US3664785A

US3664785A - Presses for production of complex components

Info

Publication number: US3664785A
Application number: US883032A
Authority: US
Inventors: Alec Frank Marshall; Hugh Gordon Taylor
Original assignee: Birmingham Small Arms Co Ltd
Current assignee: Birmingham Small Arms Co Ltd
Priority date: 1968-12-13
Filing date: 1969-12-09
Publication date: 1972-05-23
Anticipated expiration: 1989-05-23
Also published as: GB1242259A; DE1962420A1

Abstract

A TOOL FOR A HIGH ENERGY RATE MACHINE FOR THE PRODUCTION OF COMPACTS OF METAL POWDERS OF TWO OR MORE SECTIONS OF DIFFERENT THICKNESS IN LINE OF PRESSURE COMPRISES AN UPPER PUNCH FIXED TO A RECIPROCAL MACHINE RAM, A DIE HAVING A BORE DEFINING THE PERIPHERY OF THE CAMPACT TO BE PRODUCED, A FIXED LOWER PUNCH AND A MOVABLE FLANGE PUNCH DISPOSED WITHIN THE BORE AND FORMING TOGETHER A LOWER CLOSURE FOR THE BORE, A FLANGE PUNCH PISTON FIXED TO THE FLANGE PUNCH HAVING UPWARDLY AND DOWNWARDLY FACING SURFACE, MEANS FOR SUPPLYING FLUID PRESSURE TO THE DOWNWARDLY FACING SURFACE TO HOLD THE FLANGE PUNCH IN AN UPPER POSITION PRIOR TO COMPACTION OF POWDER CONTAINED WITHIN THE DIE, AND MEANS FOR SUPPLYING FLUID PRESSURE TO THE UPWARDLY FACING SURFACE TO MOVE THE FLANGE PUNCH PISTON DOWNWARDLY DURING COMPACTION OF THE POWDER BY THE UPPER PUNCH.

Description

y 1972 A. F. MARSHALL ET AL 3,664,785

I PRESSES FOR PRODUCTION OF COMPLEX COMPONENTS 4 Sheets-Sheet 1 Filed Dec. 9, 1969 Inventors ALEC FRANK MARSHALL and HUGH GOR N TAYLOR Attorneys 7 1772 mCLl/\ May 23, 1972 AR HA L 'ET AL 3,664,785

PRESSES FOR PRODUCTION OF COMPLEX COMPONENTS Filed Dec. 9, 1969 4 Sheets-Sheet 2 Inventors ALEC FRANK MARSHALL and HUGH GORDON TAYLOR Attorneys ,y r I #4111 1 Edam/wav y 23, 1972 A. F. MARSHALL ETAL 3,664,785

IRESSES FOR LRODUCILON 01" COMPLEX COMPONENTS Filed Dec. 9, 1969 4 Sheets-Sheet 3 Inventors ALEC FRANK MARSHALL and HUGH'GORDON TAYLOR Attorneys )2QAAA) 1 y 23, 1972 A. F. MARSHALL ETAL 3,664,785

PRESSES FOR PRODUCTION OF COMPLEX COMPONENTS Filed Dec. 9, 1969 4 SheetsSheet 4 Inventors ALEC FRANK MARSHALL and HUGH GORDON TAYLOR Attorneys United States Patent 3,664,785 PRESSES FOR PRODUCTION OF COMPLEX COMPONENTS Alec Frank Marshall, Solihull, and Hugh Gordon Taylor, Birmingham, England, assignors to The Birmingham Small Arms Company Limited, Birmingham, England Filed Dec. 9, 1969, Ser. No. 883,032 Claims priority, application Great Britain, Dec. 13, 1968, 59,300/ 68 Int. Cl. B29c 3/00 US. Cl. 425-78 12 Claims ABSTRACT OF THE DISCLOSURE A tool for a high energy rate machine for the production of compacts of metal powders of two or more sections of different thickness in line of pressure comprises an upper punch fixed to a reciprocal machine ram, a. die having a bore defining the periphery of the compact to be produced, a fixed lower punch and a movable flange punch disposed within the bore and forming together a lower closure for the bore, a flange punch piston fixed to the flange punch having upwardly and downwardly facing surfaces, means for supplying fluid pressure to the downwardly facing surface to hold the flange punch in an upper position prior to compaction of powder contained within the die, and means for supplying fluid pressure to the upwardly facing surface to move the flange punch piston downwardly during compaction of the powder by the upper punch.

This invention relates to the production of shaped compacts of metal and other powders (hereinafter referred to generically as metal powders) which are subsequently sintered to form finished or semi-finished components. The methods of producing these, involving presses, usually hydraulic, in which the powder is compacted in a die, are well known. The increasing demand for larger components and higher densities has led to the experimental use of high energy rate forging presses adapted for compacting metal powders. These presses, which usually have ram velocities up to 60 feet per second, have the advantage of higher ratio of energy to press weight than conventional presses. While the production of simple, single thickness components presents no major difliculties, more complex components, and in particular components with two or more sections of difierent thickness in the line of pressure, involve problems which, so far as we are aware, have hitherto prevented the successful use of the high energy rate method.

When suitable powders are pressed in a die between punches their flow and pressure characteristic are not of a hydraulic character as is basically the case in the various techniques for forming solid articles. In practice the powder compresses almost entirely vertically and only moves laterally to a minor degree. For this reason the height of loose powder over each diflerent section thickness must initially be substantially in proportion to the final dimensions of the compacted powders. From this it follows that separate elements of tooling must be used for each different thickness of section and that each element must be moved (relatively to other parts of the tooling) the correct distance. Thus (assuming the compact to be produced vertically with a single upper punch) the tooling of a component with two sections of diiferent thickness (for example, a boss with a flange) would require two lower punches and one upper punch, the lower punches having between them relative movement between the initial filling position and the final compacted position. The die, which forms the outer periphery of the compact, also usually moves relatively to the lower punches to minimise friction between the die and the powder and the same applies to the core rod if one is used to form a hole in the component.

For convenience the lower punch which forms the lower face of the greatest compact section thickness will be referred to as the fixed punch and the other lower punch as the flange punch.

When the operating ram or piston carries the upper punch downwards at high velocity it first begins to compact the powder lying between the upper punch and the flange punch. Pressure transmitted from the upper punch through the powder then accelerates the flange punch downwards very rapidly.

As the powder ideally should be increased in density at an equal rate in both flange and boss sections, it IS essential that the resistance of the flange punch and its supporting medium should be limited,to prevent overdensification of the flange in the initial stages of compaction.

If the supporting medium is just sufficient to support the weight of the punch, the resistance provided by the punch becomes a function its weight and acceleration.

These conditions demand a flange punch unit of minimum weight which at the same time must be strong enough to withstand the final pressure of compaction after it has moved downwards from the fill position to the final compacting position.

The thicker, boss section of the compact is compacted simultaneously with the flange. The increasing density in the boss increases the friction between powder and tool in the bore of the flange punch. The upper punch velocity also decreases as its energy is expended in densifying the powder. The increasing friction will decelerate the flange punch considerably before it reaches the final compacting position.

In one proposal for a high energy rate machine designed for compacting metal powders the flange punch is supported by a bar which floats on two pneumatic pistons. Due to the extremely rapid downward acceleration of the flange punch the bar is subjected to considerable bending stress. In addition the weight of the moving parts is such that the combined inertia of the flange punch, bar and pistons is great relative to the appropriate range of flange punch areas.

One of the objects of the present invention is to provide a construction in which the support for the flange punch is not subjected to considerable bending stress. A further object is to provide a construction in'which the inertia of the flange punch and piston is reduced, thereby permitting a design which more nearly provides the correct pressure to the powder during the initial stages of compaction.

According to the invention a tool for use in conjunction with a high energy rate machine for the production of compacts of metal and other powders of two or more sections of different thickness in line of pressure comprises an upper punch aflixed to a reciprocal ram of the machine, a die having a bore therethrough defining the periphery of the compact to be produced, a fixed lower punch, a movable flange punch, said lower fixed punch and movable flange punch being disposed within the bore and forming together a lower closure thereof, a flange punch piston aflixed to the movable flange punch having upwardly and downwardly facing surfaces, means for supplying fluid pressure to the downwardly facing surface to hold the flange punch in an upper position prior to compaction of powder contained within the die, and means for supplying fluid pressure to the upwardly facing surface to move the flange punch piston downwardlyduring compaction of the powder by the upper punch.

The piston is preferably of circular or annular crosssection arranged to move in a pneumatic or hydraulic cylinder.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which like reference numbers indicate like parts, and in which:

FIG. 1 is a cross-section through a tool of the kind referred to illustrating the relative movements of the component parts thereof,

FIG. 2 is a cross-section through a tool according to the invention,

FIG. 3 is a cross-section through a tool according to the invention showing a means of actuating the flange punch support piston by the machine ram,

[FIG. 4 is a cross-section through a valve adapted to control the actuation of the flange punch support piston,

FIG. 5 is a cross-section through a tool according to the invention showing an alternative flange punch support piston,

FIG. 6 is a cross-section through a tool of the kind referred to adapted to produce a compact of three different sections, and

FIG. 7 is a cross-section through a tool of the kin referred to in which the positions of the flange and fixed punches are reversed to produce an alternative shape compact.

FIG. 1 illustrates the essential components of an exemplary tool of the kind referred to and the relative movements of said components; the cross-section to the right of the centre line showing the position of the components at the instant when compaction is about to start and the cross-section to the left of their positions when compaction is complete, A die 1 defines the outer periphery of the compact to be produced and has disposed concentrically therein a flange punch 2, a fixed punch 3 and a core rod 4. The space 5 is filled with the metal powder which is to be compacted to form an article which, in this case, is of annular shape with a central boss. The compaction of the powder is accomplished by the upper punch 7 which is aflixed to the ram of a high energy rate compaction machine as shown at 20 in FIG. 3. The final positions of the various components of the tool reveal that only the fixed punch has remained stationary, all other components having moved downwards, that is in the direction of compaction, in varying degrees. The upper punch 7 and the flange punch 2 have moved to positions which, together with fixed punch 3, define the required cross-section 6 of the final article. The die 1 and the core rod 4 have moved in order to minimise the friction between them and the powder during the compaction operation.

Referring in particular to the three

punches

2, 3 and 7, the flange punch 2 moves the distance B, the upper punch 7 moves the distance A whilst the fixed punch 3 has remained stationary. The overall height of the powder is compacted from E to C and the height of the powder forming the boss from F to D by the relative movement of the punches. As has been hereinbefore mentioned, powder compaction machines of all types result in compaction which is almost entirely vertical with little or no lateral movement of powder and, because it is preferable to have an equal degree of compaction throughout the powder, therefore, the distance B moved by the flange punch 2 is such that the ratio C:E is equal to the ratio DzF. Expressed another way D =xF and Cl=xE where x is the compression ratio of the powder.

FIG. 2 illustrates a tool according to the invention and again the cross-section to the right of the centre line shows the components thereof before compaction and the cross-section to be left after compaction. The flange punch 2 abuts and is preferably affixed to piston 8 which is slideably mounted on the fixed punch 3 and is adapted to move in cylinder 10 in the member 9 which is stationary with reference to the fixed punch 3. The piston 8 may be held in its uppermost position in which the flange punch is in the pre-compaction position by the action of a fluid in the chamber 11 formed by the cylinder 10 and the underside of the piston 8, the fluid being supplied at a pressure just sufficient to hold the piston 8 and the flange punch 2 in said uppermost position. The bottom face 12 of the cylinder acts as a stop to define the lowermost position of the piston to which it is moved during the compaction operation. The downward movement of the piston is effected by the application of fluid pressure to an upwardly facing surface thereof, as will be described in greater detail with reference to the embodiments of the invention hereinafter described.

As the piston 8 is subjected only to compressive stress it can be made from relatively light metal, for example, aluminium alloy or plastics, which may be reinforced if necessary.

In the embodiment shown in FIG. 3 the piston 8 has an upward facing shoulder 13 which does not abut the upper face 14 of the cylinder 10 when the piston is in its uppermost position and therefore forms annular chamber 15. The chamber 15 communicates through passage 16 with cylinder 17 in which operates the acceleration piston 18. An arm 19 attached to the ram 20 of the machine, carries plunger 21 which is adapted to engage the acceleration piston 18 when the upper punch 7 approaches the die. A resilient cushion 22 positioned within the recess 23 in the top face of piston 18 acts as a shock absorber and enables the acceleration piston to be smoothly accelerated from rest by the plunger 21.

The operation of the flange piston acceleration means is as follows. The plunger 21 on the descending ram 20 contacts the buffer 22 just before the upper punch 7 contacts the powder and distorts it to fill the recess 23 providing increasing resistance suflicient to begin the downward movement of the acceleration piston 18. As the acceleration piston 18 moves downwards it increases the pressure of the fluid contained within the cylinder 17, the passage 16 and the annular chamber 15 and thus exerts a downward force on the shoulder 13 of the piston 8 which is accelerated downwards. The area of the acceleration piston is less than the area of the shoulder 13 and therefore piston 8 travels at a speed less than that of the piston 18 and hence the ram 20. The upper punch therefore approaches the descending flange punch but at a reduced velocity.

The powder between the upper punch 7 and the flange punch 2 is by this means subjected to a greatly reduced pressure in the initial stages of compacting. As the upper punch 7 compresses the powder over the flange punch 2 it exerts a force therethrough which eventually accelerates the flange punch to a velocity virtually equal to that of the upper punch 7. Fluid is then drawn into the chamber 15 at a greater rate than it is supplied by the acceleration piston which therefore accelerates to a speed greater than that of the plunger 21 allowing the buffer 22 to expand and maintain contact with the plunger 21.

The above described flange punch accelerating means ensures that there is no over-densification of the flange during the initial stages of compaction and enables the density of the flange and boss sections to increase at an equal rate. Control of the timing of the flange punch acceleration can be arranged by vertical adjustment of the plunger in such a manner that compaction of the flange can be delayed or advanced relative to the compaction of the boss.

The fluid pressure need not be exerted directly by the ram but can be supplied by a separate source controlled by a ram actuated valve. FIG. 4 shows a suitable ram operated piston valve.

The piston valve 24 is actuated by a plunger 21 attached to the ram through intermediate buffer 25 in a similar manner to acceleration piston shown in FIG. 3. The bore 26 in which the piston 24 is slideably located has

ports

27, 28 and 29 separated by lands 30 and 31 respectively. Port 27 communicates through inlet passage 32 with a fluid pressure source (not shown) which has accumulator 33 in conventional manner. Port 28 communicates through outlet passage 34 with the flange piston and port 39' communicates with pressure relief passage 35. The piston flange 36.normally lies on land 30 but when the piston 24'is moved downwards by plunger 21 against the action of spring 37 it passes port 28 and allows the fluid pressure source to communicate with the flange piston chamber thus accelerating the flange piston. When the plunger 21 is moved upwardly after the compacting stroke the piston 24 moves under the action of spring 37 and the piston flange 36 moves from land 31 to land 30 allowing the flange punch chamber to communicate with the relief outlet 35 enabling the flange punch piston to be returned to its initial position.

The advantage of this method of accelerating the flange punch is that the energy taken from the ram is only that required to operate the valve, the energy required to accelerate the flange punch being taken from a separate source. While the timing of the acceleration of the flange punch and piston is controlled as before by the ram plunger, the'rate of acceleration in this alternative design is dependent upon the fluid pressure. Other types of valve could be employed, for instance, sleeve, poppet or rotary valves, but it is preferred to use a piston valve of the type as described above.

In a still further embodiment of the invention shown in FIG. the timing of the acceleration of the flange punch and piston is controlled directly by the upper punch and not by a plunger attached to the ram.

The flange punch piston 8 has an upward facing shoulder 41 forming the small annular chamber 38. Chamber 38 is fed with fluid at a relatively high pressure through inlet passage 39 and the chamber 11 below the flange punch piston is fed with fluid at a relatively low pressure through inlet passage 40. The areas of the underside of the piston 8 and the shoulder 41 are such that upward force exceeds the downward force by a margin suflicient to maintain the piston in its uppermost position, as shown.

When the descending upper punch 7 contacts the powder to be compacted it transmits a force therethrough which is suflicient to move the flange punch 2 and the flange punch piston 8. This movement of the flange punch piston 8 exposes the shoulder 42 to the high pressure fluid and the greatly increased high pressure area so formed causes the piston 8 to be accelerated downwards, just as the upper punch begins to compact the powder over the flange punch 2. The acceleration will depend upon the inertia of the moving parts and the force applied by the high pressure fluid. The maximum velocity of the piston 8 can be controlled by the increase in pressure on the low pressure area and the drop in pressure on the high pressure area.

When the compacting is complete, the flange punch piston 8 is returned to its upper position by increasing the pressure in chamber 11 below the piston, or by other means. A seal 43 is preferably located in the face of shoulder 42 eflectively sealing off its area from the action of the high pressure fluid when the piston 8 is in its uppermost position.

As an alternative to initiation of the downwards acceleration of the flange punch piston by the upper punch, the piston area inside the seal 43 may be given an impulse of high pressure fluid as through conduit 40'.

The flange punch systems in all the above described embodiments are, of course, applicable to the use of more than one moving lower punch, where components of three or more thicknesses are to be produced.

Control of the relative movement of the die 1 and the core rod 4 during compacting is not normally as critical as in the case of the flange punch, and their acceleration rates are normally lower, but the control systems specified herein are also applicable to the die 1 and the core rod 4. In certain types of component the die 1 and the core rod 4 may have shoulders 44 and 45 respectively, FIG. 6, to produce change of section on the component. In such cases the die 1 and core rod 4 move in an identical manner to the flange punch 2, and the control systems specified herein are then directly applicable to die and core rod movements.

The term flange punch is used for convenience in describing the punch which forms the underside of the thinner section of a two-section component and should also be understood to apply to a similar moving punch with any other component shape. For instance reversal of the positions of the flange and fixed punches as shown in FIG. 1 would enable an annular cup-shape component to be produced, as shown in FIG. 7.

The invention may be used in association with the invention described in our U.S. application Ser. No. 883,- 405, filed Dec. 9, 1969.

What we claim is:

1. A tool for use in conjunction with a high energy rate machine for the production of compacts of metal and other powders of two or more sections of different thickness in line of pressure comprising a ram actuated upper punch mounted for reciprocal upward and downward movement, a die having a bore therethrough defining the outer periphery of a compact to be produced, a fixed lower punch, a movable flange punch, said fixed lower punch and the movable flange punch being disposed within said bore and forming together a lower closure for said bore, a flange punch piston disposed in solid motion transmitting association with said flange punch and having upward and downwardly facing surfaces, means for supplying fluid pressure to the downwardly facing piston surface to hold the flange punch in an upper position prior to compaction of powder contained in the die bore, and means for supplying fluid pressure to the upwardly facing piston surface to move said piston and flange punch downwardly during compaction of powder in said bore by downward movement of said upper punch.

2. A tool according to claim 1 wherein the means for supplying fluid pressure to the upwardly facing surface of the flange punch piston comprises a piston reciprocable in a cylinder in fluid communication with said upwardly facing surface and a plunger affixed to the ram of the machine arranged to contact and actuate said piston as the ram moves downwardly.

3. A tool according to claim 1 wherein the means for supplying fluid pressure to an upwardly facing surface of the flange punch piston comprises a source of fluid pressure, a passage communicating between said source of fluid pressure and the upwardly facing surface of the flange punch piston, a valve normally closing said passage, and a plunger carried 'by the ram of the machine arranged to contact and open said valve as the ram moves downwardly.

4. A tool according to claim 1 wherein an upwardly facing surface of the flange punch piston carries means providing a seal isolating said surface from a source of fluid pressure when the flange punch piston is in an uppermost position, means being provided to initiate downward movement of the flange punch piston, breaking the seal and exposing the upwardly facing surface to the source of fluid pressure.

5. A tool according to claim 4 wherein the means for initiating downward movement of the flange punch piston is the ram of the machine acting through the powder contained within the die.

6. A tool according to claim 4 wherein the means for initiating downward movement of the flange punch piston is a means of appling a pulse of fluid pressure to the upwardly facing surface thereof.

7. A tool according to claim 1 wherein said flange punch piston is fixed to the flange punch and is slida'bly disposed within a cylinder that is stationary relative to the fixed punch.

8. A tool according to claim 1 wherein said means for supplying fluid pressure to said upwardly facing surface is adapted to at least initially accelerate the flange punch downwards during the compaction operation.

9. A tool according to claim 1 wherein the fluid pressure applied to the upper surface of the flange punch piston is derived from a source independent of the ram action of the machine.

10. A tool according to claim 9 wherein a passage between the independent source of fluid pressure and the flange punch piston is normally closed by a valve disposed to be opened by a plunger rigid with the ram of the machine.

11. A tool according to claim 1 wherein said flange punch piston has two upwardly facing surface regions one of which is of substantially smaller area than the other and said means for supplying fluid pressure to said upwardly facing surface is connected to a source of relatively high fluid pressure, said larger area region being connected with said source only after initial downward movement of the said piston, and said means for supplying fluid pressure to said downwardly facing surface of the piston is connected to a source of relatively low fluid pressure, the relationship between the area of the smaller upper surface region and the area of the downwardly facing surface of the piston being such that when the piston is in its uppermost position the upward force on References Cited UNITED STATES PATENTS 2,509,783 5/1950 Richardson 18 16.7 2,562,876 8/1951 Baeza 18 16.5 2,810,929 10/1957 Willi 18-167 2,821,748 2/1958 Willi 18--16.7 3,164,812 11/1964 Haller 25',91,X 3,337,916 8/1967 Smith 18-16 .7 3,524,220 8/ 1970 Davison 1816.7

I. SPENCER OVERHOLSER, Primary Examiner B. D. TOBOR, Assistant Examiner