Abstract:
Two sets of linear motors are fixed on opposed sides of a molding head driving device. Each linear motor includes a movable slider facing a casing. The linear motor contains a molding head and a magnetic plate facing a molding head. The use of two linear motors cancels out the magnetic attraction between the facing linear motors. A linear roller guide is disposed vertically in a direction perpendicular to the magnetic attraction between the linear motors so that the magnetic attraction from the linear motors does not act on the linear roller guide. In another embodiment, three sets of molding head driving devices are disposed between left and right frames integrally formed projecting from a base to form a molding device. In a further embodiment a pair of double linear motors drives four molding head driving devices. The double linear motors are affixed together by, for example, bolts.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a molding device for processing small, precision parts that present a light load and require high positioning accuracy for use in clean work environments and assembly lines. 
     Conventionally, hydraulic presses, crank presses that use a crank mechanism, and the like have been used as molding devices for processing small, precision parts that present a light load and require high positioning accuracy. 
     In addition to these types of presses, there have also been provided molding devices that use an AC servo motor to raise and lower a slide via a screw mechanism. 
     Furthermore, molding devices that use linear motors have also been developed. These devices take advantage of properties of linear motors such as high speed, high positioning accuracy, and efficient transfer of drive force involving quick acceleration and deceleration. 
     In conventional molding devices, a clamp press does not provide stable positioning accuracy for the bottom dead center of the slide due to thermal displacement and the like. With hydraulic presses, the use of oil, the installation space requirements, noise, and the like prevent their use in clean work environments. 
     With molding devices that use an AC servo motor as a drive source, it is a problem to provide high positioning accuracy. In addition, such devices raise safety concerns relating to power outages. 
     With molding devices that use a linear motor, the position at which the linear motor is attached to the guide device can result in the magnetic attraction from the linear motor applying a force to the guide device, which guides the raising and lowering of the molding head. This can cause a change in the gap between the magnetic plate and the movable slide of the linear motor, resulting in unstable thrust from the linear motor, deformation in the guide device leading to increased friction resistance that prevents smooth raising and lowering of the molding head, or the like. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a molding device which overcomes the problems described above. 
     It is a further object of the invention to provide a molding device that is highly accurate, and that has a positioning accuracy for the bottom dead center that is not affected by thermal displacement or the like. The present invention does not require a large installation space and can be used in clean work environments with limited noise and vibration. Positioning of the molding head during high-speed operations is reliable, and if power is lost during a power outage or when operations are stopped, the molding head is held reliably at a stopping position. 
     In order to achieve the objects described above, the present invention. 
     It is a still further object of the invention to provide multiple parallel molding devices which can be operated together or independently. 
     It is a still further object of the invention to provide multiple parallel molding devices on a common base, wherein the multiple molding devices are disposed between rails integrally projecting from the base. 
     The present invention provides a molding device that uses the thrust from linear motors including a magnetic plate and a movable slide to raise and lower a molding head guided by a guiding device disposed on a frame. Magnetic attraction between facing linear motors is canceled out by having two or more linear motors disposed facing each other separated by the molding head. The linear motors include either: a magnetic plate disposed toward the molding head and a movable slide disposed toward the frame; or a movable slide disposed toward the molding head and a magnetic plate disposed toward the frame. A guiding device is disposed to guide the raising and lowering of the molding head along a vertical direction perpendicular to the direction of magnetic attraction between the linear motors. The magnetic attraction from the linear motors is prevented from acting upon the guiding device. 
     The present invention can also provide a molding device as described above where the guiding device is formed as a linear roller guide, with at least two linear roller guides fixed on either side of the molding head. The linear roller guides include a guide rail and a roller unit, either with the guide rail disposed toward the molding head and the roller unit disposed toward the frame or with the roller unit disposed toward the molding head and the guide rail disposed toward the frame. 
     The present invention can also include a linear scale disposed to detect the position of the vertically moving molding head. 
     The present invention can also provide a molding device as described above where a counter-balancing device is disposed to balance the mass of the molding head, including an attached upper mold. This counter-balancing device can be formed from a spring device or an air-cylinder device. 
     The present invention can also include a support device disposed to support the vertically moving molding head at a stopping position when power to the molding device is shut off at the completion of an operation or due to a power outage. This support device can be formed as a spring-activated electromagnetically open device, a spring-activated air-pressure opening device, or a spring-activated oil-pressure device. 
     Briefly stated, the present invention provides two sets of linear motors fixed on opposed sides of a molding head driving device. Each linear motor includes a movable slider facing a casing. Each linear motor includes an armature plate movable adjacent a magnetic plate. The use of two linear motors cancels out the magnetic attraction between the facing linear motors. A linear roller guide is disposed vertically in a direction perpendicular to the magnetic attraction between the linear motors so that the magnetic attraction from the linear motors does not act on the linear roller guide. In another embodiment, three sets of molding head driving devices are disposed between left and right frames integrally formed projecting from a base to form a molding device. In a further embodiment a pair of double linear motors drives four molding head driving devices. The pair of double linear motors are affixed together by, for example, bolts. 
     According to an embodiment of the invention, there is provided a molding device comprising: at least two linear motors, the at least two linear motors facing each other separated by a molding head, a magnetic attraction between facing linear motors is canceled out by their positioning facing each other, the linear motors including a magnetic plate disposed toward one of the molding head and the frame, and a movable slide disposed toward the other of the molding head and the frame, a guiding device for guiding raising and lowering of the molding head along a vertical direction perpendicular to a direction of magnetic attraction between the linear motors, and the magnetic attraction from the linear motor is prevented from acting upon the guiding device. 
     According to a feature of the invention, there is provided a molding device comprising: a molding head, a guiding device for guiding the molding head in a linear direction, a molding head driving device, the molding head driving device including at least first and second linear motors, with one of the first and second linear motors fixed on each side of the molding head, each of the first and second linear motors including a movable slider and a magnetic plate, one of the movable slider and the magnetic plate being affixed to the molding head, and the other of the movable slider and magnetic plate being affixed to the molding head, a magnetic field of the magnetic plates in the first and second linear motors being oriented so that magnetic fields therefrom cancel at the guiding device, the guiding device being disposed vertically in a direction perpendicular to the magnetic attraction between the linear motors, the molding head driving device is formed in a modular structure so that the guiding device is not affected by the magnetic attraction between the linear motors, and at least one of the molding head driving devices is disposed between a left frame, a center frame, and a right frame projecting from a common base. 
     The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a schematic front-view perspective drawing of a molding device according to an embodiment of the present invention. 
     FIG. 2A is a schematic rear-view perspective drawing of the molding device of FIG.  1 A. 
     FIG. 3A is a schematic cross-section drawing of the molding device of FIG.  1 A. 
     FIG. 4 is a drawing to which reference will be made in describing the structure of the linear motor. 
     FIG. 1 is a cross section of a molding device having a plurality of mold driving devices on a common base. 
     FIG. 2 is a cross section taken along A—A in FIG.  1 . 
     FIG. 3 is a vertical cross section through one of the mold driving devices of FIG.  1 . 
     FIG. 5 is a vertical cross section through a further embodiment of a mold driving device. 
     FIG. 6 is a vertical cross section showing two pairs of mold driving devices on a common base. 
     FIG. 7 is a vertical cross section showing one pair of mold driving devices on a common base, disposed between separate pairs rails integrally formed with the base. 
     FIG. 8 is a vertical cross section similar to FIG. 7, except for showing three mold driving devices on the common base, disposed between separate pairs of rails integrally formed with the base. 
     FIG. 9 is a vertical cross section showing two pairs of slide driving devices, wherein each pair of slide driving devices is on its own base, and the two bases are connected together. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1A,  2 A and  3 A, a frame  2  of a molding device I includes a left frame  3  having a table  3 A on which a lower mold (not shown in the figures) may be attached. A right frame  4  is fixed to the left frame  3 . The front frame includes a vertical driving section for a molding head  36 , which is raised and lowered. An upper mold (not shown in the figures) may be attached to the molding head  36 . 
     Referring now also to FIG. 4, movable sliders  6 A,  6 A of a linear motor  6  are fixed to the inner front surface and the rear front surface of the front frame  4 . Magnetic plates  6 B,  6 B are fixed to the front surface and the rear surface of the molding head  36 , which is disposed inside of the right frame  4 . Magnetic plates  6 B,  6 B face and engage movable sliders  6 A,  6 A, which are disposed on the right frame  4 . 
     The linear motor  6  includes: a movable slider  6 A, in which a coiled wire  19  and a cooling section therefor are formed integrally. A magnetic plate  6 B, formed from N poles and S poles of a permanent magnet is separated by a space from the movable slider  6 A. Continuous thrusting is obtained by controlling and synchronizing the current phase through coil  19  of the movable slider  6 A based on the positions of the magnetic polarities facing the coil  19 . 
     A forced cooling pipe not shown in the figures is embedded inside the movable slider  6 A very close to the coiled wire  19 . The cooling pipe absorbs the heat generated in the coiled wire  19 . A cooling device not shown in the figures provides cooling by supplying a cooling fluid via pipes  20 ,  20 , which are connected to openings  16 ,  16  disposed at the end of the movable slider  6 A, thus allowing efficient external discharging of heat. This minimizes the effect of heat generated by the linear motor  6  on the molding device. 
     The cooling of the linear motor  6  can also be accomplished using an air-cooling method. 
     Roller units  7 A,  7 A are fixed to the inner left surface and the inner right surface of the right frame  4 . Guide rails  7 B,  7 B, facing and engaging the roller units  7 A,  7 A disposed on the right frame  4 , are fixed to the left surface and right surface of the molding head  36 . 
     A counter-balancing device  11  is disposed inside the molding head  36 . The counter-balancing device  11  urges the mass of the molding head  36 , including an upper mold not shown in the figure, toward a predetermined position using the force from a spring  10  via a bracket  8  fixed to the right frame  4  and a stud bolt  9  engaging the bracket  8 . 
     A linear scale  13 , disposed at a rear section of the left frame  3 , is scanned by a detection head  12  to detect the vertical position of the molding head  36 . The detection head  12  is positioned where it avoids obstructing the linear motor  6 . The detection head  12  projects from the molding head  36  through a cut-out opening  17  in the left frame  3 . 
     A spring-activated, electromagnetically open support device  14  is disposed at a rear section of the left frame  3 . A disk plate  15  projects from the molding head  36  through a cut-out opening  18  in the main frame  3  so as to avoid obstructing the linear motor  6 . When power to the molding device  1  is cut off due to the completion of work or a power outage, the disk plate  15  is secured via a spring not shown in the figures, thus reliably keeping the molding head  36  at its stopping position. 
     When power is sent to the molding device  1 , the support device  14  is excited and the spring (not shown in the figure) is activated to open the disk plate  15 . 
     When the disk plate  15  is opened, current is applied to the coils  19 ,  19  of the movable sliders  6 A,  6 A of the linear motors  6 ,  6  based on a stroke length and top dead center and bottom dead center for the molding head  36  as defined beforehand in a control device not shown in the drawings. The molding head  36  is raised and lowered by the thrust of the linear motors  6 ,  6 . Linear roller guides  7 ,  7 , which serve as a guiding device, are disposed vertically in a direction perpendicular to the direction of magnetic attraction between the linear motors  6 ,  6 . Thus, the magnetic attraction from the linear motors  6  is not applied to the linear roller guide  7 , thereby providing stable and accurate positioning for the bottom dead center. 
     In the linear motors  6  of this embodiment, the movable slider  6 A is fixed toward the right frame  4  and the magnetic plate  6 B is fixed toward the molding head  36 . However, it would is also possible to form the linear motors  6  with the magnetic plate  6 B fixed to the right frame  4  and the movable slider  6 A fixed to the molding head  36 . 
     Also, in the linear roller guide  7  of this embodiment, the roller unit  7 A is fixed toward the right frame  4  and the guide rail  7 B is fixed to the molding head  36 . However, it is also possible to form the linear roller guide  7  with the guide rail  7 B fixed toward the front frame  4  and the roller unit  7 A fixed toward the molding head  36 . 
     Furthermore, the counter-balancing device  11  in this embodiment is performed by a spring device. It is also possible to use an air-cylinder, or other device for counter-balancing. The supporting device  14 , which is described above as a spring-activated electromagnetically open device, can also be a spring-activated activated air-pressure opening device or a spring-activated oil-pressure device. 
     As the description above makes clear, the present invention provides high positioning accuracy for the bottom dead center of the molding head that is not affected by thermal displacement or the like. Furthermore, the present invention can be used with limited installation space and clean work environments, and provides a molding device having a molding head with limited noise and vibration that can be reliably positioned during high-speed operations. 
     Also, the stopping position of the molding device can be reliably maintained after an operation is completed or when the power to the molding device is cut off due to a power outage or the like. 
     Referring to FIGS. 1,  2  and  3 , a multiple molding device  1 ′ includes a left frame  3  and a right frame  4  formed integrally with a base  2 . A lower die  9  (not shown in the figures) is attached the base  2 . A plurality of molding heads  36  are disposed inside three identical molding head drive devices  5 ,  5 ,  5 . The molding head drive devices are disposed between the left frame  3  and the right frame  4 . The molding head drive devices  5 ,  5 ,  5  are raised and lowered as a single unit. A plurality of upper dies (not shown in the figures) are attached to the molding heads  36 . 
     Movable sliders  8 A,  8 A are fixed to the inner left surfaces and the inner right surfaces of casings  7 . Magnetic plates  8 B,  8 B, which engage the movable sliders  8 A,  8 A of the casings  7 , are fixed to the left side surfaces and the right side surfaces of the molding heads  6  inside the casings  7  so that they face the movable sliders  8 A,  8 A. 
     Referring now to FIG. 4, each linear motor  8  in this embodiment is the same as the single-die linear motor described above, and thus further description thereof is omitted. 
     Returning now to FIG.  1  through FIG. 3, roller units  12 A,  12 A are fixed to the inner front surface and the inner rear surface of the casing  7 . Guide rails  12 B,  12 B, facing the roller units  12 A,  12 A engage roller units  12 A,  12 A of the casing  7 . Guide rails  12 B,  12 B are fixed to the front surface and the rear surface of the molding head  36 , thus forming linear roller guides  12 ,  12 . 
     As described above, the members which form the molding head drive devices  5  are disposed inside the casings  7  to form a single unit. The molding heads  36  of the molding head drive devices  5 ,  5 ,  5  can be raised and lowered according to a desired stroke length and timing. Thus, a wide variety of products requiring multi-step processing can be easily obtained. 
     Current is passed through the coils  9 ,  9  (FIG. 4) in the movable sliders  12 A,  12 A of the linear motor  8 ,  8  according to the top dead center and the bottom dead center of the molding head  36  and the stroke length as entered beforehand in a control device not shown in the figures. The molding head  36  is raised and lowered by the thrust of linear motors  8 ,  8  to perform pressing of a given material between a lower die (not shown in the figures) attached to the base  2  and an upper die (not shown in the figures) attached to the molding head  36 . 
     By having facing linear motors  8 ,  8  disposed on either side of the molding head  36 , the magnetic attraction between the facing linear motors  8 ,  8  is canceled out, thus allowing smooth raising and lowering of the molding head  36 . 
     Also, the linear roller guides  12 ,  12 , which serve as a guiding device, are disposed vertically in a direction perpendicular to the attachment position of the linear motors  8 ,  8 , i.e. to the direction of magnetic attraction between the linear motors  8 ,  8 . Thus, the magnetic attraction from the linear motor  8  is not applied to the linear roller guide  12 , and stable positioning accuracy for the bottom dead center is provided. 
     In this embodiment, linear motor  8  is formed by having the movable slider  12 A disposed on the casing  7  and the magnetic plate  8 b fixed on the molding head  36 . However, it would also be possible to have the linear motor  8  formed with the magnetic plate  8   b  fixed on the casing  7  and with the movable slider  12 A fixed on the molding head  36 . 
     Also, in this embodiment, the linear roller guide  12  is formed by having the roller unit  12 A fixed to the casing  7  and the guide rail  12 B fixed to the molding head  36 . However, it would also be possible to have the linear roller guide  12  formed with the guide rail  12 B fixed to the casing  7  and the roller unit  12 A fixed to the molding head  36 . 
     Referring to FIG. 5, a second embodiment of the invention includes a molding device  21  having a left frame  23  and a right frame  24  formed integrally with a base  22 . A single molding head driving device  5  is interposed between a left frame  23  and a right frame  24 . The second embodiment is identical to the first embodiment shown in FIG.  1  through FIG. 4 except for the number of molding head driving devices  5 , so the description will be omitted. 
     Referring to FIG. 6, there is shown a third embodiment of the present invention which includes two pairs of molding head driving devices  5 . The operation of this embodiment is the same as in the previous embodiments, and will therefore be omitted. 
     Referring to FIG. 7, there is shown a fourth embodiment which includes a single pair of molding head driving devices  5 . Referring to FIG. 8, there is shown a fifth embodiment. The operation of this embodiment is the same as in the previous embodiments, and will therefore be omitted. 
     The third embodiment, the fourth embodiment, and the fifth embodiment are identical to the first embodiment described above except for the middle frame, so a detailed description will be omitted. 
     Returning to FIG. 6, a molding device  31  according to the third embodiment includes a left frame  33  and a right frame  34  integrally with a base  32 . A middle frame  35  is formed integrally with the base  32  at a central position between the left frame  33  and the right frame  34 . Two identical molding head driving devices  5 ,  5  are interposed as a single unit between the left frame  33  and the left side surface of the middle frame  35 . Two identical molding head driving devices  5 ,  5  are interposed as a single unit between the right side surface of the middle frame  35  and the right frame  34 . 
     Returning to FIG. 7, a molding device  41  according to the fourth embodiment includes a left frame  43  and a right frame  44  integrally formed with a base  42 . A center frame  45  is formed integrally with the base  42  at a central position between the left frame  43  and the right frame  44 . A single molding head driving device  5  is interposed between the left frame  43  and the left side surface of the middle frame  45 . A single molding head driving device  5  is interposed between the right side surface of the middle frame  45  and the right frame  44 . 
     Referring to FIG. 8, a fifth embodiment of the invention includes a left frame  53  and a right frame  54  integrally formed with a base  52 . A first middle frame  55 A and a second middle frame  55 B are formed integrally with the base  52  between the left frame  53  and the right frame  54 . 
     A single modular molding head driving device  5  is interposed between the left frame  53  and the left side surface of the first middle frame  55 A. A single modular molding head driving device  5  is interposed between the right side surface of the first middle frame  55 A and the left side surface of the second middle frame  55 B. 
     Furthermore, a single modular molding head driving device  5  is interposed between the right side surface of the second middle frame  55 B and the right frame  54 , thus forming the molding device  51 . 
     In the embodiments described above, the molding head driving devices  5  interposed between the left frames  3 ,  23 ,  33 , 43 ,  53  and the right frames  4 ,  24 ,  34 ,  44 ,  54  all have identical structures. However, it is also possible to use a different type of molding head driving device  5  for the ones attached to the left frames  3 ,  23 ,  33 ,  43 ,  53  and the right frames  4 ,  24 ,  34 ,  44 ,  54 , with casings  7  having different attachment sections. 
     Also, in these embodiments, the middle frames  35 ,  45 ,  55  are formed in two pieces. Referring to FIG. 9, it would also be possible, as shown in a sixth embodiment, to have a molding device  61  formed, for example, by connecting a left center frame  65 A projected from a base  62 A and a right center frame  65 B projected from a base  62 B using tightening means  66 , e.g., a bolt. 
     Also, in these embodiments, the molding head driving devices  5  interposed between the left frames  3 ,  23 ,  33 ,  43 ,  53  and the right frames  4 ,  24 ,  34 ,  44 ,  54  use the side on which the linear motor  8  is attached as the connecting surface. However, it would also be possible to use the side on which the linear roller guide  12  is attached as the connecting surface. 
     As described above, the present invention provides a molding device that allows positioning of molding heads for high-speed operations. Noise and vibration is limited, and the bottom dead center of the molding head can be precisely positioned without being affected by thermal displacement or the like. The present invention can also be used in clean work environments and in limited installation spaces. 
     Furthermore, when processing small, precision parts that require multiple steps, the frame can be structured according to the molding steps, thus making the present invention easy to implement for a molding line. 
     Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.