WO2002072309A1

WO2002072309A1 - High capacity tool crib for a machine tool for the processing of printed circuit boards

Info

Publication number: WO2002072309A1
Application number: PCT/IT2002/000154
Authority: WO
Inventors: Giacomo Aufiero
Original assignee: Acd Technologies S.P.A.
Priority date: 2001-03-13
Filing date: 2002-03-13
Publication date: 2002-09-19
Also published as: EP1370390A1; ITTO20010230A0; TW551005B; ITTO20010230A1

Abstract

The tool crib (19) is carried by a fixed plate (20) and includes a series of linear cassettes (21), each fitted with a row of tools (14). The linear cassettes (21) are carried by a cogged belt (32) movable on a closed trajectory (31). The belt (32) is made of flexible material and engages at least two belt pulleys (33, 34), each cassette (21) being housed in a corresponding cassette holder member (37), so that the row of tools (14) is at right angles to the closed trajectory. The cassette holder members (37) are guided by two fixed guides (48). At a tool (14) change station (58), the fixed plate (20) is fitted with a notch (55). Two locking arrangements (59) are able to operate two jaws (61) to lock the sticks (21) in the tool (14) change position. The tool (14) change that is carried out by pincers (62) movable vertically and transversely.

Description

HIGH CAPACITY TOOL CRIB FOR A MACHINE TOOL FOR THE PROCESSING OF PRINTED CIRCUIT BOARDS.

TECHNICAL FIELD The present invention concerns a high capacity tool crib for a machine tool for the processing of packs of printed circuit boards, and a relative machine tool fitted with such tool crib.

BACKGROUND ART

In the processing of packs of printed circuit boards, it is necessary to make a large number of holes of different, generally very small, diameters. The tools are subject to wear, and must be replaced very frequently, both due to wear as well as to change the diameter of the holes themselves. Moreover, to increase the productivity of the machine tool, some machine tools have been proposed that are fitted with various operating heads, able to work simultaneously.

Different types of tool- cribs are known. In general, for each operating head is envisaged a corresponding tool crib, and a tool change device between each operating head and the relative tool crib. A known tool crib .has the tools disposed according to a row and column matrix, so the tool capacity is very limited. Another known tool crib consists of a drum which is able to house a series of tool sticks, to help the manual replacement of the used tools in the tool crib. Nevertheless, this tool crib also has a limited capacity. In addition, this tool crib requires the machine to be stopped for the replacement of the sticks, so the cost of processing proves relatively high.

A machine tool has also been proposed with a large number of operating heads and a tool crib, common to the operating heads, in which the tool crib is disposed far from the processing area, so ' as to allow both the use of a high capacity tool crib as well as the replacement of the sticks of the tool crib during processing. This tool crib is joined to a transfer device which is able to distribute the tool sticks to a series of intermediate stations, without stopping the machine tool, which is also fitted with a series of tool change devices between the various operating heads and the relative intermediate stations. This tool crib is very efficient, but proves relatively expensive due to the transfer device at the intermediate stations.

A high capacity tool crib has also been proposed, which is common to a series of operating heads and is able to bring the tool sticks directly into a series of tool change stations, joined to the operating heads. This high capacity tool crib is formed by a large number of rigid mother support members, fixed around a fulcrum between, and movable along, a closed trajectory, each mother support member being able to hold a large number of dependent support members, each able to house a stick of tools. The closed trajectory is obtained by means of a rigid guide carried by a frame of basically rectangular shape, which is normally disposed near the processing area. The frame is connected to a protective cover of the operating heads, so that, by opening such cover, the tool crib is moved away from the processing area to allow the replacement of the tool sticks.

This high capacity tool crib has some drawbacks. First of all, due to the rigid mother support members articulated with each other, the tool crib is relatively noisy, heavy and expensive. In addition, its arrangement inside the protective cover limits the tool capacity of the tool crib. Lastly, it requires a complicated shifting mechanism connected to the cover to gain access to the work area of the table.

DISCLOSURE OF INVENTION

The aim of the invention is to realize a high capacity tool crib for a machine tool for the processing of packs of printed circuit boards, which requires no shifting for the replacement of the tool sticks, and which proves to be of high reliability and of limited cost, eliminating the aforesaid drawbacks for the tool cribs known to the art.

According to the invention, this aim is reached by a high capacity tool crib for a machine tool for the processing of packs of printed circuit boards, including a series of sticks each fitted with a row of tools side by side, and movable means along a closed trajectory to support said sticks, in a removable way, so that said row of tools is at right angles to said trajectory; characterized in that said movable means include a belt of flexible material engaged with at least two belt pulleys.

In particular, each stick is basically prismatic bar shaped, with a series of parallel seats, each able to house one of said tools, said belt being fitted with a series of stickholder members, each able to house a stick of tools in a removable way.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better comprehend the invention, herein described are two preferred embodiments, done by way of example with the help of the enclosed drawings, in which:

Figure 1 is a partial and schematic perspective view of a machine tool, incorporating a high capacity tool crib according to a first embodiment of the invention; Figure 2 is a perspective view of the tool crib of Figure 1, in enlarged scale;

Figure 3 is a perspective view of a stickholder member, in subsequently enlarged scale;

Figure 4 is a vertical section according to the line IV-IV of Figure 3;

Figure 5 is a partial lengthwise section of the tool crib of Figure 2 ;

Figure 6 is a cross-section of the tool crib of Figure 2;

Figure 7 is a detail of Figure 2, in subsequently enlarged scale; Figure 8 is a schematic view of a tool crib of the tools for the machine of Figure 1, according to another embodiment of the invention;

Figure 9 is a perspective view of a detail of Figure 8, in enlarged scale; Figure 10 is a perspective view of the detail of Figure 9, taken from another angle;

Figure 11 is a vertical section of a detail of Figure 10;

Figure 12 is a section according to the line XII-XIV of Figure

11; Figure 13 is a vertical section of another detail of Figure

10;

Figure 14 is a vertical section of a contrivance of the tool crib of Figure 8;

Figure 15 is a section according to the line XV-XV of Figure 14.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figure 1 , a machine tool is generically denoted by 5, for the processing of packs 6 of printed circuit boards, e.g. a perforating machine. In Figure 1, a pack 6 to be perforated is schematically illustrated by dotted lines. The machine tool 5 essentially includes a rigid bed 7, carrying a worktable 8, which defines a work area on which the pack 6 can be fixed. The machine tool 5 also includes a pair of crosspieces 9, which are movable as regards the table 8, parallel to themselves, along a Y axis, at right angles with respect to the crosspieces 9.

Each crosspiece 9 carries at least one carriage 11 movable along an X axis, parallel to the crosspieces 9. In particular, each crosspiece 9 ' carries two carriages 11 movable independently of each other, each of which is fitted with an operating head 12, able to slide along a vertical Z axis. The head 12 is fitted with a rotating spindle 13, which is able to house, a tool 14, with a cylindrical tang 15 (see also Figures 2 and 3) . Each crosspiece 9 is able to be brought into a corresponding rest position 16, disposed outside the work area of the table 8, while each carriage 11 is able to be brought into a corresponding rest position 17 along the relative crosspiece 9, it also being disposed outside the work area of the table 8.

The position assumed by each operating head 12 when the relative crosspiece 9 and the relative carriage 11 are situated in the respective rest positions 16 and 17, represents the rest position of the operating head 12 for the change of the tool 14 in the relative spindle 13. At the rest position of each operating head 12, the machine 5 is fitted with a tool change device, generically denoted by 18, which will be better seen afterwards. Lastly, the machine 5 is fitted, on each side, with a corresponding tool crib, generically denoted by 19, with a high tool 14 capacity. Each tool crib 19 is schematically represented in Figure 1, and is common to two operating heads 12 of the two crosspieces 9. Each tool crib is carried by a plate 20 fixed in a known way on the bed 7, so the tool crib 19 is disposed at the rest position 17 of the two carriages 11.

Each tool crib 19^' includes a series of sticks 21 (Figures 2 and 3) , each of which is fitted, side by side, with a row of tools 14 in a known way. In Figure 3, only one tool 14 of the row is shown for reasons of simplicity. In particular, each stick 21 is of standard type in the industry of printed circuit board processing, and is formed by a plastic bar 22, of basically prismatic shape, equipped with two slightly tapered ends 23. The bar 22 is fitted with a series of fourteen cylindrical -seats 24, each able to house the tang 15 of a tool 14. The seat 24 extends outwards into a cylindrical appendix 26 protruding slightly from the bar 22. The bar 22 is also fitted with, on each side, a notch 25, in which an elastic element 27 is disposed, for example made of rubber, able to axially hold the tools 14 in their seats 24 by friction. The bar 22 is fitted with two lateral prismatic ribs 28, and a surface 29 opposite the appendices 26, in which a central hollow 30 is disposed, for the positioning of the bar 22.

According to the invention, each tool crib 19 includes some movable means along a closed trajectory 31, denoted by a dot- dash line in Figure 1, for the support of a series of sticks 21. Such movable means are made up of a cogged belt 32 made of flexible material, e.g. rubber reinforced with flexible and inextensible fibres, which is engaged with at least two belt pulleys 33 and 34. The sticks 21 are disposed on the belt 32, so that the row of tools is at right angles to the trajectory of the belt 21 itself, preferably at a constant mutual distance.

The pulleys 33 and 34 are disposed so as to define a rectilinear portion 36 of the trajectory 31, parallel and adjacent to the bed 7 of the machine tool 5. The length of the trajectory 31 of the belt 32, and therefore the tool 14 capacity in the tool crib 19, depends on the distance between the two pulleys 33, 34 and, if necessary, the presence of one or more transmission pulleys, disposed above the pulleys 33 and 34. The pulley 33 is turned by a reversible electric motor, not shown in the drawings, which is intermittently operated under the control of the usual numeric control unit of the machine tool 5.

According to the embodiment of the Figures 1-7, the pulleys 33 and 34 are rotating on two horizontal axes, carried by corresponding pairs of support members 35 fixed on the plate 20. Therefore, the belt 32 is disposed so that, in the rectilinear portion 36 of the trajectory 31, it keeps the tools 14 vertical, with the bit turned downwards. The belt 32 is fitted with a series of stickholder members 37 (Figures 2- 6), each of which is able to house a stick 21. Each stickholder member 37 is formed by a U-section plastic bar 38, of shorter length than that of the stick 21. The bar 38 is fixed on the belt 32, by means of two screws 39, which are able to engage two corresponding threaded bushings 41, incorporated in the elastomeric material of the belt 32. Preferably, the bushings 41 are incorporated in correspondence of a tooth of the belt 32, as shown in Figure 5, to allow a more rigid support for the stickholder member 37.

The two wings of each bar 38 are fitted with two internal grooves 42, of prismatic section, which are able to be engaged by the two prismatic ribs 28 of the stick 21, so the stick 21 can be slide inserted into the stickholder member 37. This stickholder member 37 is fitted with an elastic positioning dowel, known in itself, which is formed by a ball 43 (Figure 4) disposed in a cylindrical seat 44, and pushed by a compression spring 46 in a direction which is parallel to the tools 14. The ball 43 is able to engage the hollow 30 of the surface 29 of the stick 21.

Each bar 38, at its two ends, is fitted with two guide elements, formed by two prismatic grooves 47, which are able to engage two corresponding fixed guides 48, prismatic and parallel to the trajectory 31 of the belt 32. In particular, the fixed guides 48 are carried by two pairs of L-section lower 49 and upper 51 bars, each pair being parallel to the two rectilinear portions of the trajectory 31. The bars 49 and 51 are fixed on a frame 52 including a first series of crosspieces 53 carried by columns 54 fixed on the plate 20, and on which the lower bars 49 are fixed, and a second series of crosspieces 56 carried by other columns 57 fixed on the bars 49, and on which are fixed the upper bars 51. Therefore, the trajectory 31 proves perfectly rigid along its entire length thanks to the bars 49 and 51 and the pulleys 33, 34.

The plate 20 is fitted with two notches 55 at the two tool 14 change stations 58, and thus at each tool change device 18. At each station 58, are envisaged two contrivances 59 (Figures 6 and 7), which can be operated so as to engage the two ends 23 of the stick 21, when this is brought by a relative stickholder member 37 disposed in the corresponding station 58. In particular, each contrivance 59 is made up of a pneumatic cylinder, able to operate a jaw 61 to engage it with the corresponding tapered end 23 of the stick 21.

Each tool change device 18 includes pincers 62, known in themselves, which are able to engage a tool 14. The pincers 62 are movable vertically between a low position and a high position, to insert or extract a tool 14 in the spindle 13 or in the tool crib 19. The pincers 62 are carried by a slide, not shown in the drawings which, when the pincers 62 are situated in the low position, is transversely movable by a variable stroke between the position of the spindle 13 and one of the seats 24 of the stick 21.

The operation of the machine tool 5, for the selection and the change of a tool 14, is as follows.

It is assumed that a certain number of stickholder members 37 (Figures 1 and 2) of the two tool cribs 19 are already loaded with the relative sticks 21 of new tools 14, a pack 6 of circuit boards is fixed on the table 8, and that an already worn tool 14 is inserted in one or more spindles 13. Each tool crib 19 has a stick 21 in the tool change station 58, locked by the jaw 61 (see also Figures 6 and 7), and has a seat 24 without a tool, from which the tool 14 of the spindle 13 was extracted. At first the control unit moves the operating head 12 and the relative crosspiece 9 into the respective rest positions 17 and 16. Then the control unit operates the relative pincers 62 so as to extract the used tool 14 and to put it back into its seat 24. Then, if the new tool 14 is in the same stick 21, the pincers 62 are moved to the seat 24 of the new tool 14. If, however, the new tool 14 is in another stick 21, the pulley 33 is then turned which moves the belt 32 so as to bring the new stick 21 into the station 58. In both cases, the pincers 62 are brought to the seat 24 of the new tool 14, and extract the selected tool 14. Lastly, the pincers 62 move to insert the new tool 14 into the spindle 13 and move back to their low position.

During processing, the operator of the machine tool 5 can carry out the replacement of the sticks 21 of used tools 14, with sticks 21 of new tools 14, at any point of the trajectory 31, preferably at the driven pulley 34, disposed on the rear area of the machine 5.

Figures 8-15 contain another embodiment of the invention. In it, the parts that are similar to those of the Figures 1-7 are denoted by the same reference numbers, and will only be described briefly. The two pulleys 33 and 34 are here rotating around two vertical axes, so in the rectilinear portion 36 of the trajectory 31 of the cogged belt 63, this keeps the tools 14 of the sticks 21 in a horizontal position. The stickholder member 37 includes an L-section bar 64, similar to that of bar 38, but which is closed at the bottom by a portion 69.

A stick 21 can be inserted in the bar 64, which is kept placed against the portion 69 by an elastic element including a slider 65 (Figures 11 and 12) able to slide in a seat 70 of the bar 64. The slider 65 is pushed by a spring 71 so as to engage one of its 'wedge-shaped ends, with a furthermost inclined portion 72 of the surface 29 of the bar 22. On the slider 65 is fixed, by means of a pin 73 able to slide in a seat 74, a knob 75, which can be hand operated to free the stick 21, overcoming the action of the spring 71.

The bar 64 is of greater length than the stick 21 and has an appendix 66 fixed around a fulcrum on a pin 67 carried by a fastener 68, which is fixed on the belt 63 by means of two screws 39. The element 68 is fitted with a circle arc seat 76, in which a peg 77 is guided, fixed on the appendix 66. Each bar 64 has, on its upper end, a roller 78 rotating on an axis parallel to the bar 64, which engages an inverted U-shaped upper rail 79. On the lower end of the bar 64 is instead disposed a roller 80 rotating around an axis perpendicular to the bar 64, which engages a lower U-shaped rail 81. The two rails 79 and 81 are disposed parallel to the entire trajectory 31, also around the pulleys 33 and 34. The lower rail 81 is fixed to the plate 20, by means of a series of columns 82, while the upper rail 79 is carried by a frame formed by a bar 82' fixed on two axes of the pulleys 33 and 34, and carrying a series of crosspieces 83, on which the upper rail 79 is fixed. At each station 58 of tool 14 change, there is an interruption in the two rails 79 and 81, to allow the stickholder member 37 to rotate through 90°. At the interruption of the rails 79 and 81 to ensure a rigid guide for the belt 63, a pair of idle belt pulleys 84 is envisaged, with which the belt 63 engages. In addition, in front of the interruption of the upper rail 79 a vertical plate 85 is disposed, which is fitted with two columns 86, able to slide in two guides 87, fixed on the rail 79 itself. The plate 85 is besides fixed, by means of a bracket 88, on a rod 89 able to be operated by a pneumatic cylinder 90.

The bar 64 is besides fitted with two holes 91, each able to be engaged by a corresponding peg 92 (Figure 13) when the bar

64 is turned in a horizontal position. Each peg 92 is fixed on a piston 93 operated by a corresponding pneumatic cylinder 94, so as to lock the stick 21 in the bar 64 during the change of tools 14, carrying the stick 21 to rest against the wall of the bar 64, opposite the pegs 92.

Each station 58 is fitted with pincers 62 of change of tool 14, similar to those of Figure 7. Only one station 58 is shown in Figure 8, that can be joined to only one operating head 12, e.g. in the case of a machine tool 5 having only one crosspiece 9. Alternatively, the station 58 can be joined to two or more operating heads 12 carried by two crosspieces 9 as in Figure 1, but the tool 14 change operations must be carried out at different times.

At the station 58 is also disposed a contrivance generically denoted by 95 (Figure 10) which includes a link element, formed by a bar 96, which is fitted with a notch 97 able to be engaged with the peg 77. In particular, the bar 96 is fixed, by means of a plate 98 (Figures 14 and 15) on a rod 99 able to be operated by a double-acting pneumatic cylinder 100, which is disposed with its axis basically vertical. The cylinder 100 is fitted with two opposite pins 101, rotating on two fixed appendices 102, and is fixed lower down on a fork 103 connected by an articulated joint with a rod 104 operated by a second pneumatic cylinder 105, which is fixed around a fulcrum on a fixed pin 106.

Lastly, a contrivance 107 (Figure 10) is disposed at the station 58, made up of a pneumatic cylinder 108 able to operate a corresponding locking member, or piston 109, which is able to engage a hollow 110 disposed on the end of the bar 64 opposite that of the appendix 66 (Figure 9) .

To select a new tool 14 of the tool crib 19 of the Figures 8- 15, the belt 63 is moved so as to bring the desired stick 21 to the station 58. Then the pneumatic cylinder 90 moves the vertical plate 85 upwards which frees the interruption of the rail 79, and no longer constrains the stickholder member 37. Operating the cylinder 105, the rod 104 now makes the cylinder 100 turn in a clockwise direction on the axis of the two pins 101, engaging the notch^' 97 of the bar 96 with the peg 77 of the bar 64.

Afterwards, the cylinder 100 is operated, which moves the rod 99 downwards together with the bar 96, therefore the bar 64 is turned so that the relative stick 21 temporarily arranges the tools 14 with their axis vertical. The contrivance 107 is operated, which engages the piston 109 in the hollow 110, so as to lock the bar 64 in the turned position. Lastly, the two pneumatic cylinders 94 are operated, whose pistons 93 carrying the pegs 92 now lock the stick 21 against the wall of the bar 64, locking it in the tool 14 change position. The change of the tool 14 is now carried out in a similar way to that seen for the embodiment of Figures 1-7.

When another stick 21 is to be selected, one carries out the reverse movements of the pegs 91, of the piston 99 and of the link bar 96, so the bar 64 returns to the vertical position. Then the vertical plate 85 moves downwards, so the continuity of the rail 79 is restored. Lastly, the belt 63 of the tool crib 19 is made to slide again, selecting the new stick 21. Also in this case the sticks 21 can be replaced on the bars 64 in any area of the belt 63. For this purpose, operating the knob 75, unlocks the stick 21 from the bar 64, the stick 21 of the used tools 14 is extracted upwards, and a stick 21 of new tools 14 is inserted.

From that seen above the advantages of the tool crib 19 according to the invention appear clear with respect to known tool cribs. First of all, the capacity of the tool crib 19 can be easily increased by adding some transmission pulleys and replacing the belt 32, 63 with a belt of greater length. The belt 32, 63 besides proves to be very silent and of limited weight and cost. Finally, the tool crib 19 does not require any shifting to gain access to the work area of the table 8.

Naturally, various modifications and improvements can be made to the tool crib described and/or to the relative machine tool fitted with such tool crib, without leading away from the scope of the claims.

For example, the tool crib 19 of the Figures 1-7 can be fitted with just one notch 55 of the plate 20, to serve the two operating heads 12 in sequence. Furthermore, the tool crib 19 can be applied on a machine tool with a table movable with respect to a crosspiece fitted with several operating heads. In that case, there can be envisaged as many tool 14 change stations as there are machine spindles.

With the embodiment of the Figures 8-15, a single tool crib 19 can be envisaged with a length so as to serve the operating heads 12 on the two sides of the machine tool 5 of Figure 1, or so as to serve several adjacent machine tools 5. In addition, the lateral locking of the stick 21 in the bar 64 can be eliminated, while the axial locking carried out by the piston 109 can be carried out by acting on the tapered end of the bar 22 by means of a jaw similar to the jaw 61 of Figure 7. Lastly, the linking and rotation of the bar 64 can be obtained by a different kinematic motion to that of the cylinders 100 and 105 illustrated in the Figures 14 and 15.

Claims

1. High capacity tool crib for a machine tool for the processing of packs of printed circuit boards, including a series of sticks (21), each fitted with a row of tools (14) side by side, and movable means (32, 63) along a closed trajectory (31) to support said sticks (21), in a removable way, so that said row of tools (14) is at right angles to said trajectory (31) ; characterized in that said movable means include a belt (32, 63) of flexible material engaged with at least two pulleys (33, 34) .

2. Tool crib as in claim 1, characterized in that said sticks (21) are fixed on said belt (32, 63) at a constant mutual distance.

3. Tool crib as in claim 1 or 2, characterized in that said belt (32, 63) is rubber reinforced with flexible and inextensible fibres.

4. Tool crib as in one of the previous claims, characterized in that said belt (32, 63) is cogged and is engaged with at least two belt pulleys (33, 34) disposed so as to define a rectilinear portion (36) of said trajectory (31) .

5. Tool crib as in one of the previous claims, in which each of said sticks (21) is in the shape of a basically prismatic bar (22) and with a series of parallel seats (24) each able to house one of said tools (14), characterized in that said belt (32, 63) is fitted with a series of stickholder members (37), each able to house a stick (21) of tools (14) .

6. Tool crib as in claim 5, characterized in that each of said stickholder members (37) has at least one prismatic groove (42) able to engage a corresponding prismatic rib (28) carried by said stick (21), said stickholder member (37) being fitted with el'astic positioning means (42, 46; 65) of the stick (21) along said groove (42) .

7. Tool crib as in claim 5 or 6, characterized in that said belt (32, 63) is fitted with threaded bushings (41) incorporated in said elastomeric material and able to be engaged by fastening screws (39) of said stickholder members

(37) .

8. Tool crib as in one of the claims from 5 to 7, characterized in that each of said stickholder members (37) is guided by two fixed guides (48; 79, 81) parallel to said trajectory (31) .

9. Tool crib as in claim 8, characterized in that at each tool (14) change station (58) said stickholder member (37) assumes a position of tool (14) change, locking means (59, 92) being envisaged to lock said stick (21) on said stickholder member (37) .

10. Tool crib as in claim 8 or 9, characterized in that in said rectilinear portion (36) of said trajectory (31) said belt (32) is disposed so as to keep said tools (14) vertical, each of said stickholder members (37) being formed by a bar

(38) directly fixed on said belt (32) by means of at least two of said screws (39) .

11. Tool crib as in the claims 9 and 10, characterized in that said bar (38) is of lesser length than said stick (21), each end of said stick (21) including a tapered portion (23) protruding from said stickholder member (37) , said locking means including two contrivances (59) able to act on said tapered portions (23) , each of said contrivances (59) including a pneumatic cylinder able to operate a corresponding jaw (61) to engage it with the relative tapered portion (23) .

12. Tool crib as in ^'claim 6 and one of the claims 10 or 11, characterized in that said elastic means (42, 46) include a ball (42) pushed by a compression spring (46) acting in a direction parallel to said seats (24), said ball (42) being able to engage a hollow (30) carried by an external surface (29) of said stick (21) .

13. Tool crib as in claim 8 or 9, characterized in that in said rectilinear portion (36) of said trajectory (31) said belt (63) is disposed so as to keep said tools (14) horizontal, each of said stickholder members (37) including a bar (64) able to house said stick (21), said bar (64) being fixed around a fulcrum on a pin (67) of a fastening element

(68) connected with said belt (63) by means of at least two of said screws (39) .

14. Tool crib as in claim 13, characterized in that each of said bars (64) is of greater length than said stick (21), said stick (21) being fitted with an inclined portion (72) at one end and is closed at one end by a closing portion (69) , said positioning means including an element (65) operated by a spring (71) to push said stick (21) against said closing portion ( 69) .

15. Tool crib as in claim 14, characterized in that said bar (64) is fitted with two rollers (78, 80) at the two ends, able to engage said fixed guides (79, 81) .

16. Tool crib as in claim 15, characterized in that at each tool (14) .change station (58), said guides are fitted with an interruption, at least one of said guides (79, 81) being fitted with a plate (85) movable vertically at said interruption between a position which allows the rotation of said bar (64) and a position in which it completes said guide (79) .

17. Tool crib as in' claim 16, characterized in that at each tool (14) change station (58) is envisaged a contrivance (95) able to be operated to turn said bar (64) through 90° on said pin (67) to bring said stick (21) into a position of tool (14) change.

18. Tool crib as in claim 17, characterized in that said contrivance (95) includes a link element (96) able to be connected with said bar (64) by a first actuator (105) and a second actuator (100) able to operate said link element (96) to carry out said rotation.

19. Tool crib as in claim 18, characterized in that said two actuators consist of two pneumatic cylinders (100, 105) fixed around a fulcrum on a fixed structure (102, 106) , one (100) of said pneumatic cylinders (100, 105) being hinged on a rod (104) operated by the other pneumatic cylinder (105) .

20. Tool crib as in one of the claims from 17 to 19, characterized in that said bar (64) is locked in the turned position by a locking member (109) operated by another pneumatic cylinder (108), said bar (64) being fitted with one end having a hollow (110) able to be engaged by said locking member (109) .

21. Tool crib as in claim 20, characterized in that said locking means include two members (92) operated by two corresponding actuators (94) when said bar (64) is in the turned position, to lock said stick (21) in said bar (64) .

22. Machine tool for the mechanical processing of packs of printed circuit boards, including a worktable (8), an operating head (12) with a spindle toolholder (13), said operating head (12) being movable as regards said table (8) to move into a tool (14) change station (58, 79), and a tool (14) change device (18) of said spindle (13), characterized by a tool crib (19) of the tools (14) according to one of the previous claims .

23. Machine tool as in claim 22, in which said spindle (13) is rotating on a vertical axis, characterized in that said tool crib (19) can be selectively operated to bring a stick (21) of tools (14) into said station (58, 79) disposed with its axis vertical, said tool (14) change device (18) including pincers (62) able to extract a tool (14) from said spindle (13) and from said tool crib (19) and afterwards insert the extracted tool (14) into said tool crib (19) and into said spindle (13) .