Power frame saw

In a power frame saw having a machine frame, working clamping means mounted on the machine frame and composed of clamping jaws which are relatively movable for clamping a workpiece in a fixed position, guide means pivotally mounted with weight balancing on the machine frame, a saw bow mounted on the guide means to undergo reciprocating movement in a given direction relative to the guide means, a saw blade held in the bow to extend at an oblique angle to the direction of movement, drive means connected for imparting such reciprocating movement to the bow to cause the saw blade to perform successive cutting and return strokes, and means for controlling pivotal movement of the guide means relative to the machine frame and including a source of hydraulic pressure fluid, a main piston-cylinder unit mechanically connected between the machine frame and the guide means and presenting a hydraulic chamber connected to receive fluid from the source for producing a force tending to pivot the guide means relative to the machine frame, a displacement piston-cylinder unit defining a hydraulic chamber connected in fluid communication with the main piston-cylinder unit chamber, a cam drive system rotating with the drive means and connected to act on the displacement piston-cylinder unit in a manner to vary the volume of its hydraulic chamber for cyclically causing the force with which the guide means presses the blade against the workpiece to decrease during each return stroke and increase during each cutting stroke, a cutting pressure regulating valve connected to the hydraulic chambers for maintaining the fluid pressure therein below a selected maximum value, and a charging piston-cylinder unit presenting a chamber connected between the hydraulic pressure fluid source and the main piston-cylinder unit chamber and operatively associated with the cam drive system for delivering a quantity of fluid to the main piston-cylinder unit during each return stroke to advance the saw blade into the workpiece during each successive cutting stroke, the improvement comprising adjustment means responsive to the spacing between the clamping jaws and connected to control the stroke of said charging piston-cylinder unit for causing the magnitude of the quantity of fluid delivered to said main piston-cylinder unit during each return stroke to be an inverse function of the spacing between the clamping jaws, whereby when the jaws are farthest apart for holding the largest workpiece the magnitude of the fluid quantity is a minimum and when the jaws are closest together for holding the smallest workpiece the magnitude of the fluid quantity is a maximum.