IL44673A - Evaporative cooling of tools in glass-working machines - Google Patents

Abstract

1436034 Cooling moulds and dies HER. MANN HEYE 25 Feb 1974 [2 May 1973] 8474/74 Headings C1 and H7 In the cooling of glassware forming moulds or dies by spraying a liquid thereupon, the surface of the mould towards which the liquid is sprayed is covered by at least one metal plate. As shown a mould half 20 is sprayed with water from spray nozzles 37, the water impinging on metal plates 30 screwed to the mould. A lining 35 comprising a metal screen mesh, glass fibre or asbestos mat is provided between the plate 30 and the mould half 20. The external surface of the plate may be provided with a top cladding for retaining or distributing the cooling liquid. The cooling liquid is preferably water which is free of salts and lime and contains a wetting agent. [GB1436034A]

Description

44673/3 EVAPORATIVE COOLING OF TOOLS IN GLASS-WORKING MACHINES in JUT nii rm iin:. ,~πκη V'B mm On nrps The present invention relates to an apparatus for carrying out the evaporative cooling of tools in glass-working machines, for example press dies and moulds, with a cooling, liquid . . "■ "- · ' • A known arrangement of. this type is described , in the article "Methoden der Formenki!lhlung an Glasverarbeitungs-maschinen" (Methods for the Cooling of Moulds in Glassworking Machines) , by Rudolf ille in Volume 7, " onstruktion und Betrieb von Glasverarbeitungsmaschinen" (Construction and Operation of Glass-working Machines) / published by the Deutsche Glastechnische Gesellschaft e.V., Verlag der Deutschen Glastechnischen Gesellschaft, Frankfurt am Main, 1961, pages 35 to 43. Basically, in these known methods, nipples are screwed into the external wall of a mould in suitable positions, into which cooling water is dropped. The following disadvantages are inherent in this known solution: Reat sinks in the form of screved-in nipples are fixed locally upon the surface of the mould. The spatial extent of each of these known heat sinks is naturally comparatively small, because strict limits must be set upon the size of the thread diameter of the threaded nipples . Known moulds become expensive by. fitting heat sinks. The known moulds must also have comparatively thick walls in order, in the first place, to allow the nipples to be screwed in and, in the second place, because of the very strict localisation of the heat sinks, to allow a satisfactory temperature distribution to be achieved over the wall of the mould facing the glass by means of the wall thickness. It is in fact possible to provide a comparatively large number of nipples per unit surface, but this increases the capital outlay on the construction. The known mould, because. of its large wall thickness and the nipples screwed into it, together with the cooling wate lines, ha§ comparatively large external dimensions., which becomes .. particularly disadvantageous if only a strictly limited surface area is provided for the installation of the moulds, in particular moulds for small hollow glass bodies. This. applies to an increased extent in a case of machines with double moulds.

These strictly limited localised known types of heat sink result ' in formation. of an accumulation of water at the base of the nipple, due to the water droplets. Evaporation proceeds under- or surface neath a liquid meniscus/and therefore under adverse conditions. In conditions of sufficiently great overheating., there is a risk of film evaporation at an extremely small heat transfer coefficient (compare the above cited treatise of Wille, page 39, Figure 8) . Furthermore, difficulties are encountered in attempts to optimise the spatial location of the known heat sinks, because the heat sinks cannot be moved a 'will over the surface of the mould. Cooling of the base of a split. mould is not provided. No possibility is given for influencing the magnitude of the heat transfer at the known.heat sinks..

In another known arrangement of the above-mentioned type (Austrian Patent Specification 24,927) , water is dripped or squirted in controllable amounts into the hollow wall of a mould. The resulting water vapour flows through the mould cavity and likewise, performs the function of cooling. ;A disadvantage of this arrangement is that the quantity of: water for each mould impinges only upon a comparative3.y small region of the mould surface. This regio " is under cooled in the manner of a heat sink, whilst on account of the large quantity of heat ; per unit surface in this region, the Leidenfrost phenomenon, ■ that is to say film evaporation, also occurs in this region and the heat transfer coefficient drops sharply in an undesirable manner. The . temperature of the region is fixed at a constant value of about 110°C, because of the water located there. A temperature gradient forms from the remaining parts of the mould wall to this region, which results in heat transfer in the wall by thermal conduction. From the additional cooling of the rest of the mould wall by convective heat transfer by means of water vapour, no discernible improvement in the cooling of such parts of the wall ca be expected, because of the very small volume of vapour available. Moreover, no prescribed path is provided for the vaporised water. By the use of this known type o cooling mechanism, it is not possible to achieve even an approximately uniform temperature of the mould surface facing the glass. The mould wall must be hollow and comparatively . thick and it is therefore expensive and;"requires a great deal of valuable space, which cannot be made available, in particular in modern compact fully automatic moulding systems .. ' The mould is comparatively heavy and expensive.

It is also known, from German Published Specification 2,150,193, to spray cooling liquid directl on to the surface, which may if required, be a profiled surface, of the tool which is to be cooled. ".. .

The present invention is based upon the aim of providing improvement in the cooling of the tools and in particular of avoiding to a large extent film evaporation of the cooling liquid under conditions of normal operation of the tools.

In accordance with the present invention, a jacket assembly is provided so as substantially to cover and contact ■ the surface of the tool to be cooled.

In this arrangement, advantageously, care is 'to" be taken that the difference (superheating) . between the temperature of the surface of the jacket assembly contacted by the cooling liquid and the evaporation temperature of the cooling liquid, under normal operation of the ' tool : ',■ lies in the range of the critical temperature difference at the boundary between bubble evaporation and film evaporation and preferably lies in the region of bubble evaporation. By substantial or complete exclusion of compressed air as the cooling medium, which otherwise could result in. noise loads of 90 to 100 dB, the invention affords valuable contribution to the design of working spaces favourable to the environment.

The surface of the tool which is to be cooled may possess a more or less high degree of natural roughness, or may even be intentionall profiled, for example by means of cooling ribs. Moreover, existing moulds may also be fitted with a jacket assembly according to the invention. The roughness or the profiling of the surface. can also be presen additionally or only at .that side of the jacket assembly facing the tool. The sole condition to be satisfied is that between the tool . and the jacket assembly there shall exist a sufficiently large total contact surface for the conduction of heat, which prevents the building up of a heat bank in the wall of the . tool,- and secondly allows the establishment of the desired magnitude of the superheating at the surface of the jacket assembly contacted by the cooling liquid. When the jacket assembly is releasably coupled to the tool, the tool can, as desired, be set up in the conventional way as well as in the. manner according to the invention. The application, of the '. cooling liquid to the jacket assenibly may be effected in any desired manner.- In one preferred embodiment of the invention, the-, jacket assembly comprises a metal. plate arranged for application to ' the surface of the tool to be ccoled. With this, the · jacket assembly becomes comparatively inexpensive, and can be ' set up on an extensive operating scale. The metal plate can be closed or may be provided with perforations. " , ■ '. * According to a preferred feature of this embodiment, a lining is arranged between the metal. plate and the surface · of the tool to be cooled.. This makes it possible to use a comparatively thin metal plate under conditions of uniform temperature drop, through the jacke assembly. The intermediate lining can be arranged to influence the size of -the. contac surface between the jacket assembly and the tool. Preferably, the intermediate lining comprises at least. one temperature-resistant non-metal. In this way, it is possible to achieve, v;ith a small thickness of the intermediate lining, a . .. comparatively large contact surface with. adequate heat transfer. ■ ■ · ·.' ■ lining · According to another preferred arrangement,- the/comprises a metal screen mesh. This has the advantage of providing a comparatively small contact surface with the tool surface to be copied on the one hand and with the metal plate on the other . hand. By .the. use of an arrangement ■ wherein the external surface of the jacket assembly contacted by the cooling liquid comprises a top cladding capeible of retaining the cooling liquid and/or distributing the cooling liquid, it is possible to hold and/or to distribute the cooling liquid to the desired degree. If the top cladding is not inherently stable, or if. it is so fragile as to require protection from damage, it is possible to apply externally to the top cladding a further stabilising retaining layer, for example a form of retaining ^grid.

Distribution of the cooling liquid is desirable in particular if. the cooling liquid is applied only locally to the jacket assembly. \ For example, it is often the case that not all the regions of the surface of the jacket assembly can be reached or jet with a stream/of cooling liquid. In these cases, the top claddin provides for the delivery of cooling liquid to these regions also. Thus the outer surface of the jacket assembly ma have heat extracted from it in a. substantially uniform manner if evaporation of the cooling liquid takes place over as large a surface area as possible.

Another preferred arrangement consists in securing the acket assembly to the tool, for example by welding or riveting. This is recommended if the jacket assembly may remain permanently connected with the.,tool. . In other cases, the coupling of the jacket assembly to the tool may employ a form of releasable connection. This serves to allow for adaptation of a tool to different methods of cooling and also provides for easier repai and servicing of the jacket assembly and the tool.

Preferably, the jacket assembly is at least partly movable relative to the tool; . this is of particular advantage in the case of intermittent application of the cooling liquid to the jacket assembly, which is. attended by periodical thermal' expansion of the jacket assembly with respect to the tool. It is appropriate in this case to secure the jacket assembly at one point, so that at ail other points the. jacket assembly is free to move with respect to the tool in all directions relative to such fixed point. Another preferable arrangement is to urge the jacket assembly against the tool with a controllable force. This allows the magnitude of the total contact ; area between the jacket assembly and the tool to be controlled and therefore correspondingly influences the magnitude of the thermal conduction. In a similar manner, the magnitude of the thermal conduction can be controlled by using a jacket assembly which comprises a plurality of layers arranged to be urged together with a controllable force. .

According to a preferred embodiment of the invention, the apparatus includes one or more spray nozzles for spraying the cooling liquid, on to the jacket assembly. This arrangement ensures a reliable and uniform distribution of the cooling liquid over a comparatively large surface. region of the jacket assembly. For this purpose. the spray nozzles can advantageously be controlled in dependence upon the . temperature of the surface of the jacket assembly contacted by the cooling liquid for. the purpose of maintaining the desired level of the difference between the temperature of the jacket assembly surface contacted by the cooling liquid and the boiling temperature of the cooling liquid .

The invention also consists in a method of operating a glass-working machine, which comprises supplying a cooling liquid to . jacket assembly located substantially covering and in contact with the surface of a glass-working tool to be cooled. Preferably, the method involves the use of a prepared cooling liquid, most desirably a purified water freed from lime and salts ana containing an added vetting agent.

In order that the invention may be readily understood, preferred embodiments are described below-, by way of example, in . conjunction with the accompanying drawings, in which; ■ Fig. 1 shows a. longitudinal section through one half, of a finishing mould together with a jacket assembly applied thereto; ■ - ■ Fig. 2 shows a. cross section along the line II7-II. of Fig. 1; Fig. 3 a longitudinal section through another practical form of a finishing mould with a jacket assembly applied thereto; Figs. 4 and 5 show a partial section through a detail of ci mould with different types of jacket assembly mounted thereon ; Fig. 6 shows a view of the detail VI in Fig. upon an enlarged scale-; Fig,.7 shows a longitudinal section through a further practical form of a finishing mould with a jacket assembly mounted thereon; ■'_··■ Fig. 8 shows a schematic circuit diagram for supplying spray nozzles of a finishing mould with cooling liquid; Fig . 9 shows a longitudinal section through a press die with an internal jacket assembly ap lied thereto.

In Fig. 1, there is shown one half 20 of a finishing mould 23 in its closed condition, in which the halves of the ' finishing mould surround an axial portion of a base 25 of . the finishing mould.. The finishing mould half 20 is suspended in one half of a known type of finishing mould clamp 26, v/hich is partially shown in the drav/ing.

On the outside of the finishing mould half 20 a jacket assembly 30 is mounted by means of screws 27, the assembly consisting of a metal plate 33 and a non-metallic intermediate lining 35 between the metal plate 33 and the finishing mould half 20.

A number of spray nozzles 37 are arranged to spray cooling liquid in conical streams 39 on to the outside of the. metal plate 33, where the cooling liquid evaporates.

Fig. 2 shows that the jacket assembly 30 substantially covers the. surf ce v.'hich is to be cooled of the finishing mould half 20. .

The other half of the finishing mould, which is not:, shown in Figs.' 1 and 2, is provided, like the finishing mould half 20, with a similar jacket assembly, on to which cooling liquid is .likewise applied.

In Fig. 3, a finishing mould half 40 is provided,, like the . finishing mould half .20, with a jacket assembly 41, consisting of a metal plette 43 and a metal screen mesh or sieve 45 serving as an intermediate lining between.. the metal plate 43 and the mould half 40. Approximately at its centre, the jacket centering assembly 41 is secured by a/eenfosai screv; 47 to the half 40 of the finishing mould. Further screws 49 pass through the jacket assembly 41 with sufficient lateral clearance and are. screwed into the finishing mould half 40. The screws 49 serve the purpose of pressing the jacket assembly 41. to the desired extent against the finishing mould half 40 and thus, at the same time, serve to influence the extent of the contact surface area between the metal screen 45 and the finishing mould half . 0 and also between the metal screen 45 and the metal plate 43. This. arrangement again influences the extent of the thermal conduction between the finishing mould half 40 and the surface 50 of the jacket assembly 41 which comes into contact with the cooling ■ liquid. Due to the clearance between the screws 49 and the jacket assembly 41, the latter . can displace Itself at any side centering' of the/s8H¾.K« screv/ 47 to a greater or lesser extent with respect to the finishing mould half 40. Such displacements are necessary under conditions of varying thermal expansio of the finishing mould half 40 and the jacket assembly 41.· In Fig. 4, a jacket assembly 57 comprising a metal plate 55 is mounted upon a mould 53, whose, internal surface 5 is periodically charged with hot glass. The metal plate 55 is pressed against the mould 53 by means of screws 59.

Fig. 5 shows a practical form of the invention, which is modified as compared with Fig. 4 insofar as a jacket assembly 60 also includes a top cladding 63 applied externally to the . ■ metal plate 55. The top cladding 63 consists here of a metal mesh screen, vhose function is to hold cooling liquid which is applied to the outside of the jacket assembly 60, that is to say to prevent the liquid running off and/or to distribute this cooling liquid over the external surface of the jacket, asseiubly 60. ' The enlarged view in Fig. 6 shows an area of. comparativel slight roughness 65 in the metal plate 55 and an area of comparatively greater roughness or a. profiled area 67 of the mould 53. The sum of all the partial contact areas between the mould 53 and the metal plate 55 in the region . ·, .'"· of roughness peaks .; constitutes a total contact area, through which there takes place thermal conduction from the mould 53 to the metal plate ' 55.

In Fig. 7, a jacket assembly 71 is provided on the outside of a finishing mould half 70. The jacket assembly 71 consists of an intermediate lining 73 in the form of a metal sieve or screen, a metal plate 75, a top cladding 77 and. a retaining layer 79 in the form of a further comparatively large mesh sieve or screen. The : function of the retaining layer 79 is to afford protection from external damage for the fragile top cladding 77, which serves to retain and distribute the cooling liquid, and to hold such top cladding 77 in good uniform contact .wi h the metal plate 75. The jacket assembly 71 is- secured to the finishing mould half 70 screw 80 and is also pressed against the mould half 70 with the desired force by means of screws 81.

In the schematic circuit diagram according to Fig. 8, prepared water is. aken from a tank 90, conducted . through a filter 91 and fed by a pump 93 in a line 95, which, is made safe by a pressure limiting valve 96. From the line 95, the . cooling liquid proceeds into three branch lines 98, 99 and 100, in which pressure control valves 103, 104 and 105 respectively are inserted. In each of the branch lines 98, 99 and 100, a two-way/two position valve 108, 109 and.110 is located, also.

The branch line 98 supplies lower spray nozzles 113 with cooling liquid, of which only two are shown in the drawing, the branch line 99 supplies centre spray nozzles 115, of which again only two are shown, and the branch line 100 supplies upper spray nozzles 117. In Fig. 8, a finishing mould 120 is cooled, this mould comprising a base 121 of a finishing mould, two finishing mould halves 123 and 124 and two neck mould halves .126 and 127. The halves 123 and 124 of the finishing mould and the neck mould halves 126 and 127 are fitted respectively with a . jacket assembly 129, 130, 131, 132, upon which cooling liquid is sprayed by the spray nozzles 113 to 117.

A temperature sensor 135 is connected through a line 137 with the input of a controller 140- An end switch 141 is connected over a line 143 to a further input of the controller 1.40. Three, output lines 145, 146 and 147.lead respectively to an electromagnet of the electromagnetically-operable valves 108, 109 and 110.

In an operating cycle, as soon as the halves 123 and 124 of the finishing mould have reached a position at which the spraying is to begin, a signal is generated. at the end switch' 141 and fed into the controller 140. : The controller 140 control's the valves 108, 109 and 110. through the lines 145, 146 and 147 and switches' hese valves into the open or through-flow position shown in Fig. 8, in which all of the spray nozzles 113 to 117 spray liquid on to the finishing, mould.120. The . duration of spraying for the individual spray nozzles is controlled by the temperature sensor 135, which causes a resetting of the valves 108, 109 and 110 into their closed positions when the measured temperature lies belov.7 a predetermined value, that is to say the cooling of the finishing mould 120 has progressed to a sufficient degree. It is also possible to fit a plurality of such temperature sensors a different positions of the finishing mould 120, for example to fit them to the neck mould halves 12G and 127, in order to determine the spraying duration of the respective individual spray nozzles.

In Fig. 9, a press die 150 is provided on its inner surface which is not contacted by the glass with a lining, or ■ jacket 151, which is held in the press die 150 fay means of a screw threaded ring 153. By means of a spider 155, the ring- 153 also supports a spray nozzle 157/ which sprays the cooling liquid on to the inside of the j cket 151. In the same way as described in relation to the previous embodiments, the jacket 151 can be of multi-layer construction and can also be. locally secured to the press die.

Claims (20)

44673/2 WHAT IS CLAIMED IS:

1. An apparatus for carrying out the evaporative cooling of tools in glass-working machines comprising a plate-like structure arranged to substantially cover and contact the surface to be cooled of the tool, and means for applying to an external surface of the structure a liquid which evaporates on contact therewith.

2. An apparatus according to claim 1, wherein at least one of (a) the face of the tool opposite the plate-like structure and (b) the sur-face of the plate-like structure facing the tool is provided with a roughened or profiled surface.

3. An apparatus according to claim 1 or 2, wherein the said structure comprises a metal plate arranged for application to the surface of the tool to be cooled.

4. An apparatus according to claim 3, wherein a lining is arranged between the metal plate and the surface of the tool to be cooled.

5. An apparatus according to claim 4, wherein the intermediate lining comprises at least one temperature-resistant non-metal.

6. An apparatus according to claim 5, wherein the intermediate lining comprises a glass fibre or asbestos mat.

7. An apparatus according to claim 4, wherein the intermediate lining comprises a metal screen mesh.

8. An apparatus according to any preceding claim wherein the external surface of the plate-like structure 44673/2 contacted by the cooling liquid comprises a top cladding capable of retaining the cooling liquid and/or distributing the cooling liquid.

9. An apparatus according to claim 8, wherein the top cladding is arranged to retain or distribute the cooling liquid by capillary force.

10. An apparatus according to any preceding claim, wherein the plate-like structure is secured to the tool.

11. An apparatus according to any of claims 1 to 9, wherein the plate-like structure is releasably connected to the tool.

12. An apparatus according to claim 11, wherein the plate-like structure is at least partly movable with respect to the tool .

13. An apparatus according to any preceding claim, wherein the plate-like structure can be urged against the tool with a controllable force.

14. An apparatus according to any preceding claim, wherein the plate-like structure comprises a plurality of layer arranged to be urged together with a controllable force.

15. An apparatus according to any preceding claim, which includes one or more spray nozzles for spraying the cooling liquid on to the plate-like structure.

16. An apparatus according to claim 15, wherein the spraying period of the spray nozzles is controllable in dependence upon the temperature of the surface of the plate- 44673/2 ^ like-structure contacted by the cooling liquid for the purpose of maintaining the desired level of the difference between the temperature of the plate-like structure surface contacted by the cooling liquid and the boiling temperature of the cooling liquid.

17. An apparatus according to claim 1, substantially as described with reference to the accompanying drawings .

18. A method of operating a glass-working machine, which comprises applying a cooling liquid to an external surface of a plate-like structure located so that it substantially covers and contacts the surface )to be cooled'of a glass-working tool¾ so that the liquid evaporates on contact with the structure.

19. A method according to claim 18, wherein. purified water freed from lime and salts and containing an added wetting agent is used as the cooling liquid.

20. A method according to claim 19, wherein the cooling liquid comprises purified water freed from lime and salts and containing an added P.O.Box 33116, Tel Avi Attorneys for Applicant