Injection molding apparatus

Claim 2

In an injection molding apparatus including a pair of platens relatively movable between closed and open positions for closing and opening a mold, means for moving said platens into and out of said two relative positions comprising: a. an electro-magnetic winding embeddEd in one of said platens; b. circuit means for energizing said winding with a magnetizing current in one direction for attracting said other platen thereto to close said platens; c. means for biasing said platens to their open position; and d. circuit means for energizing said winding with a current in the reverse direction of a value sufficient to reduce residual magnetism to a degree that said baising means can move said platens to said open position but below a value to reclose said platens.

Claim 3

In an injection molding apparatus including a pair of platens relatively movable between closed and open positions for closing and opening a mold, means for moving said platens into and out of said two relative positions comprising: a. an electro-magnetic winding embeddEd in one of said platens; b. circuit means for energizing said winding with a magnetizing current in one direction for attracting said other platen thereto to close said platens; c. means for biasing said platens to their open position; and d. circuit means for energizing said winding with a current in the reverse direction of a value sufficient to reduce residual magnetism to a degree that said baising means can move said platens to said open position but below a value to reclose said platens.

Claim 4

In an injection molding apparatus including a pair of platens relatively movable between closed and open positions for closing and opening a mold, means for moving said platens into and out of said two relative positions comprising: a. an electro-magnetic winding embeddEd in one of said platens; b. circuit means for energizing said winding with a magnetizing current in one direction for attracting said other platen thereto to close said platens; c. means for biasing said platens to their open position; and d. circuit means for energizing said winding with a current in the reverse direction of a value sufficient to reduce residual magnetism to a degree that said baising means can move said platens to said open position but below a value to reclose said platens.

Claim 5

The injection apparatus of claim 1, wherein said biasing means are spring means.

Claim 6

The injection apparatus of claim 2, wherein said spring means includes a first relatively stiff spring and a second spring less stiff than said first spring, said second spring having a greater throw than said first spring.

Claim 7

The injection apparatus of claim 1, further comprising injection apparatus including passage means leading to the mold, means for enabling and disabling said injection apparatus, means for energizing said enabling-disabling means upon the closing of said platens to inject molding compound into said mold and means for deenergizing said enabling-disabling means a predetermined time interval after said platens close whereby to discontinue the injection of molding compound when the mold is substantially filled.

Claim 8

The injection apparatus of claim 4, further comprising valve means in said passage means, means for opening said valve means upon said injection apparatus being enabled, and means for closing said valve means a predetermined brief time interval after said injection apparatus is disabled for preventing injection of any substantial quantity of molding compound by residual pressure in said passage means after said injection means has been disabled.

Claim 9

The injection apparatus of claim 5, wherein said means for opening said valve means is pressure responsive.

Claim 10

In an injection molding apparatus including a pair of platens relatively movable between closed and open positions for closing and opening a mold, means for moving said platens into and out of said two relative positions, injection apparatus including passage means leading to the mold, means for enabling and disabling said injection apparatus, valve means in said passage means, means for opening said valve means when said injection apparatus is enabled, and means for closing said valve means a predetermined brief time interval after said injection apparatus is disabled for preventing injection of any substantial quantity of molding compound by residual pressure in said passage means after said injection means has been disabled.

Claim 11

In an injection molding apparatus including a pair of platens relatively movable between closed and open positions for closing and opening a mold, means for moving said platens into and out of said two relative positions, injection apparatus including passage means leading to the mold, means for enabling and disabling said injection apparatus, valve means in said passage means, means for opening said valve means when said injection apparatus is enabled, and means for closing said valve means a predetermined brief time interval after said injection apparatus is disabled for preventing injection of any substantial quantity of molding compound by residual pressure in said passage means after said injection means has been disabled.

Claim 12

In an injection molding apparatus including a pair of platens relatively movable between closed and open positions for closing and opening a mold; I. means for moving said platens into and out of said two relative positions comprising: a. an electro-magnetic winding embedded in one of said platens for magnetically attracting the other of said platens to close the mold when said winding is energized; b. a switch having a first condition when said platens are open and a second condition when said platens are closed; c. a first switching means having energized and deenergized positions and being operable therebetween, said first switching means further including means for delaying the operation of said first switching means from its energized to its deenergized positions, circuit means for energizing said first switching means closed when said switch is in said first condition; d. a second switching means having energized and deenergized positions and being operable therebetween, said second switching means further including means for delaying the operation of said second switching means from its energized to its deenergized position, circuit means for energizing said second switching means closed when said switch is in said second condition; e. a third switching means having energized and deenergized positions and being operaBle therebetween, said third switching means further including means for delaying the operation of said third switching means from its energized to its deenergized positions, and having a longer delay than said first switching means, circuit means for energizing said third switching means and closed only when said switch is in said first condition and said second switching means is in its deenergized position; f. circuit means for energizing said electromagnetic winding in one direction closed when said third switching means is energized; g. a reversing relay, circuit means for energizing said reversing relay closed only when said switch is in said second condition and said third switching means is in its deenergized position; h. circuit means for energizing said electromagnetic winding in the reverse direction when said reversing relay is energized; i. means for biasing said platens to their open position; and II. injection apparatus, means for rendering effective said injection apparatus when said switch is in said second condition and said first switching means is in its energized position.

Claim 13

In an injection molding apparatus including a pair of platens relatively movable between closed and open positions for closing and opening a mold; I. means for moving said platens into and out of said two relative positions comprising: a. an electro-magnetic winding embedded in one of said platens for magnetically attracting the other of said platens to close the mold when said winding is energized; b. a switch having a first condition when said platens are open and a second condition when said platens are closed; c. a first switching means having energized and deenergized positions and being operable therebetween, said first switching means further including means for delaying the operation of said first switching means from its energized to its deenergized positions, circuit means for energizing said first switching means closed when said switch is in said first condition; d. a second switching means having energized and deenergized positions and being operable therebetween, said second switching means further including means for delaying the operation of said second switching means from its energized to its deenergized position, circuit means for energizing said second switching means closed when said switch is in said second condition; e. a third switching means having energized and deenergized positions and being operaBle therebetween, said third switching means further including means for delaying the operation of said third switching means from its energized to its deenergized positions, and having a longer delay than said first switching means, circuit means for energizing said third switching means and closed only when said switch is in said first condition and said second switching means is in its deenergized position; f. circuit means for energizing said electromagnetic winding in one direction closed when said third switching means is energized; g. a reversing relay, circuit means for energizing said reversing relay closed only when said switch is in said second condition and said third switching means is in its deenergized position; h. circuit means for energizing said electromagnetic winding in the reverse direction when said reversing relay is energized; i. means for biasing said platens to their open position; and II. injection apparatus, means for rendering effective said injection apparatus when said switch is in said second condition and said first switching means is in its energized position.

Claim 14

The injection apparatus of claim 8, wherein said circuit means for energizing said electromagnetic winding in the reverse direction includes current limiting means.