GB2174324A - Forging press - Google Patents

Abstract

A mechanical crank forging press has a top ram (10) carrying an upper tool (12) reciprocable towards and away from a lower tool (14) itself mounted on an annular piston (24) within an hydraulic cylinder (26). A punch- carrying piston (28) extends upwardly through the annular tool-carrying piston (24) and carries a punch (30) at its upper end projecting into a die cavity within the lower tool (14). Downward movement of the top ram (10) brings the upper and lower tools into contact and displaces the tool-carrying piston (24) into the hydraulic cylinder (26) to expel the punch-carrying piston (28) upwardly and outwardly therefrom thus actuating an upward forging stroke of the punch (30) into the closed die cavity. <IMAGE>

Description

SPECIFICATION Forging press This invention relates to a mechanical crank forging press wherein atop ram is cyclically actuable by a cranktowards and away from a lower bolster.

Conventionally, the top ram carries a forging punch movable, during the downward forging stroke ofthe top ram, into co-operation with a toolset mounted on the lower bolster.

Such presses are not generally used in "flash less" forging since, in such techniques, a fully closed die cavity is provided in atoolsetwhich necessitates the exercise of extremely close, and hence relatively expensive, control on the size and temperature ofthe work-piece. If such close control is not exercised there is a danger ofthe press stalling or even breaking during the forging stroke. However such a mechanical crank press may be utilised forflashless forging without the necessity of exercising strict control on temperature and size ofthework-pieceif some form of pressure relief is provided to accommodate potential press overstressing; such a press with pressure relief being described in our British patent 2 107 231.The press described in this patent utilises a lockable split toolset providing a fully closed die cavity, hydraulic pressure relief being provided to accommodate potential overstressing of the press.

It has now been discovered that a mechanical crank forging press may also be used for closed die forging whereinthe movementofthetop ram during the forging stroke may be adapted to co-operate with a novel arrangement of toolsetfor applying forging pressureto awork-piece inthetoolset.

In accordancewith the inventionthere is provided a mechanical crankforging press having atop ram cyclically actuable by the crankfor movement towards and away from a lower bolster; a toolset having upper and lower die cavity-defining tools carried respectively on the top ram and lower bolster; a forging punch associated with one of said tools and being reciprocable into and out ofthe die cavity, said one of said tools being carried by a toolcarrying piston reciprocable within an hydraulic cylinder and said forging punch being caried bya punch-carrying piston also reciprocable within said hydraulic cylinder, the surface area ofthe punchcarrying piston acted on by the hydraulicfluidwithin the hydrauliccylinder being lessthanthesurface area ofthe tool-carrying piston acting on the hydraulicfluidwithin hydraulic cylinderwhereby, on closing movement of the top ram towards the lower bolster during a forging stroke, the upper and lower tools are brought into contact with one anotherto close the die cavity and hydraulicfluid displaced by the movement ofthe tool-carrying piston inwardly of said hydraulic cylinder displaces hydraulic fluid to expel the punch-carrying piston outwardly ofthe cylinder and hence to movetheforging punch into the closed die cavity.

Conveniently, the tool-carrying piston is of annular form and said punch-carrying piston is movable axially through said annulartool-carrying piston in sealing engagement therewith.

Thus hydraulic pressure is applied to the punchcarrying piston when the upper and lowertools are in contact and when thetool-carrying piston is moved inwardly of the hydraulic cylinder during the forging stroke of the top ram. The hydraulic pressure applied to the punch-carrying piston, and hence to the workpiece, cannot therefore cause the tools to separate because it is the pressure transmitted between the contacting faces of the tools during the forging stroke of the top ram which initiates the hydraulic pressure applied to the punch.

Other features ofthe invention will become apparent from the following description given herein solely by way of example with reference to the accompanying drawing which is a side crosssectional view th rough a press constructed in accordance with the invention.

The press illustrated in the drawing comprises a mechanical crankforging press having atop ram 10 vertically reciprocable by the action of the crank (not illustrated). The top ram 10 has securely attached thereto the upper tool 12 of a toolset co-operable with the lower tool 14 of thetoolset to define therebetween when the two tools are in contact with one another along respective lower and upper planar surfaces 16 and 18, a closed die cavity.

The lowertool l4ofthetoolset is mounted upon a split adaptor ring 20 itself clamped by a clamping ring 22to a large diameter annular piston 24 movable vertically within an hydrauliccylinder26 on the lower bolsterofthe press.

The annular piston 24, i.e. the tool-carrying piston, provides a central cylindrical bore within which there is mounted for reciprocable movement a further piston 28 in sealing engagement therewith. Said further piston 28 extends outwardly through a smaller diameter portion ofthe bore and carries on its upper surface a forging punch 30 projecting into the lower tool 14 ofthetoolset.

As shown in the drawing,the space 32 between the lower surface of the tool-carrying piston 24 and below the surface ofthe punch-carrying piston 28 is filled with hydraulicfluid.Abore 34 extends verticallyupwardlythrougha partofthetool- carrying piston and is provided with an openable and closable bleed valve 36 at its upper end. The space 38 abovethetool-carrying piston 24withinthe hydrauliccylinderisfilledwithairand isventedto atmospherethrough air breather holes 40.Similarly, the space 42 above the punch-carrying piston 28 is filled with air and may be vented to atmosphere or pressurised pneumatically through a conduit44 extending through the tool-carrying piston 24 for return movement ofthe punch-carrying piston 28 as will be further described herein. Adjuster bolts 46 extend through an upper closure 48 ofthe hydraulic cylinder 26 for defining the neutral position ofthe tool-carrying piston 24.

Said neutral position is achieved when the upper and the lowertools 12 and 14 of the toolset are separated (i.e. before the forging stroke commences) byapplying pneumaticpressurethroughconduit44 above the upper surface of the punch-carrying piston 28to force it downwardly and hence displace hydraulic fluid and force the tool-carrying piston 24 upwardly until it abuts the adjuster bolts 46. At this stage, the forging punch 30 is thus at its lowermost position within the die cavity of the lower tool 14 and a work-piece, such as a cylindrical work-piece, may be inserted through the open top of the die cavity in the lowertool 14.

Upon downward movement ofthe top ram 10 during actuation of the forging stroke, the lower planar surface 16 of the upper tool 12 will contact the upper planar surface 18 of the lower tool 14 to close the die cavity. Further downward movement ofthetop ram 10 will press the lower tool 14 downwardly towards the bolster and hence, through the adapter ring 20 and clamping ring 22, will also cause the tool-carrying piston 24to move inwardly of the hydraulic cylinder 26 thereby displacing hydraulic fluid to expel the punchcarrying piston 28 outwardly and upwardly of the tool-carrying piston 24. Such movement brings the forging punch 30 upwardly into the closed die cavity to exertforging pressure on the work-piece located therein; a partially displaced position ofthe punch 30 being shown in the drawing.

The total surface area ofthe annulartool-carrying piston 24 acting upon the hydraulic fluid is considerably greater than the surface area of the punch-carrying piston 28 whereby the downward movement of the top ram 10 imparts a movement of the punch 30 towards the work-piece which is greater than the movement of the top ram 10; such movement of the punch 30 also being faster than the movement of the top ram 10 proportional to the difference in the respective total surface areas of the tool-carrying piston 24 and punch-carrying piston 28 which are exposed to the hydraulic fluid within the cylinder 26.The force transferred back from the punch-carrying piston 28 via the hydraulic fluid to the tool carrying piston 24 is increased in the same proportion as the aforesaid difference between the total surface areas of the respective pistons thus ensuring a high die-closing force during the forging operation which is essential to the ability of the press to produce a flashless forging.

Control of the pressure developed in the hydraulic cylinder during the forging stroke is achieved by the provision of a pressu re-relief valve (not illustrated) connected to a port 50 in the space 32 of the hydraulic cylinder. ,; As illustrated in the drawing, the work-piece is of cylindrical form which, during the forging stroke, is deformed to the shape defined by the die cavity (as illustrated) by the movement of the forging punch 30 within the die cavity.

The forging press described herein in accordance with the invention comprises an hydraulically actuated forging punch 30 mounted on the lower bolster of the forging press. However, it will be appreciated that the arrangement may be "inverted" in that the whole of the tool-carrying piston 24, the punch-carrying piston 28 and their hydraulic cylinder 26 may be carried by the top ram 10, a fixed lower tool then being provided on the lower bolster.

Claims (3)

1.A A mechanical crank forging press having a top ram cyclically actuable by the crank for movement towards and away from a lower bolster; a toolset having upper and lower die cavity-defining tools carried respectively on the top ram and lower bolster; a forging punch associated with one of said tools and being reciprocable into and out of the die cavity, said one of said tools being carried by a toolcarrying piston reciprocable within an hydraulic cylinder and said forging punch being carried by a punch-carrying piston also reciprocable within said hydraulic cylinder, the surface area of the punchcarrying piston acted on by the hydraulic fluid within the hydraulic cylinder being less than the surface area of the tool-carrying piston acting on the hydraulic fluid within hydraulic cylinder whereby, on closing movement of the top ram towards the lower bolster during a forging stroke, the upper and lower tools are brought into contact with one another to close the die cavity and hydraulic fluid displaced by the movement ofthetool-carrying piston inwardly of said hydraulic cylinder displaces hydraulic fluid to expel the punch-carrying piston outwardly of the cylinder and hence to move the forging punch into the closed die cavity.

2. Aforging press as claimed in Claim 1 wherein the tool-carrying piston is of annular form and said punch-carrying piston is movable axially through said annular tool-carrying piston in sealing engagement therewith.

3. Aforging press substantially as herein before described with reference to the accompanying drawing.