A Device for Introducing a High-Temperature Fluid into a Rotating Body.

Technical Field.

The invention relates to a device for introducing a high- temperature fluid into a rotating body.

Specifically though not exclusively the invention is useful in the paper industry for introducing a heat vector fluid internally of a rotating body constituted by a drying cylinder or calender of a continuous paper l ne. The heat vector fluid can be for example water vapour, heat transferring oil, or the like.

Background Art. Reference is made in particular to a device comprising a pipe, destined solidly to connect with the rotating body and through which the heat vector fluid passes, and a support, situated externally of the pipe, to which the tube is rotatably coupled on special bearings. Generally there are two connections to the support, one delivery connection and a discharge connection for the heat vector fluid. Further, sealing organs are provided, operating between the rotating pipe and the fixed support. The joint is connected to the rotary body, for example a drying cylinder or calender for paper, by coaxially fixing the pipe to the body so that the joint exhibits an outlet end which opens into an inlet mouth of the rotary body. During functioning, the rotary body draws the pipe in its rotary motion, while a heat vector fluid, previously heated to a relatively high operating temperature, is fed to the delivery connection and, passing through the pipe, is introduced into the rotary body, transferring heat

thereto. Generally the fluid, after having performed its set task, is sent to the discharge connection through a discharge channel which is also solid in rotation with the rotary body; the discharge channel is usually located coaxially and internally of the pipe.

In order to improve the performance and speed of industrial processes where the introduction of a high- temperature fluid in a rotary body occurs, especially in the paper industry, the temperature of the fluid is relatively high.

Experience, however, teaches that it is not at present wise to rise above a certain limit working fluid temperature, since this would lead to intolerable thermal stress on the bearings mounted on the rotating pipe in which the hot fluid flows. What happens, taking into account the operative conditions such as body rotation speed, fluid pressure and so on, is that the increase in the vector fluid working pressure temperature acts negatively on the working conditions of the joint bearings and thus lead to a diminution of their functioning duration and, obviously, the need to replace them more frequent1y.

At present, therefore, a relatively low vector fluid working temperature is fixed, which detracts from the performance and velocity of the industrial process, all in order to reduce to a minimum the number of the times the rotating body has to be stopped to substitute the joint bearings. For example, in the specific case of the paper industry, the maintenance halt for a drying cylinder or a calender leads to the blocking of an extremely complex and expensive plant, with a considerable ensuing economic cost .

The main aim of the present invention is to obviate the above drawbacks in the prior art by providing a device, constructional y simple and economical, which enables a

heat vector fluid to be used at a relatively high temperature, while at the same time guaranteeing long bearing functioning times. An advantage of the present invention is that a high temperature gradient between the bearings mounted on the pipe and the internal wall of the pipe itself, in direct contact with the fluid, can be obtained,

A further advantage is that the differentiated dilations caused during functioning due to the above-mentioned temperature gradient are compensated.

A still further advantage is that of collecting the heat transferring fluid which inevitably escapes through the seals between the rotating pipe and the relative fixed support, avoiding thus the loss of the fluid into the environment. Further, thanks to the present invention it is possible to prevent loss of the bearing lubricating oil into the environment.

Disclosure of the Invention.

These aims and advantages and others besides are all attained by the device of the invention, as it is characterised in the claims that follow.

Further character stics and advantages of the present invention will better emerge from the detailed description that follows, of an embodiment of the invention, illustrated in the form of a non-limiting example in the accompanying drawings, in which: figure 1 shows a lateral view of a first embodiment of the device of the invention with some parts sectioned according to line I-I of figure 2; figure 2 is a lateral view from the left of figure 1, with some parts sectioned according to line 11—II of figure 1; figure 3 shows a section of a detail of a second embodiment of the invention. With reference to the figures, 1 denotes in its entirety a

device for introducing a high-temperature fluid into a rotating body.

In the example the rotating body, not illustrated, is constituted by one of the many drying cylinders of a plant for the manufacture of paper. This cylinder rotates on command about a horizontal axis x of rotation. A continuous belt of paper to be dried winds partially about the external surface of the cylinder. The external active surface of the cylinder is heated by means of the above- mentioned fluid. In the specific case the heat vector fluid can be heat transferring oil or water vapour. A heater, not illustrated, heats the heat transferring fluid up to a working temperature which can reach up to above 300 degrees Celsius. The heated fluid, through a fluid feed delivery circuit, is sent to the device 1 and thereafter introduced in to the user rotating body, whic in the example is a drying cylinder.

Then the fluid, after having heated the active surface of the rotating cylinder on which a paper belt to be dried is wound, newly passes through the device 1 and returns to the heater through a discharge branch of the feed circuit. The direction of the heat transferring fluid flow is denoted by arrows 14. 3 and 4 denote a delivery connection and a device discharge connection provided for connection with the delivery and discharge branches of the heat transferring fluid feed circuit.

2 denotes a heat transferring fluid feed pipe which is provided for solid and coaxial connection with the drying cylinder. A flange 5 is mounted for this purpose on an end of the pipe 2.

The pipe 2 is rotatably coupled with rotation axis x to a support 6 to which said delivery connection 3 and the discharge connection 4 are fixed. Two bearings 7 equipped with seal rings 27 are mounted between the support 6 and

the pi pe 2 .

A heat transferring fluid return pipe (not illustrated) is arranged internally and coaxially of the pipe 2, which return pipe is in communication at one end thereof with the rotating cylinder and at another end thereof with the discharge connection 4. The return pipe serves for the passage of the heat transferring fluid after it has transferred heat to the rotating cylinder. Seals are provided between the feed pipe 2 and the support 6. In the example, the seals comprise a frontal seal ring 8 made solid to the pipe 2 and located coaxially externally of said pipe 2. A seal collar 9, coaxial to the pipe 2, is mounted on the support 6 and can be limitedly displaced axially thereto. The collar 9 is kept pressed against the frontal seal ring 8 by one or more springs 10, so that a seal is made between one fixed face of the collar 9 and a rotating counterface of the ring 8. Further seal means, not illustrated in the drawings, are provided, also operating on the rotating pipe, which seal means are conformed and arranged such as to isolate the heat transferring fluid delivery flow from the return flow thereof .

The device 1 exhibits a fin 26 made solid to the support 6 and destined to interact with a special external bracket in order to avoid rotation of the support 6.

The description to this point has made reference to characteristics which are common to rotating joints of known type. In the present invention, between the pipe 2 and the bearings 7 an annular cooling conduit 11 is provided, which is solid in rotation with the pipe 2. The cooling conduit 11 exhibits an inlet 12 and an outlet 13 of a cooling fluid. Also provided are means for feeding the cooling fluid, preferably compressed air (not illustrated) which injects a flow of refrigerating air in a channel 15

made in the breadth of the support 6. The direction of the air flow is indicated by arrows 16. The channel 15 opens into an annular chamber 17 afforded in a portion of frontal extemity in the support 6 and a shaped annular disc 18 fixed to the support 6. The chamber 17 exhibits an annular aperture facing the inelt 12 of the cooling conduit 11. A labyrinth seal 19 operates between the disc 18 and the external surface of the pipe 2. An annular chamber 30 is afforded internally of the support 6, at the outlet 13 of the cooling conduit 11: said annular chamber 30 has at one end thereof an outlet 31 of the cooling air connected to the source of compressed air in such a way as to create a closed ci rcuit . As is evidenced in figure 1, the path of the cooling air passes close to the sealing rings 27 and the seal zone between the frontal seal ring 8 and the seal collar 9. The conformation and arrangement of the cooling fluid path is such that the flow thereof aspirates and entrains the inevitable lubrication oil and heat transferring fluid leaks exiting from the seals. In this way said fluids pollute get lost to the environment.

A support structure 20 operates between the two facing internal walls of the cooling conduit 11, which support structure 20 is preferably made of steel and, in the embodiment shown in figures 1 and 2, comprises a plurality of tubular elements 21 paralllel to the cooling conduit 11 and arranged internally of the conduit, side by side and in contact one with another. Each tubular elements 21, which extends in axial direction from the inlet 12 to the outlet 13, is further in contact with the facing internal walls describing the cooling conduit 11. Contact between a single tubular element 21 and said cooling conduit 11 walls occurs along two slim longitudinal zones of very limited width.

Also provided are means for contrasting the tubular elements 21 circumferentially with respect to the cooling conduit 11. Said means for contrasting preferably comprise a stop 22 fixed to both facing internal walls of the cooling conduit 11 by means of a pin 28. The stop 22 is constituted by a parel lelepi ped plate interpos tioned between two tubular elements 21, in contact there-with, and extended lengthwise about the same as the tubular elements 21. The cooling conduit 11 is realized by predisposing a sleeve 29 about the portion of pipe 2 acting as a pivot, on which sleeve 29 bearings 7 are mounted, said bearings 7 having an internal diameter which is greater than the external diameter of the pipe 2, thus giving rise, between the pipe 2 and the sleeve 29, to a hollow space, open at ends thereof, which affords the cooling conduit 11. Then, internally of said hollow space, the tubular elements 21 are inserted by force to form a crown surrounding the pipe 2. The dimensions of the pipe 2, the sleeve 29 and the tubular elements 21 are chosen in such a way as to realize an interference fit. The bearings 7 are mounted on the sleeve 29.

In the illustrated embodiments, the cooling conduit 11 and the relative path of the cooling fluid involve both bearings 7. Obviously it would be possible to provide an axially shorter annular conduit for each bearing 7. In the embodiment of figure 3 the support structure 20 comprises a corrugated element 23, preferably made of steel, having a surface composed of alternated projections 24 and recesses 25, where the projections 24 are in contact with one of the two facing internal walls describing the cooling conduit 11 , and the recesses 25 are in contact with the remaining wall. In this case, too, the sleeve 29 is arranged about the pipe 2, creating thus a hollow space which is open at opposite ends and internally

of which the corrugated element 23 is arranged with an interference fit. In this embodiment, too, a fixed means of contrasting (not illustrated) is arranged in the cooling conduit 11, which prevents the corrugated element 23 from moving circumferentially inside the cooling conduit 11.

During use, the cooling conduit 11 is continuously fed with a cooling fluid (in the example compressed air) which follows the path indicated by arrows 16, while both the pipe 2 and the sleeve 29 external to the pipe 2 and functioning as coupling pivot of rotation, as well as the support structure 20 comprised between the pipe 2 and the sleeve ?d , are drawn in rotation by the rotating body. At the same time the heat transferring fluid, at a relatively high temperature, is fed to the pipe 2 and thence introduced into the rotating body.

As it passes through the cooling conduit 11, the cooling air sprays the internal and external walls of the cooling conduit 11 as well as the internal and external surfaces of the support structure 20. The support structure 20, apart from having structural functions, also represents a barrier to the heat transmitted by radiation from the internal wall and the external wall of the cooling conduit 11. For this aim at least a portion of the external surface of the support structure 20 is preferably mirror- smooth. The heat transmitted by conduction between the walls of the cooling conduit 11 is relatively low, since the thermal bridges are limited, in substance, to the thin zones of contact between the support structure 20 and the walls of the cooling conduit 11 and the stop 22.

It has been observed that, thanks to the special cooling system of the present invention, in the breadth comprised between the internal wall of the pipe 2 in direct contact with the hot heat transferring fluid and the internal surface of the bearings 7, a very high thermic gradient is

established. The temperature of the bearings 7 during use is relatively low, which increases the duration of functionabi 1 ty. This thermic gradient does not represent a structural problem as the deformab 1 ity and elasticity of the material of the support structure 20 and its special conformation and arrangement compensate for the differentiated thermic dilations originating from the temperature gradient. Thanks to the invention it is possible the user rotating body can work at high rotation speeds and high heat transferring working temperatures, but at the same time the number of maintenance stops of the support system can be 1 i i ted.