DE4013295A1 - Threaded spindle drive with safety cut=out - has plate spring packet operating cut=out switch via axial displacement spindle - Google Patents

Abstract

The spindle drive has a rotary nut (11) attached to the spindle (6), coupled to a piston rod (12), or a carriage etc., for linear reciprocation of the latter in response to the spindle rotation. A plate spring packet (10) between the spindle (6) and the drive housing, is used to operate a safety cut-out switch (17( for the spindle drive motor (0), in response to its axial movement. Pref. the switch (17) is mechanically, electrically, or electronically continuously adjustable. ADVANTAGES - Prevents damage to drive upon exceding permissible stroke.

Description

introduction

Spindle drives are drive or movement elements, with linear with those with optional forces and velocities Driven paths and in circular or other geometric Movements can be implemented.

Spindle drives are preferably used where on a elaborate hydraulic system should be dispensed with where pneumatics either too weak or because of its compressibility it is too indefinable where self-locking is required and where Accurate intermediate positions, especially under load should be.

In contrast to fluidic movement elements, where in the event of overload or collision with the front or rear end position and if the pressure is not switched off and thus the force is applied damage or destruction of the system (e.g. Cylinder) or the element or device to be moved an intermediate pressure limitation is avoided mechanical spindle drives, driven by electric motors, the risk of the engine blowing, if the system is exposed to an overload and the motor is not switched off in time.

If the drive motor is not switched off in time in the end positions, runs back and forth from the threaded spindle moving nut on the front or back of the device housing and wedged in the threads of the spindle. This can also lead to damage or destruction and requires disassembly of the device to remove the mother from her To be able to solve the wedging again.

Spindle drives with a right and left rotating Drive nut with a piston rod, a driver or a carriage, etc., is driven by an electric motor are preferably via internal or external Limit switch switched off and on.

These limit switches do not register an overload, however just switch off at a predetermined position.

Advancement

To prevent internal and external damage or destruction, is a safety shutdown in the end positions and offered during the entire movement sequence or stroke, with this requirement taking into account that the basic dimensions the device does not experience any changes and full use of these basic dimensions the stroke or the movement path is guaranteed.  

State of the art

Various safety shutdowns are known, however too expensive or too slow in their function or in their construction is too complicated and the basic dimensions, or influence the full stroke or path use.

Solution according to the invention

The invention is based on a construction in which the threaded spindle via a disc spring package, which on the one hand opposes the threaded spindle, on the other hand, supports against the device housing, is rotatably and axially displaceable back and forth.

The displacement path becomes mechanical or inductive or optical, etc. the lead screw on mechanical, electrical or electronic Switching and control devices that transmit the drive motor switch off or toggle.

The switching and control devices are preferably infinitely adjustable, so that depending on the travel, a pre-determined, force-displacement-related shutdown is possible.

Because with increasing spindle speed and thus increasing Acceleration of the drive nut and thus the piston rod, of the driver or the carriage after actuation of the switch-off element the braking distance is longer and therefore the position accuracy what gets worse from the acceleration of mass compared to the diaphragm spring package, if provided in the End positions and also in intermediate positions a high positioning accuracy is required, the speed of the drive motor before the actual shutdown information and in any selectable distance throttled. The command to throttle takes place either via internal or external sliding limit switches or electronically selectable.

Speed reduction is preferred for DC motors due to voltage reduction for three-phase and single-phase motors by switching poles (4/2 Dalander switching).

If the engine speed is to be kept constant, then the Speed reduction between the electric motor and threaded spindle a change gearbox mounted, based on the specified Positions infinitely variable to the required gear ratios switches down and thus a speed reduction of the threaded spindle takes place.

If you want to move axially against yourself Dispense with the diaphragm spring package supporting spindle construction, this is how a hydraulic system becomes between the drive motor and the threaded spindle mounted, which essentially consists of an electric motor driven oil pump and a driving the threaded spindle Oil engine exists. Via pressure relief valves and Flow control valves become maximum motive force, shutdown force  and regulates and determines speed.

Description - Fig. 1 to 6. Fig. 1

An electric motor ( 0 ) is connected to a flange ( 1 ) which is screwed to a housing tube ( 2 ) which carries a piston rod guide ( 3 ) on the head side.

The motor shaft ( 4 ) rotates a threaded spindle ( 6 ) via a coupling ( 5 ), which is rotatably and axially displaceably mounted in the bearings ( 7 ).

The bearings ( 7 ) are supported on the collar ( 8 ) on the threaded spindle ( 6 ) via the disc spring assembly ( 10 ) against the flange ( 1 ) on surface "A", and on the other via the ring ( 9 ) on the threaded spindle ( 6 ) from the disc spring assembly ( 10 ) against the flange ( 1 ) on surface "B".

A piston ( 11 ) runs on the threaded spindle ( 6 ) and has a thread in its bore similar to that of the threaded spindle ( 6 ) and thus has the function of a drive nut ( 11 ). This piston ( 11 ) is connected to a piston rod ( 12 ) in the form of a tube and is secured against rotation via a guide rail ( 13 ). In this case, the piston ( 11 ) is provided with a groove which runs in the guide rail ( 13 ). Instead of a guide rail ( 13 ), the housing tube ( 2 ) can be equipped with sigens ( 14 ) directed inwards. The piston ( 11 ) then has longitudinal recesses that run in these siggen. With square tubes ( 2 ) or other profiles, the inner contour of which is adapted to the piston ( 11 ), an additional anti-rotation lock is not required.

The piston ( 11 ) is equipped with one or more permanent or electromagnets ( 30 ) for actuating switches placed on the housing tube ( 2 ).

Between the bearings ( 7 ) and the plate spring assembly ( 10 ) there are axially moving switching rings ( 15 ) which actuate switches ( 17 ) via switching fingers ( 16 ). The switches ( 17 ) are axially displaceable. A switch ( 17 ) is for the switch-off process in the forward flow, a switch ( 17 ) is separate for the switch-off process in the return flow, to be adjusted manually or via adjustment spindles or via electrical adjustment devices.

Fig. 2

Instead of the axially moving switching rings ( 15 ), a switching segment ( 18 ) is pivotally mounted in the flange ( 1 ) at the pivot point "C" to the left and right. The lower end of the switching segment ( 18 ) is designed as a ball finger ( 19 ) which engages in the groove of a driving ring ( 22 ) which moves axially and radially with the threaded spindle ( 6 ). Switching cams ( 20 ) which can be displaced and braced are arranged on the switching segment ( 18 ) at the top and act on switching elements ( 21 ) which are fixedly mounted.

Fig. 3

Instead of switching rings, switching fingers, cams or other mechanical elements transferring the displacement movement of the threaded spindle ( 6 ) to switches, the displacement path can be transmitted to strain gauges, longitudinal travel potentiometers ( 23 ) etc., which are coupled to an electronic control unit ( 24 ).

Fig. 4

If mechanical motion transmission is dispensed with, the threaded spindle shaft ( 25 ) is provided, for example, with a ( 26 ) vernier, which is preferably optically scanned. The scanning sensor ( 27 ) counts, for example, the graduation marks traveled within a movement path and passes this count on to the electronics for further use.

Fig. 5

As already described in section 60 to 85, is at high spindle speeds and thus high feed speeds for the purpose of optimal positioning accuracy after initiating the shutdown process, a speed restriction required before the switch-off process is initiated.

If the switch-off position is known, for example in the end positions or at precisely defined points on the movement path to be traveled, additional switches ( 29 ) or without a switch can be used at any point before the switch-off point when using longitudinal travel potentiometers or nonies, etc. via the electronics of the Switching process to be started at a low speed.

The speed is reduced by reducing the voltage or changing the pole on the drive motor ( 0 ).

Fig. 5 shows an example of a solution to the speed reduction without that the electric motor has to be throttled. Electric motor ( 0 ) and threaded spindle stub ( 33 ) are connected via a synchronized reduction gear ( 34 ) in such a way that the displacement path of the threaded spindle ( 6 ) is used to change the ratio or reduction ratio. The speed change is infinitely analogous to conventional, infinitely variable transmissions.

Fig. 6

If you do not use a movable threaded spindle in the axial direction and still want to have a safety shutdown at any point in the end positions and over the entire and over the entire travel path back and forth, the electric motor ( 0 ) and threaded spindle ( 6 ) a hydraulic system ( 35 ) interposed.

The electric motor ( 0 ) drives an oil pump ( 36 ) which is located in an oil-filled housing ( 37 ). The oil flow passes through chambers or supply line ( 38 ) via a pressure relief valve ( 39 ) and a flow control valve ( 40 ) to the oil motor ( 41 ). To change the direction of rotation, either the direction of rotation of the electric motor ( 0 ) is changed or the oil flow is fed to the opposite side of the oil motor ( 41 ) via a 4-way valve ( 44 ).

Functions

The drive nut ( 11 ) attached to the axially displaceable threaded spindle ( 6 ) moves a piston rod ( 12 ) connected to the drive nut ( 11 ) or a slide or driver ( 32 ).

If a counterforce is opposed to the piston rod ( 12 ) or the slide or driver ( 32 ) in the front or rear end positions or in any position within the travel distance, the axially displaceable threaded spindle ( 6 ) presses the disc spring assembly ( 10 ) against the fixed housing - in the case shown, against the fixed flange ( 1 ).

The greater the counterforce, the more the disc spring assembly ( 10 ) compresses and the greater the displacement of the threaded spindle ( 6 ).

Since the spring travel and thus the displacement path to a finite number of forces acting on the piston rod ( 11 ), the slide or the driver ( 32 ) can be brought into a mathematical relationship, it is possible to determine which counter force is pending for which spring travel.

These determined values are used for the predetermination of the Switch-off point used.

If, for example, the spring assembly ( 10 ) compresses by 3 mm at a counterforce of 5000 N, by 5 mm at a counterforce of 10,000 N, the switch ( 17 ) which triggers the switch-off process becomes at a desired switch-off force of 10,000 N 0 mark shifted to mark 5, provided the gear ratio is 1: 1. Since separate switches ( 17 ) are installed for the supply and return, the supply and return force can be set separately and differently from one another.

When using the switching segment ( 18 ), the switching cams ( 20 ) are displaced, the displacement path of the switching cams here being analogous to the transmission ratio of pivot point "C" to point of engagement ball finger ( 19 ) in the driving ring ( 22 ) and pivot point "C" to radius of switching cams "R" , for example 1: 3, which means that with a displacement of the threaded spindle ( 6 ) of 5 mm, a displacement of the switching cams ( 20 ) of 15 mm is to be carried out. This gives a higher setting accuracy.

If, for example, a longitudinal travel potentiometer ( 23 ) is used, which is mechanically coupled to the moving threaded spindle ( 6 ), the retracted wiper position of the longitudinal travel potentiometer ( 23 ) corresponds to a situation in which the threaded spindle ( 6 ) is axially at rest, that is , theoretically there is no counterforce in the axial direction.

When a counterforce occurs, the threaded spindle begins to move axially and consequently takes the slider of the longitudinal travel potentiometer ( 23 ) with it. This changes a voltage applied to the longitudinal path potentiometer. This voltage or resistance change is registered by a downstream electronics ( 24 ).

The electronics are equipped with an actual-target comparison system. Using separate trimmers for forward and reverse accordingly, the counterforce at which the shutdown process is specified should be initiated. The adjustment is stepless. Instead of trimmers, you can also use a keyboard to select the desired one Switch-off force can be selected. This can also be on different path positions programmed in different sizes will.

If the displacement path is scanned and registered without contact, for example via a vernier ( 26 ) attached to the displacing threaded spindle shaft ( 25 ) by means of a sensor ( 27 ), the graduated lines on the vernier ( 26 ) are counted by the sensor ( 27 ) and in the Electronics recycled. The adjustment is carried out analogously to the technique described when using a longitudinal path potentiometer, only that counting pulses are implemented instead of a voltage or resistance difference. The same applies to specification and programming.

If an intermediate hydraulic system ( 35 ) is used, in which an oil pump ( 36 ), driven by the electric motor ( 0 ) drives an oil motor ( 41 ), the desired shutdown force is set at the pressure relief valve ( 39 ). Since the required oil pressure is proportional to the force opposing the piston rod ( 12 ) or driver or slide ( 32 ), the minimum and maximum pressure to be driven can be registered, set and switched off via a contact pressure gauge ( 42 ) etc. connected upstream of the pressure relief valve Electric motor are evaluated. You can also do without switching off the electric motor and bring the oil flow into an unpressurized circulation via an auxiliary valve ( 43 ). However, the primary safety basis is always the pressure relief valve ( 39 ), which returns the pressurized oil flow to the tank ( 37 ) according to its setting. If the force opposing the piston rod, the driver or the slide exceeds a value set on the pressure relief valve, this will blow off the pressurized oil flow and the threaded spindle ( 6 ) will no longer rotate.

This variant also has a safety shutdown Validity in forward and reverse and in connection with described electrical or electronic switching and  Control elements is also a shutdown in any path positions possible.

At high speeds of the threaded spindle ( 6 ) and thus high feed speeds, the speed of the electric motor ( 0 ) is throttled to a lower speed before the actual switch-off process. This process has already been described. This restriction is not necessary when using a hydraulic system, since the speed of the pressure rise is proportional to the counterforce that occurs.

Claims (5)

1. Safety shutdown, characterized in that a motor-driven threaded spindle, which has a non-rotatably mounted drive nut, connected to a piston rod, a driver or slide, moves linearly back and forth or back and forth, via a plate spring assembly, which is against the threaded spindle and supports the machine housing, is mounted so as to be axially displaceable in a radially rotating manner, and transmits this displacement path mechanically or without contact to switching and control elements. 2. Safety shutdown according to claim 1, characterized in that all switching and control elements, the mechanical or contactless the displacement register the threaded spindle, mechanically, continuously adjustable electrically or electronically and both in the front and rear end positions, as Switch-off and switchover functions also at any path position trigger, internally or externally mounted are. 3. Safety shutdown according to claim 1 and 2, characterized characterized that preferably at high threads spindle speeds and thus high movement speeds in any position internally or externally adjustable switches are installed that a switching process to a lower speed and therefore lower movement speed for the purpose perform optimal positioning accuracy. 4. Safety shutdown according to claim 1 to 3, characterized characterized in that a speed reduction is optional through a between the drive motor and threaded spindle assembled by the axial movement of the threaded spindle changing in the gear ratio Transmission, is carried out continuously. 5. Safety shutdown according to claim 1 to 4, characterized characterized in that instead of an axially displaceable Threaded spindle and the associated Construction and switching between drive motor and axially rigid threaded spindle a hydraulic unit consisting of the drive motor driven oil pump and by this driven oil motor with intermediate Pressure limiting and flow control valve installed is, one installed before the pressure relief valve Pressure registration element, or a contact manometer infinitely adjustable switching impulses or provides information that or switching the drive motor or for switching of the oil pressure system to pressureless circulation be used.