Band conveying device with vacuum attraction mechanism

Abstract: A band conveying device with vacuum attraction mechanism comprises a base frame, a traveling carriage movable on the base frame, a plurality of band holding units arranged in a row and provided on the traveling carriage perpendicularly with respect to a traveling direction thereof, and a plurality of vacuum pads for attracting and holding a band by vacuum which are arranged in annular form and attached to the band holding units. The vacuum pads are divided into at least two vacuum systems. Each of at least two vacuum systems is provided with a vacuum pressure switch and an electromagnetic valve for shutting off its vacuum system when its degree of vacuum decreases below a given level.

Description: BACKGROUND FOR THE INVENTION: Field of the Invention: This invention relates to a band conveying device for use with a tire forming machine. Description of the Prior Art: From FR-A-20 84 435 a device for picking up sheets by vacuum attraction is known. This known device consists of a plurality of vacuum elements or pads, respectively, each having a valve for shutting off the vacuum source from the respective suction pad when no object is in front of the pad. The pad comprises a tube having at one end a suction nozzle and at the other end a collar forming a circular opening which can be closed by a ball being movable inside the tube between the opening and a stop. Through the circular opening extends a helical spring, one end thereof acting upon the ball and the other end thereof being supported by a screw being disposed opposite to the circular opening and movable in the direction of the axis of the helical spring. Because of this plurality of interdependent factors to be adjusted, this known control mechanism is not easy to handle and, in addition, susceptible to errors and therefore not reliable in a satisfactory manner. The present applicant filed Japanese Patent Application No. 63-82989, which discloses a tire conveying device and proposes to attract a member to be conveyed by vacuum, but not teaches vacuum attraction being performed with respect to any surface portion of the member to be conveyed expect a joined portion. In the process of forming a tire, a band is formed by winding a belt-shaped material around a cylindrical drum. The so-called vacuum attractor (vacuum-pad) is effective in attracting a smooth surface, but not for a rough surface having a stepped portion. The reason is that the vacuum attractor cannot fit with a stepped surface portion of a member to be attracted, leaving a gap between them, so that air is sucked through the gap, disabling vacuum attraction. Since a plurality of vacuum attractors are usually connected together by one pipeline, if at least one vacuum attractor becomes disabled, the others cannot get sufficient vacuum and attain their function. When the belt-shaped material is wound around the drum in a tire forming machine, each resulting joined portion of the material causes roughness in the form of a stepped portion. Since the position of such a stepped portion can be detected, it is possible to position the vacuum attractors so as not to confront the stepped portion. However, the belt-shaped material is usually formed by joining a plurality of material segments of given length, and each resulting joined portion causes roughness in the form of another stepped portion. Such another stepped portion can hardly be detected by the forming machine. Even if this second type of stepped portion can be detected, it is very difficult to position the vacuum attractors so as not to confront the two types of stepped portions. Consequently, the band cannot be conveyed reliably. SUMMARY OF THE INVENTION: It is an object of the present invention to provide a band conveying device with vacuum attraction mechanism which can reliably convey a band having joined portions arising when belt-shaped material segments are joined together and when the resulting belt-shaped material is wound around a drum. To accomplish the foregoing object, the present invention provides a band conveying device with vacuum attraction mechanism which comprises a base frame extending between a band forming station and a tire assembling station, a traveling carriage movable on the base frame, a plurality of band holding units provided on the traveling carriage perpendicularly with respect to the traveling direction thereof, and a plurality of vacuum pads for attracting and holding a band by vacuum, said vacuum pads being arranged at the band holding units in annular form and are attached therewith, characterized in that the vacuum pads are divided and connected to form at least two vacuum systems, and each of at least two vacuum systems being provided with a vacuum pressure switch and an electromagnetic valve for shutting off the respective vacuum system when its degree of vacuum decreases below a given level. As will be appreciated, according to the present invention, the vacuum pads are divided into at least two vacuum systems, and vacuum is applied to the individual vacuum systems. When the degree of vacuum of any vacuum system cannot reach a given level, vacuum supply to such a malfunctioning vacuum system is shut off, and the other vacuum systems (with sufficient vacuum) are used in band conveying. A joined portion arising in the process of a tire forming machine can be put aside. On the other hand, the joined portion of a material appears at only one point along the circumference; therefore, even when the said joined portion of a material causes one vacuum system to get insufficient vacuum, the other vacuum systems can well attract the band by vacuum, whereby the band can be conveyed reliably. BRIEF DESCRIPTION OF THE DRAWINGS: Fig. 1 is a side view showing a band conveying device according to the present invention; Fig. 2 is a view taken in the direction of the arrow Y in Fig. 1; Fig. 3 is a view taken in the direction of the arrow X in Fig. 1; Fig. 4 is a diagram showing a pipeline network for vacuum pads; Fig. 5 is a diagram explanatory of the constitution of a band; Fig. 6 is a diagram explanatory of joined portions of the band; and Fig. 7 is a side view showing the band conveying device with the band held thereby. DESCRIPTION OF THE PREFERRED EMBODIMENT: An embodiment of the present invention will now be described with reference to the drawings. In Figs. 1 through 7, A designates a band holding unit, C a traveling carriage, D a base frame, 2 a band, B2, B3, B4 electromagnetic valves, B5, B6 vacuum pressure switches, and A17, A21, A22 vacuum pads. In Fig. 1, each band holding unit A is slidably supported via a rectilinear bearing C1 and a rail C2 on the traveling carriage C. The three band holding units are moved on the traveling carriage C by a driving unit of the positionable type (not shown). The band holding units A will be described in greater detail with reference to Figs. 1 through 3. A frame A1 is secured on the rectilinear bearing C1, a cam A2 is fitted in the frame A1, and pins A3 and A4 are secured to the cam A2. A pin A5 is secured to the cam A2, and a plurality of grooves A6 are formed. A driving unit of the positionable type A8 is pivotably supported via a pin A10 by a bracket A7 attached to the frame A1, and a clevis A9 at the end of a rod A11 of the driving unit A8 is pivotably supported by the pin A5. The frame A1 has a nut A13 attached thereto, and a screw rod A12 is threaded into the nut A13. This screw rod A12 is attached via a bearing (not shown) to the traveling carriage. A plurality of levers A14 are pivotably supported by pins A3, and one end A16 of each lever A14 is inserted in the corresponding groove A6 of the cam A2. A plurality of levers A15 are pivotably supported by pins A4 secured to the frame A1. Fig. 3 shows the band holding unit disposed at either end, in which a vacuum pad A17 is secured to a corresponding block A24, each block A24 has pins A18 and A19 secured thereto, and the corresponding levers A14 and A15 are pivotably supported. The distance between the pins A3 and A19 of the lever A14 is equal to that between the pins A4 and A18 of the lever A15. Fig. 2 shows the band holding unit disposed at the center, in which the vacuum pads A21 and A22 are arranged in the circumferential direction and secured to a corresponding block A23 as illustrated, and the pins A18 and A19 are secured to each block A23. The support mechanism of the block A23 is identical with that illustrated in Fig. 3. The pipeline network of the vacuum pads A17, A21 and A22 will be described with reference to Fig. 4. The vacuum pads A17 of the band holding units disposed at either end are connected together by branch lines extending from one pipeline, and actuated/deactuated by the electromagnetic valve B2. The vacuum pads A21 and A22 of the band holding unit disposed at the center are actuated/ deactuated by the electromagnetic valves B3 and B4, respectively. Vacuum for the electromagnetic valves B3 and B4 is supplied from the output end of the electromagnetic valve B2. The output ends of the electromagnetic valves B3 and B4 are connected to the vacuum pressure switches B5 and B6, respectively. The operation of the foregoing units will be described. When the band is to be held, first, the electromagnetic valve B2 is turned on to actuate the vacuum pads A17. Then, the electromagnetic valve B3 is turned on. The pressure switch B5 monitors and determines whether or not sufficient vacuum is reached. When sufficient vacuum is reached, the electromagnetic valve B3 is kept on; otherwise, the electromagnetic valve B3 is turned off. Then, the electromagnetic valve B4 is turned on. The pressure switch B6 monitors and determines whether or not sufficient vacuum is reached. When sufficient vacuum is reached, the electromagnetic valve B4 is kept on; otherwise, the electromagnetic valve B4 is turned off. A band conveying device according to the present invention, as shown in Fig. 7, holds and conveys the cylindrical band 2 by means of the vacuum pads A17, A21 and A22. As shown in Fig. 5 in greater detail, the band 2 is composed of side walls B7, an inner liner B8, and a ply B9, these being arranged in laminated form. To hold the band, the vacuum pads A17 come into contact with the side walls, and the vacuum pads A21 and A22 come into contact with the ply. Since the side wall as well as the ply is formed by winding a belt-shaped rubber material into a cylindrical shape, they have joined portions arising in a forming step as shown in Fig. 6. In Fig. 6, B10 designates a joined portion of the side wall, and B11 designates a joined portion of the ply. Usually, the joined portions arising in the forming step are circumferentially distributed such that they are out of phase or take a phase difference of 90° or 180° therebetween. That is, the joined portions of the side wall and the ply can be distributed so as not to be positionally aligned with the vacuum pads. If such provisions are not incorporated, air leaks through between the vacuum pad and the joined portion (having a rough surface) in contact therewith, resulting in insufficient vacuum. Since the side wall B7 is formed by extrusion, its belt-shaped material before a winding step has no joined portion. However, since the ply B9 is formed by connecting a plurality of strip-shaped material segments of given length, its belt-shaped material before the winding step has several joined portions. After the belt-shaped material is wound into a band shape, at least one joined portion (having arisen before the winding step) probably remains on the band. This primary joined portion differs from the joined portion arising in the forming step; thus, it is generally impossible to put the vacuum pad out of alignment with the primary joined portion. Where the holding unit disposed at the center for holding the ply B9 has only one vacuum system of vacuum pads as in the prior art, if the joined portion is aligned with one vacuum pad, the central band-holding unit cannot attain its holding function. Further, if the capacity of a vacuum source is critical, the other vacuum pads cannot get sufficient vacuum, making band conveying impossible. According to the present invention, the vacuum pads of the central band-holding unit are circumferentially arranged in paired form and divided into two vacuum systems. Consequently, when the joined portion (arising before the winding step) is aligned with the vacuum pad by any chance, the one vacuum system inclusive of the above vacuum pad is put out of use and the other vacuum system is put in use, whereby the band can be held and conveyed reliably. Fig. 6 shows the state wherein a primary joined portion B12 different from the joined portion arising in the forming step is in alignment with the vacuum pad A22. In this case, the electromagnetic valve B4 is turned off, so that the band is held by the vacuum pads A17 and A21. In modification, an alarm may be provided which is actuated when both vacuum systems cannot get sufficient vacuum, or an additional pressure switch may be provided in a vacuum system including the vacuum pads A17 to monitor its degree of vacuum. As described above, the band conveying device with vacuum attraction mechanism of the present invention comprises; a base frame extending between a band forming station and a tire assembling station, a traveling carriage movable on the base frame, a plurality of band holding units provided on the traveling carriage perpendicularly with respect to the traveling direction thereof, and a plurality of vacuum pads for attracting and holding a band by vacuum which are arranged in annular form and attached to the band holding units; and is characterized in that the vacuum pads are divided into at least two vacuum systems, and each of at least two vacuum systems is provided with a vacuum pressure switch and an electromagnetic valve for shutting off its vacuum system when its degree of vacuum decreases below a given level. Therefore, the band can be attracted and conveyed by vacuum even in case where the conventional vacuum system of vacuum pads cannot perform vacuum attraction because of the presence of the joined portion in the band material. The joined portion arising in the forming step is properly oriented in the circumferential direction before band conveying, whereby both the joined portion of the band material and the joined portion arising in the forming step can be prevented from being positionally aligned with the vacuum pads. The vacuum system whose degree of vacuum has decreased due to the roughness of the joined portion or the like is shut off by the electromagnetic valve responsive to the vacuum pressure switch for detecting the degree of vacuum. When the degree of vacuum detected by the vacuum pressure switch is improper, an alarm is raised or the machine is stopped.

Claims: A band conveying device with a vacuum attraction mechanism comprising a base frame (D) extending between a band forming station and a tire assembling station, a traveling carriage (C) movable on the base frame (D), a plurality of band holding units (A) provided on the traveling carriage (C) perpendicularly with respect to the traveling direction thereof, and a plurality of vacuum pads (A17, A21, A22) for attracting and holding a band (2) by vacuum, said vacuum pads (A17, A21, A22) being arranged at the band holding units (A) in annular form and are attached therewith, characterized in that the vacuum pads (A17, A21, A22) are divided and connected to form at least two vacuum systems, and each of at least two vacuum systems being provided with a vacuum pressure switch (B5, B6) and an electromagnetic valve (B3, B4) for shutting off the respective vacuum system when its degree of vacuum decreases below a given level. The band conveying device according to claim 1, characterized in that three band holding units (A) are provided on the traveling carriage (C) in a row so as to form two outer band holding units (A) and a center band holding unit (A), the vacuum pads (A17) provided at the outer band holding units (A) are connected to form one vacuum system, and the vacuum pads (A21, A22) attached to the center band holding unit (A) being connected to form at least two vacuum systems, each of which being provided with said vacuum pressure switch (B5, B6) and said electromagnetic valve (B3, B4).

Inventors: AGAWA JIRO, SATO HIDEMASA, AGAWA, JIRO, SATO, HIDEMASA, Agawa, Jiro, c/o Nagasaki Shipyard &amp; Eng. Works, Sato, Hidemasa, c/o Nagasaki Shipyard &amp; Eng. Works
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1991
Main classification: B29D30
IPC codes: B29D30