EP1524080B1

EP1524080B1 - Locking device of the articulated lever type for clamping workpieces

Info

Publication number: EP1524080B1
Application number: EP04024241A
Authority: EP
Inventors: Ener Varetto; Lio Piccolo
Original assignee: VEP Automation Srl
Current assignee: VEP Automation Srl
Priority date: 2003-10-16
Filing date: 2004-10-12
Publication date: 2007-11-21
Anticipated expiration: 2024-10-12
Also published as: ES2297320T3; PL1524080T3; DE602004010217T2; DE602004010217D1; ITTO20030813A1; EP1524080A1

Description

The present invention refers to devices of the articulated lever type provided with a clamping arm which can swing in order to allow to clamp workpieces with respect to the body of the device.
More specifically, the invention refers to such a device in which the movement of the clamping arm can be controlled by driving means, typically driven by a fluid, or, as an alternative, following to the manual driving of a lever associated externally with the device.
In particular, the invention relates to a locking device of the articulated lever type for clamping workpieces, of the type defined in the preamble of annexed claim 1.
Such a device is known from DE-196 45 778 . This document describes two different embodiments of a locking device, in both of which an auxiliary shaft is rotatably arranged coaxially inside the main shaft to which the clamping arm is keyed. In the first embodiment, the auxiliary shaft is, besides rotatable, also axially movable with respect to the main shaft as a result of the axial thrust of elastic means operatively interposed between an end of the auxiliary shaft, where the manual driving lever is connected, and the main shaft. This solution requires that a slot having a branch transverse to the axis of the main shaft and a branch parallel to such an axis, is formed in the main shaft, so as to allow both the axial and transverse movement of a pin fixed to the auxiliary shaft and crossing the main shaft, which controls the movement of the service rod. In the device according to the second embodiment of this document, the auxiliary shaft can only rotate with respect to the axis of the main shaft and therefore the slot formed in the main shaft is only directed transversely to the axis thereof, since it must allow only the transverse movement of the control pin following to the rotation of the auxiliary shaft with respect to the main shaft. In the latter case, the elastic means operatively interposed between the auxiliary shaft to which the manual control lever is fixed and the main shaft, act torsionally in order to bring back the auxiliary shaft in a preset angular position with respect to the main shaft, when the auxiliary shaft undergoes a rotation caused by the driving of the control lever.
Both these solutions have a general structure relatively complex, which contributes to make the operation of the device delicate. In particular, the maximum weights which can be applied manually to the driving lever must be limited by using a lever of a reduced length in order to avoid that loads too much high may damage the inner members of the device, such as the control pin.
Moreover, the side hindrance of the two locking devices of this document is high, because the auxiliary shaft must project axially from both the ends of the main shaft in order to allow to arrange the elastic means on these projecting ends, so that the manual driving lever can be mounted indifferently at one of the two sides of the device, allowing therefore its installation according to two possible different configurations of use. In this manner, a portion of the auxiliary shaft always extends beyond the clamping lever at the side of the device opposite to that to which the lever is associated, which constitutes an obstacle able to limit the capability of the device to be installed.
In order to overcome the above mentioned disadvantages of the devices according to the prior art, the subject of the invention is a device having the features set forth in the appended claims.
In particular, a device according to the invention has a simpler inner structure and its members are more rugged than those of the similar known devices, on the same terms of external dimensions of the device, so that it allows higher loads to be applied by the manual control lever without any risk to damage its members. Moreover, in the device according to the invention, the main shaft and the auxiliary shaft have substantially the same axial extension so that the device does not have any portion projecting sideways beyond the clamping arm at the side opposite to that to which the manual driving lever is associated, which improves the functional capacity and the operational flexibility of use and installation of the device.
Further characteristics and advantages of the invention will become more clearly evident from the reading of the detailed description which follows, given purely by way of a non limiting example and referred to the attached drawings, in which:

figure 1 is a side elevational view of a clamping device according to the invention,
figure 2 is a perspective view of the device of figure 1 in an open condition, in a first operational step following to the driving of the manual control lever,
figure 3 is a view similar to that of figure 2, in another operational step following to the driving of the lever,
figure 4 is an elevational view sectioned along line IV-IV of figure 3,
figure 5 is an elevational view sectioned along line V-V of figure 3,
figure 6 is an enlarged perspective view of a detail indicated by arrow VI of figure 4, and
figure 7 is an exploded perspective view of a detail indicated by arrow VII of figure 4.

With reference to the figures, a locking device of the articulated lever type, which can be used for clamping workpieces, is indicated 1 as a whole. A fork shaped clamping arm 12 is associated to the body 2 of the device 1, and is keyed to square sectioned ends 16a of a main shaft 16 having an axis A, by means of U-shaped locking members 14, 14a. In particular, the axial extension of the shaft 16 is substantially equal to the width of the arm 12.
The shaft 16 has a control appendage 18 having the function of a crank and projecting radially from a central zone thereof, which is connected by means of an articulation pin with a pair of connecting rods 23. The connecting rods 23 are in turn connected by means of another articulation pin to the end of a service rod 20, which is slidably mounted inside the body 2. The articulated joint serving to connect the rod 20, which comprises the pair of connecting rods 23 and the control appendage 18, forms an articulated toggle joint of the device 1, indicated as a whole by the reference numeral 22, which will be considered in greater detail in the following.
The sliding movement of the rod 20 can be controlled by automatic driving means which, in the most common case, comprise a fluid-driven double acting cylinder 4 (figure 1), typically of the pneumatic type, which is fixed at the bottom of the body 2. In this case, with reference to figures 2 and 3, during the clamping movement of the arm 12, the rod 20 initially performs a raising movement indicated by arrow B of figure 2, until the connecting rods 23 of the toggle joint 22 reach a position perpendicular to the rod 20. In this position, which corresponds to the maximum effort of the toggle joint 22, a condition of unstable equilibrium is reached, which is called "dead point" condition because a further sliding of the rod 20 beyond this point does not cause a further rotation of the clamping arm 12. A further axial movement of the rod 20 in the direction indicated by arrow C of figure 3, also of a very short distance, brings the toggle joint 22 in a condition in which the movement of the arm 12 becomes irreversible, since it cannot happen unless the rod 20 moves in the direction opposite to that indicated by arrows B and C.
In order to control manually the movement of the arm 12, in particular the reaching of its clamping position, the device 1 is also provided with a manual driving lever 30. The lever 30 can be associated indifferently to each one of the two sides of the body 2, so as to make easy the installation of the device 1 in any configuration required for its use.
In order to allow the connection and operation of the lever 30, an auxiliary shaft 24 is arranged coaxially inside the main shaft 16, which auxiliary shaft is mounted so as to be able only to rotate with respect to the shaft 16. A radial control pin 26 extending centrally from the auxiliary shaft 24 crosses a slit 28 of the main shaft 16, which slit is directed only transverse to the axis A.
Conveniently, the auxiliary shaft 24 has an axial extension which is substantially the same of the main shaft 16 and the side hindrance of the clamping arm 12, so that it does not project sideways from the side flanks of the arm 12.
The pin 26 has a free end 26a, for example having an hemispheric shape, which is adapted to engage a corresponding hollow seat 27, formed at a side of rod 20, when the latter is close to said "dead point" position, in order to allow to move axially the rod 20 in both the sliding directions thereof as a result of the driving of the lever 30. In particular, the end 26a of the pin 26 engages the seat 27 at least in the range of movements of the rod 20 which are comprised between a first position slightly preceding the attainment of the "dead point" condition of the toggle joint 22, and a second position subsequent to such a "dead point" condition.
The control pin 26 has length such that it cannot interfere with the members of the toggle joint unit 22, and in particular with the connecting rods 23, but which allows only the engagement thereof in the seat 27 of the rod 20. In this manner, the small length of the pin 26 makes it relatively rugged and deteriorations of the toggle joint unit 22 can be avoided in the case of application of heavy loads to the lever 30, since the pin 26 does not interfere with the unit 22.
Respective hollow seats 24a, having a hexagonal cross-section, are formed at the opposite ends of the auxiliary shaft 24. Each of the seats 24a is adapted to receive a corresponding hexagonal pin 44 extending axially from a movable member 34, which has a generally cylindrical shape. The pin 44 and the respective seat 24a in which it is received, constitute a prismatic fit allowing to fasten each other into rotation the member 34 and the auxiliary shaft 24.
A series of threaded radial holes 30a, for example four, are formed on the external sidewall of the movable member 34 in order to allow to fix a corresponding threaded end of the manual driving lever 30. The several holes 30a allow the arrangement of the lever 30 in the more favourable position for its driving, both in the case the lever 30 is associated to the right side or to the left side of the device 1, and in the case the device 1 is installed with its axis vertical or horizontal.
The member 34 is rotatably supported inside a substantially cylindrical and cage-shaped case 36 which has an integral connecting portion 14a quite similar to the U-shaped locking member 14, to allow the case 36 to be fixed to one of the branches of the arm 12, at one of the ends 16a of the shaft 16, in order to fasten it into rotation with the shaft 16.
The case 36 has a bottom wall 41 provided with a central hole 46 intended to be crossed by the hexagonal pin 44, in which a series of radial grooves 42 are formed, for example four, the shape of which is a little more extended than a semi-cylinder (see figure 7), in each of which a respective pin 40 is forcedly inserted. In this manner, a portion of the outside surface of each pin 40 project axially from the bottom wall 41, so that a rib is formed, which extends towards the member 34. In its turn, the member 34 has, on its face opposite to the wall 41, a series of radial grooves 38 intended to be engaged by the portions of the pins 40 projecting axially from the face 41.
Preferably, the number of grooves 38 is twice as much as that of the pins 40, namely there are eight grooves 38 when four pins 40 are provided. The pins 40 and the respective groove pairs 38 constitute reference formations intended to be mutually engaged following to the rotation of the member 34 with respect to the case 36, and therefore to the main shaft 16, as a result of the handling of the lever 30.
Each pair of grooves 38 is made in such a manner that one of the grooves of each pair of adjacent grooves 38 engages a respective pin 40 in a position of the lever 30 which corresponds to a first angular position of the pin 26 preceding the attainment of the "dead point" condition of the toggle joint 22, while the other groove of the same pair of grooves 38 engages the same pin 40 when the lever 30 is in a position which corresponds to a second angular position beyond the "dead point", in which the movement of the clamping arm 12 is made irreversible.
A series of slots transverse to the axis A, the number of which corresponds to that of the threaded holes of the member 34, are formed in the sidewall of the case 36 in order to allow the lever 30 to pass through the case 36 in the various assembly positions of the lever 30. The ends 43 of each of these slots constitute shoulder surfaces for limiting the angular travel of the lever 30 with respect to the case 36, and therefore with respect to the main shaft 16.
The case 36, at the side opposite to the bottom wall 41, is closed by means of a generally disc-shaped external cover 48 which has a cylindrical axial pin 50 on which a plurality of Belleville springs are inserted coaxially in order to constitute a spring pack 32. The spring pack 32 bears at one side on the inner face of the cover 48 and, at the opposite side, on the edge of a collar 52a formed close to the bottom of an axial hole 52 of the member 34, within which the pin 50 is axially movable. In this manner, the spring pack 32, which is operatively interposed between the case 36 fixed to the main shaft 16 and the movable member 34 connected into rotation with the auxiliary shaft 24, urges the movable member 34 towards the auxiliary shaft 24, in the direction of the axis of rotation A.
Corresponding threads 54 and 56 are formed on the peripheral edge of the cover 48 and inside the case 36, at the side opposite to the bottom wall 41, which are intended to engage each other in order to allow to connect the cover 48 to the case 36, so as to close the movable member 34 within the case 36. Moreover, the cover 48 is provided with seats 49 on its outside face, in order to control its rotation by means of a tool (not shown) during the closing step of the case 36 and in order to change the distance between the cover 48 and the member 34 with the aim of adjusting the preloading of the spring pack 32.
In the manual operation of the device 1, the application to the lever 30 of a rotation indicated by arrow D in figure 2, causes the raising of the rod 20 as a result of the rotation of the main shaft 16 about the axis A and of the simultaneous rotation of the auxiliary shaft 24 together with the respective pin 26. When the rod 20 reaches a position close to that shown in figure 3, the toggle joint unit 22 is in a configuration which slightly precedes the attainment of the "dead point", and a first groove of each pair of grooves 38 of the movable member 34 is engaged by a respective pin 40. In this condition, the end 26a of the pin 26 engages the seat 27 of the rod 20. Continuing with the angular movement of the lever 30, as indicated by arrow E of figure 3, the angular movement of the member 34 gets free from that of the case 34 and of the main shaft 16, whereby only the auxiliary shaft 24 rotates so that the pin 26 slides within the slit 28 of the shaft 16 until it reaches the position shown in dashed lines of figure 3, and the rod 20 is moved in order to bring the toggle joint unit 22 beyond the "dead point". In this configuration, in which the movement of the arm 12 is irreversible, the second groove of each pair of grooves 38 is engaged by the respective pin 40. When the pin 40 passes between one and the other groove of each pair of grooves 38, the spring pack 32 undergoes a compressive stress, while in the condition in which the pins 40 engage a respective groove 38, the spring pack 32 expands so that it returns in a normal working condition in which it exerts an axial thrust determined by the preloading of the pack 32 as a result of the angular position of the cover 48 with respect to the case 36.

Claims

Locking device of the articulated lever type for clamping workpieces, including a swingable clamping arm (12) mounted on a main shaft (16) which is rotatable with respect to the body (2) of the device (1) about an axis of rotation (A), the main shaft (16) being able to be controlled into rotation by the axial sliding of a service rod (20) through a toggle joint unit (22) which is adapted to reach a position beyond a dead point in which the movement of the clamping arm (12) is irreversible, a rotatable auxiliary shaft (24) being arranged coaxially inside the main shaft (16), from which extends a control pin (26) crossing a slit (28) of the main shaft (16), which is directed only transverse to it, said pin (26) being adapted to cooperate with the service rod (20) in order to cause an axial sliding thereof, the device (1) comprising a manual driving lever (30) which can be selectively fixed to one of the ends of the auxiliary shaft (24) in order to allow to control manually the swing of the clamping arm (12), an elastic member (32) being operatively interposed between the main shaft (16) and the auxiliary shaft (24),
characterized in that the elastic member (32) acts along the direction of said axis of rotation (A) so as to urge axially towards the auxiliary shaft (24) an axially movable member (34) which is fastened into rotation to the auxiliary shaft (24) and to which the manual driving lever (30) is connected, said movable member (34) being supported rotatably by a case (36) which can be selectively fixed to an end (16a) of the main shaft (16), corresponding reference formations (38, 40) being formed on opposite faces of the movable member (34) and of the case (36), which formations axially extend with respect to said axis of rotation (A) and are intended to engage each other when the movable member (34), together with the respective manual driving lever (30), reaches at least an angular position close to said dead point position of the toggle joint (22), with respect to the main shaft (16).
Device according to claim 1, characterized in that said reference formations (38, 40) are adapted to define both a first position preceding the attainment of said dead point of the toggle joint (22), and a second position beyond said dead point in which the movement of the clamping arm (12) is made irreversible.
Device according to claim 1 or 2, characterized in that the reference formations include at least a radial rib (40) formed on an axial face of the case (36) and a corresponding groove (38) formed on an axial face of the movable member (34) which is opposite to said axial face of the case (36), or viceversa.
Device according to anyone of claims 1 to 3, characterized in that said radial rib consists of a pin (40) received in a radial groove (38) of the case (36).
Device according to anyone of claims 1 to 4, characterized in that the movable member (34) is fastened into rotation to an end of the auxiliary shaft (24) by means of a prismatic fit (44, 24a).
Device according to claim 5, characterized in that said prismatic fit comprises a pin having an hexagonal cross-section (44) which projects axially from the movable member (34) and engages a corresponding seat (24a) formed at a respective end of the auxiliary shaft (24).
Device according to anyone of claims 1 to 6, characterized in that said elastic member (32) is interposed between the movable member (34) and an external cover (48) of said case (36).
Device according to claim 7, characterized in that the cover (48) is connected to the case (36) by means of a threaded connection (54, 56) so that the amount of the thrust force of the elastic member (32) can be adjusted as a result of the rotation of the cover (48) about said axis of rotation (A) and with respect to the case (36).
Device according to anyone of claims 1 to 8, characterized in that the elastic member includes a pack (32) of coaxial Belleville springs.
Device according to anyone of claims 1 to 9, characterized in that the case (36) defines shoulders (43) for the angular movement of the manual driving lever (30) and of the movable member (34), with respect to the main shaft (16).
Device according to anyone of claims 1 to 10, characterized in that the free end of the control pin (26) is adapted to engage a corresponding seat (27) formed on a side of the service rod (20), in order to cause the axial sliding of the rod (20) in both directions, when it is close to said first and second position.
Device according to claim 11, characterized in that the toggle joint unit (22) includes at least a connecting rod (23) for the articulated connection of an end of the service rod (20), and a control appendage (18) projecting from the main shaft (16), in which the control pin (26) has such an extension that it cannot interfere with said at least a connecting rod (23).
Device according to anyone of claims 1 to 12, characterized in that the auxiliary shaft (24) has an axial extension which is substantially equal to that of the main shaft (16).
Device according to anyone of claims 1 to 13, characterized in that the auxiliary shaft (24) has an axial extension which is substantially equal to the side hindrance of the clamping arm (12).