EP0938939A2

EP0938939A2 - Improved metal strip feeder

Info

Publication number: EP0938939A2
Application number: EP99100700A
Authority: EP
Inventors: Sergio Dallan
Original assignee: Dallan SRL
Current assignee: Dallan SpA
Priority date: 1998-01-30
Filing date: 1999-01-15
Publication date: 1999-09-01
Anticipated expiration: 2019-01-15
Also published as: PT938939E; ES2223148T3; SI0938939T1; IT1306461B1; ITVE980006A1; ATE270931T1; EP0938939A3; ITVE980006A0; DK0938939T3; DE69918581T2; DE69918581D1; EP0938939B1

Abstract

An improved metal strip (28) feeder, of the type comprising a pair of grippers (18,18'), each formed form a pair of jaws (20,20') positioned transversely to the longitudinal axis of the feeder and extending substantially along the entire width of this latter, said grippers being operated in a mutually synchronized manner in the sense that while one gripper is activated and advances towards the machine to be fed, the other gripper is deactivated and moves in the opposite direction, characterised in that at least one of the two jaws (20,20') of each gripper comprises a plurality of appendices (24) positioned along the entire jaw and projecting from its gripping surface to an adjustable extent.

Description

This invention relates to an improved metal strip feeder.
Feeders are known for presses and machines in general which mechanically operate on a metal strip fed between the tools of said machines.
EP-B1-0737115 describes a feeder provided with two pairs of grippers movable with reciprocating movement parallel to the longitudinal axis of the strip and operated synchronously such that when a gripper grips the strip it is driven in the direction required for strip advancement, whereas when that gripper is not activated it is driven in the opposite direction. It is clear that by suitably synchronizing the working movement with the advancing movement of the two grippers, correct unidirectional feed of the strip can be achieved towards the machine to be fed.
A known type of such feeders uses grippers with pairs of jaws extending along the entire width of the feeder. They have proved particularly useful because of their adaptability to metal strip practically of any width, but at the same time they have shown to be limited in their use with small-width and small- thickness metal strip, especially if its position is displaced from the longitudinal axis of the feeder.
In this respect, in the case of metal strip of small width, when the two jaws of each gripper engage it, the small clamping surface makes the grip uncertain and can result in uncertain locking, and hence undesirable movement of the strip relative to the gripper which clamps it, with obvious uncertainty of position of the strip relative to the machine to be fed, and possible inaccuracies in the resultant work. In addition, if the longitudinal axis of the strip does not coincide with the longitudinal axis of the feeder, the strip will not be centered about the two jaws of each gripper, which can result in loss of parallelism between said jaws, with highlighting of this phenomenon.
According to the invention these drawbacks are eliminated by an improved metal strip feeder as described in claim 1.
The invention is further clarified hereinafter with reference to the accompanying drawings, on which:
Figure 1 is a plan view of an improved feeder according to the invention, and
Figure 2 is a longitudinal vertical section therethrough on the line II-II of Figure 1.
As can be seen from the figures, the feeder according to the invention comprises a bed indicated overall by 2, on which there are mounted two longitudinal rails 4,4' for guiding two slides 6,6' on which two carriages 8,8' are mounted.
Each of the carriages 8,8' is provided with a threaded bush 10,10' in which there engages a longitudinal rod 12,12' provided along about one half of its length with a thread in one direction, and along the other half with a thread in the opposite direction.
The threaded rod 12 is supported by the bed 2 via a pair of supports 14,14' applied to shoulders 15,15', the support 14 supporting its right end, whereas its left end extends beyond the shoulder 15' to be coupled to the output shaft of a direct current electric motor 16, also mounted on the bed 2.
On each carriage 8,8' there is mounted a gripper 18,18' extending substantially along the entire width of the bed 2. Each gripper 18,18' comprises a fixed lower jaw rigid with the corresponding carriage 8,8', and a movable upper jaw 20,20' driven relative to the corresponding fixed jaw by a pair of pneumatic actuators 22 of vertical axis.
The movable jaw 20,20' of each gripper 18,18' comprises a plurality of aligned apertures housing corresponding grub screws 24, adjustable individually in their axial position relative to the seat housing them and consequently adjustable in the amount by which they project from the clamping surface of the jaw. This adjustment can be achieved for example by rotating the grub screw 24 and fixing it in the attained position by a locking nut 26.
The end of each screw 24 is pointed to facilitate, as described hereinafter, its penetration into the metal strip 28 to be fed a machine which is positioned downstream of the feeder according to the invention, and is not further described as it does not form part of this invention.
External to the two shoulders 15 but still forming part of the bed 2, there are provided two centering sections 30,30' for the strip 28. Each centering section comprises a pair of transverse guides 32,32', ie positioned perpendicular to the guides 4,4'. They guide two slides 34,34' engaged on respective threaded rods 36,36', which are coupled to the corresponding threaded rods of the other centering section by sprocket wheels 38 connected together by pairs of chains 40,40' extending along the longitudinal edges of the bed 2 and covered together with the sprocket wheels 38 by a guard 42,42'.
The threaded rods 36,36' relative to one of the two centering sections 30,30' extend beyond the respective sprocket wheel 38 and can be removably coupled to a handwheel 44,44' for manual operation.
In each slide 34 there is provided a longitudinal groove 44 facing the groove 44' of the facing slide 34' so as to cooperate with this in engaging the longitudinal edges of the strip and in guiding it in its advancement.
At the upstream end of the feeder, defined with reference to the direction of advancement of the strip 28, indicated by the arrow 46 on the drawings, there is provided a traditional straightening station for the strip 28, ie a station comprising a pair of lower transverse rollers 48 on which the strip 28 rests, and an upper transverse roller 50 which presses the strip against the lower rollers with adjustable intereference, to remove any curvature which the strip possesses if originating from the unwinding of a coil.
At that end of the feeder closer to the machine fed therewith there is provided a safety device, consisting of a lower plate 52 on which the strip 28 slides, and an upper plate 54 which is hinged to the bed 2 along its rear transverse edge and can hence pass from a position parallel to the lower plate 52 to a raised position, shown by dashed in Figure 2.
When said upper plate 54 is in its lowered position there is interaction between a sensor 56 mounted on the bed 2, and a sensor-operating activator 58 rigid with the bed, whereas when said plate 54 is in its raised position this interaction is lacking and the sensor is deactivated.
The feeder of the invention operates as follows:
when the characteristics of the strip to be worked are known, and in particular its width, its thickness and its transverse position relative to the bed 2, correct feed to the downstream machine is achieved by individually operating the two handwheels 44 to position the slides 34,34' in accordance with the correct position of the strip 28.
In this respect, operating the handwheel 44 directly rotates the threaded rod 36, causing the slide 34 of the centering section 30' to traverse along the guides 32,32', while at the same time, by virtue of the connection between the sprocket wheels 38 and chain 40, causing the threaded rod 36 of the section 30 to rotate with simultaneous operation of its slide 34 in the same direction, so that the two slides 34 of the two centering sections 30,30' move simultaneously in the same direction.
The same operation is repeated with the handwheel 44a, on termination of which the slides 34' of the two sections 30,30' are arranged such as to ensure correct positioning of the strip 28 with which the downstream machine is to be fed.
As stated, this adjustment is made manually, and is facilitated if each of the two threaded rods 36,36' rigid with the handwheels 44,44' has associated with it a counter for counting the revolutions through which the rod has passed. The threaded rods 36,36' can also be associated with stepping motors instead of with handwheels, so as to be able to undergo motorized operation controlled by a computer.
After the position of the strip 28 in the transverse direction relative to the bed 2 has been correctly defined, and likewise its position relative to the grippers 18,18', the grub screws 24 are adjusted. During this stage the grub screws of those jaw portions 20 directly involved in gripping the strip 28 are made to project to an extent sufficient to ensure that the points of the grub screws penetrate into the strip 28 sufficiently to securely clamp it. At the same time the grub screws of those jaw portions 20 not involved in gripping the strip are made to project to a greater extent to compensate for the strip thickness and to rest directly on the underlying jaw, to in all cases ensure perfect parallelism between the two jaws of each gripper independently of the position of the strip 28.
Having made this adjustment, the feeder is ready to operate by the synchronized powering of the actuators of the two grippers 18,18'and of the motor 16 which drives the threaded rod 12, in accordance with that described for example in the aforesaid EP-B1-0737115.
With correct operation, the advancement of the strip 28 proceeds on the basis of the operating sequence of the machine positioned downstream of the feeder: the strip 28 is made to advance gradually as and when the machine requires it for working, in which case the upper plate 54 rests on the strip 28 parallel to the lower plate 52 and the sensor 56. It remains constantly activated by the activator 58 and provides the enabling signal for line operation.
If however for any reason the downstream machine fails to operate correctly such as to cause a hold-up of the strip within said machine, the thrust which the strip undergoes by virtue of its advancement by the feeder causes it to arch in the only direction possible, ie upwards. This arching causes the plate 54 to rise, with disengagement between the activator 58 and the sensor 56.
This latter, no longer activated, generates an alarm signal, which can be used to halt the line of operation and to feed a corresponding indication to the personnel responsible for supervising the line.
From the aforegoing it is apparent that the improved feeder of the invention is particularly advantageous, in that:

it enables metal strip of any width and thickness to be guided for correct feeding to any machine,
it enables this adjustment to be made quickly, easily and repetitively, and in particular by a computer,
it enables accidental hold-up in strip advancement to be noted in good time, to immediately halt the operation of the working line and to feed suitable signals to the supervisory personnel.

Claims

An improved metal strip (28) feeder, of the type comprising a pair of grippers (18,18'), each formed form a pair of jaws (20,20') positioned transversely to the longitudinal axis of the feeder and extending substantially along the entire width of this latter, said grippers being operated in a mutually synchronized manner in the sense that while one gripper is activated and advances towards the machine to be fed, the other gripper is deactivated and moves in the opposite direction, characterised in that at least one of the two jaws (20,20') of each gripper comprises a plurality of appendices (24) positioned along the entire jaw and projecting from its gripping surface to an adjustable extent.
A feeder as claimed in claim 1, characterised in that said appendices consist of grub screws (24).
A feeder as claimed in claim 2, characterised in that the end of each grub screw is pointed.
A feeder as claimed in claim 2, characterised in that each grub screw (24) is provided with a locking nut (26) for its locking in the desired position.
A feeder as claimed in claim 1, characterised by also comprising two pairs of facing slides (34,34') positioned externally to the grippers (18,18'), said slides comprising a groove (44,44') for engaging the edges of the strip (28), at least one slide of each pair of slides being movable relative to the other slide.
A feeder as claimed in claim 5, characterised in that each pair of slides (34,34') is mounted on a pair of guides (32,32') positioned perpendicular to the direction of advancement of the strip.
A feeder as claimed in claim 5, characterised in that each pair of slides (34,34') is engaged on corresponding threaded rods (36,36').
A feeder as claimed in claim 7, characterised in that the threaded rods (36,36') are provided with sprocket wheels (38) connected together by pairs of chains (40,40').
A feeder as claimed in claim 8, characterised in that the threaded rods (36,36') are removably coupled to a handwheel (44,44') for manual operation.
A feeder as claimed in claim 8, characterised in that the threaded rods are associated with stepping motors.
A feeder as claimed in claim 1, characterised by comprising in correspondence with its exit end a flap plate (54) hinged to the feeder bed (2) and substantially in contact with the metal strip during its advancement, said flap plate being rotatable as a result of arching of the strip, to activate a member (56) for indicating this irregularity.
A feeder as claimed in claim 11, characterised in that the flap plate (54) comprises an activator (58) for the indicating member, said activator and said member mutually interacting when the plate is horizontal.