The invention also relates to a machine for treating objects in the form of sheets or plates, comprising at least one treatment station in which the objects are treated, and a conveyor for transporting the objects through the machine, said conveyor having a plurality of carriers for carrying the objects, each of said carrier including at least one holding member for holding an object at an edge portion thereof, the object being freely suspended in the holding member.

The device according to the invention is primarily intended, and particularly suited for use in a machine for treating the kind of objects in the form of plane sheets or plane plates which form the starting material for the production of printed circuit cards and it therefore will be described with this use as an illustrative example. However, it is not limited to this use.

A machine for surface treatment of sheets or thin plates of the type mentioned above, in the following termed panels, is known from SE-B-459 084. It comprises a transporting system with carriers for the panels. Each carrier holds a panel which is suspended in a holding

member on the panel-carrier, the holding member being provided with a plurality of gripping devices. During the treatment the panel carriers, each having a panel, are moved stepwise along a transporting path from a loading station for the panels to a discharge station. As the carriers proceed from the loading station to the discharge station, the panel carriers pass a number of treating baths into which the panels are dipped.

The movement of the carriers with the panels suspended from their gripping devices includes horizontal movements, which normally take place while the carriers are in an upper position in which the panels are raised from the treating baths, and vertical movements between the upper position and a lower position in which the panels are dipped into the treating baths and raised therefrom.

In the application of the invention taken as an example the panels may be a laminate of a non-conducting layer an a copper foil applied thereto. A circuit pattern is made on the panel by etching after a so-called resist, i.e. a coating corresponding to the desired circuit pattern and resistant to the etching liquid, has been applied onto the copper foil. After the etching the resist is removed, so-called stripping in order to expose the circuit pattern.

The resist can be applied to the panel using different methods. In a known method a film of photosensitive resist material is rolled onto the surface of the copper foil whereupon the circuit pattern is exposed on the film which is then developed. The portions corresponding to the interspaces between the conducting portions of the circuit pattern are removed so that a resist pattern remains which is in accordance with the desired circuit pattern.

Using a more recently developed method it is possible to reduce substantially the width of the conductors and the spaces between the conducting portions of the circuit patterns in relation to the first-mentioned method.

According to this method, the resist film is applied by electrophoresis. The copper foil laminate or panel then functions as an electrode in an electrically conducting bath containing the photosensitive resist material in dissolved form. The non-conducting resist material migrates to the foil surface and attaches to it. When the foil surface and, where applicable, copper plated walls of holes in the panel, have been completely coated with a dense film of resist material, the electrophoretic coating process ceases. After a careful removal of remaining bath liquid by bowing and drying of the panels the film formed is exposed and developed in the same manner as the first-mentioned method.

In the electrophoretic coating method, the gripping devices not only have to hold the panel but also have to maintain good electrically conducting contact with the copper foil.

One and the same gripping device should be able to be used, as far as possible, for different kinds of panels, such as thin panels, thick and heavy panels (such as multilayer panels, which are panels having several insulating layers and conducting layers positioned therebetween) , panels which are easy to bend, rigid panels, panels which are to be treated by the electrophoretic resist coating method, panels which are to be subjected to other methods which do not require current supply to the panel, and so on.

It is also desirable for the gripping devices to meet the following further requirements:

The gripping devices should hold the panel rigidly such that the panel can be agitated and vibrated without being displaced in the holding member so that good exchange of chemicals in through-plated apertures in the panel is ensured.

The gripping devices should hold the panel by gripping elements which only in little extent penetrate the surface layer of the panel; therefore the gripping elements should not be in the form of points or needles.

The gripping devices should cover as little portion of the panel as possible; in general the portion which the gripping devices cover have to be cut away and disposed resulting in loss of expensive material.

Bath liquid should be efficiently blown away from the surfaces of the gripping devices.

The gripping devices should transfer as little bath liquid as possible from one treating bath to the next.

The gripping devices should keep the panel in vertical position no matter if the panel is thick or thin.

In the case the gripping devices also serve as electrical contact means, their contact surfaces for transferring current to the panel should be as small as possible so that undesired plating with resist material and the resulting necessity of cleaning demand and loss of valuable resist material are minimized. Resist material deposited on the contact

surfaces should be able to be removed chemically without opening the gripping devices, and the contact surfaces should have a long useful life.

The object of the invention is to provide a device and a machine of the types indicated above, the gripping devices of which well meeting at least most of the requirements indicated above.

The device according to the invention is characterized in that the holding member includes at least one clamp having two cooperating shanks which are movable toward and away from each other, each shank having a clamping element, said clamping elements defining a gap therebetween which can be opened for receiving said edge portion of the object, and that at least one of the clamping elements has at least one edge-like ridge, the crest of which facing the other clamping element.

The machine according to the invention is characterized in that the holding member includes at least one clamp having two cooperating shanks which are movable toward and away from each other, each shank having a clamping element, said clamping elements defining a gap therebetween which can be opened for receiving said edge portion of the object, and that each clamping element consists of a rod with a plurality of substantially parallel edge-like ridges, the ridges of the one clamping element being substantially horizontal and the ridges of the other clamping element being substantially vertical.

The invention is described further below with reference to the accompanying drawings showing a preferred embodiment.

Fig. 1 is a perspective view of a machine according to the invention;

Fig. 2 is a schematic view of a panel carrier of the machine according to Fig. 1 with holding members for four panels; Fig. 3 is a side view of a clamp of the holding member according to Fig. 2; Figs. 4-6 show the clamping elements of the clamp in different positions.

The machine 10 schematically shown in Fig. 1 for dip-treatment of objects P is of the kind known per se and shown and described in SE-B-459 084. Reference is made to this publication for a full description of the machine and its mode of operation; the machine is described herein only to the extent required for an understanding of the present invention.

At one end, to the left in Fig. 1, the machine comprises an loading station 11, not shown in detail, having a store for a supply of objects P in the form of plane panels to be treated.

At the other, right end, the machine has a discharge station 12, likewise not shown in detail, with a store in which treated panels are placed.

Disposed between the loading and discharge stations 11, 12 are a treatment station which includes a row of tanks for treatment baths, such as baths for electrophoretic coating of the panels with resist material and pre-treatment and post-treatment of the coated panels, and equipment 14 for drying the treated panels. Behind the row of tanks there is a conveyor 15 which serves for transporting the panels stepwise from the loading station 11 to the discharge station 12 and to

dip the panels in one-or more of the treatment baths in the tanks in the treatment station 13 during the transport.

The panels are transported by means of a number of carriers 16 having a bracket or cantilever beam 17 provided with four holding members 18. The holding members hold the panels P at their upper edge portion and move along a horizontal path as they move from the loading station 11 to the discharge station 12.

Furthermore, they move up and down at the baths in which the panels are to be treated and also at the loading station 11 and the discharge station 12.

At the loading station 11 each holding member 18 is brought into engagement with the upper edge portion of a panel in the store and the panels are then held suspended in the holding members until the carrier 16 reaches the discharge station 12 where the holding members are opened and the finally treated panels are delivered to the store.

From the discharge station 12 the carriers 16 are returned to the loading station 11 on an upper transporting path 19.

Fig. 2 shows one of the carriers 16 with the four holding members 18, which hold and support four suspended panels P disposed in vertical planes which are parallel to the direction in which the panels are transported.

During its movement the carrier 16 is slidably movably supported on a series of vertical support plates 20 disposed after each other (two support plates are shown in Fig. 2). The support plates 20 are individually movable in the vertical direction between an upper position and a lower position. When two adjacent support

plates 20 are in the-upper position or the lower position the carrier can be displaced horizontally from one support plate to the other by means of a feeding device 21 shown only roughly, see Fig. 2.

So far as it has been described above, the conveyor 15 is known. The invention relates to a special design of the conveyor and, more particularly, the holding members 18 of the carriers 16. This design will be described in greater detail below with reference to Figs. 2 to 5.

The four holding members 18 are disposed on a horizontal frame 22 which is suspended in the support beam 17 by strip-like electrically insulating connecting pieces (not shown) in a manner such that the frame 22, and thus also the holding members 18, can be vibrated or oscillated to and fro by means of an agitating device, not shown. The agitation, which is carried out while the panels P are immersed in a bath, serves to providing a relative movement of the panels and the bath liquid so that the bath liquid will be brought into intimate contact with all free surfaces of the panels.

The four holding members 18 are identical with each other and each includes a horizontal bar 23 which extends in the transporting direction and is disposed to the frame 22, and four gripping devices in the form of clamps 24 which are secured to the bar 23 and is similar to tongs.

Fig. 3 is a side view of a clamp 24.

Each clamp 24 has a pair of shanks 25 and 26 which are pivotally connected to each other by means of a pin bolt 27 the axis of which is parallel to the bar 23. The upper end of the one shank 25 is secured to the bar 23 and carries the pin bolt 27 and the other shank 26 via the pin bolt. Above the pin bolt 27 a compression spring 28 is inserted between the shanks 25, 26. The spring 28

constantly endeavours to moving the upper shank parts 25A and 26A away from each other.

The stationary shank 25 of the clamp 24 is formed of a vertical rod the lower end of which is provided with a likewise vertical downwardly extending clamping element 29. This is in the shape of a threaded rod, the upper end of which is screwed into a threaded hole 25B in the upper shank part 25A. The clamping element 29, which forms a lower shank part, can be adjusted in vertical direction and in turning direction by turning it in relation to the upper shank part. It can be locked in a selected set position by means of a locking nut 30.

Similarly, the shank 26 has an upper shank part 26A in the shape of a rod and a lower shank part formed of a threaded rod 31 extending downwardly from the lower end of the rod 26A. The upper end of the rod 31 is screwed into a threaded hole 26B in the upper shank part 26A and can be adjusted vertically in the same manner as the clamping element 29 and locked in a selected set position by means of a locking nut 32. A clamping element 33 in form of a short piece of a threaded rod is secured to the rod 31 adjacent the lower end thereof by welding or soldering or in some other suitable manner. The clamping element 33 is secured to the rod 31 such that it is opposite to the clamping element 29 with the axis substantially horizontal.

The compression spring 28 constantly endeavours to holding the clamp 24 in a closed position with the clamping elements 29 and 33 placed close to each other.

An opening mechanism, not shown, at the loading station 11 of the machine is arranged to move the upper shank parts 25A, 26A together to open the clamp 24 so that the upper edge of a panel P in the loading store can be inserted between the lower shank parts (Figs. 5, 6). When

the opening mechanism then releases the upper shank parts, the clamp is closed by the spring 28, whereby the threads of the clamping elements 29 and 33 engage the panel P on opposite sides thereof (Figs. 3, 4). A corresponding opening mechanism is provided at the discharge station 12.

The clamp 24 is made wholly of metal so that it can serve as connecting device for supplying current to the panel P. Alternatively, only the clamping elements 29 and 33 and the rod 31 are made of or coated with metal and arranged so that they can be connected to a current source. The clamping elements 29 and 33 then serve not only as holding means, but also as electrical connecting members which connect the panel P to the current source, said panel P being immersed in a treatment bath and serving as an electrode (anode) in an electrophoretic resist coating system, for instance.

The threads of the clamping elements 29 and 33 are V-threads, such as metric threads (in most cases M8-M12 threads are suitable) and the crest of threads 29A and 33A thus are substantially triangular in cross-section.

The sections of the crest of threads 29A, 33A of the clamping elements 29, 33 which engage the opposite sides of the panel P therefore form edge-like ridges, the ridges of the clamping element 29 being parallel with each other and inclining to the vertical plane by a small angle corresponding to the helix angle of the thread, while the ridges of the clamping element 33, which likewise are parallel with each other, incline by a small angle to a vertical plane which is parallel to the transporting direction, i.e. perpendicularly to the panel faces.

The contact surfaces of the clamping elements 29, 33 which are formed by the crests of the ridges are

therefore small, but--not so small as to easily penetrate a metal foil on the panel faces. Moreover, they have the form of two orthogonal or mainly orthogonal systems of parallel short lines facing each other on opposite sides of the panel P. The contact surfaces therefore provide both a good electrical contact between, on the one hand, the clamping elements 29, 33 and, on the other hand, the panel, and a very firm grip of the panel so that it is reliably held against the forces acting on the panel at the contact surfaces of the clamping elements without there being a great danger of damaging the panel, regardless of the direction of the forces.

The threads of the clamping elements 29, 33 may be standardised V-threads, the thread diameter and other quantities being chosen such that the surface pressure at the contact surfaces is sufficient to ensure a good contact and a safe holding but yet not so high as to cause damages to the panels at the contact areas.

Suitably, a plurality of thread turns, such as two or three thread turns, engage the panel on each side. When required, the thread tops can be sharpened at the contact areas by filing or grinding or in any other suitable manner so that a firm grip is ensured.

In the embodiment of the clamping elements 29, 33 shown and described by way of example the choice of threads, which are the elements by which the clamping elements engage the panels, is dictated by practical conditions in the production, standard elements in the form of screws or threaded rods can be used. Obvious alternatives, which are equivalent in respect of the intended function, are other ridge-like shapes, such as annular ridges having a triangular cross-section.

The shapes of the clamping elements represented by the embodiments shown and described by way of example are

also favourable in that they permit an effective blowing away of bath liquid which accompanies the clamping elements when the panels are lifted out of the baths.

Normally, the panels have to be entirely immersed in the baths during the treatment. This means that also a portion of the clamping elements will be immersed in the bath liquid. Bath liquid will therefore inevitably be left on the clamping elements when they are lifted up, but this liquid can easily be blown away at the same time as liquid accompanying the panels is blown away when the panels have been lifted. The bath liquid tends to remaining in particular at the narrow spaces at the contact areas of the clamping elements, but the chosen shape of the clamping elements contributes to an effective blowing away also there.

In cases where the treatment of the panels includes the application of a resist film by electrophoretic technique in the manner explained above, the resist material tends to coat also those surfaces of the clamping elements which are immersed in the resist bath. After the treatment, resist material must therefore be removed from these surfaces. This may be effected in a chemical way.

The illustrated and described design of the clamping elements 29 and 33 with cross-wise systems of ridges is advantageous also in respect of the removal of the resist coating from the clamping elements. When the clamping elements are opened to release the panel at the discharge station and allowed to close, the clamping elements 29, 33 will engage each other directly. However, they will be in direct contact with each other only where the ridges cross each other. Consequently, the liquid used to remove the resist coating on the clamping elements will readily come into contact with the coating even at those parts of the clamping elements which engage the panels during the treatment.

In order to minimize the undesired coating of the clamping elements with resist material, the clamping elements may be coated with a thin layer of a resist-repellent material, such as Teflon. This material can easily be removed, such as by means of a file or another abrasive means, from those surfaces of the clamping elements which are to serve as contact surfaces.

When required in the illustrated and described embodiment, fresh contact surfaces on the clamping element 29 can be successively provided by turning the clamping element through a part of turn and then being liberated from the coating at the portion which in this way has been positioned opposite to the other clamping element.

Coating the clamping elements with a resist-repellent material also facilitates the flowing-off of treatment liquid from the clamping elements. The flowing-off is also promoted by the ridges of the clamping elements everywhere having an inclination to the horizontal which in most places is considerable.

Figure 4 shows the clamp 24 when used to hold a panel P which is considerably thicker than the one shown in Fig. 3. From a comparison between Fig. 3 and Fig. 4 it is apparent that the difference in thickness will not entail any difference in the engagement of the clamping elements with the panel.