JPH04343696A - Holding device - Google Patents

Abstract

PURPOSE:To provide a compact holding device generating strong holding force and surely detecting an object to be held. CONSTITUTION:Holding claws 2 are provided radially from the holding center, a drive source 5 is provided in the holding center direction, and they are connected via links 3 for moving the output shaft of the drive source 5 synchronously with the holding claws 2. Sensors 8 are fitted to the holding claws 2. The output of the drive source is transferred near the portions of the holding claws 2 holding an object to be held via the links 3, the holding sections attain the maximum holding force, and a holding device can be miniaturized and made lightweight.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gripping device attached to an industrial robot or the like for transferring several types of cylindrical workpieces having different diameters.

0002

2. Description of the Related Art A conventional device of this kind, as described in Utility Model Publication No. 15106/1980, uses a single drive source to operate one of a plurality of gripping claws, and this operation is controlled by a link mechanism. This signal is transmitted to a plurality of other gripping claws to open and close the gripping claws. In addition, in order to confirm the object to be grasped, a detector was installed in the gripping claw to directly detect the object to be grasped, or a method was used in which a simple method was used to detect pressure changes inside the fluid cylinder of the drive source. .

0003

[Problem to be Solved by the Invention] The purpose of the above-mentioned prior art is to grip a lightweight work such as a printed circuit board,
In order to grip a heavy workpiece, the link mechanism for transmitting the force of the driving source requires mechanical rigidity, which has the disadvantage of increasing the size of the entire device. In addition, regarding the detection of the grasped object, when directly detecting the grasped object with a detector, it may not be possible to detect the grasped object due to the condition of the part where the grasped object and the grasping claw come into contact, and it may not be possible to detect the grasped object due to changes in pressure inside the fluid cylinder. This method has the disadvantage that an erroneous signal is output when the gripping claws are mechanically restrained at an abnormal position, for example, before gripping the workpiece is completed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and to provide a gripping device that is compact and generates a strong gripping force.

[0005]

[Means for Solving the Problems] In order to achieve the above object, a plurality of gripping claws and a driving source are provided, the gripping claws are provided radially from the gripping center, and the driving source is provided in the direction of the gripping center axis. The output shaft of the drive source is connected to each of the gripping claws via a link that enables the gripping claws to open and close synchronously, so that a gripping force is directly generated in the gripping claws.

Furthermore, when the object to be gripped is a metal object, a conductor is installed at the tips of two or more of the gripping claws in order to confirm the gripping state.

[0007]

[Operation] When the fluid supply to the drive source is simultaneously switched and moved forward and backward, the gripping claws connected to the output shaft via a link radially approach or separate from each other synchronously from the gripping center.

As shown in FIG. 4, the gripping force (F) of the device also increases as the gripping diameter (y) of the workpiece increases and the weight increases. As shown in Figure 2, the maximum force is generated at the part where the claw grips the workpiece. Further, when the object to be grasped is a metal object, when the object to be grasped is grasped, the conductor is short-circuited by the object to be grasped, and a current flows through the conductor installed at the tips of the two or more gripping claws. This makes it possible to confirm that the object to be grasped has been grasped.

[0009]

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

Reference numeral 1 is attached to the tip of the wrist of an industrial robot or the like. An air cylinder 5 is attached to the lower surface of the base 1 so that a piston 7 moves in the direction of the central axis of the base 1 on a plane parallel to the lower surface of the base 1. The gripping claws 2, 2a to 2c are fixed to one end of the piston 7 via a link 3. Two conductors 8 are attached to the tips of the gripping claws 2. When switching the air supply to each air cylinder 5 and moving the piston 7 forward or backward, each gripping claw 2, 2a
2c move toward or away from each other radially from the center of the base plate. At this time, the gripping claws 2, 2a to 2c are connected to the piston 7 via the links 3, 3a to 3c, and therefore open and close in synchronization. Therefore, even if the inner diameter of the object to be gripped 9 changes, the amount of movement of each of the gripping claws 2, 2a to 2c is the same, so that the object can be gripped with high accuracy with a constant center. Furthermore, each of the gripping claws 2, 2a to 2c has a large movement stroke, allowing a fairly wide range between the maximum workpiece and the minimum workpiece. And, in this example,
In order to grip the workpiece more stably, there are three gripping claws, and for this purpose, the piston 7 and each gripping claw 2, 2a
The attachment positions of the links 3, 3a to 3c in ~2c are shifted up and down for compactness, which is also a feature.

[0011] Now, to describe the gripping force of this device in comparison with the gripping forces of other gripping devices, the mechanism of this device is shown in Fig. 3.
The link mechanism is shown in , and the gripping force F is stopped as shown below, and from the Pythagorean theorem,

0012

[Math 1]

[0013] Differentiating the number 1 2x+(dy/dx)・2y=0 therefore

[0014]

[Math 2]

From equations 1 and 2,

[0016]

[Math 3]

[0017] From the amount of work

[0018]

[Math 4]

From equations 3 and 4,

[0020]

[Math 5]

[0021] Figure 4 is a graph of number 5.

[0022] This shows that as the diameter and weight of the gripping portion of the work increases, the gripping force increases accordingly. On the other hand, as shown in FIG. 5, the gripping force of conventional gripping devices has always remained constant even when the diameter and weight of the workpiece gripping portion has increased.

Furthermore, the gripping force generated in the workpiece holding section will be explained based on FIGS. 6 and 7. This device has the structure shown in Fig. 6, and the output of the drive unit is transmitted to the L1 section of the gripping claw, which is the workpiece gripping part, and the relationship between the position of the gripping claw and the gripping force is as shown in Fig. 8, and the workpiece gripping The maximum force is generated at
At the attachment part of the claw, the force is minimized, reducing damage to the drive part of the claw, and achieving an effective force transmission state. On the other hand, conventional gripping devices have a structure as shown in Figure 7, in which the force transmitted to the attachment part of the claw decreases as it approaches the tip of the jaw, and the force transmitted from the drive source to the workpiece gripping part decreases as it approaches the tip of the claw. It was inefficient, as the power was often reduced to less than half. As described above, it can be said that the present device is considerably more efficient than conventional devices in terms of the gripping force generated in the workpiece gripping section. Further, there is a potential difference in the conductor 8 installed on the gripping claw 2, and when an object made of metal is gripped, the conductor is short-circuited and a current flows. and,
This allows it to be detected that the object to be gripped is gripped.

As explained above, in this embodiment, the output of the air cylinder, which is the driving source, is generated in the gripping claws via the link, so there is no loss due to transmission, and a large gripping force can be obtained. Moreover, the gripping force near the gripping portion of the gripping claw is the greatest, and the structure is simple and can be made small and lightweight.

[0025]

Effects of the Invention According to the present invention, the output of the drive source is transmitted through the link to the vicinity of the gripping part of the gripping claw, so that the greatest gripping force can be obtained at the gripping part, so that the gripping device is small and lightweight. can be converted into Moreover, if the covering is metal,
Since the presence or absence of a workpiece is determined by the presence or absence of a current flowing through a conductor installed in the gripping claw, it is possible to prevent false detection of the presence or absence of a workpiece, thereby reducing malfunctions of the entire system and improving the operating rate.

[Brief explanation of drawings]

FIG. 1 is a front view of an embodiment of the present invention.

FIG. 2 is a plan view of FIG. 1;

FIG. 3 is a linkage mechanism diagram of the device.

FIG. 4 is a relationship diagram of the force generated in the workpiece gripping diameter of the gripping device.

FIG. 5 is a relationship diagram of forces generated in the workpiece gripping section of the gripping device.

FIG. 6 is a structural diagram of the gripping device.

FIG. 7 is a structural diagram of a conventional gripping device.

FIG. 8 is a diagram showing the relationship between the gripping portion and the force in the gripping claw of the gripping device.

FIG. 9 is a diagram illustrating the relationship between the gripping portion and the force in the gripping claws of the conventional gripping device.

[Explanation of symbols]

1: Base, 2a to 2c: Gripping claw, 3 and 3a to 3c: Link, 4: Lead wire, 5: Air cylinder, 6: Gripping rubber, 7: Piston, 8: Conductor, 9: Object to be grasped.

Claims (3)

[Claims] 1. A gripping device comprising a plurality of gripping claws, a link mechanism connecting the gripping claws so as to be able to open and close the gripping claws synchronously, and a drive section for opening and closing the grasping claws, wherein the drive section The output shaft of the drive unit is linked to the gripping claws in correspondence with each of the gripping claws so that the driving force of the gripping claws operates in the direction of the gripping center axis of the gripping claws so that each claw can open and close synchronously. A gripping device characterized in that the gripping device is connected via a. 2. The gripping claw is composed of at least three claws, and the connecting portion of the link to the drive unit and the connecting portion to the gripping claw are attached so as to be shifted in the direction of the gripping center axis of the gripping claw. The gripping device according to claim 1, characterized in that: 3. When the gripped object is metal, the gripper is further provided with a means for confirming that the gripped object has been gripped by passing a current through a conductor installed in two or more of the gripping claws. The gripping device according to claim 1.