[DESCRIPTION]

[invention Title]

AUTOMATIC PALLET CHANGER

[Technical Field]

The present invention relates to an automatic pallet changer, and more particularly, to an automatic pallet changer which supplies and withdraws hydraulic oil between a shaft which is integrally formed with a vane and a stopper for restricting rotation of the vane, so that the shaft formed with the vane is rotated by a pressure of the hydraulic oil, and also supplies and withdraws the hydraulic oil between a housing for accommodating the shaft and the stopper and upper and lower hydraulic plates of the shaft, so that the shaft is moved up and down by the pressure of the hydraulic oil and thus a pallet is organically interlocked with the movement of the shaft.

[Background Art] A mechanical apparatus for processing a metallic or non- metallic material in various cutting or non-cutting shaping ways using proper tools is called a machine tool.

The machine tool is classified into a cutting machine tool and a metal forming machine tool according to whether or not chips are generated in a working process using a tip or a

drill .

The cutting machine tool, which generates the chips from the material during the working process, includes a lathe, a milling machine, a machining center, a drilling machine, a boring machine, a grinding machine, a gear cutting machine, a special processing machine and so on. The metal forming machine, which does not generate the chips from the material during the working process, includes a mechanical press, a pneumatic press, a cutting and bending machine, a forging machine, a drawing machine and so on.

According to development of technologies and requirement for increasing productivity, an automatized and numerically controlled cutting machine tool has been rapidly developed. Recently, the development of the numerically controlled cutting machine tool was divided into lathe series and milling machine series, however, they are complexly combined and thus a multi-functional machining center is appeared. Due to wide demand for the machining center in the industrial field, a market for the machining center is sharply increased. The machining center is a machine tool which can perform various kinds of cutting processes in a single machine, and has not only a function of automatically changing tools but also a function of automatically working at least two surfaces of a work piece. The machining center is classified into a rotational machining center for processing a rotational work

piece and a non-rotational machining center for processing a non-rotational work piece.

The non-rotational machining center for processing the non-rotational work piece has been improved from an NC milling machine or an NC drilling machine, and includes an automatic tool changer (ATC) , a tool magazine and an automatic pallet changer (APC) .

The rotational machining center for processing the rotational work piece has been improved from an NC lathe so as to perform various processes such as angle dividing, groove working, hole working, tap working and the like after previously performing the cutting process, and also includes the ATC and the APC.

As described above, there is a tendency that the rotational machining center and the non-rotational machining center essentially employ the APC.

According to its driving type, the APC can be classified into a cam-shaft type, a rack-pinion type, a ball-screw type, and a vane-stopper type. Fig. 1 shows a view of a conventional automatic pallet changer (APC) of the cam-shaft type. The cam-shaft type APC includes a shaft 120 which is moved up and down and a cam mechanism 150 which is interlocked with the shaft 120 so as to be rotated. In the cam-shaft type APC, the shaft 120 which receives

power from a fluid pressure or a power transmitting means like a motor is moved up and down, and the cam mechanism 150 interlocked with the shaft 120 is constructed to be rotated by the up and down movement of the shaft 120. However, because the cam-shaft type APC has so many construction components, it is difficult to fabricate and maintain it, and thus fabricating time and cost are increased.

Fig. 2 shows a view of a conventional automatic pallet changer (APC) of the rack-pinion type. The ack-pinion type APC includes a rack 160 in which a tooth portion is formed at one side thereof and a pinion 161 which has a tooth portion engaged with the tooth portion of the rack 160.

Since the ack-pinion type APC is constructed so that the rack 160 is moved up and down by a power transmitting means and the pinion 161 is rotated by the up and down movement of the rack 160, it has a complicated structure and thus it is difficult to fabricate it. Further, it is difficult to exactly and stably transmit power due to the simple tooth engagement type power transmitting method. Fig. 3 shows a view of a conventional APC of the ball- screw type. The ball-screw type APC includes a central shaft on which a screw type ball road 171 is formed, and a ball 170.

In the ball-screw type APC, a piston which is fixed to a housing so as to enclose the central shaft is moved up and down by a fluid pressure and the ball 170 provided in the

piston is also moved up and down along the screw type ball road 171 of the central shaft by the up and down movement of the piston so that the central shaft is rotated. However, the ball-screw type APC has a complicated structure and thus it is difficult to fabricate it. Further, energy loss is occurred during an energy converting process from the up and down movement to the rotational movement, and durability is lowered by friction between the ball 170 and the screw type ball road 171. Furthermore, a fluid is used as a power transmitting medium, and thus if the fluid is not rapidly supplied and withdrawed during a fluid supplying and withdrawing process, a repulsive force is generated. Also if the fluid is supplied and withdrawed too rapidly, the repulsive force is also generated by a collision between components.

[Disclosure] [Technical Problem]

It is an object of the present invention to provide an automatic pallet changer (APC) in which a vane and a stopper are used so as to simiplify a structure of the APC, thereby easily fabricating and facilely maintaining the APC.

It is another object of the present invention to provide an automatic pallet changer ¹ in which a flowing rate of a fluid is properly controlled during a fluid supplying and

withdrawing process

[Technical Solution]

In order to achieve the above objects of the present invention, there is provided an automatic pallet changer (APC) comprising a rotatable cylindrical hollow shaft; upper and lower hydraulic plates which are respectively disposed at upper and lower sides of the shaft and integrally formed with the shaft; a vane which is disposed between the upper and lower hydraulic plates so as to enclose a part of an outer surface of the shaft and integrally formed with the shaft; a stopper which is disposed at the outer surface of the shaft so as to restrict rotation of the shaft; a housing which accommodates the shaft and the stopper and also has a hydraulic supplying port therein; a fixing arm which is coupled to the housing so as to fix the stopper; and a pallet which is interlocked with the shaft so as to be moved up, down, left and right.

Preferably, a hydraulic oil flowing portion is formed at one side of the vane and the other side which is spaced apart from said one side of the vane at a desired angle in a circumferential direction.

Preferably, the hydraulic oil flowing portion comprises a first flowing portion which is formed into a rectangular weir shape of which a depth becomes gradually shallow from one side

or the other side of the vane toward a circumferential direction of the vane, and a second flowing portion which is formed into a triangular weir shape of which a depth and a width become gradually shallow and narrow from one side or the other side of the vane toward the circumferential direction of the vane so as to not only supply and withdraw the hydraulic oil but also absorb a shock.

Preferably, the stopper is disposed between the upper and lower hydraulic plates so that a left and right rotational movement thereof is restricted by the fixing arm.

Preferably, a longitudinally elongated elliptical fixing portion in which the fixing arm is inserted is formed in the outer surface of the stopper so that the stopper is fixed by the fixing arm.

[Description of Drawings]

Fig. 1 is a view of a conventional automatic pallet changer (APC) of a cam-shaft type.

Fig. 2 is a view of a conventional automatic pallet changer (APC) of a rack-pinion type.

Fig. 3 is a view of a conventional automatic pallet changer (APC) of a ball-screw type.

Fig. 4 is an exploded perspective view of an automatic pallet changer (APC) according to the present invention. Fig. 5 is a perspective view of a shaft.

Fig. 6 is a longitudinal view of the automatic pallet changer (APC) according to the present invention.

Fig. 7 is a cross-sectional view of the automatic pallet changer (APC) according to the present invention. Fig. 8 is a view showing an example of rotation of the shaft .

Fig. 9 is a view showing an example of up and down movement of the shaft.

[Detailed Description of Main Elements]

10: housing 11: fixing arm

12: hydraulic oil port 20: shaft

21: vane

22: hydraulic oil flowing portion 22a: first flowing portion

22b: second flowing portion

23: upper hydraulic plate

24: lower hydraulic plate

30: stopper 31: fixing portion 40: pallet 150: cam

160: rack 161: pinion

170: ball 171: ball road

[Best Mode] Practical and presently preferred embodiments of the

present invention are illustrative as shown in the following Examples and Comparative Examples.

Fig. 4 is an exploded perspective view of an automatic pallet changer (APC) according to the present invention, Fig. 5 is a perspective view of a shaft, Fig. 6 is a longitudinal view of the automatic pallet changer (APC) according to the present invention, Fig. 7 is a cross-sectional view of the automatic pallet changer (APC) according to the present invention, Fig. 8 is a view showing an example of rotation of the shaft and Fig. 9 is a view showing an example of up and down movement of the shaft.

Referring to Figs. 4 and 5, the APC includes a rotatably cylindrical hollow shaft 20, upper and lower hydraulic plates 23 and 24 which are disposed at upper and lower sides of the shaft 20 and integrally formed with the shaft 20, a vane 21 which is disposed between the upper and lower hydraulic plates 23 and 24 so as to enclose a part of an outer surface of the shaft 20 and integrally formed with the shaft 20, a stopper 30 which is disposed at the outer surface of the shaft 20 and contacted with one side or the other side of the vane 21 so as to restrict rotation of the shaft 20, a housing 10 for receiving the shaft 20 and the stopper 30, a fixing arm 11 which is coupled to the housing 10 so as to fix the stopper 30, and a pallet 40 which is interlocked with the shaft 20 so as to be moved up, down, left and right.

The upper and lower hydraulic plates 23 and 24, which are disposed at upper and lower sides of the shaft 20 and integrally formed with the shaft 20, are formed so as to be in contact with an inner circumferential surface of the housing 10.

The vane 21, which is disposed between the upper and lower hydraulic plates 23 and 24 so as to enclose a part of an outer surface of the shaft 20 and integrally formed with the shaft 20, has a desired shape so as to enclose a part of the outer surface of the shaft 20 and is fixed so as to be contacted with a lower surface of the upper hydraulic plates 23 and an upper surface of the lower hydraulic plates 24. Thus the vane 21 is interlocked with the upper and lower hydraulic plates 23 and 24 as well as the shaft 20. On one side and the other side of the vane 21, there is formed a hydraulic oil flowing portion 22 through which hydraulic oil as the power transmitting medium for transmitting power to the shaft 20.

The hydraulic oil flowing portion 22 includes a first flowing portion 22a which is formed into a rectangular weir shape of which a depth becomes gradually shallow from one side or the other side of the vane 21 toward a circumferential direction of the vane 21, and a second flowing portion 22b which is formed into a triangular weir shape of which a depth and a width become gradually shallow and narrow from one side

or the other side of the vane 21 toward the circumferential direction of the vane 21 so as to not only supply and withdraw the hydraulic oil but also absorb a shock.

When the hydraulic oil is supplied and withdrawn to/from a hydraulic oil port 12 of the housing 10, the hydraulic oil is passed through the first and second flowing portions 22a and 22b. An amount and a speed of the hydraulic oil passing through the first and second flowing portions 22a and 22b depend on a size and a shape of each of the first and second flowing portions 22a and 22b.

In case that the amount of the hydraulic oil passing through the first and second flowing portions 22a and 22b is increased, a rotational speed of the shaft 20 is also increased. However, a collision between the stopper 30 and the vane 21 is occurred and thus a repulsive force is generated.

On the contrary, in case that the amount of the hydraulic oil passing through the first and second flowing portions 22a and 22b is reduced, the rotational speed of the shaft 20 is reduced, and the withdrawing process of the hydraulic oil filled between the stopper 30 and the vane 21 is delayed, and thus a repulsive force is also generated.

Therefore, the first and second flowing portions 22a and 22b are respectively formed into the rectangular weir shape of which the depth becomes gradually shallow from one side or the other side of the vane 21 toward the circumferential direction

of the vane 21 and the triangular weir shape of which the depth becomes gradually shallow from one side or the other side of the vane 21 toward the circumferential direction of the vane 21 so that the amount and speed of the hydraulic oil can be properly restricted, thereby effectively controlling the rotation of the shaft 20.

The stopper 30, which is accommodated in the housing 10 together with the shaft 20 so as to restrict the rotation of the shaft 20, is interposed between the upper and lower hydraulic plates 23 and 24 and fixed to the housing 10 by a fixing arm 11 coupled to the housing 10.

Herein, an elongated elliptical fixing portion 31 in which the fixing arm 11 is inserted is formed in the outer surface of the stopper 30 so that the stopper 30 is fixed by the fixing arm 11.

Since the fixing portion 31 is formed into the longitudinally elongated elliptical shape, a left and right rotational movement of the stopper 30 is restricted by the fixing arm 11, but the up and down movement can be allowed within a distance range between the fixing portion 31 and the fixing arm 11.

Referring to Figs. 6 and 7 as a longitudinal section view and cross-section view of the automatic pallet changer (APC) respectively and 8 and 9 showing examples of operating of the automatic pallet changer, if the hydraulic oil is supplied

between the stopper 30 and one side of the vane 21 from the hydraulic oil port 12 formed in the housing 10 and also the hydraulic oil filled between the stopper 30 and the other side of the vane 21 is withdrawn through another hydraulic oil port 12 of the housing, the shaft 20 can be rotated.

And if the hydraulic oil is supplied between the stopper 30 and the other side of the vane 21 and the hydraulic oil filled between the stopper 30 and one side of the vane 21 is withdrawn, the shaft 20 is rotated reversely. The hydraulic oil port 12 for supplying and withdrawing the hydraulic oil between the stopper 30 and one or the other of the vane 21 is formed in the housing 10 so as to be correspondent to the first and second flowing portions 22a and 22b formed in one side and the other side of the vane 21. The hydraulic oil is also supplied and withdrawn to/from an upper side of the upper hydraulic plate 23 and a lower side of the lower hydraulic plate 24, and thus a pressure is generated and the shaft 20 is moved up and down by the pressure. At this time, the shaft 20 is moved up and down within the distance range between the fixing portion 31 formed in the outer surface of the stopper 30 and the fixing arm 11 coupled to the housing 10 so as to fix the stopper 30.

The contact surfaces contacted with the vane 21, the shaft 20, the stopper 30 and the housing 10 are respectively spaced apart from them in a gap of 0.05mm and thus it is

prevented that the hydraulic oil is leaked during the process of supplying and withdrawing the hydraulic oil. Therefore, a separate sealing member is not needed to prevent the leakage of hydraulic oil. Further, since the contact surfaces contacted with the vane 21, the shaft 20, the stopper 30 and the housing 10 are respectively spaced apart in a gap of 0.05mm, an oil film is formed by the hydraulic oil and functions as a lubricating oil.

[industrial Applicability]

According to the present invention, the structure of the APC can be simplified by using the vane and the stopper, and thus it is easy to fabricate and maintain it.

Further, since the amount of the hydraulic oil which is supplied and withdrawn through the hydraulic oil flowing portion can be controlled properly, the rotational speed of the shaft is increased and the repulsive force is reduced, thereby improving performance of the APC.

Further, according to the present invention, the rotational movement and the up/down movement of the shaft can be performed without additional apparatus.

Furthermore, since each member is fabricated by a precision working process, it is prevented that the hydraulic oil is not leaked through the contact surface between the members and thus it is not necessary to provide an additional

sealing member, and also since a lubricating film is formed by the hydraulic oil, a lubricating operation is achieved naturally without separate lubricating oil.

Those skilled in the art will appreciate that the conceptions and specific embodiments disclosed in the foregoing description may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. Those skilled in the art will also appreciate that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims.