TECHNICAL FIELD

The present invention relates to a fastening device, and in particular to a setting tool for a blind rivet.

BACKGROUND ART

Generally, a setting tool for a blind rivet is used to set and fasten a blind rivet fastener, such as a blind rivet and a blind rivet nut. The process of setting and fastening the blind rivet is known.

Referring to FIG. 1 and FIG. 2, the existing rivet gun disclosed by a Chinese patent application CN 110834060 A is suitable for setting a blind rivet 9 (as shown in FIG. 1) and comprises a shell 2, a drive unit 3, a pull unit 4, a clamping unit 5, a nose part 6, and a sensing unit 7. The pull unit 4 comprises a screw rod 42 extending along a second axis R2 as well as a connector 43 connected to the screw rod 42. The clamping unit 5 comprises a clamping sleeve 51 connected to the connector 43, a plurality of clamping blocks 52 angularly arrayed around the second axis R2 in sequence, a central rod 53, a clamping spring 54, and a stopper 55. The clamping sleeve 51 has an enclosing wall 511 and a clamping opening 512 defined by the enclosing wall 511. The clamping blocks 52 are arranged in the enclosing wall 511 and adjacent to the clamping opening 512. The central rod 53 can constantly abut against the clamping blocks 52 by means of an elastic force from the clamping spring 54. When pushed against the central rod 53, the clamping blocks 52 protrude from the clamping opening 512 and move towards the second axis R2 to clamp the blind rivet 9. A plurality of clamping teeth or convex ribs are provided inside each clamping block 52, and are constructed and configured to improve engagement with a mandrel (not shown) of the blind rivet.

When getting close to the final position (as shown in FIG. 2), the clamping spring 54 pushes against a head 531 of the central rod 53, such that the head 531 pushes against the clamping blocks 52; and in this way, the clamping blocks 52 move towards the clamping opening 512 and protrude from the clamping sleeve 51 via the clamping opening 512. When the clamping blocks 52 are pushed by the head 531 to move towards the clamping opening 512, the clamping blocks 52 gradually approach the second axis R2 to clamp the blind rivet 9.

However, when getting close to the final position, the backs of the clamping blocks 52 are supported against the clamping sleeve 51 by surface-to-surface contact. When the blind rivet fastener is set, part of the pulling force generated is used to form a closed head of the blind rivet fastener, and the other part of the pulling force is used to generate a clamping force. The clamping blocks 52 are supported against the mandrel of the blind rivet by means of this clamping force. As a result, the clamping teeth, which are intended to engage with the mandrel of the blind rivet, inside each clamping block 52 are seriously stressed, especially the clamping teeth corresponding to a front end of the clamping sleeve 51 are stressed to the greatest extent. Consequentially, the clamping teeth inside the clamping block 52 are abraded or fractured in a short time in most cases, such that setting tools cannot be used normally.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a setting tool for a blind rivet, which can effectively solve the problem of a setting tool being unable to be used normally due to damage or abrasion of clamping teeth inside clamping blocks of a clamping unit, thus reducing the repair rate of the setting tool.

In an embodiment of the present invention, a setting tool for a blind rivet comprises a shell as well as a drive unit, a pull unit, a clamping unit, and a nose part which are contained in the shell, wherein the clamping unit comprises a clamping sleeve connected to the pull unit, a plurality of clamping blocks angularly arrayed around a pulling direction in sequence, and a clamping spring; the clamping sleeve has an enclosing wall and a clamping opening defined by the enclosing wall; backs of the clamping blocks abut against an inner wall of the enclosing wall; a plurality of clamping teeth are provided on an inner side, facing a mandrel of a blind rivet, of the clamping block to improve the clamping of the clamping blocks to the mandrel of the blind rivet; the clamping spring is configured such that the clamping blocks are movable in the clamping sleeve between an initial position and a final position; when the clamping block is located at the final position, a front section of the clamping block protrudes from the clamping opening, and a rear section of the clamping block is retained in the clamping sleeve; and the clamping teeth located at the front section of the clamping block are at least partially removed in advance.

In a preferred embodiment of the present invention, the clamping teeth at the front section of the clamping block are all removed.

In another preferred embodiment of the present invention, the clamping teeth at the front section of the clamping block are partially removed and are lower than the clamping teeth at the rear section of the clamping block.

In a further preferred embodiment of the present invention, when the clamping blocks are located at the final position, the clamping teeth, closest to the clamping opening, at the front sections of the clamping blocks are all or at least partially removed.

Preferably, the clamping teeth are formed as convex ribs uniformly arrayed on the clamping block essentially in the pulling direction; the convex rib comprises a top edge, a first side surface, and a second side surface, wherein the top edge is essentially perpendicular to a central line of the mandrel; the first side surface faces the drive unit and extends from the top edge to a root of the corresponding clamping tooth at a first angle to the pulling direction; and the second side surface faces the nose part and extends from the top edge to the root of the clamping tooth at a second angle to the pulling direction.

More preferably, a rounded corner with a smooth transition portion is formed at the root of the clamping tooth by the first side surface and the second side surface.

More preferably, the first angle is larger than the second angle.

The top edge of the clamping tooth at the rear section of the clamping block is at least partially in surface-to-surface contact with a peripheral surface of the mandrel.

In the embodiments of the present invention, the clamping blocks are made from medium-carbon nickel-chromium-molybdenum alloy steel with a nickel content of about 1.6%-2.0%.

In the embodiments of the present invention, after the clamping blocks are subjected to heat treatment, the depth of a hardened layer ranges from 0.5 mm to 0.8 mm, and the surface hardness is not less than HV680.

When the blind rivet is set by using the setting tool for a blind rivet of the present invention, the mandrel of the blind rivet is clamped by the clamping blocks; when the clamping blocks are located at the final position, the front sections of the clamping blocks protrude from the clamping opening; the clamping teeth at the front section of each clamping block are at least partially removed in advance to achieve an avoidance effect at the front sections of the clamping blocks, so as to reduce or eliminate a concentrated stress or shear force acting on the front sections of the clamping blocks and generated due to unequal acting forces from the clamping sleeve and the blind rivet, wherein the unequal acting forces are caused by actual processing tolerance or design during riveting. In this way, early abrasion or fracture of the clamping teeth on the inner side of each clamping block can be avoided, so that the service life of the clamping blocks is prolonged, and the repair rate of the setting tool for a blind rivet is greatly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments mentioned can be better understood through the following detailed description and with reference to the drawings. It is emphasized that the various components are not necessarily drawn to scale. In fact, the size can be increased or decreased at will for the sake of clarity of discussion. In the drawings, the same reference numerals refer to the same elements.

FIG. 1 is a schematic sectional view showing an initial position of an existing setting tool for a blind rivet;

FIG. 2 is a schematic sectional view showing a final position of the existing setting tool for a blind rivet in FIG. 1 ;

FIG. 3 is a schematic perspective partial exploded view of a setting tool for a blind rivet in an embodiment of the present invention;

FIG. 4 is a schematic partial sectional view showing an initial position of the setting tool for a blind rivet in FIG. 3 in the embodiment;

FIG. 5 is a schematic partial sectional view showing a final position of the setting tool for a blind rivet in FIG. 3 in the embodiment;

FIG. 6 is a schematic view of a clamping block of a setting tool for a blind rivet in an embodiment of the present invention;

FIG. 7 is a schematic projection of the clamping block of the setting tool for a blind rivet in FIG. 6 in the embodiment;

FIG. 8 is a schematic partial enlarged view of the clamping block of the setting tool for a blind rivet in FIG. 7 in the embodiment;

FIG. 9 is a schematic projection of a clamping block of a setting tool for a blind rivet in another embodiment of the present invention; and

FIG. 10 is a schematic projection of a clamping block of a setting tool for a blind rivet in a further embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

A setting tool for a blind rivet of the present invention is described below with reference to FIG. 3 to FIG. 10.

Referring to FIG. 3 to FIG. 5, a setting tool for a blind rivet in an embodiment of the present invention is suitable for setting a blind rivet 7. The setting tool 1 for a blind rivet comprises a shell 2 as well as a drive unit 3, a pull unit 4, a clamping unit 5, and a nose part 6 which are contained in the shell. An axis R extending in a pulling direction is defined by the pull unit 4, the clamping unit 4, and the nose part 6.

The clamping unit 5 comprises a clamping sleeve 50 connected to the pull unit 4, a plurality of clamping blocks 51 angularly arrayed around the pulling direction in sequence, and a clamping spring 54, wherein the clamping sleeve 50 has an enclosing wall 52 and a clamping opening 53 defined by the enclosing wall 52; backs of the clamping blocks 51 abut against an inner wall of the enclosing wall 52; and a plurality of clamping teeth

55 are provided on an inner side, facing a mandrel 8 of the blind rivet, of each clamping block 51 to improve the clamping of the clamping blocks 51 to the mandrel of the blind rivet. Preferably, the clamping teeth 55 are formed as convex ribs uniformly arrayed on the clamping block essentially in the pulling direction. The clamping spring 54 is configured such that the clamping blocks 51 are movable in the clamping sleeve 50 between an initial position and a final position. As shown in FIG. 4, when the clamping blocks 51 are located at the final position, a front section 511 of the clamping block protrudes from the clamping opening 53, and a rear section 512 of the clamping block is retained in the clamping sleeve 50.

Referring to FIG. 3, when the clamping unit of the setting tool for a blind rivet of the present invention is located at the initial position, the clamping sleeve 50 is adjacent to the nose part 6. An end, abutting against the nose part 6, of each clamping block 51 does not protrude from the clamping sleeve 51 via the clamping opening 32. The clamping blocks 51 are located in a clamping space defined by the enclosing wall 52 and are radially spaced from the axis R, so that the mandrel 8 of the blind rivet 7 can be inserted into an axial hole in the nose part 6 to be surrounded by the clamping blocks 51. Rear sides of the clamping blocks 52 abut against a central rod 56 to compress the clamping spring 54. No clamping force is radially applied to the mandrel 8 by the clamping teeth 55 on the inner side of each clamping block 51 .

The clamping sleeve 50 can be driven by a screw rod of the pull unit to move to the final position along the axis R. When getting close to the final position (as shown in FIG. 5), the clamping spring 54 pushes against a head of the central rod 56, such that the central rod 56 pushes against the clamping blocks 51 ; and in this way, the clamping blocks 51 move towards the clamping opening 53 and protrude from the clamping sleeve 50 via the clamping opening 53. When the clamping blocks 51 are pushed by the central rod

56 to move towards the clamping opening 53, the clamping blocks 51 gradually approach the axis R while the enclosing wall 52 is gradually reduced in aperture to the clamping opening 53, such that the clamping teeth 55 at least partially contact and clamp the mandrel of the blind rivet. When getting close to the final position, the backs of the clamping blocks 51 are supported against the inner wall of the enclosing wall 52 of the clamping sleeve 50 by surface-to-surface contact. When a blind rivet fastener is set, part of a pulling force generated in the pulling direction shown in FIG. 5 is used to form a closed head of the blind rivet 7, and the other part of the pulling force is used to generate a clamping force. The clamping blocks 51 are supported against the mandrel 8 of the blind rivet 7 by means of the clamping force. The mandrel 8 of the blind rivet 7 is clamped, then pulled backwards, and finally split to be riveted to a plate.

Referring to FIG. 5, when the clamping unit 5 of the setting tool for a blind rivet is located at the final position, the clamping blocks 51 each have the front section 511 protruding from the clamping opening 53 as well as the rear section 512 retained in the clamping sleeve 50. In an ideal state, whether the clamping blocks 51 are located at the initial position or the final position, inner side surfaces of the front sections 511 and inner side surfaces of the rear sections 512 should be totally parallel to the axis R; that is, when the clamping blocks are located at the final position, a clamping force should be evenly applied to a peripheral surface of the mandrel 8 by the front sections 511 and the rear sections 512. However, due to the fact that the mandrel 8 of the blind rivet 7 cannot be totally parallel to the axis R constantly during riveting, and also due to errors possibly caused during processing or assembly, and abrasion of materials, the front sections 511 , protruding from the clamping opening 53, of the clamping blocks apply a larger clamping force in a radial direction, and especially marginal clamping teeth 551 closest to the clamping opening 53 are subjected to both the clamping force in the radial direction and the pulling force in the pulling direction. Thus, the clamping teeth at the front section 511 of each clamping block, especially the marginal clamping teeth 551 closest to the clamping opening 53, are most likely to be abraded or fractured. To prevent the clamping teeth from being abraded or fractured, in the setting tool for a blind rivet of the present invention, the clamping teeth at the front section of each clamping block are at least partially removed in advance to achieve an avoidance effect, so as to reduce or eliminate a concentrated stress or shear force acting on the front sections 511 of the clamping blocks 51 and generated due to unequal acting forces from the clamping sleeve 50 and the blind rivet, wherein the unequal acting forces are caused by actual processing tolerance, design, or the fact that the mandrel of the blind rivet cannot be totally parallel to the axis R constantly during the riveting.

Referring to FIG. 6 and FIG. 7, in a preferred embodiment of the present invention, the clamping teeth at the front section 511 of each clamping block 51 are all removed. For example, the clamping teeth at the front section are ground off. In this way, the inner side of the front section 511 of the clamping block 51 is essentially formed as a plane or an arc surface approximately parallel to part of the peripheral surface of the mandrel 8. As the rear section 512 of the clamping block 51 is still in the clamping sleeve 50, and the rear section 512 is thicker than the front section 511 in the radial direction, higher tensile property is endowed to the rear section 512, and the clamping teeth on the inner side of the rear section 512 are sufficient to clamp the mandrel of the blind rivet during the riveting. The benefit of grinding off all the clamping teeth at each front section is to simplify a processing technology without affecting the pulling force needed by the blind rivet during setting.

Referring to FIG. 4 to FIG. 7, the clamping teeth 55 are formed as the convex ribs uniformly arrayed on each clamping block 51 essentially in the pulling direction. Preferably, referring to FIG. 7 and FIG. 8, each convex rib comprises a top edge 550, a first side surface 551 , and a second side surface 552, wherein the top edge is essentially perpendicular to a central line of the mandrel; the first side surface extends from the top edge 550 to a root of the corresponding clamping tooth at a first angle a to the pulling direction; and the second side surface extends from the top edge 550 to the root of the clamping tooth at a second angle b to the pulling direction. More preferably, the first angle a is larger than the second angle b, facilitating insertion of the mandrel. In this way, the clamping force from the clamping teeth 55 is increased, and the abrasion of the clamping teeth is reduced. More preferably, a rounded corner with a smooth transition portion is formed at the root of the clamping tooth by the first side surface 551 and the second side surface 552 to reduce the risk of fracture. More preferably, the top edge 550 of the clamping tooth at the rear section of each clamping block is at least partially in surface-to-surface contact with the peripheral surface of the mandrel 8. Therefore, the top edge 550 is formed as a gently curved surface instead of a ridge. When the peripheral surface of the mandrel is clamped with the top edge 550, the top edge 550 is at least partially in surface-to-surface contact with the surface of the mandrel, so that the clamping tooth is less likely to be fractured when pulled, and the abrasion degree of the top edge 550 can be reduced.

Referring to FIG. 9, in another embodiment of the present invention, the difference from the foregoing embodiment is that the clamping teeth at the front section 511 of each clamping block 51 are not completely removed, but the clamping teeth at the front section 511 of each clamping block 51 are partially removed. As shown in FIG. 9, the clamping teeth at the front section 511 of the clamping block 51 are lower than the clamping teeth at the rear section 512 of the clamping block 51 . In this way, the concentrated stress or shear force generated due to the unequal acting forces caused by the actual processing tolerance, the design, or the fact that the mandrel 8 of the blind rivet cannot be totally parallel to the axis R constantly is avoided, and the number of clamping teeth remains the same, so that the force is applied to each clamping tooth more evenly during the riveting.

In a further preferred embodiment of the present invention, as shown in FIG. 10, the difference from the foregoing embodiments is that the clamping teeth, closest to the clamping opening 513, at the front sections of the clamping blocks are all or at least partially removed. Similarly, in the solution of this embodiment, the concentrated stress or shear force generated due to the unequal acting forces caused by the actual processing tolerance, the design, or the fact that the mandrel of the blind rivet cannot be totally parallel to the axis R constantly is avoided, and the number of clamping teeth remains the same, so that the clamping teeth are stressed more evenly during the riveting. Furthermore, as only the clamping tooth closest to the clamping opening is removed, the whole clamping block has higher abrasion resistance and a longer service life.

In addition, in the embodiments of the present invention, in order to further improve the abrasion resistance of the clamping blocks and reduce the possibility of the clamping teeth fracturing, the clamping blocks are made from medium-carbon nickel-chromium- molybdenum alloy steel with a nickel content of about 1.6%-2.0%, such as steels with grades of SNCM439/SNCM447/SNCM431. Such steel as an alloy steel with a high nickel content has improved strength and toughness and excellent abrasion resistance. Moreover, by performing proper heat treatment on the clamping blocks, the abrasion resistance of the clamping blocks can also be greatly improved. For example, after the clamping blocks are subjected to heat treatment, the depth of a hardened layer ranges from 0.5 mm to 0.8 mm, and the surface hardness is not less than HV680.

In conclusion, by means of improving the structure of the clamping blocks and/or selecting more suitable materials and more appropriate processing technologies, the setting tool for a blind rivet of the present invention is capable of setting 70000 blind rivets without causing the clamping teeth to fracture, thus greatly reducing the repair rate of the setting tool. As mentioned above, although the exemplary embodiments of the present invention have been described in the specification with reference to the drawings, the present invention is not limited to the above specific implementations, and may have many other implementations. The scope of the present invention should be defined by the claims and their equivalent meanings.