CYLINDER RAM TRAVEL

TM 94940-539-14&P

D. CYLINDER RAM TRAVEL

The cylinder is equipped with an automat.c limit control valve which will open and stop the ram after its normal

extension of 7' or 14', depending upon the press model.

Avoid using the press with the ram extended to its outermost position.

E. CAUTION

Never apply pressure against the table when suspended only by the cables. After insert- ing the table pins, back off

the winch handle to avoid breaking its gear.

F. HOW THE PUMP WORKS

Referring to the hydraulic schematic circuit, page 4, it will be observed that the fluid in the reservoir (only under

atmospheric pressure) is admitted to the pump chambers through the inlet check valves when the pump handle is moved

upward. (Plungers move outward and the displaced area fills with fluid, then the inlet check valves close.) When the pump

handle is pulled downward, moving the plungers in, the plungers force the fluid in the pump chambers through the outlet

check valves and into the press cylinder. When the plungers stop moving upward, these outlet check valves close and

retain the fluid in the press cylinder. Additional strokes continue this action, adding their charge to the press cylinder each

time the pump is stroked, resulting in a movement of the cylinder ram or an increase in the cylinder pressure.

G. TWO SPEED PUMP ACTION

Both pumps move together resulting in simultaneous intake of fluid from the reservoir through their own inlet check

valves. Also each pump will discharge its fluid through its own outlet check valve into the cylinder circuit, resulting in a

comparatively fast pumping speed of fluid to the press cylinder. However, when the cylinder ram contacts the work and

the resistance is too great to continue using the fast pumping speed, it is necessary to eliminate the high speed pump.

This is accomplished by opening the high volume control valve (SPEED SLOW position), allowing the fluid to escape at

the opened valve from where it can return to the reservoir at no pressure. This results in permitting the large plunger to

continue moving in and out without the need of opening its outlet check valve connecting to the cylinder circuit. With this

arrangement, only the small pump will deliver fluid to the cylinder circuit, permitting the attainment of high pressure.

The smaller pump is equipped with a high pressure relief valve to avoid exceeding the normal operating pressure of the

press. Note that this relief valve is installed in such a manner that when a predetermined pressure is attained, the relief

valve will permit the fluid to escape on the compression stroke to the reservoir. This prevents a further build-up of

pressure but does not relieve the pressure already attained in the cylinder.

H. CYLINDER CONTROL VALVE

The pump unit is equipped with a cylinder control valve, its purpose being to release fluid which has been forced post

the outlet check valves of the pumps into the cylinder circuit. The opening of the cylinder control valve (RAM UP position)

allows fluid to escape at the valve seat and return to the reservoir, permitting the cylinder retracting springs to return the

ram to its uppermost position.

I. CONTROL VALVES

A study of the schematic drawings will show that the control valve balls are located under the valve seats and are held

in contact by springs. This arrangement prevents over- tightening of the valves which would damage the valve seats. It

also has the advantage