US2712168A - Molding press - Google Patents

Description

July 5, 1955 F. J. KENLINE 2,712,163

MOLDING PRESS Filed May 24, 1952 I 2 Sheets-Sheet l INVENTOR. ram-dz 9. BY

y 5, 1955 F. J. KENLINE 2,712,163

MOLDING PRESS Filed May 24, 1952 2 Sheets-Sheet 2 INVENTOR.

p z 441M United States Patent MGLDING PRESS Frederick J. Kenline, Buffalo, N. Y., assignor to Lake Erie Engineering Corporation, Buffalo, N. Y., a corporation of New York Application May 24, 1952, Serial No. 289,741

13 Ciaims. (CI. 25-45) This invention relates to molding presses and more particularly to apparatus for controlling the volume of the material fed into the mold of a molding press such as a brick press during the feeding portion of the brick forming cycle.

In one form of conventional brick press, there is provided a mold with which plungers cooperate to form the top and bottom of the mold. Means are provided for supplying material to the mold and power actuated means are provided for moving the plungers toward each other for thus pressing the material in the mold into the shape of a brick. In a press of this general type, the position of the bottom plunger at the time the mold is filled determines the volume of the brick forming mix which enters the mold, and therefore, determines the forming pressure, the Weight of the brick, the thickness of the brick, and influences to a large degree the porosity and density of the bricks.

The manufacturer of bricks, especially refractory bricks, strives for uniformity in the thickness, weight, and qualities of his product. The density and porosity of refractory bricks greatly influence several refractory qualities in which uniformity is an essential factor such as slag absorption, chemical reactivity to furnace slags and furnace atmospheres, and resistance to thermal shock. Absolute uniformity of the bricks in the pressing operation is dependent upon three factors, the time of each pressing cycle being constant: (1) uniformity of the volume and apparent density of the brick forming mixture entering the mold during each cycle (2) the same position of the bottom plunger relative to the top of the mold during each mold-filling operation and (3) the application of the same amount of pressure during each cycle. Since the commonly used method of feeding the mold does not provide for absolute uniformity in the density of the brick-forming mixture entering the mold on each cycle, it is necessary that means be provided for making volume adjustments by controlling the position of the bottom plunger to compensate for variations in the density of the brick-forming mixture. In the normal press operation the adjustment is made manually from time to time, sometimes every few minutes, by the operator-who judges fromthe weight and thickness of the brick whether the proper amount of material has been used, or from the sound of the press (as learned from his experience) whether excessive pressures are being used in brick form- Accordingly the principal object of the present invention is to automatically adjust the volume of the mold to compensate for variations in the apparent density of the brick-forming mixture to mold bricks having dimensions and densities within predetermined tolerances.

Another object is to provide an electrical control system for a molding press which automatically adjusts the depth of fill of the mold and is responsive to the spacing of the top and bottomplungers of the press at the end of the pressing phase in one operating cycle of the press for adjusting the relative position of the bottom plunger 2,712,168 Patented July 5, 1955 with respect to the mold during the mold filling phase of the next succeeding operating cycle.

Another object is to provide such a molding press which produces bricks or like molded articles having uniform dimensions and densities falling within very small tolerance ranges.

These objects, as well as other objects and advantages of the invention which will be apparent from the following description and accompanying drawings, are attained in one embodiment of my invention by automatically adjusting the depth of fill of the mold so that for a given tonnage of the press the bricks will conform to predetermined dimensional tolerances but have maximum density for the particular press, and in another embodiment by automatically adjusting the depth of fill of the mold so that for a given volume of the brick-forming mixture the bricks will conform to predetermined dimensional tolerances but have a density falling within a predetermined density range.

In the accompanying drawings:

Fig. 1 is a diagrammatic representation of one embodiment of my invention and showing a hydraulic molding press having associated therewith an electrical control system for automatically controlling the depth of fill of the mold cavity so that for a given tonnage the molded articles will always have maximum density.

Fig. 2 is a diagrammatic representation of another embodiment of my invention and showing a hydraulic molding press having associated therewith an electrical control system for automatically controlling the depth of fill of the mold cavity so that for a given volume of material the molded articles will have a predetermined density.

Figure 1 Referring more particularly to the form of the invention shown in Fig. 1, the brick press is shown in simplified diagrammatic form as having an intermediate stationary platen or mold 1 shown as having a central brick forming cavity 2 which corresponds to the size and shape of the brick to be produced in horizontal section but extends vertically completely throughthe intermediate stationary platen. The press also is shown as having a lower vertically movable platen 3 which carries an upstanding.

plunger 4 fitted in the bottom of the cavity 2 and having the same rectangular size and shape so as to enclose the lower end of this cavity and provide a bottomtherefor. This lower movable platen 3 also carries a pair of upstanding lower dimensional stops, one of which is indicated at 5, and which lower dimensional stops are shown as extending into sidereccsses 6 provided in the intermediate stationary platen 1. The press also is shown as having an upper movable platen 7 secured to the lower end of a ram 8. This upper movable platen carries a pair of depending upper dimensional stops, one of which is indicated at 9, and which are arranged to engage the lower dimensional stops, indicated at 5, of the lower movable platen 3. This ram 8 has an enlarged piston head 10 which works in the bore of a closed stationary maincylinder 11. A closed reservoir or tank 12 is mounted on the upper end of the main cylinder 11, communication between this reservoir and the upper end of the bore of the main cylinder being provided by an opening 13 under control of an upwardly closing prefill valve 14 which is spring loaded to urge it to a closed position. This valve 14 is actuated through a piston rod 15 projecting upwardly from the prefill valve and connected with a piston 16 which works in a closed stationary cylinder 18, this stationary cylinder being arranged in the reservoir or tank 12.

The upper dimensional stop 9 is shown as provided with a vertical passage 21 which is continued through the upper movable platen 7 for a purpose which will presently appear. These stops and 9 provide a positive limit for the approach of the platens 3 and 7. The cavity 2 is filled by any suitable means (not shown) with the brick forming mix or material 23 from which the brick is formed, the material in this cavity being compressed by an upper plunger 24 depending from the upper movable platen 7 in position to enter the cavity 2 and conforming to its cross sectional shape.

The depth of fill of the cavity 2 with the material 23 is determined by a position of the vertically movable bottom plunger 4 relative to the stationary intermediate platen or mold 1. This bottom plunger 4, together with the lower movable platen 3, is moved vertically by a vertical screw 26 which is held against vertical movement by any suitable means (not shown) and works in a threaded opening 27 in the lower movable platen 3. This screw 26 is turned through a pair of bevel gears 28 from the shaft of a reversible electric motor M. It will be seen that when the motor M is energized to turn in one direction the lower movable platen 3 and the bottom plunger 4 will be raised to provide a reduced depth for the cavity 2 and when energized to turn in the reverse direction lowers this platen and plunger to provide an increased depth of fill for the cavity 2.

The hydraulic circuit for the brick press is shown as comprising a main pump 30 of any suitable type. This main pump 30 delivers liquid under pressure through a pump discharge line 31 one branch 32 of which is connected with a four way solenoid valve indicated generally at 33 and the other branch 34 of which is connected to a solenoid valve 35. The branch line 32 has a restriction 29 to maintain pilot pressure in the branch 34 from the main pump 30 even when the four way solenoid valve 33 opens the branch 34 to the reservoir or tank 12.

The four way solenoid valve 33 is shown as comprising a stationary body having a closed bore 36 which communicates at its center with the branch 32 of the main pump discharge line and intermediate its ends with lines 37 and 38, the line 37 leading to the upper end of the bore of the main cylinder 11 and the line 38 leading to a two way check valve indicated generally at 39 and also by a branch 38a to the upper end of the cylinder 18 of the prefill valve 14. The opposite ends of the bore of the four way valve 33 communicate with the opposite ends of a passage 40 the central part of which is connected by a line 41 with the tank or reservoir 12. The line 38, intermediate its branch 38a and the four way solenoid valve 33, is provided with a restriction 47 to maintain pressure in the branch 38a even when the four way solenoid valve 33 opens the branch 38 to the reservoir or tank 12.

A reciprocable valve plug 42 is fitted in the bore 36 of the four way valve 33, this valve plug being provided with circumferential grooves 43, 44 and 45 forming corresponding movable chambers for connecting the different lines in different relations. The plug 42 is extended at one end through the body of the valve to provide the core 46 for a winding 48, and is extended at its opposite end through the body of the valve to provide the core 49 for a winding 50. V

The valve plug 42 is centered by a spring (not shown) in the neutral or deenergized position shown in which the line 37 is blocked and the branch 32 of the main pump discharge line is connected through the grooves 44 and 43 of the plunger with the line 41 leading to the tank or reservoir 12. When the winding 50 is energized, the plug 42 is moved to connect the branch 32 of the main pump discharge line, through the groove 44, with the line 37 leading to the upper end of the bore of the main cylinder 11, and to connect, through the groove 43, the line 38 of the two way check valve 39 and cylinder 18 of the prefill valve 14 with the line 41 of the tank or reservoir 12. When the winding 48 is energized, the plug 42 is moved to connect the branch 32 of the main pump discharge line, through the groove 44,

with the line 38 leading to the two way check valve 39 and cylinder 18 of the prefill valve 14, and to connect the line 37 from the upper end of the bore of the main 4 cylinder 11, through the groove 45, to the branch 40 of the line 41 of the tank or reservoir 12.

The return line 51 of the main pump 30 leads from the tank or rservoir 12 and is connected through a relief valve 52 with the line 37 between the four way solenoid valve 33 and the upper end of the bore of the main 2 cylinder 11.

The solenoid valve 35 is shown as comprising a stationary housing having a bore 53in which is fitted a r piston 54, this piston having a passage 55 extending axially the position shown in which the branch 34 of the main pump discharge line is blocked and in which a line from the tank or reservoir 12 is in communication, through the passage 55, with a line 62 leading to the 2 two way check valve 39.

This two way check valve 39 comprises a stationary body having a horizontal central partition 63 providing an upper chamber 64 and a lower chamber 65. The line 38 of the four way solenoid valve 33 connects with the lower chamber 65 and the upper chamber 64 is connected 73 by a line 66 with the lower end of the bore of the main cylinder 11. A check valve 68 in the upper chamber 64 seats against an opening 69 through the partition 63 to prevent how of liquid from the upper chamber 64 to the 7 lower chamber 65 but to permit a reverse flow when the pressure in the lower chamber 65 is greater than that in the upper chamber 64. A spring loaded check valve 70 in the lower chamber 65 seats against an opening 71 through the partition 63 to prevent flow of liquid from the lower chamber 65 to the upper chamber 64 but to permit a restricted reverse fiow from the upper chamber 64 to the lower chamber 65 when the pressure of its spring is overcome. This check valve 70 has a stem 72 connected with a piston 73 in a cylinder 74 formed in the housing of the two way check valve, this cylinder 74 communicating with the line 62 of the solenoid valve 35.

Power for the electrical circuit of the brick press is derived from three power lines 75, 76 and 78. The power line 76 is connected through a branch line 79 with one of the contacts of a normally closed manual return switch 80, the other contact of this manual return switch 80 being connected by a line 81 with the normally open contact 82 of a control relay indicated generally at 83. The winding 84 of this control relay is connected with the power line 75 and also with an armature 85 of the relay which engages the contact 82 when the winding 84 is energized. The main power line 76 is connected by a branch 86 with an armature 88 of the relay 83 and which engages a contact 89 when the winding 84 is deenergized.

The line 81 of the manual return switch 80 is connected by a branch line 90 with one contact of a normally open manual start switch 91, the other contact of this start switch being connected by a line 92 with the winding 50 of the four way solenoid valve 33. A branch 93 of this line 92 connects with the end of the winding 84 opposite the main power line 75 and also with the armature 85.

A second branch 94 of the line 92 connects with the stationary contact of a slow down limit switch 95, the movable contact 96 of which is opened during the final part of the descent of the main ram 8 by contact with a cam 98 mounted on the upper movable platen 7. The

.- movable contact 96 of this slow down limit switch is connected by a line 99 with the winding 59 of the solenoid valve 35, the other end of this winding being connected by a line 100 with the main power line 75.

A branch 101 of this line 100 connects with the winding 102 of a control relay 103, the other end of this winding being connected through a line 104 with the movable contact 105 of a return limit switch 106, this return limit switch being opened by engagement of the movable contact 105 thereof with the cam 98 mounted on the upper movable platen 7 during the final part of the return stroke of the main ram 8. The fixed con tact of this return limit switch 106 is connected by a line 108 with the fixed contact 89 of the control relay 83.

The winding 48 of the four way solenoid valve 33 is connected across the line 100'and 104 by branch lines 109 and 110. The line 100 is also connected by a branch line 111 with the end of the winding 50 opposite the line 92.

In the energized condition of the winding 102 of the control relay 103, its normally open armature 112 is drawn into engagement with a fixed contact connected by a line 114 with the main power line 76. This armature 112 is connected by a line 115 with the normally open armature 116 of a timer 118, the timing of this timer starting on the energization of its winding 119 which is connected by a line 120 with the line 115, and by a line 121 with a branch 123 of the main power line 75.

The armature 116 of the timer 118 engages a fixed contact 124. After the energization of its winding 119 and the expiration of the period for which the timer 118 has been set its armature 116 is disengaged from 124. Change in the position of the plunger 4 occurs between the moment when the timer 118 is energized and when the timer 118 times out. The armature 116 will then have moved from the position shown in Fig. l to engage the dead contact. The timer 118 resets only after the relay 103 is deenergized by the cam 98 disengaging the armature 106 from the stationary contact 108 of limit switch 106. The fixed contact 124 is connected by a line 125 with the winding 126 of a normally open control relay 127. The other side of this winding 126 is connected by a line 128 with the branch 123 of the power line 75.

The armature 129 of the control relay 127 is connected with the branch line 79 of the main power line 76 and, when the winding 126 is energized, is drawn into engagement with a fixed contact 130 and which is connected by a line 131 with a pair of armatures 132 and 133 of a control relay 134, the armature 132 being normally open, and the armature 133 being normally closed. The winding 135 of this control relay 134 is connected by a line 136 to the branch 123 of the main power line 75 and the other side of this winding 135 is connected by a line 138 to a third, normally open armature 139 of the control relay 134 and also with the movable contact 140 of a depth of fill limit switch 141 mounted on the upper movable platen 7.

This movable contact 140 of the depth of fill limit switch 141 is arranged to be moved, under certain conditions as will hereinafter appear, upwardly into engagement with its fixed contact 142 when the upper movable platen 7 reaches the end of its working stroke. For this purpose a spring depressed actuator rod 143 is arranged in the vertical passage 21 through the upper movable platen 7 and upper dimensional stop 9 and with its lower end in position to engage the lower dimensional stop 5 on the lower movable platen 3. The upper end of this actuator rod 143 is provided with an arm 144 which engages and lifts the movable contact 140 of the depth of fill limit switch 141 when the actuator rod 143 strikes the lower dimensional stop 5 and is lifted relative to the upper movable platen 7. The fixed contact 142 of the depth of fill limit switch 141 is connected by a line 145 with the fixed contact 146 of the control relay 134 and which is engageable with the normally open armature 139 thereof. This line 145 is also connected to the line 120 connecting with the winding 119 of the timer 118.

The remainder of the electrical circuit is concerned with the reversing line starter 150 for the motor M. This cavity 2 forms no part of the invention, this apparatusreversing line starter has a decrease winding 151 connected by a line 152 with the branch 123 of the main power line 75 and an increase coil or winding 153 also connected by a line 154 with the branch 123 of the main power line 75. The other side of the decrease coil 151 is connected by a line 155 with a fixed contact 156 of the control relay 134 and which is engageable with the normally closed armature 133 of this relay. The other side of the increase coil 153 is connected by a line 158 with a fixed contact 159 of the control relay 134 and which is engageable with the normally open armature 132 of this relay.

Energization of the decrease coil 151 of the reversing line starter 150 closes three normally open armatures 160, 161 and 162. The armature is connected by a line 163 with the branch 123 of the main power line 75. The armature 161 is connected by a line 164 with a branch 165 of the main power line 76. The armature 162 is connected by a line 166 with the main power line 78. The armature 160 is drawn into engagement with a fixed contact 168 at the end of a line 169 leading to the reversing motor M. The armature 161 is drawn into engagement with a fixed contact 170 connected with a second line 171 leading to the reversing motor M. The armature 162 is drawn into engagement with a fixed contact 172 at the end of a third line 173 leading to the motor M.

Energization of-the increase coil 153 of the reversing line starter 150 closes three normally open armatures 175, 176 and 178 against fixed contacts 179, 180 and 181, respectively. The fixed contact 179 is at the end of the branch 123 of the main power line 75. The fixed contact 180 is at the end of the branch 165 of the main power line 76. The fixed contact 181 is at the end of the main power line 78. The armature is connected with the motor line 171. The armature 176 isconnected with the motor line 169. The armature 178 is connected with the motor line 173.

Operation of Fig. 1

is not shown or described.

To begin the pressing phase of the press operating cycle during which the material 23 is compressed into a brick, the operator presses the start switch 91 so as 1 to establish a circuit from the main power line 76, line 79, normally closed return switch 80, line 90, closed start switch 91, lines 92 and 93, winding 84 of control relay 83 to main power line 75. The energization of winding 84 of the control relay 83 pulls its armature 85 intoengagement with the contact 82 thereby to establish a holding circuit which is maintained after the start switch 91 is released, this holding circuit being from main power line 76, line 79, closed return switch 80, line 81, contact and armature 82, 85 and winding 84 to the main power line 75.

The energization of the winding 84 of the control relay 83 also establishes a circuit from main power line 76, through line 79, closed return switch 80, line 81, contact and armature 82, 85, lines 93 and 92, winding 50 of the four-way valve 33, and lines 111 and 100 to the main power line 75.

The energization of the winding 84 of the control relay 83 also establishes a circuit from the main power line 76, through line'79, closed return switch 80, line 81, contact and armature 82, 85, lines 93, 92 and 94, closed slow down limit switch 95, line 99, winding 59 '7 of solenoid valve 35, and line 101) to the main power line 75. The slow down limit switch 95 is closed at this time because the movable upper platen 7 is in an elevated position and hence the cam 98 thereon is out of contact with the movable contact 96 of this normally closed slow down limit switch.

The closing cycle is initiated by this energization of the winding 50 of the four way solenoid valve 33 and the winding 59 of the solenoid valve 35. The energization of the former causes theplug 42 in the four way solenoid valve 33 to move downwardly as viewed in Fig. 1, and the energization of the latter causes the piston 54 of the solenoid valve 35 to move to the right as shown in Fig. l and thereby establish communication from line 34 to line 62 and block oif line 60. Fluid under pressure from the main pump 38 therefore passes from the outlet line 31 through branch line 34, solenoid valve 35, and line 62 into the cylinder 74, thereby moving the piston 73 downwardly against the resistance of its spring and opening the valve 70 to permit fluid to flow through the valve opening 71. The downward position of the plug 42 of the four way solenoid valve 33 causes this plug to direct volume from the main pump 30 through lines 31 and 32, groove 44, and line 37 to the upper end of the main cylinder 11 above the piston head 10. At the same time fluid trapped under this piston head 10 is permitted to escape through line 66, upper chamber 64 of the two way check valve 39, open valve port 71, lower chamber 65 of this valve 39, line 38 through the restriction 47, groove 43 in the plug 42 of the four way solenoid valve 33 and line 41 to the tank or reservoir 12. Under these conditions the ram 8 descends rapidly causing a back pressure to build up behind the restriction 47 in line 38. This back pressure is applied through the branch line 38a to the prefill cylinder 18 above the piston 16 of the prefill valve 14. This back pressure is sufficient to move the piston 16 and prefill valve 14 downwardly against its spring thus allowing fluid to flow from the tank or reservoir 12 into the upper end of the cylinder 11 during this rapid part of the closing movement of the ram 8.

A small amount of such rapid downward movement of the ram causes the cam 98 to release the armature 105 of the limit switch 106 and allows this armature to engage the stationary contact 108 and set up the circuit later used to return the ram 8.

Further progress of the ram 8 downwardly causes its cam 98 to engage the armature 96 of the limit switch 95 and moves this armature away from the stationary contact 94 thus breaking the circuit through the winding 59 of the solenoid valve 35 and which circuit was established by the relay 103 through the line 99. The spring 56 in the solenoid valve 35 then moves the plunger 54 to the left as viewed in Fig, 1, thereby to block off line 34 and to connect lines 62 and 60 through the port 55 in the plunger 54. This last connection relieves the pressure behind the plunger 73 which had been overcoming the spring of the valve 78 and allows this valve 70 to close under the influence of its spring. The setting or resistance of this spring is such that sufficient back pressure is built up in the upper chamber 64 of the two way check valve and in line 66 to support the main ram 8 and the other weights connected with this main ram. The closing of the valve 70 also eliminates the back pressure existing in lines 38 and 38a and hence the prefill valve 14 is permitted to close under the influence of its spring and thereby cut off the direct flow of liquid from the reservoir 12 to the upper end f the cylinder 11. However, the main pump 30 is still delivering fluid into the upper end of the main cylinder 11 through lines 31, 32, groove 44 in the plug 42 of valve 33, and line 37 to the upper end of the main cylinder 11, and with the prefill valve 14 closed, main pump pressure commences to build up in the upper end of the main cylinder 11 and drive the main piston 8 10 and ram 8 downwardly. This downward movement of the main piston 10 forces the liquid under this piston to escape through line 66 to the upper chamber 64 of the two way check valve 39. This pressure is sufficient to overcome the spring of the valve 70 and to force this valve open. Accordingly the speed of further descent of the main ram is determined by the delivery of the main pump 30.

The descent of the main ram 8 continues until a back pressure against the liquid above the piston head 19 builds up to a value where it opens the relief valve 52 and bypasses the liquid from the main pump 30 through the lines 37 and 51 into the tank or reservoir 12. This back pressure is produced either by engagement of the dimensional stops 5 and 9 or by a compression of the charge to a value equal to the preset tonnage of the press. It is to be noted, however, that in either event the dimensional stops 5 and 9 either are brought into engagement or are brought into very close relation to each other as that under all conditions of continuous operation bricks of the same dimensions, Within very close tolerance, and of maximum density for the particular tonnage, are produced.

During this final descent of the ram 8, the actuator rod 143 either does or does not close the depth of fill limit switch 141. At this time it shall be assumed that this actuator rod 143 does not close this depth of fill limit switch 141, and the operation of the electrical control system for influencing the relative position of the bottom plunger 4 with respect to the mold 1 during the mold filling phase of the next succeeding operating cycle will be described accordingiy. This retention of the depth of fill limit switch 141 in an open condition at this time is occasioned by an excessive fill of the material in the mold cavity 2.

To start the press opening phase of the operating cycle, the operator presses the return switch 80, thereby opening the circuit through the winding 84 of the control relay 83 and permitting its armatures 85 and 88 to assume the position shown in Fig. 1. This operates to denergize the winding 50 of the four way solenoid valve 33 since one side of this winding is energized through the lines 92 and 93 and armature 85 of the control relay 83 which is opened by the deenergization of the relay 83. At the same time the opposite Winding 48 of the four way solenoid valve '33 is energized through a circuit comprising the main line '76, line 86, armature 88 and contact 89 of control relay 83, line 168, closed return limit switch 166, lines 104 and 109, winding 48 and lines 110 and 100 to the main power line 75.

Energization of the winding 48 of the four way solenoid valve 33 moves its plug 42 to connect the branch 32' of the main pump discharge line, through the groove 44, with the line 38 leading to the two way check valve 39 and cylinder 18 of the prefill valve 14. Accordingly the prefill valve 14 is moved to the open position shown so that liquid above the piston head 1!] is free to escape directly from the upper end of the bore of the main cylinder 11 into the tank or reservoir 12. Also, main pump pressure is supplied from the line 38 to the upper chamber 64 of the two way check valve 39. This pressure opens the check valve 70 against the resistance of its spring and permits the escape of this fluid through the port 71 and lower chamber 65 of the two way check valve 39 and through the line 66 to the main cylinder below' the piston head 10 so that this piston head is forced to rise.

The movement of the plug 42, when the winding 48 of the four way solenoid valve 33 is so energized, also connects the line 37 from the upper end of the bore of main cylinder 11, through the groove 45, to the branch 40 of the line 41 leadingto the tank or reservoir 12.

During the initial part of this return movement of the main ram 8, the slow down limit switch is permitted to close by disengagement of the cam 98 of the upper movable platen 7 from the movable contact 96 of this slow down limit switch. However, this closing has no effect at this time because the circuit through this switch is open at the armature 85 of the control relay 83.

The deenergization of the control relay 83 also energizes the winding 102 of the control relay 103. This energization is from the main power line 76, through line 86, closed armature and contact 88, 89 of the control relay 83, line 108, closed return limit switch 106, line 104, winding 102 of control relay 103, and lines 101 and 100 to the main power line 75. The energization of the control relay 103 pulls up its armature 112 so as to establish a circuit from the main power line 76, through line 114, armature 112 of control relay 103, lines 115 and 120, winding 119, of timer 118 and lines 121 and 123 to the main power line 7 5. This starts the timer 118 which continues to remain energized for the period of its time setting. Upon the expiration of: this period of time, it is deenergized. It is noted at this point that the setting of this timer determines the length of time of the depth of fill readjustment which time may be anything from a small fraction of a second to several seconds.

As long as the timer 118 is energized the control relay 127 is also energized through the circuit comprising the main power line 75, lines 123 and 128, winding 126 of the control relay 127, line 125 and closed contact and armature 124, 116 of the timer 118, line 115, armature 112 of control relay 103 and line 114 to the main power line 76. The energization of the control relay 127 pulls up its armature 129 and connects the armatures 132 and 133 with the main power line 76 through the line 131, closed contact and armature 130, 129 of the control relay 127 and line 79.

The control relay 127 controls the connection of the armatures 132 and 133 of the control relay 134 with a live power line. The energization of this control relay 134 is under control of the normally open depth of fill limit switch 141 so as to control the selection of either the decrease winding 151 or the increase winding 153 of the reversing line starter 150 for energization.

Under the assumed condition, that is, that the actuator rod 143 did not close the depth of fill limit switch 141 during the descent of the ram 8 because of the presence of an excessive charge in the cavity 2, it will be noted that the control relay 134 is not energized.

Accordingly at this time, the armature 133 of the control relay 134 is permitted to remain in engagement with the fixed contact 156 and thereby energize the decrease winding 151 of the reversing line starter 150, this circuit through the decrease winding 151 being from the main power line 76, line 79, closed armature and contact 129, 130 of the control relay 127, line 131, closed armature and contact 133, 156 of the control relay 134, line 155, decrease winding 151 and through lines 152 and 123 to the main power line 75.

Energization of the decrease winding 151 of the reversing line starter 150 pulls up the armatures 160, 161 and 162 so as to engage these armatures with their respective contacts 168, 170 and 172. This connects the motor line 169 through the lines 163 and 123 with the main power line 75; the motor line 171 through the lines 164 and 165 with the main power line 76; and the motor line 173 through the branch 166 with the main power line 78. This connection of these three motor lines with the three main power lines energizes the motor M to rotate in the direction to raise the bottom plunger 4 relative to the intermediate platen or mold, and hence decrease the depth of the cavity 2 and thereby decrease the depth of fill during the next operating cycle of the brick press. As previously noted, this adjustment of the bottom plunger 4 continues only so long as the timer 118 is energized, and in any event not longer than the period for which control relay 103 is energized, this latter being deenergized when the circuit therethrough is broken on the opening of the return limit switch 106. Normally the operative period for which the timer 118 is set is less than the time required for completely opening the press but in the event this timer 118 is set for a longerp'eriod, the depth of fill adjustment will be positively terminated with completion of the press opening phase of the operating cycle.

In the description immediately preceding, it was assumed that the depth of fill of the cavity 2 was excessive and that hence the actuator rod 143 was not moved sufficientlyfar to close the depth of fill limit switch 141, whereby the decrease winding 151 was energized. On the other hand, if the depth of fill of the cavity 2 is insufiicient so that at the end of the pressing phase of the same press operating cycle, the dimensional stops 9 and 5 engage before the full capacity or tonnage of the press can be utilized to compress the charge of material in the cavity 2, the actuator rod 143 is raised sufiiciently far to close the depth of fill limit switch 141.

Under these conditions the foregoing description with respect to the energization of the control relay 103, timer 118 and control relay 127, still obtains. However, a circuit is now established through the winding of the control relay 134, this circuit being from the main power line 75 through the branch lines 123 and 136, winding 135, line 138, closed contacts and 142 of the depth of fill limit switch141, lines 120 and 115, closed armature 112 of control relay 103 and line 114 to main power line 76.

The control relay 134 is locked in and for this purpose when it is so energized a circuit is established from the main power line 75, lines 123 and 136, winding 135 of the control relay 134, closed armature and contact 139, 146, lines 145, 120 and 115, closed armature 112 of control relay 103, and line 114 to the main power line 76. Accordingly, this control relay 135 is held in an energized condition until the control relay 103 is de-' energized to break this holding circuit.

The energization of the control relay 134 operates to energize the increase winding 153 of the reversing line starter and prevents the energization ofits decrease Winding 151. For this purpose a circuit is established from the main power line 76 through line 79, closed armature and contact 129, 130 of the control relay 127, line 131 and closed armature and contact 132, 159 of control relay 134 and line 158 through the winding 153 of the reversing line starter 150 and through lines 154 and 123 to the main power'line 75. I Y

Energization of the increase winding .153 of the re'-' versing line starter 150 draws the armatures 175, 176 and 178 into engagement with the fixed contacts 179, and 181, respectively. This connects the motor line 171 with the main power line 75 through the closed armature and contact 175, 179 and branch line 123. This also connects the motor line 169 with the main power line 76 through the closed contacts 176, 180 and branch line 165. This also connects the motor line 173 with the main power line 78 through the closed armature and contact 178, 181. With the motor lines 171, 169 and 173 so connected with the main power lines 75, 76 and 78 the motor M is energized to rotate in the direction to lower the bottom plunger 5 and relative to the stationary intermediate platen or mold 1, and thereby increase the vertical extent of the cavity 2 and thereby increase the depth of fill during the next operating cycle of the brick press.

It will be thus seen that if the depth of the cavity 2 is insufiicient to produce a brick of the desired dimensions and density, the depth of fill limit switch 41 is closed by the actuator rod 143 and the increase winding 153 of the reversing line starter 150 is energized so as 'to drive the motor M in the directionto lower the bottom plunger 4 so that with the next charge of the cavity 2 a greater amount ofmaterial will be received therein to produce a brick closer to the predetermined density and dirnensions. On the other hand, if the depth of the cavity 2 is too great to produce a brick of the desired density and dimensions when the material is compressed, the actuator rod 143 is engaged by the lower dimensional stop but is not raised sufficiently to close the depth of fill limit switch 141, this energizing the decrease winding 151 of the reversing line starter 150 thereby to energize motor M to raise the bottom plunger 4 to correct this condition for the next succeeding cycle.

The motor M operates in either direction as long as the timer 118 is energized, this being for the time interval for which this timer has been set. At the end of this period the timer 118 deenergizes thereby to release its armature 116 and break the circuit through the winding 126 of the control relay 127. The deenergization of this control relay 127 operates to disconnect the armatures 132 and 133 of the control relay 134 from the main power line 76 and, accordingly, both the decrease winding 151 and increase winding 153 of the reversing iine starter 150 are cut out of circuit so as to deenergize the motor M.

As the upper movable platen 7 begins to rise the depth of fill limit switch 141, it closed, is opened but this does not operate to decnergize the winding 135 of the control relay 134 since this winding is locked in. As the upper movable platen 7 continues to rise, the slow down limit switch 95 is closed but this does not operate to energize the winding 50 of the four way solenoid valve 33 or the winding 59 of the solenoid valve 35 since the circuit therethrough is broken at armature 85 of the deenergized control relay 83.

The upper movable platen 7 continues to rise until its cam 98 engages the movable contact 105 of the return limit switch 106 so as to disengage this contact and open this switch. Opening of the return limit switch 106 breaks the circuit through the winding 102 of the control relay 103 and also the winding 48 of the four way solenoid valve 33. Deenergization of the winding 43 of the four way solenoid valve 33 permits the plug 42 to be returned to its neutral position shown in Fig. l by its return spring (not shown) and to thereby connect the branch line 32 of the main pump discharge with both lines 38 and 41, and also to block line 37. Accordingly the parts are returned to the position assumed at the start of the description of the operation preparatory to another cycle of operation.

It will be noted that the adjustment of the depth of fill takes place only during the press opening phase of the operating cycle of the press, and preferably only during the initial part of this phase or, in other words, during the ascent of the upper movable platen 7.

Figure 2 In the form of the invention shown in Fig. 2, the hydraulic circuit is the same as that illustrated in Fig. 1 with the addition of two electrical pressure switches 190 and 191 responsive to the pressure in the main cylinder 11 above the piston head of the ram 8. Accordingly the description of the hydraulic circuit is not repeated and the same reference characters used in Fig. l have been applied. Both pressure switches 190 and 191 are shown as connected with the line 37 communicating with the upper part of the bore of the cylinder 11 and the pressure switch 190 is normally closed, whereas the pressure switch 191 is normally open.

Power for the electrical control system in the form of the invention shown in Fig. 2 is derived from three main power lines 195, 196 and 198. The main power line 196 is connected through a branch line 199 with one of the'contacts of a normally closed manual return switch 200, the other contact of this manual return switch 200 being connected by a line 201 with the normally open contact 202 of a control relay indicated generally at 203. The winding 204 of this control relay is connected with the main power line 195 and also with an armature 205 of the relay which engages the contact 202 When the winding 204 is energized. The main power line 196 is connected by a branch 206 with an armature 208 of the control relay 203 and which engages'a contact 209 when the winding 204 is deenergized.

The line 201 of the manual return switch 200 is connected by a branch line 210 with one contact of a normally open manual start switch 211, the other contact of this start switch being connected by a line 212 with the winding 50 of the four way solenoid valve 43. A branch line 213 of this line 212 connects with the end of the winding 204 opposite the main power line and also with the armature 205. A second branch 214 connects with the stationary contact of a slow down limit switch 215, movable contact 216 of which is opened during the final part of the descent of the main ram 8 by contact with a cam 218 mounted on the upper movable platen 7. The movable contact 216 of this slow down limit switch is connected by a line 219 with the winding 59 of the solenoid valve 35, the other end of this winding being connected by a line 220 with the main power line 195. A branch 221 of this line 220 connects with the winding 222 of a control relay 223, the other end of this winding being connected by a line 224 with the movable contact 225 of the return limit switch 226, this return limit switch being opened by engagement of the movable contact 225 thereof with the earn 218 mounted on the upper movable platen 7 during the final part of the return stroke of the main ram 8. The fixed contact of this return limit switch 226 is connected by a line 228 with the fixed contact 209 of the control relay 203.

The winding 48 of the four way solenoid valve 33 is connected across the lines 220 and 224 by branch. lines 229 and 230. The line 220 is also connected by a branch line 231 with the end of the winding 50 opposite the line 212.

In the energized condition of the winding 222 of the control relay 223, its normally open armature 232 is drawn into engagement with a fixed contact connected by a line 234 with the main power line 196. This armature 232 is connected by a line 235 with the normally open armature 236 of an adjustable time relay 238. This relay is characterized by being cocked or set up when energized, its timing commencing when it is deenergized. The winding 239 of this adjustable time relay is connected by a line 240 to a branch line 241 of the main power line 195 and thte other side of this winding 239 is connected by a line 242 to an armature 243 which is drawn into engagement with the fixed contact 244 of a line 255 connected with the movable contact 256 of the normally open pressure switch 191.

The line 242 connected with the winding 239 of the adjustable time relay 238 also connects with one stationary contact 260 engaged by the normally closed contact 261 of a double pole, double throw depth of fill limit switch indicated generally at 262. This depth of fill limit switch 262 is mounted on the upper movable platen 7. This movable contact 261 of the depth of fill limit switch 262 is connected by a line 263 with the stationary contact 264 of the pressure switch 191.

The depth of fill limit switch 262 includes a second normally open movable contact 265 which is connected by a line 266 with a third armature 268 of the control relay 203, this armature 268 being drawn into engagement with a fixed contact 269 connected by a line 270 with the main power line 196.

The movable contacts 261 and 265 of the depth of fill limit switch 262 are connected and are arranged to be moved upwardly by a spring depressed actuator rod 271 which is arranged in the vertical passage 21 through the upper movable platen 7 and upper dimensional stop 9 with its lower end in position to engage the lower dimensional stop 5 on the lower movable platen 3. The upper end of this actuator rod 271 is Provided with an arm 272 which engages and lifts the movable contact 261 of the depth of fill limit switch 262 when the actuator rod strikes the dimensional stop 5 and is lifted suiticiently relative to the upper movable platen 7.

The movable contact 265 of the depth of fill limit switch 262 is connected by a line 275 with one fixed contact 276 of an adjustable time relay 278. This adjustable time relay, as with the adjustable time relay 238, is characterized by being in the nature of a cocking relay in that upon energization it is merely set up and its timing commences when it is deenergized. This fixed contact 276 is engaged by a normally open armature 277 which is connected by a line 279 with the fixed contact of the normally closed pressure switch 190. The movable contact 280 of this normally closed pressure switch 190 is connected by a line 281 with the fixed contact 282 of the depth of fill limit switch 262 and which fixed contact is engageable with its normally open movable contact 265.

The winding 285 of the adjustable time relay 278 is connected across the lines 241 and 279 by lines 286 and 288, respectively. This adjustable time relay 278 has a second normally open armature 289 which is connected by a line 290 with the line 235 connecting the armature 232 of the control relay 223 with the armature 236 of the adjustable time relay 238.

The remainder of the electrical circuit is concerned with the reversing line starter 300 for the motor M. This reversing line starter has a decrease winding 301, connected by a line 302 with the branch 241 of the main power line 195, and an increase winding 303 also connected by a line 304 with the branch 241 of the main power line 195. The other side of the decrease coil 301 is connected by a line 305 with a fixed contact 306 of the adjustable time relay 23S and which is engageable with the normally open armature 236 of this relay. The

other side of the increase coil 303 is connected by a line 307 with a fixed contact 308 of the adjustable time relay 278 and which contact is engageable with the normally open armature 289 of this relay.

Energization of the decrease coil 301 of the reversing line starter 300 closes three normally open armatures 310, 311 and 312. The armature 310 is connected by a line 313 with the branch 241 of the main power line 195. The armature 311 is connected by a line 314 with a branch 315 of the main power line 196. The armature 312 is connected by a line 317 with the main power line 198. The armature 310 is drawn into engagementwith a fixed contact 318 at the end of a line 319 leading to the reversing motor M. The armature 311 is drawn into .4

engagement with a fixed contact 320 connected with a motor line 321 leading to the reversing motor M. The armature 312 is drawn into engagement with a fixed contact 322 at the end of a motor line 323 leading to the motor M.

Energization of the increase coil 303 of the reversing line starter 300 closes three normally open armatures 325, 326 and 328 against fixed contacts 329, 330 and 331, respectively. The fixed contact 329 is at the end of the branch 241 of the main power line 195. The fixed contact 330 is at the end of the branch 315 of the main power line 196. The fixed contact 331 is at the end of the main power line 198. The armature 325 is connected with the motor line 321. The armature 326 is connected with the motor line 319. The armature 328 is connected with the motor line 323.

Operation of Fig. 2

The fundamental principle of the form of the invention shown in Fig. 2 is that a weight of a sample of any material is compressed to a given volume under the same pressure as any other sample of the same material having the same weight. Because of this principle, measurements of the sample taken during any part of the compression stroke of the press can be used as an indication of the final density of the sample when a predetermined final volume is reached. With measurements taken during any part of the compression stroke, it is apparent that the density tolerance of the sample when final volume is reached will be a direct function of (a) the compression curve of the 14 material, (b) the point of the compression stroke at which the measurements are taken and (c) the distance over the compression stroke over which such measurements are taken. However, it is also apparent that the actual shape of the compression curve for the particular material being formed is unimportant.

In Fig. 2 the brick press is shown at the end of the mold filling phase of the operating cycle of the press and in which phase a charge of material 23 for forming the brick has been placed in the mold cavity 2, this material having been leveled off along the top of the stationary intermedi ate platen 1 and being substantially the amount of material necessary to produce a brick of the desired dimensions and density. Since the apparatus for introducing the material 23 into the mold forms no part of the invention, this apparatus is not shown nor described.

By way of general description of the operation of the brick press;

1. If the quantity of material 23 in the cavity 2 is too small to produce a brick of the desired density, the depth of fill limit switch 262 will be actuated by the actuator rod 271 before either the pressure switch 190 or the pressure switch 191 is actuated. This sets up the electrical control system circuit to increase the depth of fill of the cavity 2 for the mold filling phase of the next cycle of operation of the press by energizing the increase winding 303 of the reversing line starter 300 as soon as the press opening phase of the present cycle commences.

2. If the quantity of material 23 in the cavity 2 is too great, the pressure switches 190 and 191 are both actuated before the depth of fill limit switch 262. This sets up the electrical control system to decrease the depth of fill of the cavity 2 by energizing the decrease winding 301 of the reversing line starter 300 during the press opening phase of the operating cycle thereby to decrease the amount of fill for the next cycle of operation.

3. If the quantity of material 23 in the cavity 2 is within the tolerance range of the proper amount, the pressure switch 190 is actuated, followed by actuation of the depth of fill limit switch 262 and this, in turn, followed by actuation of the pressure switch 191. With this sequence of operation neither the increase winding 303 nor the decrease winding 301 of the reversing line starter 300 is energized and hence no change in the-depth of fill of the cavity 2 takes place for the next cycle of press operation. The differential between the pressures necessary to operate either pressure switch and the pressure necessary to contact the limit switch determines the density tolerance and is adjustable.

To form the material 23 into a brick, the operator presses the start switch 211 so as to establish a circuit from the main power line196, line 199, closed return switch 200, line 210, switch 211, lines 212 and 213, winding 204 of control relay 203 to main power line 195. The energization of this winding 204 of the control relay 203 pulls its armature 205 into engagement with the contact 202 thereby to provide a holding circuit which is maintained after the start switch 211 is released, this circuit being from the main power line 196, line 199, closed return switch 200, line 201, contact and armature 202, 205 and winding 204 to the main power line 195.

The energization of the winding 204 of the control relay 203 also establishes a circuit from the main power line 196, through line 199, closed return switch 200, line 201, contact and armature 202, 205, lines 213, 212, winding 50 of the four way solenoid valve 33 and lines 231 and 220 to the main power line 195.

The energization of the winding 204 of the control relay 203 also establishes a circuit from the main power line 196, through line 199, closed return switch 200, line 201, contact and armature 202, 205, lines 213, 212 and 214, closed slow down limit switch 215, line 219,'winding 59 of solenoid valve 35, and line 220 to the main power elevated position and hence the cam 218 thereon is out of contact with the movable contact 216 of this normally closed switch.

As with the form of the invention shown in Fig. l, the closing cycle is initiated by the energization of the winding 50 of the four way solenoid valve 33 and the winding 59 of the solenoid valve 35. The energization of the former causes the plug 42 in the four way solenoid valve 33 to move downwardly as shown in Fig. 2, and the energization of the latter causes the piston 54 of the solenoid valve 35 to move to the right as shown in Fig. 2 and thereby establish communication from line 34 to line 62 and to block off line 60. Fluid under pressure from the main pump therefore passes from the outlet line 31 through branch 34, solenoid valve 35, and line 62 into the cylinder 74, thereby moving the piston 73 downwardly against the resistance of its Spring and opening the valve 70 to permit fluid to flow through the valve opening 71. The downward position of the plug 42 of the four way solenoid valve 33 causes this plug to direct volume from the main pump 39 through the lines 31 and 32, groove 44, and line 37 to the upper end of the main cylinder 11 above the piston head 10. At the same time fluid trapped under the piston head 10 is permitted to escape through the line 66, upper chamber 64 of the two way check valve 39, open valve port 71, lower chamber 65 of this valve 39, line 38 through the restriction 47, groove 43 in the plug 42 of the four way solenoid valve 33 and line 41 to the tank or reservoir 12. Under these conditions the ram 8 descends rapidly causing a back pressure to build up behind the restriction 47 in line 38. This back pressure is applied through the branch line 38a to the pilot cylinder 18 above the piston 16 of the prefill valve 14. This back pressure is sufiicient to move the piston 16 and prefill valve 14 downwardly against its spring thus allowing fluid to flow from the tank or reservoir 12 into the upper end of the cylinder 11 during this rapid part of the closing movement of the ram 8.

A small amount of such rapid downward movement of the ram 8 causes the cam 218 to release the armature 225 of the limit switch 226 and allows this armature to engage the stationary contact of line 228 and set up the circuit later used to return the ram 8.

Further progress of the ram 8 downwardly causes its cam 218 to engage the armature 216 of the limit switch 215 and moves this armature away from the stationary contact of the line 214 thus breaking the circuit through the winding 59 of the solenoid valve and which circuit was established by the relay 223 through the line 219. The spring 56 in the solenoid valve 35 then moves the plunger 54 to the left as viewed in Fig. 2, thereby to block offline 34 and to connect lines 62 and through the port 55 in the plunger 54. This last connection relieves the pressure behind the plunger 73 which had been overcoming the spring of the valve and allows this valve 70 to close under the influence of its spring. The setting or resistance of this spring is such that sufiicient back pressure is built up in the upper chamber 64 of the two way check valve 39 and in line 66 to support the main ram 8 and the other weights connected with this main ram. The closing of the valve 70 also eliminates the back pressure existing in lines 38 and 33a and hence the prefill valve 14- is permitted to close under the influence of its spring and thereby cut oif the direct flow of liquid from the reservoir 12 to the upper end of the cylinder 11. However, the main pump 30 is still delivering fluid into the upper end of the main cylinder 11 through lines 31, 32, groove 44 in the plug 42 of valve 33, and line 37 to the upper end of the main cylinder 11, and with the prefill valve 14 closed, main pump pressure commences to build up in the upper end of the main cylinder 11 and drive the main piston 10 and ram 8 downwardly. This downward movement of the main piston 10 forces the liquid under this piston to escape through line 66 to the upper chamber 64 of the two way check iii) iii

valve 39. This pressure is sufficient to overcome this spring of the valve 70 and to force this valve open. Accordingly the speed of further descent of the main ram is determined by the delivery of the main pump 30.

The descent of the main ram 8 continues until a back pressure against the liquid above the piston head 10 builds up to a value where it opens the relief valve 52 and bypasses the iiquid from the main pump 30 through the lines 37 and 51 into the tank or reservoir 12. This back pressure is produced by the engagement of the dimensional stops 5 and 9 of the press. It is to be noted, however, that the dimensional stops 5 and 9 are brought into engagement so that under all conditions of continuous operation, bricks of the same dimensions within very close tolerances are produced.

During the descent of the ram 8 and while the material 23 is being compressed, the pressure in the cylinder 11 above the piston head 10 rises in conformity with the graphic curve or pattern of compressibility of the material 23 in the cavity 2. Therefore, at some point during this compression stroke, pressure switch will be actuated so as to open its normally closed contact 280, and at some later point, when the pressure in the cylinder 11 above the piston head 10 is higher, pressure switch 191 will be actuated to cause its movable contact 256 to engage its stationary contact 264. After the dimensions of the material 23 in the cavity 2 are corrected as determined by previous actuation of the pressure switches 199, 191, the depth of fill will be correct. The proper setting of the limit switch 262 under this condition is such that it will be actuated by the arm 272, the movement of which is determined by the position of the ram 8 between the positions of this ram when its back pressure was such as to actuate pressure switches 190 and 191. At this time it shall be assumed that the arm 272 actuates the limit switch 262 prior to the operation of either the pressure switch 190 or the pressure switch 191.

As previously noted, this sequence of operation of these switches operates to set up the electrical control system forenergization of the increase winding 303 of the reversing line starter 300 thereby to increase the depth of fill of the cavity 2 for the next cycle of operation. The circuit so set up is completed by the operator pressing the return switch 200. Thus, under this assumed sequence of operation of the depth of fill limit switch 262 before either of the pressure switches 190 and 191, a circuit is established from main power line 196, line 270, contact and armature 269, 268 of control relay 203, line 266, closed contacts 265 and 282 of the depth of fill limit switch 262, line 281, closed pressure switch 190, lines 279 and 288, winding 285 of adjustable time relay 278 and lines 286 and 241 to the main power line 195.

The energization of this winding 285 of the adjustable time relay 2'73 pulls up its armature 277 so as to establish a circuit from the main power line 195, through lines 241, 286, winding 285 of adjustable time relay 278, lines 288 and 279, closed armature and contact 277 and 276 of this adjustable time relay 278, lines 275 and 266, closed armature and contact 263, 269 of the control relay 203, and line 276 to the main power line 196. This locks the energization circuit for the winding 285 of the adjustable time relay 278 for as long as the winding 204 of the control relay 203 remains energized. As previously indicated, the adjustable time relay 278 commences its a) timing at the start of the deenergization thereof. It is to be noted that the energization of the adjustable time relay 278 also pulls up its armature 289 into engagement with the contact 308, but this is ineffective at this time to energize the increase winding 303 of the reversing line starter 300 because this circuit is broken at the armature 232 of the control relay 223. I a

To begin the press opening phase of the operating cycle, the operator presses the return switch 200 and opens the holding circuit through the winding 204 of the control relay 203 to permit its armatures 205, 268 and 208 to assume the position shown in Fig. 2. This operates to deenergize the winding 50 of the four way solenoid valve 33 since one side of this winding is energized through the lines 2l2 and 213 and armature 205 on the control relay 203 which is opened by the deenergization of this relay 203. At the same time the opposite winding 48 of'the four way solenoid valve 33 is energized through a circuit comprising the main line 196, line 206, armature, and contact 208, 209 of control relay 203, line 228, closed return limit switch 226, lines 224 and 229, winding 48 and lines 230 and 220 to the main power line 195.. Energization of winding 48 of the four way solenoid valve 33 moves its plug 42 to connect the branch 32 of the main pump discharge, through the groove 44, with the line 38 leading to the two way check valve 39 and cylinder 18 of the prefill valve 14. Accordingly, the prefill valve 14 is moved to the open position shown so that liquid above the piston head is free to escape directly from the upper end of the bore of the main cylinder 11 into the tank or reservoir 12. Also, main pump pressure is supplied from theline 38 to the lower chamber 65 of the two way check valve 39.- This pressure opens the check valve 68 in its free flow direction and permits the escape of this fluid through the port 69 and upper chamber 64 of the two way check valve 39 and through the line 66 to the main cylinder 11 below the piston head 10 so that the piston head is forced to rise. The movement of the plug 42, when the winding 48 of thefour way solenoid valve 33 is so energized, also connects the line 37 from the upper end of the bore of the main cylinder 11, through the groove 45, to the branch 40 of the line 41 leading to the tank or reservoir 12.

During the initial part of this return movement-of the main ram 8, the normally closed slow down limit switch 215 is permitted to reclose by disengagement of the earn 218 on the upper movable platen 7 from the movable contact 216 of the slow down limit switch. However, this closing has no effect at this time because the circuit through this switch is open at the armature 205 of the control relay 203.

Inasmuch as, at this time, as previously described, the adjustable time relay 278 is energized or cocked, the deenergization of the control relay .203, caused by the operator pressing the return switch 200, operates to deenergize the winding 285 of this adjustable time relay since the holding circuit therethrough is broken at armature 268 of the control relay 203. This causes the adjustable time relay 278 to begin to run for the period of time for which it has been set and it is to be noted that its armature and contact 289, 308 remain engaged until this period of time has elapsed.

The deenergization of the control relay 203 also energizes the winding 222 of the control relay 223.- This energization is from the main power line 196, through line .206, closed armature and contact 208, 209 or the control relay 203, line 228, closed return limit switch 226, line 224, winding 222 of the control relay 223 and lines 221 and 220 to the main power line 195. The energization of the control relay 223 with the adjustable time relay 278 so energized, establishes a circuit through the increase winding 303 of the reversing line starter 300. This circuit is from the main power line 196 'line 234, closed armature 232 of control relay 223, lines 235 and 290, closed armature and contact 289, 308 of the adjustable time relay 278, line 307, increase winding 303.

of the reversing line starter 300, and lines 304 and 241 to the main power line 195. It1is to be noted at this time that this circuit through the increase winding 303 of the reversing line starter 300 is maintained for the period of time for which the adjustable time relay 278 has been set and that at the end of this time the adjustable time relay 278 releases to break this circuit through its armature and contact 289, 308. I

This energization of the increase winding 303 of the reversing line starter 300 draws its armatures 3'25, 3'26 and 328 into engagement with the fixed contacts329, 330 and 331, respectively. This connects the motor line 321 with the main power line 195 through the closed armature and contact 325, 329 and branch line 241. This also connects the motor line 319 with the main power line 196 through the closed armature and contact 326, 330 and branch line. 315. This also connects the motor line 323 with the .main power line 198 through the closed armature and contact 328, 331. With the motor lines 321, 319. and 323 so connected withthe main power lines 195, 196 and 198, the motor. M is energized to rotate in the direction to lower the bottom plunger 4 and thereby increase the. vertical extent or depth offill of the cavity 2. I

n In the immediate preceding description of operation, itwas assumed that the quantity of material 23 in the cavity 2 was too small to provide a brick of the desired dimensions and density and that accordingly the depth of fill limit switch 262 was actuated before either of the pressure switches or 191. Assuming now that the cavity 2 contains too great a quantity of material 23 to provide a brick of the desired dimensions and density, the pressure switches 190 and 191 are both actuated before the depth of fill limit switch 262 so as to energize the decrease winding 301 of the reversing line starter 304..

Thus, with too great a quantity of material in the cavity 2, the upper movable platen 7 is prevented from descending to a point where the actuator rod 271 will operate .the contacts of the depth of fill limit switch 262 until the pressure switches 190 and 191 are actuated by the back pressure built up in the upper end of the cylinder 11. Under these conditions a circuit is established from the main power line 195, lines 241 and240, winding 239 of adjustable time relay 238, line 242, closed contacts 260 and 261 of depth of fill limit switch 262, line 263, closed pressure switch 191, lines 255, 275 and 266, closed armature and contact 268, 269 of control relay 203 and line 270 to the main power line 196.

Energization of the adjustable time relay 23 8 pulls up its armatures 243 and 236, and the pulling up of its armature 243 provides a holding circuit for maintaining the .winding 239 of this adjustable. time relay 238 energized until broken at the armature 268 of the control relay 203 when this relay is deenergized. This holding circuit comprises the main power line 195, lines 241 and 240, winding 239 of adjustable time relay 238, closed armature and contact 243, 224 of this, relay, lines 255, 275 and 266, closed armature and contact 268, 269 of control relay 203 and line 270 to the main power line 196. V b

At this point it is noted that, as with the other adjust able time relay 278, the adjustable time relay 238 is cooked or set for operation by the energization' of. its

winding 239 and that its timing commences when the circuit through its winding 239 is broken at which time its armatures remain closed for the period of time determined by the setting.

Inasmuch as under the conditions now assumed the adjustable time relay 238 has been energized or cocked, the deenergization of the control relay 203 occasioned by the operator pressing the return switch 200 operates to deenergize the winding 239 of this adjustable time relay since the-holding circuit therethrough is broken at armature 268 of the control relay 203. This causes the adjustable-time relay 238 to begin to run for the period of time .forwhich it has been setand it is to be noted that its armature and contact 236, 306 remain engaged until this period of time .has elapsed.

Accordingly, during this period of time a circuit ;is closed through the decrease winding 301 of the revers ingline starter 300. 'This circuit is from the main power line 195, lines 241, 302, decrease winding 3.01 .of the reversing line Starter 300, line 305, closed contact and armature .306, "236 of the adjustable time relay 238, line 235, closed armature 232 of control relay 223,, and line 234 to the main powei line 196. 'Energization of the decrease winding 301 of the reversing line starter 300 pulls up the armatures 310, 311 and 312 soas to engage these armatures with their respective contacts 318, 320 and 322. This connects the motor line 319 through the lines 313 and 241 with the main power line 195; the motor line 321, through the lines 314 and 315 with the main power line 196; and the motor line 323 through the line 317 to the main power line 198. This connection of these three motor lines with the three main power lines energizes the motor M to rotate in the direction to raise the bottom plunger 4 and hence decrease the depth of the cavity 2 and thereby decrease the depth of fill during the next operating cycle of the brick press. This movement of the bottom plunger 4 andmotor M continues only so long as the adjustable time relay 238 is operating during its time cycle.

If the cavity 2 contains exactly the right amount of material to produce a brick of the desired dimensions and density, the pressure switch 190, depth of fill limit switch 262 and pressure switch 191 are operated in this sequence and in such sequence neither of the adjustable time relays 278 or 238 are energized or cocked so that neither the increase coil 303 nor the decrease coil 301 of the reversing line starter 300 are subsequently energized. Accordingly, the motor M is not energized to rotate in either direction during the return strokeof the ram 8 and therefore no change in the relative position of the bottom plunger 4 with reference to the intermediate stationary platen or mold 1 is made so that the same depth of fill of the cavity 2 is maintained for the next operating cycle of the press. 7

Thus, with the switches'190, 262 and 191 operating in this sequence, the initial opening of the pressure switch 190 has no effect in closing the circuit through the adjustable time relay 278 because of the opening of this switch. The closing of the contacts 265 and 282 of the depth of fill limit switch 262'subsequent to the operation of the pressure switch 190 likewise has no effect in closing the circuit through the adjustable time relay 278 because at this time the contacts of the normally closed pressure switch 190 are open. The closing of the contacts of the pressure switch 191 subsequent to the oper ation of the depth of fill limitswitch 262 likewise has no effect in closing the circuit through the adjustable time relay 238 because at this time the contacts 260 and 261 of the depth of fill limit switch 262 are open. Accordingly, it will be seen that this sequenceof switch operation: namely first the pressure switch 190, then the depth of fill limit switch 262, and then the pressure switch 191, has no elfect in closing any circuit and hence with this sequence neither of the adjustable time relays 278 and 238 are energized to set up the circuit for a depth of fill readjustment. v It will be observed that the depth of fill adjustment of the bottom plunger 4 by the motor M, if any, takes place during the press opening phase of the operating cycle of the press. As the main ram 8 reaches the end of its return stroke in this phase, its cam 218 engages the movable contact 225 of the return limitswitch 226 and opens this switch. Opening of this return limit switch 226 breaks the circuit through the winding 222 of the control relay 223 and also through the winding 48 of the four way solenoid valve 33. Accordingly the parts are returnedto the position assumed at the start of the description of the operation preparatory to another cycle of operation.

, It will be appreciated that the invention can be practiced with different types of presses and that the form of the electrical circuits as described can be varied to a larger degree and still carry out the concept of the invention. The invention is therefore not to be construed as limited to the particular embodiments shown but is to be accorded the full range of equivalents comprehended by the accompanying claims. I

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, .20 I claim 1. In a molding press having 'a mold and a-top plunger and a bottom plunger cooperating with said mold'and forming atop'anda bottom respectively thererr, and dimensional stops moving with said plungers for controlling the minimunispacing therebetween, said press having an operating cycle including a mold filling phase during which the mold is filled with material, a pressing phase during which at leaston'e of said plungers' moves relative to the other to compress the material and a press opening phase during which said plungers move away from each other; the combination therewith of means for automatically adjusting 'the depth of fill of the mold, which comprises an electricalcontrol'system responsive to the spacing ofsaid dimensional stops 'at the end of the pressing phase in one operating cycle for adjustingthe' relative position of said bottom plunger with respect to said mold during the mold filling phase of the next suc ceeding operating cycle, said electrical control system comprising electromotivated means includinga reversible motor, a reversing line starter for said reversible motor and having a decrease winding and an increase winding one side of each of which is connected to an electrical supply line, a control relay having a pair of normally closed contacts'in circuit with the other side of said decrease winding and a pair of normally opencon-' tacts in circuit with the other side of said increase winding, timer means arranged to connect that contact of each of said pairs thereofremote from the respective winding with another electrical supply line for'a predetermined period of time during the press opening phase of oneoper ating cycle whereby a closed circuit is established through one of said windings, and normally open switch means arranged in the energization circuit of said control relay and responsive'to the spacing of said dimensional stops at the end of the pressing phase of said one operating'cycle for controlling the energization of said control relay so as to permit, during the press opening phase of said one operating cycle, energization of said decrease winding when said switch means remain open and energization of said increase winding when said switch means'are closed.

2. In a molding press having a mold and a top plunger and a bottom plunger cooperating with said mold and forming a top and a bottom respectively therefor, and dimensional stops moving with said plungers for controlling the minimum spacing therebetween, said press having an'operating cycle including a mold filling phase during which the mold is filled with material, a pressing phase during which at least one of said plungers' moves relative to the other to compress thejmaterial and a press opening phase during which said plungers move away from each other; the combination therewith of means for automatically adjusting the depth of fill of the mold, which comprises an electrical control sy'stem'responsive to' the spacing of said dimensional stops at the end at the pressing phase'in one operating cycle for adjusting the relative position of said bottom plunger with respect to said mold. during the mold filling phase of the next succeeding operating cycle, said electrical control system comprising electro-motivated means including a reversible motor, a reversing line starter forsaid reversible motor and having" a decrease winding and an increase winding one side of each of which is connected to an electrical supply line, aiirst control relay having a pair of normally closed contacts in circuit with the other side of said decrease winding and a pair of normally open contacts in circuit with the other side of' said increase winding, timer means arranged. to connect that contact of each of said pairs thereof remote from the respective one of said windings with another electrical supplyline said timer means [when energized establishing a closed circuit through one of said windings for a predetermined length of time, a second controlrelay having its normally open contacts arranged in the energization circuit for said timer means and 3150 arranged inthe energization circuit'for said first control relay, means operative at the. beginning of the press opening phase to energize said second control relay thereby to close its said contacts, and normally open switch means arranged in the energization circuit of said first control relay and responsive to the spacing of said dimensional stops at the end of the pressing phase of said one operating cycle for controlling the. energization of said first control relay so as to permit, during the press opening phase of said one operating cycle, energization of said decrease winding when said switch means remain open and energization of said increase winding when said switch means are closed.

3. In a hydraulic press having a mold and atop plunger and a bottom plunger cooperating with said mold and forming a top and a bottom therefor, said press having an operating cycle including a mold filling phase during which the mold is filled with material, a pressing phase during which at least one of said plungers moves relative to the other to compress the material and a press opening phase during which said plungers move away from each a other; the combination therewith of means for automatically adjusting the depth of fill of the mold, which comprises an electrical control system responsive to the spacing of said plungers during any portion of the pressing phase of one operating cycle for adjusting the relative position of said bottom plunger with respect to said mold during the press opening phase of the said operating cycle, said electrical control system comprising electro-motivated means including a reversible motor, a reversing line starter for said reversible motor and having a. decrease winding, and an increase winding, a normally closed pressure switch and a normally open pressure switch both arranged to be actuated in response. to. the. pressure. of the hydraulic fluid utilized to close the press. during the pressing phase of the operating cycle thereof, one of said pressure switches being operatively associated. with the energization circuit for one of said windings and the other of said pressure switches being operatively associated with the energization circuit for the other of said windings, and, a third switch means responsive to the. spacing of said plungers during the pressing phase of one operating cycle for determining which, if any, one of said windings is to be energized duringthe press opening phase of said. one operating cycle, said third switch means including a. pair of normally open contacts in circuit with said normally closed pressure switch and also including a pair of normally closed contacts in. circuit with said normally open pressure switch.

4. A. hydraulic molding press according to claim 3, in which said electrical control system further comprises timer means included in the energization circuit of each of said decrease and increase windings whereby any ener-- gization thereof is for a predetermined period of time.

5. In a. hydraulic press having a mold and a top. plunger and a bottom plunger cooperating with. said mold and forming a top. and a bottom therefor, saidpress having anoperating cycle including a mold filling. phase during; which the mold is filled with material, a pressing phase during which at least one of said plungers moves relative to the other to compress the material and a press opening phase during which said plungers move away from each other; the combination therewith of means for automatically adjusting the depthof fill of the mold, which comprises an electrical control system responsive to the spacing of. said plungers during any portion of the pressing phase of one operating cycle for adjusting the relative position of said bottom plunger with respect to said. mold; during the press opening phase of said operating cycle, said electrical control system comprisingelectro-motivated means including a reversible motor, a, reversing line starter for said reversible motor and having a. decrease winding and an increase winding, a first time relay having a pair of normally open contacts arranged in the energization circuit of one of said decrease and increase windings, a second time relay having a pair of normally open contacts arranged in the energization circuit of the other of said decrease and increase windings, a normally closed pressure switch and a normally open pressure switch arranged to be actuated in response to the pressure of the hydraulic fluid utilized to close. the press during the pressing phase of the operating cycle thereof, one of said pressure switches being arranged in the energization circuit of one of said time relays and the other of said pressure switches being arranged in the energization circuit for the other of said time relays, and a third switch means responsive to.

the spacing of said plungers during any portion of the pressing phase of one operating cycle for controlling the energization of said windings during the press opening phase of said one operating cycle, said third switch means including a pair of normally open contacts in circuit with said normally closed pressure switch and also including a pair of normally closed contacts in circuit with said normally open pressure switch.

6. In a hydraulic press having a mold and a top plunger and a bottom plunger cooperating with said mold and forming a top and a bottom respectively therefor, and dimensional stops moving with said plungers for controlling the minimum spacing therebetween, said press having an operating cycle including a mold filling phase during which the mold is filled with material, a pressing phase during which at least one of said plungers moves relative tov the other to compress the material and a press opening phase during which said plungers move away from each other; the combination therewith of means for automatically adjusting the depth of fill of the mold,

" which comprises an electrical control system responsive to phase of the said operating cycle, said electrical control system comprising electro-motivated means including, a reversible motor, a reversing line starter for said toversible motor and having a decrease winding and an in- I crease winding, a first time relay having a pair of nor- I mally open contacts. arranged in the energization circuitv of said decrease winding and said first time relay, when. energized, closing its said contacts and holdingthem. closed for a predetermined period of time after said first time relay is deenergized, a second time relay having, a pair of normally open contacts arranged in the energization circuit of said increase winding and said second time. relay, when energized, closing its said contacts and holding them closed for a predetermined period of time after said second time relay is deenergized, a third control relay having its normally open contacts arranged in the normally open pressure switch.

energization circuits of said windings,- means operative at the beginning of the press opening phase to energize said third control relay thereby to close its said contact-s,v a normally closed pressure switch and a normally open pressure switch arranged to be actuated in response to the pressure of the hydraulic fluid utilized to close the press during the pressing phase of the operating cyclethereof, said normally open pressure switch being arranged in the energization circuit of said first time relay, said normally closed pressure switch being arrangedv inthe energization circuit of said second time relay, and depth of fill switch means responsive to the spacing of said dimensional stops during any portion of the pressing phase. of one operating cycle for controlling the energization of said winding during the press opening phase of said one operating cycle, said depth of fill switch means including a pair of normally open contacts in circuit with said .normally closed pressure switch and also including, a pair of normally closed contacts in circuit with said 7, In a molding press having a mold and a and a bottom plunger cooperating with said mold and forming a top and. a bottom respectively therefor, said press having an operating cycle including a mold filling top plunger phase during which the mold is filled with material, a pressing phase during which at least one of said plungers moves relative to the other to compress the material and a press opening phase during which said plungers move away from each other; the combination therewith of means for automatically adjusting the depth of fill of the mold, which comprises an electrical control system responsive to the spacing of said plungers at the end of the pressing phase in one operating cycle for adjusting the relative position of said bottom plunger with respect to said mold during the mold filling phase of the next succeeding operating cycle, said electricalcontrol system comprising electro-motivated means including a reversible motor, switch means for controlling the direction of motion of said reversible motor, and timing means for automatically stopping the operation of said reversible motor after a predetermined running period, said switch and timing means influencing said relative position of said bottom plunger.

8. In a molding press having a mold and a top plunger and a bottom plunger cooperating with said mold and forming a top and a bottom respectively therefor, said press having an operating cycle including a mold filling phase during which the mold is filled with material, a pressing phase during which at least one of said plungers moves relative to the other to compress the material and a press opening phase during which said plungers move away from each other; the combination therewith of means forautomatically adjusting the depth of fill of the mold, which comprises an electrical control system responsive to the spacing of said plungers at the end of the pressing phase in one operating cycle for adjusting the relative position of said bottom plunger with respect to saidmold during the mold filling phase of the next succeeding operating cycle, said electrical control system comprising electro-motivated means including a reversible motor operatively arranged to adjust said relative position of said bottom plunger, a reversing line starter for said reversible motor and adapted to control the direction of motion thereof, means for controlling said reversing line starter for influencing the direction of motion of said reversible motor, and timing means for automatically stopping the operation of said reversible motor after a predetermined running period.

9. In a molding press having a mold and a top plunger and a bottom plunger cooperating with said mold and forming a top and a bottom respectively therefor, said press having an operating cycle including a mold filling phase during which the mold is filled with material, a pressing phase during which at least one of said plungers moves relative to the other to compress the material and a press opening phase during which said plungers move away from each other; the combination therewith of means for automatically adjusting the depth of fill of the mold, which comprises an electrical control system responsive to the spacing of said plungers at the end of the pressing phase in one operating cycle for adjusting the relative position of said bottom plunger with respect to said mold during the mold filling phase of the next succeeding operating cycle, said electrical control system comprising electro-motivated means including a reversible motor operatively arranged to adjust said relative position of said bottom plunger, a reversing line starter for said reversible motor and adapted to control the direction of motion thereof, switch means responsive to the spacing of said plungers at the end of the pressing phase for controlling said reversing line starter as to influencing the direction of motion of said reversible motor, and timing means for automatically stopping the operation of said reversible motor after a predetermined running period.

10. In a molding press having a mold and a top plunger and a bottom plunger cooperating with said mold and forming a top and a bottom respectively therefor, said press having an operating cycle including a mold filling phase during which the mold is filled with material, a pressing phase during which at least one of said plungers moves relative to the other to compress the material and a press opening phase during which said plungers move away from each other; the combination therewith of means for'automatically adjusting the depth of fill of the mold, which comprises an electrical control system responsive to the spacing of said plungersat the end of thepress'ing phase in one operating cycle for adjusting the relative position of said bottom plunger with respect to said" mold during the mold filling phase of the next succeeding operating cycle, said electrical control system comprising electro-motivated means including a reversible motor, a reversing line starter for said reversible motor and having a decrease winding and an increase winding, means arranged to energize one of said windings for a predetermined period of time during the press opening phase of one operating cycle, and switch means responsive to the spacing of said plungers at the end of the pressing phase of said one operating cycle for determining which one of said windings is to be energized during the press opening phase of said one operating cycle.

11'. In a molding press having a mold and a top plunger and a bottom plunger cooperating with said mold and forming a top and a bottom respectively therefor, said press having an operating cycle including a mold filling phase during which the mold is filled with material, a pressing phase during which at least one of said plungers moves relative to the other to compress the material and a press opening phase during which said plungers move away from each other; the combination therewith of means for automatically adjusting the depth of fill of the mold, which comprises an electrical control system responsive to the spacing of said plungers at the end of the pressing phase in one operating cycle for adjusting the relative position of said bottom plunger with respect to said mold during the mold filling phase of the next succeeding operating cycle, said electrical control system comprising electro-motivated means including a reversible motor, a reversing line starter for said reversible motor and having a decrease winding and an increase winding, a control relay having a pair of contacts arranged in the energization circuit for each of said windings, one of said pair of contacts being normally closed and the other pair being normally open, means arranged to energize one contact of each of said pairs thereof for a predetermined period of time during the press opening phase of one operating cycle, and switch means responsive to the spacing of said plungers at the end of the pressing phase of said one operating cycle for controlling the energization of said control relay to determine which one of said windings is to be energized during the press opening phase of said one operating cycle.

12. In a molding press having a mold and a top plunger and a bottom plunger cooperating with said mold and forming a top and a bottom respectively therefor, said press having an operating cycle including a mold filling phase during which the mold is filled with material, a pressing phase during which at least one of said plungers moves relative to the other to compress the material and a press opening phase during which said plungers move away from each other; the combination therewith of means for automatically adjusting the depth of fill of the mold, which comprises an electrical control system responsive to the spacing of said plungers at the end of the pressing phase in one operating cycle for adjusting the relative position of said bottom plunger with respect to said mold during the mold filling phase of the next succeeding operating cycle, said electrical control system comprising electro-motivated means including a reversible motor, a reversing line. starter for said reversible motor and having a decrease winding and an increase winding one side of each of which is, connected to an electrical supply line, a control relay having a pair of normally open contacts in circuit with the other side of one of said windings and a pair of normally closed contacts in circuit with the other side of the other of said windings, timer means arranged to connect that contact of each of said pairs thereof remote from the respective winding with another electrical supply line for a predetermined period of time during the press opening phase of one operating cycle whereby a closed circuit is established through one of said windings, and switch means responsive to the spacing of said plungers at the end of the pressing phase of said one operating cycle for controlling the energization of said control relay to determine which one of said windings is to be energized during the press opening phase of said one operating cycle.

13. In a molding press having a mold and a top plunger and a bottom plunger cooperating with said mold and forming a top and a bottom respectively therefor, said press having an operating cycle including a mold filling phase during which the mold is filled with material, a pressing phase during which at least one of said plungers moves relative to the other to compress the material and a press opening phase during which said plungers move away from each other; the combination therewith of means for automatically adjusting the depth of fill of the mold, which comprises an electrical control system responsive to the spacing of said plungers at the end of the pressing phase in one operating cycle for adjusting the relative position of said bottom plunger with respect to said mold during the mold filling phase of the next succeeding operating cycle, said electrical control system comprising electro-motivated means including a reversible motor, a reversing line starter for said reversible motor and having a decrease winding and an increase winding one side of each of which is connected to an electrical supply line, a first control relay having a pair of normally open contacts in circuit with the other side of one of said windings and a pair of normally closed contacts in circuit with the other side of the other of said windings, a second control relay having its normally open contacts arranged to connect that contact of each of said pairs of said first control relay contacts which is remote from the respective one of said decrease and increase windings with another electrical supply line, a timer having its normally open contacts arranged in the energizaticn circuit for said second control relay, a third control relay having its normally open contacts arranged in the energization circuit for said timer, means operative at the beginning of the press opening phase to energize said third control relay and thereby actuate said timer whereby a closed circuit is established through one of said windings for a predetermined period of time, and switch means responsive to the spacing of said plungers at the end of the pressing phase of said one operating cycle for controlling the energization'of said first control relay to determine which of said windings is to be energized during the press opening phase of said one operating cycle.

References Cited in the file of this patent UNITED STATES PATENTS 2,256,798 Yeakel Sept. 23, 1941 2,455,823 Tauber et al. Dec. 7, 1948 2,618,833 Adams Nov. 25, 1952

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