Method and apparatus for controlling spring rate and leverage in a screen printing device

In a screen printing machine including a base, a rotary head mounted on said base, a plurality of arms extending radially outwardly from said rotary head, each arm having a screen frame holder mounted at its distal end, wherein said rotary head is indexable to a plurality of printing platens and wherein each arm is mounted for pivotal movement toward and away from said platens about a horizontal axis;

• spring means associated with each arm, said spring means extending from a first attachment means on said arm to a second attachment means on said head, and
• means associated with each arm for simultaneously adjusting the spring rate of said spring means and leverage available for moving each of said arms toward and away from said platens to thereby facilitate uniform movement of each of said arms substantially independently of screen frame size and weight, and to cause said arms to remain raised when raised to a non-printing position, and to remain lowered when lowered to a printing position.

In a screen printing machine, an adjustment mechanism for altering the spring rate of an extension spring extending between a printing head and a screen holding arm mounted to said head for pivotal movement about a horizontal axis of rotation between raised non-printing and lowered printing positions, said adjustment mechanism comprising means for varying in a substantially vertical direction the location of a connector to which an end of the spring closest the head is attached, relative to a horizontal plane containing said horizontal axis of rotation, to thereby enable said spring to maintain said screen holding arm in said raised non-printing and lowered printing positions.

An adjustment mechanism for a screen printing device comprising at least one screen printing arm adapted to hold a screen frame and pivotally mounted to a screen printing head for rotation about a first substantially horizontal axis between raised non-printing and lowered printing positions, said device comprising spring means extending between a first attachment means on said arm and a second attachment means on said head, said adjustment mechanism comprising means for moving one of said first substantially horizontal axis and said second attachment means vertically toward or away from the other to facilitate substantially uniform movement of said screen printing arm toward and away from said screen printing head substantially independently of screen frame size and weight, said spring means acting to hold said screen printing arm in said raised and lowered positions when moved to said positions by a user.

In a method for adapting a screen printing machine to accommodate screen frames of various sizes and weights, said screen printing machine including a head, and at least one screen frame holding arm pivotally mounted on said head for movement about an axis toward and away from a platen to lowered printing and raised non-printing positions, and including a pair of coil extension springs associated with said at least one arm, wherein said springs are arranged on opposite sides of said arm and are attached at outer ends to first attachment points on said at least one arm and at inner ends to second attachment points on said head for controlling the movement of said at least one arm, the improvement comprising the step of:

• (a) vertically adjusting the second attachment points of said extension springs relative to a horizontal plane containing said axis in accordance with the size and weight of the screen frame utilized with the machine, to achieve uniform arm movement and to insure that the arm will remain lowered when moved to the lowered printing position, and remain raised when moved to the raised non-printing position.

In a method for adapting a screen printing machine to accommodate screen frames of various sizes and weights, said screen printing machine including a head, and at least one screen frame holding arm pivotally mounted on said head for movement about an axis toward and away from said platen, a lower printing and raised non-printing positions, respectively, and including spring means extending between a first attachment means on said at least one arm and a second attachment means on said head for controlling the movement of said at least one arm, the method comprising the step of:

• (a) moving said second attachment means to a position above or below said axis, depending on screen frame size and weight to thereby facilitate uniform movement of said screen frame holding arm, and to insure that said screen frame holding arm will remain raised to said non-printing position, and remain lowered when moved to said printing position.

In a screen printing machine including a head and at least one screen holding arm pivotally mounted on said head for movement about an axis toward and away from a platen, and further including at least one pair of coil extension springs, one on either side of said at least one arm, each of said coil extension springs attached at one end to first attachment means on said at least one arm and at another end to second attachment means on said head for controlling the movement of said at least one arm;

• means for adjusting the spring rate of said at least one pair of coil extension springs and for creating varying degrees of leverage to facilitate movement of said arm toward and away from said platen, and wherein said second attachment means each include a connector comprising a pair of spaced eyelet portions connected by an elongate throat portion, an outer one of said eyelets adapted to receive the inner end of one of said extension springs, and an inner one of said eyelets adapted to receive said adjusting means.

In a screen printing machine including a base, a rotary head mounted on said base, a plurality of arms extending radially outwardly from said rotary head, each arm having a screen holder mounted at its distal end, wherein said rotary head is indexable to a plurality of printing platens and wherein each arm is mounted for pivotal movement toward and away from said platens about a horizontal axis;

• spring means including a pair of extension springs associated with each arm, each of said extension springs extending from a first attachment means on said arm to a second attachment means on said head, said second attachment means each including a connector comprising a pair of spaced eyelet portions connected by an elongated throat portion, an outer one of said eyelets adapted to receive the inner end of one of said extension springs, and an inner one of said eyelets adapted to receive said rotatable means, and
• adjustment means associated with each arm for simultaneously adjusting the spring rate of said extension springs and leverage available for moving each of said arms toward and away from said platens, said adjustment means comprising means for moving said second attachment means vertically relative to said horizontal axis.