MXPA98006758A - Mechanical press with mechanism of l - Google Patents

Abstract

The present invention relates to a mechanical press characterized in that it comprises: a frame having a platform, a piston carried by the frame for reciprocal movement towards and outside the platform, a first pivot carried by the frame, at least a first arm constructed to rotate about the first pivot to drive the platform, a second pivot carried by the frame, an actuator, and at least one pivot joint each having one end pivotally connected to the second pivot and the other end operably connected to the actuator and in a pivotable and sliding manner is associated with the first arm, whereby the actuator drives the pivot joint to rotate about the second pivot that urges the first arm to rotate about the first pivot and move the piston between advanced and retracted positions.

Description

MECHANICAL PRESS WITH CAM MECHANISM Field of the Invention This invention relates generally to a forming press and more particularly to a mechanical press using an articulated cam mechanism.

Background of the Invention A forming press can be used to perform various forming operations on a metal sheet workpiece, such as drilling, trimming, beading, shaping and the like. To provide the necessary force to the tool or die of the press acting on the metal workpiece, some preforming presses have used a cylinder driven by a fluid under pressure, such as a pneumatic or hydraulic cylinder. Cylinders driven by a fluid, either pneumatic or hydraulic, require highly effective seals to prevent leakage of fluid under pressure. Contaminants adjacent to the cylinder can degrade or destroy the seals leading to fluid leaks Ref.028176 which cause a reduced press output force or press failure. This may require the replacement of the seal or, in some cases, the cylinder driven by a complete fluid. Accordingly, cylinders driven by a fluid are not durable, are somewhat expensive, and because of the leakage they can provide a decreasing force to the piston of the press during the life of the cylinder, thereby affecting the operation of the press. Still further, the cylinders driven by a fluid, to provide sufficient force to the piston of the press, are generally large and relatively slow in operation. There are many restrictions on the size of the cylinders, for example, the high pressure required for the necessary output and the high cylinder temperatures in use, among other factors which arise during the use of the cylinders.

Brief Description of the Invention A mechanical press pulls a ram carried by a structure and movable to the advanced and retracted positions by a spherical screw assembly driven by an actuator, such as a reversible motor, to drive an eccentric roller assembly connected to the piston by an articulated system . The articulated system has a pair of pivot joints pivotally connected at one end to a fixed pivot shaft connected to the structure of the press and connected at the opposite end to a follower nut for movement therethrough when the follower nut travels along of the length of the impulse screw. A pair of roller followers are also driven by the follower nut to move between the first and second positions within the cam treads formed in a pair of first lever arms operatively connected to the piston. In use, when the motor drives the screw in one direction, the first lever arms are rotated in one direction to move the piston to its advanced position where the piston pushes a die or tool in engagement with a work piece. When the motor is inverted, the first lever arms are rotated in the opposite direction to move the piston to its retracted position to uncouple or die or tool from the workpiece. The joint is designed to maximize the mechanical advantage of the press in its advanced position whereby a maximum force is provided in this position to form the work piece. The articulated system is also designed to have a lower mechanical advantage when the press is moved adjacent to its retracted position to thereby increase the speed of the press when it is retracted from the work piece and reduce the force applied to the ram to increase efficiency of the system. Accordingly, the press has its highest force and its lowest speed adjacent to the advanced position to provide a controlled high force acting on the workpiece, and a lower force and a higher speed adjacent to its retracted position to rapidly retract the piston from the work piece, to advance the piston rapidly towards the work piece, to reduce the tension on the motor and the articulated assembly and to increase the speed and efficiency of the press. The objects, features and advantages of this invention include providing a mechanical press that uses an articulated assembly to provide a strategically varied force and speed of the press piston in use, when driven by a motor with a constant output speed in two directions opposite, provides maximum force and a controlled speed when forming the work piece, provides reduced force and increased speed when the piston is retracted from the workpiece and when the piston is initially advanced towards the workpiece, it makes possible the use of a smaller actuator, it comprises a fully mechanical joint driven by an electric motor, it does not depend on the integrity of a high pressure seal as in a cylinder driven by a fluid, it provides substantially the same output force throughout Its lifespan is extremely compact, resistant, durable, designed or relatively simple and inexpensive manufacturing, and in service, has a prolonged useful life.

Brief Description of the Drawings These and other objects, features and advantages of this invention will be apparent from the following detailed description of the preferred embodiments and in the best manner, the appended claims and the appended drawings, in which: Figure 1 is a view in perspective of a mechanical forming press according to the present invention; Figure 2 is a side view of the press in which this invention takes shape in its retracted position; Figure 3 is a schematic view of the press in its extended position; and Figure 4 is a top view of the press.

Detailed Description of the Preferred Modalities Referring in greater detail to the drawings, Figures 1-4 illustrate a mechanical press 10 in which this invention takes shape, with a piston 12 carried by a structure 14 and movable to the advanced and retracted positions by an actuator such as an assembly of spherical screw 16 driven by a reversible electric motor 18, to drive a roller cam assembly 20 connected to the piston 12 by an articulated system 22. Alternatively, the actuator may be a hydraulic or pneumatic cylinder or piston. The structure 14 has a pair of side elements 24 vertically and laterally spaced, fixed to a base plate 28 and interconnected by transverse plates 30. A slide 32 is mounted for reciprocating movement on the structure 14 by a pair of tracks 34 each secured to one of the side elements 24. A lower platform 36 is fixed to the press bed 10 and an upper platform 40 is fixed to the piston 12 for movement towards and away from the lower platform 36. Typically, the upper and lower forming dies bottom or other tool, are mounted on the platforms 36, 40 and moved to the open and closed positions by the reciprocating movement of the piston 12.

The articulated system 22 has a pair of first lever arms 42 interconnected by a spacer tube 44 and hinged by bearings 46 to move in a pivoting manner on a first axis 48 carried by the side elements 24 of the structure 14. Adjacent to one end, the lever arms 42 are pivotally connected to the piston 12 by bolts 50 received and carried by articulated blocks 51 carried by carriages 52 fixed to the piston 12. The carriages 52 allow the horizontal movement of the pivots in response to the rotation of the arms. This horizontal movement is along a trajectory perpendicular to the path of movement of the piston. The roller cam assembly 20 has a pair of roller followers 54 each received in a tread 56 of the separate cam, formed in plates 58 fixed or secured by cap screws 60 to the first lever arms 42. Each Roller follower 54 is hinged to a short end shaft 62 received and articulated adjacent to one end on a pair of pivot links or links 64 hinged about a pivot axis 66 adjacent to its other end by bearings 68 on a pair of plates carriers 70 fixed to the structure 14. Preferably, the treads 56 of the cam are formed in separate plates 58 mounted on the first lever arms 42 so that the contour of the treads 56 of the cam can be easily changed to adapt the press to different applications and to facilitate the repair or replacement of any worn treads of the cam. The spherical screw assembly 16 has a follower nut 72 connected to the short end shafts 62 which are hinged to the roller followers 54 and received on an impulse screw 74 driven by the reversible motor 18 and hinged for rotation in a housing 76 pivotally mounted by bearings 78 on the short end shafts 79 received through the carrier plates 70. To provide the preferred articulation geometry, the motor 18 is mounted in such a way that when the pivot connections 64 are at the midpoint of their travel, the screw 74 is generally perpendicular to the pivot connections or joints 64 so that the force is generally applied along the axis of the screw 74. The motor 18 can be an adjustable speed motor which is connected to the screw 74 through a clutch 75 or other torque limiting device, which limits the maximum torque applied to the screw 74 and here that the piston 12 prevents damage to the press mechanism and at high speeds it may slip somewhat due to the reduced mechanical advantage of the mechanism. This clutch arrangement preferably provides an essentially constant maximum applied torque or output torque to the follower nut 72 and roller follower 54.

Operation of the Press In Figure 2, the press 10 is shown in its fully retracted position where the piston 12 is on the top of the carriages 32. In this position, the follower nut 72 has been driven to the free end of the drive screw 74 by the motor 18 and consequently, the followers of roller 54 connected to the follower nut 72 by means of the shafts 62 have been moved on the tread 56 of the cam to a first end 80 of the treads 56 of the cam. In this position, the roller followers 54 rest on a first portion 82 of the treads 56 of the cam so that they tend to rotate the first lever arms 42 in the counterclockwise direction around the first shaft 48 to move the upper platform 40 away from the lower platform 36. To move the piston 12 from its retracted position to its advanced position as shown in Figure 3, the motor 18 is energized to rotate the driving screw 74 in a direction in which the follower nut 72 travels towards the engine 18 whereby it moves the followers of the roller 54 towards the second end 84 of each tread 56 of the cam and rotates the pivot connections 64 in the reverse direction of the handles of the clock around the pivot axis 66. In this position, the roller followers 54 rest on the second portion 86 of the tread 56 of the cam to rotate the first portions of the cam. lever blades 42 in the direction of the teloj hands about the first axis 48 to advance the piston 12 and consequently the upper platform 40 towards the lower platform 36 to close the dies placed on the platforms 36, 40 and by means of This will form the work piece placed between the arrays. When moved between their retracted and advanced positions, the mechanical advantage of the press 10 changes due to several factors. First, the effective length of the first lever arm, 42 from the point of contact of the roller followers 54 within the treads 56 of the cam to the first axis 48 is increased in the advanced position compared to the position retracted The increased effective length of the lever arms 42 provides an increased mechanical advantage to increase the force applied to the dies when the work piece is formed. A second factor are the different slopes of the first and second portions 82, 86 of each tread band 56 of the cam, which are engaged by the roller followers 54 when the piston 12 is moved adjacent to its retracted and advanced positions, respectively. When they are adjacent to the retracted position of Figure 2, the roller followers 54 engage the first portion 82 of each tread 56 of the cam which has an increasing and relatively gradual slope through approximately the first half of the movement of the cam. roller follower 54 within the tread 56 of the cam, which provides an increased travel speed of the first lever arm 42 when acting on the roller followers 54. This increased displacement provides an increased movement speed of the first arm of lever 42 and therefore of the piston 12. On the contrary, when adjacent to the advanced position of Figure 3, the roller followers 54 rest on the second portion 86 of the tread 56 of the cam which has a gradually inclined surface and provides a relatively slow speed of movement of the lever arm 42 and a force i ncremented applied to the lever arm 42 and consequently to the piston 12 to more forcefully and more slowly move the piston 12. Preferably, the tread 56 of the cam is constructed and arranged to provide a constant output force for an input force constant through approximately the last inch of travel of the roller follower 54 adjacent to the fully advanced position of the piston 12 to control the maximum force of the press 10 as a function of the maximum input force which is limited by the clutch 75 A third factor which takes into account the change in mechanical advantage is the relative position of the pivot axis 66, the trajectory of movement of the pivot connections 64, and the orientation of the treads 56 of the cam. The treads 56 of the cam are generally parallel to the path of movement of the pivot connections 64 when the piston 12 is adjacent to its advanced position. Accordingly, a given rotational movement of the pivot connections 64 provides a relatively small rotational movement of the lever arms 42. On the contrary, the movement path of the pivot connections 64 is more inclined to the treads 56 of the cam when the piston 12 is adjacent to its retracted position. Therefore, the same increase in rotational movement of the pivot connections 64 provides an increased rotational movement of the lever arms 42 adjacent to the completely retracted position of the piston relative to the fully advanced position of the piston. Accordingly, the lever arms 42, the pivot connections 64 and the cam tread 56 are designed to provide each an increased mechanical advantage when the piston 12 is adjacent to its advanced position to provide increased piston force. 12 while it is moving at a slower speed towards its fully advanced position and when the piston 12 initially retracts from its fully advanced position. Additionally, the lever arms 42, the pivot connections 64 and the tread band 56 of the cam provide a reduced mechanical advantage and increased speed of movement of the piston when the piston 12 is adjacent to its retracted position. The mechanical advantage of the press 10 can be further improved by providing a motor 18 which has variable speeds and / or output forces adjacent to the advanced and retracted positions of the piston.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following

Claims (13)

1. A mechanical press, characterized in that it comprises: a structure having a base; a piston carried by the structure for reciprocating movement towards and away from the bed; a first pivot carried by the structure; at least a first arm constructed to rotate about the first pivot to drive the piston; a second pivot carried by the structure; an actuator; and at least one connection or pivot joint each having one end pivotally connected to the second pivot and the other end operatively connected to the actuator and slidably and pivotally associated with the first arm, whereby the actuator drives the pivot connection or articulation so that turn around the second pivot which drives the first arm to rotate it around the first pivot and moves the piston between the advanced and retracted positions.

2. The press according to claim 1, characterized in that the actuator comprises an electric motor, a driven screw to rotate the motor and a follower received on the screw to travel axially along the screw when the screw rotates and the connection or articulation pivot is operatively connected to the follower.

3. The press according to claim 1, characterized in that the actuator comprises a cylinder having a rod of the piston operatively connected to the pivot connection or articulation.

4. The press according to claim 1, characterized in that the piston moves reciprocatingly along a generally linear path between the advanced and retracted positions and the pivot connection or articulation is generally parallel to the trajectory when the piston is at the halfway between their advanced and retracted positions.

5. The press according to claim 1, characterized in that the pivot connection or pivot rotates in a first direction about the second pivot when the piston moves from its retracted position to its advanced position causing the first arm to rotate in a second, opposite direction to the first direction, around the first pivot.

6. The press according to claim 1, characterized in that the first arm has generally opposite ends with the first pivot placed between them and the pivot connection or articulation is associated with the first arm generally adjacent to one end and the other end of the first arm is adjacent to the piston and the first pivot is located closer to the end of the first arm adjacent to the piston than the opposite end of the first arm.

7. The press according to claim 1, characterized in that it also comprises a third pivot around which the actuator is pivotally received to allow the pivoting movement of the actuator.

8. The press according to claim 2, characterized in that the motor operates at a constant maximum force in the directions both forward and backward.

9. The press according to claim 2, characterized in that it also comprises a clutch coupled with the motor to limit the maximum output force applied to the screw by the motor to prevent damage to the actuator and the piston.

10. The press according to claim 1, characterized in that it also comprises a tread of the cam carried by the first arm and an axis connecting the pivot connection or articulation, the follower and a roller follower received on the tread of the cam for operatively associating the pivot connection with the first arm so that when the pivot link or articulation rotates about the second pivot, the roller follower moves relative to the first arm within the tread of the cam and it rests on the first arm through the tread of the cam to cause the first arm to rotate about the first pivot.

11. The press according to claim 10, characterized in that the tread of the cam has a surface which is constructed to be displaced at an increasing speed by the roller follower when the piston is moved adjacent to its retracted position to provide a relatively fast rotation of the first arm and consequently a relatively rapid displacement of the piston.

12. The press according to claim 10, characterized in that the tread of the cam has a surface which is engaged by the roller follower when the piston is moved adjacent to its advanced position and the surface is constructed to provide a relatively smooth displacement. small of the first arm and consequently, the piston when it is adjacent to its advanced position.

13. The press according to claims 10, 11 and 12, characterized in that the distance between the follower of the roller and the first pivot is greater when the piston is in its advanced position than when the piston is in its retracted position to provide a mechanical advantage Increased press when the piston is adjacent to its advanced position. SUMMARY OF THE INVENTION The present invention relates to a mechanical press having a cam carried by a frame and movable to the advanced and retracted positions by a spherical screw assembly driven by a reversible motor to drive a roller eccentric assembly connected to the piston by a system articulate. The articulated system has a pair of connections or articulations pivotally connected at one end to a fixed pivot shaft connected to the structure of the press and connected at its opposite end to a follower nut for movement thereto when the follower nut travels at length of the impulse screw. A pair of roller followers are also driven by the follower nut to move between the first and second positions within the cam treads formed in a pair of first lever arms operatively connected to the piston. In use, when the motor drives the screw in one direction, the first lever arms are rotated in one direction to move the piston to its advanced position where the piston pushes a die or tool in engagement with a workpiece. When the motor is inverted, the first lever arm is rotated in the opposite direction to move the piston to its retracted position to decouple the die or die from the workpiece.