WO1997044627A2

WO1997044627A2 - Process for the continuous firing of ceramic pipes and furnace for implementing it

Info

Publication number: WO1997044627A2
Application number: PCT/EP1997/002261
Authority: WO
Inventors: Christian Roffler
Original assignee: Christian Roffler
Priority date: 1996-05-03
Filing date: 1997-05-02
Publication date: 1997-11-27
Also published as: DE19617717A1; WO1997044627A3

Abstract

In the process for the continuous firing of ceramic pipes (30), the pipes (30) lie on two support bars (34, 35) running in the longitudinal direction (28) of the furnace (26). Said support bars (34, 35) form a plurality of descending sections (36, 37) down which the pipes (30) can roll. To each descending section (36, 37) is allocated a stop (40) which is provided at the end of a descending section and is fitted across the length (28) of the furnace (26). On rolling down the descending section (36, 37), the pipes (30) acquire sufficient kinetic energy, for them to be redirected across the longitudinal direction (28) on striking the stop (40).

Description

Name: Process for the continuous firing of ceramic pipes and furnace to carry out this process.

The invention relates to a method for the continuous firing of ceramic tubes and to a furnace for carrying out this method.

As is known, the ceramic material is only produced by firing. Burning in the furnace turns green pipes into a ceramic pipe, in particular stoneware pipes for the sewage system. During firing Dür ^¬ no shape deviations fen occur, this would result in the finished tubes to geometric errors, for example, deflection, irregular shape or the like. Pipes in a kiln are therefore moved so that shape errors cannot occur. A method is known for firing ceramic tubes in a furnace, in which the tubes initially rest in the fork of Y-shaped carriers, two such carriers being associated with each tube. The carriers of each of the two sides are each driven by a chain. Inside the furnace, at least in its high temperature zone, the pipes are rolled over a raised plateau or a slight slope. They are moved forward by one leg of the Y-shaped carrier and remain in contact with this leg.

This method and the corresponding furnace have proven themselves in principle, but the relatively high mechanical outlay is disadvantageous. The synchronism of the two supports of each tube is difficult to achieve, rather it happens that the two supports of a tube are not at the same height, so that the tube is transported obliquely forward. This leads to problems. In addition, this known method is only suitable for pipes without an external glaze and without an integrated sleeve.

This is where the invention begins. It has set itself the task of improving the process of the type mentioned in the introduction and to further develop the furnace accordingly so that the transverse alignment of the pipes inside the furnace is always guaranteed.

This object is achieved by the method according to patent claim 1 and by the furnace according to patent claim 8.

In contrast to the method of the type mentioned at the outset, the method according to the invention is also suitable for firing tubes with an integrated sleeve and tubes which are glazed on the inside and outside. The support rails ^¬ form a variety of gradients, preferably they are continuously arranged one after another, thus continuously merge into one another. Continuous is understood to mean the word continuous in the mathematical sense. The gradients may be stationary and are preferably fixed before ^¬ so that the left and right guide of a tube always have the same position. When the tubes when rolling down a Gefäl ^¬ lestrecke deviate from the transverse direction, respectively, this deviation is again balanced and the end of the downhill slope by stops the correct transverse position restored. For this purpose, the pipes have at the end of a slope have a sufficient kinetic energy, so that they automatically when striking against the respective stop as the ^¬ can align to the longitudinal direction transversely. This kinetic energy should, however, only be so large that the alignment is reliably achieved so that the bumps remain low when striking the stop. Furthermore, the movement of the pipes along the downward gradients should take as much time as possible. Accordingly, the gradients are so inclined that although a secure rolls of the tubes is preferably achieved without any additional mechani¬ cal drives, but the shallowest angle at which a derarti ^¬ is achieved ges rolling, is selected.

In the preferred embodiment, the mounting rails have a continuous gradient from the beginning to the end of the furnace, for example a gradient of 1 to 4 degrees. The tubes roll continuously on these rails, which are inclined in this way, and are aligned correctly again by stops, which are preferably parts of transport ^devices .

The transport system according to the invention is essentially stationary. Since ^¬ th through, errors in synchronization of drive chains no longer occurring defects ^¬. It can be any length built ovens. According to the invention, the tubes are constantly in motion, but it is also possible not to roll them continuously, but to alternate between rolling and resting phases. The hours of rest are doing so suffi ^¬ sized time accordingly short that no permanent deformation of the pipes occur in them, in particular no bending or changing the Quer¬-section.

The tubes roll on two elongate, substantially parallel support rails ^¬. Each roll the descents down to an on ^¬ shock and then pass through the transport device supports essentially automatically into the next downhill section. However, it is also possible to lift them from one downhill section into the following downhill section by means of a conveyor device. In this way, both glazed pipes and pipes with an integrated sleeve can be produced.

The tubes are preferably transported through the furnace continuously, but possibly also in cycles. Green tubes are introduced into the entrance of the furnace and finished tubes are removed. In the preferred continuous workflow, the stops and thus the transport devices work synchronized.

The pipes should advantageously have a different rotational orientation at the beginning of a downhill section than at the end of the downhill section. You turn ^¬ when rolling down the slope by an angle alpha, z. B. alpha = 70 ° or 180 °. The length of the downhill sections is now matched to the outside diameter of the pipes so that the pipes are rotated through the downhill sections and by rolling down a certain amount alpha for the subsequent possible rest position and this size is chosen so that the pipes are always again take different rotational positions. As a result, the pipes cannot become out of round or bend in the hot-plastic state. Is carried out so the support on the rails carry ^¬ that the pipes are supported in their gravimetric fourth points. The mounting rails are narrow, for example several centimeters to a maximum of twenty centimeters, e.g. B. 10 cm, wide. Between the two mounting rails there is 50% of the total weight of the pipe, on the left and right of each guide there is 25 percent by weight. As a result, the mounting rails have the least possible influence on the Deformation of the pipes. They have a flat surface.

When the tubes are dipped prior to entry into the furnace in a glaze bath, only those areas remain unglazed on the outer ^¬ coat, with which the tubes rest on the support rails during firing. Advantageously, the tubes prior to immersion in the glaze bath are externally gripped by forceps, the annular cover those areas and thus protect against access of the glaze bath with which the raw ^¬ re rest later on the support rails.

Further advantages and features of the invention result from the remaining claims and the following description of not limiting to understanding embodiments are explained in detail, the voltage with reference to the drawing ^¬. In this drawing:

FIG. 1: a basic side view of a device for firing ceramic tubes, FIG. 2: an interior view of a section of the furnace according to FIG. 1 in a side view, FIG. 3: a top view of the arrangement according to FIG. 2, FIG. 4: a side view similar to FIG. 2 in another embodiment and FIG. 5: a representation similar to FIG. 2 in a further embodiment.

According to FIG 1 are for burning suitable pipes, so-called green tubes 20 immersed first in a glaze bath 22, and then a furnace 26, which is designed as an elongated kiln and is also referred to as horizontal burn oven conveyed into the A ^¬ transition region 24. The furnace has a longitudinal direction 28. It accommodates tubes 30, they lie within ^¬ half of the furnace 26 is substantially horizontal and transverse to the longitudinal direction 28. The individual tubes 30 are spaced apart tung in longitudinal Rich ^¬ 28 cm, for example 10 to m is 1, the tubes 30 are in ^¬ nerhalb of the furnace 26 in a single layer. The burned pipes 30 leave the furnace 26 at an exit region 32.

Inside the furnace 26, the tubes 30 rest on support rails 34, 35. There are two support rails 34, 35 are provided which extend substantially parallel to each other ^¬. They support the pipes, whereby for the support tongue as small as possible is used, so far the support rails 34, 35 are for example a few cm wide, if possible they are even narrower, z. B. only 1 cm or less wide.

The support rails 34, 35 form a plurality of slopes 36, 37 lying one behind the other. In the exemplary embodiments shown, they all lie on a straight line. They can also be curved. The individual gradients 36, 37 preferably merge into one another. In a not shown, also possible embodiment, the slopes are arranged one behind the other in the manner of a sawtooth. With 36 the slopes outside a high-temperature zone 38 of the furnace 26 are designated, with 37 the slopes within this high-temperature zone 38. In the area of the high-temperature zone 38 there are temperatures of a maximum of, for example, 1,100 to 1,280 ° C. In this area, the tubes 30 become hot plastic, and improper handling can result in permanent deformation. According to the invention, the pipes are rotated again and again by rolling down gradients 36, 37. On the basis of stops 40, which are each located at the end of a downhill section 36, 37, it is achieved that the pipes 30 are always found transversely to the longitudinal direction 28 when they have got into an inclined position due to the rolling. In the case of sawtooth-shaped gradients, the short, essentially vertical tooth flanks form stops.

The details of the furnace can be seen more clearly from the first exemplary embodiment according to FIGS. 2 to 3. Thereafter, the furnace 26 has an upper wall 42, side walls 44 and a lower wall 46. The support rails 34, 35 run parallel and straight in a side view. The slopes 36, 37 merge seamlessly.

The rolling of the tubes 30 serves to give the tubes a different orientation again and again. When the downward gradients 36, 37 roll down, the pipes each have a different rotational orientation. In other words, the tubes 30 roll on their outer jacket and rotate at an angle that is not equal to 360 ° and is dimensioned as possible that in the case of several successive descending gradients and thus rotations, there are always different or opposite directions Rotational alignments can be achieved. In this respect, angles of rotation of 70 ° or 180 °, for example, have proven to be particularly favorable. One problem is that you want to use an oven for several, differing ^¬ che pipes, for example for pipes having nominal diameters 150, 200 and 250 mm. In them, the outer periphery is different, the ^¬ accordance with the angular change of the rotational alignment at specified waste roll distance different. The lengths of the downhill sections 36, 37 and the transport processes are coordinated and selected in such a way that the occurring pipe diameters are rotated as optimally as possible.

A so-called transport device 48 is provided for the transport of a pipe 30 from a downhill section 36, that is to say from a stop 40 at the beginning of a subsequent downhill section 36. In the case of a sawtooth-shaped gradient, this is a lifting device that lifts the pipes onto the beginning of an inclined surface.

The exemplary embodiment according to FIGS. 2 and 3 is based on support rails 34, 35 which extend over the entire length of the furnace 26 or over partial areas, for example a number of downhill sections, e.g. B. 8 to 12 ken Gefällestrec ^¬, have a constant inclination. As can be seen from Figure 2, the section of the furnace shown and possibly the entire furnace 26 is inclined to the horizontal. As a result, the support rails 34, 35 have a continuous gradient and the individual gradient sections 36 and 37 adjoin one another in a straight line.

The angle of inclination of the gradients 36, 37 can be chosen so that the pipes overcome the static friction and rolling friction, that is, they always begin to roll at any point where they are placed on the gradients 36, 37. In the exemplary embodiment according to FIGS. 2 and 3, the inclination is chosen to be lower. The pipes 30 roll on its own, the Haftrei ^¬ environment is not overcome, but the angle is greater than that of the rolling friction. Once the tubes 30 are bumped and rolling, they continue to roll. However, it is also possible, as will be described below, to continuously convey the pipes. This makes it possible to choose an even smaller angle of inclination.

Between the gradients 36 and 37 are each transport ^¬ 48. These devices take in the illustrated embodiments also have the function of stops 40 at the end of the respective gap distance 36 and 37. Each slope section 36 and 37 are assigned two star arrangements which form the transport devices 48 of a slope section. The two star arrangements of each support rail 34, 35 are rotatably connected to one another, in particular via a common shaft, or advantageously also outside of the furnace. In the embodiment shown according to FIGS. 2 and 3, a total of three arms are provided, the arms being arranged at a 120 degree angle to one another. It is also possible to provide more arms, for example five arms, see FIG. 5. The arm which is up or down in each case acts as a stop 40.

There are two options for litigation. On the one hand, continuous process control is possible. Due to the inclination of the slopes 36 and 37, the pipes 30 roll continuously and are kept perpendicular to the rolling direction by the transport devices 48 and only stopped briefly if necessary. On the other hand, it is possible that the pipes 30 have short breaks whenever they rest against the stops 40. FIGS. 2 and 3 accordingly show such a position in which the tubes 30 are in their resting phases. The star-shaped transport devices 48 rotate clockwise by 120 degrees. As a result, the arm that previously formed stop 40 is folded down and no longer blocks the rolling movement of the associated tube to the right. The following arm strikes the pipe 30 from below and thus gives it an impulse and possibly moves it over a certain distance until the pipe 30 rolls down the subsequent downhill section 36 or 37 and reaches the next stop 40. This is formed by the arm of the star-shaped transport device of the subsequent downhill section 36 and 37, which now stands upwards.

A high-temperature zone 38 is shown on the right in FIGS. In order to achieve several cycles in a cycle-wise work, the downhill sections 37 of this zone are additionally equipped with tabs which can be raised by means of a vertically acting lifting cylinder 56, this state being shown in FIG. In the retracted state, they do not protrude above the gradient 37. The arrangement described works as follows: If the tube shown on the far right in FIG. 2 lies at its associated stop and the circulating device 50 with the tab described is still retracted, the lifting cylinder 56 is actuated and takes the tab of each of the two Mounting rails 34, 35 which in FIG. gur 2 shown inclination. The pipe 30 now rolls to the left until it abuts the upstanding arm of the previous slope 36. After a while, the lifting cylinder 56 is lowered again, the tube can now roll to the right again, whereby it may receive a small pulse due to the star-shaped transport device of the previous downhill section 36 in order to trigger the rolling movement.

The exemplary embodiment according to FIG. 4 works similarly, except that here both support rails 34, 35 are raised over a certain number of downhill sections, for example 6 to 12 with the associated transport devices 48, so that the transport can now take place in the opposite direction, that is to say to the left , The raised position is shown in dashed lines in Figure 6. Again, the star-shaped transport devices 48 can be used to trigger the rolling. This can be done both in the Be ^¬ movement to the left and in the movement to the right. As can be seen from FIG. 4, the two support rails 34, 35 are articulated at the left end, and at the right end they are articulated to a piston rod of the vertically acting lifting cylinder 56. As a result, the two inclination positions, which are shown in broken lines in FIG. 6, are achieved. This training is particularly suitable for gradients 37 in the high temperature range.

In the exemplary embodiment according to FIG. 5, five-armed star arrangements are provided, which form the transport devices 48. Each individual star is engaged with the associated tube 30 like a chain gear. For this purpose, the star arrangements have concave inner surfaces which essentially correspond to the outer contour of the tube 30. The pipe 30 unwinds in the thus formed tooth of the star arrangements, characterized there is only a male mini ^¬ friction between the tubular sheath and the surfaces of Sternanord ^¬ voltages.

Adjacent transport devices 48 are arranged next to one another such that the arms of the star arrangements overlap, and are accordingly laterally offset transversely to the longitudinal direction 28 of the furnace. As a result, a transport device 48 can transfer a pipe 30 to the adjacent transport device without a gap occurring in the transport process.

In the embodiment of Figure 5, the drive shafts are Transport devices 48 above the tubes 30, while in the ^previous embodiments ^{¬ are} below this. As long as the tube 30 is brittle - that is to say up to approximately 800 degrees in the heating area and from 800 degrees in the cooling area - the stars preferably grip from below, in accordance with the exemplary embodiments according to FIGS. 2 to 4, while they are above 800 degrees preferably grasp from above, see FIG. 5. This arrangement has the advantage that if there are any fragments on the support rails 34, 35, the tube can deflect upwards by 30 to 800 ° and is therefore not squeezed between the rails and the star. Above the temperature threshold, the tube 30 can deform hot plastic if this should be necessary. The arrangement of the drive shafts ^¬ upper half of the tubes has that in a possible breakage the fragments to fall freely down the advantage and will not get stuck on the shafts or between these. For this reason, it has proven to be advantageous in principle to drive the stars via stub shafts mounted on one side and not via a continuous shaft.

According to FIG. 5, the pipes which have sleeves 31 are arranged alternately. Seen from above, the sleeves are alternately left and right.

P A T E N T A N S P R Ü C H E

1. Method for firing ceramic tubes (30), in which

green tubes (20) are introduced into an oven (26), pass through the oven (26) transversely to the longitudinal direction (28) of the oven (26) and are removed from the oven (26) as finished ceramic tubes (30),

- The tubes (30) are conveyed through the furnace (26), in particular continuously rolling through the furnace (26),

- The tubes (30) rest on two support rails (34, 35) running in the longitudinal direction (28) of the furnace (26), the support rails (34, 35) forming a plurality of downhill sections (36, 37), along which the pipes are moved and

- each downhill slope (36, 37) a stop (40) is associated, which at the end of a slope (36, 37) is provided and direction transverse to the longitudinal ^¬ (28) of the furnace (26) is disposed, said tubes (30 ) are sufficiently moved during the movement along the slope (36, 37) that they can align themselves transversely to the longitudinal direction (28) when striking the respective stop (40).

2. The method according to claim 1, characterized in that at least egg ^¬ nige downhill sections (36, 37), preferably each downhill section (36, 37) is assigned a transport device (48), the tubes (30) from a downhill section (36, 37) in the next slope (36, 37) moved or promotes.

3. The method according to claim 1, characterized in that a number of downhill sections (36, 37), preferably all downhill sections (36, 37) form a continuous, continuously extending downhill section.

Claims

4. The method according to claim 1, characterized in that the tubes (30) rest on the support rails (34, 35) so that each outside of each guide 1/4 of the total weight and between the support rails ^¬ NEN (34, 35) each half of the total weight of the tube (30) is found.

5. The method according to claim 1, characterized in that the tubes (30) have an integrated sleeve (31).

6. The method according to claim 1, characterized in that the green tubes (20) are immersed in a glaze bath (22) before being introduced into the oven (26), preferably ring areas on the outer jacket of the tubes (30) to which the Contact with the mounting rails takes place, are covered when immersed.

7. The method according to claim 1, characterized in that the tubes (30) at the beginning of a slope (36, 37) have a different rotational orientation than at the end of this slope (36, 37), in particular that the tubes (30) to the The ends of successive slopes (36, 37) have as different a rotation orientation as possible.

8. The method according to claim 1, characterized in that the furnace (26) has a high-temperature zone (38), that at least some of the gradients (36, 37) located in this high-temperature zone (38) are equipped with circulation devices (50) and that the tubes (30) stretch by this circulating device (50) at the beginning of the same gradient ^¬ (36, 37) are transported back and the slope section (36, 37) roll down again.

9. Furnace (26) for firing ceramic tubes (30), which has an entrance into which green tubes (20) are introduced which pass through the furnace (26) transversely to the longitudinal direction (28) and which has an exit from which the finished ceramic tubes (30) are removed, two support rails (34, 35) running in the longitudinal direction (28) being provided in the furnace (26), on which the tubes (30) rest and these support rails (34, 35 ) form a multiplicity of downhill sections (36, 37) along which the pipes (30) can roll down, each of which is Slope section (36, 37) is assigned on the one hand a stop (40) which is provided at the end of the respective slope section (36, 37) and is arranged transversely to the longitudinal direction (28) of the furnace (26).

10. furnace (26) for firing ceramic tubes (30) according to claim 9, characterized in that each slope (36, 37) is assigned a Transportvorrich¬ device (48) and at least the slopes (36, 37) in the high temperature zone (38) a circulation device (50) is assigned.