GB2102842A - A heated trough calender - Google Patents

Abstract

A heated trough calender for drying and smoothing damp pieces of linen, is provided with contact surfaces which are heated by means of a flowable heat carrier medium. A pre-drying unit is provided as a rotatably mounted, drivable cylinder 9, to the outer surface of which there is fixed a pipeline system 16 which is connected a transfer device 9 connected to a line for collecting condensate from the troughs at the inlet end 11 and to an abduction system for removing condensate from the cylinder 9 at the outlet end. In Fig. 2, the system 16 comprises two helical parallel pipelines 17, 18 the inlets 19, 20 and outlets 21, 22 are positioned at opposite ends of the cylinder 9. In Fig. 3 (not shown), the system (16) is divided into sections (26) in which helical pipelines (27) are provided. <IMAGE>

Description

SPECIFICATION A heated trough calender The invention relates to a heated trough calender for drying and smoothing damp pieces of textile material e.g. linen, which comprises at least one calender unit, consisting of a rotatably mounted and drivable calender cylinder and at least one stationary calender trough, which partly embraces the calender cylinder jacket, as well as trough bridges connecting successive calender units, the calender troughs and the trough bridges having heating systems, which are feedable with a heat carrier medium that is capable of flowing, and a pre-drying unit, which is heatable by means of the heat carrier medium abducted from these heating systems, being arranged upstream of the first calender unit.

These days, the problem of saving energy and of optimising the use of energy in technical processes becomes more and more important.

The energy-intensive process of drying textiles, such as pieces of linen, as takes place for example in steam-heated trough calenders, is also affected thereby. The aim is to reduce the specific energy requirement for drying a piece of linen.

One way of doing this is, inter alia, the predrying of those pieces of linen prior to the calendering process proper. There are already known heated trough calenders wherein the pieces of linen are pre-heated and pre-dried prior to the actual calendering process by means of contact with a heated surface (DE Gm 1 789 610; 8 d, 20/04). The linen is passed over a heated external surface of the calender trough. However, in this process the cold damp laundry has to slide on the heated contact surface. The thermal energy required for pre-heating and pre-drying the linen is taken from the calender trough, that is to say it has to be additionally expended. Furthermore, it is difficult to transfer this principle to multiple trough calenders.

It has therefore already been proposed to use the heat carrier medium that is abducted from the heating systems of the calender troughs and trough bridges and still has a considerable heat content for heating a pre-drying unit arranged upstream of the first calender unit (DE Patent Application P 30 41 244.3). This technical solution relates to a trough calender which is heated by means of steam and is equipped with a rotatably mounted drivable pre-drying cylinder.

For the purpose of being pre-dried, the pieces of linen are guided so as to be in abutting contact with the external wall of the pre-drying cylinder and so as to partly rotate therewith. The predrying cylinder is heated in that the condensate obtained from the calender troughs and trough bridges is collected in a vessel and is fed from this vessel by means of a pump to channels which are provided in the inner surface of the hollow predrying cylinder and extend between the two front ends thereof. The condensate is fed to these channels at one front end of the pre-drying cylinder and is abducted at the opposite front end thereof. However, since the condensate is subjected to high pressure, the depressurisation inevitably coming about at the suction side of the pump quickly leads to the destruction of the pump due to the effect of cavitation.

Furthermore, the heat transfer to the entire outer surface of the pre-drying cylinder attainable with this arrangement of the channels is neither adequate nor even.

In order to pre-heat and pre-dry the pieces of linen satisfactorily, there are provided in the zone of the pre-drying cylinder further guide elements, with which the pieces of linen have to be brought into contact. However, these guide elements are heated with live steam, that is to say additional thermal energy is required. Consequently, the intention of saving energy in the heated trough calender is not taken into account.

It is the object of the invention to improve the energy balance of the heated trough calender.

The task underlying the invention is to provide a heated trough calender which allows the effective and uniform re-use of the waste heat from the heat carrier medium serving for heating the calender troughs and the trough bridges.

According to the invention we provide a heated trough calender for drying and smoothing damp pieces of textile material, which comprises at least one calender unit, consisting of a rotatably mounted and drivable calender cylinder and at least one stationary calender trough which partly embraces the calender cylinder jacket, as well as trough bridges connecting successive calender units, the calender troughs and the trough bridges having heating systems, to which a heat carrier medium which is capable of flowing can be fed, and a pre-drying unit, which is heatable with the heat carrier medium abducted from these heating systems, being arranged upstream of the first calender unit, characterised in that the pre-drying unit is designed as a rotatably mounted, drivable pre-drying cylinder, to the outer surface of which there is fixed a pipeline system which is connected to the outlets of the heating systems via a collection line at the inlet end and to an abduction system for the heat carrier medium of the heated trough calender at the outlet end.

The heated trough calender according to the invention has the advantage that the considerable quantity of heat of the trough calender which is still contained in the heat carrier medium abducted from the calender troughs and the trough bridges is not lost as waste heat but can be utilised in the drying process of the linen. After all, the heat extracted from the heat carrier medium in this way may be up to 1/3 of the quantity of heat which has to be expended for drying the linen in one of the following calender units. This results in a considerable reduction of the specific energy requirement of the heated trough calender, which means in other words that a substantially higher quantity of the water contained in the linen can be evaporated with the same expenditure of energy.

The pre-drying cylinder according to the invention ensures a maximum heat transfer, which, above all, is even over the entire width thereof, from the heat carrier medium to the surface of the pre-drying cylinder and thus to the pieces of linen resting thereon.

However, it is also possible to vary the heating of the pre-drying cylinder in specific sections of its outer surface. This allows a larger quantity of heat to be fed to the pre-drying cylinder, for example in the mostly more heavily utilised central zone of the entire working width of the heated trough calender.

The invention furthermore enables the consumed heat carrier medium to be fed to the pre-drying cylinder under the pressure which prevails in the heating elements of the calender troughs and the trough bridges. Consequently, a separate condensate pressure reduction system becomes unnecessary in superheated steam trough calenders, and the condensate can be abducted from the trough calender at the operating pressure.

The invention will hereinafter be explained in more detail with the aid of an exemplified embodiment. In the drawings FIGURE 1 shows a diagrammatised lateral view of a heated trough calender, FIGURES 2 and 3 show views of pre-drying units equipped according to the invention, and FIGURE 4 shows a detail IV shown in Fig. 2.

The heated trough calender according to the invention has two parallel side supports 1, in which at least one calender cylinder 2 is rotatably mounted. Each calender cylinder 2 is drivable and is embraced by at least one calender trough 3, which has the shape of a cylinder jacket segment.

In the present example, a calender cylinder 2 and a calender trough 3 form a calender unit 2; 3.

If the heated trough calender comprises several of such calender units 2; 3 in succession, then the successive calender troughs 3 are connected by trough bridges 4.

Both the calender troughs 3 and the trough bridges 4 are heated. In most cases, a heat carrier medium capable of flowing, such as steam, heat carrier oil, etc., serves for this purpose.

The invention will be described by the example of a trough calender which is heated with high pressure steam.

The calender troughs 3 and the trough bridges 4 are equipped in known manner with heating elements, through which the heat carrier medium flows. Since the manner in which the heat carrier medium is fed to the heating elements is not of importance in the present context, the means serving for this purpose have not been shown in the drawings.

The steam in the heating elements transmits a considerable proportion of its heat to the calender troughs 3 and the trough bridges 4 and is thereafter available, under the conditions prevailing therein (temperature 1 900 C; pressure approximately 1.2 MPa), as a saturated condensate. This condensate is fed from the calender troughs 3 and the trough bridges 4 via condensate traps 5 to a condensate collection line 6 which opens into a transfer device 8 which is connected to a pre-drying unit 7.

The pre-drying unit 7 is a drivable pre-drying cylinder 9 which is rotatably mounted in the side supports 1 and the diameter of which is similar to that of a calender cylinder 2. It is equipped with a known laundry guiding device 10 in the form of belts, which extend in parallel, or an endless revolving screen belt.

The transfer device 8 is also sufficiently known in its kind and serves for transferring a medium, which is capable of flowing, from a stationary line to a revolving machine element and vice versa.

Connected to an inlet 11 of the transfer device 8 is the condensate collection line 6, while an outlet 12 is connected to a line 13 which leads via a regulator 14 to a condensate abduction system 1 5 for the steam-heated trough calender or the entire laundry operation.

According to the invention, a pipe line system 1 6 has been fixed to the outer surface of the predrying cylinder 9. This system is connected to the transfer device 8 and is thus in communication with the condensate collection line 6 at the inlet end and with the condensate abduction system 15 via the line 13 and the regulator 14 at the outlet end.

The pipeline system 16 preferably has a helical configuration. This configuration is discernible in Fig. 2 which shows a particularly advantageous constructional form of the pre-drying cylinder 9 forming part of the invention. In this construction, the pipeline system consists of two helical pipelines 17; 18 which extend in parallel side by side and over the entire outer surface of the predrying cylinder 9 and whose inlets 19; 20 and outlets 21; 22 are positioned at the opposite front ends 23 of the pre-drying cylinder 9. The inlets 19; 20 of the pipelines 17; 18 are connected through a branching line 24, which is provided in the interior of the pre-drying cylinder 9, to the inlet 11 of the transfer device 8, while a similar line 25 connects the outlets 21; 22 of the pipelines 17; 1 8 to the outlet 12 of the transfer device 8.

Fig. 3 shows another possible constructional form of the pre-drying cylinder 9. Herein, the pipeline system 16 has been divided, with respect to the length of the pre-drying cylinder 9, into several sections 26, in which pipelines 27 are provided in a likewise helical manner. For clarity's sake, the pipelines 27 have been elongated in Fig.

3. However, in a practical construction, the lead of the helix is such that the individual windings of the pipelines 27 lie closely side by side.

As in the design shown in Fig. 2, the inlets 28 of the pipelines 27 are connected through a line 24 to the inlet 11 of the transfer device 8 and the outlets 29 are connected through a line 25 to the outlet 12 thereof.

It is advantageous if, as shown in Fig. 3, the individual sections 26 of the pipeline system 16 are so arranged that there comes about a shape of the pre-drying cylinder 9 which is symmetrical about a central plane 30.

In order to avoid heat losses, the front ends 23 of the pre-drying cylinder 9 are thermally insulated.

Both the pipelines 17; 18 shown in Fig. 2 and the pipelines 27 shown in Fig. 3 are so designed in cross section that the laundry to be dried comes into good contact therewith. A particularly advantageous cross-sectional form is shown in Fig. 4 as a detail IV of Fig. 2.

The laundry can rest directly on the pipelines 17; 18 and 27 respectively. However, it is also possible to provide for the interposition of a highly heat-conducting screen 31, as shown in Fig. 3.

The mode of operation of the steam-heated trough calender according to the invention is as follows: The pieces of linen to be calendered are passed in a spread state to the steam-heated trough calender in the usual way, for example by means of a feeding machine which, as viewed in the direction of passage 32, is arranged upstream of the steam-heated trough calender. They are grasped by the laundry guiding device 10 of the pre-drying unit 7 and, bearing firmly against the pre-drying cylinder 9, that is to say without any movement relative to the surface thereof, are guided so as to partly rotate with this cylinder.

Thereafter, the pieces of linen pass in known manner through the following calender units 2; 3 and are dried and smoothed therein. Due to its contact with the outer surface of the pre-drying cylinder 9, the laundry is heated and pre-dried so that the contact surface of the calender trough 3 of the first calender unit 2; 3 can be utilised much better for drying and smoothing the laundry. The temperature difference between the laundry and the calender trough 3 is substantially lower, that is to say the laundry has to be heated to a lesser degree in order to cause the water contained therein to evaporate.

For this purpose, the pre-drying cylinder 9 is heated with the consumed heat carrier medium, which in this case is the condensate of the steam serving for heating the trough calender.

The condensate is fed under the high pressure which prevails in the heating elements of the calender troughs 3 and the trough bridges 4 from these via the condensate traps 5 and the condensate collection line 6 to the inlet 1 of the transfer device 8. It passes through the line 24 to the inlets 19; 20 of the pipelines 17; 18 and the inlets 28 of the pipelines 27 respectively and passes through these lines. Thereafter, it is fed through the line 25, which is connected to the outlets 21; 22 and 29 respectively, to the outlet 1 2 of the transfer device 8. The regulator 14 connected into the line 13 ensures that the condensate is introduced into the condensate abduction system 15 at a constant pressure.

The important feature of the construction shown in Fig. 2 is the fact that the condensate flows through the pipelines 17 and 18 in opposite directions from one of the two front ends 23 of the pre-drying cylinder 9 to the respective other front end 23. This ensures that the outer surface of the pre-drying cylinder 9 is evenly heated over the entire length thereof.

By contrast, the construction shown in Fig. 3 allows specific sections of the outer surface of the pre-drying cylinder 9 to be fed with varying quantities of condensate and thus to vary the heating of these sections.

This may be of advantage, for example, in the event of the calender being insufficiently covered, if the central zone of the pre-drying cylinder 9 comes into contact with considerably more pieces of linen than the edges thereof do, so that more heat is withdrawn from this zone.

This variation in the supply of condensate to the sections 26 of the pipeline system 1 6 may be brought about, for example, by dimensioning the branches of the line 24 differently.

Claims (6)

1. A heated trough calender for drying and smoothing damp pieces of textile material, which comprises at least one calender unit, consisting of a rotatably mounted and drivable calender cylinder and at least one stationary calender trough which partly embraces the calender cylinder jacket, as well as trough bridges connecting successive calender units, the calender troughs and the trough bridges having heating systems, to which a heat carrier medium which is capable of flowing can be fed, and a pre-drying unit, which is heatable with the heat carrier medium abducted from these heating systems, being arranged upstream of the first calender unit, characterised in that the pre-drying unit (7) is designed as a rotatably mounted, drivable pre-drying cylinder (9), to the outer surface of which there is fixed a pipeline system (16)which is connected to the outlets (21;; 22; 29) of the heating systems via a collection line (6) at the inlet end and to an abduction system (1 5) for the heat carrier medium of the heated trough calender at the outlet end.

2. A heated trough calender as claimed in Claim 1, characterised in that the pipeline system (16) is helically arranged on the outer surface of the predrying cylinder (9).

3. A heated trough calender as claimed in Claims 1 and 2, characterised in that the pipeline system (16) consists of two helical pipelines (17; 18) which extend in parallel side by side and over the entire length of the outer surface of the predrying cylinder (9) and whose inlets (19; 20) and outlets (21; 22) are positioned at the opposite front ends (23) of the pre-drying cylinder (9).

4. A heated trough calender as claimed in Claim 1, characterised in that the pipeline system (16) is divided, with respect to the length of the predrying cylinder (9), into several sections (26), each of the pipelines (27) associated with these sections (26) being connected with its inlet (28) via a common line (24) to the collection line (6) and with its outlet (29) via another common line (25) to the abduction system for the heat carrier medium.

5. A heated trough calender as claimed in Claims 1 and 5, characterised in that the sections (26) of the pipeline system (16) are arranged so as to be symmetrical about a central plane (30) of the pre-drying cylinder (9).

6. A heated trough calender substantially as described with reference to the accompanying drawings.