Abstract A tool cylinder is provided in parallel with an air pump cylinder. Each cylinder is separated by its respective piston into an upper and a lower chamber each of which communicates pneumatically through an upper and a lower opening with its counterpart in the other cylinder. The openings are open and closed by the relative position of the pistons. A constant volume of air is sealed tightly in the chambers. When the pump piston is actuated upwardly by an external rotary power source, highly compressed air is supplied on the head of the free-piston while a negative air pressure is produced in the lower chambers. The combination of this high pressure above and low pressure below causes the free-piston to be forced abruptly downward. At the lower dead point of the free-piston it hits a chisel and opens an upper portion of the lower opening thus allowing the high pressure in the upper chamber of the tool cylinder to escape to the lower chamber of the pump cylinder. A lower buffer or cushion chamber of relatively large volume is formed in the tool cylinder and it absorbs a part of the downward energy of the free-piston. The free-piston is pushed back by this cushion chamber to a position where a lower portion of the lower opening is opened. At this time, the pump piston is moving downward and thus provides a positive pressure in the lower chamber and a negative pressure in the upper chamber. The free-piston is driven upward by these positive and negative pressures and its own inertia and closes the upper opening, thereby forming an upper buffer chamber in the tool cylinder. The upward movement of the free-piston is absorbed by the upper buffer chamber and the free-piston then falls by its weight to a position where the upper opening is opened, to complete the cycle.
A free-piston type percussion device with air pump, comprising: an air pump cylinder which slidably supports a piston therein, said piston being driven reciprocally up and down in a regular manner by a rotating power source of constant velocity; a tool cylinder housing the said free-piston which on its downward work stroke supplies an impart force to a chisel; means for combining said cylinders adjacent to and in parallel with each other; upper and lower opening means for connecting the internal cavities of said cylinders near their tops and bottoms; an upper buffer means of small volume provided in the upper portion of said tool cylinder by positioning the upper face of said upper opening slightly below the head cover of said tool cylinder, said buffer means preventing said free-piston from striking said cylinder head cover at its upper dead point; and a lower buffer means of large volume provided at the lower portion of said tool cylinder by positioning the lower face of said lower opening far above the lower end of said tool cylinder, said lower buffer rebounding said free-piston after it strikes said chisel and reaches its lower dead point to a position sufficient to open at least a lower portion of said lower opening, said lower opening and said two pistons being in such relationship with each other that said free-piston opens an upper portion of said lower opening at its lower dead point and allows the pressure in said upper chamber of said tool cylinder which forced said free-piston on its downward stroke to escape to said lower chamber of said pump cylinder and in such a relationship with each other that said pumppiston opens an upper portion of said lower opEning at its lower dead point and allows the pressure in said lower chamber of said tool cylinder which forced said free-piston on its return stroke to escape to said upper chamber of said pump cylinder, and said opening and said two pistons being in such a relationship with each other that said free-piston reaches its upper dead point after it closes said upper opening and said pump-piston reaches its upper dead point without closing said upper opening so as to discharge the air compressed in said upper chamber of said pump cylinder through said upper opening to said upper chamber of said tool cylinder thereby forcing said free-piston downward.
Claim 2
Dependent Claim
396 words
A free-piston type percussion device with air pump, comprising: an air pump cylinder which slidably supports a piston therein, said piston being driven reciprocally up and down in a regular manner by a rotating power source of constant velocity; a tool cylinder housing the said free-piston which on its downward work stroke supplies an impart force to a chisel; means for combining said cylinders adjacent to and in parallel with each other; upper and lower opening means for connecting the internal cavities of said cylinders near their tops and bottoms; an upper buffer means of small volume provided in the upper portion of said tool cylinder by positioning the upper face of said upper opening slightly below the head cover of said tool cylinder, said buffer means preventing said free-piston from striking said cylinder head cover at its upper dead point; and a lower buffer means of large volume provided at the lower portion of said tool cylinder by positioning the lower face of said lower opening far above the lower end of said tool cylinder, said lower buffer rebounding said free-piston after it strikes said chisel and reaches its lower dead point to a position sufficient to open at least a lower portion of said lower opening, said lower opening and said two pistons being in such relationship with each other that said free-piston opens an upper portion of said lower opening at its lower dead point and allows the pressure in said upper chamber of said tool cylinder which forced said free-piston on its downward stroke to escape to said lower chamber of said pump cylinder and in such a relationship with each other that said pumppiston opens an upper portion of said lower opEning at its lower dead point and allows the pressure in said lower chamber of said tool cylinder which forced said free-piston on its return stroke to escape to said upper chamber of said pump cylinder, and said opening and said two pistons being in such a relationship with each other that said free-piston reaches its upper dead point after it closes said upper opening and said pump-piston reaches its upper dead point without closing said upper opening so as to discharge the air compressed in said upper chamber of said pump cylinder through said upper opening to said upper chamber of said tool cylinder thereby forcing said free-piston downward.