumatically operated or automatically in conjunction with humidity measuring devices. The hood incorporates the following features:

1. The employment of the supporting structure of the hood as an internal ductwork system produced from rectangular hollow tubes.

2. Incorporation of a corrugated honeycomb structure or similar air-to-air heat exchangers 7 within the structure of the hood itself and the directing of the exhaust air around the recovery unit 7 to recover heat from the exhaust.

3. The utilisation of by pass flap or damper valves 13 controlled manually or automatically to maintain constant humidity conditions in each section or modules of the hood.

4. A hood for cylinder drying machines of paper making machines and other cylinder drying machines substantially as described with reference to the accompanying drawings.

4. The complete exclusion of external ductwork for supply and return air to the hood air systems by incorporating supply fans 4, steam heaters 10 and return air ducts 11 within the hood structures.

In addition to the foregoing it is also possible to incorporate air-to-water heat exchangers in certain sections of the hood if required and additional water spray units in the final exhaust air stream after the heat exchangers to utilise the last vestiges of residue heat for water heating purposes.

The hood may be of modular form and constructed in such a manner that, if required, it can be initially supplied as a simple open canopy which can be converted to a totally enclosed unit at a later date and all of the aforesaid features added in stages if necessary.

WHAT WE CLAIM IS:

1. A hood for the cylinder drying section of paper making machines and other cylinder drying machines comprising a plurality of sections or modules, a framework for supporting the hood consisting of longitudinal, transverse and vertical tubes, square or rectangular in cross section, through which heated air is circulated to pocket discharge nozzles in each section between the cylinders, a supply fan, a heat recovery unit and a steam heater battery housed in the heater chamber for each section or module of the hood, an inclined diaphragm wall dividing the hood into two chambers comprising a heater chamber and a cylinder chamber, a duct for transferring moist air from the cylinder chamber to the heater chamber, and a damper valve to control the passage of the air between the chambers in each module all the aforesaid features being enclosed within the compass of the hood and an exhaust fan at intervals for withdrawing air from the module.

2. A hood for cylinder drying machines as in Claim 1 in which the nozzles direct the heated air from the vertical tubes into the hood between the peripheries of adjacent cylinders.

3. A hood for cylinder drying machines as in Claims 1 or 2 and control means for the damper valve to maintain constant humidity conditions in the hood.