GB2292365A

GB2292365A - Automatic tool changer

Info

Publication number: GB2292365A
Application number: GB9416458A
Authority: GB
Inventors: Tomokazu Sendai
Original assignee: Nitta Corp; Applied Robotics Inc
Current assignee: Nitta Corp; Applied Robotics Inc
Priority date: 1994-08-15
Filing date: 1994-08-15
Publication date: 1996-02-21
Anticipated expiration: 2014-08-15
Also published as: GB9416458D0; HK96397A; SG42955A1; GB2292365B

Abstract

An automatic tool changer comprises a first unit 1 and a second unit 2. One of the units has a rotatable cam 4 with an engaging portion 40. The other unit is provided with an engaging pin 20. Engagement and disengagement between the engaging portion 40 and the engaging pin 20 along with a rotation of the cam 4 allows the first unit 1 and the second unit 2 to couple together and separate from each other. Furthermore, the cam 4 is provided with a protrudent part 5, which prevents accidental disengagement of the units 1, 2. <IMAGE>

Description

AUTOMATIC TOOL CHANGER The present invention relates to an automatic tool changer or coupling comprising a first unit and a second unit releasably connectable to the first unit.

Such automatic tool changers are disclosed in the Japanese Patent Application Laid-Open No. 63-269293, for example.

The automatic tool changer disclosed therein is illustrated in Fig. 7. This automatic tool changer comprises a first unit 1 and a second unit 2. The first unit 1 is attached to an arm A of a robot, while the second unit 2 to be connected to a tool is disposed on a bench D when it is separated from the first unit 1.

Separation or connection of the first and second units 1, 2 is achieved by feeding air into connection and separation ports 30, 31 of a cylinder 3 disposed in the first unit 1, which causes an output shaft 32 to extend or contract so as to give a cam 4 a to-and-fro rotation.

The cam 4, which is shown in Figs. 7 and 8, is rotatably attached to the first unit 1 by means of a rotary axis 39. As shown, an engaging portion 40 of cam 4 is divided into two parts. These two parts are divided by a part where the distance between the rotary axis 39 and the part is equal to the distance a between the rotary axis 39 and a contacting point P of the engaging pin 20 and the cam 4 at the time of a normal contact of the first and second unit 1, 2. The part at a distance from the rotary axis 39 larger than the distance a is referred to as a large part 42, while the other part which is at a distance from the rotary axis 39 which is shorter than the distance a is referred to as a small part 41.

Therefore, when the cam 4 is rotated and drawn outwardly, in the midst of this turning movement, the cam 4 and the engaging pin 20 come to engage stably with each other at a place where the contacting point P of the engaging portion 40 is slightly beyond the engaging pin 20.

However, as shown in Fig. 9, for example, if foreign matter D is caught between the engaging portion 40 and the engaging pin 20, the automatic tool changer described above provides an imperfect engagement. Under these circumstances any inadvertent large external impacts may cause the imperfect engagement to fail and the second unit 2 to drop from the first unit 1, as shown in Fig.

10.

The present invention seeks to alleviate at least some of the aforementioned problems and to provide an automatic tool coupling or changer capable of preventing inadvertent release of a second unit from a first unit even if the engagement of coupling elements (for example, a cam and an engaging pin) is not perfect, and capable of providing a firm coupling.

To achieve the object, the present invention provides an automatic tool coupling or changer which comprises a first unit and a second unit. On one of the two units a cam, rotatable about an axis and having an engaging portion, is provided, while an engaging pin is provided on the other unit. Engagement and disengagement between the engaging portion and the engaging pin along with the rotating movement of the cam allow the first and second units to be connected together or separated from each other. The engaging portion comprises a large part and a small part. These two parts are divided by a part where the distance from the rotary axis is equal to the distance between the rotary axis and the contacting point of the engaging pin and the cam at the time of a normal contact of the first and second units.Furthermore the small part is provided with a protrudent part, and the distance between the rotary axis and a furthest portion of the protrudent part is shorter than that between the rotary axis and the contacting point.

The protrudent part is preferably provided with a straight part and the distance between the straight part and the rotary axis increases gradually in the direction from the large part toward the small part.

Since the present invention is constituted as described above, even if there is imperfect engagement between the engaging portion of the cam and the engaging pin and an impact of a large external force (such as a force to separate the second unit from the first unit) is applied to the second unit, the protrudent part and the engaging pin come to engage with each other, thereby preventing the second unit 2 inadvertently dropping from the first unit 1.

Embodiments of the present invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of an embodiment of the automatic tool changer according to the present invention.

Fig. 2 is a sectional view of the automatic tool changer shown in Fig. 1.

Fig. 3 is a diagram showing a state of engagement and that of disengagement between an engaging portion of a cam and an engaging pin in the automatic tool changer.

Fig. 4 is a diagram showing the relation between the cam and the engaging pin in an imperfect engagement.

Fig. 5 is a diagram showing a coupling state of the first and second units wherein foreign matter is caught between the engaging portion of the cam and the engaging pin.

Fig. 6 is a diagram showing an engagement between the engaging pin and the protrudent part of the cam.

Fig. 7 is a sectional view of a conventional automatic tool changer.

Fig. 8 is a diagram showing a state of engagement and that of disengagement between an engaging portion of a cam and an engaging pin in the conventional automatic tool changer shown in Fig. 7.

Fig. 9 is a diagram showing a coupling state of the first and the second units wherein foreign matter is caught between the engaging portion of the cam and the engaging pin in the conventional automatic tool changer shown in Fig. 7.

Fig. 10 is a diagram showing a state wherein, in the conventional automatic tool changer, the engagement between the engaging portion of the cam and the engaging pin fails and the second unit drops from the first unit DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the accompanying drawings, an embodiment of the present invention is described further.

An example automatic tool changer of the present invention includes a first unit 1 and a second unit 2, as shown in Fig. 1. The first unit 1 is attached to an arm A of a robot, while the second unit 2 to be connected to a tool is disposed on the bench D. As shown in Figs. 1 and 2, the first and the second units are designed to connect with each other in such a way that a protrusion 11 projecting from a connecting surface of the first unit 1 is put into a recess 21 of the second unit.

A recess 12 in the protrusion 11 defining an inner face thereof is provided with a double action cylinder 3 and a cam 4 as shown in Fig. 2. Feeding air to connection and separation ports 30, 31 of the cylinder 3 allows an output shaft 32 to extend or contract to rotate the cam about a rotary axis 39.

As shown in Fig. 3, the cam 4 is made of a thick plate in an approximately sector shape. A round portion of the cam 4 defines an engaging portion 40 to engage with an engaging pin 20, which is to be described later. The cam 4 is designed to project out from and locate in an opening 10 provided on the first unit 1 and this is illustrated by a solid line and a twin dot chain line in Fig. 3. The engaging portion 40 of the periphery of cam 4 has a large part 42 and a small part 41. These two parts are divided by a part where the distance from the rotary axis 39 is equal to the distance a between the rotary axis 39 and the contacting point P of the engaging pin 20 and the cam 4 at the time of normal contact of the first and second units 1, 2.In the large part 42, the distance from the rotary axis 39 is longer than the distance a and, in the small part 41, the distance from the rotary axis 39 is shorter than the distance a. Furthermore the small part 41 includes a protrudent part 5, and the distance b between the rotary axis 39 and a furthest portion of the protrudent part 5 is shorter than the distance a.

The protrudent part 5 of this embodiment is provided with a straight part 50, and the distance between the straight part 50 and the rotary axis 39 increases gradually in the direction from the part 42 toward the part 41, as shown in Fig. 4. When the engagement between the engaging portion 40 and the engaging pin 20 is imperfect, the distance c between the rotary axis 39 and a furthest point of the protrudent part 5 in the direction X which is orthogonal to the direction Y which is, in other words, the direction of separation of the first and second units 1, 2, is larger than the distance between the rotary axis 39 and the engaging pin 20 in the same direction.

As shown in Fig. 2, the cylinder 3 is provided with a compression spring 33 at the side of the connecting port 30 and a shaft 36 at its rear end. The output shaft 32 and the shaft 36 have cams 4 at the respective ends and the cams 4 are attached thereto by means of respective pins. Extension and contraction of the output shaft 32 causes the cams 4 to project out of and hide into respective openings 10 of the first unit 1.

Portions of the unit 2 corresponding to the openings 10 of the unit 1 are provided with respective pins 20. As illustrated by solid lines in Figs. 2 and 3, when the cams 4 project out or the openings 10, the cams 4 and the pins 20 are respectively engaged with each other to provide a proper coupling of the first and second units 1, 2. On the other hand, when the cams 4 respectively hide into the openings 10 as illustrated by double dot chain lines in Figs. 2 and 3, the engagement between the cams 4 and the pins 20 are released to allow separation of the second unit 2 from the first unit 1.

Since the automatic tool changer of the present invention is constituted as described above, the present invention has the following advantages. The protrudent part 5 of the engaging portion 40 of the cam 4 prevents an inadvertent drop of the second unit 2 out of the first unit 1.

Namely, when a foreign matter is caught between the engaging portion 40 of the cam 4 and the engaging pin 20 and the engagement between the portion 40 and the pin 20 is imperfect, as shown in Fig. 5, and a large impact of an external force is applied to the second unit 2, the second unit 2 is about to drop out of the first unit 1 and separates slightly therefrom.

However, as clearly shown in Fig. 6, due to the existence of the protrudent part 5, the engaging pin 20 immediately engages with the straight part 50 of the protrudent part 5. More specifically in Fig. 6, the circumferential face of the engaging pin 20 is contacting with the round small part 41 as well as the straight part 50. Thus, an inadvertent drop of the second unit 2 out of the first unit 1 will not happen.

The angle between the edge side 43 and the straight part 50 of the protrudent part 5 is not limitative. Furthermore, the shape of the protrudent part 5 is not limited to an approximate triangle, but any appropriate shape may be employed.

As described above, the present invention provides an automatic tool changer capable of preventing an inadvertent drop of the second unit from the first unit even if the engagement of the connecting device, or the cam and the engaging pin in this embodiment, is imperfect.

Claims

1. An automatic tool changer comprising a first unit and a second unit, one of said units being provided with a cam rotatable about an axis and having an engaging portion and the other unit being provided with an engaging pin such that rotation of the cam and engagement and disengagement of the engaging portion and the engaging pin permit coupling and separation of the units, wherein the engaging portion of the cam includes a large part and a small part separated by a part located at a distance from the rotary axis which is equal to that between the rotary axis and a contacting point of the engaging pin and cam at the time of operative coupling of the first and second units, said large part being located at a distance from the rotary axis which is greater than that between the rotary axis and the contacting point and the small part being located at a distance from the rotary axis which is shorter than that between the rotary axis and the contacting point, and the small part being provided with a protrudent part having an extremity located at a distance from the rotary axis which is shorter than that between the contacting point and the rotary axis.

2. An automatic tool changer according to Claim 1 wherein the protrudent part has a straight part and the distance between the straight part and the rotary axis increases in the direction away from the large part and toward the small part.

3. An automatic tool changer according to Claim 1 or 2 wherein one of the units is provided with two rotatable cams and the other unit has two engaging pins.

4. An automatic tool changer substantially as hereinbefore described with reference to, and as illustrated in, any one of the accompanying Figures 1 to 6.