referring to fig1 a press machine includes a bolster 2 fixed on a frame 1 . tie rod 3 is planted vertically at each of four corners of the bolster 2 . a middle plate 5 , uprights 6 , and a crown 7 are disposed in order along an intermediate portion of the tie rods 3 . each of the tie rods 3 has a step portion provided at an intermediate portion thereof so that these elements 5 , 6 , and 7 are securely and stably tightened by tightening nuts 8 . the middle plate 5 incorporates a slider guide 4 . a motor 9 is mounted on the crown 7 by fixing means ( not shown ), and a rotational shaft 10a of a fly - wheel clutch 10 is born on the crown 7 . the motor 9 and the fly - wheel clutch 10 are connected by a belt 11 . a pinion 12 jointed to an end of the rotational shaft 10a is engageable with a bevel gear 14 jointed to an input side end of a driving shaft 13 placed at a center of the press machine . the driving shaft 13 has a sphere 15 serving as a center of oscillation and is rotatably supported , through metal bearing , by the crown 7 , the middle plate 5 , the bolster 2 and a knockout plate 17 held by the bolster 2 through rods 16 . the tie rod 3 is surrounded at between the middle plate 5 and the crown 7 by a square or circular pipe 61 , as shown in fig7 or 8 , so that the rigidity of the tie rod 3 between the middle plate 5 and the crown 7 is increased , thereby improving the precision of a motion converting mechanism . a swash plate 19 is fitted onto a portion of the driving shaft 13 between the crown 7 and the middle plate 5 . one side of the swash plate 19 , as shown in fig2 in more detail , is slidably abutted against the crown 7 through a metal bearing sheet 18 . the swash plate 19 is slidably abutted at the other side thereof with an oscillating plate 21 through a metal bearing sheet 20 . as shown in fig4 and 5 , the oscillating plate 21 has a semi - spherical surface portion 21a integrally formed at a center thereof which projects and has an axial through hole 22 . the semi - spherical surface portion 21a rotatably faces the slider guide 4 , and preferably is put into spherical contact therewith . the sphere 15 is rotatably supported by the hole 22 so as to prevent the axial movement of the oscillating plate 21 . a connecting rod 23 having spheres at both ends is rotatably supported by the oscillating plate 21 through a support plate 24 and is disposed at one end thereof near the perpendicular surface of the cylindrical portion 19a of the swash plate 19 , as shown in fig2 and 3 . the other end of the connecting rod 23 is rotatably held in the slider 25 supported by the slider guide 4 through a cap 38 . the slider guide 4 at a center of the middle plate 5 has six cylindrical through holes 26 disposed concentrically and spaced equiangularly , as shown in fig6 . a cylindrical end portion 29a of a locking pin 29 is slidably held by the respective cylindrical holes 26a through a compression coil spring 30 . the lock pin 29 has at the other end a spherical head 27 which is rotatably engaged with a spherical head hole 28 of the oscillating plate 21 . a compression coil spring 31 is held by a cap - like spring pressure member 32 for urging the respective spherical head 27 . the compression force of the spring 30 is substantially equal to that of the compression spring 31 , so that the lock pin 29 is constantly supported in a floating state . the spring pressure member 32 is disposed in a recess portion 19b provided in the swash plate 19 . a description is now made of an ejector or a knockout mechanism . a swash plate 33 is mounted on the knockout plate 17 , and connected to the driving shaft 13 . a slider 35 is slidably disposed in the bolster 2 through a bearing 34 . a spherical head 36 of the slider 35 is rollingly housed by a slipper 37 . the slipper 37 slides on an inclined surface of the swash plate 34 so as to move the slider 35 axially . an operation of the press machine thus constructed will be described hereinunder . when the motor 9 is driven , the rotational force is transmitted to the fly - wheel clutch 10 through the belt 11 , and an energy of such rotational force is held by the fly - wheel clutch 10 . the rotational force selectively transmitted by the clutch 10 to rotate the driving shaft 13 through the pinion 12 and the bevel gear 14 . the swash plate 19 is thus rotated together with the driving shaft 13 , and then the oscillating plate 21 is oscillated , while the rotation thereof is inhibited by the lock pins 29 . since the compression forces of the compression springs 30 and 31 are constantly balanced , the lock pins 29 are axially moved freely through the hole 26 . since the spherical heads 27 of the lock pins 29 are thus substantially constantly placed on a concentric locus , the connecting rods 23 securely transmit vertical movements to the sliders 25 to perform a press operation without horizontal movement . the lock mechanism of the oscillating plate 21 uniformly transmits the rotational driving force to the oscillating plate 21 and thus produces no vibration , thereby causing low noise and high mechanical efficiency . in addition , since a plurality of lock pins 29 are disposed radial inwards from the sliders 25 to which small driving torques are applied , thin pins may be used as the lock pins . further , since the rotation preventing force can be distributed to each of the pins , the press machine has high reliability of mechanical strength even if it is small . the structure in which the entire load during the operation of the press is received by the swash plate 19 increases the rigidity and mechanical efficiency of the machine . in the above embodiment , since the tensile force generated when the slider 25 is separated from a work ( not shown ) is received by the semi - spherical surface portion 21a provided at the center of the oscillating plate 21 , the resistance to the tensile force is high . in addition , since the swash plate 19 has a cylindrical structure in which the spring pressure 32 is disposed in the recess portion 19b , the dead space is effectively employed , and the axial length of the apparatus is decreased , thereby contributing to a decrease in the size thereof . further , since the slide guide 4 is separate from the middle plate 5 , the slider guide 4 can be replaced by another one as occasion demands , thereby easily standardizing the apparatus . fig9 shows another embodiment in which a driving source is modified . an input gear 40 is secured to a driving shaft 13 , which engages with an output gear 42 of a hydraulic motor 41 . the hydraulic motor 41 is connected , through an oil tank 43 , to a hydraulic pump 44 which is driven by an electric motor 9 . this embodiment is characterized in that an output converting mechanism h is within lubricating oil o . the lubricating oil o is of course contained in a sealed structure . according to this embodiment , the durability of the parts of the output converting mechanism is improved and machine sound is absorbed . fig1 and 11 show a press machine according to a further embodiment of the invention , which is horizontally mounted on an upper side of a box - like base 50 . although this embodiment is fundamentally the same as the first embodiment , this embodiment is different from the first embodiment in the point that three sliders 25 are provided parallel . in the present invention , since the work load applied to the slider is received by the swash plate , a small press machine having high rigidity and comprising a driving mechanism having high mechanical efficiency can be obtained .