GB2136140A - Automatic Testing Machine for Printed Circuits - Google Patents

Abstract

An automatic testing machine for printed circuits, of the kind employing a checkout unit (5) electrically connected to a processor suitable to check the good or bad quality of printed circuits (6), comprises a horizontally movable feed conveyor (30) which transfers the printed circuits (6) coming from a stack (21) acting as a store, to the checkout unit (5) where a vertically movable, transverse locating member (40) is provided, which is suitable to contact and position the printed circuit (6) on the checkout unit (5) in the best way, after the automatic locking of the feed conveyor (30). An automatic separation device (49) for faulty printed circuits, controlled by the processor, is provided downstream of the checkout unit (5) with respect to the feed-in direction of conveyor (30). The machine structural components relating to the stacking (3), transporting (2) and separating (4) @ for said printed circuits (6) are adjustable in position according to the sizes of the printed circuits (6) to be examined. <IMAGE>

Description

SPECIFICATION Automatic Testing Machine for Printed Circuits It is known that printed circuits are checked in testing machines provided with adapted checkout units electrically connected to a processor which is suitable to instantaneously examine the good or bad quality of each printed circuit submitted to checkout. More particularly, checkout units essentially consist of a plurality of metal plugs or nails, disposed so as to form a sort of horizontal bed, usually called "bed of nails" on which they are disposed in a reticulated manner and are suitable to be inserted into corresponding checkout points provided with holes exhibited on the board of a printed circuit. The insertion of metal nails into the checkout points of a printed circuit occurs by the displacement of the horizontal lying plane of said bed in a direction normal to the printed circuit board.

At present, according to the art hitherto known, the positioning of each printed circuit on the checkout unit of the machine is carried out by hand by an operator who picks up the printed circuits from a store, transfers them to the machine and, after the checkout, separates the faulty circuits according to the processor indications.

It is apparent that this procedure is disadvantageous owing, on the one hand, to the required working times and, on the other hand, to the high costs due to the constant need of staff engaged with the checking operations.

Furthermore, owing to the direct human intervention, errors cannot be excluded both during the separation step of the examined printed circuits and the positioning step of each printed circuit on the checkout unit.

In order to obviate these drawbacks, automatic testing machines have been provided in which printed circuits are fed in by means of a chute along which the printed circuits coming from a store reach, by gravity, the checkout unit. These machines, which have a rather complicated structure, are exclusively designed for the checkout of printed circuits produced on a large scale (to be used on wide consumption articles such as for example television sets, household electrical apparatuses, etc.) having therefore the same (reduced) sizes and a rather small number of checkout points.

The main drawback of these machines is therefore due to their rigidity of employment as they are exclusively designed to check printed circuits of one type only and, in any case, of small sizes.

The main object of the present invention is therefore to overcome the above mentioned drawbacks relating to the art hitherto known, by the provision of a machine allowing to automatically carry out the feeding, checkout and separation of differently sized and even rather large circuits, while ensuring a great liability and high working speeds, thereby involving economical and technological advantages.

This and still further objects are achieved by the automatic testing machine for printed circuits of the kind using a checkout unit provided with a plurality of plugs or nails electrically connected to a process or, suitable to be connected to homologous checkout points provided with holes disposed on a printed circuit to be examined, said checkout unit being movable at right angles to the lying plane of said printed circuit thus allowing the insertion of part of said nails into said checkout points, characterized in that it comprises: a feed conveyor horizontally movable in the direction of said checkout unit; a loading device for the printed circuits to be examined, located upstream of said checkout unit relative to said feed-in direction, suitable to pick up the same, one by one, from a stack acting as a store, and to put them down upon said feed conveyor; a locating member transverse to said feed-in direction, disposed close to said checkout unit suitable to allow the contacting and positioning of each printed circuit in transit on said checkout unit, in register with said nails, said locating member being movable at right angles, according to predetermined working steps, with respect to the feed-in direction of said feed conveyor, means being provided for locking said feed conveyor during the checking step of each printed circuit in said checkout unit, an automatic selection and separation device for said printed circuits, disposed downstream of said checkout unit electrically connected to said processor and controlled thereby.

Advantageously, according to a further feature of the present invention, the feed conveyor consists of a pair of horizontal parallel powered belts on which two opposed side ends of each printed circuit respectively rest, the distance between said parallel belts being adjustable according to the sizes of the printed circuits to be examined and said belts being mounted on corresponding pulleys axially adjustable on their shafts of rotation.

Further features and advantages of the invention will be made more apparent in the following detailed description of the preferred embodiment given hereinafter by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a top diagrammatic view of the machine with some parts cut away to better show others; Fig. 2 is a top view of the levers for the control of the movable projections suitable to load the printed circuits to be examined on the feed conveyor; Fig. 3 shows a cross-sectional view of part of the machine taken along the line Ill-Ill in Fig. 1; Fig. 4 is a cross-sectional view of part of the machine taken along the line IV--IV in Fig. 2.

Referring to the accompanying drawings, it has been generally indicated at 1 the machine of the present invention. From a general point of view and said machine 1 substantially consists of a central portion 2 comprising a checkout unit 5, of a feed portion 3 for the feeding of the printed circuits 6 to be examined and of an end portion 4 for separating and evacuating the examined printed circuits 6.

The central portion 2 substantially consists of a testing machine for printed circuits of the traditional type comprising (see Figs. 1 and 4) a quadrangular structure 7 carrying four threaded bars 8 driven, through a chain 9 and gear wheels 10, by a motor 11, on which is mounted a horizontal plate 1 2 movable in a vertical direction, that is provided with a rising or descending motion depending upon the direction of rotation of the threaded bars 8.

A bed of metal nails 13 (Fig. 4) is secured on the horizontal plate 12 said nails being disposed in a known reticulated manner and being electrically connected to an electronic processor not shown in the figures. Above said bed 1 3 there is an exclusion mask 14 supported by brackets 1 5 integral to structure 7, which is provided with through holes 1 6 in register with bed 13, distributed according to the particular configuration of the printed circuits 6 to be examined.

At its upper part, the central portion 2 is provided with a flat horizontal lid 17, slightly spaced away from the exclusion mask 1 4 placed below so that it forms a slot having a thickness (D) slightly bigger than the thickness (S) of a printed circuit 6. Lid 1 7 is movable along the horizontal plane in known manner, so that it allows overhauling or manual intervention in the area placed below, being controlled, through a wheel 18, by a motor 19 (Fig. 1).

The feed portion 3 of the machine 1 is supported by a pair of longitudinal members 20 secured outwardly at one end of structure 7. It should be observed that this is very advantageous in itself as it allows to modify, according to the invention, machines of the known type without acting in a substantial manner on the main components thereof.

Referring particularly to Figs. nd 3, it has been indicated at 21 a stack of printed circuits 6 acting as a store, defined along its edges by four upright posts 22 of L-shaped section resting at their lower ends on the horizontal edges 23 of a pair of longitudinal structural members 24 parallel to each other, supported by transverse bars 25 fastened at their ends to the longitudinal members 20.

Two of said upright posts 22 are adjustable in place with respect to members 24, each of them being provided at its lower portion with a sliding block 22 slidably introduced into longitudinal guides 23' obtained on the edges 23 of members 24. Said members 24 are in turn adjustable in a transverse position (so that the distance therebetween can be altered), as they are connected to bars 25 by sleeves 26 that can be locked by means of securing screws not shown in the figures. As a result, it is possible to adapt the above described structure to any sizes (within certain limits) of the printed circuits 6 to be examined.

A shaft 27 driven by motor 28 is transversely mounted at the ends of the longitudinal members 20, on said shaft being fitted two pairs of pulleys 29 (which are also adjustable in place transversely to shaft 27) on which is mounted a pair of parallel belts 30 forming the feed conveyor for said printed circuits 6; said belts, driven by motor 28, move along the horizontal plane in the direction of the checkout unit 5 (as shown by the arrows in Fig. 1). At the opposite side with respect to the checkout unit 5, belts 30 are mounted on corresponding idler pulleys 29' which, as shown in Fig. 1, are secured in a removable manner to structure 7 so that they can be spaced apart from or approached to each other according to the sizes of the printed circuits 6.

In order to better explain what shown in the figure, it should be observed that pulleys 29 and 29' are disposed respectively by pairs, a further driving gear placed below (indicated at 29" in Fig.

3) being provided for each belt 30 for the purpose of maintaining belt 30 in the horizontal plane both for what concerns the active part thereof (moving forward towards the checkout unit 5) and the inactive part thereof (moving backward).

Belts 30 are disposed below the stack 21 so that they are brought into contact with the side edges of the printed circuits 6 which are positioned thereon in turn, by means of the loading device shown in Figs. 2 and 3. Said loading device 31 consists of a double series of projections 32 and 33 disposed on the structural members 24 and inwardly facing the area included therebetween. In more detail, the supporting projections 32 are disposed longitudinally aligned on each member 24 while the shaped projections 33, longitudinally aligned too, are disposed at a slightly higher level and offset with respect to the first ones.Projections 32 and 33 consists of substantially cylindrical members accommodated in through housings 34 obtained in said structural members 24 provided with a reciprocating motion in a transverse direction to the feed-in direction of belts 30 and protruding at the inside of the structural members 24. At the outside of each o,f them projections 32 and 33 are articulated respectively to control - levers 35 and 35' (Fig. 2) operated by two horizontal rods 36 and 36' driven by corresponding pneumatic jacks 37 and 37'.

Below said stack 21, at the same level as the supporting projections 32 there is a first micro switch 38 (Fig. 3) activated by each printed circuit 6, electrically connected to the pneumatic jacks 37 and 37' and adapted to control the following working steps of the loading device 31.

During a first step, stack 21 is supported by projections 32 (protruding from members 24) while projections 33 are inside housings 34.

Subsequently projections 33 (provided with a horizontally-grooved head 33', the thickness of said grooves 39 being equal to the thickness (S) of each printed circuit 6) protrude from housings 34 and act on the stack 21, exerting a pressure in a perpendicular direction thereto and contacting the side edges of the printed circuits 6 starting from the last but one, from the bottom. At this point projections 32 go back dropping a printed circuit (the last forming the bottom of stack 21) onto belts 30 while stack 21 is supported by projections 33. Then projections 32 protrude and projections 33 go back so that the stack 21 is caused to lower on projections 32. The cycle goes on. The micro-switch 38, contacted by the printed circuit 6-at the bottom of stack 21 causes the starting of the above described steps.If there are no more printed circuits 6 in stack 21, the microswitch 38 remains desactivated, which causes the loading device 31 to stop.

Then the printed circuit 6 carried on belts 30 reaches the checkout unit 5 where a transverse locating member 40 is provided adapted to allow the contacting and positioning of the same printed circuit 6 in correspondence of bed 13.

This locating member 40 consists of a horizontal plate (Figs. 1 and 3) disposed between belts 30 immediately downstream of bed 1 3 relative to the feed-in direction of said belts. It is provided with a horizontal abutment edge 41 at right angles to the feed-in direction of circuit 6, the angular position of which is adjustable in the horizontal plane by means of adjusting screws 42. A second micro-switch 43 is provided on said edge 41; when contacted by the printed circuit 6 it causes the belts 30 to stop as it is electrically connected to motor 28.

The locating member 40 is vertically movable as it is actuated by an electromagnet 48 (diagrammatically shown in Fig. 3) housed below it and acting on a pair of vertical cylinders 44 carrying the member 40 introduced into corresponding holes exhibited by structure 7. The vertical motions of said locating member 40 are scheduled. It appears projecting above the exclusion mask 14 so that it can contact the printed circuit 6 carried by belts 30 running over the exclusion mask 14 (see Fig. 4). As soon as the printed circuit 6 activates the microswitch 43, belts 30 stop and plate 12 rises introducing the nails of bed 13 into the holes 16 of mask 14 and, therethrough, into the checkout points of the printed circuit 6.After the checkout, plate 1 2 lowers, the locating member 40 is brought down actuated by the electromagnet 48, and belts 30 start again moving away the printed circuit 6 downstream of the checkout unit 5. The cycle goes on again.

Referring particularly to Figs. 3 and 4, it has been indicated at 45 an additional pair of belts disposed above belts 30 and parallel thereto.

Belts 45, mounted on corresponding powered pulleys 46 (in the same way as belts 30 so that they lie in the horizontal plane) are disposed immediately downstream of the loading device 31 over the whole longitudinal extension of belts 30 placed below.

Belts 45 aim at obviating possible warpage of the printed circuit 6 coming from stack 21 (which may occur in the event of rather large printed circuits), keeping said printed circuit 6 in a horizontal plane defined between the two pairs of belts 30 and 45.

As it is particularly shown in Fig. 4, belts 30 and 45 run within a slot of (D) thickness defined by mask 14 and lid 1 7 under which a covering sheet 47 in contact with belts 30 and 45 can be disposed.

Downstream of the checkout unit 5 there is the end portion 4 of the machine 1 where an automatic device 49 is provided for separating printed circuits 6. Said end portion 4 comprises a pair of longitudinal structural members 50 (Fig. 1) similar to members 24, provided with sleeves 51 mounted on transverse bars 52 supported at the ends of a pair of supporting longitudinal members 53 secured to structure 7.

This construction method too is advantageous as it allows to modify machines of the known type without carrying out particular changings on the main components thereof.

A shaft 54 driven by a motor 55 is transversely mounted at the ends of longitudinal members 53; it carries two pulleys 56 on which are respectively mounted two belts 57 forming the evacuation conveyor for said printed circuit 6. At their opposite ends belts 57 (movable according to the direction shown by the arrows in Fig. 1) are mounted on idler pulleys 58 connected to the ends of members 50. The distance between belts 57, in the same way as previously described, is adjustable depending upon the sizes of the printed circuit 6, by suitably positioning sleeves 51 on bars 52 and pulleys 56 on shaft 54.

The automatic device 49 for separating the examined printed circuits 6 comprises a pneumatic jack 59, provided with opposed rods, transversely fastened to members 50 below the horizontal lying plane of belts 57, which is electrically connected to the processor; said processor controls the motions thereof in a transverse direction according to the data detected on the printed circuit 6 examined in the checkout unit 5. Close to said jack 59, that is above it and in the vicinity of one of the two belts 57 there is a third micro-switch 60 suitable to be contacted by the printed circuits 6 in transit. This micro-switch 60, which is connected to the processor, is used to reveal the presence of a printed circuit 6 at that point of the machine, to the processor itself.

The processor, after sorting the sequence of the checkouts carried out on circuits 6 causes, through the jack 59, the opening (or not) of members 50 when each circuit 6 contacts the micro-switch 60. The operation of jack 57 will therefore take place if the circuit 6 contacting the micro-switch 60 appears faulty as a result of the checkout previously carried out in unit 5.

Below the end portion 4 of the machine 1 a reception shelf (not shown) is provided for faulty printed circuits 6 while a storing apparatus (not shown) for printed circuits 6 devoid of manufacture defects is provided downstream of the machine 1 itself, with respect to the feed-in direction of belts 57.

Obviously the operating steps of the machine 1 will be set so that a sufficient spacing between the printed circuits 6 in transit on the checkout unit 5 and on the separation device 49 is achieved.

It should be noted that the machine in question, owing to its structure and conception is able to use a checkout unit of the universal type and therefore capable of testing printed circuits of different sizes.

The invention attains the intended purposes.

Obviously, the embodiment of the invention described above is not intended to comprise a limitation; particularly, several modifications concerning the nature and operation of the machine in question, which will be clear to those skilled in the art, could be made without departing from the spirit and scope of the invention itself.

Furthermore, all details could be replaced by technically equivalent elements and the materials used as well as the shapes and sizes could be whatever according to the different requirements.

Claims (9)

1. An automatic testing machine for printed circuits of the kind using a checkout unit (5) provided with a plurality of plugs or nails (13), electrically connected to a processor, suitable to be connected to homologous checkout points provided with holes disposed on a printed circuit (6) to be examined, said checkout unit (5) being movable at right angles to the lying plane of said printed circuit (6) thus allowing the insertion of part of said nails (13) into said checkout points, characterized in that it comprises::-a feed conveyor (30) horizontally movable in the direction of said checkout unit (5);-a loading device (31) for the printed circuits (6) to be examined, located upstream of said checkout unit (5) relative to said feed-in direction, suitable to pick up the same, one by one, from a stack (21) acting as a store, and to put them down upon said feed conveyor (30);;-a locating member (40), transverse to said feed-in direction, disposed close to said checkout unit (5), suitable to allow the contacting and positioning of each printed circuit (6) in transit, on said checkout unit (5) in register with said nails (13), said locating member (40) being movable at right angles, according to predetermined working steps, with respect to the feed-in direction of said feed conveyor (30), means (43) being provided for locking said feed conveyor (30) during the checking step of each printed circuit (6) in said checkout unit (5)tan automatic selection and separation device (49) for said printed circuits (6), disposed downstream of said checkout unit (5), electrically connected to said processor and controlled thereby.

2. A machine according to claim 1, characterized in that said feed conveyor (30) substantially consists of a pair of horizontal parallel powered belts (30) on which two opposed side ends of each printed circuit (6) coming from said stack (21) acting as a store respectively rest, the distance between said parallel belts (30) being adjustable according to the sizes of the printed circuits (6) to be examined and said belts (30) being mounted on corresponding pulleys (29-29') axially adjustable on their shafts of rotation.

3. A machine according to claim 2, characterized in that the stack (21) acting as a store is disposed above said pair of parallel belts (30) and is defined by four upright posts (22) connected at their lower part to corresponding longitudinal structural members (24) disposed outwardly to said belts (30) and substantially parallel to the latter, said longitudinal structural members (24) being supported by transverse bars (25) on which they are adjustable in place by altering their distance in connection with the sizes of the printed circuits (6) to be examined, at least two of said upright posts (22) being adjustable in their longitudinal position with respect to said longitudinal structural members (24), each of them being provided at its lower part with a sliding block (22') introduced in a corresponding longitudinal guide (23') obtained on each of said structural members (24).

4. A machine according to claim 1, characterized in that said loading device (31) for the printed circuits to be examined comprises a plurality of projections (32-33) provided with reciprocating movements transversely to the feed-in direction and disposed under said stack (21) of printed circuits, said plurality of projections (32-33) consisting, on each of the two sides of said stack (21), of one series of supporting projections (32) which are horizontally aligned and simultaneously movable, and of a second series of shaped projections (33) which are horizontally aligned too but disposed at an upper level with respect to the first projections, said shaped projections (33) being provided with simultaneous reciprocating movements in synchronism with said supporting projections (32) according to a sequence of steps suitable to allow the dropping of said printed circuits (6), one by one, onto said feed conveyor (30), the end (33') of each of said shaped projections (33) acting on the side edge of said printed circuits (6) being provided with horizontal grooves (39), the height of each groove corresponding to the thickness (S) of one printed circuit (6).

5. A machine according to claim 4, characterized in that said supporting projections (32) and said shaped projections (33) are connected to two corresponding series of control levers (35-35') operated by horizontal rods (36-36') each of them being driven by a pneumatic jack (37-37').

6. A machine according to claim 1, characterized in that said transverse locating member (40) substantially consists of a horizontal plate (40) actuated, according to said predetermined working steps, by an electromagnet (48) disposed below it, said plate (40) being provided with a horizontal abutment edge (41) at right angles to said feed-in direction, suited for contacting and positioning a printed circuit (6) on said checkout unit (5).

7. A machine according to claim 1, characterized in that said means (43) for locking said feed conveyor (30) comprises a micro-switch (43) suitable to be contacted by said printed circuits (6), one by one, disposed close to said locating member (40) and electrically connected to the motor (28) of said feed conveyor (30).

8. A machine according to claim 1, characterized in that an evacuation conveyor (57) is provided downstream of said checkout unit (5) with respect to said feed-in direction and close to said automatic selection and separation device (49) for said printed circuits (6), said evacuation conveyor (57) comprising a pair of powered parallel horizontal belts (57) mounted on corresponding pulleys (56-58) on which the two opposed side ends of a printed circuit (6) respectively rest.

9. A machine according to claim 8, characterized in that said automatic selection and separation device (49) for said printed circuits (6) comprise a pneumatic jack (59) operated by said processor disposed in the vicinity of said evacuation conveyor (57), suitable to allow the pulleys (56-58) of said second pair of belts (57) to move away from each other transversely to the direction of motion of said evacuation conveyor (57), depending on the charcteristics of said printed circuit (6) examined by said checkout unit (5), said spacing away from each other causing the dropping of said printed circuit (6) onto a reception sheif placed below said evacuation conveyor (57).