Tool for mounting a tension clamp

A tension clamp (19) includes a band (20) surrounding an object to be fastened and a buckle (21) arranged on the inner band end portion (22) and surrounding the band (20), with the outer band end portion (23) extending through the buckle (21). A tool for mounting the tension clamp includes a holding device for holding the buckle (21) along with the band (20) surrounding the object to be fastened, a tensioning device for tensioning the band (20) round the object to be fastened by applying tension to the outer band end portion (23), a locking device (50) for locking the buckle (21) on the band (20), and a severing device for cutting off excessive band length. The locking device (50) has plier jaws (54) adapted to be inserted into lateral windows (25) of the buckle (21) for deforming side edge portions (24) of the other band end portion (23).

PRIOR ART

For mounting an object such as an air bag material on a gas generator or an air bag on a mounting plate, tension clamps, such as known from U.S. Pat. No. 8,424,166 B2, are used which consist of a band and a buckle disposed on one end portion of the band.

U.S. 2009/0114308 A1 discloses a tool by which such a tension clamp, which has been pre-assembled from a band and a buckle and placed on the object, is tensioned round the object, the buckle is subsequently locked on the band, and the excessive length of the outer band end is cut off. To do so, the object to be fastened including the tension clamp is placed in a holder, the outer band end is clamped between a tensioning roller and a pressure roller, and the tensioning roller is rotated. When a given band tension or a given rotation of the pressure roller is reached the band is locked to the buckle by being deformed within the buckle using a spring-loaded plunger. At the same time, the outer band end which projects from the buckle is cut off by means of a cutting wheel which is rotated together with the plunger.

Deforming the band within the buckle requires the object to be fastened as a counter element to receive the force exerted by the plunger. This involves the risk of the object to be fastened being damaged.

As another disadvantage of the known tool, the cutting of the band generates a sharp-edged end piece projecting from the buckle, which may lead to injuries in the subsequent handling.

In another tool for mounting a tension clamp, as known from U.S. Pat. No. 3,641,629, a buckle is mounted on a band by means of two counter-acting plier jaws, each of which has an inclined surface to engage a lateral window in the buckle. The inclined surfaces are convex at their upper sides and produce a convex hump in the band to be locked in an aperture of the buckle. Higher tensional forces occurring in the band will entail the risk of the hump slipping out of the aperture so that the locking will open.

SUMMARY OF THE INVENTION

The invention is based on the object to avoid, at least in part, the disadvantages which exist with comparable prior art tools. A more specific object maybe seen in providing a tool of the type described above by which a tension clamp maybe mounted with the force required for a secure fixation and without any substantial influence on the object to be fastened.

This object is achieved by the invention. In the tool formed in accordance with the invention, a locking device has means which may be moved into a lateral window of the buckle for deforming a side edge of the outer band end portion. The deforming forces act parallel to the surface of the object to be fastened and are supported by the tool. The object or structural member is thus not influenced or required within the area of the buckle even when relatively high deforming forces are exerted on the buckle to achieve a secure locking.

The locking device has preferably two plier jaws adapted to move into opposite windows of the buckle for simultaneously deforming both side edges of the outer band end portion. This prevents transverse forces from acting on the buckle and the locking takes place symmetrically.

In another embodiment, the plier jaws have inclined surfaces at their sides which are remote from the inner band end portion during the deforming process, and the width of the plier jaws corresponds to the clear width of the windows as measured in the longitudinal direction of the band. This allows the portions of the band lying within the area of the window to be notched and bent up, wherein the windows of the buckle themselves form the cutting edges for the notching. Part of the occurring wear thus takes place on the buckle rather than on the tool.

The severing device for shearing off the band preferably has a shearing member movable in a direction transverse to the longitudinal direction of the band wherein the shearing member, in shearing off the band, cooperates with a part of the buckle so that part of the wear takes place on the buckle rather than on the tool also in this process. The edge of the shearing member facing the buckle is rounded off to avoid abrasion of material (e.g. of a coating) when the tension clamp is inserted.

In an embodiment, the severing device has two counter-acting plier jaws with cutting edges for notching both edges of the outer band end portion at the end face of the buckle remote from the inner band end portion. Preferably, the plier jaws have inclined surfaces for bending up triangular parts of the band portion to be severed. This arrangement performs the severing without forces acting on the object to be fastened.

In further embodiments, the surfaces of the locking and, respectively, severing device, which effect the notching process and/or the severing process are grooved to counteract the generation of chips, or if generated, keep them as small as possible.

Preferable, the part of the locking device to be moved into the lateral windows of the buckle may be controllable in such a manner that it serves to fix the buckle during the severing step, thus fulfilling a further purpose.

The locking device and the severing device maybe controllable by a common crank, preferably in a manner that the locking device is released from its engagement in the windows of the buckle after the severing step.

In a further embodiment, the device for tensioning the band round the object to be fastened has a clamping mechanism which is movable away from the buckle holder to clamp the outer band end portion. For accelerating the tensioning process, the movement of the clamping mechanism is controlled in its first part dependent on distance and then dependent on force, wherein the change-over from distance control to force control takes place at a predetermined force threshold.

EMBODIMENTS

The tension clamp19shown inFIGS. 1aand 1bof the drawings includes a band20and a buckle21. Both parts are preferably made of metal.FIG. 1aillustrates a condition in which the buckle21of the tension clamp19is fixed at the inner band end portion22, the band20is placed round an object to be fastened (not shown), and the outer band end portion23is fed through the buckle21. During the final mounting, the band20is tensioned round the object to be fastened by pulling its outer end portion23, in the tensioned condition the outer end portion23is locked by deforming parts24of its side edges (FIG. 1b) in the area of lateral windows25of the buckle21, and excessive band length is removed at the rear end face26of the buckle21.

The tool shown inFIG. 2includes a holding device for holding the tension clamp19and the object to be fastened (not shown) which is surrounded by the clamp, a tensioning device for tensioning the tension clamp19round the object to be fastened, a locking device50for locking the band20to the buckle21in the tensioned condition, and a severing device for severing excessive band length. These devices are explained in more detail below.

As shown inFIGS. 3 and 7, the outer band end portion23of the tension clamp19is inserted in a passage31(FIG. 7) provided in the lower part of the tool head30to such a maximum extent that the band20abuts a stop34(FIG. 5) integrated in a body of the clamping mechanism. A proximity sensor35(FIGS. 5 and 7) makes sure that band is present in the tool and has been moved into the passage31to a sufficient extent.

In this position, the band20is fixed by a clamping mechanism40which is shown inFIGS. 4 to 7and constitutes the holding and which includes a plunger42driven by a toggle lever41. When the clamping mechanism40is driven by actuating a start button (not shown) or by an electronic control, the plunger42is lowered to fix the band20by pressure against the bottom portion32of the slider33.

Subsequently, the band20is tensioned round the object to be fastened by the tensioning device (FIGS. 4 to 6) pulling the outer band end portion23. The tensioning force is applied by an electrically actuated cylinder having a piston rod45which moves the entire clamping mechanism40and all associated parts such as the proximity sensor35and the slider33to the right until a predetermined force value is detected by a load cell46.

To shorten the time required for the tensioning process, the piston rod45may be controlled at first dependent on distance and in the final part of the movement, when a predetermined tension is reached, dependent on force.

In this position, the locking device50shown inFIGS. 8 to 10is operated to lock the buckle21on the band20. A locking device50, which is arranged on the tool head30and is downward movable through a control crank51includes a pair of plier jaws54which are pivotal on pins53, each jaw54having an inclined surface55(FIGS. 10 and 12) at their lower ends.

In this condition, the plier jaws54are moved toward each other by the control crank51so as to engage the windows25of the buckle21, and their inclined surfaces55notch and bend up the side edge portions24of the band at the edges of the windows (seeFIG. 1b). The width of the plier jaws54corresponds to the clear width of the windows25measured in the longitudinal direction of the band. This achieves a locking between the band20and the buckle21substantially free of play. Since the buckle21itself is used for notching shearing the side edge portions24of the band20, the buckle takes up part of the wear.

As seen in the enlarged representations ofFIGS. 11 and 12, the inclined surfaces55of the plier jaws54are provided with grooves56in order to counter-act the generation of chips or, if generated, keep them as small as possible, when the side edge portions24are notched.

By the further movement of the control crank51(FIG. 8), the severing device is raised whereby the length of the outer band portion23projecting from the buckle21is sheared off between a cutting edge61(FIGS. 7 and 11) formed on a lower part60of the passage31and an edge62at the end face26of the buckle21(FIG. 1b). The cutting edge61rounded to avoid excessive wear of the band20. During the shearing process, the buckle21continues to be fixed by the plier jaws54of the locking device50.

The plier jaws54are subsequently opened to prevent them from becoming stuck in the windows25of the buckle21and failing to release the buckle21.

Then, the piston rod45is moved to the left in the drawings whereby the plunger42of the clamping mechanism40releases the severed part of the outer band portion23which is still clamped. The slider33is then moved to the left so that the severed porting of the outer band portion23is set free and can fall out of the tool.

In the severing device explained with reference toFIGS. 7 and 13, the excessive band length is cut off by moving the part of the tool forming the passage31upward, i.e. away from the tension clamp and the object to be fastened. Since an edge formed on the end face26of the buckle21is used for this shearing movement, the buckle21again takes up part of the wear and the tool is saved. At the same time, a sharp-edge end of the band20is prevented from projecting from the buckle21.

As shown inFIG. 11, the lower surface of the passage31, which co-operates with an edge of the buckle21in severing the excessive band portion23, is provided with grooves37which are shaped and dimensioned similar to the grooves56in the plier jaws54and again serve the purpose of counter-acting the generation of chips or, if generated, keeping them as small as possible.

In the alternative embodiment of the severing device shown inFIG. 14, the excessive band length is cut off by a knife65which is moved in the direction of the tension clamp and shears against the surface of the surface of the passage31. The knife65is chamfered at66to press the projecting band against the buckle21thereby avoiding sharp edges.

The further embodiment of the severing device shown inFIG. 15uses plier jaws70which act against one another to notch both sides of the band20on the outer side of the buckle21. In this process, a narrow centre web of the band20is left, which is subsequently torn off. This again saves the tool.

In the embodiment of the severing device shown inFIG. 16, plier jaws72are provided which have inclined surfaces similar to those of the plier jaws54of the locking device, for folding up triangular portions73(FIG. 17) of the band part to be cut off. This again leaves a narrow centre web74, which is subsequently torn off.

In the severing devices shown inFIGS. 14 to 17, the parts of the tool which sever the band portion23may also be grooved similar to the passage31inFIG. 11in order to counter-act the generation of any chips or, if generated, keep them as small as possible.

In the alternative illustrated inFIG. 18, the clamping mechanism80has an eccentric lever82which can be rotated by means of a piston rod81. When the piston rod81moves to the right the eccentric lever82is rotated and fixes the band by pressing it against the bottom part32of the slider. After the excessive length of the outer band section has been cut off, the piston rod81is moved to the left so that the severed band portion becomes free to fall out of the tool.

REFERENCE NUMBERS

22Inner band end portion

23Outer band end portion

74Centre web