DE1210290B - Hydrostatic transmission for alternating movements - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

F06h

German class: 47 h -18

Number: 1210 290

File number: W 30437 XII / 47 h

Filing date: July 29, 1961

Opening day: February 3, 1966

The invention relates to a hydrostatic transmission for alternating movements, in particular for linear alternating movements in machine tools, in which the generating the alternating movements alternating hydraulic motor with a pump with adjustable delivery rate via a reversing device is connected, via one of a pressure medium auxiliary source of constant flow rate fed and controlled by a pilot valve pressure medium auxiliary circuit can be actuated, the The pilot spool is adjusted depending on reversing pulses, which are selected when reaching the preselected Reversal points of a part participating in the alternating movements are triggered.

Such transmissions are known. In many applications it is desirable to adjust the feed rate adapt the hydraulic working piston to the respective working conditions by changing the delivery rate of the pump. Frequently the speed is different in the two stroke directions. On the other hand, it is necessary that Reversal of the working piston at least at one end of the stroke, regardless of the respective feed speed to be controlled so that the standstill of the machine parts participating in the changing movements always and very precisely takes place at the same predetermined point.

In the case of transmissions of the type mentioned at the beginning, the reversing pulse is triggered always at the z. B. by setting a sensor certain same point of the stroke, namely regardless of the respective feed speed of the hydraulic working piston. To with these However, to reach standstill at the same point when driven, the deceleration resp. Re-acceleration of the working piston during the switching process in each case as a function of the normal working speed of the working piston that has just been set.

These relationships are illustrated in Fig. A, in which the speed-displacement curve of the working piston is shown in the area of a reversing point. The ordinate of the diagram shows the speed ν and the abscissa s the stroke of the working piston. This is how the controlled reversal point should be, while the reversal pulse is triggered _{at S 1.} In the case of curve I, the working piston has the maximum permissible working speed V ₁ . When the point ^ is reached, the reversing process is triggered, so that the working piston is braked with a constant delay according to the line la until it is in. Hydrostatic gear for alternating movements

Applicant:

Hydrel A. G., Romanshorn (Switzerland)

Representative:

Dipl.-Ing. F. Thieleke, Dr.-Ing. R. Doering
and Dr. J. Fricke, patent attorneys,
Munich 2, Josephspitalstr. 7th

Named as inventor:

Fritz Wegerdt, Weingarten (Württ.)

Point S ₀ comes to a standstill. From here the re-acceleration takes place in the opposite direction. In curve II it is assumed that the working piston has the much lower working speed v ₂ . In this case, too, the reversal pulse is triggered again at point S _1.

So that the working piston comes to a standstill at point S _{0 even at this working speed,}

the deceleration of the working piston must be significantly less in this case than in the case of curve I.

If a specific reversal point on the stroke path is not controlled, the deceleration and acceleration of the working piston can of course be chosen to be constant regardless of the respective working speed, as shown in FIG. B is indicated in curves III and IV. One accepts that at different working speeds the point at which the working piston comes to rest is at a different point on the stroke path for each working speed, as indicated by the reversal points S ₂ and S ₃ for curves IV and III in F i G. 2 is indicated.

From the Fi g. A and B one recognizes that one is at

the known gearboxes of the type specified above either the braking and acceleration forces for the working piston and those driven by it Change parts depending on the feed rate or always on compliance and must do without the same turning point.

It is the object of the invention to develop a hydrostatic transmission of this type so that it is independent the deceleration or re-acceleration of the Working piston is always constant, but still the

609 503/197

3 4

Umkehφunkt the alternating movement always at the sen piston remains synchronous with the working piston the same point of the stroke and moved with great and the two common switching device accuracy can be controlled. tang operated. In order to make the task of the invention even more clearly shifting the triggering command point to a, reference is made to FIG. In 5 another element of the transmission. The processes, which these represent the curves V and VI again slide after this command, are not influenced by the hiergrams for the different working speeds. Finally, there are also dities V ₁ and V _{2 of} the working piston. S ₁ is known to the sensor, which is the trigger pulse at the trigger point for the reversing pulse, while S ₀ interacts with the working piston or one of the controlled invariable reversal point. OK with this moving part, omit and in order to be able to delay or accelerate the working piston independent of the respective working speed, the triggering by an electrical time relay can be delayed or accelerated at the beginning of the working stroke, it is necessary to switch the constant one and after the set time movement of the working piston has elapsed during its normal period, it gives the trigger pulse. Here, too, the painting stroke at all working speeds, the 15 time relays have no influence on the sequence of the reversing processes occurring after the triggering is slower than the maximum working speed. The ratios according to curve V are to be extended beyond the trigger point S ₁ in this known arrangement until the working piston has just reached particularly sensitive to changes in the constant delay line Va. For advancing speed of the working piston.
the curve VT this point is denoted by VIa. In contrast to the known gears, from Fig. C it can be readily seen that a hydrostatic gearing operating according to the diagram shown after the reversal pulse has been triggered when the pulse is applied to the timing relay in the case of the gearing according to the invention the reversal of all working speeds that are smaller than the device to be controlled, namely depending on the maximum permissible working speed according to the respectively selected feed speed curve V, a considerable gain in work in the more or less to delay. The respective support area brings the reversal phase with it. For the amount of the working pressure medium source, the case of curve VI in FIG. C is the gain in working speed of the working piston. A one in the position of the time constant between the points ^ and S _{0 Hegenden inversely proportional reversing phase shown hatched.} 30 to the delivery rate of the working pressure medium source

This object is achieved according to the invention so indicates that the time constant at the maximum

by an operating speed that can be switched on by the reversing pulse (curve V in FIG. C)

Time relay and one reversed to the delivery zero, so that immediately after triggering the reversal

quantity of the pump adjustable (adjustment device control pulse at point S ₁ the constant delay

tungi?) time constant. This causes the connection of the working piston to begin, as is the case with the

tion between the Druckmittelhüfsquelle and the line V α is indicated. Depending on the work

Reversing device is only after the speed has elapsed, the greater the time con-

set delay time of the timing relay released stante of the timing relay, so that the delay always

will. Advantageously, the timing relay only starts when the normal working curve

a hydraulic timer, the pressure 40 intersecting the constant deceleration curve Va (point

Funds supplied to the timer by the pre-tax VEa). This means that the requirements set out above

slide is controlled. ments by the teachings of the present invention

The use of timing relays, even those with met.

pressure medium-fed timer is known per se. The delay times are usually great So it is 45 small (less than a second) with compressible pressure medium. It has therefore proven to be known bar gear for forging hammers, which proved to be particularly beneficial when you have a time impact of the hammer on the workpiece da- relais with hydraulic timer used, whereby by changing the duration of the input the Draclanmittelzufuhr to the timer by the Time of action of the driving pressure medium on the urine pilot valve can be controlled. The size mer changes by means of an electrical timing relay. The 50 of the time constant of the timer can mean two things The reversal point and the deceleration of the hammer can be influenced in a manner; first of all, a die However, this is exclusively due to the length of the time stroke of the hydraulic timer hitting the hammer on the forging is determined. defining stop provided for the rest position

In another case, an electrical time is used, which depends on the flow rate of the Relay for this, the dwell time of the hydraulic Ar- 55 main pump can be adjusted. On the other beitskolbens to determine at the reversal point, and side you can ensure that the Speizwar, in order to reduce the pressure of the timer from another auxiliary pump in a forging press when the stroke end position is reached for a previous one, the delivery rate of which is determined by the respective delivery rate Maintain time span. Again, the main pump's amount is proportional. Both measure the time relay has no influence on the acceleration 60 can be taken individually or advantageously inclination and delay of the working piston and apply to jointly.

the exact adherence to a predetermined reversal - the timer can only one of the two reversal point, be assigned points. In those cases where on

In another known transmission, the two reversing points require precise control-reversing pulses is not caused by the working piston 65, it may be appropriate to use both reversing or triggered by this moving parts. Rather, the working piston is each given a timing relay the movement of the working piston in a map, the time constants depending on the hydraulic clock cylinder simulated, the different speed on the working

and the idle stroke of the working piston can be different. The timing mechanisms are supplied with power both timing relays from a common pressure medium source, controlled via the common distributor piston.

The invention is applied in the following to a reciprocating piston engine which executes linear movements shown. However, it is readily apparent that they are also used in hydraulic motors reversible rotary motion can be applied. In the drawings, the same parts are used for the same parts Reference numerals used.

The invention is illustrated below with reference to schematic drawings of two exemplary embodiments explained in more detail.

F i g. 1 shows a first exemplary embodiment of a hydrostatic transmission in which the teaching according to FIG the invention has been applied;

F i g. 2 shows a second embodiment in which the piston of the reciprocating piston engine has a differential effect is working.

The embodiment according to FIG. 1 shows a hydrostatic motor in the form of a thrust piston motor with working piston K ₁ , with piston rods extending out on both sides, which move a table T with reversing cams T ₁ , T ₂ , which interact with a pulse generator G.

In the example shown, a continuously reversible hydrostatic pump AP, for example of the radial piston type, serves as the operating pressure medium source. Such pumps are known and need not be described. Pump AP and working piston K ₁ are connected by main lines 1 and 2. A reversing valve with reversing piston K _s serves as the switching device for the pump , the protruding piston rods of which interact with stops A ₁ , A ₂ that can be adjusted by adjusting wheels R ₁ , R _2.

The reversing spool with reversing piston K ₃ is fed with a constant flow rate from a gear pump ZP , the pressure line 6 of which optionally connects to the feed lines 7 and 8 via a pilot spool with pilot piston K _2. The pilot valve also controls the outflow of the pressure oil from the lines 12 and 13 of the reversing valve into the sump 0. The switching of the pilot piston K _{2 of} the pilot valve takes place via the release device G ₁ electrically, hydraulically or, as shown, mechanically.

In both feed lines 7 and 8 of the reversing piston J ^ _{3 , a timing piston Z 1} , Z ₂ controlled by a timing relay is arranged, which releases the pressure medium supply to the reversing piston after the timing relay has expired. The example shown is a time relay with a hydraulic timer. The timer has a time piston — Z ₁ and Z ₂ —which is biased into its rest position by a spring Fd ₁ or Fd _2. This rest position is determined by a stop Sp ₁ and Sp _{2 in} each case. In the example shown, the right-hand timing piston Z _{1 is} in contact with its stop Sp ₁ and is thus in the starting position. Each time piston also serves as a valve slide and for this purpose has an annular groove E ₁ or E ₂ which, when the piston reaches the end position W, establishes a connection between the feed line 7 or 8 and the reversing cylinder, as is the case for the time piston Z ₂ is shown. The running time of the piston from its adjustable rest position to its end position, in which it releases the connection, represents the time constant of the timing relay.

For the inevitable adjustment of the time constant inversely proportional to the adjustment of the delivery rate of the working pressure medium source, a gear connection between the setting mechanism R ₁ and R ₂ for the stops A ₁ and A _{2 of} the reversing

piston K ₃ and the setting mechanism for the stops Sp ₁ and Sp _{2 of} the timer.

It is advisable to ensure that the timers are fed from a pressure medium source, the delivery rate of which changes proportionally with the delivery rate of the main pump. For this purpose, in the example shown, a hydrostatic control pump SP with a continuously variable flow rate is used to feed the timers, the flow rate regulator V of which is directly connected to the flow rate regulator of the main pump, so that the flow rate adjustment of both pumps always takes place in the same sense and to the same extent. In order to ensure that this control pump SP always delivers into the same pressure medium line 3, a floating piston S with associated check valves is arranged between the two outlets of the pump.

It is readily apparent that at maximum delivery rate of the main pump AP the associated stops Sp ₁ and Sp ₂ of the timers are pushed so far into the cylinder space that the time pistons Z ₁ and Z _{2 are} in the stop at their end position W. In this position there is not only a free connection between the gear pump ZP and the reversing piston K ₃ , but the pressure medium supplied by the control pump SP can also flow freely through the drainage openings released by the time piston, so that the pump operates without pressure.

In the illustrated phase of the hydraulic transmission, the working piston K ₁ moves to the right at a constant speed. The timing piston Z ₂ maintains the connection to the reversing piston via the line 10 so that the reversing piston K _{3 is held} in its right-hand position. As soon as the stop T ₁ actuates the pulse generator G, the pilot piston K _{2 is switched} from the position shown to its other position. The line 8 is connected via line 12 to the sump 0 and the line 7 to the pressure line 6. The connection between line 7 and line 9 is still _{blocked by the time piston Z 1} , so that the working piston K ₁ continues to move at a constant speed in the previous stroke direction. When the piston K _{2 of} the pilot valve is switched over, the line 4 for the timing piston Z _{1 is also} connected to the pressure line 3 of the control pump SP . The timer then begins to run in that the cylinder space in front of the piston surface of the timer piston Z _{1 is} filled with pressure medium via the line 4. After the time constant has elapsed, ie as soon as the piston Z _{1 reaches} the fixed stop W , the connection between the lines 7 and 9 is released through the annular groove E ₁ , while the pressure line 4 is connected to the drain. At this moment the reversing piston K ₃ begins to reverse the main pump, the working piston K ₁ with a constant delay

is braked. As soon as the primary control piston has reached its central position, the working piston K _{1 has reached} the desired reversal point. With a further movement of the reversing piston K ₃ , the power of the main pump increases and the result is a constant acceleration of the working piston K ₁ up to the constant speed value determined by the stop A _2. The stops A ₂ and A ₁ determine not only the output of the main pump but also the work output of the control pump.

In the embodiment according to FIG. 2, the piston rod of the piston K _{10 of} the reciprocating piston motor is guided outward on one side and moves upright. The working surfaces of the piston that are effective during the two strokes are of different sizes.

In the example shown, the actual working stroke should be directed downwards, as indicated by the arrow. In order to be able to perform the return stroke at increased speed, a check valve RV _{1 is provided in the piston Z 10} , which can open in the direction of the smaller piston area F ₁ . This ensures that when the working medium flowing in the pressure line 2 acts on the larger piston area F _2, the two piston sides are connected through the check valve RV ₁ , so that only an area of the cross-sectional dimension of the plunger of the piston is effective during the return stroke. Such a valve connection can also be provided outside the working piston directly between the two lines 1 and 2.

The piston Z of the timing relay, reversing piston K ₃ , pilot piston K ₂ and main pump AP work together essentially in the same way as in the transmission of FIG. 1 with the difference that the timing relay is only effective when reversing at the end of the working stroke.

In the present example, a special auxiliary pressure medium source can be dispensed with to feed the timing relay. Rather, the excess amount of the pressure fluid emerging from the working cylinder through line 2 during the working stroke is used to feed the timing relay. During the normal working stroke, this is conveyed into the sump 0 via the check valve RV ₁ , line 3, line 4 in the cylinder of the feed piston Z _4. Since the working piston K _{10 of} the thrust piston motor always moves beyond the trigger point _{S 1} (see Figs. A to C) of the reversing pulse at a constant speed at all working speeds that are lower than the maximum speeds, there is still no after switching of the pilot piston K ₂ the illustrated in the other position still sufficient excess pressure oil in the line 2 is available. After the pilot piston Z _{2 has been switched} over, this oil is conveyed via the non-return valve RV ₁ , line 3 and line S into the timing relay with the timing piston Z in order to set it in motion. In order to ensure that the pump can still suck in enough when it passes through the zero position and that the working piston is constantly re-accelerated, the excess oil in the feed piston Z _{4 is} additionally supplied to the main pump AP in this position, namely by the fact that when switching Des. Pilot piston K _2, the line 4 is brought to the intake line 13 in connection.

Since the return stroke of the working piston takes place at increased speed in the example shown, a special measure is provided to limit the acceleration of the working piston to the increased speed to the same value that is also provided for the other accelerations and decelerations (line Va in Fig. C).

ίο These measures consist in that the pressure line of the leading ₃ Umsteuerzylinders opens on the left side of Umsteuerkolbens K at a point 11 which corresponds to the position of his left side of the piston K ₃ in the zero position of the main pump

speaks. A bridging line is provided for this line, which opens into the end of the cylinder at 12 and which has a throttle Dr , which accelerates or decelerates the reversing piston K ₃ during its movement in

Unken part of the cylinder is limited to the desired value.

Otherwise, the mode of operation of the arrangement according to FIG. 2 essentially the same as that the arrangement according to FIG. 1, so that a further explanation is not necessary.

The invention is applicable with the same advantage also in the cases where the main pump is not reversed above zero, but a reversing slide serves as a reversing device, which is arranged between the pump and the working motor and the pump lines in its two slide positions alternately connects to one or the other side of the piston. In these cases, that controls Time relay the pressure medium circuit that actuates the reversing spool.

Claims (11)

Patent claims: 1. Hydrostatic transmission for alternating movements, in particular for linear alternating movements in machine tools, in which the hydraulic motor generating the alternating movements is alternately connected to a pump with an adjustable flow rate via a reversing device, which is fed by a constant flow rate from an auxiliary pressure medium source and controlled by a pilot valve Auxiliary hydraulic circuit can be actuated, whereby the pilot valve is switched over as a function of reversing pulses which are triggered when a pre-selected reversal point of a part participating in the alternating movements is reached, characterized by a timing relay with time piston (Z ₁ , Z ₂ or Z) that can be switched on by the reversing pulse. 55, and a time constant that can be set inversely to the delivery rate of the pump by means of an adjusting device (R) , which causes the connection between the auxiliary pressure medium source (ZP) and the reversing device (K ₃ ) to be released only after the set delay time of the time relay has expired. 2. Hydrostatic transmission according to claim 1, characterized in that the time relay controls a time piston (Z) which is switched on in the connection between the pilot valve with, pilot piston (K ₂ ) and reversing device with reversing piston (K ₃ ), which normally blocks this connection. 3. Hydrostatic transmission according to spoke 2, characterized in that the time relay has a hydraulic timer and the pressure medium supply to the timer is controlled by the pilot piston (K ₂ ). 4. Hydrostatic transmission according to claim 3, characterized in that the hydraulic time relay has a displaceable in a calibrated cylinder time piston (Z ₁ , Z ₂ or Z), which is biased towards its rest position by a spring (Fd ₁ , Fd ₂ ) and can be acted upon hydraulically in the opposite direction and at the same time serves as a time-dependent valve slide for the connection between the reversing device with reversing piston (K ₃ ) and the pilot valve with pilot piston (K ₂ ) . 5. Hydrostatic transmission according to claim 4, characterized in that the rest position of the time piston (Z ₁ , Z ₂ ) is determined by a stop (Sp ₁ , Sp ₂ ) adjustable with the on-position of the delivery rate of the main pump (AP) . 6. Hydrostatic transmission according to claim 4 or 5, characterized by a control pump (5P) for feeding the hydraulic timer, the delivery rate of which is adjustable in proportion to the respective delivery rate of the main pump (AP) (Fig. 4). 7. Hydrostatic transmission according to claim 6, in which a hydrostatic continuously reversible pump is used as the working pressure medium source and a hydraulic reversing piston with adjustable end positions is used as the reversing device, characterized in that a continuously reversible hydrostatic control pump (SP) is also used to feed the hydraulic timer, the flow rate regulator of which (F) is coupled to the reversing piston (K ₃ ) of the main pump (AP). 8. Hydrostatic transmission according to claim 1 to 7, characterized in that both reversal points of the hydraulic working motor (K ₁ ) are each assigned a hydraulic time relay with time piston (Z ₁ , Z ₂ ) and the supply of the timers of both time relays from a common pressure medium source - Feed pump (Sp) - takes place and is controlled via the common pilot piston (Z ₂ ). 9. Hydrostatic transmission according to claim 6 with a linear movements executing working piston, the two alternately effective piston surfaces have different dimensions by unilaterally leading the piston rod out of the working cylinder, characterized in that to feed the hydraulic timing relay with the timing piston (Z) when the smaller working piston area during the working stroke, the excess amount of _{pressure oil flowing off from the other side of the piston (Z 10} ) of the piston engine is used (Fig. 5 and 6). 10. Hydrostatic transmission according to claim 9, characterized in that the two sides of the piston (K ₁₀ ) of the reciprocating piston motor via a check valve (RV ₁ ) which opens only to the smaller side of the piston are in connection during the return stroke. 11. Hydrostatic transmission according to claim 9 or 10, in which a reversing piston is used as a reversing device for the working pressure medium source with end positions limited by adjustable stops, characterized in that the connecting line between the constant flow pump (ZP) and the effective when switching from the return stroke to the working stroke The surface of the reversing piston (K ₃ ) opens into the reversing cylinder at a point (11) which roughly corresponds to the position of the associated piston surface in the middle position of the reversing piston, and that this connecting line has a bridging line (12) which opens into the cylinder of the reversing piston in the area of the piston end position ) with a predetermined throttle (Dr) (Fig. 5). Considered publications:
German Patent Nos. 850 838, 896 003;
U.S. Patent Nos. 2250705, 2304131,
341 1 sheet of drawings 609 503/197 1.66 © Bundesdruckerei Berlin