Blind rivet setting device and method for setting a blind rivet

Abstract

Blind rivet setting device and method. The blind rivet setting device includes a housing; a pulling mechanism arranged in the housing; an electric motor structured and arranged move the pulling mechanism in a pulling direction out of a rivet receiving position; a control device, which is structured and arranged to control the motor, including a tear-off detection device that generates a mandrel tear-off signal when a pulling mandrel is torn off; and an operating device that is connected to the control device. When the mandrel tear-off signal is generated, the control device stops the driving of the pulling mechanism in the pulling direction.

Claims

1. A blind rivet setting device comprising: a housing; a pulling mechanism arranged in the housing; an electric motor structured and arranged to move the pulling mechanism in a pulling direction out of a rivet receiving position; a control device, which is structured and arranged to control the motor, comprising a tear-off detection device that monitors current or electric power drawn by the motor to generate a mandrel tear-off signal when a pulling mandrel is torn off; and an operating device that is connected to the control device; wherein, when the mandrel tear-off signal is generated, the control device is configured to stop the driving of the pulling mechanism in the pulling direction, and wherein the tear-off detection device comprises a current monitor structured and arranged to constantly ascertain a current fed to the motor, which includes a maximum value and an intermediate maximum occurring prior to the maximum value, and to generate the mandrel tear-off signal only when the current, after reaching the maximum value, drops at least by a predetermined percentage of the maximum value within a pulling movement of less than 1 mm, whereby the tear-off detection device does not detect the intermediate maximum as the maximum value.

2. The blind rivet setting device according to claim 1, wherein the control device is structured and arranged to decelerate the motor while energy is recovered.

3. The blind rivet setting device according to claim 2, wherein, when the mandrel tear-off signal is generated, the control device is structured and arranged to reverse the motor and to move the pulling mechanism counter to the pulling direction.

4. The blind rivet setting device according to claim 3, wherein the control device is structured and arranged to move the pulling mechanism all the way into the rivet receiving position.

5. The blind rivet setting device according to claim 3, wherein the control device is structured and arranged to move the pulling mechanism all the way into a position outside of the rivet receiving position.

6. The blind rivet setting device according to claim 5, wherein the position outside of the rivet receiving portion is a position immediately before the pulling mechanism opens.

7. The blind rivet setting device according to claim 1, wherein the predetermined percentage is 30%.

8. The blind rivet setting device according to claim 1, wherein the operating device is structured and arranged to transmit at least two different actuation signals to the control device depending on different actuation modes.

9. A method for setting a blind rivet using the blind rivet setting device of claim 1 comprising: actuating the control device to move, via the controlled electric motor, the pulling mechanism in the pulling direction out of the rivet receiving position; wherein, when a pulling mandrel is torn off, the method further comprises automatically generating a mandrel tear-off signal so the control device stops the moving of the pulling mechanism in the pulling direction.

10. The method according to claim 9, wherein, when the mandrel tear-off signal is generated, the method further comprises decelerating the motor and recovering energy.

11. The method according to one of claim 10, wherein, when the mandrel tear-off signal is generated, the method further comprises altering the direction of movement of the pulling mechanism.

12. The method according to claim 11, further comprising moving the pulling mechanism all the way into the rivet receiving position.

13. The method according to claim 11, further comprising moving the pulling mechanism into a position outside of the rivet receiving position.

14. The method according to claim 13, wherein the position outside of the rivet receiving position is a position immediately before the pulling mechanism opens.

15. The method according to claim 9, further comprising monitoring a current draw of the motor to generate the mandrel tear-off signal and generating the mandrel tear-off signal when, after reaching a maximum value, the current drops by at least a predetermined percentage of the maximum value.

16. The method according to claim 9, wherein the operating device is actuatable in at least two different actuation modes and transmits a different signal to the control device in each actuation mode.

17. A blind rivet setting device, comprising: an electric motor; a pulling mechanism; a control device to move, via the electric motor, the pulling mechanism in a pulling direction out of a rivet receiving position, wherein, only when a predetermined percentage drop from a maximum current drawn by the electric motor occurs within a pulling movement of less than 1 mm, which is indicative of a pulling mandrel being torn off, the control device is configured to stop moving of the pulling mechanism in the pulling direction and the electric motor is decelerated to recover energy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:

(2) FIG. 1 shows a highly schematized view of essential functional elements of a blind rivet setting device; and

(3) FIG. 2 shows a highly schematized progression of the force over the distance during the setting of the blind rivet.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.

(5) The mechanical structure of a blind rivet setting device is described in DE 41 26 602 C2, the disclosure of which is expressly incorporated by reference herein in its entirety. For this reason, only those functional elements which are essential for understanding the present invention are explained below.

(6) A blind rivet setting device 1 comprises a housing, not illustrated in greater detail, in which a pulling mechanism is arranged. The pulling mechanism comprises a clamping jaws arrangement 2 which is connected to a hollow threaded spindle 3. The threaded spindle 3 is engaged with a gearing device 4. The gearing device 4 is connected to a reversible electric motor 6 via a transmission element 5.

(7) The clamping jaws arrangement comprises multiple clamping jaws 7, 8 which are closed, that is, pressed against one another by a certain force, in a setting operation of a blind rivet, not illustrated in greater detail, in order to grasp a pulling mandrel of the blind rivet and apply a pulling force thereto. This closed state of the clamping jaws arrangement 2 is illustrated by solid lines. However, the clamping jaws arrangement 2 can also be moved into a rivet receiving position, illustrated by dashed lines, in which the clamping jaws 7, 8 are open and form a receiving opening 9 for the rivet mandrel.

(8) From this rivet receiving position, the clamping jaws arrangement 2 can be moved in a pulling direction 10, illustrated by an arrow, when the motor 6 acts on the clamping jaws arrangement 2 via the gearing device 4 and the threaded spindle 3.

(9) The motor 6 is connected to a control device 11. The control device 11 receives electric energy from a battery 12, which can also be embodied or formed as a rechargeable battery or storage battery. The control device 11 is also connected to an operating device 13 which comprises, e.g., a pushbutton or a pressure switch 14.

(10) The control device 11 feeds the electric motor 6 energy in the form of electric current via a feed line 15. In the feed line 15 (or in a different position) in the control device 11, a current sensor 16 is arranged which forms part of a tear-off detection device 17. Here, the current sensor 16 and the tear-off detection device 17 are illustrated as discrete elements. However, they can also be a component of the control device 11.

(11) FIG. 2 shows, in schematic form, the progression of the force F over the distance s that the clamping jaws arrangement 2 travels in a setting operation of a blind rivet. A function 18 is illustrated. From the function 18, it follows that the force initially increases during the setting of a blind rivet. In many cases, there then occurs an intermediate maximum 19 when the pulling mandrel slips into the rivet sleeve. The force then continues to increase, which can be attributed to the pulling mandrel forming the closing head on the rivet sleeve. The force subsequently continues to increase up to a maximum 20 and then drops off abruptly when the pulling mandrel tears off. The tear-off detection device 17 continuously monitors the current with the aid of the current sensor 16 (or in a different manner) and detects the maximum 20 not only in that it registers a maximum generally, but rather in that it checks whether the current, after reaching the maximum value 20, drops by a predetermined percentage of the maximum value. This predetermined percentage can be equal to 50%, for example. The drop must occur, for instance, in a section of the distance s which is smaller than 1 mm, preferably smaller than 0.5 mm. It is thus eliminated, with high certainty, that the tear-off detection device 17 incorrectly identifies the intermediate maximum 19 as the maximum 20.

(12) The force, the progression 18 of which is illustrated in FIG. 2, is produced by a torque of the motor 6 via the gearing device 4. The current draw of the motor 6 correlates sufficiently with the torque, meaning that if the torque increases, then the current draw of the motor 6 also increases. The maximum value 20 of the force F can thus be ascertained with sufficient accuracy by a corresponding maximum of the drawn current. In the same manner, the decrease in force illustrated in FIG. 2 can be detected from a drop or a decrease in the current draw.

(13) The tear-off detection device 17 immediately relays the detection of the mandrel tear-off to the control device 11. The control device 11 subsequently stops the driving of the clamping jaws arrangement 2 in the direction of pull 10. Advantageously, the control device 11 decelerates the motor 6 while energy is recovered. The energy gained thereby is fed back into the battery 12. This has two advantages. On the one hand, energy is recovered. On the other hand, through the deceleration of the motor 6, less time is lost.

(14) Once the motor 6 has reached its idle state, the control device 11 reverses the motor 6 so that the clamping jaws arrangement 2 is moved counter to the pulling direction 10. Alternatively, the motor 6 can also simply remain idle.

(15) This movement can extend all the way into the rivet receiving position illustrated by dashed lines, in which the clamping jaws 7, 8 are moved away from one another so that the torn-off rivet mandrel is released. This is then the shortest possible cycle time, since the clamping jaws arrangement 2 is, after the completion of the setting operation, immediately available again in a position in which it can receive a new rivet mandrel.

(16) In some situations, however, it may be disadvantageous to move the clamping jaws arrangement 2 into the rivet receiving position, for example, when the blind rivet setting device is held in a downward direction during the riveting. In this case, the torn-off pulling mandrel could fall out of the receiving opening 9 and damage the item that is to be joined, or cause problems in another way, for example, causing a risk of a short circuit for electrical subassemblies or rattling noises if the rivet mandrel loosely lies around in a component in an uncontrolled manner.

(17) In this case, the clamping jaws arrangement 2 is not moved all the way into the rivet receiving position, but rather into the position illustrated by solid lines which is outside of the rivet receiving position. This position is, for example, defined such that the clamping jaws arrangement 2 must only travel a short distance in order to open the clamping jaws 7, 8.

(18) In a manner not illustrated in greater detail, a mandrel collecting container that receives the torn-off pulling mandrels can also be provided at the end of the threaded spindle 3 facing away from the clamping jaws arrangement 2.

(19) The different end positions of the clamping jaws arrangement 2 can then be selected by an actuation of the pressure switch 14.

(20) If the pressure switch 14 is only actuated briefly, the control device 11 starts the setting operation and, with the aid of the motor 6, moves the clamping jaws arrangement 2 in the pulling direction up until the tearing-off of the pulling mandrel, which is detected as a result of the maximum 20 being reached. The clamping jaws arrangement 2 is then moved counter to the pulling direction 10 back into the rivet receiving position again and the clamping jaws 7, 8 are opened.

(21) If the pressure switch 14 is pressed continuously, however, then the clamping jaws arrangement 2 is moved up until the tearing-off or breaking of the pulling mandrel and then moved back into the position shortly before the rivet receiving position. The clamping jaws arrangement 2 is only moved back into the rivet receiving position when the operator releases the pressure switch 14. The operator can thus independently decide when the pulling mandrel is to be disposed of.

(22) It is also possible to leave the clamping jaws arrangement 2 in place in the attained position after the tearing-off of the pulling mandrel and to allow the resetting operation of the clamping jaws arrangement 2 into the rivet receiving position to begin later altogether. Here, the resetting operation of the clamping jaws arrangement 2 can also be initialized by a release of the pressure switch 14, for example.

(23) Of course, the different operating states can also be set up in a different manner, for example, by providing an additional reversing switch.

(24) If no rivet has been received in the blind rivet setting device and the setting operation is nevertheless started, it is also not possible for a drop in the maximum current to take place. The clamping jaws arrangement 2 is then, for example, moved into the back end position, which corresponds to the maximum stroke, and remains in place after reaching the back end position without the clamping jaws arrangement 2 being moved back into the rivet receiving position. Only after a release or renewed actuation of the switch 14 is the return travel into the rivet receiving position started.

(25) The current sensor 16 can, as explained above, also be a component of the control device 11. It can also be arranged between the control device 11 and the battery 12.

(26) It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.