Punching machine

Abstract

 A punching machine having a punching machine framework (7), a work plane (4) for work pieces (3), a handling assembly carried by said framework (7), a graduated workpiece checking bar (6) and a pair of workpiece-locking pincers (2) brought by said units (11) for each pincers (2), and a programme control unit (30), handling assembly, said graduated bar (6) being mobile in, and flush with a work plane (4), at least one pair of clamping the machine comprising a device (1) for automatic positioning each of the workpiece-locking pincers (2), including a slide member (9) for each pincer (2) slidably mounted on the said graduated bar (6), locking and retaining means (13) carried by said slide member (9) and locking means (10) arranged to lock and unlock said slide member (9) relatively to said graduated bar (6).

Description

[0001] The present invention relates to a punching machine provided with an automatic pincer positioning device.

[0002] Punching machines for metal plates or sheets are equipped with pincers to hold and to move the plates that are being worked on the work bench surface. Such pincers are mounted on a graduated horizontal reference bar in such a way that their position is established according to the size of each plate and the automatic work program that is set for it, as well in such a way that the punch head that carries the machine tools does not interfere with them during the punching operations.

[0003] For its part the graduated bar can move in two dimensions on the punching machine's working plane to present the plates, held still by the aforementioned pincers, to the machine tools brought by the punch head so that this can carry out the task as programmed and set by the logic that governs and controls each punching machine.

[0004] The positioning of the pincers that lock the plates in place is carried out strictly manually: such pincers are in fact slidably mounted along the graduated bar and when they have reached their pre-established position they are rendered rigid with the bar itself by means of clamps that can be locked or released with nuts and bolts provided for the purpose.

[0005] The positioning operations for the aforementioned pincers take up a significant amount of time for their completion since, in addition to the preparatory slackening of the screws and bolts that fasten them to the graduated bar and the subsequent tightening of them onto this when the position has been found, it is necessary to take the utmost care and to be very precise in registering these with the graduated references for each plate in order that the automated work program can be completed error-free.

[0006] The above pincer positioning operation has necessarily to be carried out each time the metal plate or sheet format is changed and therefore also the corresponding dedicated work program. Such changes become necessary numerous times during the course of a working day and so the resulting loss of time adds up to a significant amount, severely affecting the punching machine's productivity and thus also the costs of production.

[0007] Moreover, the manual positioning of the pincers may be subject to registration inaccuracies in relation to the predetermined graduated references for the work program, inaccuracies that essentially depend on the skill and care of the human operator and that, though of themselves slight in absolute terms, may lead to imprecise performance of the work that becomes exponentially extended until the punching machine becomes completely jammed when one of the pincers, in its cross movement, collides with the headstock.

[0008] The technical aim of this invention is to eliminate the above-mentioned problems of the state of the art by providing a punching machine having a device for the automatic positioning of the workpiece-locking pincers whereby the said positioning can be carried out with no need for any manual intervention and with the maximum precision in its execution.
This task and these aims are all achieved by a punching machine having a punching machine framework, a work plane, a handling assembly carried by said framework, a graduated workpiece checking bar and a pair of workpiece-locking pincers brought by said handling assembly, said graduated bar being mobile in, and flush with a work plane, at least one pair of clamping units for each pincers, and a programme control unit, characterised in that it comprises a device for automatic positioning each of the workpiece-locking pincers, including a slide member for each pincer slidably mounted on the said graduated bar, locking and retaining means carried by said slide member and locking means arranged to lock and unlock said slide member relatively to said graduated bar.

[0009] Further the features and advantages of the present invention will better appear from the description of a preferred, but not exclusive, embodiment of a punching machine having a device for automatic positioning plate-locking pincers, illustrated by way only of not limiting example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic front view of a punching machine provided with a device for the automatic positioning of plate-locking pincers in accordance with the present invention;

Figure 2 is a large-scale and schematic view of a plate-locking pincer in accordance with the present invention in a determined work position along the graduated workpiece bar; and

Figure 3 is a large-scale and schematic view of a plate-locking pincer in accordance with the present invention during its positioning stage along the graduated workpiece bar.

[0010] With particular reference to these drawings, 1 generally indicates a device for the automatic positioning of plate-locking pincers 2 on a work plane 4 of a punching machine 5.

[0011] The device 1 comprises a graduated workpiece checking bar 6 brought by a handling or conveying assembly (not shown as it is well-known to a person skilled in the art and its structure is outside the scope of the present invention) that is supported by the framework 7 of the machine 5 and mobile along two dimensions parallel to, and flush with, the work plane 4.

[0012] A slide or saddle 9 is slidably mounted and guided onto the graduated bar 6 and has one or a pair of bracket extensions 9a. At its lower portion the slide 9 carries one or a pair of lower support arms 8 projecting from it, e.g. in substantial parallelism with the brackets 9a. The slide 9 is formed with rear dovetail grooves 15 at its rear face 14 arranged to engage with respective longitudinal grooves 6a in the graduated bar in order to form a sliding joint therewith.

[0013] A first locking mechanism, generally indicated at 10, is provided for to lock and hold, upon control, the slide 9 tight to the graduated bar 6 or to let it free to slide along it. The locking mechanism 10 can be automatically actuated by a pair of upper and lower clamping cylinder-and-piston units 11, e.g. of a well known type normally provided on punching machines 5, designed to lock a plate 3 on the work plane 4.

[0014] Each plate-locking pincer 2 has its own actuator 12, e.g. a fluid operated jack, arranged to actuate a locking and retaining mechanism 13 for tightening hold of the plate 3 when this latter is in position for punching, i.e. when the pincers 2 are positioned, according to the program, along the graduated bar 6.

[0015] More particularly, the first locking mechanism 10 consists of at least a first lever member or spike 16 that is articulated at a pivot pin 17 to an upper portion of the slide 9 and has its rear end facing the graduated bar 6 terminating with a downwardly extending pawl o tooth 18 arranged to engage with the upper groove 15 of the graduated bar 6 through an opening or recess in the slide 9, whereas its front end is spring loaded at its lower face 19 by a resilient means, e.g. a pre-tensioned helical spring 20 mounted onto a support pin 21 that is borne by the support arms 8. The upper face 22 is designed to be engaged at the rear end of the spike 16 by the upper clamping cylinder-and-piston unit 11.

[0016] The support pin 21 has fine registration means, arranged to adjust the reaction force of the pre-tensioned spring 20, e.g. comprising a hexagonal head 23 coaxial to, and formed at the lower end of the support pin, a threaded rod 24 which is an extension of the support pin 21 integral with the hexagonal head 23 and designed to penetrate a counter-threaded hole (not visible in the drawings) that is formed coaxially to the support pin 21 in a traverse member 26 rigidly connected, e.g. welded, at its ends to the brackets 9a.

[0017] A washer 25 rests upon the hexagonal head 23 around the support pin 21 and acts as abutment member for the pre-tensioned spring 20 whose other end rest against the lower face 19 of the of spike 16.

[0018] The second locking mechanism 13 consists of at least one rocking lever 27 that is pivoted at an intermediate portion thereof to a pivot pin 28 secured to the support arms 8, and has its rear end 27a shaped as a fork for slidably and rotatably engaging with a pivot pin 29 secured to one and of the actuator 12, e.g. a jack, whose other end is carried by the slide 9. The front end 27b of the rocking lever 27 locates a roller pad 31 of plastics material having a longitudinal flattened portion 31a facing the work plane 4 and designed to rest on and engage with a metal sheet or plate 3 to be locked in position on the work plane 4, as is known in the art.

[0019] The operation of a device for the automatic positioning of plate-locking pincers in punching machines, according to the present invention, is described here below with specific reference to one only of the pincers 2 provided in the punching machine 5. The helical spring 20 keeps the spike 16 normally engaged at its pawl 18 with the upper groove dove-tailed profile groove 6a of the graduated bar 6, thereby keeping the pincer 2 constantly in its closed position for carrying out a punching operation.

[0020] In this configuration, the rocking lever 27 retains a metal sheet or plate 3 (Figure 2) by being pulled upwards at its end 27a owing to the action of the actuator 12.

[0021] When the pincers 2 have to be repositioned along the graduated bar 6, the latter moves along the work plane 4 bringing the pincers with it in sequence to collimate below the clamping cylinder-and-piston units 11. Upon being energized, clamping units 11 press on the upper face 22 of the spike 16. Such a pressure causes the spike 16 to rotate through a relatively small angle of a few degrees around the pivot pin 17, thereby causing the pawl 18 to move away from the groove 6a of the graduated bar 6. In this configuration, the pincer 2 is locked between the clamping units 11 while the graduated bar 6 is free to slide relative to the pincer 2 until this is collimated with a predetermined reference point on the graduated bar 6 as set by a program control unit 30 controlling the punching machine 5.

[0022] Once this position has been reached, the clamping units 11 are de-activated and thus the pawl 18 re-engages with the graduated bar 6 owing to the action or the spring 20.

[0023] The same operational stages are repeated also for the twin pincer 2 and the graduated bar 6, by being moved along the work plane 4, reaches a predetermined position where the rocking levers 27 of the pincers 2 through their respective rollers 29 hold the plate 3 in position.

[0024] It should be pointed out that repositioning of the pincers 2 is made necessary and is carried out when a plate 3 has a substantial length and in order to be able to be worked by the punching machine 5 in each of its areas, including those temporary covered by the rollers 29, it becomes indispensable to have to lock in position and move a plate 3 to a number of positions on the working plane 4.

[0025] The above described device for the automatic positioning of the plate-locking pincers in a punching machine according to the present invention is susceptible to numerous modifications and variations within the scope of the following claims.

[0026] Any reference sign following technical features in any claim has been provided to increase intelligibility of the claim and shall not be construe as limiting the scope of the claim.

Claims

1. A punching machine having a punching machine framework (7), a work plane (4) for work pieces (3), a handling assembly carried by said framework (7), a graduated workpiece checking bar (6) and a pair of workpiece-locking pincers (2) brought by said handling assembly, said graduated bar (6) being mobile in, and flush with a work plane (4), at least one pair of clamping units (11) for each pincers (2), and a programme control unit (30),
   characterised in that it comprises a device (1) for automatic positioning each of the workpiece-locking pincers (2), including a slide member (9) for each pincer (2) slidably mounted on the said graduated bar (6), locking and retaining means (13) carried by said slide member (9) and locking means (10) arranged to lock and unlock said slide member (9) relatively to said graduated bar (6).

2. A punching machine as claimed in claim 1, characterised in that said locking and retaining means (13) comprises at least a lever member (16) that is articulated at a pivot pin (17) to said slide member (9) and has one end thereof facing said graduated bar (6) and arranged to engage therewith, and the other end thereof arranged to be actuated by the a respective clamping unit (11), and resilient means (20) designed to urge said other end of said lever member (16) into engagement with said graduated bar (6).

3. A punching machine as claimed in claim 2, characterised in that said end of said lever member (16) facing said graduated bar (6) terminates with at least one pawl extension (18) arranged to engage with said graduated bar (6).

4. A punching machine as claimed in claim 3, characterised in that the said slide member (9) has an access opening or recess to the said graduated bar (6) through which the or each pawl extension (18) engages with said graduated bar (6).

5. A punching machine as claimed in any claim 2 to 4, characterised in that said resilient means comprises a pre-tensioned spring (20) on support means (21, 25) carried by said slide member (9).

6. A punching machine as claimed in claim 5, characterized in that said support means (21) comprises registration means (23) arranged to adjust the reaction force of the pre-tensioned spring (20).

7. A punching machine as claimed in claim 5, characterized in that the said registration means comprises a threaded rod (24) having a control head (23) and designed to penetrate a threaded hole formed coaxially to said threaded rod (24) in a traverse member (26) carried by said slide member (9).

8. A punching machine as claimed in any claim 1 to 7, characterised in that said retaining means (13) comprises actuating means (12) having one end thereof secured to said slide member (9), at least one support arm (8) carried by, and extending from said slide member (9), a rocking lever element (27) pivoted at an intermediate portion thereof to said support arms (8) and having one end (27a) thereof shaped so as to slidably and rotatably engage with a pivot pin (29) secured to the other end of said actuating means (12), whereas its other end (27b) locates a pad member (31) facing the work plane (4) and designed to rest on and engage with a workpiece (3) to be locked in position on the work plane (4).

Drawing