WO2009149717A1

WO2009149717A1 - A clamping tool

Info

Publication number: WO2009149717A1
Application number: PCT/DK2009/050127
Authority: WO
Inventors: Karsten Bent Kofod; Søren P. SØGAARD
Original assignee: Ss Holding Aps
Priority date: 2008-06-11
Filing date: 2009-06-11
Publication date: 2009-12-17

Abstract

A clamping tool (1) for clamping a workpiece (2) to a support (3a, 3b, 3c), comprising a base (6), a clamping arm (9), an activation arm (10) pivotally connected to said base (6) for moving said clamping arm (9) from a releasing to a locking end position, and a first and a second arm (14, 10a) forming a toggle joint (13) arranged to reach a dead point position when said activation arm (9) is moved from said releasing to said locking end position. The clamping tool (1) is characterized in that said first and second arms (14, 10a) of said toggle joint (13) in said releasing endposition form an angle below 180°, preferably below 90°, with each other, a point formed by said angled first and second arms (14, 10a) being directed substantially towards said clamping arm (9).

Description

A clamping tool

The present invention relates to a clamping tool for clamping a workpiece to a support, comprising a base, a clamping arm, an activa- tion arm pivotally connected to said base for moving said clamping arm between a releasing end position and a locking end position, and a first and a second arm forming a toggle joint arranged to reach a dead point position when said activation arm is moved from said releasing to said locking end position. Such clamping tools are applied to clamp a number of work- pieces to a support or fixture for welding together the work pieces to form a welded object such as a container or the like.

Several different designs of such clamping tools are known from the prior art, of which most are able to exert pressure to a workpiece in one predefined direction. However, in many cases it is necessary to clamp a workpiece in two directions, e.g. both a vertical and a horizontal direction, in order to obtain the accuracy that is often required of such welded objects. Thus, at least two kinds of clamping tools have to be used to clamp each workpiece to the support; one set for clamping the workpiece in one direction and a second set for clamping the workpiece in a second direction.

EP 1159110 B suggests a solution to this problem by providing a clamping tool of the kind mentioned in the opening paragraph in which the clamping arm via two perpendicularly positioned contact surfaces clamps a workpiece both in a direction downwards and in a direction away from the base. However, it is often necessary to, instead, clamp a workpiece both in a direction downwards and in a direction towards the base. This is not possible with the clamping tool of EP 1159110 B. Thus, in these cases two different kinds of conventional clamping tools are still used today to clamp the workpiece to the support.

In view of the above the object of the invention is to provide a clamping tool of the kind mentioned in the opening paragraph, which is able to clamp a workpiece both in a direction downwards and in a direction towards the base. To meet this object the clamping tool according to the invention is characterized in that said first and second arms of said toggle joint in said releasing end position form an angle below 180°, preferably below

90°, with each other, a point formed by said angled first and second arms being directed substantially towards said clamping arm.

By means of this arrangement of the clamping tool a first contact surface on or of the clamping arm can act on a workpiece with a pressure in a downwards direction while a second contact surface on or of the clamping arm simultaneously can act on the same workpiece in a direction towards the base.

A number of workpieces, which are to be welded together to form a welded object, can hereby be clamped securely and precisely to the support, both in a downwards direction and in a direction towards the base and by means of half as many clamping tools as are required today using conventional clamping tools. Thereby, the task of clamping the workpieces and subsequently removing the finished, welded object from the fixture is facilitated and made less expensive, and the overall costs of producing the welded object are reduced.

In a preferred embodiment of the clamping tool according to the invention, said first arm of said toggle joint is, via a first pivot, connected pivotally to a first end of an intermediate arm, a second end of said intermediate arm being pivotally connected via a second pivot to said clamping arm, said intermediate arm further being connected pivotally to said base via a base pivot positioned between said ends of said intermediate arm. Hereby, an effective clamping tool with a strong clamping force in said two directions is provided. In a preferred development of this embodiment said base pivot is in the releasing end position of said clamping tool positioned eccentrically, i.e. displaced from an imaginary straight line connecting said first and second pivots, in a direction away from said clamping arm, said intermediate arm preferably being V-shaped, said base pivot being positioned at a point of said V- shape. Positioning the base pivot eccentrically in this direction provides a larger angle of movement of the clamping arm, i.e. the arm can be lifted or rotated more towards an upward direction. This makes it easier to remove the welded object from the support after completing the welding operation because the welded object can be removed in the upwards direction without releasing the clamping tool from its position which is fixed in relation to the welding fixture. Also, the V-shape ensures that the intermediate arm does not interfere with and is not pushed into the activation arm or other parts during movement between its two end positions. In another development said second pivot connects said intermediate arm to a first end of said clamping arm, said clamping tool further comprising a rocking arm, which at one end is pivotally connected to said base via a pivot and at another end is pivotally connected to said clamping arm via a pivot positioned between said first end and a second end of said clamping arm. This provides for improved control and movement of the clamping arm.

In another preferred embodiment said activation arm is con- nected pivotally to said first arm of said toggle joint via a pivot positioned at a first end of said activation arm, and said activation arm is pivotally connected to said base via a pivot positioned between said first end and a second end of said activation arm, said pivots defining said second arm. In another preferred embodiment said toggle joint has just passed said dead point position in said locking end position, said first and second arms of said toggle joint in said locking end position forming an angle preferably between 174 and 179°, preferably between 176° and 178°. Hereby, a suitably large force must be overcome to move the clamping tool out of the locking end position towards the releasing end position.

In another preferred embodiment a stop, preferably a stop plate, is provided on said base, said toggle joint abutting said stop in said locking end position. This allows for a precise adjustment, during manufacture, of the position of an angle formed by said first and second arms of said toggle joint in the locking end position of the clamping tool.

In another preferred embodiment said base comprises a foot, which extends into a housing, which housing in said locking end position encloses said toggle joint and preferably an intermediate arm. Hereby, a good fixation of the clamping tool to a support can be achieved while the toggle joint and preferably an intermediate arm are protected from dirt and the like.

In another preferred embodiment said clamping arm at said second end comprises a first contact face positioned to extend substantially in parallel with said clamping arm and a second contact face positioned to extend substantially perpendicularly with said clamping arm. The workpiece can hereby be clamped securely and precisely in the fixture both in a downwards direction and in a direction towards the base. The invention will be explained in greater detail below, describing exemplary embodiments with reference to the drawing, in which

Fig. 1 is a side view of a clamping tool according to the invention in a releasing end position, and

Fig. 2 is a side view of the clamping tool of Fig. 1 in a locking end position.

Referring to Figs 1 and 2 a clamping tool generally designated by the reference numeral 1 is to serve for clamping a workpiece 2 of a welded object to a fixture or support 3. The support 3 comprises a horizontal support part 3a, a vertical support part 3b and a horizontal base support part 3c.

The clamping tool 1 comprises a base 6 with a foot 6b in the form of wings for securing the base 6, and hereby the clamping tool 1, to the support 3 by means of for example screws or welds (not shown). The foot 6b is formed integrally with and extends into a housing 6a of the base 6. Also, the clamping tool 1 comprises a clamping arm 9, an activation arm 10 with a handle 11, a rocking arm 12, an intermediate V- shaped arm 17, and a toggle joint 13 having a first arm 14 and a second arm 10a, the second arm 10a forming part of the activation arm 10.

The activation arm 10 is pivotally connected to the base 6 for moving the clamping arm 9 between the two end positions, i.e. between a releasing end position as shown in Fig. 1 and a locking end position as shown in Fig. 2.

Each of the housing 6a, clamping arm 9, activation arm 10, rocking arm 12, intermediate arm 17, and first arm 14 comprises two plane-parallel, symmetrical metal plates of similar thickness x, which are positioned at one of four different distances from each other to allow for the individual parts to move past each other during movement between the two end positions of the clamping tool 1. The symmetry planes of the parts 6a, 9, 10, 12, 17, 14 are coincident.

To explain the individual relationships between the parts 6a, 9, 10, 12, 17, 14 in the depth direction of Figs 1 and 2, in the following each of these parts are positioned in one of four categories: In category a the plate distance is 0, in category b the distance is 2x, in category c the distance is 4x, and in category d the distance is 6x. Thus, two parts falling within different categories a-d are able to move past each other during movement between the two end positions of the clamping tool 1. Keeping this in mind, the clamping arm 9 and the first arm 14 belong to category a; the activation arm 10 and the intermediate arm 17 belong to category b; the housing 6a belongs to category c; and the rocking arm

12 belongs to category d. In other words, the clamping arm 9 and the first arm 14 and the activation arm 10 and the intermediate arm 17, respectively, are the only ones of the categorized parts not able to move past each other. Thus, the intermediate arm 17 is V-shaped with a cut- out to ensure that the toggle joint 13 does not intersect the intermediate arm 17 when moving between the two end positions of the clamping tool 1.

In the locking end position of Fig. 2 the housing 6a encloses the first arm 14, the intermediate arm 17 and parts of the activation arm 10 and the clamping arm 9.

The activation arm 10 is pivotally connected to the base 6 via a pivot 21 positioned between the first end and a second end of the activation arm 10. Furthermore, the activation arm 10 is connected pivotally to the first arm 14 of the toggle joint 13 via a pivot 24 positioned at a first end of the activation arm 10, the second arm 10a of the toggle joint

13 being defined by the pivots 21, 24.

The first arm 14 of the toggle joint 13 is, via a first pivot 17a, connected pivotally to a first end of the intermediate V-shaped arm 17. A second end of the intermediate arm 17 is pivotally connected via a sec- ond pivot 17b to a first end of the clamping arm 9.

The intermediate arm 17 is also pivotally connected to the base 6 via a base pivot 17c positioned between the ends of the intermediate arm 17. The base pivot 17c is positioned eccentrically, i.e. displaced from an imaginary straight line L (Fig. 1) connecting the pivots 17a, 17b, in a direction away from the clamping arm 9, i.e. a downward direction in the open position shown in Fig. 1. Thus, the base pivot 17c is positioned at a point of the V-shape, i.e. an intersection between two legs of the V-shape, of the intermediate arm 17. This provides a larger angle of movement of the clamping arm 9, i.e. the arm 9 can be lifted more towards a vertical direction before it reaches the releasing end position, cf. Fig. 1. As can be seen in Fig. 1, this makes it possible to remove a resulting welded object from the support in the vertical direction without releasing the clamping tool 1 from the base support part 3c. The rocking arm 12 is at one end pivotally connected to the base 6 via a pivot 22 and at another end pivotally connected to the clamping arm 9 via a pivot 23 positioned between the first and a second end of the clamping arm 9. All pivots 17a-17c and 21-24 are in the present embodiment provided in the form of swivel pins. At its second end the clamping arm 9 comprises a first clamp plate 20 and a second clamp plate 19. The first clamp plate 20 extends in parallel with the clamping arm 9, and the second clamp plate 19 extends perpendicularly with the clamping arm 9. The first clamp plate 20 has a contact face 5, which in the locking end position of the clamping tool 1 in the example shown supports an upper horizontal surface of the workpiece 2. The second clamp plate 19 has a contact face 4, which in the locking end position of the clamping tool 1 correspondingly supports a vertical surface of the workpiece 2, said vertical surface being a surface of the workpiece 2 facing in a direction away from the base 6. The clamp plates 19, 20 are manufactured by forming a metal plate in a 90° angle. The clamp plate 20 is secured to the clamping arm 9 by means of two screws 50, 51.

The principle of operation of the clamping tool 1 according to Figs 1 and 2 is described in the following. In fig. 1 the clamping tool 1 is in the releasing end position. In this position the first and second arms 14, 10a of the toggle joint 13 form an angle of about 80° with each other, the point formed by the arms 14, 10a being directed obliquely upwards, i.e. towards the second end of the clamping arm 9. By manually rotating the handle 11 of the activation arm 10 in the direction of the arrow A in Fig. 1, the arms 9, 10, 10a, 12, 14, 17 pivot about their respective pivots 17a-17c and 21- 24 from the releasing end position shown in fig. 1 towards the locking end position shown in fig. 2. During movement from the releasing to the locking end position, the clamping arm 9 follows a path corresponding to the arrow B shown in Fig. 1. Thus, the clamping arm 9 initially moves past the workpiece 2 in the horizontal direction on the surface of the workpiece 2 directed away from the base 6. This allows for the clamp plate 19 to pass the workpiece 2 in the vertical direction on the left side of the work piece 2 in Figs 1 and 2. Continuing its path in the direction of the arrow B, the clamp plate 19 then moves in the opposite horizontal direction, i.e. towards the base 6, until it reaches said side surface of the workpiece 2, i.e. is in the locking end position of Fig. 2. Simultaneously, the contact surface 5 of the clamp plate 20 contacts the upper surface of the workpiece 2. In this position the clamp plate 19 and the support part 3b secure the workpiece 2 in the horizontal direction, and the clamp plate 20 and the support part 3a correspondingly secure the workpiece 2 in the vertical direction.

The toggle joint 13 reaches a dead point position when the two arms 14, 10a form an angle of about 180° with each other. The clamping tool 1 is arranged such that the toggle joint 13 has just passed the dead point position when reaching the locking end position in Fig. 2. More specifically and as it appears from the figure, the angle between the arms 14, 10a is about 177° (or 183° when measured corresponding to the above described initial angle between the arms 14, 10a of about 80°). A stop in the form of a stop plate 40 is provided on the base 6, connecting the two plates of the housing 6a, the toggle joint 13 abutting the stop plate 40 when said angle between the arms 14, 10a has reached the desired value. Thereby, the clamping tool 1 is locked, as forces exerted by the workpiece 2 on the clamping arm 9 towards the releasing end position of the clamping tool 1 are not large enough to force the toggle joint 13 to move beyond the dead point position of the toggle joint 13; thus, a rela- tively large force must be overcome to move the clamping tool 1 out of the locking end position towards the releasing end position. As a consequence, the workpiece 2 is clamped securely and precisely to the support 3 both in a downwards direction and in a direction towards the base 6. Further, in the locking end position of the clamping tool 1 the com- bined arm system of the clamping tool 1 is labile, ensuring that the clamp plates 19, 20 exert no or only small forces on the workpiece 2 such that any risk of deformation of the workpiece 2 during the welding operation is minimized.

When the welding operation has been completed, i.e. a welded object has been manufactured from a number of work pieces, the welded object is released from the support 3 by rotating the handle 11 in the opposite direction of the arrow A. The clamping arm 9 then moves through a path opposite the arrow B until having reassumed the releasing end position of Fig. 1. The welded object can then be lifted in the vertical direction past the clamp plates 19, 20 and thus released from the support 3.

If the clamping arm 9 rotates any farther towards vertical than the position shown in Fig. 1, there is a risk that the arm system of the clamping tool 1 jams, making it hard or impossible to manually rotate the handle 11. To prevent this, in the present embodiment a stop screw 41 has been provided in the rocking arm 12, the stop screw 41 abutting the first (lower) end of the clamping arm 9 and stopping it from further rotation about the pivot 23 when having reached the position of Fig. 1.

The clamping tool 1 according to the invention may be designed in numerous other ways than the embodiment shown in the figures. For example, a further toggle joint (corresponding to the two simultaneously working toggle joints with reference numerals 13 and 16 in the above mentioned EP 1159110 B) may be implemented in order to provide further locking strength of the clamping tool 1.

Claims

P A T E N T C L A I M S

1. A clamping tool (1) for clamping a workpiece (2) to a support (3a, 3b, 3c), comprising a base (6), a clamping arm (9), an activation arm (10) pivotally connected to said base (6) for moving said clamping arm (9) between a releasing end position and a locking end position, and a first and a second arm (14, 10a) forming a toggle joint (13) arranged to reach a dead point position when said activation arm (9) is moved from said releasing to said locking end position, c h a r a c t e r i z e d in that said first and second arms (14, 10a) of said toggle joint (13) in said releasing end position form an angle below 180°, preferably below 90°, with each other, a point formed by said angled first and second arms (14, 10a) being directed substantially towards said clamping arm

(9).

2. A clamping tool (1) according to claim 1, wherein said first arm (14) of said toggle joint (13) via a first pivot (17a) is connected piv- otally to a first end of an intermediate arm (17), a second end of said intermediate arm (17) being pivotally connected via a second pivot (17b) to said clamping arm (9), said intermediate arm (17) further being connected pivotally to said base (6) via a base pivot (17c) positioned between said ends of said intermediate arm (17).

3. A clamping tool (1) according to claim 2, wherein said base pivot (17c) in the releasing end position of said clamping tool (1) is positioned eccentrically, i.e. displaced from an imaginary straight line (L) connecting said first and second pivots (17a, 17b), in a direction away from said clamping arm (9), said intermediate arm (17) preferably being V-shaped, said base pivot (17c) being positioned at a point of said V- shape.

4. A clamping tool (1) according to claim 2 or 3, wherein said second pivot (17b) connects said intermediate arm (17) to a first end of said clamping arm (9), said clamping tool (1) further comprising a rock- ing arm (12), which at one end is pivotally connected to said base (6) via a pivot (22) and at another end is pivotally connected to said clamping arm (9) via a pivot (23) positioned between said first end and a second end of said clamping arm (9).

5. A clamping tool (1) according to any one of the previous claims, wherein said activation arm (10) is connected pivotally to said first arm (14) of said toggle joint (13) via a pivot (24) positioned at a first end of said activation arm (10), and said activation arm (10) is pivotally connected to said base (6) via a pivot (21) positioned between said first end and a second end of said activation arm (10), said pivots (24, 21) defining said second arm (10a).

6. A clamping tool (1) according to any one of the previous claims, wherein said toggle joint (13) in said locking end position has just passed said dead point position, said first and second arms (14, 10a) of said toggle joint (13) in said locking end position forming an angle preferably between 174 and 179°, preferably between 176° and 178°.

7. A clamping tool (1) according to any one of the previous claims, wherein a stop (40), preferably a stop plate, is provided on said base (6), said toggle joint (13) abutting said stop (40) in said locking end position.

8. A clamping tool (1) according to any one of the previous claims, wherein said base (6) comprises a foot (6b), which extends into a housing (6a), which housing (6a) in said locking end position encloses said toggle joint (13) and preferably an intermediate arm (17).

9. A clamping tool (1) according to any one of the previous claims, wherein said clamping arm (9) at a second end comprises a first contact face (5) positioned to extend substantially in parallel with said clamping arm (9) and a second contact face (4) positioned to extend substantially perpendicularly with said clamping arm (9).