GB2090189A - Press drive - Google Patents

Abstract

A drive for a fast running crank driven press, comprises a crankshaft 2, having two eccentrics 7, 21 and a crank 6, a crank driven ram 3 and balancing masses 18, 32 for the ram 3. Each eccentric 7, 21 is pivotally connected to one end of a rocker arm 15, 29 by means of a link member 9, 23 mounted on the eccentric and having a balancing mass 18, 32 and a pin 11, 25. The other end of the rocker arms 15, 29 are pivotally mounted in the frame 1 via a pins 17 (31). The eccentrics 7, 21 are arranged rotated in opposite directions through similar angles of twist 62, (63) with respect to a vertical plane of reference 41. The pins 17 and 31 in the frame are disposed oppositely one another. <IMAGE>

Description

SPECIFICATION Drive for presses This invention relates to a press drive having a crankshaft, a crank driven operating ram and balancing masses for the ram.

The invention is advantageously used in fastrunning presses with crank driven rams for the manufacture of can components. The invention may also be used with crank mechanisms having extreme values for the number of strokes, stroke magnitude and the mass moved, for example in the case of punchers, cutting machines, automatic shaping machines and crank shears.

Balancing devices in crank driven presses having complete mass balancing of the crank driven operating ram are known. The balancing devices are provided with a crank driven counterram. The counter-ram comprises the balancing mass for the operating ram. The crank drive of the counter-ram is formed by two connecting rods which are supported on both sides of the connecting rod of the operating ram on eccentric collars of the crankshaft. The eccentricity of the eccentric collars for the crank-drive of the counterram is offset by 1 800 with respect to the eccentricity of the crank for the crank drive of the operating ram. The counter-ram moves in six-fold or four-fold guide paths (German Offenlegungsschrift 16 27 899 and U.S.Patent Specification 3.611.918). The direction of movement of the counter-ram is opposite to that of the operating ram.

Furthermore, a device for balancing the forces of inertia in two-step crank driven presses is known. In accordance with this, the counter-ram is connected in an articulated manner with one place on the crank of the crankshaft. The crank for the balancing device is disposed between the two cranks of the connecting rod of the operating ram.

The counter-ram is provided with a column guide (German Offenlegungsschrift 24 54 959).

The complex construction of the counter-ram and its guide is disadvantageous in the case of the known devices for balancing the forces of inertia.

Moreover, the guide for the counter-ram increases the dimensional variation of the press frame. The driving torque and the driving power of the ram drive with the known balancing devices is greater than in the case of balanced mechanisms, as the mass of the operating ram must be accelerated at the same time as the mass of the counter-ram as a result of the displacement by 1 800. The balancing devices are only designed for crank driven presses with small ram strokes.

The invention aims at simplifying the drive of a low-vibration crank driven machine and to reduce the driving torque and the driving power.

An object of the invention is to provide a machine drive having an auxiliary transmission, which does not require accurate guiding and effects an approximately complete balancing of the forces of inertia and an approximately constant reduced mass moment of inertia on the crankshaft.

Accordingly, the present invention consists in a press drive having a crankshaft with two eccentrics, a crank driven operating ram and balancing masses for the ram, characterised in that one crankshaft eccentric on one side of the crank is arranged rotated in one direction through an angle of twist with respect to a vertical plane of reference and is pivotally connected to one end of a rocker arm by means of a link member having a balancing mass and a pin, the other end of the rocker arm being pivotally mounted in the press frame via a pin, and in that the other crankshaft eccentric on the other side of the crank is arranged rotated in the other direction through an angle of twist with respect to the vertical plane of reference and is pivotally connected to one end of a further rocker arm by means of a further link member having a further balancing mass and a further pin, the other end of said further rocker arm being pivotally mounted in the press frame via a further pin, the pins at the other end of the rocker arms being preferably located opposite one another in the frame, and the angles of twist being preferably of the same magnitude.

On rotation of the crankshaft the operating ram effects the known stroke movement. The balancing masses are simultaneously moved via the eccentrics and the two link members by the crankshaft. The course of the movement of the balancing masses is out of phase with one another, i.e. the points of inversion are passed through successively. The phase displacement of the courses of movement of the balancing masses results from the twisting of the eccentrics with respect to the crank. The exact determination of the angle of twist is provided in accordance with the geometry and mass distribution of the press drive from the requirement for approximately simultaneous balancing of the forces of inertia and power balancing.

The balancing mass may be modified in accordance with the mass of the upper tool part used. The mass and the shape of the balancing masses are conveniently identical.

The particular advantages of the invention consist in that the arrangement of the balancing gear is very economic in terms of space and has a very simple construction, in that the crankshaft is in particular very short and torsionally rigid and its bearings have a very small spacing with respect to one another and it is therefore very rigid with respect to bending, in that the two balancing masses provide sufficient forces of inertia to compensate the forces of inertia of the operating ram and the forces of inertia of the balancing masses working in this respect at right angles to the operating line of the ram are almost completely compensated by the opposite points of articulation, in that as a result of the twisting of the eccentricity in the angular range of 100 to 1200 of the eccentrics the two balancing masses and the operating ram produce an approximately constant reduced mass moment of inertia on the crankshaft and therefore that a low driving torque and a smaller power input of the press drive is required, as the mass of the operating ram is not accelerated at the same time as the balancing masses.

An optional feature of the invention consists in that a divided eccentric with a key is mounted on one side of the crank on a crankshaft collar and is rotated by an angle of twist in one direction with respect to the perpendicular plane of reference, and in that a further divided eccentric with a key is mounted on the other side of the crank on a crankshaft collar and is rotated in the opposite direction by the angle of twist with respect to the plane of reference, the crankshaft collar on one side of the crank and the crankshaft collar on the other side of the crank having a common axis of symmetry.

The particular advantage of this construction is the comparatively simple and easy construction of the crankshaft, comprising the use of undivided crankshaft bearings for the crankshaft and the considerably simplified mounting of the crankshaft overall. Furthermore, any angle of twist may be selected and secured by the key of the eccentric.

The crankshaft collar on one side of the crank may have one axis of symmetry and a crankshaft collar on the other side of the crank may have another axis of symmetry.

The particular advantage with respect to previously described construction is the further simplified construction of the crankshaft and the divided eccentrics as a result of the reduction of the external diameter.

The divided eccentric may be adjustably disposed on the crankshaft collars without the keys. Preferably, the balancing masses are mounted on the rocker arms.

This construction is advantageously used in the case of machine frames which are formed differently from the present embodiment or for very small balancing masses. In a simple construction the balancing mass is integrated in a way which is economic in terms of space in the rocker arms.

An optional feature of the invention is that other transmission gears are connected to the link member.

If a transmission gear is connected, the balancing masses are disposed at another location in the machine frame, for example below the working area. The articulation may be on both sides or on one side. The articulated transmission gear may be embodied as a known crank mechanism. The known devices for balancing the forces of inertia having a counter-ram twisted through 1800 may achieve in an inexpensive manner an approximate balancing of the forces of inertia and an approximately constant reduced mass moment of inertia on the crankshaft, if the rotated arrangement of the invention is used.

In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically and by way of example embodiments thereof, and in which: Fig. 1 is a side view of a fast-running crank driven press, Fig. 2 is a cross-section on the line A-A of Fig.1, Fig. 3 is a cross-section on the link B-B of Fig. 2, Fig. 4 is a cross-section on the line C-C of Fig. 2, Fig. 5 shows a detail from Fig. 3 having a further embodiment of the crankshaft cam, Fig. 6 shows a detail from Fig. 4 with a further embodiment of the crankshaft cam, Fig. 7 shows a detail from Fig. 3 with a further embodiment of the crankshaft cam, and Fig. 8 shows a detail from Fig. 4 with a further embodiment of the crankshaft cam.

The crank driven press illustrated in Fig. 1 comprises an inclined press frame 1 having a crankshaft 2 with eccentrics 7 and 21 mounted in the upper portion of the frame, the crankshaft carrying a connecting rod 3 having a pivot pin 4 connected to a ram 5.

Fig. 2 shows the arrangement of the press drive in cross-section and Fig. 3 shows the left-hand side (as viewed in Fig. 2) of the balancing device and Fig. 4 the right-hand side of the balancing device in cross-section.

The crankshaft 2 with the eccentrics 7 and 21 is mounted in the press frame 1 by means of bearings 20 and 34. A first two-part link member 9 held together by connection screws 10 is mounted on a bearing 8 which is in turn mounted on the crankshaft eccentric 7 on the left-hand side (as viewed in Fig. 2) of the crank 6. The eccentric 7 is shown rotated anti-clockwise through the angle of twist 62 with respect to a plane of reference 41.

A balancing mass 18 is fastened to the link member 9 by means of screws 19. A rocker arm 1 5 constructed as a bell-crank lever is pivotally mounted at one end in the frame 1 by means of a bearing 16 and pin 17, and is pivotally connected at its other end to the link member 9 via a bearing 12, pin 11, bearing cover 13 and screw 14.

A second two-part link member 23 held together by connection screws 24 is mounted on a bearing 22 which is in turn mounted on the crankshaft eccentric 21 on the right-hand side (as viewed in Fig. 2) of the crank 6. The eccentric 21 is shown rotated clockwise through the angle of twist 63 with respect to the plane of reference 41.

A balancing mass 32 is fastened to the link member 23 by means of screws 33. A rocker arm 29 is pivotally mounted at one end in the frame 1 by means of a bearing 30 and pin 31, and is pivotally connected at its other end to the link member 23 via a bearing 26, pin 25, bearing cover 27 and screw 28.

The connecting rod 3 with the pivot pin 4 is mounted on the crank 6. The ram 5 is connected to the pin 4 and guided in the press frame 1.

Fig. 5 shows a further embodiment of the lefthand crankshaft eccentric 7, and Fig. 6 a further embodiment of the right-hand crankshaft eccentric 21, these being embodied separately from the crankshaft 2. A divided eccentric 37 is clamped on a left-hand crankshaft collar 35 by means of clamping screws 38 and is secured against rotation relative to the collar 35 by a key 36. The eccentric 37 is shown rotated anticlockwise through the angle of twist 62 with respect to the plane of reference 41.

A divided eccentric 44 is clamped on a righthand crankshaft collar 42 by means of clamping screws 45 and is secured against rotation relative to the collar 42 by a key 43. The eccentric 44 is shown rotated clockwise through the angle of twist 63 with respect to the plane of reference 41.

The left-hand crankshaft collar 35 and the right-hand crankshaft collar 42 have a common axis of symmetry 39.

Figs. 7 and 8 show a further embodiment of the left-hand and right-hand crankshaft eccentrics 7 and 21, these being embodied separately from the crankshaft 2.

A divided eccentric 50 is clamped on a lefthand crankshaft collar 48 by means of clamping screws 51 and secured against rotation relative to the collar 48 by a key 49. The eccentric 50 is shown rotated anti-clockwise through the angle of twist 62 with respect to the plane of reference 41.

A divided eccentric 57 is clamped on a righthand crankshaft collar 55 by means of clamping screws 58 and secured against rotation relative to the collar 55 by a key 56. The eccentric 57 is shown rotated clockwise through the angle of twist 63 with respect to the plane of reference 41.

The left-hand crankshaft collar 48 has one axis of symmetry 52 and the right-hand crankshaft collar 55 has another axis of symmetry 59.

A further embodiment is provided by the omission of the keys 36, 43, 49 and 56 and providing a more reliable clamping of the eccentrics 37, 44, 50 and 57. The advantage of this embodiment is that it enables a stepless adjustment of the angles of twist 62 and 63.

Claims (7)

1. A press drive having a crankshaft with two eccentrics, a crank driven operating ram and balancing masses for the ram, characterised in that one crankshaft eccentric on one side of the crank is arranged rotated in one direction through an angle of twist with respect to a vertical plane of reference and is pivotally connected to one end of a rocker arm by means of a link member having a balancing mass and a pin, the other end of the rocker arm being pivotally mounted in the press frame via a pin, and in that the other crankshaft eccentric on the other side of the crank is arranged rotated in the other direction through an angle of twist with respect to the vertical plane of reference and is pivotally connected to one end of a further rocker arm by means of a further link member having a further balancing mass and a further pin, the other end of said further rocker arm being pivotally mounted in the press frame via a further pin, the pins at the other end of the rocker arms being preferably located opposite one another in the frame, and the angles of twist being preferably of the same magnitude.

2. A press drive as claimed in claim 1, wherein a divided eccentric with a key element on one side of the crank is mounted on a crankshaft collar and is rotated in one direction through an angle of twist with respect to the perpendicular plane of reference, and in that a further divided eccentric with a further key element on the other side of the crank is mounted on a further crankshaft collar and is rotated in the other direction through the angle of twist with respect to the perpendicular plane of reference, the two crankshaft collars having a common axis of symmetry.

3. A press drive as claimed in claim 2, wherein one crankshaft collar has one axis of symmetry and the other crankshaft collar has another axis of symmetry.

4. A press drive as claimed in claim 2 or 3, wherein the divided eccentrics are mounted adjustably on the crankshaft collars without key elements.

5. A press drive as claimed in claim 1 , wherein the balancing masses are provided on the rocker arms.

6. A press drive as claimed in claim 1 or claims 1 and 5, wherein other known transmission gears are connected to the link member.

7. A press drive, substantially as herein described with reference to and as shown in the accompanying drawings.