Device for removing a peduncle from a printed circuit board

Abstract: A device (10) for removing a connecting peduncle passing through a separation slot between two printed circuit boards comprises a moving element (13) having reciprocating motion to bring a cutting face (14) thereof which is formed under a projection projecting from a shank between a pair of bucking elements (17, 18) facing each other to identify at least in an initial section thereof a seat in which the projection is insertable without play. The transverse dimension of the moving element (13) is such as to be received in a sliding manner guided in the slot to receive said peduncle between its cutting face and the edges of the bucking elements. Upon operation of the motor means (11) the moving element (13) cuts the peduncle while the bucking elements (17,18) engage with sharpened surfaces (15,16) at the sides of the peduncle to avoid transmission of transverse strains in the printed articles to be separated.

Description: In the art of mass production of printed circuits there are often provided multiples of the same printed article in a single plate to be later separated from each other after completion of treatment and mounting of the components. Said art is advantageously applied especially with small printed circuits the handling of which whether manual or automatic would be difficult if taken individually, especially in the assembly and welding phase of the components thereof. Generally, to make easier the subsequent separation of the printed circuits during the production of the board the separation lines between them are milled, thus producing between the printed circuits of the board a slot broken only by small joining peduncles which are removed at the end of the assembly operations. In the known art various solutions to the problem of removing said peduncles have been proposed but they all suffer from various drawbacks which make them unsatisfactory. For example there are known numerically controlled machines which eliminate the peduncles by the automatic movement of a small milling head. The need to programme the machine on the basis of the conformation of the printed circuit boards to be treated makes the solution acceptable only for large production runs because of the high cost of said machine. In addition the production of dust is high and harmful to the quality of the electronic circuit being processed. Another separation method calls for the use of shears under which an operator positions sequentially the peduncles of the printed circuit boards to be separated. Said shears suffer however from the serious drawback of excessively stressing the printed circuit boards and causing cracking at the edges and possible detachment of the welded components. In addition the danger of said devices for the operator is high since only a brief distraction is enough to cause a serious injury. Lastly, good skill is required to obtain perfect removal of the peduncles without affecting other parts of the printed circuit board. As an alternative to the use of expressly made devices there are also used methods which call for the use of general purpose hand cutting tools such as nippers and the like and then hand filing of the ragged edges thus obtained. But it is clear that said systems produce considerable loss of time and results which are not always acceptable. In addition, with very small printed circuit boards the welded components are very near the edge and hence easily damaged during processing. The general object of the present invention is to obviate the above mentioned drawbacks by supplying a tool for removal of peduncles between printed circuit boards which would be economical, easy and safe to use, and would give perfect trimming of the edges separated by it without stressing the printed circuit board and the components on it. In view of said object it has been sought to provide in accordance with the present invention a device for removal of a joining peduncle passing through a slot separating two printed circuit boards and characterized in that it comprises a moving element having reciprocal motion to bring a cutting face thereof, formed under a projection projecting laterally from a shank between a pair of bucking elements facing each other to identify at least in an initial section thereof a seat in which the projection can be inserted without play, the transverse size of the moving element being slightly smaller than the width of the slot, so that it is received in a sliding manner and guided in the slot to receive said peduncle between the cutting face and the edges of the bucking elements. To further clarify the explanation of the innovative principles of the present invention and its advantages as compared with the known art there is described below with the aid of the annexed drawings possible embodiments as examples applying said principles. In the drawings FIG. 1 shows a side elevation view of a separating device in accordance with the present invention, FIG. 2 shows a partial cross section view along plane of cut II-II of FIG. 1, FIGS. 3 - 5 show enlarged cross section views of an operative sequence of the device of FIG. 1, FIG. 6 shows a side view of FIG. 3, and FIG. 7 shows a perspective view of the device of FIG. 1 during its use. With reference to the FIGS. a removing device, indicated generally by reference number 10 in FIG. 1, in accordance with the present invention comprises a motor body 11 for operation of a cutting head 12. As can be seen better in FIG. 2 the cutting head 12 is made up of an element 13 which slides inwardly of the cutting head upon operation of the motor means contained in the body 11. The sliding element 13 has a generally L-shaped form and displays a cutting face 14 facing bucking surfaces 15 and 16 belonging to two laminations or bucking elements 17 and 18 arranged at the two sides of the element 13. Between the two laminations are also included plates 19 and 20 to define a seat for sliding passage of the element 13. Laminations 17, 18 and plates 19, 20 are packed and fixed between spurs 21 and 22 projecting from the body 11. As can be seen clearly in FIG. 3 the cutting face 14 extends longitudinally with a concave surface with side cutting edges inclined inward at an angle α. The bucking surfaces 15, 16 are inclined opposite to each other at an angle β. In addition the laminations 17 and 18 are relieved internally at 24 and 25 respectively. In using the device the element 13 is fitted in the slot existing between two printed circuit boards, indicated in FIG. 4 generally by 26 and 27. The thickness "s" of the moving part 13 is provided to be only a few hundredths of a millimetre less than the slot so that the element 13 can slide freely, guided accurately by said slot until it reaches a first peduncle 28 which unites printed circuit boards and which, in this manner, abuts under the surface 14 as may be seen clearly in FIG. 6. When operating the motor means contained in the body 11 the element 13 retracts, sinking the side edges into the peduncle flush with the walls of the slot between the printed circuit boards. At the same time the bucking surfaces 17 and 18 engage below with the sides of the peduncle preventing the two printed circuit boards 26 and 27 from drawing apart under the effect of the cutting element 13. The sharp edge of the bucking surfaces must cut into the surface of the peduncle to hold the printed circuit boards in position without the bucking members sinking excessively. The inclination of the bucking surfaces 15 and 16 also prevents the printed circuit boards from bending upward under the effect of the sinking of the cutting face 14. For this purpose the angle β has been found to be advantageously between 4° and 30° and preferably about 15°. During continuance of the cutting action (FIG. 4) the peduncle is compressed by the concave form of the surface 14 so as to detach itself from the cutting edges without stressing the printed circuit boards at the sides. To obtain a good cut it has been found that the angle α can advantageously be between 20° and 50°. Preferably said angle can be about 30°. As shown in FIG. 6, to facilitate the sinking of the cutting edges of the face 14 in the peduncle said edges are inclined at an angle with respect to the longitudinal direction of the extension of the cutting face. Said angle has been found advantageously to be between 5° and 20° and preferably about 10°. When the peduncle is completely cut the further travel of the element 13 pushes it (FIG. 5) into the widened zone of the bucking elements so that it is released and is removed thanks to the chute conformation of the surface 29 between said bucking members. The peduncle is thus completely eliminated and the resulting edges of the slot between the printed circuit boards are perfectly finished. The element 13 then returns to the initial position and the tool can be guided along the slot between the printed circuit boards until it meets the next peduncle to be removed. As may be seen, with a cutting head in accordance with the present invention the peduncles are removed rapidly and accurately without producing dust or transmitting excessive stresses to the printed circuit boards and the components thereof. FIG. 2 shows a possible embodiment of the power unit 11. The shank of the element 13 is connected to a rod 30 of a compressed actuator unit to be moved against the action of a spring 31. To obtain a favourable ratio of space occupied to power the compressed actuator unit is provided by means of two coaxial pistons 32, 33 supported on the rod 30 to slide in separate chambers 34, 35 respectively. The rod 30 is drilled axially at 39 to supply compressed air to the two chambers 34, 35 for operating a valve 36. In particular, compressed air arriving from a duct 37 is supplied to the valve 36. A slide valve 38 when driven by a lever 23 places the duct 37 in communication with the duct 39 which supplies the pistons so as to control the element 13 in its cutting travel. Next the slide valve 38 puts the duct 39 in communication with an exhaust duct 40 so that the spring 31 can recall the pistons 32 and 33 and then return the element 13 to its rest position. Advantageously the lever 23 is partially protected by a shell 41 to prevent accidental operation thereof. The embodiment just described is usable as a hand tool by forming the case 11 in a graspable manner so that the tool can be used as shown in FIG. 7. Said solution provides a very manageable, fast and accurate tool, the cutting head being guided by the slots 42 between the printed circuit boards. In addition, safety is very high because the space between the cutting face 14 and the strikers 15, 16 is very limited and hence at the worst can only pinch the operator's skin in case of improper use or accidental contact. Naturally the above description of an embodiment applying the innovative principles of the present invention is given merely by way of example and therefore is not to be taken as a limitation of the patent right claimed here. For example, it can be readily imagined how the peduncle removing unit described can be used as a device fixed to a bench while the printed circuit board is moved manually. In addition the motor means can be different than shown. For example, if the dimensions of the motor body do not constitute a problem the two pistons can be replaced by a single larger piston. It could also be imagined to use motor means operating differently such as, for example, electrical motor means consisting of an electric motor with reducing gears.

Claims: Device for removal of a joining peduncle passing through a slot separating two printed circuit boards and characterized in that it comprises a moving element (13) having reciprocal motion to bring a cutting face (14) thereof formed under a projection projecting laterally from a shank, between a pair of bucking elements (17, 18) facing each other to identify at least in an initial section thereof a seat in which the projection can be inserted without play, the transverse size (S) of the moving element being slightly smaller than the width of the slot, so that it will be received in a sliding manner and guided in the slot (42) to receive said peduncle (28) between the cutting face and the edges of the bucking elements. Device in accordance with claim 1 characterized in that the cutting face of the moving element extends longitudinally with a concave surface identifying sharpened lateral cutting edges. Device in accordance with claim 1 characterized in that the bucking elements are applied laterally to a guide body for the shank of the moving element. Device in accordance with claim 1 characterized in that the bucking elements have supporting faces (15, 16) for supporting the peduncle conformed in an opposing inclined manner to form each a sharp edge near said seat. Device in accordance with claim 1 characterized in that the bucking elements have at the end of their initial section in which is inserted the moving element, an increase of the mutual distance to form the initial path of discharge of the removed peduncle. Device in accordance with claim 2 characterized in that the sharpened edges of the cutting face have an angle (α) between 20° and 50° and preferably about 30° with the parallel side faces of the projection of the moving element. Device in accordance with claim 1 characterized in that the cutting face is inclined with respect to the longitudinal direction of the extension of the projection at an angle between 5° and 20° and preferably about 10° with the edges of the bucking elements. Device in accordance with claim 1 characterized in that the shank of the moving element is operatively connected to motor means to be drawn against the action of elastic means (31) in the direction of approaching said cutting face to the bucking elements. Device in accordance with claim 8 characterized in that the motor means are contained in a graspable case. Device in accordance with claim 8 characterized in that the motor means comprise compressed air actuators. Device in accordance with claim 10 characterized in that the compressed air actuators comprise two coaxial pistons (32, 33) with a common shank (30) and bearing at one end the shank of the moving element. Device in accordance with claim 8 characterized in that the elastic means are provided in the form of a spring. Device in accordance with claim 11 characterized in that the two coaxial pistons are supplied by a compressed air source through a duct (39) made coaxially in the rod. Device in accordance with claim 9 characterized in that the motor means are operated by a manual control positioned on said case. Device in accordance with claims 10 and 14 characterized in that the manual control comprises a lever (23) placed on the side of the case (11) to control upon operation the opening of a valve (38) to supply compressed air to said compressed air actuators. Device in accordance with claim 4 characterized in that the faces inclined in an opposing manner of the bucking elements form with a plane passing through both of said sharp edges an angle (β) between 4° and 30° and preferably about 15°.

Inventors: BROSADOLA GIANNI, BROSADOLA, GIANNI
Applicants: BROS ITALIA SRL, BROS ITALIA S.R.L.
Application year: 1991
Main classification: H05K3
IPC codes: H05K3, B26B15, B23D27