GB2087430A - Plating Apparatus - Google Patents

Abstract

A plating line unit 10 for assembly with one or more other similar units, to form an electro or electroless plating line comprises at least one free-standing tank 42, a cover 30 having an aperture to provide access to the top of the tank, four legs (e.g. 12, 14) each supporting a corner of the cover and trunking 80 for housing electrical equipment and supply lines positioned over the rear of the cover. A jig for supporting plate-form workpieces in a plating tank comprises a framework the bottom of which provides support means for the workpieces and first 184 and second 188 reception means for receiving respective opposed upstanding edge portions of each workpiece. A reciprocable cathode for assembly (figs. 10-12, not shown) comprises a bar (192, 194) having secured to its undersurface a pad of self lubricating synthetic resin (e.g. PTFE) which slidingly engages in a channel of similar material 212. Electroplating apparatus comprises a framework of weldable corrosion resistant plastics material (e.g. polypropylene) which supports a number of pre-treatment and/or plating tanks. <IMAGE>

Description

SPECIFICATION Plating Line Construction This invention relates to the construction of electro and electroless plating lines which find particular, but not exclusive, application in the plating of printed circuit boards PCBs).

Conventional plating lines suffer from many drawbacks: electrical equipment is normally mounted below solution levels at the front or rear of the tanks and the connecting wiring not only hinders access to the tanks but its exposed position renders it vulnerable to damage and presents a potential danger to personnel; access to the drain connections to the tanks is difficult; the tanks are commonly supported or located by a mild steel tubular frame that is externally coated with a plastics coating which, if damaged, renders the underlying steel liable to corrosive attack by the chemicals used; the floor beneath the tanks is liable to attack by spilt treatment and plating solutions as it cannot be properly hosed down; and the line cannot be readily re-arranged to accommodate desired variations in the plating process.

By the adoption of the various aspects of the present invention these drawbacks are overcome or lessened and according to a first aspect of the present invention there is provided a plating line unit for assembly with one or more other similar units to form an electro or electroless plating line, the unit comprising at least one free-standing tank, a cover having an aperture to provide access to the top of the tank, the cover preferably also having a dependent lip projecting into the mouth of the tank and being partially supported by the tank, four legs each supporting a corner of the cover and, if the unit is to be juxtaposed with a neighbouring unit, each leg adjacent said neighbouring unit being provided with means to support a respective adjacent corner of the cover of the neighbouring unit, and trunking for housing electrical equipment and supply lines positioned over the rear of the cover, the unit preferably being constructed of polypropylene or similar material which is resistant to corrosive attack by the chemicals used in plating processes.

A leg provided with said means to support a corner of a neighbouring unit is preferably a leg which is bifurcated at its upper end and positioned equally beneath the cover of said unit and said neighbouring unit. The legs are preferably tubular, of square round cross-section and arranged to fit into flanged sockets or pegs secured to the floor, other sockets or pegs being secured to the underside of the cover at each corner for receiving the upper end of a simple columnar leg, if there is no neighbouring unit, or of one of the bifurcations of a bifurcated leg if there is a neighbouring unit.

Each cover is preferably formed with a peripheral upturned lip to minimise spillage; the juxtaposed lips of adjacent covers are capped by a capping of inverted U-section to prevent spillage or seepage of liquid between units. The peripheral lip is desirably also continued downwardly to retain the upper edge of a panel one of which is fitted to the front and rear of each unit and to the exposed end of a terminal unit; the bottom edges of the panels drop into grooved brackets secured to each leg near its base.

The or each tank preferably rests on downwardly-continued walls, the medial portions of which are cut away to allow the underlying floor to be washed free of harmful spilt chemicals: there is thus no obstruction apart from the corner portions of the tank walls, the bottom portions of the tubular legs and the co-operating flanged sockets or pegs.

If the tank is to hold a solution which gives off noxious fumes and vapours an extraction orifice is normally fitted through which fumes and vapours may be drawn off from across the surface of liquid in the tank. Because the orifice is connected to overhead ducting it is convenient to arrange the orifice at the rear upper edge of the tank. However this is usually shorter than the upper edges extending transversely of the plating line.

According to a yet further aspect of the present invention an extraction orifice is formed integrally with a wall of the tank extending transversely of the plating line and leads to ducting extending downwards and to the rear of the tank where said ducting is connected to a common discharge duct which may be formed of PVC running along the rear of the units.

The tank may be constructed with internal divider plates to permit counter flow rinsing; and with compartments to house, for example, heaters or temperature probes.

Instead of the tank liner in conventional use which is simply a sheet of polyethylene, the present invention provides according to a still further aspect a purpose-made rigid inner tank with a peripheral flange which interlocks with an upturned formation running along the bottom of the dependent lip located at the periphery of the aperture through the cover.

The entire construction, except for ducting, is normally fabricated of polypropylene to combine maximum strength and corrosion-resistance with reasonable cost and is far superior to the conventional PVC which ages and cracks; moreover polypropylene lends itself to being welded Where the unit is for use in an electroless plating process or in the non-plating tanks of an electro plating process it additionally comprises rollers mounted on the cover supporting a frame constituting a jig carrier which is arranged to be reciprocated in a longitudinal direction and from which are suspended jigs which carry the workpieces to facilitate their transfer from tank to tank and enable them to be moved with respect to the surrounding solution when in the tanks.A drawback of conventional frames is that they are formed of a quite rigid material which if it becomes distorted, will not be supported by all the rollers thus subjecting the remaining rollers to undue strain; moreover, if a roller which is in contact with the frame should stick very rapid wear of the frame and roller takes place, the latter rapidly losing its circularity. According to another aspect of the present invention the frame is made of a slightly flexible material such as polypropylene so that it always engages all the rollers which are preferably made of polyacetal so as to be corrosion-resistant and hard-wearina.

In known systems the reciprocal drive for the frames is arranged above the frames which of course restricts access to the tanks: according to the present invention the reciprocal drive is arranged from beneath the frame, the power source, e.g. an electric motor, being housed in a terminal unit with a drive shaft projecting through the cover; the simple mechanism for converting rotary to reciprocal motion is preferably protected by a housing.

According to still another aspect of the present invention there is provided a jig for suspension from the above-described reciprocating frame and for carrying a number of plate-form workpieces such as PCBs, the jig comprising a framework the bottom of which provides or mounts support means for supporting a plurality of workpieces, first and second reception means for receiving respective opposed upstanding edge portions of each workpiece, the first and second reception means preferably being independently adjustable to accommodate different heights of workpiece and preferably also being independently adjustable to accommodate different widths of workpiece.The support means and reception means may each be elongate members with a number of slots formed therein, the elongate slotted members constituting the first and second reception means being slidably mounted on elements which are upstanding with respect to the base, and which are themselves adjustable in a direction perpendicular to their longitudinal extension.

To enable workpieces of greatly different widths to be accommodated intermediate support arms may be provided, the arms being mounted to pivot in a plane normal to the direction of longitudinal extension of said elements.

The jig is normally provided with suspension means which cooperate with the reciprocable frame and which may take the form of two pairs of arms, one positioned above respective opposed ends of the framework. The pairs of arms are preferably formed so as to allow the jig to be placed in the bath in a correct orientation only and one arm may carry an actuator for a proximity switch which is closed when the jig is placed in the tank so that e.g. a timing control, warning light or rinse procedure may be automatically operated.

Where the unit comprises an electro plating tank it is necessary for the cathode to be reciprocated. Conventional cathodes normally take the form of a stainless steel bar positioned above the bath and supported at each end on a plastics roller; if a roller should stick considerable wear is suffered by the roller which soon develops a flat on its circumferential surface.According to a yet further aspect of the present invention the danger of such wear is minimized by securing to at least the undersurface of the bar at or near each end thereof a pad of hard, self-lubricating synthetic resin material such as polytetrafluoroethylene, a further pad preferably being secured to each side face of the bar adjacent to said pad, and utilizing as a support for each end of the bar a block of similar material having a channel in which is received for sliding movement the respective end portion of the bar to which the pad or pads are secured. If the block is of generally H-section and dimensioned to be accepted by a frame mounted on, for example, the cover, the block may be turned round or upside down to bring unworn or less worn surfaces into play.

According to a rather different aspect of the present invention there is provided apparatus for use in the electro plating of precious metals, comprising a framework formed of lengths of a weldable, corrosion-resistant plastics material such as polypropylene which supports a number of pre-treatment tanks, access to each of which is provided by an aperture in a common cover, and/or a plating tank. Preferably the apparatus comprises a unified pre-treatment section and a plating section which may be followed by at least one drag-out tank.

Access to space below the pre-treatment tanks which is not occupied by equipment and which may be used for storage is preferably gained through sliding doors and a catchment tray is located beneath the plating tank.

A control console may be provided at the rear of the worktop.

Although the invention may be carried out in a variety of ways, some particular embodiments thereof will now be described, by way of example, with reference to the accompanying drawings in which Figure 1 is a front elevation, partly broken away and partly in vertical section, of a terminal portion of a plating line according to the invention; Figure 2 is a plan of the terminal portion of a plating line shown in Fig. 1; Figure 3 is a vertical section on an enlarged scale through the plating line of Figs 1 and 2 at the right hand tank; Figure 4 is a side elevation of a modification of the tank shown in Fig. 3; Figure 5 is a plan of the tank shown in Fig. 4; Figure 6 is a vertical section of a countercurrent rinsing tank taken in the lorigitudinal direction of the plating line; Figure 7 is a plan of the tank of Fig. 6; ; Figure 8 is a transverse vertical section through a tank receiving a removable liner; Figure 9 is an isometric view of a jig for holding PCBs; Figure 10 is a plan of a terminal portion of a reciprocable cathode bar assembly according to the invention; Figure 11 is a vertical section on the line Xl- Xl of Fig. 10; and, Figure 12 is a vertical section on the line XII XII of 11.

In Figs 1 to 3 there is shown a terminal unit 10 of an electroless copper plating through hole (PTH) line for PCBs.

At its free end, being the right-hand end as seen in Figs. 1 and 2, the unit 10 has two columnar support legs 12, 14 which consist simply of a length of polypropylene tubing; at its other end which is juxtaposed with the end of a neighbouring unit 16, the unit 10 shares with the unit 1 6 two bifurcated intermediate support legs 1 8, 20. These each comprise a stem 22, a crosspiece 24 and two vertical branch pieces 26, all constituted by lengths of polypropylene tubing.

The bases of two columnar legs 12, 14 and the bifurcated legs 18, 20 are each firmly held in a flanged polypropylene socket 28 which is secured to the floor. In an alternative embodiment the legs 12, 14, 18 20 and sockets 28 may be provided with cooperating screw threads to provide height adjustment.

A rectangular cover 30 of sheet polypropylene has a socket 32 of the same material welded to its underside at each corner for receiving the respective upper ends of the legs 12, 14 and of the right hand branch pieces 26. The cover 30 has welded around its periphery a polypropylene strip 34 forming a raised lip 34a and a downwardlyprojecting lip 34b. An oblong aperture 36 and a square aperture 38 are cut out from the cover 30, each aperture having a dependent skirt 40.

A free-standing tank 42 of oblong crosssection is constructed from sheet polypropylene and comprises two end walls 44, 46 and two side walls 48, 50 having a peripheral lip 52 running around the upper edges thereof, and an inset floor 54; the medial portions of the walls 44, 46, 48, 50 are cut away. A shelf 56 projects from the end wall 44 and is apertured to support an immersion heater 58 which is protected by two protection rods 60, 62. A water inlet 64 is provided in the end wall 46 and a drain outlet 66 in the floor 54, the inlet 64 and outlet 66 both having valved connections (not shown). As best seen in Fig. 3 the dependent skirt 40 around the aperture 36 enters the mouth of the tank 42 while the lip 52 contacts the underside of the cover 30 to assist in supporting it.

A square tank 68 is constructed similarly to the tank 42 and cooperates in a similar way with the skirt 40 around the aperture 38. The tank 68 is fitted with an inlet and an outlet (not shown) and any other desired equipment.

Near the foot of each of the legs 12,14 are mounted two mutually perpendicular grooved brackets 70 while a single grooved bracket 72 is mounted near the foot of each of the intermediate support legs 1 6, 1 8 to project on either side thereof. A front panel 74, end panel 76 and rear panel 78, each consisting of a rectangular polypropylene sheet are mounted simply by inserting the upper edge behind the respective length of the downwardly-projecting lip 34b and then allowing the lower edge to drop into respective grooved brackets 70, 72. The upper edges of the panels 74, 76, 78 are prevented from falling inwardly by a flange 79 (see Fig. 3).

Trunking 80 to contain electric wiring (not shown) is mounted along the rear of the cover 30 and has an inclined front panel 82 on which are mounted push buttons, switching meters, and indicator lights indicated generally by the reference 84 thus providing a control console; electrical equipment (notshown) such as transformers are housed within the trunking 80, the rear of which is closed by removable panels 82.

The construction of the adjacent unit 1 6 is essentially similar to that of the unit 10. A cover 86 of the unit is apertured to provide access to a tank 88 and is supported at its corners by the right hand branch pieces 26 extending from the common legs 18, 20. The two juxtaposed lengths of the raised lip 34a are capped by a length of channel section polypropylene extrusion 90 to prevent seepage of liquid between the covers 30, 86.

A jig carrier 92 consists essentially of a frame 94 constructed of polypropylene and formed of two longitudinal members 96, 98 running the length of the plating line connected by an end frame member 100 and a series of transverse struts 102 connecting the longitudinal members 96, 98 between each tank. The frame 94 is mounted for reciprocation on polyacetal rollers 104 running on stainless steel pins mounted in polypropylene blocks 106 secured to the cover 30 beneath each of the longitudinal members 96, 98.

Reciprocating motion is imparted to the frame 94 through a link arm 104, one end of which is pivotally connected to the end frame member 100 and the other end of which is pivotally connected to a drive wheel 106 at a point near the circumference thereof, the wheel 106 being driven by an electric motor (not shown) mounted within the unit 10.

At intervals along the longitudinal member 96 there project crutches 108 each of which is matched by an identical crutch 108 projecting from the longitudinal member 98 at an opposed position. As best seen in Fig. 3 adjacent pairs of opposed crutches 108 support the respective ends of rails 110 from which a jig 112 to be described in detail later is supported.

Fig. 4 shows a modification 114 of the tank 42 in which an orifice 11 5 replaces the dependent skirt 40 at the top of the side tank wall 50. The orifice 11 5 gives into a hood 11 6 which narrows to a socket 118 in which is received an elbow duct 1 20 which is connected to a PVC trunking (not shown) running along the rear of the units 10, 1 6 at a level about half the height thereof. The tank 114 is equipped with a level probe 121 and a thermostat probe 122 and has an intermediate floor support 123.

In Figs. 6 and 7 is shown a counter flow rinsing tank 1 24 which is incorporated into an unillustrated part of the plating line. The tank 124 is internally partitioned by three divider plates 125, 126, 127, the plate 126 being apertured at 128. The tank 122 is thus divided into four compartments 130, 131, 132, 133, compartment 130 having a valved drain 134, and compartments 131, 132 being served by a common valved drain 135. Rinsing water is fed to the bottom of the compartment 1 30 through inlet pipe 136, flows over the weir formed by the top plate 125 and into compartment 134 via the apertures 128, over the weir formed by the top of plate 127, and thence to waste through the open drain 138.PCBs are initially rinsed in the comparatively dirty water in compartment 132 and subsequently in the cleaner water flowing through compartment 130.

A tank 140 shown in Fig. 8 is modified to receive a liner tank 142, the use of which enables any sludgy deposit formed therein to be easily disposed of. The skirt 40 around an aperture 144 in the cover 30 is formed with an upturned lip 146 and the upper edges of the walls 148 with a co-operating down tunnel lip 150. The liner tank 142 is provided with shelves 152,154 apertured for reception of a heater. By means of handles one of which 1 56 is shown the liner tank 142 may easily be withdrawn for cleaning out Fig. 9 shows the previously-mentioned jig 112 in greater detail.The jig 112 has a pair of base members 160, a pair of uprights 162, 164 at each end interconnected by intermediate struts 166, 1 68 and a pair of upper rails 110 which have extensions 11 Oa at one end and longer extensions 11 Ob at the other end. A locating block 1 70 is secured to the underside of the extensions 11 ova,11 Oh and to one of the blocks is secured an actuator 1 70 for a proximity switch (not shown) mounted on the inner side face of the longitudinal member 96 near the respective crutch 108. It will be appreciated that the base members 160, the two pairs of uprights 162, 164 and the pair of rails define a cuboid framework.

A series of slotted rack members 1 74 are secured transversely between the base members 160. Between each corresponding pair of uprights 1 62, 1 64 are secured lower rods 174 and upper rods 1 76. Four vertical rods 1 78 are slidably mounted between the lower rod 174 and upper rod 176 lying in the plane defined by a side face of the framework of the jig 112 and four corresponding rods 180 are similarly mounted on the other side face of the framework. As will be seen the vertical rods 1 78, 1 80 terminate at each end in bosses 182 which may be secured in a desired position on the respective rods 1 74, 1 76 which pass there through by a grub screw.A slotted rack element 1 84 extends between each opposed end pair of vertical rods 178, 180, the element terminating at each end in a collar 186 in which the respective rod 1 78, 1 80 is slidably received, the collars 1 86 being securable by means of a grub screw.

A half-length slotted rack element 188 terminates at one end in a collar 1 86 is mounted on each end of the two inner pairs of vertical rods 178, 180. The jig 110 is thus very adaptable for receiving PCBs or similar plate-like articles of different sizes; by adjustment of the rack elements 1 84, 1 88 in horizontal and vertical directions; if large plates are to be accommodated the half-length rack elements 1 88 may simply be rotated about the respective vertical rods 178, 180 so that they lie in the plane of the side of the framework thus allowing the whole length of the jig between the uprights i 62, 164 to be utilized.

In an alternative embodiment the rails 110 at the top of the jig carrier 112 may be positioned more closely together and the crutches 108 positioned correspondingly closer at one side to prevent the jig carrier from being placed in a tank the wrong way round.

In Figs. 10 and 11 is shown one end of a stainless steel cathode carrier frame 190 which comprises two carrier arms 1 92, 1 94 joined at the ends shown by an L-section polypropylene cathode carrier 1 96 having a horizontal stainless steel stiffening plate 198 on'which is pivotally mounted one end of a link arm 200, the other end of which is pivoted eccentrically to a driven wheel 202. The link arm 200 and wheel 202 are protected by a cover 203.

Near its end the arm 192 is fitted a PTFE channel 204 which is secured by screws, one of which 206 is shown. A terminal lug 208 projects from the end of each arm 192, 194 for connection of copper braid 210 running from a source of supply along the side of each arm.

Beneath each channel is mounted a PTFE bearing block 212 (shown in section in Fig. 12) which is a sliding fit in a square frame 214. The weight of each carrier arm 1 90, 192 is thus taken by the undersurface of the respective PTFE channel 204 which rests on one of the four bearing surfaces 216 provided by the block212 thus giving an extremely long-lasting bearing.

When appreciable wear does take place the block 212 may be withdrawn and be replaced after being turned through 980 to bring another bearing surface 216 uppermost.

It has not be attempted above to describe all the equipment which may be incorporated into the plating line construction of the present invention: what must be stressed is that the construction allows the equipment to be incorporated easily and in a rational manner. For example the electrical equipment and supply lines are as far as possible installed in the trunking 80 which is above water level; water supply lines are positioned along the top rear of the units; extraction ducting is at mid-level; and drainage connections along the rear of the units near floor level. The design of the tanks and legs not only allows efficient hosing down but also provides access to the outlets.

Rearrangement of tanks may be carried out with the minimum of expense and trouble to allow different procedures to be adopted.

Claims (36)

Claims

1. A plating line unit for assembly with one or more other similar units to form an electro or electroless plating line, the unit comprising at least one free-standing tank, a cover having an aperture to provide access to the top of the tank, four legs each supporting a corner of the cover, and trunking for housing electrical equipment and supply lines positioned over the rear of the cover.

2. A unit as claimed in claim 1, in which the cover has a dependent lip projecting into the mouth of the tank and is partially supported by the tank.

3. A unit as claimed in claim 1 or 2, in which the cover is formed with a peripheral upturned lip.

4. A unit as claimed in claim 3, in which the peripheral lip is continued downwardly to retain the upper edge of an upstanding panel.

5. A unit as claimed in any preceding claim, in which the cover has sockets or pegs secured to the underside of the cover at each corner thereof for receiving an upper end of a respective leg.

6. A unit as claimed in any preceding claim and additionally comprising a bracket secured to the lower portion of each leg for supporting the lower corner of an upstanding panel.

7. A unit as claimed in any preceding claim, in which the tank is arranged to rest on downwardly-continued wells, the medial portions of which are cut away to allow the underlying floor to be washed free of harmful spilt chemicals.

8. A unit as claimed in any preceding claim, in which the tank additionally comprises an extraction orifice formed integrally with a wall of the tank extending transversely of the plating line.

9. A unit as claimed in any preceding claim and additionally comprising a rigid inner tank with a peripheral flange which interlocks with an upturned formation running along the bottom of a dependent lip located at the periphery of the aperture through the cover.

10. A unit as claimed in any preceding claim and additionally comprising rollers mounted on the cover and supporting a frame constituting a jig carrier which is arranged to be reciprocated in a longitudinal direction and from which, in use, are suspended jigs which carry the workpieces.

11. A unit as claimed in claim 10 and comprising a reciprocal drive arranged from beneath the frame.

12. A unit as claimed in any preceding claim and constructed substantially of polypropylene.

13. A unit as claimed in any preceding claim which is to be juxtaposed with a neighbouring unit, and in which each leg intended for juxtaposition with a neighbouring unit is provided with means to support a respective adjacent corner of the cover of the neighbouring unit.

14. A unit as claimed in claim 13, in which each said leg is bifurcated at its upper end to allow it to be positioned equally beneath the cover of said unit and said neighbouring unit.

1 5. A unit as claimed in claim 1 and substarftially as herein described.

1 6. A plating line unit substantially as herein described with reference to the accompanying drawings.

17. Ajig for suspension from a reciprocating frame and for carrying a number of plate-form workpieces for immersion into a tank on a plating line, the jig comprising a framework the bottom of which provides or mounts support means for supporting a plurality of workpieces, and first and second reception means for receiving respective opposed upstanding edge portions of each workpi ece.

1 8. A jig as claimed in claim 17, in which the first and second reception means are arranged to be independently adjustable to accommodate different heights of workpiece.

19. A jig as claimed in claim 17 or 18, in which the first and second reception means are independently adjustable to accommodate different widths of workpiece.

20. A jig as claimed in any one of claims 17 to 19, in which the support means and reception means are each elongate members with a number of slots formed therein, the elongate slotted members constituting the first and second reception means being slidably mounted on elements which are upstanding with respect to the base, and which are themselves adjustable in a direction perpendicular to their longitudinal extension.

21. A jig as claimed in any one of claims 17 to 20 and additionally comprising intermediate support arms mounted so as to be pivotable in a plane normal to the direction of longitudinal extension of said elements to enable workpieces of greatly different widths to be accommodated.

22. A jig as claimed in any one of claims 17 to 21 and additionally comprising suspension means which cooperate with the reciprocable frame.

23. A jig as claimed in claim 22, in which the suspension means take the form of two pairs of arms.

24. Ajig as claimed in claim 23 in which the pairs of arms are formed so as to allow the jig to be placed in the bath in a correct orientation only.

25. Ajig as claimed in claim 23 or 24, in which one arm carrying an actuator for a proximity switch which is arranged to be closed when the jig is placed in the tank.

26. A jig as claimed in claim 17 and substantially as herein described.

27. Ajig substantially as herein described with reference to Fig. 9 of the accompanying drawings.

28. A reciprocating cathode for an electro plating tank comprising a bar having secured at least to the undersurface thereof, at or near each end, a pad of hard, self-lubricating synthetic resin material such as polytetrafluoroethylene.

29. A cathode as claimed in claim 28, in which a further pad is secured to each side face of the bar adjacent to said pad, and additionally comprising, as a support for each end of the bar, blocks of similar material having a channel in which is received for sliding movement the respective end portion of the bar to which the pad or pads are secured.

30. A cathode as claimed in claim 28, in which each block is of generally H-section and dimensioned to be accepted by a mounting frame, the arrangement being such that the block may be turned round or upside down to bring unworn or less worn surfaces into play.

31. A cathode as claimed in claim 27 and substantially as herein described.

32. A reciprocating cathode substantially as herein described with reference to Figs. 10 to 12 of the accompanying drawings.

33. Apparatus for use in the electro plating of precious metals, comprising a framework formed of lengths of a weldable, corrosion-resistant plastics material such as polypropylene which supports a number of pre-treatment tanks, access to each of which is provided by an aperture in a common cover, and/or a plating tank.

34. Apparatus as claimed in claim 32 and which comprises a unified pre-treatment section and a plating section.

35. Apparatus as claimed in claim 33 and additionally comprising at least one drag-out tank.

36. The features as herein disclosed, or their equivalents, in any novel selection.