US3908437A

US3908437A - Power press with a flywheel and spindle drive

Info

Publication number: US3908437A
Application number: US392486A
Authority: US
Inventors: Horst Bachmann
Original assignee: Langenstein and Schemann GmbH
Current assignee: Langenstein and Schemann GmbH
Priority date: 1970-02-19
Filing date: 1973-08-29
Publication date: 1975-09-30
Anticipated expiration: 1992-09-30

Abstract

A power press in which there is provided a press head and an upwardly and downwardly movable ram together with a flywheel and spindle drive. A drive device is provided for the spindle and the flywheel can be coupled to the spindle and, in addition to the drive device for the spindle, there is a motor operably connected to the flywheel and running in a single rotational direction.

Description

United States Patent 11 1 Bachmann 1 Sept. 30, 1975 POWER PRESS WITH A FLYWHEEL ANI) SPINDLE DRIVE [75] Inventor: Horst Bachmann. Einberg. Germany abandoned.

[30] Foreign Application Priority Data Feb. 19. 1970 Germany 2007505 [52] US. Cl. 72/452; 72/454; 100/287; 100/291 51 Int. Cl.- 821.] 9 10 [58] Field of Search 72/452. 454. 453. 443. 72/445, 449; 100/271, 273, 270, 100/289, 290, 291

[56] References Cited UNITED STATES PATENTS 827.833 8/1906 Webb [00/291 2.245.573 6/1941 Crilev 72/454 3.122.033 2/1964 Riemensehneider 100/291 3.418.860 12/1968 Hun) IOU/289 3.512.476 5/1970 Georg 100/270 3.595.163 7/1971 Baumann.. 100/270 3.743.469 7/1973 Gibbons 100/291 FOREIGN PATENTS OR APPLICATIONS 7.550 12/1952 France 100/291 Primary E.vumim'r-Richard J. Herbst Assistant l;'.\uminerGene P. Crosby Attorney. Agent. or Firm-Holman & Stern [57] ABSTRACT A power press in which there is provided a press head and an upwardly and downwardly movable rum together with a flywheel and spindle drive. A drive device is provided for the spindle and the flywheel can be coupled to the spindle and. in addition to the drive device for the spindle. there is a motor operubly connected to the flywheel and running in a single rotational direction.

3 Claims. 5 Drawing Figures US. Patent Sept. 30,1975

. 5 Mn ea Sheet 2 of 3 Sheet 3 of 3 US. Patent Sept. 30,1975

7y I 34a POWER PRESS WITH A FLYWHEEL AND SPINDLE DRIVE This application is a division of my copending application Ser. No. 116,507 filed Feb. 18, 1971, now abandoned.

BACKGROUND OF THE INVENTION The invention relates to a power press with a die block and a flywheel and drive for a ram adapted for up and down movement, with the drive having spindles.

PRIOR ART A key press is disclosed besides spindle presses by the German Patent specification No. 1,265,548. In the case of the known wedge presses, a crank drive actuates a wedge gear unit which in turn acts on the ram. In addition, wedge presses are possible in which the wedge gear unit is actuated by a hydraulic cylinder-and-piston drive.

Power presses of the type defined at the outset are known from the German Patent specification No. 292,206 or from the German lain open document 1,283,972. They possess either a stationary or an axially movable, vertically arranged'spindle. The flywheel is either rigidly connected to the spindle or there is a clutch between spindle and flywheel, in which the spindle either engages at the ram with its thread or is rigidly connected to the ram. The power presses operate either with only one individual flywheel or with two flywheels which can be coupled together, the fixed flywheel being rigidly connected to the spindle and the loose flywheel being free of the spindle, but being capable of being connected to the spindle. There power presses possess, with a determined flywheel mass of the flywheel, a determined spindle rotation and a determined spring rigidly of the press body, a corresponding stress of the spindle. The fixed spindle arrangement with a vertical spindle has, in addition, the disadvantage that in the spindle portion between the spindle screw and transverse mounting there occurs, in a superimposed manner, pressure and torsion stresses. The spindles must be made larger to correspond to this superimposed stress. This is not only expensive but also gives rise to a relatively large frictional moment in the spindle nut.

As is well known, the drive of the hitherto known spindle presses with an electricmotor connected directlyto the spindle has the disadvantage that the power supply is loaded non-uniformly with short current surges. The energy of the press and the losses arising from the acceleration of the flywheel have to be supplied in the short acceleration time by the power supply. Particularly in the case of faststriking power presses, the instantaneous power is very large in relation to the mean power. These relationships are undersired and become all the more problematic the greater the spindle press is made.

OBJECTS AND SUMMARY OF THE INVENTION prising a press head, a ram for vertical reciprocating movement relative to the press head; a wedge for acting on the ram to produce a downward movement of the i 5 ram.

In this power press, there is a step-down gearing viz a wedge gear unit connected between the energy storage wedge system (flywheel) and the ram. The spindle stress is reduced by the stepping down of the wedge gear unit approximately in the ratio of the stepping down, with the spindle rotation becoming inversely proportional thereto. The flywheel masses, in turn, are reduced inversely proportionally by the square. The disadvantage, described at the outset, of a vertical, stationarily arranged spindle is eliminated by the transverse mounting of the spindle. The flywheel is arranged on the side of the spindle free from compressive stress, so that the spindle portion between the flywheel and spindle nut is stressed substantially only by torsion stresses and the other part between the nut and the thrust bearing essentially only by compressive stress.

A switchable friction or slipping clutch may be provided between the spindle and the flywheel. The clutch serves as an overload protection, i.e. it prevents stressing of the power press component parts by an inadmissably large force. The switchable slipping clutch may be embodied in a switchable manner in such a way that shortly after the beginning of the slip, the friction surfaces are completely separated from each other and remain separated during the return motion.

The loose flywheel is not negatively loaded during the return motion of the ram to the upper starting position, resulting in that a small amount of flywheel energy has to be overcome. The loose flywheel can, during the return motion, remain stationary or be loaded in the positive direction so that ona new stroke a part of the energy is already available.

It is, however, in practice very expensive to make large clutches of this type with extra-ordinary high moments of rotation as switch clutches. By the interposition of a stepdown gear, the slip moment of the clutch is reduced proportionally to the step-down ratio, e.g. in the case of a stepdown ratio of i=2, by half. In this way, it is possible to uncouple the flywheel at the beginning of the slipping and to keep it separated from the spindle during the return motion.

In a relatively small spindle press, the clutch is disengaged on attaining the so-called slipping moment or in the lower dead point in the manner described above, i.e., the electric motor is fully loaded during the forward motion only, while during the return motion it is operated with about half load. In this way, the motor is substantially thermally relieved of load and the degree of efficiency is improved. In a larger spindle press, the flywheel is disengaged in the same manner during the return motion. Furthermore, the disengaged flywheel is continuously driven in an unaltered direction of rotation during the return motion by a second electric motor which can be substantially smaller than the first.

If the striking sequence is not directly consecutive, the motor can bring'the flywheel to the synchronous rotation before the next working cycle is started. The motor, therefore, normally runs without interruption as long as the press is in operation. It is also possible to disconnect the motor shortly before the impact and switch it on again only after the impact. During the pressing operation, the motor is retarded by flywheel masses, but after the disengagement of the flywheel, it is immediately accelerated once more by the motor. During the forward motion, both motors together accelerate the flywheel masses coupled together. By this measure not only is the effective degree of drive decisively improved but also the above-mentioned unfavorable power supply loading is eliminated by the removal of the high current peak and idle power.

The starting current peak at the beginning of the forward motion at the motor for the fixed flywheel mass can be reduced still further, if, after switching on the working cycle, the rotating loose flywheel masses are firstly coupled with the fixed flywheel masses by the friction clutch and the latter are accelerated from the stationary position. The motor for the fixed flywheel masses is switched on only after a certain period of acceleration.

It is expedient if there is provided a piston-andcylinder arrangement for the displacement of the wedge. The transversely positioned spindle arrangement is namely advantageous for a cylinder-and-piston drive, in which the force effect expediently takes place on the wedge. During the displacement of the wedge in the direction of the spindle axis, the spindle and flywheel are acuated to rotate via the spindle nut. In the case of a hydraulic drive of this type, it is expedient to make the thread pitch of the spindle and the spindle nut as large as possible. The greater the thread pitch, the smaller, however, the spindle rotation becomes with predetermined ram velocity. For this reason, it is not possible in conventional power presses to make the thread pitch sufficiently large, because with a reduction in rotation of of the spindle, the flywheel masses had to increase by the square thereto. With the interposition of a wedge drive and the higher spindle rotation connected with it, it is possible without any difficulty to make the pitch of the spindle thread sufficiently large.

The invention is now described, by way of example, with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows, in section, a flywheel spindle press with an electrical drive;

FIG. 2 shows, in section, a flywheel spindle press with a hydraulic drive;

FIG. 3 shows, in section, a further hydraulic drive of a flywheel spindle press;

FIG. 4 shows, partially in section, a switchable slip clutch for a flywheel spindle press in accordance with FIGS. 1-3 and FIG. 5 shows an electrical circuit for a flywheel spindle press in accordance with FIG. '1 and a slip clutch in accordance with FIG. 4.

DETAILED DESCRIPTION OF THE EMBODIMENTS In the power press shown in FIG. 1, a ram 2 is provided for guided reciprocating movement in a power press stand 1, with the ram 2 carrying therebelow a tool 3. The press stand 1 has at the top thereof a press head 4 which is provided with a cavity 4a. In the cavity there is arranged a wedge 5 which slides with its longer, horizontally arranged cathetus on the top of the ram 2. The hypotenuse 5a of the wedge 5 is adapted to slide on a sloping surface 4b, on which the wedge 5 rises and moves downwardly, so that during the downward motion, it presses the ram 2 downwardly. It is possible to connect the wedge 5 to the ram 2 in a sliding fashion so that when the wedge 5 is raised, it also raises the ram 2. However, it is expedient to provide a hydraulic piston'and-cylinder arrangement 6 which engages on one side onto the ram 2 and on the other side onto the press head 4 to move the ram upwards during the return stroke.

A spindle 7 is disposed to two

thrust bearings

8a, 8b on the press head 4 and is axially immovable. A spindle nut 9 on the spindle 7 is axially displaceable along the spindle 7 and engages onto the wedge S. In this way, the spindle end to be coupled with a drive does not effect any axial movement. The spindle nut 9 as above mentioned, is provided on the wedge 5.

At the lower end of the spindle 7 there is arranged coaxially therewith, a flywheel 10 which is connectable to the spindle by means of a switchable slip clutch 11. An electric motor 12 which is continuously running in a single rotationally direction and is accommodated on the press head 4 serves as the drive of the connectable flywheel 10, The upper end of the spindle 7 is drivable by means of an electric motor 14 accommodated on the press head 4. At the upper end of the spindle 7 there is also provided a conventional brake 13 which serves both as a brake during the return motion and as a retaining brake. More particularly, the brake is pr0- vided in front of the end piece within a frame 14a and this encloses the part of the spindle 7 projecting from the press head 4. The brake is a drum brake of the type known in the automobile art and checks 13b are provided on the outside and a drum 130 on the inside. The drum is connected to the spindle. In the power stroke, the clutch 11 is engaged and the continuously running motor 12 and fly wheel 10 then impart motion to spindle 7 which begins wedge 5 in its motion to start the power stroke of ram 2. When the fly-wheel, clutch and spindle reach a predetermined acceleration, motor 14 is switched on.

The power press shown in FIG. 2 is to a large extent constructed in the manner as the power press shown in FIG. 1. However, in this case, the spindle nut 9a is arranged axially immovable in the press head 4a. The spindle 7a is shortened in comparison with the spindle 7 shown in FIG. 1, and is axially movable and engages with its lower end onto the wedge 5a, but it does not pass therethrough. It carries at its upper end, the flywheel which is not rigidly connected to the spindle and which can be coupled to the spindle by means of the slip clutch 11a. The clutch 11a is similar to and functions in the same manner as clutch 11 and the details thereof are illustrated in FIG. 4. It is possible to provide a motor 12a driving the connectable flywheel. A hydraulic piston and cylinder arrangement 15 is provided on the side of the press head 4a opposite the flywheel, the piston rod of which is connected to the wedge 5a and which serves to displace the wedge not only to the right but also to the left with the displacement to the right causing a downward movement of the ram 2a.

A power press in accordance with FIG. 3 is likewise constructed to a large extent in a manner similar to a press in accordance with FIG. 1. What is different is that instead of a motor engaging at the spindle 7b in a non-releasable way, there are provided two piston-andcylinder arrangements 16 arranged on both sides of the wedge 5b with the arrangements 16 serving to displace the wedge 5b. It is possible in this embodiment to arrange that the contacting surfaces of the wedge and ram lie not horizontally but run in a sloping manner, with the spindle 7b being arranged horizontally. Surfaces, which run in a sloping manner, between the ram and wedge, however, have the disadvantage that considerable forces come to bear on the ram guide, namely the horizontal press force components against the respective surfaces. In this embodiment, the flywheel 10b and slip clutch 11b are similar to the flywheel and slip clutch illustrated in FIGS. 1 and 4. The cheeks 13b are of the type shown in the brake 13 of FIG. 1.

In the ideal case, the slip clutch should be fully separated directly at the beginning of the slipping. The impulse to separate can, however, only be given if the slipping has already begun, so that in practice the separation takes place delayed in time with respect to the beginning of the slipping. One possibility of triggering the separation of the slip clutch consists in that a contact finger mounted on the flywheel is pressed with spring force against a counter disc. The counter disc, which is connected to the spindle, possesses in the circular movement zone of the contact finger, a plurality of cam-shaped projections. When the contact finger slides over these projections, the inpulse for separation arises. Another possibility of separating the slip clutch consists in that the switch impulse is given electronically by frequency comparison.

The switchable slip clutch shown in FIG. 4 is suitable for a power press in accordance with FIG. 1. In accordance with FIG. 4, an end piece 17 of a spindle is guided in a cavity provided in a press stand 16', with the end piece 17, rigidly carrying a clutch disc 18in the cavity. On the end piece 17 a loose flywheel 19 is rotatably provided and which flywheel projects from the cavity and carries an anchor disc which is axially displaceable but non-rotatable relative to the flywheel 19, and which is arranged parallel to the clutch disc 18. A friction lining 21 is provided between the clutch disc 18 and the anchor disc 20. Disc rollers 22 (of which one is shown) are provided between the two

discs

18, 20 in chamber 24.

The loose flywheel 19 is driven via a shaft butt 23, by an electric motor 12, which is secured, by means of a web 25, to the press stand 16'. Between the loose flywheel l9 and the anchor disc 20 compression springs 26 are provided which are biased to press the anchor disc 20 against the clutch disc 18. On the anchor disc 20 there is accommodated an annular anchor 27 which embraces the loose flywheel l9 and is axially displaceable thereon. If the anchor disc 20 is pushed back against the pressure of the compression springs 26, the annular anchor 27 is located inside a system of magnets 28, which is provided on the press stand 16'.

When the clutch is released, the disc can turn together with the loose flywheel 19 around the end piece 17 but it is also movable axially. If the clutch is engaged, then the anchor disc is pressed with the lining 21 against the clutch disc 18.

In the clutch disc 18 are provided recesses 18a into which part of the rollers 22 project with the rollers being adapted to rotate on shafts 22a attached to the clutch disc 18. The part of each roller 22 opposite the disc 18 projects into the chamber 24. The cross-section of the chamber 24 tapers toward the right hand side of the disc 20 or, in other words, the chamber 24 is in the shape of a trough. As soon as the anchor disc 20 rotates somewhat, the roller 22 rolls out of the chamber 24 and presses the anchor disc towards the right (FIG. 4).

In accordance with FIG. 5, the system of magnets 28 is located via a switch 29 on two voltage carrying-leads 30a. 30b. The switch 29 can be actuated by means of a relay 29a which can be connected to the voltage supply via a switch 31 and/or a limit switch 32. The limit switch 32 is, in accordance with FIG. 1, provided on the press stand 1 in the vicinity of a cam 32a which is accommodated on the ram 2. The power press forward motion can be switched on by a switch 33, which is actuable by hand and a relay 31a is connected to the voltage supply, with the relay actuating the switch 31. Finally, there is provided a switch 34 via which a relay 340 can be connected to the voltage supply and the return motion of the press can be switched.

When the ram 2 travels downwards, then the forward motion switch 33 is closed and the switch 31 and the limit switch 32 is opened so that the switch 29 is opened and the system of magnets is not energized. The anchor disc 20 is pressed by the compression springs 26 against the clutch disc 18. In good time before the lower dead point, i.e., before the ram 2 comes into contact with a work piece, the limit switch 32 is actuated so that the system of magnets 28 is energized. As soon as the adjusted nominal moment of the slip clutch is attained during the forming of the work piece or in the case of a rebound impact, the rollers 22 are released from the chambers 24 and press and the anchor 27 into the system of magnets 28 so that the slip clutch is released. Since the anchor 27 is held firmly by the system of magnets 28, the clutch remains released. If the return motion of the press ram 2 is switched on, the switch 33 effecting the forward motion is opened so that the switch 31 closes itself, by which the system of magnets 28 is energized during the whole return motion and holds the slip clutch in the released state. If, then, it is again switched over to forward motion, i.e., the switch 33 is closed the switch 31 opens and, since the switch 32 is also opened, the system of magnets 28 becomes demagnetized so that the slip clutch can engage under the action of the compression spring 26.

What we claim is:

1. A power press comprising a press head, an anvil, a ram for upward and downward movement relative to said anvil, and drive means for said ram, said drive means including a spindle, a flywheel, a switchable clutch connecting said flywheel to one end of said spindle, a motor operably connected to said flywheel and continuously rotating in one direction, and a second motor operably connected to the other end of said spindle, said second motor being reversible, whereby when said clutch is engaged said continuously rotating motor moves said ram in the direction of impact and said ram is moved only by said reversible motor when said clutch is disengaged.

2. A power press as claimed in claim 1, wherein said switchable clutch is a slip clutch, and said second mentioned motor is actuated after an acceleration period of said spindle after being activated by engaging said clutch.

3. A power press provided with a press head, an anvil, a ram for upward and downward movement relative to the anvil, and a drive device for the ram including a spindle and a flywheel connectable to the spindle, the improvement including a motor operably connected to the flywheel, said motor running in a single rotational direction, and a switchable slip clutch having frictional surfaces between the flywheel and the spindle so that at the beginning of slip, the frictional surfaces are completely separated from each other and remain separated during the return motion.