Industrial robot - Patent Review 3985238

What is claimed are:

1. An industrial robot having a multiple articulated arm mechanism, wherein at least two separate arms, or a main arm (A2) and a subsidiary arm (A3) are operable in a common plane, the industrial robot is characterized in that the main arm (A2) is fixedly connected at its base end to a second joint shaft (B2) coupled to a power unit so that the main arm is rotatable around the axis of the second joint shaft; the subsidiary arm (A3) is fixedly connected at its base end to a third joint shaft (B3) rotatably mounted on the forward end of the main arm (A2) so that the subsidiary arm is rotatable around the axis of the third joint shaft; a sun gear (Sc) is rotatably mounted on the second joint shaft (B2); in engagement with said sun gear, a planet gear (Pc) is rotatably mounted on a fixed shaft (11c) arranged in a suitably selected longitudinal position of the main arm (A2); an intermediate gear (Mc) is rotatably mounted on said fixed shaft (11c) and securedly connected to said planet gear (Pc) so that they are rotatable together; a transmission gear (Tc) fixedly mounted on said third joint shaft (B3) is operatively connected to the intermediate gear (Mc) through a connecting rod so that the second and third joint shafts (B2) and (B3) are connected to each other by way of the stretching movement epicyclic gear system (Ec) consisted of said gears (Sc, Pc, Mc and Tc); and the gear ratio among said gears (Sc, Pc, Mc and Tc ) are so selected as to satisfy a relation of (t2 .times. t4)/(t1 .times. t3) = 2 (wherein, t4, t3, t2 and t1 represent the number of teeth carried on the gears Sc, Pc, Mc and Tc, respectively, in this order), so that upon transmitting power to the second joint shaft B2 to swing the main arm (A2) up or down around the axis of the second joint shaft (B2), while the subsidiary arm (A3) can be swung down or up, or swung in the opposite direction, for an equal angle in the common plane.

2. An industrial robot having a multiple articulated arm mechanism, wherein at least a primary arm and a secondary arm are operable in a common plane, the industrial robot is characterized in that the primary arm is fixedly connected at its base end to a primary joint shaft coupled to a power unit so that the primary arm is rotatable around the axis of the primary joint shaft the secondary arm is fixedly connected at its base end to a secondary joint shaft rotatably mounted on the forward end of the primary arm so that the secondary arm is rotatable around the axis of the secondary joint shaft; a sun gear is rotatably mounted on the primary joint shaft; in engagement with said sun gear, a planet gear is rotatably mounted on a fixed shaft arranged in a suitably selected longitudinal position of the primary arm; an intermediate gear is mounted on said fixed shaft and securedly connected to said planet gear so that these gears are rotatable together; a transmission gear fixedly mounted on the secondary joint shaft is operatively connected to the intermediate gear through a connecting rod so that the primary and secondary joint shafts are connected to each other by way of the swing-up and -down movement epicyclic gear system for the secondary arm consisted of said sun gear, planet gear, intermediate gear and transmission gear; and the gear ratio among said gears are so selected as to satisfy a relation of (t1' .times. t3')/(t2' .times. t4') = 1 (wherein, t4', t3', t2' and t1' represent the number of teeth carried on the sun gear, planet gear, intermediate gear and transmission gear, respectively, in this order), so that upon transmitting power to one of said two joint shafts the arm mounted on the other joint shaft can be swung up or down around the axis of said one of joint shafts, while the arm mounted on said the other arm can be shifted parallel in the common plane without changing its absolute angular position.

3. An industrial robot having a multiple articulated arm mechanism, wherein at least two separate arms, or a subsidiary arm (A3) and grasping arm (A4) are operable in a common plane, the industrial robot is characterized in that the subsidiary arm (A3) is fixedly connected at its base end to a third joint shaft (B3) coupled to a power unit so that the subsidiary arm is rotatable around the axis of the third joint shaft (B3); the grasping arm (A4) is fixedly connected at its base end to a fourth joint shaft (B4) rotatably mounted on the forward end of the subsidiary arm (A3) so that the grasping arm (A4) is rotatable around the axis of the fourth joint shaft (B4); a sun gear (Sf3) is rotatably mounted on the third joint shaft (B3); in engagement with said sun gear, a planet gear (Pf3) is rotatably mounted on a fixed shaft (11f3) arranged in a suitably selected longitudinal position of the subsidiary arm (A3); an intermediate gear (Mf3) is mounted on said fixed shaft (11f3) and securedly connected to said planet gear (Pf3) so that these gears (Mf3) and (Tf3) are rotatable together; a transmission gear (Tf3) fixedly mounted on the fourth joint shaft (B4) is operatively connected to the intermediate gear (Mf3) through a connecting rod so that the third and fourth joint shafts (B3) and (B4) are connected to each other by way of the swing-up and -down movement epicyclic gear system (Ef3) for the grasping arm consisted of said gears (Sf3, Pf3, Mf3 and Tf3); and the gear ratio among said gears (Sf3, Pf3, Mf3 and Tf3) are so selected as to satisfy a relation of (t1' .times. t3')/(t2' .times. t4') = 1 (wherein, t4', t3', t2' and t1' represent the number of teeth carried on the gears Sf3, Pf3, Mf3 and Tf3, respectively, in this order), so that upon transmitting power to the third joint shaft (B3) the subsidiary arm (A3) can be swung up or down around the axis of the third joint shaft (B3), while the grasping arm (A4) can be shifted parallel in the common plane without changing its absolute angular position.

4. An industrial robot having a multiple articulated arm mechanism, wherein at least a primary arm and a secondary arm are operable in a common plane, the industrial robot is characterized in that the primary arm is fixedly connected at its base end to a primary joint shaft coupled to a power unit so that the primary arm is rotatable around the axis of the primary joint shaft the secondary arm is fixedly connected at its base end to a secondary joint shaft rotatably mounted on the forward end of the primary arm so that the secondary arm is rotatable around the axis of the secondary joint shaft; a sun gear is rotatably mounted on the primary joint shaft; in engagement with said sun gear, a planet gear is rotatably mounted on a fixed shaft arranged in a suitably selected longitudinal position of the primary arm; an intermediate gear is mounted on said fixed shaft and securedly connected to said planet gear so that these gears are rotatable together; a transmission gear fixedly mounted on the secondary joint shaft is operatively connected to the intermediate gear through a connecting rod so that the primary and secondary joint shafts are connected to each other by way of the swing-up and -down movement epicycle gear system for the secondary arm consisting of said sun gear, planet gear, intermediate gear and transmission gear; and the gear ratio among said gears are so selected as to satisfy a relation of (t1' .times. t3')/(t2' .times. t4') = 1 (wherein, t4', t3', t2' and t1' represent the number of teeth carried on the sun gear, planet gear, intermediate gear and transmission gear, respectively, in this order); a gear is rotatably mounted on the arm mounted on one of said joints so that it is operative in association with the motion transmission gear; and said gear is fixed to a grasping mechanism so that upon transmitting power to the other joint shaft to swing the other arm up or down around the axis of said other joint shaft, the grasping mechanism mounted on said one of arms can be moved together with said the other arm without twisting.

5. An industrial robot having a multiple articulated arm mechanism, wherein at least two separate arms, or a subsidiary arm (A3) and a grasping arm (A4) are operable in a common plane, the industrial robot is characterized in that the subsidiary arm (A3) is fixedly connected at its base end to a third joint shaft (B3) coupled to a power unit so that the subsidiary arm is rotatable around the axis of the third joint shaft (B3); the grasping arm (A4) is fixedly connected at its base end to a fourth joint shaft (B4) rotatably mounted on the forward end of the subsidiary arm (A3) so that the grasping arm (A4) is rotatable around the axis of the fourth joint shaft (B4); a sun gear (Sh3) is rotatably mounted on the third joint shaft (B3); in engagement with said sun gear, a planet gear (Ph3) is rotatably mounted on a fixed shaft (11h3) arranged in a suitably selected longitudinal position of the subsidiary arm (A3); an intermediate gear (Mh3) is mounted on said fixed shaft (11h3) and securely connected to said planet gear (Ph3) so that these gears (Mh3) are rotatable together; a transmission gear (Tf3) fixedly mounted on the fourth joint shaft (B4) is operatively connected to the intermediate gear (Mh3) through a connecting rod so that the third and fourth joint shafts (B3) and (B4) are connected to each other by way of the swing-up and -down movement epicyclic gear system (Eh4) for the grasping arm consisted of said gears (Sh3, Ph3 and Th3); and the gear ratio among said gears (Sh3, Ph3, Mh3 and Th3) are so selected as to satisfy a relation of (t1' .times. t3')/(t2' .times. t4') = 1 (wherein, t4', t3', t2' and t1' represent the number of teeth carried on the gears Sh3, Ph3, Mh3 and Th3, respectively, in this order); a gear (40h4) is rotatably mounted on the grasping arm (A4) so that it is operative in association with the motion transmission gear (Th3); and said gear (40h4) is fixed to the grasping mechanism (A5) so that upon transmitting power to the third joint shaft (B3) to swing the subsidiary arm (A3) up or down around the axis of the third joint shaft (B3), the grasping mechanism (A5) mounted on said grasping arm (A4) can be moved together with the subsidiary arm (A3) without twisting.

6. An industrial robot provided with a multiple articulated arm mechanism, wherein an arm (A3) is connected to a main arm (A2) which is connected to a base arm (A1) which is connected to the power unit at the first joint shaft (B1), and each of said arms (A1, A2 and A3) is rotatable in a common plane around the axis of a corresponding one of first, second and third joint shafts, (B1, B2 and B3), the industrial robot being characterized in that:

a planet gear (P2d) is fixedly mounted on the second joint shaft (B2) which is rotatably mounted on the forward end of said base arm (A1);

a sun gear (Sc) is rotatably mounted on said second joint shaft (B2);

a first joint shaft (B1) is fixedly mounted on the base end of said base arm (A1);

drive gear (Sd and C) are rotatably mounted on said first joint shaft (B1);

a drive gear (D) is fixedly mounted on said first joint shaft (B1);

the drive gear (Sd) is fixedly mounted on a base block (X) and operatively engages said sun gear (Sc) and the drive gear (C) engages said planet gear (P2d) so that the first joint shaft (B1) is connected to the second joint shaft (B2) by way of the swing-up and-down movement epicyclic gear system (Ed) comprising said gears (Sc, Sd, P2d and C), for thereby connecting the second joint shaft (B2) to the power unit; and

the gear ratio between said gears (Sc, Sd, P2d and C) is so selected as to satisfy a relation of (t6 .times. t7)/(t8 .times. t4) = 1 (wherein, t4, t6, t7 and t8 represent the number of teeth carried on the gears Sc, Sd, P2d and C, respectively, in this order), so that upon rotating the drive gear (D) the base arm (A1) can be swung around the first joint shaft (B1) to thereby rotate the second joint shaft (B2) around the first joint shaft (B1) for swinging up or down the main arm (A2) having the planet gear (P2d) fixed thereon around the second joint shaft (B2) for an angle, and simultaneously rotating the sun gear (Sc) around the first joint shaft (B1) to thereby swing the subsidiary arm (A3) having a transmission gear (Tc) fixed thereon and associated with said sun gear (Sc) up or down, or in the same direction as the main arm (A2), for an angle in the common plane.

7. An industrial robot provided with a multiple articulated arm mechanism according to claim 6, wherein a planet gear (P1d) engages the sun gear (Sc) with the drive gear (Sd), the planet gear (P1d) being rotatably mounted on the second joint shaft (B2) so that it is engaged with the drive gear (Sd) which is loosely mounted on the first joint shaft (B1), said planet gear (P1d) being securely connected to the sun gear (Sc) so that they are rotatable together, and the gear ratio between the gears (P1d, Sd, P2d and C) are so selected as to satisfy a relation of (t6 .times. t7)/(t5 .times. t8) = 1, wherein t5, t6, t7 and t8 represent the number of teeth carried on the gears (P1d, Sd, P2d and C), respectively, in this order.

8. An industrial robot provided with a multiple articulated arm mechanism according to claim 7, wherein a grasping arm (A4) is fixedly mounted on the forward end of the subsidiary arm (A3) and a grasping mechanism (A5) is mounted on said grasping arm (A4) so that, when the subsidiary arm (A3) is swung up or down for an angle, said grasping mechanism (A5) can be swung up or down, or can be swung in the same direction, for an equal angle in the common plane.

9. An industrial robot provided with a multiple articulated arm mechanism according to claim 7, wherein:

a fourth joint shaft (B4) is rotatably mounted on the forward end of the subsidiary arm (A3) and the grasping arm (A4) is fixedly mounted at the base thereof on said fourth joint shaft (B4) so that each of the arms (A1, A2, A3 and A4) is rotatable in a common plane around the axis of the corresponding joint shaft (B1, B2, B3 and B4);

sun gears (Sf and Sh) are rotatably mounted on the joint shaft (A1, A2 and A3);

planet gears (Pf and Ph) are rotatably mounted on the fixed shaft (11f and 11h) respectively so that they are engaged with said sun gears (Sf and Sh) respectively, said fixed shafts (11f and 11h) being arranged in a suitably selected longitudinal position of the arms (A1, A2 and A3);

intermediate gears (Mf and Mh) are mounted on said fixed shafts (11f and 11h), respectively, and fixedly connected to said planet gears (Pf and Ph) respectively so that these pairs of gears (Pf, Mf; Ph, Mh) are rotatable together;

transmission gears (Tf and Th) rotatably mounted on said joint shaft (B2 and B3) are operatively connected to said intermediate gears (Mf and Mh) respectively;

a transmission gear (Tf3) fixedly mounted on the fourth shaft (B4) is operatively connected to the intermediate gear (Mf3) in the subsidiary arm (A3);

a transmission gear (Th4) associated with the grasping mechanism (A5) is operatively connected to an intermediate gear (Mh3) in the subsidiary arm (A3), so that epicyclic gear systems (Ef and Eh) are arranged between the joint shafts (B1, B2, B3 and B4);

and the gear ratio between the gears (S, P, M and T) composing said epicyclic gear systems (Ef and Eh) are so selected as to satisfy a relation of (t1' .times. t3')/(t2' .times. t4') = 1 (wherein, t4', t3', t2' and t1' represent the number of teeth carried on the gears S, P, M and T, respectively, in this order) so that even when the arms (A1, A2 and A3) are swung up or down, the grasping arm (A4) can be shifted parallel without changing its absolute angular position and hence the grasping mechanism (A5) can be moved without changing its absolute twisting angle.

Description Submit all comments and votes

This invention relates to a so-called industrial robot which can grasp an object, transfer the same from a position to the other and perform a preselected series of actions for handling the object at that position and, more particularly, to a novel multiple articulated type industrial robot which can perform properly a wide variety of actions corresponding to those provided by the hand and arm of human body. To allow the best use of the space and provide a high efficiency operation, the robot has a compact construction by concentrating the control units for the various robot actions in a single position.

The conventionally known industrial robots are either of a circular cylindrical coordinates type or a spherical coordinates type. The circular cylindrical coordinates type robot carries a finger section which can be opened and closed, twisted and also swung in one direction. The arm section connected to said finger section can be moved linearly up and down as well as forward and backward, and also can be twisted about its axis. Whereas, the spherical coordinates type robot provides a combination movement in both the horizontal and vertical directions as well as the movement in the forward and backward directions.

Each of these prior art apparatuses has both merits and demerits for use as an industrial labor saving means. With these conventional industrial robots it can hardly be expected to carry out complex modes of movements corresponding to those of hand and arm of human body.

A short point which is commonly involved in both types of conventional robots and has to be specifically mentioned herein is that they require a considerably large installation space compared with their operation space. In these conventional robots the finger section is so arranged that it can be operated by a piston slidably received in a cylinder having a preselected length. With this arrangement, even when the robot finger section needs to be operated only within an angle of 180.degree. in the front side of the robot, a robot installation space equal to the forward and backward stroke of the arm section, or equal to the cylinder length, is required also in the rear side of the robot. In other words, the conventional robots require two times as large as installation spaced compared with its actual operation range.

The other disadvantages involved in the conventional robots are that the robot of circular cylindrical coordinates type has a too large vertical length at its central portion because the arm section needs to be moved in the vertical direction, and that the robot of spherical coordinates type can cover only a limited operation range because of a limited vertical swinging angle of the arm due to its configuration.

To eliminate these and other disadvantages of the conventional industrial robots an improved mechanism has been proposed heretofore, wherein the arm section is designed as an articulated arm so that it can additionally provide a stretching movement. However, this mechanism, which is provided with a lateral guide rail for the arm end for thereby attaining a reliable and smooth stretching movement of the arm section, is not very practical because of its complicated construction and limited movement.

The present invention is a result of a long and extensive studies which has been conducted in view of the foregoing for developing a novel industrial robot apparatus substantially free from said various disadvantages involved in the prior art industrial robots. The invention is directed to a mechanism belonging to a technical category which is quite different from the conventional robots in both construction and configuration.

It is a primary object of this invention to provide a multiple articulated type industrial robot which has a smooth and flexible movement resembling that of the upper limb of human body.

Another object of this invention is to provide such an industrial robot which has an almost equal operation space and installation space for thereby permitting the best use of the installation space.

Still another object of this invention is to provide an industrial robot which eliminates all the disadvantages involved in the conventional devices to provide excellent operation characteristics and allows a relative movement of the individual portions of the multiple articulated arm with a simple operation. This facilitates the setting work of the operation program.

A further object of this invention is to provide an industrial robot having a compact construction and a high efficiency operation by concentrating the control units thereof in a single position.

To attain these and other objects the present invention proposes a mechanism which is characterized in that a main arm and a subsidiary arm of equal length can be moved freely in a common plane. These arms are pivotably connected together end to end to form an articulated arm assembly. The whole arm assembly can be swung up and down by swinging up and down the base arm which is separately attached to the main arm. The articulated arm also provides a stretching movement, in which the forward end of the subsidiary arm can be moved toward and away from the base end of the main arm by use of an epicyclic gear system connecting the main arm to the subsidiary arm. In such a stretching movement the main arm alone is first swung up or down and then, by the action of the epicyclic gear system, the subsidiary arm is swung in the common plane and in the reverse direction for an equal angle with respect to the horizontal direction.

Another feature of this invention lies in that a grasping arm provided with a grasping mechanism is pivotably connected to the forward end of the subsidiary arm so that the grasping arm can be held in a preselected constant angular position irrespective of the swing-up and-down movement and stretching movement of the entire articulated arm. Besides, the apparatus of this invention can be swivelled in a horizontal plane intersecting, at right angles, the vertical plane in which the entire articulated arm swings up and down for stretching movement. Thus, the multiple articulated type robot of this invention can provide a three-dimensional movement.

Still another feature of this invention lies in that the grasping mechanism to be mounted on the grasping arm is so arranged as to be pivoted on the grasping arm shaft, for thereby maintaining the absolute inclination angle of the grasping arm irrespective of the stretching movement and swing-up and -down movement of the entire articulated arm. The entire articulated arm including said grasping arm can be swivelled in a substantially horizontal plane for thereby providing a three-dimensional movement.

To control the operation of such an articulated industrial robot in a simple and reliable manner, the motion transmission mechanism for the swing-up and -down movement and the stretching movement of the articulated arm as well as the motion transmission mechanism for the swing-up and -down movement and twisting movement of the grasping arm are respectively consisted of a gear train, each consisting of an epicyclic gear system, so that an improved smooth operation can be attained at the joint portions and the erroneous works which might occur due to the repeated usage can be minimized. Further, the construction of the robot can be made in compact by utilizing a connecting rod or rotary shaft in the gear trains so as to reduce the number of gears.

FIG. 1 is a partially fragmented perspective view of the entire industrial robot according to this invention;

FIG. 2 is a longitudinal sectional view of the main portion of the industrial robot according to this invention;

FIG. 3 is a partial elevation of the main portion shown in FIG. 2;

FIGS. 4, 5 and 6 are respectively partial enlarged views of the main portion shown in FIG. 2;

FIG. 7 is a view for explaining the operational principle of the multiple articulated arm according to this invention;

FIGS. 8, 9 and 10 are respectively views for explaining the operational principle of gear trains built into the multiple articulated arm; and

FIG. 11 is a schematic view for explaining the features of the multiple articulated arm.

The invention will be described in detail first, with reference to the preferred embodiments illustrated in FIGS. 1-6. As is seen from FIG. 1 the industrial robot of this invention consists of an articulated arm A, a pair of swivel base block Y and a fixed base block X. Said articulated arm A consists of a base arm A1, a main arm A2, a subsidiary arm A3, a grasping arm A4 and a grasping mechanism A5. The base arm A1 is much shorter compared with the main arm A2 and subsidiary arm A3 and swingable only in the vertical plane as will be stated later. The main arm A2 and subsidiary arm A3 are made much longer than the base A1 and have an equal length (see FIG. 2), and correspond to the arm of human body. The grasping arm A4 corresponds to the hand; while the grasping mechanism A5, to the finger portion of the human body. The arms A1, A2, A3 and A4 are connected together in the following manner:

To the base end of the base arm A1 is arranged a first joint shaft B1 (see FIGS. 2 and 4) which is connected to a power unit, to the forward end of the base arm A1 is arranged a second or shoulder joint shaft B2 to which is pivoted the main arm A2, to the forward end of the main arm A2 is arranged a third or elbow joint shaft B3 to which is pivoted the subsidiary arm A3 and to the forward end of the subsidiary arm A3 is arranged a fourth or wrist joint shaft B4 to which is pivoted the grasping arm A4. The arms A1, A2, A3 and A4 are freely pivotable around an axis of each corresponding joint shafts B1, B2, B3 and B4 in a common plane. To provide an ability of placing an object grasped by the grasping mechanism A5 in a preselected place in the preselected position and/or handling the same in that place in the preselected manner, the industrial robot of this invention has five individual operation gear trains provided therein:

1. The first operation gear train serves to transfer an object grasped by the grasping mechanism A5 towards and away from the fixed base block X in a horizontal plane. More specifically, the first gear train is a so-called stretching movement gear train which operates, when the main arm A2 pivoted on the second joint shaft B2 arranged at the base end thereof is swung up or down for a certain angle, to swing down or up the subsidiary arm A3 pivoted on the third joint shaft B3 in the common plane for an equal angle.

2. The second gear train contributes to transfer the object in a vertical direction. When the second joint shaft B2 is moved around the first joint shaft B1 and the main arm A2 is swung up or down around the second joint shaft B2 in a common plane for a certain absolute angle, or an angle measured from the horizontal direction, the subsidiary arm A3 also swings up or down around the third joint shaft B3 in the common plane for an equal absolute angle. In other words, the second operation gear train may be called a swing-up or -down movement gear train which serves to swing up and down the main arm A2 and subsidiary arm A3 as if they were a straight one-piece member.

3. The third and fourth gear trains are respectively a swing-up and -down movement gear train and a twisting movement gear train for both of the grasping arm A4 and grasping mechanism A5. More specifically, these gear trains serve to hold the grasping arm A4 and grasping mechanism A5 in a predetermined position for thereby grasping the object to be transferred in a desired position and handling the same in a preselected manner.

4. The fifth gear train serves to rotate the rotary base block Y for 360.degree. with respect to the fixed base block X so that the entire articulated arm as well as the object held by it can be rotated over 360.degree. in the horizontal plane.

According to this invention an articulated arm which corresponds to the arm and hand of human body and consisting of four arm portions is operated by means of above-described five separate operation gear trains. To facilitate the understanding of this invention the construction, operation and effect of the apparatus of this invention will be described hereinunder, especially in connection with said five operation gear trains.

First, the swivel gear train for swivelling the overall articulated arm A in a horizontal plane for 360.degree. will be described. Referring to FIG. 1, the swivel base block Y is mounted on the horizontal top surface of the fixed base block X so that the bottom surface of the swivel base block Y and the top surface of the fixed base block X are in contact with each other. The swivel base block Y can be swivelled for 360.degree. around a central vertical shaft (not shown) by means of a suitable drive mechanism. Between two support blocks 5 standing on either sides of the swivel base block Y is rotatably journalled the first joint shaft B1 of a suitable length. The articlated arm A is pivotably mounted on the first joint shaft B1. The overall swivel gear train is so arranged as to allow the rotary base block Y rotate horizontally together with the overall articulated arm A.

Next, the stretching movement gear train and swing-up and -down movement gear train will be described simultaneously. To facilitate the understanding of the operation of these gear trains, in the following description the expression of "rotation" of the arms and/or gears means that there is a visually perceivable difference in the position of the arms and/or gears before and after operation. In other words, the arms and/or gears are said to be rotated or not rotated depending on the change in their absolute angular position. For example, referring to the relationship between the subsidiary arm A3 and grasping arm A4, when the subsidiary arm A3 swings up and down, if the grasping arm A4 supported on the forward end of the subsidiary arm A4 is displaced together with the forward end of the subsidiary arm A3 while maintaining the horizontal position, then it will be said that the subsidiary arm A3 has been rotated, whereas the grasping arm A4 has not been rotated. So far as the relative position between the subsidiary arm A3 and the grasping arm A4 is connected, such an operation involves a change in the angular relation between these arms and hence both of the arms might seen to have been rotated. However, in the following description whether the arm and/or gear have been rotated or not will exclusively be judged based on the absolute angular position of the arm and/or gear.

Now the fundamental conditions for effecting said swing-up and -down movement and stretching movement will be considered with reference to FIG. 7 which illustrates the operation principle of the articulated arm according to this invention. In the position where the main arm A2 and subsidiary arm A3 are extending along a horizontal straight line as shown by a real line, the line extending between the center O2 of the second joint shaft B2 for the main arm A2 and the center 04 of O4 fourth joint shaft B4 arranged at the base end of the grasping arm A4 will be called a reference line. It will be apparent that every time when the grasping arm A4 is moved horizontally towards the center O2 of the second joint shaft B2 along said reference line, an equilateral triangle will be formed with a straight line extending along the reference line and having an arbitrary length as the base and the main and subsidiary arms A2 and A3 having an equal length as the oblique sides. Conversely, if the main and subsidiary arms A2 and A3 are moved relative to each other so that an equilateral triangle is defined by these arms and said reference line, then the grasping arm A4 will move horizontally along the reference line.

In FIG. 7 when the fourth joint shaft B4 of the grasping arm A4 is moved toward the position B4a as shown by the two-dotted chain line while maintaining the original absolute inclination of the grasping arm A4 irrespective of the stretching movement of the arms A3 and A4, the angle of rotation of the arms A2, A3 and A4 will be as follows:

Assuming that the second joint shaft B2 for the main arm A2 rotates counter-clockwise for an angle of .theta., then the third joint shaft B3 on which p, is pivoted the subsidiary arm A3 will be rotated in the same direction for an equal angle of - .theta..sub.1, while the fourth joint shaft B4 on which is pivoted the grasping arm A4 will remain unrotated. The same is true to the rotation in the reverse direction.

Next, the consideration will be directed to the operation in which all the arms A2, A3 and A4 are swung up and down while maintaining the relative positional relationship between the main and subsidiary arms A2 and A3 unchanged and also maintaining the absolute angular position of the grasping arm A4 unchanged. For example, when the fourth joint shaft B4 on which is mounted the grasping arm A4 is moved toward the position B4b as shown by the two-dotted chain line, if the second joint shaft B2 for the main arm A2 is rotated counter-clockwise for an angle of .theta.2, then the third joint shaft B3 on which is pivoted the subsidiary arm A3 will be rotated in the same direction for an equal angle .theta.2, while the fourth joint shaft B4 on which is pivoted the grasping arm A4 will be maintained unrotated.

The foregoing angular change (or absolute angular position) of each arm in the stretching movement and swing-up and -down movement will be summerized as follows:

______________________________________ Stretching Swing-up and-down movement movement Main arm A2 +.theta.1 +.theta.2 Subsidiary arm A3 -.theta.1 +.theta.2 Grasping arm A4 0 0 ______________________________________

To satisfy these conditions, an epicyclic gear system E having a special construction is arranged between every two adjacent joint shafts B. The individual gears are arranged in the special relationship to form epicyclic gear systems E. The function of these epicyclic gear systems will be described hereinunder with reference to FIG. 8 illustrating the operational principle of these gear systems.

In the illustration, the first joint shaft B1 fixed to the rotary base block Y carries a sun gear Sd fixed thereon and also rotatably carries a drive gear C of the stretching movement gear system and a drive gear D of the swing-up and -down gear system. The base arm A1 is integral with the drive gear D so that it operates in association with the drive gear D. Rotatably mounted on the base arm A1 is the second joint shaft B2 for the main arm A2, on which are rotatably mounted a sun gear Sc of the stretching movement gear system and a planet gear P1d which is integral with said sun gear Sc. The second joint shaft B2 also has an additional planet gear P2d fixedly mounted thereon. The planet gears P1d and P2d are engaged with the sun gear Sd and drive gear C, respectively. At a preselected longitudinal position on the main arm A2 is pivotably mounted a shaft 11C fixedly carrying a planet gear Pc and an intermediate gear Mc at the opposite ends thereof. The planet gear Pc is engaged with said sun gear Sc. On the forward end of the main arm A2 is fixedly mounted the third joint shaft B3 which pivotably supports the base end of the subsidiary arm A3, as well as a transmission gear Tc. In the gear train designed as above, the epicyclic gear system Ec for the stretching movement is consisted of the sun gear Sc, planet gear Pc, intermediate gear Mc and transmission gear Tc. These gears Sc, Pc, Mc and Tc are so designed as to have a gear ratio satisfying a relation of (t2 .times. t4)/(t1 .times. t4) = 2, wherein t4, t3, t2 and t1 represent the number of teeth carried on said gears Sc, Pc, Mc and Tc, respectively, in this order. The epicyclic gear system Ed for the swing-up and -down movement is consisted of a sun gear Sd, drive gear C, planet gears P1d and P2d. The gear ratio between these gears Sd, C, P1d and P2d satisfies a relation of (t6 .times. t7)/(t5 .times. t8) = 1, wherein t6, t8, t5 and t7 represent the number of teeth carried on said gears Sd, C, P1d and P2d, respectively, in this order.

Under these circumstances, while locking the sun gear Sd and base arm A1 or the drive gear D of the swing-up and -down movement gear system, if the drive gear C alone is rotated clockwise for one revolution (or -1 revolution), then the planet gear P2d and hence the joint shaft B2 for the main arm A2 will be rotated counter-clockwise for t8/t7 revolutions (.theta. revolutions). At this time the transmission gear Tc and hence the joint shaft B3 for the subsidiary arm A3 rotates for t8/t7 .times. [ 1-(t2 .times. t4)/(t1 .times. t3)] revolutions. This means that the joint shaft B3 for the subsidiary arm A3 rotates clockwise for t8/t7 revolutions, or -.theta. revolutions (because (t2 .times. t4)/(t1 .times. t3) equals 2 as mentioned previously). Compared with the Table set forth hereinbefore, it will be understood that these results satisfy the conditions for effecting the stretching movement.

On the other hand, while locking the sun gear Sd and drive gear C if the drive gear D of the swing-up and -down movement gear system is rotated counter-clockwise for one revolution (or 1 revolution), the base arm A1 will rotate around the first joint shaft B1, while the second joint shaft B2 will move around the first joint shaft B. As a result, the planet gear P2d and the second joint shaft B2 for the main arm A2 will rotate counter-clockwise for 1 + t8/t7 revolutions (or 1 + .theta. revolutions), and the planetary gear P1d simultaneously rotate for 1 + t6/t5. Under these circumstances, the drive gear Tc rotates for 1 + t8/t7 + [(t2 .times. t4)/(t1 .times. t3)] .times. (t6/t5 - t8/t7) revolutions. Since t6/t5 equals t8/t7, or t6/t5 - t8/t7 equals zero, the subsidiary arm A3 rotates counter-clockwise for 1 + t8/t7 revolutions (or 1 + .theta. revolutions). Compared with the Table set forth previously, it is apparent that this result satisfies the conditions for effecting the swing-up and -down movement. The foregoing stretching movement and swing-up and -down movement will be summerized as follows:

First, concerning the stretching movement. The power imparted from the not shown power unit to the drive gear C of the stretching movement gear system is transmitted to the planet gear P2d, or to the main arm A2 only, but not transmitted to the sun gear Sc. Since the gears belonging to the epicyclic gear system Ec are engaged with each other at a specially selected gear ratio, the swing-up or -down movement of the main arm A2 around the second joint shaft B2 for a certain angle will accompany a rotation of the transmission gear Tc fixedly mounted on the base end of the subsidiary arm A3 for a corresponding angle in the same plane. In this case the transmission gear Tc rotates for an angle equal to the main arm 2 in the direction opposite to the rotation of the main arm A2. Accordingly, the subsidiary arm A3 swings up or down for an angle which is reversed in direction but equal in amount to that of the swinging movement of the main arm A2. This means that the main arm A2 and the subsidiary arm A3 carry out a stretching movement in the common plane.

In the swing-up and -down movement, on the other hand, the power imparted from the not shown power unit to the drive gear D of the swing-up and -down gear system is transmitted to the base arm A1 fixed to the drive gear D, so that the base arm A1 swings around the first joint shaft B1. This moves the second joint shaft B2 around the first joint shaft B1, thereby rotating the planet gears P1d and P2d. In other words, upon swinging the main arm A2, the sun gear Sc rotates simultaneously. Since the gears Sd C, P1d and P2d are provided with preselected number of teeth, when the main arm A2 swings up or down around the second joint shaft B2 for a certain angle, the transmission gear Tc securedly mounted on the base end of the subsidiary arm A3 will be rotated for a corresponding angle. The direction and angle of rotation of the transmission gear Tc are truely equal to those of the main arm A2. Accordingly, the subsidiary arm A3 and main arm A2 swing up and down in the common plane, in the same direction and for an equal angle to the main arm A2. This means that the main arm A3 swing up and down just as if they were a one-piece member.

Now the practical construction of these stretching movement gear train and the swing-up and -down movement gear train will be described with reference to FIGS. 2, 4 and 5, wherein the components having substantially similar functions to those of FIG. 8 are designated by like reference symbols. As for the connection manner between the shafts, gears and arms, there is some difference between the principle view and embodiment as will be stated later. Nevertheless, as for the functions of these shafts, gears and arms, there is no difference between the principle view and the embodiment. In the shown embodiment the gear ratio between the sun gear Sc, planet gear Pc, intermediate gear Mc and transmission gear Tc, which compose the stretching movement gear train Ec, is equal to that described hereinbefore with reference to the principle view. The same is true to the sun gear Sd, drive gear C, planet gears P1d and P2d, which compose the swing-up and -down movement epicyclic gear system Ed.

As is seen from FIGS. 2 and 4, the first joint shaft B1 mounted on the swivel base block Y has a pair of similar base arms A1 and three separate gears Sd, C and D mounted on the first joint shaft B1 between said pair of base arms A1. The gears Sd and C have sleeves 10d and 10C, respectively, received in their inner center holes so that they are freely rotatable wih respect to the first joint shaft B1. The drive gear D and pair of base arms A1 are operatively coupled to the first joint shaft B1 by means of a spline 91 or a pin 91A so that, at the time when the drive gear D rotates, the first joint shaft B1 and the pair of base arms A1 start rotating simultaneously.

The sun gear Sd is fixed to the swivel base block Y by use of any suitable means, so that it is held in a constant position with respect to the swivel base block Y irrespective of the rotation of the first joint shaft B1. The drive gear C adapted to make said articulated arm perform a stretching movement is engaged with a gear (not shown) mounted on the output shaft of a suitable drive unit such as a pulse motor, and forms a starting member of the power transmission system for making the articulated arm A perform a stretching movement.

The drive gear D adapted to make the articulated arm A perform a swing-up and -down movement is connected to another drive unit in the similar manner as the drive gear C, forming the starting member of the swing-up and -down movement transmission system for the articulated arm A.

The second joint shaft B2 arranged at the base end of the main arm A2 is supported in the horizontal position by the forward ends of the pair of base arms A1, so that the second joint shaft B2 can be moved around the frist joint shaft B1 while being held in a horizontal position.

Between the pair of base arms A1 and the second joint shaft B2 are arranged a pair of sleeves 82 so that the second joint shaft can be rotated freely with respect to the base arms A1.

Now the main arm A2 which is a component of the multiple articulated arm A will be described. As is seen from FIG. 1 the main arm A2 extends along a line intersecting the first joint shaft B1 at right angles. The main arm A2 includes a cover 101 for enclosing the entire main arm A2, and a gear train which will be described later.

As is best seen from FIG. 4 the main arm A2 is mounted at its base end on the second joint shaft B2 so that they are fixed together by use of a pair of splines 92. Within a hollow internal portion of the main arm A2 is received a stretching movement gear train for transmitting the rotation of the drive gear C to the main arm A2 and subsidiary arm A3. In the longitudinal preselected position on the main arm A2 is arranged a fixed shaft 11c in parallel relation with the second joint shaft B2. The main arm A2 also carries on its forward end the third joint shaft B3 which extends parallel to the second joint shaft B2. The third joint shaft B3 is mounted on the main arm A2 by way of a pair of sleeves 83 (FIG. 5) so that the third joint shaft B3 is freely rotatable with respect to the main arm A2. The main arm A2 also carries an axially extending rotary shaft 12c. The rotary shaft 12c is mounted on the main arm A2 by use of a pair of sleeves 13c, 13c (FIGS. 4 and 5) so that it is freely rotatable.

In conjunction with the foregoing shafts are arranged the stretching movement gear train and a portion of the swing-up and -down movement gear train composed of the planet gears P1d, P2d, sun gear Sc, planet gear Pc, intermediate gear Mc, transmission gear Tc