Means for squaring tie bars for die casting machines

A system and machine for squaring tie bars for die casting machines in which a detector means is provided for each of the tie bar nuts for separately and individually detecting the relative positions of the tie bar nuts of each of the tie rods whereby when the machine is originally squared by adjusting the adjustable means, the original squared positions of the nuts are detected and after operation of the machine it can be resquarded by adjusting said adjustable means to adjust said tie bar nuts back to their original squared positions. This adjustment is automatically accomplished through a logic circuit which controls the adjustment of the tie bar nuts.

The present invention relates to die casting machines of the type having 
tie bars and particularly to a system for resquaring the platens of the 
machine to their original square position. 
In die casting machines of the type disclosed in U.S. Pat. RE No. 32,048 
entitled TIE BAR ADJUSTMENT SYSTEM and in U.S. Pat. No. 4,466,477 entitled 
DIE CASTING MACHINE WITH STRAIN GAUGE, platens are provided between which 
the mold or die is located. One of these platens at the front of the 
machine is stationary and the other platen is a traveling platen which 
opens and closes the die or mold located between the two platens. Normally 
four tie rods are provided at the corners of the platens. These tie rods 
are secured to the front platen and also to a rear end plate. The 
traveling platen slides on these tie rods and is actuated by a hydraulic 
cylinder actuated toggle located between the traveling platen and the rear 
end plate. Located on the ends of the tie rods at the rear end plate are 
adjustment nuts or tie rod nuts, one for each of the tie rods, for 
adjusting the tension for each of the tie bars, it being desirable that 
the four tie bars share equally in the lock-up force exerted on the die 
when the traveling platen is in the lock-up position. 
When a die casting machine is originally built and before it is delivered, 
the manufacturer generally squares the machine, i.e., adjusts the 
adjustment nuts on the tie bars so that the two platens are parallel. This 
is accomplished by placing a squaring block between the front platen and 
the traveling platen and adjusting the tie rod nuts so that the tie bars 
share equally in the lock-up force exerted on the squaring block which has 
front and rear faces parallel to a known tolerence. In other words, a 
squaring block is inserted between the front and traveling platens and the 
traveling platen is actuated to the closed or lock-up position. Strain 
measurements are made on the tie bars to determine if load is uniform 
among them. If not, the traveling plate is actuated to the open position. 
Then the adjustment nuts on the ends of the tie rods are adjusted. The 
traveling plate is then again actuated to the closed position and strain 
measurements are again made. This process is repeated until the identical 
strain is being exerted in each of the tie bars. When the strain is the 
same in each tie bar, the machine is said to be "square", that is, there 
is equal tonnage on all corners of the squaring block simultaneous with 
the faces of the platens being parallel to a known tolerence. 
After the die casting machine is delivered, frequent operation of the same 
on almost a continuous basis causes wear and tear on the die and when 
metal leaks between the die halves the assumption may be that the machine 
is not square. A measure of the strain on each tie rod may determine that 
the strain in each tie rod is substantially different. 
In this case the remedy is to adjust the tie bars, after using the 
automatic method disclosed in U.S. Pat. RE No. 32,048, so that equal tie 
bar strain and therefore load distribution on the die is accomplished. 
This then permits continued use of dies with minimum metal leakage or 
flash, in spite of the fact that said die is no longer clamped by parallel 
platens. Use of the die casting machine in this manner is desirable in 
order to overcome the wear and tear on dies and thus extend their useful 
lives. It is also desirable in the case where dies have complex, 
non-uniform components which can operate at different temperatures and can 
develop non-parallel faces during normal operation. 
The difficulty arises when another die is placed in the machine at a 
different temperature state, or when an existing die becomes worn to the 
point when continued application of non-parallel clamping would be 
inadvisable. For purposes of rapid attainment of equal clamping on another 
die, or determination of the non-parallel condition of a new die, it would 
be desirable to achieve the condition mentioned earlier as "square". This 
"square" condition is attainable by use again of a squaring block, but the 
frequent installation of said squaring block is time consuming since it 
requires the removal of the die. 
Because of the difficult, time consuming, costly operation involved in 
squaring a machine with a squaring block, some operators have taken the 
position that the machine should never be adjusted and when metal leaks 
between the die halves, or the die cast article is imperfect, the die 
should be modified to correct the problem and imperfections. However, such 
practice has not been completely satisfactory because of the differences 
in the cross-sectional shapes of the dies which causes the dies when 
repaired in one area of the die to result in non-compliance in another 
area. Therefore, there has existed a long-felt need for a means to 
resquare die casting machines to their original-as-built square position. 
SUMMARY OF THE INVENTION 
In accordance with this invention, we provide a very simple means of 
resquaring a die casting machine. Our system is based upon the accurate 
assumption that all tie rods on a given machine have substantially the 
same, identical elasticity and, also, there is no permanent deformation in 
the tie bars caused by exerting different tension on each of the tie bars. 
In accordance with this invention, we initially determine the position of 
the adjustment nuts on the tie bars and the position of each nut relative 
to each other when the machine is originally squared with a squaring block 
as described above. We then provide means at each adjustment nut for 
detecting the position of each nut on its tie rod. In so determining the 
position of the adjustment nuts on the tie rods and the relative position 
of the nuts to each other, our system acts like a micrometer to detect and 
indicate any change in the position of each adjustment nut on its tie rod. 
Having determined the position of each adjustment nut relative to each 
other, we utilize the automatic tie bar adjustment system of U.S. Pat. RE 
No. 32,048 entitled TIE BAR ADJUSTMENT SYSTEM and issued on Dec. 17, 1985, 
to readjust each adjustment nut independently and separately until the 
relative positions of each of the adjustment nuts on their tie rod and to 
each other are reset to the original position of such adjustment nuts at 
the original squaring of the machine. 
In accordance with the broader aspects of this invention the detection of 
the position of each adjustment nut on its tie rod can be accomplished by 
an operator that sequentially adjusts each adjustment nut. However, in the 
preferred embodiment of this invention, we provide an automatic means 
including a logic circuit programmed for sequentially detecting when each 
of three tie bars is out of square relative to a reference bar, and 
thereafter sequentially adjusting each nut so as to return the platens to 
their original square position. In this automatic adjustment, the entire 
machine can be squared within five or ten minutes. 
With such a system, therefore, it is possible to automatically resquare a 
machine between casting cycles and thereby determine whether problems such 
as metal leaks between the die halves or casting imperfect articles are 
being caused by a bad or imperfect die, flash build-up, or an unsquare 
machine. Thus, our system can be utilized to insure uniform quality 
castings. It also lengthens the life of the machine which otherwise, to 
its detriment, might be utilized with faulty dies and also lengthens the 
life of dies by avoiding the application of large concentrated loads in 
order to detect non-parallel platens.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a die casting machine 1 is shown in pictorial form and 
includes a front stationary plate or platen 2, a rear, stationary plate 3 
and a movable or traveling plate or platen 4. The movable plate or platen 
4 is positioned between the front or rear plates and movable therebetween 
by a toggle mounted between the plates 3 and 4 and generally actuated by a 
hydraulic cylinder (not shown). On the rearward facing surface of the 
plate 2, there is attached one-half of a die 5 while the corresponding 
mating half of the die is mounted on the front surface of the movable 
platen 4. Plate 4 is slidably mounted on four tie bars 6, 7, 8 and 9 which 
are secured at one end to the front plate or platen 2 and at the opposite 
end to the rear plate 3 by means of their threaded ends which can be 
threaded sleeves and collars as specifically described in U.S. Pat. RE No. 
32,048 and disclosed in FIG. 3 as will be described hereinafter. It should 
be understood that the threaded tie bars can be integral threads cut into 
the ends of the tie bars or can be the threaded sleeves and collars as 
disclosed in FIG. 3. Associated with the tie bars 6, 7, 8 and 9 are the 
strain gauges 10, 11, 12 and 13 of a type such as that described in U.S. 
Pat. No. 4,466,477 and U.S. Pat. RE No. 32,048, the descriptions of which 
are incorporated in this application by reference since it is not 
considered essential to describe such strain gauges in detail because of 
the disclosure in such patents. 
As previously referred to, the die casting machine 1 also includes a 
hydraulic ram and a toggle linkage (not shown) coupled between the rear 
plate 3 and the movable platen 4 for advancing the movable platen into a 
locked-up casting position with the die closed and for retracting the 
movable platen 4 away from the stationary front platen 2 for opening the 
die to remove the cast part. The die casting machine 1 is of the general 
type as disclosed in U.S. Pat. No. 3,407,685, issued Oct. 29, 1968, U.S. 
Pat. No. 4,256,166, issued Mar. 17, 1981, and U.S. Pat. RE No. 32,048, 
issued Dec. 17, 1985, such patents all being assigned to the present 
assignee. U.S. Pat. RE No. 32,048, and the disclosure thereof is to be 
considered incorporated by reference into this patent because it discloses 
in greater detail the automatic tie bar adjustment means utilized by this 
invention. 
Mounted to the rear surface of rear plate 3 for rotation in a conventional 
fashion is the bull ring gear 14 having the peripheral teeth 15 engaged by 
the driver gear 16. The teeth 15 of the bull or ring gear 14 engage the 
longitudinally movable idler gears 20, 20a, 20b and 20c. As disclosed in 
FIG. 1, idler gears 20, 20a, 20b and 20c in turn selectively engage 
adjustment nuts or so-called tie bar nuts 30, 30a, 30b and 30c, which in 
turn engage the threaded ends associated with each of the tie bars 8, 9, 7 
and 6, respectively. Thus, when the ring or bull gear 14 is rotated by the 
drive gear 16, those tie bars having their adjustment nuts in engagement 
with an idler gear will have their tension adjusted. The tension 
adjustment of the tie bars is accomplished during the die open position of 
operation while the result of the adjustment is monitored during lock-up. 
Although the disclosure of U.S. Pat. RE No. 32,048 is incorporated by 
reference into this application, reference is made to FIGS. 2, 3, and 5 
for a brief description of the adjustment mechanisms for each tie bar of 
the die casting machine 1. In respect to these figures, it should be 
understood that the mechanism is identical for each of the four tie bars 
shown in FIG. 1. 
FIGS. 2 and 3 disclose the lower right (as seen in FIG. 1) tie bar 
adjustment mechanism for the tie bar 9. Tie bar 9 extends through an 
aperture 17 (FIG. 3) in the lower right hand corner of the rear plate 3. 
The tie bar 9 as disclosed includes the cylindrical sleeve 18 fitted over 
and retained on the end of the tie bar 9 by means of the retainer 36 held 
in place by the cap 38, all as disclosed in U.S. Pat. RE No. 32,048. 
Threaded on sleeve 18 is the adjustment nut 30 which has the external teeth 
31. As disclosed in FIG. 3, the adjustment nut 30 is retained on the rear 
plate 3 by means of the retainer member 21 which is secured to plate 3 by 
the bolts 22. Retainer member 21 includes an opening which exposes the 
teeth of the adjustment nut 30 and permits the idler gear 20 to engage the 
peripheral teeth 31 of the adjustment nut 30. This idler gear mechanism is 
shown in both FIGS. 2 and 3. FIG. 2 discloses the idler gear in solid 
lines engaging both the adjustment nut 30 and the bull ring 14 whereby 
rotation of the bull ring 14 rotates the idler gear 20 which in turn 
engages the teeth 31 on adjustment nut 30 for adjustment of the tie bar 
tension. FIG. 2 also discloses the idler gear in phantom lines disengaged 
from the bull gear 14 and the adjustment nut 30 although in order to 
maintain sync of the gear teeth the arrangement of the gears can be made 
to cause the idler gear to remain partially engaged with the bull gear but 
disengaged from the nut. This is achieved by the idler gear being mounted 
on a riser bracket 24 which in turn is attached to a coupler rod 25 
secured to the shaft 26 of the hydraulic cylinder 27. 
The stroke of cylinder 27 is such that when the shaft is fully extended, 
the idler gear is in engagement between both gear 14 and the adjustment 
nut 30 as seen in FIGS. 2 and 3. A pair of limit switches 28 and 29 
provide forward and rear position indication to a control circuit in 
response to the engagement of the limit switch actuator plate 34. 
Both FIGS. 2 and 3 disclose the means for rotating the bull ring gear 14, 
such means including the driver gear 16 coupled to the shaft 46 of a bull 
gear drive 19 which includes the gear reducer actuator 19b actuated by the 
hydraulic motor 19a. Motor 19a is reversible to cause rotation of shaft 46 
in a counterclockwise or clockwise direction as determined by solenoid 
valves not disclosed in FIGS. 2 and 3, but shown schematically in block 
form in FIG. 6 as solenoid valves 41 and 42. 
In order to control the bull gear so that as it is rotated it is rotated 
incremental distances, a means is provided for detecting the rotational 
position and controlling the same. This means includes a disc 44 mounted 
on the shaft 46 of the actuator or gear reducer 19. This disc is rotated 
along with the drive gear 16 by the gear reducer 19. The slotted disc 44 
includes a plurality of radially, inwardly extending angularly spaced 
slots 45 located around the entire periphery of the disc. On one side of 
the disc is a light source (not shown) provided to project a light through 
one slot as the disc is rotated. On the other side of the disc is the 
light sensor 47 (FIG. 2) positioned to detect the light projected through 
one of the slots 45 and generate a signal which is fed to the logic 
circuit 40 as will be described. The diameter of the drive gear 16 and the 
spacing of slots 45 are selected such that a signal is developed by sensor 
47 when the bull gear rotates an angular distance corresponding to one 
tooth. Accordingly the rotation of the bull gear is controlled to move in 
tooth-to-tooth increments. 
Because the description of the operation of the adjustment mechanism is 
clearly described in U.S. Pat. RE No. 32,048, it is not considered 
necessary to repeat the operation of the tie bar adjustment mechanism. It 
should be understood that as disclosed in said patent, the adjustment 
always takes place when the machine is not locked up, thereby relieving 
tension on the tie bars so that the threaded sleeve can be easily 
adjusted. 
In both the manual and automatic adjustments as described in U.S. Pat. RE 
No. 32,048, it should be understood that the adjustments are made in 
response to the tension on each of the tie bars, i.e., the tie bars are 
individually adjusted to maintain the tie bars within the prescribed 
tension limits programmed either manually or through a logic circuit. In 
either mode, the adjustment be it done manually or automatically does not 
take into account that the adjustment in the tie bars required to maintain 
the prescribed tension in each tie bar may be due to a worn or faulty die 
or to a flash build up in the die. The present invention, utilizing the 
mechanism as disclosed in U.S. Pat. RE No. 32,048, provides a means for 
resquaring the platens of the die casting machine without regard to 
whether the die is worn and faulty or whether flash is built up. 
In accordance with this invention, we provide a system schematically 
illustrated in FIG. 4. This system includes a detector means associated 
with each of the adjustment nuts 30, 30a, 30b, and 30c. This detector 
means includes limit switches LS1-A and LS1-B for adjustment nut 30, LS2-A 
and LS2-B for adjustment nut 30a, LS3-A and LS3-B for adjustment nut 30b, 
and LS4-A and LS4-B for adjustment nut 30c. Each pair of these limit 
switches is actuated by a half ring limit switch actuator 33, 33a, 33b, or 
33c provided for the adjustment nuts 30, 30a, 30b, and 30c, respectively. 
The actuators are mounted circumferentially on the adjustment nuts and 
cannot extend more than 180.degree. about the circumference of the 
adjustment nuts. The half ring limit switch actuators are all located 
radially toward the bull gear, i.e., adjacent the idler gears 20, 20a, 
20b, and 20c. 
In accordance with this system, when the die casting machine is originally 
squared by use of a squaring block as previously described, each of the 
half ring limit switch actuators 33, 33a, 33b and 33c are in the position 
radially toward the bull gear and actuating all of the limit switches 
LS1-A, LS1-B, LS2-A, LS2-B, etc. In this position, the limit switches for 
each associated adjustment nut are actuated simultaneously to designate 
the original squared position of the nut. Thus, so long as all of the 
limit switches are actuated the die casting machine is squared. However, 
if only one of the pair of limit switches is actuated, this indicates that 
the tie rod associated with such pair is out of square and specifically 
the switch which is not actuated would designate the direction the nut had 
to be turned to bring the tie bar back to the squared position. 
The structure for accomplishing the system of FIG. 4 is disclosed in FIGS. 
2, 3 and 5. Specifically, the half ring limit switch actuator 33 is 
mounted on the top peripheral surface 39 of the adjustment nut 30, it 
being important that the switch actuators are exactly positioned to 
actuate all the switches when the machine is square. Only then are the 
ring switch actuators secured in place on the adjustment nuts by means of 
the roll pins 35 (FIG. 5). It is also important that the limit switches 
such as LS1-A and LS1-B be exactly positioned at the very peak of the ramp 
37 as illustrated by FIG. 8. It should be understood that each of the 
switch actuators 33, 33a, 33b and 33c are mounted in similar fashion while 
the machine is square, the square of such machine being determined by 
inserting a squaring block between the two platens 2 and 4, actuating the 
movable platen 4 to lock position and then adjusting the nuts individually 
as previously disclosed until the strain in the tie bars is all identical 
at which time the machine is square, i.e., there is equal tonnage on all 
corners and the platens are parallel by virtue of the parallel faces of 
the squaring block. 
Having assembled the ring switch actuators 33, 33a, 33b and 33c and limit 
switches LS1-A and LS1-B etc. on their respective adjustment nuts 30, 30a, 
30b and 30c, after operating the machine it is simple to determine the 
squareness of the machine by checking each of the limit switches to 
determine if they are actuated or not. Such determination is accomplished 
by providing the indicator lights 51a, 51b, 52a, 52b, 53a, 53b, 54a and 
54b (FIG. 6), one for each of the limit switches. If all of the limit 
switches are actuated as determined by the indicator lights the machine is 
square. However, if any one limit switch is not actuated, as determined by 
an indicator light, the tie bar which is out of square can be easily 
spotted. To resquare such tie bar, all of the idler gears except for the 
one associated with the tie bar that is out of square, are disengaged from 
their associated tie bar adjustment nuts. The bull gear is then driven in 
the proper direction until both of the limit switches for the tie bar 
which was out of square are actuated indicating that such tie bar now is 
in the original squared position. This can be repeated for any of the tie 
bars which are indicated to be out of square. 
Although within the broadest aspect of this invention the die casting 
machine can be squared as above described by merely adjusting each of the 
tie bars which were indicated to be out of square, in the preferred 
embodiment of this invention the resquaring of the machine is accomplished 
by an automatic control system for adjusting the tie bars to the original 
squared position. This is done individually but in a programmed sequence 
so that the entire resquaring is accomplished automatically without any 
observance or manual adjustments or actuations by the operator except for 
initiating the programmed sequance. 
FIG. 6 discloses in block diagram form a control circuit the exact details 
of which are well within the purview of one skilled in the art, 
particularly when considering the disclosure of U.S. Pat. RE No. 32,048. 
The diagram of FIG. 6 discloses a logic circuit 40 into which is fed 
signals from the limit switches LS1-A, LS1-B, LS2-A, LS2-B, LS3-A, LS3-B, 
LS4-A and LS4-B. The logic circuit 40 responds to these various input 
signals to provide output control signals to the idler gear cylinder 
controllers 50, 50a, 50b, and 50c which in turn independently and 
separately control the hydraulic cylinders 27 for each of the idler gears 
20, 20a, 20b, and 20c, respectively. The logic circuit in responding to 
the signals from the limit switches also control the actuation of the bull 
gear drive 19. 
It should be understood that the logic circuit 40 controls the sequence in 
which each of the positions of the tie bar nuts are adjusted and checked. 
Such sequence programmed by the logic circuit is also important in the 
positioning of the nuts in their "home positions" in which the machine is 
squared. Such sequential positioning involves rotating nut 30 in a 
clockwise direction to its "home position" wherein LS1-A and LS1-B are 
both actuated and then sequentially checking and adjusting the positions 
of nuts 30a, 30b and 30c, respectively. As an example of such adjustments, 
reference is made to FIG. 4 which discloses that the ring actuator 33 is 
actuating switch LS1-B but not LS1-A. Thus, the logic circuit detecting 
this condition of limit switches LS1-A and LS1-B generates a signal to the 
clockwise solenoid valve 41 causing the bull gear drive to rotate drive 
gear 16 in a clockwise direction which in turn rotates ring gear 14 in a 
counterclockwise direction, idler gear 20 in a clockwise direction and tie 
bar nut 30 in a counterclockwise direction until the ring actuator 33 of 
the bar nut actuates both limit switches LS1-A and LS1-B. Upon such limit 
switches being both actuated, the logic circuit causes idler gear 
controller 50 to actuate hydraulic cylinder 27 to pull the idler gear 20 
out of engagement with the bull gear 14 and tie bar nut 30. 
The second sequential step produced by the logic circuit 40 is to check the 
position of nut 30b by detecting the actuation or nonactuation of limit 
switches LS2-A and LS2-B associated with tie bar nut 30a. As disclosed in 
FIG. 4, limit switch LS2-A is actuated but LS2-B is not actuated. Thus, 
the logic circuit causes the actuation of the counterclockwise solenoid 
valve 42 which causes counterclockwise rotation of drive gear 16 which 
through the ring gear 14 and idler gear 20a rotates the tie bar nut 30a in 
a clockwise direction until both limit switches LS2-B and LS2-A are 
actuated which determines the "home position" of nut 30b. At such time the 
logic circuit 40 causes idler gear cylinder controller 50a to actuate the 
hydraulic cylinder 27 associated with tie bar nut 30a to pull the idler 
gear 20a out of engagement with the tie bar nut 30a and ring gear 14. 
The third sequential step performed by the logic circuit 40 is to control 
the adjustment of the tie bar nut 30b in response to the actuation or 
deactuation of limit switches LS3-A and LS3-B. The logic circuit checks 
the orientation of tie bar nut 30b by responding to the signals from the 
limit switches LS3-A and LS3-B. If LS3-A is actuated and LS3-B is not, or 
vice versa, the logic circuit responds thereto by actuating either the 
counterclockwise solenoid valve 41 or the counterclockwise solenoid valve 
42 in the way as described in relation to the adjustment of the tie bar 
nuts 30 and 30a. This causes the bull gear drive 19 to rotate the drive 
gear 16 and the bull gear 14 in the proper direction causing both limit 
switches LS3-A and LS3-B to be simultaneously actuated by the ring 
actuator 33b. When these limit switches are simultaneously actuated the 
logic circuit signals to the idler gear cylinder controller 50b causing 
the hydraulic cylinder 27 associated with the idler gear 20b to pull the 
idler gear 20b out of engagement with the bull gear 14 and the tie bar nut 
30b. 
The fourth sequential operation performed by the logic circuit is the 
control of the bull gear drive in response to the actuation or deactuation 
of the limit switches LS4-A and LS4-B associated with the tie bar nut 30c. 
The signals generated by limit switches LS4-A and LS4-B, depending upon 
whether they are actuated or not, are fed to the logic circuit which 
causes actuation of either of the clockwise solenoid valve 41 or 
counterclockwise valve 42 which in turn controls the actuation of the bull 
gear drive that rotates the drive gear 16 which in turn rotates the bull 
gear drive in a manner as above described in relation to the tie bar nuts 
30, 30a and 30b. Upon all the limit switches LS4-A and LS4-B being 
actuated simultaneously, the logic circuit causes the idler gear cylinder 
controllers 50, 50a, and 50b to cause actuation of the hydraulic cylinders 
27 associated with the idler gears 20, 20a and 20b causing all of the 
idler gears to be reengaged with their respective tie bar nut and the bull 
gear. The tie bar nuts are now in the same relative orientation to the tie 
bar as when the machine was originally squared. Thus, if there is any 
indication of different strains in the tie bar, it is known that either 
the die is worn or faulty, flash is built up on the die or that there has 
been uneven wear of the toggle bushings. 
It should be understood that during each of the sequential steps described 
above the operation of the logic circuit is controlled by the photosensor 
47 to rotate the bull gear incremental distances corresponding to 
tooth-to-tooth increments all as described above. Further, it should be 
understood that the adjustment of the tie rods by the tie rod nuts is 
never more than 180.degree.. 
In accordance with this invention, the automatic square testing can be 
accomplished by providing visual indications from each of the indicator 
lights 51a, 51b, etc. for the limit switches LS1-A, LS1-B, etc., so that 
one can actually visualize whether all the switches are simultaneously 
actuated. By means of such visual indicator lights the system can be 
tested by a procedure in which with all of the switches actuated, the bull 
gear drive 19 is slowly adjusted until the photosensor 47 detects a light 
through one of the slots 46 as indicated by the indicator light 48 (FIG. 
6) provided for that purpose. Bull gear 14 is then adjusted one tooth, as 
determined by the photosensor 47, in a direction backing off from the die. 
If the machine is square the LS1-A, LS2-A, LS3-A and LS4-A limit switches 
will all be on as indicated by the indicator lights 51a, 52a, 53a, and 54a 
while all of the limit switches LS1-B, LS2-B, LS3-B, and LS4-B will all be 
deactuated as determined by the indicator lights 51b, 52b, 53b, and 54b. 
The next test in the autosquare testing is to rotate the bull gear in the 
opposite direction from the first direction in which it was rotated, the 
rotation being two teeth as determined by the photosensor 47 and its 
indicator light 48. In this position, the LS1-B, LS2-B, LS3-B, and LS4-B 
switches should be actuated while LS1-A, LS2-A, LS3-A, and LS4-A switches 
are deactuated. The next step is to resquare the machine by reactivating 
the logic circuit which causes the machine to be automatically squared in 
which all of the indicator lights 51a, 51b, 52a, 52b, 53a, 53b, 54a, and 
54b are all on indicating that all of the limit switches are being 
actuated and thereby the tie bar nuts have the same relative orientation 
to the tie bars as when the machine was originally squared. 
The automatic squaring can also be tested further by unbalancing the tie 
bar nut adjustments to render the machine out of square while the logic 
circuit is inactivated. Then the logic circuit is reactivated causing the 
logic circuit to perform in sequence the control of the operation of the 
bull gear drive 19 and the idler gear hydraulic cylinders 27 for 
resquaring tie rods 9, 7, 6 and 8 in a manner as above described until the 
machine is resquared. 
Although the preferred embodiment of the present invention discloses a 
fully automatic system for resquaring a die casting machine, it should be 
understood that within the broadest aspect of this invention, it 
encompasses the use of semi-automatic or manual modes of operation using 
the adjustment system of the present system as above described. The 
semi-automatic mode of operation can be accomplished by providing, for 
example, manual actuated switches to provide input signals to the solenoid 
valves for the bull gear drive and to the idler gear cylinder controllers 
such that when the limit switches for the tie bar nuts indicate a tie bar 
needs adjustment, the operator can disengage all of the idler gears except 
the one associated with the tie bar nut that needs adjustment. These and 
various modifications of the preferred embodiment of the invention 
described and disclosed herein will become apparent to those skilled in 
the art and all fall within the spirit and scope of the invention as 
defined by the appended claims.