This invention relates to a mechanical pressing machine of the type in which a slider is reciprocally moved linearly through a rotation cam.
Generally, depending on the type of drive mechanism for a slider, mechanical pressing machines are classified into a crank press, a knuckle press (toggle press) and a cam press. In a crank press, a rotational energy stored in a flywheel is converted into a linear reciprocal motion of a slider through a crankshaft and a connecting rod. Although the crank press is simple in construction, and has been most extensively used, it has problems with respect to rigidity and the generation of heat. In a knuckle press, a rotational energy of a flywheel is converted into a linear reciprocal motion of a slider through a crankshaft, a connecting rod and a knuckle link. In the knuckle press, a change in stroke is small in the vicinity of a lower dead center, and this press well withstands an impact load, but has a problem that the construction is complicated. In a cam press, a rotational energy of a flywheel is converted into a linear reciprocal motion of a slider through a cam and a connecting rod. Although it is rather difficult to manufacture a cam, the cam press has a feature that a curve of motion of the slider can be freely set by suitably determining the configuration of the cam.
Mechanical presses are also classified in terms of the number of portions of connection between a slider drive mechanism and a slider. More specifically, those presses having one connection portion are called a single-point press, those presses having two connection portions are called a two-point press, and those presses having four connection portions, in which two connection points are provided respectively adjacent to the other two connection points in juxtaposed relation thereto, are called a four-point press. The single-point press is suited for pressing a relatively small area which does not impart an unbalanced load to the slider, and the two-point press and the four-point press are suited for pressing a relatively large area which imparts an unbalanced load to the slider. The center of gravity of a die mounted on the press is not always disposed at the center of the pressing machine, and also a load during the pressing operation is not always disposed at the center of the pressing machine. Therefore, when the pressing operation is carried out through the slider on which the die subjected to such an unbalanced load is mounted, the slider is tilted in the single-point press, so that a precise pressing operation can not be carried out.
As described above, there are several kinds of conventional presses which have their respective advantages and disadvantages, and they have been selectively used in accordance with the type of working. However, the pressing machines are costly, and if a different pressing machine is introduced each time a different type of working is to be carried out, high facility costs and a large installation space are needed, and additional facilities suited respectively for several kinds of pressing machines are necessary. This results in a problem that the cost of the product is increased. Therefore, it has been desired to provide a general-purpose pressing machine which has the advantages of different kinds of conventional pressing machines.