Spray-assisted pneumatic stone-working apparatus

In a pneumatically operated stone-working tool including a tool drive, a pneumatic line connected to the tool drive for supplying pressurized gas thereto;

• a liquid spray-generating means for spraying the work area with a liquid;
• a liquid line connected to the spray-generating means for supplying liquid thereto;
• a control assembly for effecting energization and de-energization of the tool drive;
• the control assembly including a rotatable valve plunger in the pneumatic line;
• the valve plunger having a first angular position in which it maintains the pneumatic line open for allowing pressurized gas to be admitted to the tool drive from a source of pressurized gas;
• the valve plunger further having a second angular position in which it maintains the pneumatic line closed for preventing pressurized gas to be admitted to the tool drive;
• and a manually actuated lever connected to the valve plunger for rotating the valve plunger into the first or second angular position;
• the improvement wherein said control assembly comprises
• (a) means defining a valve chamber in which said valve plunger is rotatably and linearly slidably received;
• said chamber being in the path of said pneumatic line and said liquid line;
• said plunger having a first linear position in which it maintains said pneumatic line closed in either angular position of said plunger and a second linear position in which it maintains said pneumatic line open solely when said plunger is in its said first angular position;
• (b) force-exerting means continuously urging said plunger towards its said first linear position with a predetermined force;
• and
• (c) a work face forming part of said plunger and being oriented for continuous exposure to a pressure of the liquid in that part of said chamber which is in communication with said liquid line;
• said pressure acting on said work face against said predetermined force for displacing said plunger into its said second linear position when said pressure increases to a predetermined level indicative of a safe pressure for operating said liquid spray-generating means.