US2953953A - Thread rolling apparatus and control means therefor - Google Patents

Description

E. F. w. MOELTZNER ETAL 2,953,953

3 Sheets-Sheet 1 mw 5 .ww mm 9. 8. 6 mm 1 Sept. 27, 1960 THREAD ROLLING APPARATUS AND CONTROL MEANS THEREFOR Filed Aug. 4, 1953 INVENTORS ATTORNEY/7 p 1960 E. F. w. MOELTZNER EIAL 2,953,953

THREAD ROLLING APPARATUS AND CONTROL MEANS THEREFOR Mn; a mm. n N 0 S 1 "I s L t s y W J W W 3 1 v 5 m g Y B 3 5 9 1 4 L. H A d e l 1 F ATTORNEKF Sept. 27, 1960 E. F. w. MOELTZNER ErAL 2,953,953

THREAD ROLLING APPARATUS AND CONTROL MEANS THEREFOR Filed Aug. 4, 1953 3 Sheets-Sha et 3 INVENTORS [RA/6r FTP/r2 Mann Minn/u ATTORNEKT THREAD ROLLING APPARATUS AND CONTROL MEANS THEREFOR iaiented se i. 27, 19

after only half :a revolution of the threading rolls, for example. The rolling path of the threading rolls can be changed merely by changing the speed of the trans mission,' so that, for example, a work piece can be 5 finish-rolled in 5,43, 4, 1.2 etc. revolutions whereupon Ernst Fritz Wilhelm Moeltzner, Berlin-Charlottenburg,

and Johann Hiibl, Berlin-Halensee, Germany, assignors, by mesne assignments, to Landis Machine Company, 'Waynesboro, Pa., a corporation of Pennsylvania Filed Aug. 4, 1953, Ser. No. 372,284

Claims. .(Cl. 80-6) The invention concerns a controlmeans for hydraulically operated thread rolling machines with automatic approach and separation of the threading rolls and more particularly to improvements in apparatus of the type disclosed in copending'applicationserial No. 365,048 filed June 30, 1953 for Rolling Machines and Control Means Therefor now Patent No. 2,873,634 issued February 17, 1959. In accordance with the aforesaid application Serial No. 365,048 it has been proposed to reconnect the hydraulic medium, after it has been discon nected by a timer mechanism, by means of a controllable timing piston, which actuates, after a predetermined time,

a starting switch for the electrical operation of the valve It has become apparent that it is highly advantageous v V to be able readily to adapt the automatic control of thread rolling machines to specific requirements which arise When'rolling various work pieces. By adjusting the timer mechanism and the rest interval timing piston, this is possible only imperfectly and with a great deal of bother. Thus, for example, it is advantageous to accomplish rapidly the idle travel of the threading roll, which is dependent upon the distance between the rolls after they have been separated, in order to reduce the idle time for feeding large work pieces. Again, small work pieces, of which several, for example, are rolled in one revolution of the rolls, require a rapid reciprocation of the roll. Furthermore, it is important to the rolling process that the rolling travel necessary to completely roll the profile to be produced be strictly adhered to.

Heretofore, the timer mechanism was used tto disconnect the rolling pressure and this timer operated to disconnect the rolling pressure after the expiration of a predetermined time. In the case of short rolling times which occupy a fraction of one rotation of the threading rolls, the timer mechanism no longer operates with the required accuracy, since it is not practical to set a rolling time of less than two seconds. Therefore, new ways must be found to enable the most diverse rolling travels to be infinitely adjusted. These requirements are fulfilled by the invention, by reason of the fact that one or more valves, installed in the hydraulic circuit of the cylinder for operating the threading rolls, can be operated by the threading roll drive through a variable speed transmission and the length of the rolling path on cylindrical threading rolls can be infinitely adjusted by changing the threading rolls areseparated, the new work piece is transferred and the threading rolls approach each other for the new rolling operation. However, the transmission'canbe-adjusted'so'that it actuates two,'three or more reciprocations of the threading rolls in each revolution of the rolls, for example, when, respectively, two, three or more work pieces, for example screws with an M2'or -M1 thread, are to be finish-rolled per revolution of the threading rolls. The speed ratio set at the transmission for the speed of the threading rolls controls the length of the rolling path. This ratio does not change when the rotational speed of the threading rolls is changed so that it is not necessary, in such case, to readjust the transmission. Furthermore, the advantage is obtained that special threading rolls, employed heretofore, having recesses for transferring work pieces and having spirally rising surfaces, are superfluous and are replaced by standard cylindrical threading rolls. Consequently the adaptability to various rolling processes no longer depends on the particular construction of these special threading rolls, which are different for each purpose, but on the easily operated control means for the automatic reciprocation of cylindrical rolls.

An advantageous embodiment is one in which two valves are operated in synchronism by the transmission; one of the valves controls the rapid infeed of the threading rolls and the other controls the reciprocation of the rolls'without rapid infeed. Thereby the advantage is obtained that the threading roll can either'be advanced at a rapid rate to the work piece between the rolls, then rolling the work piece or can be controlled to reciprocate, so that the previous idle time islowered and the output of the machine is considerably increased. I a

It is advantageous if one of the valve spools, which is .installed in the hydraulic pressure line, opens, in'its original position, the hydraulic fluid line which leads to theloperating cylinder and which is metered by a feed regulating .valve and said valve spool, when displaced, quickly opens the 'unmetered full cross-sectional area of the pressure line for the rapid in feed and then closes it again, reconnecting the metered line. The other valve, installed in the discharge line, is closed andfat the end of the rolling operation for the'first time opens the full cross-sectional area of the discharge line arid then closes it again. The reciprocation of the threading roll may be adapted to any rolling process by the syn chronized cooperation'of both valves. Furthermore, the advantage is obtained that the thread rolling machine opj erates smoothly 'in spite of the rapid infeed, sincethe beginning of the approach movement of the threading roll is effected by an initially metered hydraulic circuit and the full cross-sectional area of the hydraulic fluid'line is effective only after the start of the approach movement of'the roll.

- An especially suitable embodiment of the-control means, for thread rolling machines is one in which the transmission operates two valve spools with cams mounted at their ends, which are engaged by the push rods of the spring pressed valve spools. But it is also possible to construct both valve spools as rotary valves and to drive them directly -from1tl1e transmission; i

A practical construction is one inwhich ;a stop. cock is installed in the hydraulic line leading to. ,the--l '-alve for the rapidinfeed control and ahead pftthe,junctiop of the line leadingto the feed regulatingvalve, ,a seeppd stop cock is installed in the line leading from the said valve spool to the operating cylinders and a third stop cock is installed in the discharge line ahead of the other valve spool. The arrangement of these cocks makes it possible to disconnect the valve controlling the rapid infeed, simply by closing the cocks and to operate merely with the valve disposed in the discharge line, which then controls the rapid reciprocation of the threading rolls. Furthermore, a comparatively simple system of pressure and discharge lines is possible, so that the control means can be applied as an auxiliary control means to the standard machine control which is by means of the main control box.

For this purpose it is to advantage that the discharge line from the operating cylinder consists of two lines, one of which leads through the main control valve and the other through one or both valves, and that the hydraulic line has a by-pass line ahead of the stop cock and leading to the operating cylinders, so that the hydraulic circuit of the control valves lies parallel to the circuit of the main control valve and the main or secondary control valves may be connected as desired. The advantage is thereby obtained that the machine can be operated either by the standard control, supplied by the main control valve with the timer mechanism and rest interval timing piston or by the auxiliary control.

It is advantageous if the main control valve spool has means, operated by a hand lever, for locking it in the position which it occupies when the electromagnet for operating it is energized; thus has the advantage that the electromagnet is not energized while the auxiliary control is being used.

Obviously, changes can be made in the arrangement of lines, control valves and cocks; thus for example both control valves can be installed in the discharge line.

The subject matter of the invention is shown in several exemplary embodiments in the drawings, in which Figure 1 shows an overall control plan,

Figures 2 and 3 show embodiments of the control means,

Figure 2a is a schematic showing of the electrical circuit of the apparatus of Figure 2,

Figures 4 and 5 are transverse sections taken along line 4-4 and 55, respectively, of Figure 3; and

Figure 6 is a view similar to Figures 4 and 5 of a modified valve.

In Fig. 1, 1 and 2 denote the threading rolls, of which the roll 1 is stationarily journalled and the roll 2 is journalled on the slide 3, which is movable by the operating pistons 4 in opposition to the retracting spring 5. The cylinder block for both pistons 4 is designated by 6. The work rest 7 with the work piece 8 to be rolled is disposed between the threading rolls. The threading rolls are driven by the driving motor 15 through the gear box 14, shaft 13, worms 11, worm wheels 12 and drive shafts 9 and 10.

The shaft 16 branches off from the transmission 14, runs at the same rotational speed as the operating shafts 9, and is connected to the variable speed transmission 17 which is variable as infinitely as possible by means of the handle 18. This transmission has two drive shafts 19 and 20 which operate the control valves 21 and 22, with the aid of the disc cams 23 and 24. The control valves are installed in the hydraulic circuit, not shown in this diagram, of the operating pistons 4 and control the full or metered flow of hydraulic fluid to the pistons and the discharge therefrom. The movement of the threading rolls 1 and 2 toward or away from each other and the threading path traveled through on these cylindrical threading rolls is therefore adjustable to the speed of the threading rolls, depending upon the rotational speed ratio set at the transmission 17.

One embodiment of this control is shown in Fig. 2. The two operating cylinders for the movable slide, not shown, which carries a threading roll, movable toward the other threading roll, areas in Fig. ldesignated by 6 and the operating pistons by 4. The main control valve spool 25 is installed in the pressure line 27 from the pump 26. The feed regulating valve 28 is located in the branch line 29 of the line 27. The branch line 29 leads to the control valve spool 30 for the rapid infeed. The second feed regulating valve 32 is installed in the branch line 31. Both lines 29 and 31 lead through the valve spool 30 and in such a way that, in the end position of the spool, the metered line 31 is connected to through-flow while the line 29 is closed. Beyond the valve spool 30, the lines 29 and 31 join line 33 which empties into the cylinder block 6 and which contains the cock 34. .The cock 35 is installed in line 29 ahead of the valve spool 30 and ahead of this cock the line 36 branches oil and likewise leads to the cylinder block 6. Two drain lines 37 and 38 lead from the spool of valve 22 to the reservoir 39. The spring 40 urges the valve spool 30 with the push rod 41 against the cam 24 which is driven by the variable speed transmission 17. The transmission 17 is maintained in driving connection with the driving motor 15 (Fig. 1) for rotating the threading rolls.

The pressure regulating valve 43 is associated with the main valve spool 25 and is installed in the branch line 44 of pressure line 27 which is also closed at the relief valve 45. The pressure regulating valve 43 and relief valve 45 have discharge lines 46 and 47 which empty into the reservoir 39. A resetting spring 48 normally urges the valve 25 to the left as viewed in Figure l and an electromagnet 49, when energized, opposes the spring to move the valve to the position shown in Figure 2. By means of the manual control handle 50, which has the latch means 51, the main valve spool 25 may be moved into the position shown and locked therein when it is to be disconnected. The body of the main valve spool 25 has, at both ends, drain lines 52 and 53, as well as the discharge line 54, which is controlled by the main valve spool 25. The discharge line 54 is closed when the spool is actuated by the electromagnet 49 or latched. Therefore the line 54, which is connected to the cylinder 6, is under pressure. In the branch line 55 are installed the pressure regulating valve 56 and the timer piston 57 for regulating the rest interval, which closes the contacts 58 and 59 when the piston 57 moves back under pressure of the spring 60 when the lines 54 and 54' are connected to open discharge. The contacts 58 and 59 close the circuit for the electromagnet 49, in which circuit the switch 61 is disposed. Switch 61, when opened, breaks the circuit through contacts 58 and 59. The switch 61 is closed when the rest interval regulator is in operation. This is indicated by the control lamp 62. The drain line 63 is connected to the cylinder of the timer piston 57. The cock 65, which serves to bleed the air, is installed in the line 64 which branches oil from the line 54'. The line 64 leads to the reservoir 39.

The cock 67 and the valve 21 having the valve spool 69 for controlling the rapid reciprocation of the threading rolls are installed in the discharge line 66 leading from the cylinder 6. The re-setting spring is denoted by 70. This spring urges the push rod 71 of the valve spool against the cam 23 which is driven by the transmission 17 and which is arranged in fixed phase with the cam 24. In the position shown the discharge line 66 is opened by the valve spool 69. The valve 21 is provided with the drain line 73. The timer device 74 operates to stop the rolling operation by de-energizing the solenoid 49.

The timer assembly 74 which may be of conventional construction includes a motor driven timer element effective to close the circuit to the opening solenoid 92 of normally closed switch 94 a predetermined time after the timer power circuit including power lines 96 and 97; is energized by closing of the normally open pressure operated switch 98. The switch 98, which is normally open, is closed by the application of pressure through conduit 99 connected to cylinders 6. The switch 94 is positioned in a simple holding circuit in parallel with the rest interval contacts 58 and '59, the holding circuit also including a normally open switch 100 closed by a solenoid 102, the switch 139 being in series with the by the latch 51. -rneans is disconnected and'the auxiliary controllrn s aaaaeaa In this manner the normal control for'automatic reciprocation is connected.

the line 29 leads directly to the cylinder block 6. The

rotary valves .75 and 76, which correspond to the valve Spools '69 and 30, are installed in'the discharge line 66. The rotary valves 75 and 76 are driven via the transmission 17 as shown in 'Fig. 1. The rotary valve 75 is installed in the branch line 66a and the rotary valve 76 in the branch line 66b. The cocks 77 and 78 are disposed in branch line 66a before and behind therotary valve 75 and the cocks 79 and 36 are disposed in branch line 66b before and behind the rotary valve 76. 7 The valve 75 serves to cause rapid reciprocation of the threading'rolls and has the recess .81, as is evident from Fig. '4, which shows a cross section through valve 75 along line 44. The cross section through the valve 76 along line 5-5 is shown in Figs. 5 and 6 which illus- 'trate exemplary embodiments of this rotary valve. "The valve '75 has on its circumference the shallow, arcuately rising recess 82, which extends over the arc x. The adjacent cylindrical portion 83 extends over the arc y. The arcuately rising recess 84, which extends over the are z, adjoins the cylindrical portion. In the other modification .of rotary valve 76a shown in Fig. 6, the recess 85, which permits the free discharge, is provided in addition to the recesses 82 and84. V

The manner of operation of the embodiment illustrated in Figure Z'Wlth the auxiliary control apparatus disconnected by disposing the valves 34, 35, and '67, in the dotted line positions of Figure 2 will now be described. Assuming that the pump 26 is in' operation, that the drive motor is energized to. rotate the rolls and that the switch 61 is open, rolls will be fully retracted because of the connection of discharge lines 54 and 54'. When switch 61 is closed, the solenoid 49 will be energiz ed by reason of the fact that switch contacts 58 and 59 are also connected thus moving the valve to the position shown in Figure 2 closing the discharge line thereby establishing pressure in cylinders 6. When switch 61 is closed solenoid 102 will be energized thus closing the switch100. As soon as rolling pressure is established the contacts 58 and .59 will be opened and the switch 98 will be closed energizing the timer mechanism 90. After a pre-set time interval the timer mechanism 90 will energize the solenoid 92, thereby opening the switch 94 to de-energize 49 and connect the discharge lines 54 and 54' and permit the retraction of the rolls. This action also opens switches 98 and 190 and solenoid 49 will remain de-energized until the switch contacts 58 and 59 are again connected after the interval established by the setting of regulating valve 56. During the rolling action the speed at which the roll 2 is advanced toward the roll 1 is determined by the setting of the feed regulating valve 28.

To connect the auxiliary control means, the cocks 34, and 67 are moved to the positions I shown in full lines. Furthermore, the feed regulating valve 28 at the main control panel is opened fully, so that regulation of the feed is now effected by the second feed regulating valve 32. Also the main valve spool 25 is moved by the handle into the position shown while the electromagnet 49 is deenergized; it is locked in this position \Vhen large work pieces are being rolled, .therapid ,infeed of threading rolls 1 and 2 ,is effected by the valve 'The valve spool 69 has opened the discharge line 66 fully, so that the hydraulic fluidflows out of the cylinder .6. After the resultant return movement the valve spool 69 is moved by the rotating cam 23 into the dotted-line position, in which the discharge line 66 is closed. The valve spool 30 is still in the full-line position. From this moment on, the hydraulic fluid delivered by the pump 26 reaches the cylinder 6 through the fully opened feed regulating valve 28, line 29, the line 31 metered by the second feed regulating valve 32, the valve spool 30 and line 33, so that the slide 3 of the threading rolls '1 and 2 begins its infeed movement. In' the next instant the rotating cam 24 moves the valve spool 30 into the dottedline position in which the unmetered line 29 is opened so that the full volume of oil passes through line 33 to the operating cylinder. The-rapid infeed'takes place and is maintained until the threading roll 2 touches the work piece 8. At this instant the push rod 41 of the valve spool runs off of the 'cam 24 so that the valve spool is again disposed in the full-line position. The line is 'agairi'close d and the-feed of'the threading roll is etfected via the metered line 31 in accordance with the amount of metering set at the feed regulating val-ve 3'2. After the rolls 1 and 2 have completed -a pre-determ-ined number of revolutions, the valve spool 69 again opens the discharge line and the process repeats. During the separating movement of the threading rolls, the finishrolled work piece is carried away and a work piece to be rolled is fed by means of known automatically operating transfer mechanisms. I

To connect the circuit for rapid reciprocating movement of the threading rolls the cocks 34 and 35 are placed in the dotted-line positions II. The cock 67 remains in position I. Thereby the valve spool 30 for the rapid infeed is disconnected and only the valve spool 69 operates. The main valve spool 25 is in the locked position. The feed regulating valve 28 at the main valve spool is adjusted to the amount of metering desired.

The hydraulic fluid delivered by the pump 26 passes, through the feed regulating valve 28, line 29, line 36 and the cock 35 which is open to this line to the operating cylinder 6. With the discharge line 66 closed, the pressure builds up and rolling of the work piece is effected. But if the discharge line 66 is opened by the cam 23 being in the appropriate position, the hydraulic fluid flows freely out of the operating cylinder 6 through the discharge line 66. Thereupon the process repeats. the speed of the cam 72 may be regulated by the transmission 17, relative to the speed of the threading rolls 1 and 2, the reciprocating movement of the threading rolls and therewith the rolling travel may be altered as desired.

The manner of operation of the embodiment with rotary valves shown in Figs. 3 through 6 is the same in principle as that of Fig. 2. The difference is merely that the cams 23 and 24 are eliminated, sothat the rotary valves 75 and 76 are driven directly from the transmis-' sion and further that both rotary valves are installed in the discharge line. It is possible for both rotary valves to cooperate, as is the case in Fig. 2. In this case the valve 76 controls the smooth start of the rapid infeed by the recess 82, the rapid infeed itself by the circumferential portion 83, the start of the feeding movement by the recess '84 and the remaining portion of the rotary valve circumference, while the discharge is effected by the rotary valve 75 and its recess 81. For this pur;

Since,

pose the rotary valves 75 and 76 must operate in synchronism, as is also the case in the embodiment of Fig. 2.

When the cocks 79 and 80 are closed, the rotary valve 76 for the rapid infeed is disconnected and the valve 75 operates alone to control the rapid oscillation of the slide 3 of the threading roll 2.

However, it is also possible to effect free discharge at the valve 76 by the recess 85, so that, in this case, this valve controls all movements of the threading rolls. In this case the cocks 77 and 78 are closed.

When all cocks 77 through 80 are closed, the thread rolling machine operates only with the already discussed main control means and without the auxiliary control.

However, the auxiliary control can also operate as the main control when it is a question of a thread rolling machine for fully automatic operation. In this case the previous main control box with timer mechanism and rest interval timing piston is eliminated and instead of it, the rolling pressure regulating valve 43, relief valve 45 and the bleeder cock 65 are admitted into the control system.

We claim:

1. In a roll forming apparatus, a pair of rolls, means mounting one of said rolls for movement toward and away from the other of said rolls, means for rotating said rolls, a fluid pressure piston for moving said one of said rolls, pressure and exhaust conduits connected to said piston, a pluralityof valves arranged in parallel in said exhaust conduit, separate operators for each of said valves, and means mechanically connecting the means for rotating said rolls and each of said valve operators for actuating each of said valve operators in timed relation with the rotation of said rolls.

2. In a roll forming apparatus, a pair of rolls, means mounting one of said rolls for movement toward and away from the other of said rolls, means for rotating said rolls, a fluid piston for moving said one of said rolls, pressure and exhaust conduits connected to said piston, valves in each of said conduits, said valves having spools provided with cam followers, cam means for engaging said cam followers to move said valve spools, and a variable speed drive transmission drivingly connecting said cams to said means for rotating said rolls for operating said cams and said valves in timed relation with the rotation of said rolls.

3. In a-roll forming apparatus, a pair of rolls, means mounting one of said rolls for movement toward and away from the other of said rolls, means for rotating said rolls, a fluid piston for moving said one of said rolls, pressure and exhaust conduits connected to said piston, a valve in said pressure conduit having at least two parallel fluid passages, control means for selectively closing one of said passages to permit the supply of fluid to said piston at a relatively reduced rate, means to operate said control means in timed relation with the rotation of said rolls, a by-pass circuit in said pressure conduit across said valve adapted to permit flow of fluid to said piston at a predetermined rate, and valve means for selectively directing fluid to said piston through said by-pass circuit or through said valve.

4. In a roll forming apparatus, a pair of forming rolls, means mounting one of said rolls for movement toward and away from the other of said rolls, means for rotating said rolls, a fluid piston for moving said one of said rolls toward and away from the other of said rolls, pressure and exhaust conduits connected to said piston, means resiliently urging said one of said rolls away from said other of said rolls, valve means in said conduits having first, second and third relative operating positions effective, respectively, to move said one roll toward said other roll at a first rate, to move said one roll toward said other roll at a second lower rate and to permit the retraction of said roll under the influence of said resilient means, and a mechanical drive connection be tween said means for rotating said rolls and said valve means for moving said valves to said first, second and third relative operating in timed relation with the rotation of said rolls.

5. The combination according to claim 4 wherein said valve means is provided with cam followers and said last mentioned mechanical drive connection includes cams for engaging said cam followers and a variable speed drive transmission drivingly connecting said cams to said means for rotating said rolls.

6. The combination according to claim 4 wherein said valve means includes rotary valves and said mechanical drive connection includes a variable speed drive transmission drivingly connecting said rotary valves to said means for rotating said rolls.

7. In a roll forming apparatus, a pair of forming rolls, means mounting one of said rolls for movement toward and away from the other of said rolls, means for rotating said rolls, a fluid pressure piston for moving said one of said rolls toward and away from the other of said rolls, pressure and exhaust conduits connected to said piston, a pair of rotary valves arranged in parallel in said exhaust conduit, and a variable speed drive transmission drivingly connecting said rotary valves to the means for rotating said rolls for operating said valves in timed relation wtih the rotation of said rolls.

8. -In roll forming apparatus, a pair of rolls, means mounting one of said rolls for movement toward and away from the other of said rolls, means for rotating said rolls, a fluid piston for moving one of said rolls, pressure and exhaust conduits connected to said piston, valve means in one of said conduits having at least two fluid passages, means for selectively closing one of said passages to reduce the rate of flow of fluid through said one conduit, additional valve means in the other conduit, and means mechanically driven by said means for rotating said rolls for actuating said valves in timed relation with the rotation of said rolls.

9. In a roll forming apparatus, a pair of rolls, means mounting one of said rolls for movement toward and away from the other of said rolls, means for rotating said rolls, a fluid pressure piston for moving said one of said rolls, pressure and exhaust conduits connected to said piston, a valve in at least one of said conduits, an operator for said valve, valve control means operatively associated with said operator, and means drivingly connecting said means for rotating said rolls to said valve control means adapted to operate said valve in synchronous relation with the rotation of said rolls.

10. In a roll forming apparatus, a pair of rolls, means mounting one of said rolls for movement toward and away from the other of said rolls, means for rotating said rolls, a fluid pressure piston for moving said one of said rolls, pressure and exhaust conduits connected to said piston, a valve in each of said conduits for controlling the flow of fluid therethrough, a separate operator for each of said valves, valve control means operatively associated with each of said valve operators, and means drivingly connecting said means for rotating said rolls to said valve control means adapted to operate said valves in synchronous relation with the rotation of said rolls.

References Cited in the file of this patent UNITED STATES PATENTS 1,764,099 Galloway June 17, 1930 1,780,471 Galloway Nov. 4, 1930 1,920,596 Schafer Aug. 1, 1933 2,257,253 Wemhoner Sept. 30, 1941 2,624,218 Flanders et al. Jan. 6, 1953 FOREIGN PATENTS 254,315 Switzerland Apr. 30, 1948 256,890 Switzerland Sept. 15, 1948 235,330 Germany Apr. 3, 1945

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