US3335590A

US3335590A - Accurate control system for axial load bulge forming

Info

Publication number: US3335590A
Application number: US388201A
Authority: US
Inventors: Kenneth E Early
Original assignee: Boeing Co
Current assignee: Boeing Co
Priority date: 1964-08-07
Filing date: 1964-08-07
Publication date: 1967-08-15
Anticipated expiration: 1984-08-15

Description

Aug. 15, 1967 K. E. EARLY 3,335,590 ACCURATE CONTROL SYSTEM FOR AXIAL LOAD BULJGE FORMING 2 Sheets-Sheet 1 Filed Aug. 7, 1964 SEEN l .1 J m INVENTOR. Kf/Y/YET/l E. 54152) Aug. 15, 1967 WATER V SUPPD V REL REL 50 $01. 56 T I,

CAM T $1 4.

K. E. EARLY ACCURATE CONTROL SYSTEM FOR AXIAL LOAD BULGE FORMING Filed Aug. 7, 1964 2 Sheets-Sheet 2 Ly ELECTRICAL VALVE SOURCE 70 SOL I -34 42 I 74 OIL sum) 44 United States Patent 3,335,590 ACCURATE CONTROL SYSTEM FOR AXIAL LOAD BULGE FORMING Kenneth E. Early, Seattle, Wasl1., assignor to The Boeing Company, Seattle, Wasln, a corporation of Delaware Filed Aug. 7, 1964, Ser. No. 388,201 3 Claims. (Cl. 72-58) ABSTRACT OF THE DISCLOSURE The invention is directed to axial load bulge forming apparatus which is controlled by a system comprising (i) a segmented split die, (ii) a compression system to close .This invention relates to axial load bulge forming apparatus, but more particularly to a control system for programming the forming sequence of tube blanks into complex shaped parts, having various diameters and radii along its length, by liquid volume control.

In the prior art the forming of tube blanks into complex shaped parts having a variety of diameters and radii was based on a system that was pressure oriented. In order to form a part the pressure necessary to form the part into its desired shape was calculated and a certain amount of pressure was' determined. However, because of the variation in wall thickness of a tube blank and the difference in temperate strength along the length of the tube blank the parts thus formed in accordance to this system were all different and needed very often additional and special treatments. For example: some parts needed .tobe anodized and others had a larger or,smaller diameter and thus had to be rejected. It was therefore obvious that each tube blank could not be treated with the same pressure as was calculated and that for each tube blank a different pressure was needed in order to form equal shaped-parts. Thus the inadequacy was traced to minute variations in gage thickness, heat treat conditions and tube geometry which are unavoidable under normal production conditions. Another technique used in the, prior art for forming of tubes and tube fittings, which involved small radius bends and a large degree of diametrical expansion, comprised the use of internal rubber pressure to bulge form the part to the die configuration. A second used a rigid die arrangement and both techniques required the .use of extremely high forming pressures. Also such internal pressures tend to lock partially formed sections of the tube to the dies flat surfaces. This means, in the case of the first technique (simple bulge forming), that the material must be stretched both circumferentially and axially to form to the die configuration. Such stretching, together with the high pressure exerted, resulted in a very high incidence of part fracture. In the second case the combination of bulge forming and end loads, the end load pushed the material intothe die cavity, but the internal pressure forced the material against the die sun I faces. This often resulted in severe galling of the material, which is a basis for rejection of the finished part. With either of these techniques a rejection rate of up to 60% has. been experienced.

In short, the prior art maintains a forming procedure which depends on pressure oriented systems which were 3,335,590 Patented Aug. 15, 1967 found to be unreliable for producing parts of a similar shape and volume. The shortcomings of pressure control are even more evident when forming long non-symmetrical parts. For example, one of the formulas used to calculate the pressure required to yield (bulge) a tube is shown below:

S=yield strength of the tube material in p.s.i. W=tube wall thickness.

R==inside radius of the tube.

P=bulge pressure in p.s.i.

tubular parts by axial load bulge forming apparatus having an automatic regulated forming sequence.

It is still another object of the present invention to form parts by an axial load bulge forming apparatus having a volume control circuit which makes it possible to finish form a tube blank in one operation during which varia tion in tube condition and geometry are automatically compensated for.

Furthermore, this invention provides other objects, features, and advantages which will become fully apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate and clarify the preferred embodiment of this apparatus, in which:

FIGURE 1, illustrates a cross section of a segmented d ie having a tube blank positioned therein.

FIGURE 2, illustrates the same segmented die as shown in FIGURE 1 with the exception that the tube blank has been partly deformed by the internal bulging pressure and the die parts have moved closer together by a hydraulic force thus providing an axial load on the tube blank.

FIGURE 3, illustrates the final axial load bulging operation accomplished in the die and the finished part enclosed therein.

FIGURE 4, shows a schematic diagram of the control system for actual load bulge forming including the die, hydraulic pressure means, liquid supply pressure means with liquid volume control and an electrical balancing and switching means.

controlled by a system comprising (a) a split die having segments, (b) a compression system to close to die thus creating axial load on the part in the die, (c) a liquid .volume control system to bulge the part in the segmented split die and (d) a balance system to coordinate and regulate the axial load pressure and liquid volume bulging pressure with one another.

Referring now to the drawings wherein like reference characters designate corresponding parts throughout FIG- .URES. 1 through 5, there is shown in FIGURE 1, a split die 2, comprising. several segments 4, 6, and 8, positioned between its stationary top section 10 and its movable bottom section 12, in an extended relationship with one another and with a work piece or tube blank 14 positioned therein. The end portions of the tube blank 14 are resting against the movable bottom section 12 and the stationary top section and it is assumed that this enclosed position of the tube blank 14 and the top and bottom sections 10 and 12 should be within :.010 inch, which would be the particular position of starting the axial load bulge forming. A pressure line 16 is connected in a liquid tight relationship with the movable bottom section 12 for supplying liquid into the tube blank 14. A bleed line 18 is connected in a fluid tight relationship to the stationary top section 10 of the bleed off air.

In FIGURE 2, the split die 2 has changed its shape, the movable bottom section 12 has moved upwards and thus has compressed the tube blank 14 while at the same time the liquid which was fed through pressure line 16 into the tube blank 14, has bulged the tube blank 14 into a shape which starts to conform to the desired inside configuration of the segments 4, 6, and 8. The segments 4, 6, and 8 have accordingly moved and positioned themselves by the bulging action of tube blank 14 into its correct position.

FIGURE 3, shows the final stage of the axial load bulge forming and segments 4, 6, and 8 of the split die 2 which are disposed between the movable section 12 and the stationary top section 10, and the tube blank 14 has been formed into the shape and length of the complex shaped part as was required. The closing of the die 2, including segments 4, 6, and 8, the top section 10, the movable bottom section 12 and the amount of liquid fed into the tube blank 14 is regulated and controlled by an accurate control system.

In FIGURE 4, a schematic diagram illustrates the accurate control system for axial load bulge forming wherein volume control of the liquid for filling of the tube blank 14 and the closure of the die 2 are coordinated in an automatic controlled sequence. In general, hydraulic means 30 are shown to be connected to the split die 2 for creating an axial load against the tube blank 14. A liquid supply means 32 is connected to the bottom section 12 of the die 2 for filling up the tube blank 14 with liquid, also a volume control means 36 is shown to be connected to the liquid supply means 32 for controlling the amount of liquid that should be used for bulging the tube blank 14 into its desired shape. A balancing means 34 which coordinates and controls the energization of the hydraulic means 30 versus the liquid supply means 32 is shown to be connected with the hydraulic means 30.

The hydraulic means 30 comprises an oil supply 40, a pressure pump 42 and a hydraulic cylinder 44, which are interconnected through an oil feeding tube 46'.

A hydraulic piston 48 is slidably positioned in the hydraulic cylinder 44 and provides axial load to the die 2. Energizing of the oil pump 42 is controlled by the balance means 34.

The liquid supply means 32 comprises a liquid supply connected to a solenoid valve 50 which is connected through pressure lines 52 with a volume control cylinder 54 and a bulge pump 56. The bulge pump 56 is further connected with the movable bottom section 12 of the split die 2 by the pressure line 16. The operation of the liquid supply means 32 is controlled by the balancing means 34 during the initial starting position until a predetermined internal pressure inside of the tube blank 14, and an external hydraulic pressure for maintaining the critical initial position is established.

The split die 2 is mounted with its stationary top section 10 to the frame member 70. A platform 72 is slidably arranged by guiding means 74 between the frame members 70 and 70'. A solenoid valve 76 is connected between the bleed line 18 and the air outlet 78.

The balancing means 34 comprises a limit switch 80, having sensing means 80 riding on a cam 82 which is mounted on the movable platform 72, and thus the limit switch 80 is operated by the movement of the platform 72. Furthermore, the limit switch has an electrical circuit connection 84 with oil pump 42 and bulge pump 56 in order to energize or de-energize them depending on the position of the sensing means 86' of the limit switch 80.

A pressure sensing device 86 is connected to pressure line 16 and electrically connected to the balance means 34, and this pressure sensing device 86 is adapted to cancel out the efiect of the balancing means 34 when the predetermined pressure and critical position is reached. The liquid supply means 32 is provided with a volume control cylinder 54 which has a piston 90 slida'bly arranged therein and which piston has a micro-switch 92 with a sensing member 94 connected thereto. A precisely calculated profile plate 96 is mounted on the platform 72. A movement of the profile plate 96 will switch on the micro-switch 92 thus energizing the bulge pump 56, which is electrically connected thereto by circuit means 88, the bulge pump 56 will then pump liquid from the vacuum control cylinder 54 to the tube blank 14, however, as soon as liquid is pumped out of the vacuum control cylinder 54, the piston 90 will move through suction towards the B position which results" in a loss of contact between the sensing member 94 of the micro-switch 92 and the cam 96. As soon as the contact is broken between the sensing member 94 and the cam 96, the micro-switch 92 will stop the operation of the pump 56 until the profile plate 96 has been moved sufliciently upwards to contact sensing member 94 and the above mentioned operation is repeated again.

A main switch 100 is connected between an electrical source and balance means 34, for supplying electrical current to the balancing limit switch 80.

Having thus described and identified the several parts by character references, the operation is as follows:

Operation A tube blank 14 is placed inside of the split die 2 and the main switch 100 is pushed into its on position which energizes the limit switch 80 and in turn connects the oil pump 42 to the electrical source and thus operates the oil pump 42, the oil pump 42 pumps the oil from the oil supply 40, through the oil feeding tube 46 to the hydraulic cylinder 44. The piston 48 thus moves upwards thereby pushing platform 72 and accordingly enclosing the tube blank 14 between the stationary top section 10 and the movable bottom section 12 of the die 2. As soon as the critical position which is approximately 10.01 inch, as mentioned before, is sensed by the sensing means 80' the limit switch 80 will shut off the pump 42 through the electrical circuit means 84 and open the solenoid valve 50 automatically. 7

It will be obvious that any manual operation for closing the tube blank 14 in between the top section 10 and the bottom section 12 of the die 2 is very difficult, especially in regard to tube blanks which are of a very thin and fragile material because deflection of the material by an over pressure would not be noticed and thus harm the material.

The opened valve 50 will fill up the tube blank 14; and simultaneously fill up the volume control cylinder 54 and move the piston 90 from the B position to the A position. When the tube blank 14 is filled up with the liquid, the air moves out through the bleed line 18 and its valve 76. The valve 76 will automatically close when all the air is moved out of the system and then will electrically actuate the solenoid valve 50 to close and this valve 50 will then remain closed during the whole form ing operation. All the air is now taken out of the system and the volume control cylinder 54 is filled up with a sufiicient amount of liquid for bulging the part into the right shape by volume control.

The sensing means 80' will now sense which of the two pumps 56 or 42 should be energized. If the platform 72 is in its critical position the pump 56 will be energized first, if the platform 72 is out of the critical position, caused by the pressure of liquid in the tube blank 14, the pump 42 will be energized first.

Assuming that the bulge pump 56 is energized first, then a pressure is created inside of the tube blank 14 which tends to move the bottom section 12 into a down Ward position thereby moving the platform 72 likewise. The sensing member 8i) will sense immediately a downward movement of the platform 72 through the cam shaped member 82 and limit switch 80 will as a result thereof stop the bulge pump 56 and energize the oil pump 42 and thus increase axial load through the hydraulic cylinder 44, moving the tube blank 14 into its prior critical enclosed position, which then will be sensed again by the sensing member 80" of the limit switch 80. This procedure of alternate operation of both the oil pump 42 and the bulge pump 56 will continue until the aforementioned critical position (controlled by the balance means 34) and predetermined pressure (controlled by the pressure sensing device 86) is reached. This assures that the forming cycle of each part will start at the same initial condition of critical position and internal tube blank 14 pressure. As has been stated before, when the predetermined pressure is reached, the balance means 34 is then electrically switched inoperative, (by valve 36 through circuit means 84) thus for the further procedure, sensing means 80 is to be disregarded. Since the conditions of pressure and critical position are now satisfied, the bulging operation can begin.

The pump 42 is now continuously energized by circuit means 104 to create a continuous axial load, thus closing the die 2. As platform 72 moves upwards profile plate 96 will contact the sensing member 94 of microswitch 92 resulting in energizing the pump 56. A movement of the profile plate 96 will switch on the microswitch 92 thus energizing the bulge pump 56, which is electrically connected thereto by circuit means 88, the bulge pump 56 will then pump liquid from the vacuum control cylinder 5'4 to the tube blank 14, however, as soon as liquid is pumped out of the vacuum control cylinder 54, the piston 90 will move through suction towards the B position which results in a loss of contact between the sensing member 94 of the micro-switch 92 and the cam 96. As soon as the contact is broken between the sensing member 94 and the cam 96, the microswitch 92 will stop the operation of the pump 56 until the profile plate 96 has been moved sufficiently upwards to contact sensing member 94 and the above mentioned operation is repeated again. The amount of liquid which is moved step by step from the volume control cylinder 54 into the tube bank 14 is carefully controlled by the shape of the profile plate 96 and thus the bulging volume is regulated in coordination with the upwards movement of platform 72. At a certain stage the sensing member 94 will reach the end of the profile plate 96 and this will assure that the proper amount of liquid, as was calculated for bulging, has been used. At that moment the pump 56 will be switched off by the limit switch 92. The pump 42 (which was switched on when the balance means 34 was switched off and the bulging operation started) will continue to operate until the die is completely closed and the forming process has been accomplished. However, if during this closing process of the die 2 the internal pressure in the tube blank 14 would exceed a predetermined pressure, then in order to prevent over bulging of the tube blank 14 between the segments 4, 6, and 8 a pressure relief valve 102 will bleed off this excess. Because the part is in its final formed shape and practically confined by the die 2, the pressure sensitivity of the part is at this moment negligible. Automatically or manually the hydraulic pressure will be released and the die 2 opened by its split arrangements (not shown) allowing the part which is shaped into the desired con-= figuration to be removed.

It will be obvious that the present disclosed manner of axial load bulge forming by volume control and its automatic system incorporated therewith will save a considerable amount of time and also produce a more efficient way of forming.

Accordingly, various minor structural modifications might be suggested to the preferred embodiment herein described, by way of illustrated example only it should be understood that many changes could be elfected to exemplarly structure herein described without departing from the spirit of the present invention, and accordingly, it should be further understood that the inventor wished to enclose within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of the inventors contribution to the art.

I claim:

1. Apparatus for forming parts of tube blanks comprising in combination:

(a) die means having segmented parts slidably mounted in longitudinal relationship and end portions having support means for holding the tube blank,

(b) compression means mounted on said die means for compressing axially the tube blank thereby adapted to close the segmented die means,

(c) liquid volume control means hydraulically connected with one of said end portions of said die means for adding a predetermined quantity of liquid inside of the tube blank,

(d) balance control means for determining the required external axial compression of the tube blank and said balance control means connected with said compression means for sensing movement of said compression means, and

(e) pressure sensing means connected with said balance control means and hydraulically connected with the tube blank for sensing inside pressure thereof and adapted to inactivate said balance control means when a predetermined amount of pressure is reached in coordination with a predetermined axial compression sensed by said balance control means.

2. Apparatus for forming parts from tube blanks as claimed in claim 1, wherein said pressure sensing means is electrically connected with said balance means and adapted to inactivate electrically said balance control means when a predetermined pressure is reached in coordination with a predetermined axial compression sensed by said balance control means.

3. Apparatus for forming parts from tube blanks as claimed in claim 1, wherein said liquid volume control means is provided with automatic switching means which Will be activated when the required external axial compression of the tube blank and the required inside pressure of the tube blank has been reached, said automatic switching means thereby automatically feeding liquid from said liquid volume control means into the tube blank in controlled quantities while said compression means is in operation closing said segmented die means.

References Cited UNITED STATES PATENTS 506,247 10/ 1893 Moorfield 72-58 788,119 4/1905 Pope 72-58 1,886,831 11/1932 Murray 72-58 2,699,595 1/ 5 Zallea 29-421 3,072,085 l/ 1963 Landis 72----62 3,220,235 11/ 196-5 Peccerill 72-62 RICHARD J. HERBST, Primary Examiner.

Claims

1. APPARATUS FOR FORMING PARTS OF TUBE BLANKS COMPRISING IN COMBINATION: (A) DIE MEANS HAVING SEGMENTED PARTS SLIDABLY MOUNTED IN LONGITUDINAL RELATIONSHIP AND END PORTIONS HAVING SUPPORT MEANS FOR HOLDING THE TUBE BLANK, (B) COMPRESSION MEANS MOUNTED ON SAID DIE MEANS FOR COMPRESSING AXIALLY THE TUBE BLANK THEREBY ADAPTED TO CLOSE THE SEGMENTED DIE MEANS, (C) LIQUID VOLUME CONTROL MEANS HYDRAULICALLY CONNECTED WITH ONE OF SAID END PORTIONS OF SAID DIE MEANS FOR ADDING A PREDETERMINED QUANTITY OF LIQUID INSIDE OF THE TUBE BLANK, (D) BALANCE CONTROL MEANS FOR DETERMINING THE REQUIRED EXTERNAL AXIAL COMPRESSION OF THE TUBE BLANK AND SAID BALANCE CONTROL MEANS CONNECTED WITH SAID COMPRESSION MEANS FOR SENSING MOVEMENT OF SAID COMPRESSION MEANS, AND (E) PRESSURE SENSING MEANS CONNECTED WITH SAID BALANCE CONTROL MEANS AND HYDRAULICALLY CONNECTED WITH THE TUBE BLANK FOR SENSING INSIDE PRESSURE THEREOF AND ADAPTED TO INACTIVATED SAID BALANCE CONTROL MEANS WHEN A PREDETERMINED AMOUNT OF PRESSURE IS REACHED IN COORDINATION WITH A PREDETERMINED AXIAL COMPRESSION SENSED BY SAID BALANCE CONTROL MEANS.