JPH01240232A - Device for detecting floating screw in automatic thread fastening machine - Google Patents

Abstract

PURPOSE:To improve the efficiency of a thread fastening operation by providing a screw adsorbing pipe which is brought into contact with a screw head inside a workpiece-face detecting member and detecting the relative moving distance between the detecting member and the pipe with a limit switch. CONSTITUTION:A sensor piece 20 is installed on a pipe-shaped workpiece-face detecting member 13, which is always energized downward with respect to a switch holder 10 by means of a spring 16. A screw adsorbing pipe 12 is fixed to the switch holder 10 and inserted into the inner face of the detecting member 13. When the screw adsorbing pipe 12 is brought into contact with a screw head portion, and if the screw is in a floating condition without being tightly fastened, the workpiece-face detecting member 13 is further moved downward until it is brought into contact with the workpiece face. Hence, the sensor piece 20 is lowered by the amount of difference between the screw contacting face and the workpiece contacting face, without giving detection by means of the limit switch 9 of the switch holder 10. Thereby, the propriety of thread fastening can be easily judged while efficiently carrying out the fastening operation.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a screw lifting detection device that can detect whether or not a tightened screw is floating above a workpiece surface in an automatic screw tightening machine. be.

[Background of the invention]

An example of this type of conventional bed floating detection device is disclosed in Japanese Patent Publication No. 61-254-96. In this example, a switch is attached to limit 1 on the support part that supports the power driver and moves up and down together with the driver, and the screw is tightened by moving relative to the support part and pin 1 of the power driver during work. When the suction pipe moves a predetermined distance, a limit switch is activated on the top of the suction pipe to detect the completion of tightening, and on the other hand, a limit switch is activated to allow the relative movement distance to reach a predetermined value. The structure is such that it is detected as a floating screw when the screw is not lifted.

However, in such a conventional screw 71 detection device,
Variations in the depth of the cross recess on the screw head deteriorate the accuracy of screw floating detection, and when replacing the pin I- due to human wear etc., set the limiter 1 each time according to the length of the replaced bit. This method has drawbacks such as the need to move the position of the switch, which requires time for adjustment.

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the conventional technology, to enable the detection of sagging even if there are differences in the height of the workpiece surface, and to ensure that the accuracy of sagging bulge detection is as low as the depth of the cross recess of the screw. To provide a screw floating detection device which enables high-accuracy screw floating detection without being affected by variations in bits, and eliminates the need to adjust the position of a limiter switch when replacing a bit.

[Summary of the invention]

The present invention includes a work surface detection member that detects the seat surface of the screw, and a screw suction pipe that contacts the head of the screw inside the work surface detection member, and limits the relative movement distance between the work surface detection member and the screw suction pipe. This system is designed to detect the floating of the seams almost directly.

[Embodiments of the invention]

Specific embodiments of the present invention will be described based on the drawings.

Fig. 1 is a cross-sectional view of the main part of an embodiment of the present invention, Fig. 2 is a cross-sectional view of the main part of the present invention showing a normal screw tightening state, and Fig. 3 is a cross-sectional view of the main part of the present invention showing a state in which a screw is loosened. FIG. 2 is a cross-sectional view of the main parts of the invention.

In Figures 1 to 3, 2 indicates Sera 1 to Play 1 to . Reference numeral 1 indicates an air cylinder serving as a lifting drive unit, and reference numeral 3 indicates a guide column 11. Both the air cylinder 1 and the guide column 3 are connected to the cellar 1 to
Fixed to play 1-2. 5 is guide column 3
A mount 14 that is slidable along the mount 1-5 is a power driver fixed to the mount l-5, and 6 is a piston rod of the air cylinder 1 that moves the mount 5 up and down. 11.degree. is a drive bit that drives the screw 15 by the force of the power driver 4. 12 has an inner diameter slightly larger than the outer diameter of the drive pinot 1-11, and its tip contacts the head of the screw 15 to detect the height of the screw 15.
This is a screw suction pipe with a suction function.

Reference numeral 7 denotes a spring serving as an elastic body provided so as to always urge the screw suction pipe 12 into close contact with the mount 5 due to an elastic force. "O is a switch holder fixed to the screw suction pipe 12, 16 is a spring that is an elastic body, 13 has an inner diameter slightly larger than the outer diameter of the screw suction pipe 12, and its tip is in contact with the work surface for detection. It is a pipe-shaped work surface detection member, and the work surface detection member 13 is always biased toward the work surface side (lower side in FIG. 1) by a spring 16. The inner diameter of the work surface detection member 13 is the same as that of the screw 15.
is larger than the maximum diameter of the head. 20 is a sensor piece attached to the work surface detection member 13. Reference numeral 9 denotes a limiter 1 to a switch that detects the position of the sensor piece 20 when the screw 15 is normally tightened to the workpiece and outputs a signal regarding the relative movement distance between the workpiece surface detection member 13 and the screw suction pipe 12. A Y pipe 14 is fixed to the set plate 2 and serves to stop screws from being supplied under pressure from a screw supply section (not shown).

8 is a suction port provided at the head of the screw suction pipe 12, and is connected to a negative pressure generation source (not shown). When the work surface detection member 13 is lowered at the start of screw tightening work, the screw 15 of the Y pipe 14 is moved to the screw suction pipe 1 by its negative pressure.
It is designed to closely suction the tip part 12a of No. 2. 1
8 is the workpiece, 17 is the stupid hole drilled in the workpiece 18, 1
9 is a screw hole.

In the above configuration, when compressed air is supplied to air cylinder 1 to tighten screws from the state shown in Figure 1, screws 1 to
The engine rod 6, the mount 1 5, the power driver 4 and the drive bit 1] begin to descend. As the power lever 4 descends, the screw suction pipe and the workpiece surface detection member 13, which are biased by the springs 7 and 16, also descend. At this time, the power driver 4 starts rotating and sucks air from the suction port 8 connected to a negative pressure generation source (not shown). This air passes through a gap 11 between the screw suction pipe and the drive pill and suctions the head of the screw 15. Furthermore, drive bit 1
1. The screw suction pipe 12, work surface detection member 13, etc. continue to descend until the ground port 1 at the lower end of the work surface detection member 13 is reached.
3a comes into contact with the work surface 18a. At this point, the workpiece surface detection member 13 stops descending, but the drive bit plate 12, switch holder [O], limit switch 9, etc. continue to descend further, and as shown in FIG. Enter 17 and tap hole 19 of workpiece 18
When it is screwed in correctly, the live pin I-
1 1. , the screw suction pipe 12 and the like stop descending, and at the same time, the rotation of the power driver 4 is also stopped. At this time, the limiter switch 9 detects the sensor piece 20 since no screw lifting occurs, and outputs a signal indicating that the screw is properly tightened. On the other hand, if the screw 15 is floating on the workpiece 18 without being completely tightened as shown in FIG. 3, the relative distance between the detection position of the limit switch 9 and the upper end position 20a of the sensor piece 20 is , the limit switch 9 cannot detect the sensor piece 20 and does not output a signal. That is, if a signal is output from the switch 9 to the limiter l, the screw 15 is properly tightened, and if no signal is output, it can be detected that the screw 15 is loose.

Incidentally, in the embodiment described in -H, a pipe is used as the work surface detection member, but a rod-shaped member may also be used.

[Summary of the invention]

According to the present invention, when tightening a workpiece, the difference in height between the surface and the screw head is detected by the relative distance between the screw suction pipe and the workpiece surface detection pipe, so variations in the depth of the cross recess of the screw can be detected. Highly accurate screw floating detection can be performed without being affected. Furthermore, since the bit is not involved in thread lifting, there is no need to adjust the position of the limit switch when replacing the bit, reducing loss time when replacing the bit and improving the efficiency of thread tightening work.

[Brief explanation of the drawing]

Fig. i is a sectional view of a main part showing a state in which the same lifting occurs as in Fig. A; 1 is the lifting mechanism, 4 is the power driver, and 5 is the mount 1.
, 7 is an elastic body, 9 is a switch to the limiter 1, 12 is a screw suction pipe, 13 is a work surface detection member, and 16 is an elastic body. Name of patent applicant Hitachi Koki Co., Ltd.

Claims (1)

[Claims] A lifting drive unit, a mount that moves up and down by the lifting drive unit, and a power driver fixed to the mount that can move up and down and is biased toward the work surface by an elastic body, and whose tip is a screw head. a screw suction pipe that suction-holds the screw by contacting the screw suction pipe; a limit switch fixed to the screw suction pipe; and a limit switch that is movable up and down with respect to the screw suction pipe and is biased toward the work surface by an elastic body; a workpiece surface detection member that can come into contact with the tightening surface of the workpiece to which the screw is being tightened, and when the screw tightening is completed, the limit switch is activated by relative movement of the screw suction pipe and the workpiece surface detection member, and the screw floats. A screw lifting detection device for an automatic screw tightening machine, characterized in that the limit switch is sometimes placed in a position where it is not activated.