Patent GB-731248-A (GB)
Title: Improvements in or relating to presses
IPC: B30B15/00
Filed: 1951-06-04
Abstract: 731,248. Operating clutches; machinery guards. HAWKES, S., and HAWKES (N.V. ENGINEERS), Ltd., F. May 19, 1952 [June 4, 1951], No. 13194/51. Classes 80 (2) and 80 (4). [Also in Groups V and VIII] A clutch for transmitting the drive to a press (see Group V) to produce a closing movement thereof in two stages comprises a central driving element 37, Fig. 6, keyed to a shaft 28, a driven element 42, loose on the shaft, to produce the first stage of the closing movement, i.e. the approach stroke, and another driven element 98, likewise loose on the shaft, to produce the second stage, i.e. the power stroke. To bring about engagement between the elements 37 and 42 a depression of the press treadle causes a bolt 44, slidable in a bore 43 in the element 42, to be pressed towards the element 37 by a spring 46 when an abutment 47, which otherwise restrains it, is moved. The abutment 47 is crescent-shaped, Fig. 5, and pivoted at 49, and it is normally held in the position shown by the pressure of a spring 53 in a projecting housing 51, the other end of the spring bearing against a plunger 52 in contact with a wall of the clutch box. The spring housing has a nose 55 and this nose initially is in line with a plunger 56 which is movable by the pressure of a lever arm 61 against its other end. This lever arm is fixed to a stem 62 which is rotatable, through another arm 65, by levers connected, through a link 69, to a lever 133 which can be depressed by the treadle of the press. Depression of the treadle causes the arm 61 to move the plunger 56 against the nose 55 and so swing the abutment 47 about its pivot. The face of the abutment 47 against which a head 45 on the bolt 44 bears has a cam surface 72, whereby its movement allows the bolt 44 to move under the influence of the spring 46 into the path of a dog 40 on the rotating element 37, with which the element 42 then rotates also. The rotation of the element 42 is caused to give an angular motion to a lever 79 by the interaction of a roller 75 and an eccentric 74, Fig. 4, the roller being carried on the end of an arm 76 projecting from the sleeve carrying the lever 79 and the eccentric 74 being formed as a boss on a cam 73 on the element 42. The motion of the lever 79 causes the approach stroke of the press, and it is terminated by an extension 50 of the abutment 47, also crescent shaped, and also having a cam surface over which the head 45 of the bolt 44 rides when the element 42 has rotated through approximately 180 degrees, whereby the bolt is again retracted and the drive broken. The sleeve 57 housing the plunger 56 has an ear 139 slidable on a cross shaft 58, and the plunger can thus be moved out of line with the nose 55 against the pressure of a return spring. The cross shaft 58 also carries a slidable sleeve 84, Fig. 4, which has spigot in contact with the ear 139, towards which it is urged by a stronger spring, but this spring does not cause movement of the sleeve and ear along the cross-shaft until the element 42 has rotated until a depression 106 in the cam surface 73 comes opposite a roller 86 on an arm extending from the sleeve, at which point it causes the plunger 56 to move clear of the nose 55. Although the pressure on the nose 55 is thus removed the spring 53 does not immediately return the abutment 47 to its first position, because the extension 50 has ridden over the end of a plunger 87, Fig. 9, which has been moved underneath it by a spring 90 and so locked it, whereby the ear 139 remains in the position to which it has been moved along the cross-shaft 58. The press platen also is thus prevented from rising again at the end of the approach stroke, as it would otherwise do due to its return springs. When the plunger 56 moves clear of the nose 55 it moves into the path of a nose 109 on a spring housing 100 projecting from a crescent-shaped abutment 95, Fig. 8, which is similar to 42 except it has no extension corresponding to 50, but has an extension 102 with a set screw 103 for adjusting the throw. To bring about engagement between the elements 37 and 98 a second depression of the press treadle causes the arm 61 to move the plunger 56 against the nose 109 and so swing the abutment 95 about its pivot 99, with the result that a head 96 on a bolt 97, Fig. 6, will ride on a cam surface on the abutment and cause a spring to move the bolt 97 into the path of a dog 41 on the rotating element 37, so causing the clutch element 98 to rotate. The clutch element 98 has a cam surface 111 over which runs a roller 112 on an arm 113 secured to a spindle 115 which projects through the wall of the clutch box and carries a lever 116. The arm 113 also incorporates a transverse sleeve 108 with a spring plunger 144 which bears against an adjacent wall of the clutch box and so keeps the roller 112 in contact with the cam surface 111. The motion of the lever 116 causes transmission of movement for the power stroke of the press. After the loose' clutch element 98 has made approximately one complete turn the bolt 97 is withdrawn by the cam surface on the abutment 95, which has resumed its original position by virtue of the release of the treadle. The clutch element 98 also carries a sleeve with a nose 129, Fig. 8, and during its rotation the nose 129 strikes a roller 94 on the end of a projection 93 from an arm 92, Fig. 9, the end of which is pivoted to the plunger 87, which it therefore retracts against the spring 90, so releasing the extension 50 of the abutment 47 and allowing resetting of the parts of the approach clutch and hence restoration of the ear 139, carrying the plunger 56 to its initial position. Safety device.-To discontinue the down stroke of the press platen at any time the operator has only to move a knee bar which, through a cable, moves the tail 143 of the arm 92, Fig. 9, causing the plunger 87 to be moved out of the way of the abutment 50 with the result that the approach clutch is reset and the platen is sent to its top position by its return springs.