The present invention relates to an automatic sheet cutting apparatus which cuts off a sheet like a knit or a woven fabric into a predetermined shape. More particularly, the invention relates to a vacuum air leakage preventive device combined with an automatic sheet cutting apparatus so that evacuated air can be prevented from leaking through a clearance between a bottom surface of one of any brush-mounting bases aligned in parallel with a pair of endless chains and a top surface of the main body of the automatic sheet cutting apparatus.
Any of those conventional chain-driven automatic sheet cutting apparatuses is provided with a number of brush-mounting bases which are aligned on a top surface of a sheet cutting table in parallel with a pair of endless chains installed on both sides of the main body of the automatic sheet cutting apparatus by way of being suspended on them. These brush-mounting bases sequentially move themselves relative to the rotation of a pair of endless chains. In the same way, a number of brushes secured on respective bases move themselves in conjunction with a cuttable sheet. Next, a control system stops the rotation of these endless chains at a predetermined position, and then activates a suction unit below the main body of the automatic sheet cutting apparatus to position the objective sheet on those brushes via a number brushes and those brush-mounting bases before permitting a cutting unit to cut the sheet on a cutting table surface into a predetermined shape by moving the cutting unit to the cutting position.
On the other hand, since there is substantial space between a pair of endless chains on both sides of the automatic sheet cutting apparatus, a supporting member is disposed on the main body of the automatic sheet cutting apparatus so that a number of brush-mounting bases aligned in parallel with and being suspended on these endless chains can slide themselves on the supporting member. This in turn results in an increased resistance against the sliding movement of those brush-mounting bases, and therefore, the apparatus needs to provide such a drive motor having substantial drive capacity.
Therefore, in order to solve this problem, any conventional automatic sheet cutting apparatus is provided with sliding members or rollers below respective brush-mounting bases to shift those brush-mounting bases by causing those sliding members or rollers to slide or roll themselves on the supporting member.
Nevertheless, when these sliding members or rollers installed below those brush-mounting bases on the supporting member of the automatic sheet cutting apparatus slide or roll themselves on the supporting member, a narrow clearance is generated between the bottom surface of those brush-mounting bases and the supporting member. In consequence, when operating a suction unit to pneumatically evacuate a cuttable sheet on those brushes via those brush-mounting bases and brushes, evacuated air leaks out of this clearance, thus resulting in a lowered efficiency.
Therefore, an object of the invention is to fully solve those technical problems inherent in any of those conventional automatic sheet cutting apparatuses by providing a novel system for preventing evacuated air from leaking out of a clearance between the bottom surface of each brush-mounting base aligned on a pair of endless chains and the top surface of the main body of the automatic sheet cutting apparatus.