Rivet head caulking machine

Abstract: The caulking machine has a column (21) having a table (38) for placing a work having rivet shanks passing therethrough, a cylinder (23) vertically movably mounted on the column (21), a piston shaft (24) fixedly mounted in the cylinder (23) so as to be movable together with the cylinder (23), a spindle (25) rotatably mounted in the piston shaft (24), and a rivet head forming tool (26) having a forming shaft (27) and secured to the bottom end of the spindle (25). The forming shaft (27) is adapted to be pressed against the rivet shank on the work by stretching the cylinder (23) and rotated by a motor (28) through the spindle (25) to form a rivet head on the rivet shank. The machine has a rotation detector (31) for judging whether a rivet head is being formed or the machine is idling by measuring the rotation of the forming shaft (27). If judged that the machine is idling, a display device can be activated and the operation of the machine can be stopped.

Description: This invention relates to a rivet head caulking machine as defined in the preamble of the claim. A machine of this kind has been known from DE-A-3 715 905. As shown in Fig. 4, in a prior art caulking machine of this type, after placing a part to be worked having a plurality of rivet shanks passing therethrough on a table 2 of a column 1, a piston shaft 4 is lowered by stretching a cylinder 3 mounted on the column 1. A spindle 6 is rotatably mounted through the piston shaft 4 along its axis. It is driven by a motor 5 mounted on the top end of the piston shaft 4. On the bottom end of the spindle 6 is mounted a rivet head forming tool 8 having a forming shaft 7 for forming a rivet head on the rivet shank. The work piece having rivet shanks passing therethrough to secure parts is set on a table which is moved in both X and Y directions so that the caulking points will come under the head of the caulking machine one after another. Since this machine is not provided with means for detecting the existence of a rivet shank, it is impossible to check whether a rivet head is being formed or the spindle is idling. Therefore, an operator had to check whether or not there was a rivet shank. Should the rivet head forming tool lower onto the work with no rivet shank present, the work might get marred.. If the part to be worked has a great number of rivet shanks passed therethrough, such checking with human eye requires a lot of trouble and thus is extremely inefficient. It is an object of this invention to provide a rivet head caulking machine which can check whether or not there is a rivet shank. In accordance with the present invention, this object is achieved by a rivet head caulking machine as claimed. Ideally, the forming shaft should not rotate at all when the rivet head forming tool makes one rotation while forming a rivet head by pressing the forming shaft of the rivet head forming tool against the rivet shank (in other words, the forming surface of the forming shaft should not slip on the rivet head being formed). Otherwise, its rotation, if any, should be negligibly small. Namely, it should make less than one rotation per rotation of the rivet head forming tool. During idling, the forming tool makes one rotation for every rotation of the rivet head forming tool. Thus, by measuring the rotation of the forming shaft with the detecting means, it can be checked whether the rivet head is being formed or the machine is idling. If the caulking machine is judged to be idling, this fact may be indicated on a display device and the operation of the machine may be stopped. This relieves an operator of the work of checking whether or not there is a rivet and thus improve the efficiency of caulking operation. Other features and objects of the present invention will become apparent from the following description taken with reference to the accompanying drawings, in which: Fig. 1 is a side view of the caulking machine embodying this invention; Fig. 2 is a partially cutaway enlarged side view of a portion of the same; Fig. 3 is a cross-sectional plan view of the same; and Fig. 4 is a side view of a prior art caulking machine. Now the embodiment of this invention will be described with reference to the accompanying drawings. In the figures, numeral 21 designates an upright column extending from a base 22. A cylinder 23 is mounted on the top end of the column 21. A piston shaft 24 is mounted in the cylinder 23 so as to be moved up and down by operating the cylinder. A spindle 25 extends through the piston shaft 24 along its axis and is rotatably supported in position. A rivet head forming tool 26 is mounted on the bottom end of the spindle 25. Since the rivet head forming tool 26 is well-known in the art, its detailed structure is not shown. It is mounted so that its forming shaft 27 will pivot with its axis inclined and so that the center of the forming shaft 27 at its lowermost end is aligned with the axis of the spindle 25. A motor 28 is mounted directly over the cylinder 23. Its driving force is transmitted to the spindle 25 through its output shaft 29 and a retractable joint 30. In the illustrated embodiment, the retractable joint 30 is slidably coupled and comprises a square shaft and a square hole for transmitting rotation. But it may have any other structure. Numeral 31 designates a detecting means for measuring the rotation of the forming shaft 27. In the illustrated example, the detecting means 31 has a cylindrical body 32 inserted from the bottom end of the forming shaft 27 and fixed thereto by a mounting screw 33. The cylindrical body 32 is provided on part of the outer periphery thereof with a reflective surface 34 formed by flat mirror finishing or sticking a reflecting plate thereon. Further, the detecting means 31 has a light-emitting and light-receiving sensor 36 mounted on an arm 35 fixed to the bottom end of the piston shaft 24 and adapted to move up and down together with the piston shaft 24 so as to be located opposite to the reflective surface 34. The detecting means may be made up of a protrusion provided on the outer periphery of the forming shaft 27 and a light emitter and a light receptor supported on an arm so as to be positioned opposite to the protrusion. With this arrangement, by stretching the cylinder 23, the spindle 25 is lowered together with the piston shaft 24 to press the forming shaft 27 of the rivet head forming tool 26 against the rivet shank. During this operation, the forming shaft should ideally not rotate at all when the rivet head forming tool 26 makes one rotation (in other words, not slip with respect to the forming head). Otherwise its rotation, if any, should be as small as possible. Namely, the forming shaft 27 should not make one rotation or more per rotation of the rivet head forming tool 26. During idling (when there is no rivet), the forming tool 27 makes one rotation per rotation of the rivet head forming tool 26. Thus, by measuring the rotation of the forming shaft 27 by means of the detecting means 31, it can be checked whether the rivet is being formed or the machine is idling. If the machine is found out to be idling, a display device (not shown) such as a light or an alarm may be activated to give notice of the fact that there is no rivet or the operation of the caulking machine may be stopped. In the drawings, numeral 37 designates a hole formed in the arm 35 through which the forming shaft 27 extends. 38 is a table secured to the column 21.

Claims: A rivet head caulking machine comprising a column (21) having a table (38) for placing a work piece having rivet shanks passing therethrough, a cylinder (23) vertically movably mounted on said column, a piston shaft (24) fixedly mounted in said cylinder (23) so as to be movable together with said cylinder, a spindle (25) rotatably mounted in said piston shaft, and a rivet head forming tool (26) having a forming shaft (27) and secured to the bottom end of said spindle (25), said forming shaft (27) being adapted to be advanced and pressed against the rivet shanks on said work piece by pressurising said cylinder and rotated by a motor (28) via said spindle to form a rivet head on said rivet shanks, characterized by detecting means (31) for measuring the rotation of said forming shaft (27) and means responsive to said detecting means (31) for activating a display device or stopping the operation of the caulking machine if said detecting means (31) detects idling rotation of the forming shaft (27) when said spindle (25) has been advanced in the absence of a rivet to be formed.

Inventors: UNO WATARU, UNO, WATARU
Applicants: YOSHIKAWA IRON WORKS, YOSHIKAWA IRON WORKS LTD.,
Application year: 1991
Main classification: B21J15
IPC codes: B21J15