Pneumatic nailer

A nailing tool comprising a body defining a reservoir adapted to be fed with compressed air, a cylinder fixed within said body and having a lower and an upper end, a plug closing the lower end of said cylinder and having a nailing plunger-receiving slit, a piston slidable in said cylinder, a nailing plunger fixed to said piston and extending through said slit, said piston reciprocable in said cylinder to cause said plunger to accomplish a nailing stroke, said cylinder fully open at its upper end, said body defining a chamber co-axial with and communicating with said cylinder upper end and with said reservoir, a cylinder closure having a leak-proof sliding fit with said chamber and reciprocable therein between a down-position resting on and closing said cylinder upper end, and an up-position opening said cylinder upper end;

• said closure having an underface which, when said closure is in down-position, protrudes outwardly from said cylinder and is exposed to the compressed air in said reservoir, a trigger located over said closure and movable between a top limit position and a down limit position in said chamber and having a head exposed externally of said body, a compression spring located between said trigger and said closure within said chamber, a first air-feeding passage communicating said reservoir and said chamber above said closure, said trigger closing and opening said first air passage in its down and top limit positions, respectively, a first air exhaust passage communicating said chamber above said closure with the ambient air, a second air exhaust passage extending through said closure and communicating the space of said cylinder above said piston with the ambient air, said trigger closing and opening said first air exhaust passage to ambient air in its top and down limit positions, respectively, with said second exhaust air passage being closed and open to ambient air in the up-and-down positions of said closure, respectively with said trigger being in top position, the sum of the downward forces exerted by said compression spring and by said compressed air onto said closure when closed being greater than the upward face exerted by said compressed air on said closure when closed, the downward force exerted by said compression spring on said closure when closed being smaller than the upward force exerted by said compressed air on said closure when closed, where in the rest-position of said tool, the air pressure in said chamber above said closure is equal to the air pressure in said reservoir, the air pressure in said cylinder above said piston is ambient air, said closure being kept closed not only by said compression spring but also by the force differential exerted by said air pressure over and under said closure, and a downward impact force exerted on said trigger causes downward movement of said trigger against the bias of said compression spring and exhaust of the compressed air in said chamber above said closure through said first exhaust means, whereby said closure moves to its up-position closing said second air exhaust passage and allowing compressed air from said reservoir to enter said cylinder and cause said piston to effect a nailing stroke.