EP2626174A1

EP2626174A1 - Clamping apparatus for clamping workworkpieces, particularly sheets

Info

Publication number: EP2626174A1
Application number: EP13000593.7A
Authority: EP
Inventors: Umberto Conte; Ener Varetto
Original assignee: VEP Automation Srl
Current assignee: VEP Automation Srl
Priority date: 2012-02-08
Filing date: 2013-02-06
Publication date: 2013-08-14
Anticipated expiration: 2033-02-06
Also published as: ITTO20120106A1; EP2626174B1

Abstract

An apparatus for clamping workpieces, particularly metal sheets, comprises a body (12) defining a plane of support (14, 16) for a workpiece (S) to be clamped, a hook member (20) movable between a resting position spaced from the plane of support (14, 16) and at least a clamping position of a workpiece (S), that is close to the plane of support (14, 16), and control means for controlling the movement of the hook member (20). The control means comprise a control rod (28) that is axially slidably mounted between two opposite positions, a L-shaped lever (52) that is swingably muonted with respect to the body (12) and is articulated to the hook member (20), and a connecting rod (44) the ends of which are articulated to the L-shaped lever (52) and to the control rod (28). The apparatus comprises elastic thrust means (66) adapted to cooperate with the control means to allow the coupling body (20), in its clamping position, to reach a plurality of positions close to the plane of support (14, 16) for selectively clamping workpieces (S) of a different thickness with respect to the body (12).

Description

The present invention generally refers to apparatuses for clamping workpieces, particularly sheets, which allow a workpiece to be held in a predetermined position by clamping it at a side edge thereof or at the edge of a hole bored in it, in order that a machining operation, such as welding, bending or similar, can be performed on it.
In particular, the invention relates to an apparatus of the type defined in the preamble of appended claim 1.
An apparatus of this type, known from DE-63 29 393 or from EP-1 393 861 , allows to clamp a sheet-shaped workpiece that has only a predetermined thickness.
The present invention aims at providing an apparatus of the type defined above that is able to clamp workpieces of different thickness, at least within a predefined range of thicknesses.
This object is achieved by means of an apparatus having the features mentioned in the appended claims.
In particular, by virtue of the fact that the apparatus comprises elastic thrust means adapted to cooperate with control means for controlling its hook member in order to allow the hook member, in its clamping position, to reach a plurality of positions close within a predetermined range to a plane of support, with the aim of clamping selectively, with respect to the body, workpieces of different thickness, the apparatus of the invention turns out to be very versatile since it can be used for machining workpieces of different thickness without requiring any adjustment of its geometrical characteristics.
According to a preferred feature of the invention, the elastic means consist of a spring the axis of which is arranged transverse to the axis of the control rod, which spring is adapted to apply an axial force to a connecting rod of the control means.
In this manner, the structure of the apparatus of the invention is structurally simple, and therefore also reliable in use.
According to another preferred feature of the invention, said spring is a gas spring that includes a substantially cylindrical body fixed to the body of the apparatus, and a piston slidably mounted with respect to the cylindrical body, having a head surface intended to rest against the radially outer surface of a rotatable roller associated with the end of the connecting rod that faces the side opposite to a L-shaped lever of the control means.
In this manner, the apparatus can be made particularly compact, to all advantage of the convenience and versatility of installation, and it is characterized by a great strength, so that it turns out to be suitable for heavy duty applications that involve a very high number of cycles of operation, without requiring any substantial maintenance.
Further characteristics and advantages of the invention will be more apparent from the following detailed description, provided purely by way of non-limiting example and referred to the accompanying drawings in which:

Figure 1 is a schematic sectional side elevation view of an apparatus according to the invention, in its resting configuration,
Figure 2 is a sectional perspective view of the apparatus of Figure 1, from which some elements have been removed for clarity,
Figure 3 is a view similar to Figure 1, in which the relevant apparatus in its clamping configuration of a workpiece,
Figure 4 is a view similar to Figure 2, showing the apparatus in the condition of Figure 3, and
Figure 5 is an enlarged view of a detail indicated by arrow V in Figure 3.

With reference to the figures, an apparatus according to the invention for clamping workpieces, such as sheets, is indicated 10 as a whole. The apparatus 10 comprises a body 12 provided on its upper part (with reference to the position of the apparatus shown in the figures) with a stationary plate 14 that defines a flat surface 16 intended to allow a workpiece S (Figure 5) to be clamped by the apparatus 10, to be supported. The body 12 is usually formed by two half-shells coupled to each other (only one of which is shown in the figures), which delimit an internal cavity of the body 12.
A relatively wide window 18 is formed in the plate 14, through which an upper loop end 22 of a hook member 20 extends beyond the surface 16, the hook member 20 having a lower elongated portion 24 arranged inside the cavity of the body 12. The elongated portion 24 is connected, as it will be described in a greater detail below, to control means adapted to control the movement of the hook member 20 between a resting position, in which its loop portion 22 is spaced from the surface 16, and a plurality of clamping positions, in which the loop end 22 is arranged close to the surface 16.
In the more general case, as known per se, a centering pin 26 is connected to the stationary plate 14, which pin protrudes perpendicularly above the surface 16 and has an axial through cavity in which the upper portion of the body 20, in particular its loop end 22, is arranged with a clearance, in order that it can move freely. The pin 26 can be used to engage a reference hole bored in the workpiece to be clamped by the apparatus 10.
In particular, the control means for controlling the movement of the hook member 20 comprise a control rod 28 axially and slidably mounted between two opposite end-of-stroke positions as a result of the movement of a piston 30, typically pneumatic, that is fixed to one end of the rod 28 and moves sealingly in the chamber of a cylinder 32 associated below the body 12, owing to the feeding of fluid in the cylinder 32 in such a manner to apply selectively a pressure to the opposite faces of the piston 30.
The upper end of the rod 28, on the side opposite to the piston 30, is fork-shaped and has a pair of parallel branches 34 between which a recess 36 is defined. Respective slots 38 (Figure 5) are formed in both the branches 34, which extend transversely to the axis of the rod 28 and are slidably engaged by the opposite ends of a shaft 40. A rotatable roller 42 is mounted on the shaft 40, preferably with the interposition of a roller bearing 41, which is received in the recess 36 and that will be referred in more detail below.
Also, a first fork-shaped end 43 of a connecting rod 44 is pivoted on the shaft 40, while the second end of the connecting rod 44 is articulated about a pin 46 parallel to the shaft 40, which pin is engaged in respective holes 47 formed at the ends of first arms 48 of a pair of L-shaped levers 52 equal to each other.
Each lever 52 has a second arm 50, transverse to the respective arm 48, articulated through another pin 56 parallel to the pin 46, both at respective holes 58 formed at the free end of the arms 50, and in a through hole 59 formed in an intermediate zone of the elongated portion 24 of the hook member 20.
Moreover, the pair of levers 52 is swingably mounted about a pivot pin 54 that is connected, at its opposite ends, to the two half-shells of the body 12, and that crosses both the levers 52 at respective through holes formed in an angular central portion thereof from which the arms 48 and 50 extend. Furthermore, another hole 60 is formed in the elongated portion 24 of the hook member 20, at the side opposite to the loop portion 22 with respect to the hole 59, which is crossed by another pin 62 the opposite ends of which are provided with respective rolling bearings (not shown) slidably mounted in respective arched slits 64 formed in the two half-shells of the body 12, in order to guide the movement of the hook member 20 in such a manner that its movement is always parallel to itself.
The control means for controlling the movement of the hook member 20, in particular the rod 28, the connecting rod 44 and the L-shaped lever 52, together with the relevant pins of rotation, constitute a toggle mechanism that has the function of making irreversible the clamping position of the hook member 20 with respect to movements.
Elastic thrust means are associated with the body 12 in order to allow the coupling body 20, in its clamping position, to assume a plurality of positions, within a predetermined range, that are close to the support surface 16 with the aim of allowing workpieces S of different thickness to be clamped with respect to the body 12.
Such elastic means are intended to cooperate with the aforesaid control means and consist preferably of a gas spring 66, typically loaded with nitrogen, arranged with its own axis transverse to the axis of the rod 28, in order to apply an axial thrust to the connecting rod 44 when the hook member 20 is in its clamping position.
In particular, the spring 66 comprises a cylindrical body 68 fixed in a corresponding seat formed on one side of the body 12 by a removable casing 70, on the one hand, and by means of a tooth-shaped abutment member 78, on the other side, that projects below the stationary plate 14.
The casing 70 is generally cup-shaped so as to receive a portion of the body 68 of the spring 66, and its outer surface is so shaped as to define, together with a side cavity 72 of the body 12, a rear fastening seat 74 in order to allow the apparatus 10 to be assembled on a support member (not shown), as an alternative to the assembly at a front coupling seat 76 formed in the body 12 at the side opposite to the seat 74.
A piston 80 is slidably mounted in the cylindrical body 68 of the spring 66, which piston has an head surface intended to bear against the radially outer surface of the roller 42 in order to apply an elastic compressive force to the connecting rod 44, in consideration of the sliding of the shaft 40 in the slots 38 of the fork end of the control rod 28.
Conveniently, a shield plate 82 is mounted between the stationary plate 14 and the body 12 of the apparatus, which is crossed by the coupling member 20 and which can translate with respect to the body 12 in a direction parallel to the plate 14 as a result of the movement of the member 20, in order to keep the opening 18 of the plate 14 substantially closed, so as to prevent foreign bodies from penetrating into the body cavity 12 through the opening 18.
Guide means for guiding the movement of the plate 82 are provided to enable translation of the shield plate 82 as a result of the movement of the hook member 20, which guide means consist of a pair of coaxial auxiliary pins 84 projecting from opposite portions of the plate 82 that face the coupling body 20, and engage respective rectilinear guide grooves 86 (only one of which is shown in Figures 2, 4 and 5) formed on opposite sides of the hook member 20.
In operation of the apparatus 10, the hook member 20 is initially in its resting position shown in Figures 1 and 2, in which the loop end 22 thereof is entirely contained in the axial cavity of the centering pin 26. In this position, that corresponds to the lowered configuration of the control rod 28, the engagement member 20 is raised with respect to the flat surface 16 of the stationary plate 14, and it is retracted from the window 18, while the shield plate 82 is in its retracted configuration closer to the gas spring 66.
With reference to Figures 3 to 5, as a result of raising of the control rod 28 caused by the pressure of the fluid admitted into the cylinder 32 on the side of the face of the piston 30 opposite to the body 12, the shaft 40 approaches the stationary plate 14, and the connecting rod 44 undergoes a rotation about the shaft 40 owing to the articulated connection of the connecting rod 44 to the L-shaped lever 52 that rotates about the pin 54. In this manner, the connecting rod 44 reaches a position substantially parallel to the plate 14, and the L-shaped lever 52 swings about the pin 54 until it reaches a configuration in which its arm 48 is oriented substantially vertical, while its arm 50 is almost horizontal.
In this position, in which the toggle mechanism makes the movement of the hook member 20 irreversible, the end loop 22 of the hook member 20 reaches its clamping position of a workpiece S that rests on the surface 16, in which it projects forward with respect to the cavity of the centering pin 26, that is lowered toward the surface 16 of the stationary plate 14 and is advanced in the direction opposite to the gas spring 66. By virtue of the engagement of the pins 84 in the grooves 86 of the member 20, the shield plate 82 is brought into a forward position with respect to the body 12, so as to close the window 18 of the stationary plate 14.
In this position of the hook member 20, the radially outer surface of the roller 42 that surrounds the shaft 40, contacts the head surface of the piston 80 of the gas spring 66. The force applied by the gas spring 66 on the connecting rod 44, thrusts axially the connecting rod 44 toward the engagement member 20, with the aim of pressing with strength the free end of its loop portion 22 toward the surface 16, and then on the upper surface of the workpiece S to be clamped, as a result of the rotation of the L-shaped lever 52 about the pin 54.
Since the ends of the shaft 40 can slide in the slots 38, the hook member 20 can assume a number of different clamping positions, the extreme positions of which are respectively illustrated in solid and dotted lines in Figure 5. In particular, the apparatus 10 of the invention automatically adjusts to clamping workpieces or sheet S having a different thickness generally comprised between about 7 and 10 mm, while maintaining a high clamping force on the workpiece S and by keeping the irreversible locking effect towards the movement of the hook member 20 unchanged, obtained by means of the toggle mechanism.

Claims

Clamping apparatus for clamping workpieces, particularly sheets, comprising a body (12) defining a plane (14, 16) for supporting a workpiece (S) to be clamped, a hook member (20) movable between a resting position spaced from said plane of support (14, 16), and at least one clamping position close to said plane of support (14, 16), for clamping a workpiece (S), and control means for controlling the movement of the hook member (20) between the aforesaid positions, which comprise a control rod (28) axially slidable between a first and a second position to which the aforesaid rest and clamping positions of the hook member (20) respectively correspond, a L-shaped lever (52) swingably mounted with respect to the body (12) and articulated to the hook member (20), and a connecting rod (44) the opposite ends of which are articulated to the L-shaped lever (52) and to the control rod (28), respectively, such control means including a toggle mechanism adapted to make the movement of the hook member (20) irreversible in said at least one clamping position,
characterized in that it comprises elastic thrust means (66) adapted to cooperate with the control means (28, 44, 52) in order to allow the hook member (20), in said clamping position, to reach a plurality of positions close within a predetermined range to said plane of support (14, 16), with the aim of clamping selectively, with respect to the body (12), workpieces (S) of different thickness.
Clamping apparatus according to claim 1, characterized in that said elastic means consist of a spring (66) the axis of which is arranged transverse to the axis of the control rod (28), which spring (66) is adapted to apply an axial force to said connecting rod (44).
Clamping apparatus according to claim 2, characterized in that said spring is a gas spring (66) that includes a substantially cylindrical body (68) fixed to the body (12) of the apparatus (10), and a piston (80) slidably mounted with respect to the cylindrical body (68), having a head surface intended to rest against the radially outer surface of a rotatable roller (42) associated with the end of the connecting rod (44) that faces the side opposite to said L-shaped lever (52).
Clamping apparatus according to claim 3, characterized in that said rotatable roller (42) is mounted about a shaft (40) for the articulation of said connecting rod (44) to the control rod (28), preferably with the interposition of a roller bearing (41).
Clamping apparatus according to claim 3 or 4, characterized in that the cylindrical body (68) of the gas spring (66) is fixed to a side of the body (12) of the apparatus (10) by a removable housing (70) that defines, together with a side portion (72) of the body (12) of the apparatus (10), a fastening seat (74) that allows the apparatus (10) to be assembled.
Clamping apparatus according to any one of claims 3 to 5, characterized in that the cylindrical body (68) of the gas spring (66) is locked with respect to the body (12), at the side opposite to said removable housing (70), by an abutment member (78) extending below said plane of support (14, 16).
Clamping apparatus according to any one of claims 3 to 6, characterized in that said rotatable roller (42) is arranged between the branches (34) of a fork end portion of the control rod (28), and in that the opposite ends of the shaft (40) engage respective slots (38) formed in said branches (34) transversely to the control rod (28).
Clamping apparatus according to any one of claims 1 to 7, characterized in that the hook member (20) has a loop end (22) projecting above said plane of support (14, 16) through a relatively wide opening (18), and an elongated portion (24), at the side opposite to the loop end (22), to which said L-shaped lever (52) is articulated by means of a first pin (56).
Clamping apparatus according to any one of claims 1 to 8, characterized in that the elongated portion (24) of the hook member (20) is articulated about a second pin (62) having at least one end slidably engaged in a respective arched slit (64) formed in the body (12).
Clamping apparatus according to claim 8 or 9, characterized in that the hook member (20) is associated with a shield plate (82) arranged below the plane of support (14, 16) and mounted so as to translate with respect to the body (12) along a direction parallel to the plane of support (14, 16), the shield plate (82) and the hook member (20) cooperating in order to keep said relatively wide opening (18) of the plane of support (14, 16) substantially closed, with the aim of preventing foreign members to enter within the body (10) through said wide opening (18).
Clamping apparatus according to claim 10, characterized in that translation of the shield plate (82) is guided by guide means (84, 86) associated with the shield plate (82) and with the hook member (20).
Clamping apparatus according to claim 11, characterized in that said guide means comprise at least a guide groove (86) formed on a side of the hook member (20), and a respective auxiliary pin (84) that engages said guide groove (86) and projects from a portion of the shield plate (82) facing the hook member (20).
Clamping apparatus according to any one of claims 1 to 12, characterized in that a transverse centering pin (26) is associated with the plane of support (14, 16), which pin has a cavity in which the hook member (20) extends.