NO122414B - - Google Patents

Description

Gravure press.

The invention relates to a deep-drawing press of the type that includes a larger drawing die, an outer drawing punch for drawing the workpiece in the larger drawing die, a smaller drawing die, an inner drawing punch for drawing the workpiece in the smaller drawing die, which dies and drawing punches are all interconnected designed and calculated for drawing the workpiece through the dies with one working stroke of the press, the inner drawing piston having a telescopic guide in the outer drawing die and lying inside this during drawing in the larger drawing die, and the end of the outer drawing die and a surface on the smaller drawing die form mutually opposite surface parts.

Such a deep-drawing press is, for example, known from the U.S. patent document no. 2,143,429. During deep drawing, an initially flat metal sheet is continuously deformed to, e.g. a cylindrical cup or box. The drawing punches pull the sheet metal through various dies, which are getting smaller and smaller. The outer area of the metal plate is held and firmly clamped each time between the preceding matrix and the associated drawing punch. As the drawing progresses, the pinched outer area of the metal plate is drawn into the drawing gap and is deformed to form the wall in the resulting! box. The material in the metal sheet is subjected to complicated flow and deformation processes. These metallurgical processes will not be discussed in more detail here. It would be sufficient to show that when the outer region of the metal plate held under pressure between the die and the drawing piston moves radially inward on its way in the drawing gap, the outer edge of the metal plate, which has a large diameter, is drawn into an area which radially lies further in, and you thus get a diameter reduction. This diameter reduction is caused by flow processes in the material. At the same time, however, as a result of the diameter reduction, the material will be subject to throw and fold formations. In order to counteract this and to make such folding impossible, a specific clamping pressure is necessary. If this clamping pressure is too low, creases occur. If the clamping pressure is too high, the frictional force, which acts on the radially inwardly moving material, will rise to such values that the material's further movement is prevented, so that the material breaks or tears.

In summary, this means that the material forms folds when the clamping pressure is too low and is exposed to breakage when the clamping pressure is too high.

It is therefore obvious that this must also be kept at a certain value depending on the firmness and strength of the material.

In practice, as you cannot precisely set a specific value and maintain it all the time, you want to regulate the pressure within a specific range, i.e. between a minimum value and a maximum value.

A minimum clamping pressure is achieved when the carrier for an inner draw piston hits the carrier of the second outermost draw piston. The inner drawing piston has then reached its end position and can no longer approach its associated matrix. If this minimum pressure is set too low, then the clamped outer area of the metal plate at the radial travel ring inwards in the direction of the tensile gap will fall at the diameter reduction connected to the travel ring inwards.

The maximum clamping pressure, on the other hand, is primarily dependent on the pressure with which the draw piston is pressed against the matrix.

The purpose of the invention is to carry out the press so that one can influence both the minimum value and the maximum value of this clamping pressure and can provide an opportunity for mutually assigning certain minimum pressure and maximum pressure.

According to the invention, this is achieved by providing the press with spacers that hold the aforementioned surface parts at a mutual distance corresponding to the wall thickness of the workpiece, thereby providing an abutment retention of the workpiece, by a pressure device that acts on the aforementioned outer drawing piston and is counteracted by the spacers, whereby a pressure retention of the workpiece, and by regulating means for controlling the relative movement of the drawing pistons, whereby the inner drawing piston is pushed out of the outer drawing piston and the workpiece is drawn between the two mentioned surface parts and through the smaller drawing die.

The length of the spacers can be set, in practice e.g. when applying or interposing discs, and the minimum clamping pressure, respectively the maximum height of the clamping gap between die and drawing punch, within which the material is thrown and deformed with fold formation, can therefore be easily set. It should be emphasized here that the spacers particularly come into effect at the end of a pull, when the material has for the most part already passed out of the clamping gap and into the pulling gap, and there is thus less material available for exerting a counter pressure.

The adjustability of the distance members' length and the regulation members are in an interaction. If spacers are too long, the material in the clamped outer area of the metal plate is exposed to too little pressure, and folds will therefore form as a result of the acting deformation forces. The same unfavorable effect is had if the holding pressure is set too low. What it depends on is therefore to set these two values, depending on the firmness and strength of the material being processed, to certain mutually assigned values. The invention enables this in a very simple way.

It is indeed possible to set a deep drawing press to specific values at the beginning of a drawing, but these values then only apply to a specific material thickness and for a specific material strength, and when these values are changed, the deep drawing press must be dismantled and readjusted hero. In practice, it is almost impossible.

With the invention, however, the values can be set in a very quick and simple way. The transition times required when transferring to others

material types and other material thicknesses are therefore small.

Further features of the invention will emerge from the patent claims.

The invention shall be described in more detail by means of examples with reference to the drawings where fig. 1 is a side elevation of the press at the beginning of the working stroke, with the hydraulic system shown schematically in dashed lines. Fig. 2 is a corresponding drawing as in fig. 1, at the end of the working stroke. Fig. 3 is an enlarged partial view of the press in fig. 1, but viewed from the opposite side and with all spacer elements shown. Fig. 4 is an enlarged partial view of the press in fig. 1, seen from the opposite side of the press. Fig. 5 is a vertical section along the line V - V in fig. 3. Fig. 6, 7 and 8 are corresponding drawings as in fig. 5, respectively following the lines VI - VI, VII - VII and VIII - VIII in fig. 3. Fig. 9 is a vertical section along the line IX - IX in fig. 18. Fig. 10 is a detailed section showing the relationship between a plate and its tension and guide rod. Fig. 11 is a detailed drawing of the fastening structure for the opposite ends of the tension and guide rods. Fig. 12 is a detailed section through a fixed distance element. Fig. 13 is a detailed section through a return stroke distance element. Fig. 14 is a detailed section through a hydraulic cushion. Fig. 15 is a detailed section showing the relationship between draw stamps and a matrix. Fig. 16 is an elevation, partially in section, showing the relative positions of the plates in the movable and fixed plate systems in the press during the initial pulling operation that follows. divisible after punching out the workpiece. Fig. 17 is a view corresponding to fig. 16 and shows the beginning of the first subsequent pulling operation and illustrates the transfer of the workpiece from one pressing step to the next. Fig. 18 is a view corresponding to that in fig. 16 and shows the workpiece after the drawing operations and partly after smoothing. Fig.

19 is a schematic diagram of the valve mechanism associated with

certain of the movable plates. Fig. 20 is a schematic diagram of the device's hydraulic systems. Fig. 21 schematically shows the progressive shaping of the workpiece in a modified form of the press with five drawing operations and one smoothing operation. Fig. 22 is a diagram showing the pressure pattern in the hydraulic system during the working stroke in the press which shapes the workpiece in fig. 21. Fig. 23 is an enlargement of part of the diagram in fig. 22, which more clearly indicates the pressure impulses. Fig. 24 is a view corresponding to that in fig. 5 of a modification and shows several sets that go inside each other, and fig. 25 shows a modified form of the holder for the movable plates.

The main press structure, which is arranged horizontally in the illustration, comprises a reinforced concrete base 10 on which a pair of reinforcement and wear plates 12 and 14 are fixed. At one end of the base 10 there is a stiffened cylinder holding plate 16 and at the other end there is a stiffened press bottom plate 18.

The plates 16 and 18 are fixedly placed on the reinforcing plates 12 and 14, with planar opposing vertical surfaces 20 and 22 exactly planar and parallel to each other and exactly placed at 90° on the plates 12 and 14, which are likewise planar, with the upper surfaces preferably placed in the same plane. The combined control rods and tension members 24 are all straight, mutually parallel and perpendicular to the plates 16 and 18, and have end portions 26 (Fig. 11) which are placed in brackets 19 and countersunk holes 27 in the plate rafts 20 and 22, with the ends 26 provided with threaded bores for receiving the head screws 21, which are passed through holes in the plates 16 and 18.

The movable plate system in the press can take many forms.

A practical arrangement, illustrated here, has several piston-carrying plates, one for each draw piston, a thrust plate to which the thrust piston is attached on one side and from which a draw piston projects from the opposite side, and a plate for the thrust pad and optionally for part of the blank punch, depending on whether the press is supplied with pre-punched workpieces or strip-shaped or square blanks are fed to the press. In what follows, the press will be described with a blanking operation carried out in the press, although it must be understood that round, pre-punched workpieces can be filled in the press and the blanking operation is omitted.

The pressure piston and tension piston plate 28, the tension piston plates 30 and 32 and the blank and cushion plate 34 are all equipped with openings 36 where liners 37 are inserted, the openings 36 being preferably arranged in the plate's four corners with the guide rods 24 slidably fitted in the liners 37 - the clamps 37" holds the liners 37 in place (see fig. 10).

Each of the plates 28, 30, 32 and 34 is equipped in the lower corners with suitable support parts 38 or 38' which can slide or roll (Fig. 25) on the reinforcement and wear plates 12 and 14. Preferably the parts 38 are positioned and removably fixed in the lower opposite corners of the plates and can be adjusted in relation to the associated plates by using spacers and the like which enable a fine vertical regulation, so that the desired situation can be obtained that the control rods 24 carry the plates 28, 30, 32 and 34, and these plates in turn carry the guide rods 24.

The plates 28, 30, 32 and 34 are controlled in terms of their relative movement towards each other and their respective relative positions at the end of the working and return strokes of the press, by means of three different and independent spacing systems.

One distance system is in the form of a stop device which is placed between the adjacent plates to determine the minimum distance between these plates by the relative movement towards each other. Another system of spacers is connected between the adjacent plates to return the plates to their relative positions at the end of the return stroke of the press. These spacers will be called return stroke stop spacers. The third system spacers are preferably in the form of hydraulic cushions placed between the adjacent plates 28, 30, 32 and 34 and have two different operating states, a locked state in which they act as a rigid columnar structure between the adjacent plates under pressure under a desired maximum, and a regulated condition in which the effective length of the pad as a spacer is reduced by means of valve devices which permit regulated relative movement towards each other between adjacent vertical plates.

In order to increase rigidity, lightness, parallel holding, maintenance and to obtain better accessibility for regulation, each of the three types of spacing system mentioned above is completely mutually independent in construction and function. However, possibly two or more of

these three systems are combined into a single system that can perform the same functions as the three systems.

The three spacing systems shall be described in more detail in connection with the illustrated embodiment of the invention, where the spacers or stop devices between the adjacent plates are made simply as a steel blv 3ck §0 whose vertical surfaces at the opposite ends are parallel to each&. z:<ter3. Each plate 30, 32 and 34 is utotyrfc with several such blocks as shown in Fig. 1 are placed equally distributed along the longitudinal axis A - A in Fig. 1 and for the sake of the other figures. only one of the disso fc.Uiilary shown in Fig. 1 in connection with

each of the plates. In practice, the outer surfaces of each of the plates 28, 30, 32 and 34 are machined with a particularly high degree of accuracy,

so that they are parallel to each other<, As the vertical surfaces of each of the plates are also parallel to the corresponding aot lying surfaces of the adjacent plates, this allows ei^S-Ugeasenfc that all the working stroke stoppers 40 which are in connection msci So swzå ® adjacent plates,

can have the same length. The placement etc. of the spacers 40 on it

vertical face of a plate in one of the adjacent pairs of plates can be done in any suitable way, e.g. as shown in fig. 12, where a head screw 41 is placed in a horizontal hole in the plate to which the spacer 40 is to be attached, and enters a threaded hole in one of the adjacent ends of the spacer 40. In this way, the vertical surface on one end of each spacer 40 be clamped to the vertical surface of its associated plate, and the opposite end of the spacer 40 then forms a contact surface which is parallel to the surface of the plate. The simple attachment of each spacer 40 to the associated plate also allows a convenient use of flat spacers that can be placed between the spacer 40 and the plate to change the effective length of the spacer 40.

The stroke stop spacers which position each plate 30, 32 and 34 in relation to each other as well as in relation to the end plate 28 at the end of the return stroke of the press can take many different forms. These spacers are indicated at 42, and they are of a construction that does not interfere with the relative movement of the vertical plates during the working stroke of the press, at the same time that the spacers 42 during the return stroke of the press act as devices for returning the plates 30, 32 and 34 in a certain ratio to each other during the return of the pressure piston plate 28 at the end of the return stroke of the press.

In the form illustrated (Fig. 13), each spacer 42 comprises a rod 44 which is fixedly attached at one end to a plate in the press's movable plate system and has a free, sliding fit in a groove 46 in the opening 48 of an adjacent plate . The stop head 50, which can preferably be regulated by the use of spacers between the head 50 and the rod 44, is attached to the opposite end of the rod 44. When adjacent plates approach each other during the working stroke of the press, the rod 44 will slide through the liner 46, relative movement finding place between the head 50 and the outer surface of the liner 46. During the return stroke of the press, movement of the pressure piston plate 28 will provide the necessary relative movement, so that the head 50 comes to rest against the outer surface of the liner 46. In this employment between the opposite surfaces on liner 46 and head 50, rod 40 will come under tension and the movement of one plate will be progressively transferred to the next adjacent plate.

The spacers '42 are preferably placed at equal intervals around the longitudinal axis a - a in fig. 1, as is the case with the spacers 40. Each spacer 42 is preferably of substantially the same effective length so as to complement the parallel relationship between the plates 30, 32 and 34.

By the fact that the rods 44 have mutually equal effective lengths and are parallel to the guide rods 24, at the same time that the adjacent surfaces of the liners 46 and the heads 50 are parallel to each other and to the two surfaces of the movable plates, movement of the plates 30, 32 and 34 is achieved by means of the pressure piston plate 28 during the return stroke of the press without disturbing the parallel relationship between the components in the press.

The third spacer system in the press is more complex both in terms of structure and function than the systems with the spacers 40 and 42. Because of this, each set of pads that are in connection with each of the plates 28, 30 and 32 will be indicated and described with their own reference number.

In general, each<*>single pad comprises a cylinder which is firmly placed on the associated plate in the movable plate system and functions as a unit together with this. A piston is arranged in each cylinder and extends out of the cylinder. The part of the piston that protrudes from the cylinder performs the function of a push part of adjustable length, which push part spreads out the plates in the movable plate system and controls their mutual movement order in a closing direction during the working stroke of the press. The cylinders in the set of hydraulic cushions that are connected to each of the above-mentioned plates are preferably equally distributed about the longitudinal axis a-a, as is the case for the spacers 40 and the spacers 42.

A set of hydraulic pads 52 is placed on the plate 28, another set of pads 54 is placed on the plate 30 and a third set of pads 56 is placed on the plate 32. Each set of pads 52 and 54 and 56 respectively comprise the cylinders 58, 60 and 62 and pistons 64, 66 and 68. It should be noted that the pads in each set are the same length and that each set of pads is a different length from the other sets. The difference in length of the pads is determined by the necessary distance between the plates in the movable plate system when this system is moved forward by the pressure piston as a sliding column of constant length. As described in more detail below, hydraulic fluid is sent to the cylinders 58, 60 and 62 to act on the ends of the pistons 64, 66 and 68, respectively, so that the pistons 64, 66 and 68 are moved to their extended positions, which positions are preferably determined by the effective lengths of the spacers 42. The liquid pressure in the pads 52, 54 and 56 thus serves to put the rods 44 in the spacers 42 under tension, as it acts to separate the individual plates 28, 30, 32 and 34.

When the hydraulic fluid is blocked in the cushions 52, 54 and 56 by means of suitable valve devices, the pistons will act as relatively fixed push columns which are placed between the plates 28, 30, 3*2 and 34. By regulating the fluid flow from the cushions by means of suitable valve devices, the pads will collapse and allow the plates in the movable plate system to approach each other.

The press's piston pressure is transmitted to the press's metal-forming tools through the hydraulic pads 52, 54 and 56. When the pads 56 have collapsed to a point where the spacers 40 on the plate 34 abut against the plate 32, the limit of the relative movement towards each other between the plates 32 and 34 reached. In the same way, when the cushions 54 have collapsed to a point where the spacers 40 on the plate 32 abut against the plate 30, the limit for the relative movement towards each other for the plates 32 and 30 has been reached. A similar situation occurs when the collapse of the pads 52 allows the spacers 40 on the plate 30 to abut against the plate 28. In the case of the successive collapse of the pads

52, 54 and 56, the labor applied to the metal forming tools will be transferred to the "locked" pads, and the colliding pads will hold the leading plates of the movable plate system together when they have reached the position in which they can come together, which position is determined by the spacers 40. The further function of the pads 52, 54 and 56 as pressure pads will be described in connection with the pressure pistons therein. movable plate system.

Each of the plates 28, 30 and 32 respectively has a tubular draw piston 70, 72 and 74 which engage each other with a tight sliding fit. As the pulling pistons will normally be made of tool steel, preferably non-ferrous liners 75 (fig. 3) are used between the pulling pistons to avoid rubbing damage.

The reduction in the diameter of the workpiece between the drawing operations is such that the drawing punches 70, 72 and 74 have sufficient wall thickness to be rigid. They are fixedly connected to their respective plates in the movable plate system in a suitable manner, so that their longitudinal axes coincide with the axis a - a in fig. 1. As shown, each draw piston 70, 72 and 74 has a series of threaded holes 76 in the inner end for receiving the screws 77 which attach the draw pins to the plates. Plates 30, 32 and 34 have apertures 78 concentric with the draw pins to allow the draw pins to pass through the plates with clearance while allowing the plates to perform relative motion relative to each other.

When the press is at the end of its return stroke, and in the position from which the working stroke begins, the front ends 80, 82 and 84 of the draw pistons 70, 72 and 74 are preferably placed in a somewhat stepped position, as best shown in fig. 4. This arrangement allows a slight creeping of the drawing punches in relation to each other without there being any tendency for the base of the metal object to be formed. This staggered arrangement of the draw pistons has the further advantage that it provides a slight delay in the successive engagement of the draw pistons so that the timing of the draw movement becomes less critical.

The number of plates in the fixed plate system and the tools placed on the plates therein will usually be determined by the number of plates in the movable plate system and by the object to be shaped by means of a single continuous stroke of the press. If blank punching is to take place in the press, the first fixed plate will perform the blank punching operation as well as the first pulling operation. The following plates can be equipped with tools for further drawing or smoothing operations or a combination of these. If the metal object to be formed is to have a detailed bottom, then the innermost drawing punch will have its outer end shaped so that it performs the detailed operation in cooperation with a detailed matrix that sits on the last, fixed plate or on the base plate 18. Preferably there are holes in the plate 18 to enable it to carry a drawing or smoothing matrix as well as a scraper mechanism, when details are not to be carried out at the bottom of the shaped object.

In the illustrated form of the invention (fig. 4), the fixed plate system in the press comprises the plates 86, 88, 90 and 92 which all have clearance holes 94 of different sizes and with the center located on the axis a-a. The fixed plates are of a rigid construction and are equipped (in the same way as plates 28, 30, 32 and 34) with holes 36 in the free corners, with liners 37 that t&z* against the guide and tension rods 24 with a tight sliding fit , so that the fixed plates can be adjusted along the rods 24. As with the plates in the foldable plate system, it is important that the plates are aligned parallel and concentric. For this reason, the vertical surfaces are on. each plate 86s 88 8 90 and 92 parallel to each other as well as to the faces of the other flat plates. Between each of the plates 86, 88, 90 and 92 and between the plate 92 and the base plate 18, a set of spacers 98 is arranged evenly distributed around the axis a-a. The spacers 98 have a length that depends on the necessary space between the plates for forming the metal object, and they are usually increasing in length in the direction of the pj<p>ease's working stroke. However, the spacers 98 in each set are preferably of the same length so that they keep the plates 86, 88v, 90 and 92 parallel, with the ends of the spacers 98 butting against the vertical surfaces of the adjacent plates. Head screws 100 can be used to connect the spacers 98 and the plates 18, 86, 88, 90 and 92 into a rigid complex of parallel plates which are horizontally aligned on the guide rods 24, while being vertically held up from the supporting surface of the foundation 10 in the press using adjustable leveling screws 101.

When a round workpiece is to be punched from a strip blank or a square-cut blank S (fig. 4), a blank punch 102 in the form of a flat ring is placed on one surface of the plate 34. The blank matrix 104 is placed on the opposite face of the fixed plate 86 and has the shape of a ring that faces a cutting egg against the bar 102. The first drawing matrix 106 is located inside the workpiece matrix 104. A flat, vertical surface 108 on the drawing matrix 106 forms a holding surface which together with the flat surface 109 (fig. 3) on the workpiece punch 102 acts as a pressure pad for controlling the marginal part of the punched workpiece B during the first pulling operation. In all subsequent drawing operations, the telescoping drawing pistons in the press act as pressure pads on the progressively drawn workpiece B.

Plates 88 and 90 are shown with drawing dies 110 and 112 respectively while plate 92 has a smooth die 114 on one side and a wiper mechanism 116 on the opposite side. A die 118 for the detail work in the bottom of a metal object to be formed is shown placed on the inner surface of the bottom plate 18. The workpiece will be passed through the drawing die 112 and the smoothing die 114 with the drawing punch 70, which is placed on the movable plate 28. The drawing punch 70 will also perform the detail work on the bottom of the workpiece in the die 118 at the end of its working stroke, and the completed workpiece will be ironed by the drawing punch 70 by means of the mechanism 116 during the return stroke of the press.

The drawing piston 74, which is placed on the movable plate 32, will pass through the drawing matrix 116 until it is in the closest position in relation to the drawing matrix 110. In this position, the end 84 will act as a pressure pad in connection with the radial surface 111 of the matrix 110 .When the outer drawing ram 74 is stopped by the spacer 40 on the plate 34, the inner drawing ram 72 on the movable plate will draw the workpiece through the drawing die 110 and continue to the vicinity of the drawing die 112, in which position the end 82 of the drawing ram 72 will act as a pressure pad.

The present invention primarily relates to the deep drawing of metal objects without annealing, where the ratio between the height and the diameter of the workpiece at the end of the drawing operation, which is carried out with a single, continuous stroke of the press, is considerably greater than what has hitherto been carried out commercially. A height to diameter ratio exceeding 4 to 1 and up to 9 to 1 has been achieved under practical commercial operating conditions. When one or more smoothing operations are performed in the press, after the last repeated drawing operation, the ratio of height to diameter of the workpiece can easily be of the order of 8 to 1 to 15 to 1.

Due to the heat developed by the drawing and smoothing operation, thermal expansion will occur in the drawing punches, and this will affect the performance of the press. When the press has been out of service for an extended period of time and the temperature of the drawing punches has returned to mostly room temperature, adjusting the spacers in the press at this time to position the ends of the drawing punches correctly in relation to the drawing dies will result in incorrect adjustment when the drawing punches brought up to the temperature reached during longer operation of the press. To avoid this situation, a long, completely enclosed, thermostatically controlled electric heating unit 120 (fig. 3) can be used, which is located inside the innermost draw piston 70. The unit 120 is shown connected to an electrical outlet 122 for easy connection -to a power source. In this way, the drawing pistons can be heated in advance and kept at a desired temperature and start-up adjustments can be avoided.

The workpiece B is drawn in all the drawing operations preferably over a relatively uniform radius 124 (Fig. 15) with minimum clearance between the drawing die and the inner drawing punch compared to standard practice. Thereby, the workpiece has an inner diameter that is close to the outer diameter of the drawing piston, preferably up against a point where it hangs firmly on the drawing piston. During application of the invention, good results have been achieved when the clearance in the axial passage 126 is of the order of 60-70% of the clearance recommended by standard handbooks for materials with small thicknesses. While standard practice requires a clearance 126 of 2.3 times the thickness of the workpiece being drawn, for example the clearance used in the new practice is preferably of the order of 2.2 times the thickness of the workpiece.

While it has heretofore been the practice to increase the clearance on passage 126 in the subsequent drawing stages due to the tendency of the workpiece to become thicker during each successive drawing stage, the purposes of the present invention are best achieved by maintaining substantially the same or reducing the clearance in all subsequent drawing steps and produce at least a minor smoothing effect on the top area of the workpiece in each drawing step.

The smoothing operation at the top of the workpiece is a result of the reduction in clearance compared to standard practice forming an interference fit between the drawing punch and the drawing die and the thickened top part of the workpiece. During the drawing steps which are carried out according to the present invention by means of a single, continuous stroke of the press, the top area of the workpiece that is smoothed will be larger in each subsequent drawing step. As will be discussed more fully below, the method results in what appears to be a reduction in the amount and/or magnitude of work and stress hardening of the workpiece with the same reduction in diameter, compared to what has heretofore been achieved under generally accepted commercial practice. In addition to the apparent lower work and/or stress hardening, a high degree of work hardening uniformity is maintained around the circumference of the workpiece, avoiding overworked local areas which would tend to repair metal fractures in subsequent drawing steps or which would necessitate annealing of the workpiece before performing secondary operations on workpiece B after it had been removed from the press. In the following sections, the structural factors which are assumed to contribute to the uniformity of the work- or strain-hardening of the workpiece will be reviewed. The initial movement of the movable plate system along the guide and tension rods 24 rigidly connects these to the rigid mass of the fixed plate system by means of the guide pins 128 (Fig. 18) on the movable plate 34 which enter the bushings 113 in the fixed plate 86 with a sliding fit with a small tolerance. As the pulling operations are carried out in sequence, the mass of the movable plate system slides more compactly as it moves towards the area where the pulling operations are carried out. This increase in compactness comes from the relative movement towards each other of the adjacent movable plates under the control of the hydraulic cushions and has the effect of helping to make the components of the movable plate system more rigid, parallel and concentrated.

The fact that the drawing punches in the press go into each other, together with the fact that the movable plate system that carries the drawing punches is rigid and parallel, results in the drawing punches being brought concentrically up against the drawing dies with a very high degree of accuracy. This concentric relationship between the drawing punches and the dies is maintained through all the different drawing operations carried out in the press during a

single, continuous stroke of this. As a result, excellent control of the metal in the workpiece is obtained when this concentric relationship is combined with the movement of the workpiece from a drawing punch with a guiding action through the drawing die and back onto the next drawing punch. This factor plus a tendency for the workpiece to stick to the drawing punch, and smoothing of the top surface of the workpiece in each drawing step, together seem to ensure uniformity of the work or stress hardening of the workpiece around the circumference.

With very highly polished drawing matrices, a two-digit reduction in the workpiece size of an order of magnitude of 80% has been achieved during

of a single, continuous stroke of the press under commercial manufacturing conditions without metal breakage and at the end of the drawing operations such a high reduction has been achieved that the metal in the workpiece is still able to withstand forming operations on the open end of the workpiece, such as bending operations without prior annealing. It has also been possible to achieve successive reductions, each of the order of 25 - 30%. For comparison, it can be mentioned that it is otherwise common to carry out the reductions according to a sliding scale, such as 25%, 15% and 10%.

Because of the results obtained with the present invention, it is practical to have a reduction in the first drawing die 106 of the order of magnitude of 40% and to carry out the drawing in each of the drawing dies 110 and 112 with reductions of an order of magnitude of 25%• When using three matrices, you will achieve a two-digit reduction without annealing on oa. 75%, and if four draw stages are used, the total reduction can exceed 80%. These results can be compared with normal practice, which gives a total possible reduction under normal conditions of approx. 55% preheat annealing.

Another area where the hi" described press deviates from usual practice concerns the speed of SB number drawing in the press. While common practice has so far indicated high-speed islands of an order of magnitude of 13 - 21 m per minute, outstanding results have been achieved with the new press with drawing speeds of 30 m per minute.

It turns out that during the shaping of metal with the new press, the size of the work hardening is reduced to a large extent compared to the size that is found when the same workpiece is processed over the same tools but with an interruption between each operation instead of all the operations being carried out in the course of a single continuous stroke of the press.

In an attempt to determine the reduction in work hardening, numerous photomicrographs have been taken of workpieces drawn from the same blank strip as it comes from the rolling mill.

Some of these workpieces were drawn in a press constructed and operated in accordance with the invention so that they were completely formed by a single, continuous and uninterrupted stroke of the press. Other work items were formed by interrupting ar-. pickling stroke in the same press after the first drawing operation and then complete the subsequent drawing operations. Some of these workpieces were taken out of the press after the first drawing operation and were then transferred to ordinary drawing tools to complete the drawing operations, the reductions carried out with the ordinary drawing tools corresponding to the looped drawing operations in the press so that the total degree of deformation of the metal would be substantially the same in the articles which were fully formed in the press as in the articles partially formed in this press and then finished on ordinary tooling.

The residual machinability of the workpieces drawn in the press, compared to the workpieces completed on conventional tooling, clearly indicates less work hardening. However, a comparison of the grain structure on the photomicrographs has not fully explained the large increase in the remaining machinability of the workpiece and the large increase in the total reductions that can be achieved.

That the workpiece can still be processed after the end of the drawing and smoothing operations is of great commercial importance when secondary operations are to be carried out. The fact that you still have machinability makes it possible for such operations to be carried out directly after you have removed the object from the drawing press and without it being necessary to subject the object to annealing.

The hydraulic pads 52, 54 and 56 are placed on and move together with the plates 28, 30 and 32 in the press. The supply of hydraulic fluid to the pads and the control of the hydraulic fluid pressures in the pads during the joint as well as the relative movement of these plates should therefore be carried out without resorting to a complicated hydraulic system which will greatly increase the costs of the press and its maintenance. The amount of hydraulic fluid required in large presses and the rapidity with which the fluid must be transferred to the pads during operation of the press, without overheating or foaming in the fluid, increases the problem.

The hydraulic system for fluid flow to and from the hydraulic pads is separate and distinct from the hydraulic system that can be used to operate the pressure piston during press operation.

and return stroke. This is the case even though the forces exerted by the pressure piston on the movable plate system create the working pressure in the hydraulic cushions.

Preferably, the hydraulic fluid used in is transferred

the hydraulic cushions 52, 54 and 56 between the cushion cylinders and the supply tank 132 (Fig. 20) through large flexible hose lines 134. These lines are mounted so that they do not wear down when their ends, which are attached to the plates, travel back and forth under the pressure of the press operation.

In order to avoid as many pipes and external branch pipes as possible, each of the movable plates 30, 32 and 34 has passages 136 (Fig.

3, 5} 6 and 7) which supply hydraulic fluid to the pad sets. On top of each of the plates there is a hydraulic manifold 138 for hydraulic connection of the passage 136 in the plates with a main control valve 140.

From fig. 5j 6 and 7 it can be seen that the locations of the passages 136 do not follow a specific pattern, but to a large extent depends on where the transverse clearance holes are located in the plates 30, 32 and 34. In practice, it may be necessary to drill two or more intersecting holes in the plates and then plugging the ends into some of these holes to provide a fluid passage 136 between an edge of the plate and a passage 148 in a hydraulic pad. It is also not always possible to let all the passages 136 open from the same edge of the plates 30, 32 and 34. In fig. 5 this has been possible, while in fig. 6 and 1, two external connections 168 are shown which sit on the vertical edges of the plate 32 and connect the passage 136 between the two lower hydraulic cushions with the branch pipe 138 on the upper edge of the plate.

The plates 30 and 32 have pressure switch valves 142 (fig. 1 and 19) on the sides. Each of the valves 140 and 142 has a manually operated knob 144 for pressure setting. When operating the pressure it is generally necessary to make adjustments to the pressures by manipulating the cam 144 when changing from one material to another of the same thickness. For example, aluminum, brass and steel articles, made from a blank of the same thickness, have been successfully drawn over the same dies by simply changing the operating pressures in the hydraulic pads 52, 54 and 56.

Each of the passages 136 has a connection with the longitudinal passage 148 in each piston in each hydraulic cushion. The outer end of each piston has a sealed connection with passage 136 in the plate to enable hydraulic fluid to flow to and from the cylinder through passage 148 in the piston. When the fluid is confined or locked in the cylinder 62 by means of the valve 142, each cylinder and each piston will collectively function as a fixed length thrust column between the adjacent plates of the movable plate system. When the valve 140 is operated by the pressure switch valve 142, which will be described in more detail below, the liquid from the cylinder 62 is metered through the passages 148 and 136 and the cylinder and the hydraulic pad will coincide in an adjustable manner so that it is possible for the adjacent plates in the movable plate system to approach each other.

Reference is made to fig. 19 where the branch pipe 38 on top of the plate 32 is in connection with the passage 136 which in turn goes to and is in connection with the passage 148 in the hydraulic cushions belonging to the plate 32. The valve body 170 in the valve 140 is placed on the branch pipe 138 and has a hole 172 which lies above an opening 174

in the branch pipe 138 in connection with the passage 136. A sleeve 176 is placed in the hole 172 and is equipped with pear-shaped openings 178 which open into an annular passage 180 which in turn is in connection with the passages 182 which are connected to the hydraulic fluid supply 132 by means of the flexible lines 134. A relief valve 184 is placed in the sleeve 176 with a spring 186 which holds it in place in the seat in a position where it closes the openings 178. A small opening 188 in the valve 184 transfers the fluid pressure in the hydraulic cushions which is formed by the pressure piston 150 of the press, to the switch valve 142 through the opening 90 and the passage 192. The switch valve 142 has a spool valve 194 with a piston 196 at one end which is stored so that it engages with an adjustable stop surface 154 on the adjacent plate 43 so that the valve 194 is moved to the left (as seen in Fig. 19) against the tension from a spring 196, from the position shown in which the valve 194 blocks the passage 192 s such that the liquid in the hydraulic cushions 54 is locked, thereby preventing the adjacent plates 32 and 34 from approaching each other. When the valve 194 is moved to the left, the passage 192 is brought into alignment with the annular passage 198, and the fluid flow passes through a vein opening 200 into the passage 202 and thence to the opening 204. A valve

206 acts to close orifice 204, and the fluid pressure required to lift valve 206 from its seat is determined by the tension on its loading spring 208.

The cam 144 can be operated to vary the tension on the spring 208 in the diverter valve 142. The lifting of the valve 206 from its seat in the opening 204 will allow the flow of liquid in the passage 136 so that the relief valve 184 is lifted and opens the holes 178. The liquid trapped in the hydraulic cushions 56 then return to the supply device 132 when the cushions begin to collapse and the plates 32 and 34 are able to approach each other. The adjustment of the tension on the spring 208 by means of the cam 144 will determine the resistance to collapsing provided by the fluid in the hydraulic cushions 54. When the relief valve 154 is under the control of a switch valve 142, a valve 210, which can:- itself in the same housing as the valve 184 and which is loaded by means of the spring 212, is used to trigger the relief valve 184 under conditions e^m exceeds the regulation of the valve 142, such as in case of overload.

In order to enable the liquid that returns to the supply 132 to be handled quickly c.- with relatively small lines, two passages 182 are preferably arranged in the valve body 170 for this purpose. The tank 132 is under constant pressure as a result of air pressure applied to the surface. This pressure is sufficient to send the fluid back to the hydraulic cushions 54 and to keep the valve mechanism in working condition. This pressure is of the order of 1.4 to 7 kg/cm and returns the liquid past a ball valve 214 to the passage 136

which leads to the hydraulic cushions 54. This liquid is also sent through the passage 216 so that it acts against the spool valve 194 when this is in the position shown.

The flexible hose connections 134 are placed above the press and are connected to the branching device 218 (Fig. 20) which in turn is connected to a channel 220 leading in one direction to the filters 122 and the outlets 124 and in the opposite direction to the intake 226 on the supply 132. Control valves 228 cause fluid from the supply 132 to flow through the filters 222 and fluid flowing from the pads to flow to the intake 226, bypassing the filters. In this way, a circulation of cooled liquid is provided for the pads. The lines 134 and manifolds 218 are routed over the press to allow the plates of the movable plate system Ix&a to move back and forth during the operation of the press without damaging the line 134.

To more fully describe the functioning of the shift valve 42, it must be assumed that the hydraulic pressure system that operates the pressure piston 150 is capable of exerting 50 tons of force on the pressure piston 150, which force is in turn directed through a semi-rigid connection 152 (fig. 3) to the plate 28. Under the assumed conditions, the main valves 140 would be regulated so that they maintained a force of something over 50 tonnes or such a force that each of the four hydraulic cushions connected to the plates 28, 30 and 32 is capable of to exert a counter force greater than 12.5 tonnes.

At this point it should be noted that the main control valve 140 of the plate 34 preferably does not have a shift valve 142 connected. Instead, it is itself a pressure regulating valve and operates to maintain a constant pressure in the pads 56 which are placed between the plates 32 and 34, sufficient to hold the punched workpiece B so that it does not wrinkle while the first trekkeope-rasjoh is performed.

Assume that the valve 140 in the plate 34 is set to a pressure whereby the pads 56 will exert a total restraint of 15 tons available during the first pulling operation. These 15 tons work all the time and will be maintained throughout the first pulling operation. When the 15 ton holding force is subtracted from the 50 tons of available force on the pressure piston 150, the remaining 35 tons are available for the first pulling operation with the pressure piston 150 delivering only the amount of force that opposes its working stroke motion. When the hydraulic cushions are filled with fluid, and this fluid is locked or trapped in them, it causes all the hydraulic cushions 52, 54 and 56 located between the plates 28, 30, 32 and 34 to act as a thrust column until the movement on the plate 34 is stopped and the pressure from the pressure piston 150 on the movable plate system overcomes the pressure setting on the valve 140 on the plate 34 whereby the liquid that is confined in the pad sets 56 is driven out of them so that the plate 32 can approach the plate 34.

When the movable plate system is moved as a unit by means of a pressure piston 50, at the beginning of the working stroke of the press, the guide pin 128 of the plate 34 enters the liner 130 of the plate 86 so that the plate 34 is rigidly coupled with the plate 86 just before the workpiece punch 102 impinges counter-strip blank S and forces the blank S against the cutting edge of the blank die 104. The strip S must be cut with a force less than 15 tons or the pad sets 56 will begin to collapse and the workpiece will be engaged by the drawing punch 74 before the workpiece B is completely cut and the surface 109 of the workpiece punch is in such a position that it acts as a pressure pad.

When the pads 34 and 86 have approached each other as shown in fig. 4 and the cutting of the workpiece B from the strip blank is completed, the spacers 40 located between the plates 34 and 86 come into operation and limit the movement of the plate 34 towards the plate 86. The plate 34 stops in a position where the surface 109 of the blank punch 102 has a distance from the surface 108 of the first drawing die 106 on the plate 86 approximately corresponding to the thickness of the workpiece.

With the joint movement of the movable plate system, which has brought all the plates 28, 30, 32 and 34 to the point where the spacers 40 between the plates 34 and 86 have stopped further impact movement of the plate 34, the pad sets 56 which have determined the distance between the plates 32 and 34, begin to collapse under the force exerted by the pressure piston 150 and which exceeds the 15 tons pressure pad force exerted on the spacers 40 between the plates 34 and 86. This pressure acts against any tendency for the marginal parts of the workpiece 8 to wrinkle and thicken during the first drawing operation.

When the pillow sets 56 collapse, hydraulic fluid in the cylinders 62 will be forced out through the longitudinal passages, 148 in the pistons 68 and into the passage 136 in the plate 34 and through the control valve 140 to the tank 132 (fig. 20), the fluid flow between the valve 140 and the tank 132 go against the supply pressure which is created by the air pressure of 1.4 - 7 kg/cm 2 on the hydraulic valve in the tank 132.

During the initial coincident movement of the pads 56, the plate 32 and its associated drawing piston 74 will be moved forward so that it moves the drawing piston 74 into contact with the workpiece B which is on the surface 108 of the drawing die 106, which sits on the first plate 86 in the fixed plate system. The movement of the movable platesy- . stem as a unit is now limited to the plates 28, 30 and 32 and the continued working stroke of the pressure piston 150 will initiate the first drawing operation by sending the drawing piston 74 through the drawing die 106 in the plate 86.

In fig. 16, the relative positions of plates 32, 34 and 86 are shown with the first pulling operation partially completed. How far the plate 32 has approached the plate 34 is indicated by the distance the head 50 of the "kickback" spacer 42 protrudes from the surface of the liner

46 which sits on the vertical surface of the plate 32. It should also. it is noted that the pressure reversing valve 142 which sits on the plate 32 approaches its

initiates 154 on disc 34.

Fig. 17 shows the relative positions of the plates 32, 34 and 86 after the completion of the first drawing operation and at the beginning of the next drawing operation in the drawing matrix 110, which sits on the plate 88. The spacers 40 between the plates 32 and 34 are now active so that the limits the distance between the plates 32 and 34, since the collapse of the pads 56 has ended and the pressure reversing valve 142 has engaged its actuator 154 on the plate 34, so that the liquid in the pad sets 54, which forms the distance between the plates 30 and 32, is brought out by " locked" position. That the cushions 54 collapse will initiate the next pulling operation, when the movable plate system's working stroke, which is now limited to the plates 28 and 30, continues.

It is in connection with the second pulling operation that the pulling piston 74 in the first pulling operation takes on the dual function of a driver and as a pressure pad for the subsequent pulling operation. This dual function is described in detail earlier in connection with fig. 15. To function properly as a pressure pad, the end 84

on the pulling piston 74 is held at a proper distance from the surface 111 on it

second drawing matrix 110. It is one of the functions of the spacers 40 which are located between the plates 32 and 34, to provide this distance. Because the length of the spacers 40 between the plates 32 and 34 is determined without regard to the thermal expansion in the drawing piston 74 in the longitudinal direction, the pinching of the workpiece can be so great that it will cause breakage in the workpiece during the second drawing operation. It is for this reason that one may find it desirable, as suggested above, to keep the telescoping draw piston unit at a controlled temperature at all times, thereby avoiding start-up regulation or metal breakage as a result of thermal expansion when operating temperatures are reached during production operation.

As mentioned above, for the sake of overview, only one spacer element in each of the three spacer systems for the movable plate system is illustrated in fig. 1 and 2. In fig. 3, 4, 16, 17 and 18, however, all these distance elements are shown in the actual number used in the press and as they appear in side elevation.

In fig. 5»6, 7 and 8 are the sections taken along section lines in fig. 3 so that the distance elements which are omitted in fig. 1 and 2 are present.

Of the elements in the three spacing systems that are individually shown in fig. 12, 13 and 14 require only the spacers in fig. 13 and 14 that the plates 28 and 30 in the movable plate system are provided with clearance holes to allow the plates 28 and 30 to move from the position in fig. 1 to the position in fig. 2 in the working class of the press.

In fig. 7 shows clearance holes 50' on the heads 50 of the spacers 42 which are attached to the plate 32. In fig. 7 also shows clearance holes 56' in the plate 30 to allow passage of the cylinder 62 and the pads 56 which are placed on the plate 12. Fig. 8 shows the clearance holes in the plate 28 for passage of the cylinders 60 in the pads 54 which are placed on plate 30.

Fig. 5, 6 and 7 indicate distribution on the plates 30, 32 and 34 of the spacer elements in the three systems illustrated in Fig. 12, 13 and 14. The elements are shown used in sets of four which are connected to each of the plates 30, 32 and 34. They are preferably distributed as equally as possible about the axis a - a and in this way help to maintain the parallelism of the plates 28, 30, 32 and 34. The number of spacer elements in each set can of course be varied and likewise their placement on the plates.

It is possible to have several tool sets in the same press. For e.g. to adapt the press to the economic production of low-cost south-facing cans for use in packaging food and soft drinks, a large number of sets of telescoping drawing punches can be placed on the plates in the movable plate system, with corresponding sets of dies placed in the fixed plate system of the press. Instead of the plate 28 e.g. has only one drawing punch, it can thus have a large number of drawing punches, the number depending on the size of the "box to be drawn and the practical and economic limitation regarding the size of the press.

Fig. 24 illustrates a modified form of the invention where three sets of telescoping draw pistons are shown installed in the press instead of the single set of telescoping draw pistons not shown in Fig. 1. Fig. 24 is a cross-section which largely corresponds to that in fig. . 5. It should be noted that each of the sets comprises the draw pins 70', 72' and 74' and that these sets are grouped around the central axis of the plate 34' instead of being positioned concentrically with the axis in the same manner as the single set in fig. 5- The marked i»eference numbers in fig. 4 indicates the same parts as indicated in fig, 5 and corresponding unmarked reference numbers.

In order to provide possible answers to the "unexpected results which have been obtained in commercial art - the present invention in the production of metal articles" which are produced from sheet metal by means of a simple, continuous and uninterrupted blow from the press, these objects have been scrutinized by using photomicrographs, by residual stress analyzes and determination of mechanical properties.

With the aim of making a comparison between objects produced using the invention and objects produced according to well-established commercial methods that have been used up to now, every possible measure has been taken to obtain largely identical test pieces. These blanks have been drawn with largely identical tools, one set of tools having been used in a press constructed according to the invention and another set of tools having been used in a conventional deep drawing apparatus. Analyzing the results obtained from comparable samples, metal fracture, metal splitting, degree of work hardening, remaining workability in the drawn object and uniformity of mechanical properties all have. have been factors of fundamental importance for consideration from a commercial point of view.

As previously indicated, studies that have been carried out on comparable samples have indicated that there has been a reduction in the degree of work hardening (expressed in residual machinability) during the production of metal objects in the new press compared to the work hardening obtained when metal objects are subjected to the same amount of metal deformation and formed by existing conventional methods.

Investigations regarding residual stresses seem to indicate that use of the new press tends to reduce the accumulation of residual stresses of a nature that is detrimental to the deep drawing of metal objects.

Example 1.

This test was performed on sheet metal blanks guaranteed by the metal manufacturer to be substantially identical in all respects. The blank size was 311.15 mm, the blank thickness 1.15 mm, the material 100 S low carbon tensile grade steel and the finished box had an outer diameter of 101.6 mm and a height of 222.27 mm. The drawing dies had radii of 6.35, 7.938 and 12.7 mm respectively, while the corresponding drawing punches had diameters of 170.94, 122.43 and 99.31 mm respectively.

Sample D.

Blanks according to the preceding paragraph were placed in a press constructed according to the invention and having a set of three drawing punches. The cans were shaped with one continuous, uninterrupted stroke of the press, the speed of the stroke was approx. 15.24 m/minute. The drawing punch and die clearances and all structural and functional features of the present invention as stated above in the description were observed during this test. The objects showed no splitting or metal breakage and were otherwise completely satisfactory in terms of surface treatment, lack of surface defects and other qualities required in drawn metal objects for commercial purposes.

Sample D 31-

The procedure indicated under Sample D was modified in that the press was stopped at the completion of the first draw and the box removed from the first draw punch. Eighteen hours later, the box, in the same condition as when removed from the drawing punch, was placed on the first drawing punch and the working stroke of the press was continued so that the second and third drawing operations were completed. In each individual case, the box was split at the top of the box. The splits mostly occurred in the recess between lugs on the upper edge of the box and generally occurred at the time the box was removed from the drawing punch, indicating excessive work hardening with a resulting brittleness that could not withstand the action of the jaws on common wiper mechanisms.

Example 2.

The conditions were the same as stated in example 1 with the exception that the material tested was our low-carbon aluminium-damped steel instead of tensile quality steel.

Sample K 21.

The procedure was the same as in sample D in example 1 with the same result, namely no splitting or metal breakage.

Sample K 29.

The procedure was the same as for sample D 31 in example 1

and with the same result, namely that you got a split in the box.

Example 3.

The conditions were the same as stated in example 1, with the exception that the material was commercial grade low carbon steel.

Sample C.

The procedure was the same as in the case of sample D in example 1 and with the same result, namely no splitting or metal breakage.

Sample C 27.

The procedure was the same as in sample D 31 in example 1

and with the same result, namely splitting the box.

Example 4.

Trial operation was carried out on a press that had been constructed

according to the invention, and the press was one used in ordinary commercial production. In this press, the movable plate system comprised a set of five telescoping drawing punches having diameters of 33.56 cm, 27.18 cm, 21.52 cm, 16.51 cm and 13.21 cm for performing five draws and a smoothing operation which all were carried out within approx. 7 seconds during a 90-inch continuous, uninterrupted working stroke of the press.

The drawing dies which were placed on the fixed plate system in the press had clearances with the drawing stamps according to the principles of the invention, the radius in the first drawing die being 6.35 mm and the radii in the following four drawing dies being 7.938 mm. Fig. 21 shows the workpieces at the various stages in this particular sample, while fig. 22 and 23 indicate the pressure pattern obtained with the tool and material used in this sample.

The material used was Alcoa aluminum alloy 3003-0 (fully soft) in the form of 18.5 inch, pre-punched rondels from a 1.016 mm thick blank. In the smoothing operation which followed the fifth drawing and which took place on the 13.21 cm diameter drawing punch, the wall of the box was smoothed from a thickness of approx. 1.016 mm to a finished wall thickness of 0.686 mm. The finished box had an outer diameter of 13.18 cm and a height of 55.88 cm. All the jugs produced during this test were without breaks or splits, and they had an excellent surface free from defects of any kind.

When removing the cans from the press, the tops of the cans were trimmed lightly as needed to remove the ears at the top edge. the machinability of the box and trimmed line was such that a 3.175 mm diameter outside overbent edge was provided on the top of the box as a secondary operation by forming the trimmed top edge over 270° without causing fracture or cracking of the metal at any point and without annealing.

As they were removed from the press, the cans were tested to determine their dimensions and mechanical properties. The places on the boxes where the dimensions and mechanical properties were determined to create the following table are shown in the bottom illustration in fig. 21. A typical table of the dimensions and mechanical properties of these boxes was as follows:

Example 5-

This test was carried out on a press that was constructed according to the invention, the press being one that is used in regular, commercial production. The sets of five telescoping drawing punches had diameters of 33.56 cm, 27.18 cm, 21.59 cm, 16.51 cm and 11.43 cm with a drawing die of 6.35 mm radius: the second, third and fourth draw dies each had a diameter of 7.938 mm, and the fifth draw die had a radius of 9.525 mm. The material in this sample was the same as in Example 4, except that the thickness of the blank was 1.27 mm. The smoothing operation was performed on the 11.43 cm drawing punch after the fifth drawing operation and reduced the wall thickness of the finished box to 1.016 mm.

The 58.42 cm diameter pre-punched rondels of 3003-0 aluminum alloy (fully soft) were placed in the press and drawn and smoothed in a continuous, uninterrupted operation to produce finished cans having a diameter of lls53 cm and a height of 96.52 cm. The total reduction during five pulling operations was somewhat more than 80%. It should be noted that the ratio between the diameter. and the height of the boxes that were frozen in this way was approx. 1-8. Boxes produced in this test had no breaks or splits of any kind and had the same faoyt machined excellent surface properties and available machinability301a indicated in example 4. The speed of the working stroke in the press was approx. 21s34 say per minute, and the clearance between draw piston and die was as described above.

Example 6. x

This test was carried out under the same conditions as in example 5, using the same tensile tests and tests and the only deviation was that Alcoa all-metal alloy 3003-H19 (fully hard) was used instead of aluminum alloy 3< 303~G (little soft). The results obtained in this test were the same as those stated in Example 4 in terms of lack of breakage or splitting. If there was a difference, the surface treatment was better and the workability after the box was removed from the press without annealing allowed rolling of the same edge mentioned in Example 4 with the same excellent results. These results with hard material were completely unexpected and cannot be explained on the basis of common commercial practice. When checking the mechanical properties of the boxes that were produced during this test of 3003-H19 aluminum alloy, it was found that the bottom of the box as indicated in fig. 21 had retained its full hardness, and the walls of the box had more than full hardness. A tabulation of the mechanical properties of a typical box produced in this test was as follows:

Until now, it has been considered commercially impossible to deep draw completely hard material. The advantages of doing this are obvious from the table above, which indicates that the mechanical properties of the deep-drawn object are largely the same over the whole of the drawn bottom and the drawn side walls. The results indicated by means of example 6 represent a great advantage in the gravure art, especially when it comes to the production of metal printing vessels.

Example 7.

In an attempt to determine the upper limits of the machinability improvement in drawn and smoothed metal objects produced with the new press, the tool used in the press in the test example'5> was modified to allow the use of sheet material with 2.54 mm thickness. This was achieved by using the same drawing stamps as indicated in example 5 and inserting larger matrices in the drawing steps. The smooth die in Example 5 was enlarged to reduce the wall thickness of the article to 1.52 mm, and another smooth die was added to reduce the wall in the finished article to 1.016 mm.

As in example 5, the material was drawn and smoothed

3003-0 (fully soft) aluminum alloy, and the workpiece diameter was 58.42 cm. Without removing the workpiece from the telescoping drawing punch assembly and without annealing or resorting to other forms of conventional devices hitherto used to restore workability after work hardening, it was possible to draw and smooth the 58.42 cm diameter workpiece into a finished box which had an internal diameter of II.43 cm and a total length of 167.64 cm with no metal breakage or splitting of any kind. The quality of the surface treatment and lack of surface defects was the same as found in example 5. The speed of the press stroke and the radii in the dies were as indicated in example 5-

A box shaped as described in the previous section was cut lengthwise and Rockwell readings taken on a 30-T scale with a load of 30 kg, using a 1.588 mm ball. Starting 101.6 mm from the bottom of the box, readings were taken at 101.6 mm intervals, the last reading being taken 50.8 mm from the open top of the box. The readings were as follows: 26, 28, 27.5, 27.5, 28.5, 29, 30, 29, 30, 28, 28, 29.5, 30, 30, 30 and 31. While in example 5 the ratio between the diameter and height of the drawn and smoothed box was approx. 1-8, this ratio in example 7 was increased to approx. 1-15 without metal breakage or splitting. After it had been drawn and smoothed, the object had such machinability that the upper limits for machinability in material as stated in example 7 had clearly not been reached.

Although it is assumed that means other than liquid pressure can be used to drive the pressure piston 150, the pressure piston 115 in the commercial form of the invention is a direct extension of a piston 156 (fig. 20) which is located in a cylinder 158 whose length determines the pressure piston 150 maximum strokes. Preferably, the fluid pressure directed against the piston 156 during the working stroke of the press is of a pulsating nature, whereby the pressure piston 150 and the plates in the movable plate system transmit high-frequency fluid impulses to the drawing pistons during the working stroke of the press.

In a real case, the liquid pressure which is to produce the working stroke of the press through movement of the pressure piston 150 can be provided with the help of the pumps 160 and 162. The pumps are of the axial piston type, where one or more axial pistons provide positive displacement of the liquid for each rotation of the pump.

In these pumps, each piston will give a pressure impulse for each rotation. Pumps of this type are, when they are precompressed, such as e.g. the pump 164 is designed so that they can work at 1800 revolutions per minute. In general, these pumps have several axial pistons, and those used in the press have seven axial pistons and are capable of delivering 351.5 kg/cm at 189.25 l/minute and 378.5 l/minute respectively. To analyze the pressure pattern during the "impact" of the press, see fig. 22 and 23, a high-speed electronic analy-

o

sator which transferred the output of a pressure build-up to vertical deflection on a cathode ray oscilloscope. To bring out the pressure pattern in fig. 22 and 23, the pressure recording was subjected to the fluid pressure acting on the piston 156 of the pressure piston 50. Fig. 22 is a representation of the curve drawn on the screen in the cathode ray tube during the complete working stroke of the press when equipped with tools to produce the drawn and smoothed object which is depicted in order of manufacture in fig. 21 and described under example 4.

Reference is made to fig. 22 where the working stroke of the press was completed in seven seconds. The pressure pattern indicates the pressure peak d in the first draw to be approx. 133.57 kg/cm p acting against the pressure piston 150. The next tensile pressure peak rd indicates a corresponding maximum pressure. It should be noted that both tripping peaks occurred within the first second of the press's operation. This indicates a relatively shallow first draw, which can be seen from fig. 21 where the sheet metal strip S is reduced so that it forms the workpiece B. Between the pressure peak rd of approx. 133.57 kg/cm 2 in the second pulling operation, and the pressure peak rd2 of approx. 123.03 kg/cm 2 in the third pulling operation, a larger time interval is specified than between the pressure peaks d and rd. This suggests an elongation of the object that takes place during the second draw, which is evident from the shape of the workpiece Bl in fig. 21.

Fig. 22 shows that the pressure peaks rd2 and rd3 at the third and fourth draw respectively took place at approx. 123 kg/cm 2 pressure. The time interval between each of the adjacent maximum pressure peaks for the pulling operations is shown as progressively increasing, which suggests the progressive elongation of the object, bearing in mind that it is desirable<*>to delay the start of a pulling operation until the previous one, is finished. It is also desirable to avoid delay in the subsequent pulling operation when the previous pulling operation has been completed.

Doing otherwise will necessarily extend the length of the press unnecessarily. In fig. 21, the workpiece b has assumed the form Bl, B2, B3 and B4

respectively at the end of the second, third, fourth and fifth pulling operation.

The smoothing operation is indicated by i in the pressure pattern in fig.22 and takes place at a pressure of approx. 53 kg/cm 2. At the completion of the smoothing operation, the pressure drops to approx. 35 kg/cm 2 , as indicated at C with a maximum pressure peak for the entire "down" cycle in the press of approx. 171 kg/cm 2 at which time the bottom of the object is detailed at the end of the "down" stroke. After the smoothing operation, the workpiece B has assumed the shape B5 in fig. 21.

In both Figures 22 and 23, the pressure pulses 166 are indicated between the pressure peaks. In these figures, no attempt has been made to depict the frequency of these impulses, although this can be determined using the electronic analysis device mentioned above. During the tests carried out on presses with pumps of the type described above, impulses with a frequency of 60 cycles per second were present. second or more, which was indicated on the pressure pattern in the form of a band having a width which depicted amplitudes covering a pressure range of the order of 14 kg.

Reference is made to fig. 23 which is an enlargement of the upper left corner in fig. 22. The frequency of the pressure impulses which make up the wide band in the marked pressure pattern during the "down" stroke of the press, is determined by the construction of the pumps used in the hydraulic system to operate the pressure piston, and the speed at which the pumps are operated. These impulses are transferred to the pressure piston 150 and from there to the plates and tension pistons in the movable plate system in the press, the transmission of the impulses between the adjacent plates going through the hydraulic cushions as well as through the tension pistons which are arranged inside each other.

Although it is one of the theories of the present invention that the high-frequency impulses that are transmitted to the metal-shaped components in the press constitute one of the many factors that ensure the unexpected results of the present invention, acceptable, commercial results have nevertheless been obtained during experiments where a accumulator was attached to the hydraulic system of the pressure piston in a deliberate attempt to reduce the size of these impulses. Those skilled in the art will understand, by studying and comparing the pressure patterns depicted in FIG. 22, which pressure patterns apply to different materials that are run through the press and under different control conditions, that the pressure patterns will be useful during control and operation of the press of the invention in commercial use.

To determine the extent to which the pressure impulses on the pressure piston 50 are transmitted to the press structure in the vicinity of the draw pistons, the pressure recorder in the electronic analyzer mentioned above was moved to the fluid system in the hydraulic pads 56 in the plate 34. The pressure patterns taken at this location were very similar to those shown in fig. 22 and 23, and the width of the drawn pressure pattern clearly indicated that impulses 166 were present with approximately the same frequency and magnitude as those found when the recorder was placed in the hydraulic pressure system in the pressure piston 150.

When the press was operated without any material being drawn or smoothed, but otherwise under operating conditions which were the same as those prevailing when the pressure patterns in fig. 22 and 23 appeared, it was found that the marked maximum pressure peaks were slightly lower. On average, the maximum pressure peaks in the pressure pattern covering a complete "down" stroke of the press without a material being formed were less than 7 kg below the maximum pressure peaks when the material was formed.

The low strain response of the metal in the workpiece B against the drawing and smoothing operations as indicated in the previous paragraphs is believed to indicate a softening of the metal as a result of two phenomena which have a cumulative effect and which provide a possible explanation for the unusual results that have achieved with the present invention which confirmed e.g. in the preceding examples 6 and 7•

A phenomenon which may be the cause of the apparently low load yielding to the metal in workpiece B is a softening effect produced by the high-frequency vibration. When drawn metal has been exposed to the action of a macrosonic vibrator, one explanation for the softening effect is that the grain boundaries absorb sufficient energy due to inelastic scattering of ultrasonic waves that the scattered atoms approach melting temperatures within milliseconds, so that the forces which are necessary to move them, is suddenly reduced.

Another phenomenon which is also believed to cause the low load response in the metal to deformation is that the deformation of the metal in the work piece B is carried out during a single continuous, uninterrupted, fast stroke of the press without significant spreading of the internal, unfolding of the hot between the deformations.

It appears that the combination of the high-frequency pulsation of the tool in a deep-drawing press with successive deformation of metal in a rapid continuous, uninterrupted stroke of the press has not been thought of before, and that the improved results of this have not been anticipated either. .

As mentioned above, many factors contribute to the achievement of the good results. P. e.g. it has been established that the guiding of the workpiece B from one drawing punch to the other during the repeated drawing operations is very important especially when it comes to forming high strength alloys. To do full justice to this fact, the reduction that takes place in the first draw matrix is preferably less than what has hitherto been considered good practice. This deviation from standard practice has been done to increase the reduction amounts that take place after the first pulling operation during the repeated pulling operations.

When using the new press, where the pressure patterns in fig. 22 and 23 were taken, a 400 hp electric motor was used to drive two axial piston type pumps having capacities of 189.25 l/min and 378.5 l/min at 351»5 kg/cm 2 at 1750 rpm. minute. The fluid pressure provided was transferred to a cylinder having an internal diameter of 152.4 mm, and against the piston which was directly connected to the impact piston of the press. By replacing the pumps mentioned in the previous section with a gear pump of 567.75 l/minute, but with a lower pressure capacity, the costs of the hydraulic pressure system in the pressure piston can be greatly reduced. However, if this replacement is made, some of the benefits of the high-frequency vibrations in the liquid pressure system produced by the axial piston pumps will be sacrificed. In such a case, one can imagine the use of a transmission system that corrects vibrations and which acts directly on one or both of the hydraulic systems in the press in order to correct a low-load response in the workpiece against deformation in the press. For example hydraulic vibrators of the type currently used commercially to test fatigue failure in materials can be connected to the press to provide vibrations up to 500 cycles per second compared to the pressure pulses of 200 cycles/second which can be obtained by means of one or more axial piston type pumps having seven pistons and operating at 1750 revolutions per second. minute.

In addition to the improvements achieved by total reduction of the workpiece when machined without intermediate annealing, many other financial savings have been achieved. By e.g. to carry out several operations during a continuous, uninterrupted stroke of the press, is handling, cleaning and lubrication of the workpiece between

operations avoided. When comparing the tool costs of

a metal object drawn in the usual way, with the tooling costs for the same object, produced in the new press, the tooling costs for the latter are considerably less and savings of up to 50% are not unusual.

It will be understood that the present invention is not limited to the production of sleeves, boxes, pipes or the like with a round cross-section. Metal objects with other shapes can also be produced. Furthermore, it has been assumed that the total length of the press can be reduced by having some or all of the plates in the fixed plate system moveable in relation to the draw stamps on the plates in the movable plate system. Presses constructed as described above have a very wide range of applicability. By changing the length of the spacers 40 by a few hundredths of a millimetre, the result will be a thicker or a thinner wall in the finished workpiece. For example a change in the length of a spacer 40 of 0.254 mm will cause a change in the wall thickness of 0.054 - 0.0508 mm. The length of a workpiece can be increased without changing the drawing punches and dies, by increasing the diameter of the workpiece size and changing the length of the spacers 98 of the plates in the fixed plate system, whereby one operation is completed before the next operation begins. To process material of this thickness, only the drawing dies need to be replaced. When changing from one material to another of the same thickness, only the holding pressure on the surface of the drawing dies needs to be regulated, and this can be done by simply turning the knobs 144.

During commercial deep drawing of a metal part, where the part is transferred from a die in one press to a die in another press, and an annealing operation is performed between the drawing operations, it is often necessary to trim the part between the drawing operations. Trimming the part is an additional operation, and it also increases the blank size needed to produce the finished drawn part. In the new press, all trimming operations between the drawing operations are avoided and as a result it allows the use of a minimum blank size.

Claims (4)

1. Deep drawing press, comprising a larger drawing die (106), an outer drawing punch (74) for drawing the workpiece in the larger drawing die, a smaller drawing die (110), an inner drawing punch (72) for drawing the workpiece in the smaller drawing die, which dies and punches are all mutually aligned and designed for pulling the workpiece through the dies with one working stroke of the press, the inner drawing punch (72) has a telescopic guide in the outer drawing punch (74) and lies inside this during pulling in the larger drawing die (106 ), and the end (84) of the outer drawing piston (74) and a surface (111) on the smaller drawing matrix (110) form mutually opposing surface parts, characterized by a spacer (40) which holds the said surface parts (111 and 84) in a mutual distance corresponding to the wall thickness of the workpiece (B), whereby an abutment retention of the workpiece is provided, by means of pressure that acts on the aforementioned outer pulling piston (74) and is counteracted by the spacers (40), whereby a pressure retention of the workpiece is provided, and by means of regulation (52 , 54, 56) for controlling the relative movement of the pulling pistons, whereby the inner pulling piston (72) is pushed out of the outer pulling piston (74) and a the workpiece (B) is drawn between the two mentioned surface parts (111 and 84) and through the smaller drawing matrix (110). 2. Deep drawing press according to claim 1, characterized in that the drawing punches and the larger drawing matrix are carried by separate, relative to each other movable plate members (30, 32 and 88) in which the spacers (40) are carried by one plate member and are arranged between the plate members, whereby a stop construction is provided for limiting the relative approaching movement of the plate members, and by a device (90) for supporting the smaller drawing matrix (110) in a fixed spaced position relative to the larger drawing matrix (106). 3. Deep drawing press according to claim 1 or 2, characterized in that the spacers (40) are made as stop pieces distributed around the longitudinal axis through the drawing dies and the drawing punches. 4. Deep drawing press according to one of the preceding claims, characterized in that the regulating means comprise hydraulic dampers (52, 54, 56) arranged between adjacent plate means for controlling the advancement of the inner drawing piston (72).