Low impact flow control device

A pressure control system for regulating a fluid pressure to at least one cylinder which actuates a corresponding pair of electrodes into and out of engagement with a workpiece, said pressure control system comprising:

• means for supplying a pressurized fluid to said at least one cylinder at a first pressure level;
• flow regulating means in fluidic communication with said supply means and said at least one cylinder for regulating flow of said pressurized fluid from said supply means to said at least one cylinder, said supply means having a first supply pressure level, said flow regulating means being operable between a first position and a second position such that said at least one cylinder is selectively in fluidic communication with said supply means when said flow regulating means is in both said first and second positions;
• first means in fluidic communication with said flow regulating means and said at least one cylinder for reducing said fluid pressure supplied to said cylinder from said first supply pressure level to a second lower pressure level when said flow regulating means is in said first position, such that said pressurized fluid is delivered to said at least one cylinder at said second lower pressure level;
• and
• second means in fluidic communication with said flow regulating means for urging said flow regulating means from said first position to said second position, such that said pressurized fluid is delivered to said at least one cylinder at said first supply pressure level;
• whereby said fluid pressure is at said second lower pressure level when said flow regulating means is in said first position so as to stroke said pair of electrodes into low impact engagement with said workpiece, and said fluid pressure is at said first supply pressure level when said flow regulating means is in said second position so as to increase a clamping load generated by said at least one cylinder on said workpiece.

A method for engaging a workpiece with a pair of welding electrodes which are actuated by at least one corresponding cylinder with a fluid at a first pressure level, and then clamping said workpiece with said pair of welding electrodes while said at least one cylinder is under the influence of said fluid at a second pressure level which is higher than said first pressure level, said method comprising the steps of:

• supplying said fluid at said second pressure level from a fluid source to a flow regulating device;
• reducing the pressure of said fluid from said second pressure level to said first pressure level while said fluid flows through a first passage when said flow regulating device is in a first position;
• monitoring the flow of said fluid through said flow regulating device and said first passage such that said fluid is delivered to said at least one cylinder through said first passage, whereby said pair of welding electrodes engage said workpiece while said at least one cylinder is stroked under the influence of said fluid at said first pressure level;
• and
• urging said flow regulating device to a second position once said pair of welding electrodes has engaged said workpiece such that said fluid is delivered at said second pressure level to said at least one cylinder through a second passage to enable said at least one cylinder to apply a clamping load to said workpiece;
• whereby undesirable impacting of said pair of welding electrodes against said workpiece is substantially avoided by initially engaging said workpiece with said pair of welding electrodes while said at least one cylinder is under the influence of said fluid at said first pressure level so as to initially engage said workpiece with a force which is less than said clamping load.