FR2663587A1 - DRIVE MECHANISM WITH CONTROL FOR MECHANICAL PRESSES. - Google Patents

Abstract

Drive mechanism with control for mechanical presses. The present invention relates to a drive mechanism with control for mechanical presses, in particular for forming sheets at high speed, consisting of a drive mechanism for converting the rotation of the drive wheels into a rectilinear movement of the slide and of a second displacement system whose transmission functions overlap during a determined phase of the travel of the slide, characterized in that the pressure point of the slide (2), designed as a double-acting cylinder (1) with piston differential, can be driven by a pneumatically actuated hydraulic pressure accumulator (10) and can be controlled by a throttle valve (12) with forced actuation depending on the stroke, placed between the pressurized fluid reservoir (8) and the cylinder (1).

Description

Drive mechanism with control for mechanical presses This

  The invention relates to a drive mechanism with control for mechanical presses, in particular for forming high-speed sheets, consisting of a drive mechanism for converting the rotation of the drive wheels into a rectilinear movement of the slide and of a second system of

  movement whose transmission functions are super-

  pose during a specific phase of the slide stroke. There is known a drive mechanism for mechanical presses in which a drive mechanism for converting the rotation of the drive wheels into a rectilinear motion of the slider is controlled by a second displacement system with transmission functions which operate during determined phases of the slide stroke The pressure point of the slide, which is designed as a double-acting cylinder with a differential piston, allows one of these forced-action telescopic pistons to control the slide, by means of

  of a liquid under pressure, before the start of stamping

  wise, so that we get a reduction in the

  velocity, proportional to the corresponding speed of the

  bucket This solution does not provide a constant impact velocity at the beginning of stamping, with

  different rates or depths of stamping.

  It does not allow to achieve speeds

  of different impact for the same speed of the slide.

  According to the document DD-WP 220 487, there is known a drive mechanism for mechanical presses in which the speed of the slide adapts to the technological conditions, in determined phases of the race, by a two-stage transmission between the mechanism

  drive and the slide, consisting of a transmission

  empty transmission and transmission under load The transmission

  load is a cam and crank mechanism consisting of a crank connected to the drive wheel and a two-part link, the two parts of which are slidably mounted along their length relative to one another , telescopically and support during the working phase on a cam joint constituted

  two cam segments rolling on one another.

  In this solution, the rigid design of the displacement does not allow to adapt to the depth

  stamping of the pieces to be formed.

  This solution is very expensive because the

  Crank and cams require a great deal of mechanical complexity. The invention proposes to make a press drive mechanism and its control, with a technical complexity as small as possible, which allows to obtain a reduced speed of impact, at high speed, when closing the press. tool, this reduced speed of the drive mechanism of the press operating before forming and can be set to any value, regardless of the speed of the press and

deep drawing.

  This object is achieved according to the invention in that the pressure point of the slide, designed as a double-acting piston with differential piston can be driven by a pneumatic hydraulic pressure accumulator and can be controlled by a valve of throttling stroke-dependent throttle positioned between the pressurized fluid reservoir

and the cylinder.

  It is also within the scope of the invention to apply this solution to cutting presses and for the preliminary acceleration of the stamping pad.

before the start of stamping.

  This solution has the advantages of a better quality of the formed part, an optimization of the impact velocity, a reduction of the noise due to forming as well as an increase in the speed of the press

  to increase the yield.

  Various other features of the invention

  The following detailed description emerges:

  embodiment of the invention is shown by way of non-limiting example in the accompanying drawings, in which:

  Figure 1 shows the training mechanism

  Hybrid with the example of a two-point slider with crank mechanism, hydraulic pressure accumulator with pressure multiplication and accumulator charge

  pressure by means of a jack driven by the slider.

  The hybrid drive mechanism will be described

  following by the work cycle of a sliding run

  bucket It is considered that the initial position corresponds to the top dead center of the crank mechanism While the differential piston of the cylinder 1, hingedly coupled to the crank mechanism, by other active elements, occupies the high position, the slider 2 is located lower than a distance corresponding to the race of

  work of the hydraulic mechanism and

  only on working piston 1, in the chamber

  higher pressure fluid 3 The differential piston

  1 of the jack 1 is with the small upper active surface 6 of pressurized fluid and the large lower active surface 7 of pressurized fluid which

  each support the slide 2, through

  mediates the upper fluid chamber 3 and the lower fluid pressure chamber 4 The two pressurized fluid chambers 3 and 4 are connected directly and indirectly to the fluid reservoir under

  pressure 8 whose liquid under pressure is pneumatic-

  pre-stressed, the pneumatic pressure being

  set differently by means of the pressure regulator 16.

  The weight of the slider 2, including the punch fixed thereto, is balanced, in known manner, by a balancing cylinder 44. The difference between the active surfaces of the upper and lower pressure fluid 6 and 7 ensures, once multiplied by the pressure in the fluid reservoir under pressure 8, a force acting on the slider 2 which ensures its lower position, mechanically limited, with a limited overbalance In the initial position of the slide at the top dead center, the dispensing valve 9 which is placed between the pressurized fluid chambers 3 and 4, is in the open position and the piston of the hydraulic pressure accumulator 10 whose pressure acts on the active surface of the upper pressurized fluid 6, is in the

  end position unloaded.

  The non-return valve 11 and the shut-off valve 12, which can be closed, are arranged in parallel in the pipe connecting the lower pressure fluid chamber 4 and the pressurized fluid reservoir 8. At the beginning of the stroke of the slide towards the top dead center, a command cam signal closes the

dispensing valve 9.

  Because of this and because of the choke valve

  12 being in the closed position and the non-return valve closing the outlet of the lower pressure fluid chamber 4, the pressurized liquid is enclosed in the pressurized fluid chamber 4, so that no displacement relative to the differential piston of the cylinder 1 and the slide is not possible The slide 2 moves downwards at the speed of the piston

differential.

  In parallel with the displacement of the slide, the jack 13 serves as a pressurized liquid pump, driven by the slide 2 During the stroke of the slide, the plunger 14, integral with the slide 2, expels the pressurized liquid from the jack 13, connected to the frame of the press, in the hydraulic pressure accumulator 10, through the plunger 14 configured hollow rod The pressure accumulator 10, shown in this application example as a pressure multiplier, can also be in In the form of a piston or bubble accumulator the pressure of the liquid in the hydraulic pressure accumulator 10 and in the pressurized fluid reservoir 8 is predetermined by the adjustment of the pneumatic pressures by means of the pressure regulator.

pressure 15 or 16.

  The pressurized fluid chamber 17 of the accumulator 10, filled with liquid under pressure,

  communicates through the lines 18 with the upper chambers

  pressure fluid 3 and the pipe 19 with the cylinder 13, the non-return valve 20 being mounted in the pipe 19, so as to close the flow in the direction of the cylinder 13. The pressure in the chamber pressurized fluid 17 is such that multiplied by the surface of upper pressure fluid 6, it exerts on the slider 2, a force directed against its gravitational force, which is greater than the force acting in the direction of gravity, in the lower pressure fluid chamber 4, which is formed by the product of the lower active surface of pressurized fluid 7 and the pressure of the pressurized fluid reservoir 8, acting

  in the lower fluid chamber 4.

  The mass of the slider 2, including that of the punch, is compensated in known manner by a balancing cylinder 44, so that the forces acting in the upper and lower chambers 3 and 4 of the fluid under

  pressure are available to speed up the slider 2.

  Before the output of the integral punch of the slider 2, in the direction of the workpiece, mechanical contact occurs between the roller 24 and the tilting lever. This displacement phase is shown in FIG. displacement of the slider is determined solely by the mechanical kinematic chain 48. As the displacement continues, because of the mechanical kinematic chain 48, a relative displacement between the differential piston of the jack 1 and the slider 2 is due to the fact that the valve of 12 is forced open and as a result of the pressurized liquid is driven from the lower chamber 4 of fluid under pressure by the reduction of forces between the upper chamber 3 and the lower chamber 4, the liquid under pressure then flowing in the pressure fluid reservoir 8 The throttle valve 12 and the guide housing of the sliding parts 35 and 42 are integral with each other. of the slider 2, while the stop rod 26 is connected to the roller 24 in the stop cylinder 27, coupled to the frame of the press, so that during the stroke of the slide, the tilting lever 25 which is mounted The stop rod 24 is movably mounted in the stop cylinder 27 and can be rigidly tightened by means of the stop piston 28 which is connected to the stop rod 26. clamping is effected by the pressure in the fluid chamber under pressure 29, against the adjustable stop 30 The pressurized fluid chamber 29 is connected to the pressurized fluid reservoir 33 whose pressurized liquid is pneumatically prestressed Pneumatic prestressing can be modified by means of the pressure regulator on the roller 34 In the pipe connecting the fluid chamber under pressure 29 and the

  fluid reservoir under pressure 33, the non-return valve

  return 31 closing the outlet of the pressurized fluid chamber 29 and the pressure limiting valve 32 serving as overload protection for the cylinder

  stop 27, are connected in parallel.

  The stop 24 is adjusted in height according to

  the slider and the depth of

  by the adjustable stop 30, so that during the advance of the slider 2 and with it the throttle valve 12 and the slider 35 and the tilting lever 25, there is a contact between the stop 24 and the tilting lever 25, just

  before the impact of the punch on the workpiece.

  The lower fluid pressure chamber 4 and the pressurized fluid reservoir 8 communicate through the pipe 49, the throttle valve 12 and the pipe. Parallel to this, there is a connection by the non-return valve 11 with a function closing

  in the direction of the pressurized fluid reservoir 8.

  The throttle valve 12 has a similar function in the same direction, in its initial position, because it is designed as a spring loaded seat valve.

  protrudes from both sides outwards, by an extension

  with each side a roll 34 placed at the end and the tilting lever 41, is held in position

  closing by the pressure spring 38.

  As the slide 2 advances, the tilting lever 25 is raised a distance equal to the opening stroke 51 and thus pivots around its support in the sliding part 35, so that the valve tappet 37 is continuously open from its closed position by the roller 34 resting on the tilting lever 25. The increasing opening section of the throttling valve 12 results in an increasing flow from the lower chamber 4 towards the fluid reservoir under pressure, which causes a relative displacement of the slider 2 against the differential piston of the cylinder 1, mechanically driven and thus reducing the

  impact velocity between the punch and the workpiece.

  The sliding part 35 with the support of the tilting lever 25 is slidably placed in a guide member and is held in its end-of-travel position by a pressure spring against the adjustable stop 36. The adjustment of the stop 36 causes a displacement. of the support of the tilting lever 25 in the sliding part 35 and thus a modification of the opening characteristic of the throttling valve 12. As a result and / or by adjusting the pressure in the fluid chamber under pressure 17 to By means of the pressure regulator 15, it is possible to adjust the return speed or the impact speed of the slide for press speeds and drawing depths.

different.

  After pivoting of the tilting lever 25 on the stroke 51, it is mechanically limited which causes the driving of the stop rod 26, until then at rest, by the stop 24, during the continuation of the advance of the throttle valve 12 secured to the slider 2; it follows that the movement of the slider to the low point expels the liquid from the pressurized fluid chamber 29, through the

  pressure 32 in the pressurized fluid reservoir 33.

  Faced with the throttle valve 12 with the valve tappet 37 are the elements 39, 42, 43, 40 and 41 which have the same function and the same designation as the tilt lever 25, the slider 35, the stop 36, the stop 24 of the roller 34 The stop 40 is here connected

  to the driving piston 1, by the driving rod 47.

  Just after the impact of the punch on the part to be formed during the relative stroke of the differential piston of the cylinder 1 and the slider 2, about 50% of the working stroke 5 of the hydraulic mechanism, there is a mechanical contact between the stop 40 and the tilting lever 39 The slide continues its advance, the stop 40 causes the tilting lever 3 which is mounted in the slide piece 42, pivots a distance equal to the closing stroke 52 It follows that the valve pusher 37, opened just before, is closed depending on the stroke, which causes a reduction in the relative speed between the differential piston of the drive cylinder 1 and the slider 2, as a result of the reduction of the flow rate of the fluid chamber under lower pressure 4, until the mechanical contact between the differential piston and the stop piston 45 From this moment, the slide continues its stroke to the bottom dead point, by the chain ci During the return of the slider, after bottom dead center, the volume of the working cylinder 13 which is filled by the pressurized fluid reservoir 8, pneumatically prestressed, via the nonreturn valves 11 and 21, increases. . The dispensing valve 22 which allows a circulation without pressure of the fluid and the pressure limiting valve 23, protecting the circuit of the pump, are connected in parallel in the piping of

  connection between the plunger 14 and the chamber

  fluid pressure 4 with the non-pressure valve

  back 21 closing the flow in the direction of the chamber

  lower fluid pressure 4 The recall of the

  bucket 2 relative to its initial position, on the working stroke 5 of the hydraulic mechanism, is performed during the return of the slide between the bottom dead center and the top dead center, by switching the distribution valve 9 to the open position There is thus established a balance of pressures between the upper and lower chambers 3 and 4 and the fluid chamber under pressure 17 is relaxed The hydraulic accumulator 10, the slider 2, the drive rod 47 and the stop rod 26 succeed

in their initial position.

  The hydraulic overload protection 46, located below the stop piston, operates from

known way.

Claims (2)

  1 Drive mechanism with control for mechanical presses in particular for forming high speed sheets, consisting of a drive mechanism for converting the rotation of the drive wheels into a rectilinear motion of the slide and a second displacement system whose transmission functions are superimposed during a given phase of the travel of the slide, characterized in that the pressure point of the slide (2), designed as a double-acting cylinder (1) with a differential piston, can be driven by a hydraulic pressure accumulator (10) with control   pneumatic and can be controlled by a foreign valve   (12) as a function of the stroke, placed between the pressurized fluid reservoir (8) and the cylinder (1).   2 drive mechanism with control for mechanical presses according to claim 1, characterized in that the forced control of the throttle valve (12), fixedly placed in the slider (2), can be achieved during the movement of the slide, by a tilting lever (34), in operative connection with the pusher (37) of the throttling valve (12) and a displaceable stop (24), placed in the press body, associated with this tilting lever as well as by a tilting lever (41), in operative connection with the valve tappet (37) and a displaceable stop (40), placed on the   differential piston of the cylinder (1), associated with this rocking lever.