DE3110162C2 - Hydraulic control circuit for controlling a device for butt welding plastic pipes and / or plastic fittings using the heating element method - Google Patents

Abstract

The invention relates to a device for butt welding plastic pipes and / or plastic fittings using the heating element method. It is important that the plastic parts are brought into a pressing position after the plasticizing of the connecting surfaces, the pressure increase up to the pressing pressure having to run through a certain time-pressure characteristic curve in order to obtain a perfect welded joint. This is achieved according to the invention in that the switching valve in the switched-off position connects at least the pressure line of the pump with the control line leading to the working chamber of the hydraulic cylinder, that a pressure accumulator and a manometer with a switching contact that can be adjusted to the desired pressure are permanently connected to the pressure line, and that the electric motor of the pump can be switched on by means of an additional push-button switch and can be switched off again when the predetermined pressing pressure is reached.

Description

31 1Ö 162

The invention relates to a hydraulic control circuit for controlling a device for butt welding plastic pipes and / or plastic fittings according to the heating element method, in which at least two clamping devices with the ones specified therein Plastic parts against each other and by means of a hydraulic adjusting device on a frame are adjustable from each other, the hydraulic adjusting device mitisls a manually operated switchover valve can be switched to reverse direction, in which the clamping devices and thus the plastic parts can be maintained under a predetermined pressing pressure in a pressing position and in which the hydraulic Adjusting device is fed by a pump driven by an electric motor, which in every working position of the switching valve provided with an initial position can be switched on for the duration of the working position is.

Such a hydraulic control circuit for a device of the type mentioned is z. B. known from DE-AS 27 34 9Ί0. This is done manually with the actuatable Unischaltungventil, what with a Stel'bebel The easiest way to accomplish this is to select the direction of adjustment of the actuating devices, depending on the working position. Difficulties in such a device are the pressure build-up to the desired level Compression pressure, which complicates the fact that, depending on the plastic parts used, a certain Pressure build-up time and a very specific pressure must be adhered to. The wall thicknesses play a role the plastic parts to be welded together and the sizes of those to be welded together Areas play a role.

If plastic parts are butt-welded to one another in a company, leave them alone Specific pressure build-up characteristics are predefined via corresponding control devices. Devices but of this type are not suitable for use on construction sites and the like, as they are too expensive and complicated are. Therefore one is content to this day with the fact that the pressing pressure is indicated by means of a manometer and that you can influence the flow rate of the pump via the manually operated switching valve. In addition a switching valve is used, which at least in the forward adjustment of the clamping devices corresponding working position can be opened more or less via the adjusting lever.

This manual influencing and specification of a desired pressure build-up characteristic is decisive Deficiency, because the pressure-time characteristic, which would be optimal for the welding process at hand, by far is not achieved.

From the book "Ölhydraulik", Springer-Verlag Vienna (1963), pages 255 to 261, a hydraulic control circuit is known in which on the feed line continuously Pressure accumulator is switched on, which is dimensioned so that pressure fluctuations occurring in the pump are compensated will.

It is the object of the invention to provide a device of the type mentioned at the outset, with which without major Control and regulation effort predetermined pressing pressure-time characteristics for the pressing position with sufficient Accuracy can be specified. In doing so, shortcomings of the operator be largely switched off and manual control of the hydraulic actuator is possible at any time stay.

This object is achieved according to the invention in that the value pairs of pressure and pressure build-up time prescribed according to DIN 8074/75 and DlN 16 963 for plastic pipes and plastic fittings of various diameters and wall thicknesses are assigned a linear averaged pressure time characteristic that the Pressure build-up of the pump takes place with this pressure-time characteristic and that in a welding process to be carried out solely by specifying the assigned pressure or the assigned

to the assigned pressure build-up time the pressure build-up is ended.

The value pairs of pressure build-up time and compression pressure prescribed by the DIN regulations are for the most varied of welding processes detected by the averaged pressure-time characteristic curve and therefore the correct timing and pressure build-up can be guaranteed simply by specifying a value of the value pair will. The inadequacies in manually influencing both values of the value pair, as in the State of the art with the manually operable valve is made are thus scrapped, because with the respective assigned value of the value pair is automatically assigned to the hydraulic control circuit with sufficient Accuracy must be observed.

An embodiment of the hydraulic control circuit is characterized in that the switching valve in the switch-off position at least the pressure line of the pump with that to the working chamber of the hydraulic cylinder leading control line connects that on the pressure line permanently a pressure accumulator and a manometer are connected to a switch contact adjustable to the desired pressure, that the The pump's electric motor can be switched on by means of an additional push-button switch and when the specified value is reached Pressing pressure can be switched off again that a pump with a large delivery rate per unit of time is used is that the pressure accumulator has a capacity that corresponds to the delivery rate of the pump, which in the one required to build up the maximum pressure maximum pressure build-up time is promoted urJ that the pressure accumulator to an initial back pressure is biased, which is equal to or greater than that required to adjust the clamping device Pressure. This ensures that the pressure accumulator is not already in the adjustment of the actuating devices the pressing position is filled.

In order to safely perform the welding process for the pair of values with the greatest pressure can, provides a further embodiment that the

the working pressure generated by the pump is slightly greater than the maximum pressure.

The automatic shutdown of the pump when reaching ^ '. ¹ S predetermined pressing pressure can be achieved with an arrangement that is characterized by

^r -5 net is that the electric motor of the pump can be switched on via a normally open contact of a contactor, that the contactor can be switched on via a normally open contact of the pushbutton switch and is kept energized through its own holding contact, with the normally closed contact in the holding circuit of the contactor trained pressure gauge switch contact is looped in that the pressure gauge switch contact interrupts the holding circuit for the contactor when the predetermined pressure is reached and that the supply voltage for the contactor and the electric motor of the pump is supplied via a valve contact that is closed in the switching valve. With this semi-automatic setting of the press

Position, the direct control of the hydraulic adjusting device is retained in that the valve contact is designed as a changeover contact, which is used in the forward and backward adjustment of the clamping devices assigned working position of the switching valve switches and the electric motor of the pump switches on directly.

If the specified pressure is reached, the pump is switched off according to a further development Drop in the pressure but automatically switched on again if the arrangement is designed so that the electric motor of the pump can be switched on via a normally open contact of an auxiliary contactor, that the auxiliary contactor Via a normally open contact of a main contactor and a pressure gauge switch contact designed as a normally closed contact can be switched on. that the main contactor can be switched on via a normally open contact of the pushbutton switch and Is kept excited via its own holding work contact that the pressure gauge switch contact when reached of the specified pressing pressure interrupts the circuit for the auxiliary contactor and the electric motor of the pump switches off, when the baling pressure drops, the circuit for the auxiliary contactor closes again and the The pump's electric motor switches on again so that the supply voltage for the pump's electric motor, the auxiliary contactor and the main contactor via a closed in the switch-off position of the switchover valve Valve contact is supplied. and that with the setting of the switchover valve in a working position, the valve contact switches off the main contactor. Also in In this case, the direct control of the hydraulic actuating device remains via the manually operable one Changeover valve obtained when it is provided that the valve contact is designed as a changeover contact is. the working positions assigned to the forward and reverse positions of the clamping devices of the switchover valve and switches on the electric motor of the pump or the auxiliary contactor directly.

So that the pressure reached is maintained for a predetermined time regardless of the actuation of the switching valve (UV) , it is additionally provided that a timer circuit can be controlled via the pressure gauge switch contact when the pressure is reached. which prevents the direct control of the hydraulic actuating device via the valve contact of the switchover valve for a predefinable time.

The invention is explained in more detail on the basis of various exemplary embodiments shown in the drawings explained. It falls

Fig. 1 is a diagram of the time-pressure curve in Build-up of the pressing pressure in the pressing position, in which the plasticized connecting surfaces of each other connecting plastic parts lie against each other,

2 shows the hydraulic block diagram of the device,

F i g. 3 shows the circuit diagram of an exemplary embodiment the electrical control arrangement for the device and

4 shows the circuit diagram of another embodiment the electrical control arrangement.

In the DIN regulation DIN 8074/75 and 16 963 are for plastic pipes and plastic fittings different diameters and wall thicknesses the Wcric for the pressure to be set and the Rise times in which the specified pressure should be reached. If you now these value pairs of the various welds that can be made on a particular device than Cross in the diagram according to FIG. 1 is drawn in, then it can be seen that this is approximately through the drawn Connect the time-pressure characteristic.

In the case of the device, this knowledge becomes evident in a semiautomatic sequence of the Pressure setting used.

With this dimensioning of the hydraulic circuit, the maximum required pressure Pmax is taken into account and a pump HP selected that can generate a higher pressure, as shown in the block diagram according to FIG. 2 can be found. In addition, a pump HP with a large delivery rate in the unit of time (l / min) is used to enable the adjusting movements of the clamping devices. in which the plastic parts to be connected are clamped, brought into the pressing position as quickly as possible and can be returned to their original position. These processes of adjustment and plasticization of the plastic parts only need to be discussed here as far as the manual control of the hydraulic circuit is concerned. The hydraulic adjusting device can have one or more hydraulic cylinders HZ connected in parallel. These hydraulic cylinders HZ can be acted upon on both sides, so that adjusting movements can be transmitted in two opposite directions via the piston K and the piston rod KS. The adjustment is initiated when the z. B. actuatable via an adjusting lever switchover valve

jo UV is brought from the starting position AS into one or the other working position VS or RS . The control lines of the hydraulic cylinders HZ are switched over in a known manner, so that the working chamber AK on the one hand and the return chamber RK on the other hand are connected to the pressure line DL of the pump HP and the adjustment takes place in one direction or the other. The control line of the hydraulic cylinder HZ that is not acted upon is connected to the hydraulic tank TK via the switching valve UV . This manual control is known, a valve contact vk being closed in each working position of the switching valve UV, which valve contact switches on the electric motor M of the pump P for the duration of the actuation. The setting of the device in the pressing position can ζ. Β. can be made via this manual control. However, it is also possible for the first time with the device to carry out the setting in the pressing position and the build-up of the pressing pressure semi-automatically. For this purpose, it is provided that the pressure line

so DL of the pump HP 'in the initial position MSdf "» switching valve UV is connected to the control line to the working chamber AK of the hydraulic cylinder HZ . In addition, a pressure accumulator DSp and a manometer MA with a switch contact mk that can be set to a desired pressure are permanently connected to the pressure line DL The capacity of the pressure accumulator DSp is now dimensioned in such a way that it can hold the amount required by the pump HP for the maximum rise time Tmax

so the pump HPz. B. a delivery rate of 1.2 l / min hai and Tm.iv = 20 see. is, then the pressure accumulator DSp must have a capacity of 0. 4 1. The pressure accumulator DSp is preloaded with a pressure Pv which is greater than that for adjustment dei

pressure required for clamping devices. In this way it is achieved that, simply by specifying a desired compression pressure P, the characteristic curve of FIG. 1 rapid rise time is kept. This makes it easier

Ol l \ J

the work with the device is remarkable, since now only the desired pressure has to be set with the switching contact mk of the manometer MA . The hydraulic circuit regulates the associated time increase automatically.

3 shows an embodiment of an arrangement for this semi-automatic control of the hydraulic circuit. The supply voltage for the arrangement is supplied via a break contact of the Ventilkonlaktes vk . This valve contact vk , designed as a switchover contact, is switched over in each division of work of the switchover valve UV and switches on the electric motor M of the pump A / P directly. So the hand control remains as usual. The semi-automatic control is initiated via the push button switch 75. The response circuit of the soundproofing device 51 is briefly closed. The contactor 51 responds and includes s H via its own holding work contact

a Haltestr

mk of the pressure gauge MA opens. This process is repeated until the valve contact vk of the switching valve UV switches off the main contactor 5 1 by actuating the manual control. This is e.g. B. by setting the Umschnltcveniils CKin the working position RV the case in which the clamping devices are returned to their starting positions after the cooling phase has expired and previously the interconnected plastic parts have been released from the Spanneinrichlungcn.

circuit,! η this holding circuit

the switching contact mk of the pressure gauge MA , which is designed as a normally closed contact, is looped in. The electric motor M of the pump WP is switched on via the normally open contact 12 of the contactor 51. It does not matter what the position of the clamping devices is. In principle, the working chamber AK of the hydraulic cylinder HZ is acted upon via the pressure line DL of the pump HP via the switch-off position AS of the switchover valve t / V. If the pressing position is reached, then the pressure builds up to the set pressing pressure according to the predetermined time-pressure jo characteristic curve of Fig. 1. If the predetermined pressing pressure is reached, then the switching contact mk of the manometer MA opens and interrupts the holding circuit of the contactor 51 Contactor 51 drops out and switches off the electric motor M of the pump HP with its contact s 12. It is easy to see that a three-phase electric motor can also be switched on and off with three working contacts of the contactor 51.

In the case of the FIG. The arrangement shown in FIG. 4 is additionally provided that after the pressing pressure has been reached, the electric motor M of the pump HP is switched on again when the pressure drops below this predetermined pressing pressure. In this way, the pressing pressure can be kept constant over a longer period of time. This is important for the cooling and solidification phase, as this can take several minutes.

The direct activation of the electric motor M of the pump HP via the valve contact vk of the switchover valve UV remains unchanged. The main contactor 51 is briefly energized via the push button switch 75, which closes the holding circuit with its holding work contact 5 11. The normally open contact s 12 of the main contactor 51 switches on the auxiliary contactor 52 via the closed switching contact mk of the pressure gauge MA. The normally open contact s21 of the auxiliary contactor 52 switches the electric motor A / the pump // Pein. The auxiliary contactor 52 is switched off via the switching contact mk of the pressure gauge MA when the specified pressing pressure is reached. The electric motor M is switched off via the contact s 21.But the main contactor 51 remains energized and the contact s 12 is closed, the auxiliary contactor 52 can again are excited when the switching contact mk of the pressure gauge MA closes again when the pressure drops below the specified value. The auxiliary contactor 52 switches the electric motor M on again with the contact s21 until the specified pressure is reached again and the switching contact 2 sheets of drawings

Claims (8)

1 claims: 1. Hydraulic control circuit for controlling a device for butt welding plastic pipes and / or plastic moldings according to the heating element process, in which at least two Clamping devices with the plastic parts fixed therein by means of a hydraulic adjusting device are adjustable on a frame against each other and from each other, the hydraulic Adjusting device can be switched over to reverse direction by means of a manually operated switchover valve are, in which the clamping devices and thus the plastic parts under a predetermined pressure are durable in a pressing position and in which the hydraulic adjusting device of a means Electric motor driven pump is fed, which in each working position of the with a starting position provided switching valve can be switched on for the duration of the working position, d a through marked, that the value pairs of compression pressure and pressure build-up line prescribed according to DIN 8074/75 and DIN 16 963 for plastic pipes and plastic fittings of the most varied of diameters and wall thicknesses are assigned a linear average compression pressure-time characteristic,
that the pressure build-up of the pump (HP) ' takes place with this pressure-time characteristic curve and
that when a welding process jo is to be carried out, the pressure build-up is ended solely by specifying the assigned pressing pressure (P) or the assigned C build-up time (T). 2. Hydraulic control circuit? Laughing claim 1, characterized in that the switching valve (UV) in the switch-off position (AS) connects at least the pressure line (DL) of the pump (HP) with the control line leading to the working chamber (AK) of the hydraulic cylinder (HZ) that on the pressure line (DL.) A pressure accumulator (DSp) and a manometer (MA) with a switching contact (mk) that can be adjusted to the desired pressure (P) are connected, that the electric motor (M) of the pump (HP) can be switched on by means of an additional pushbutton switch (TS) and can be switched off again when the predetermined pressing pressure (P) is reached. that a pump (HP) with a high delivery rate per unit of time (e.g. 1.2 l / min) is used. χ that the pressure accumulator (DSp) has a capacity that corresponds to the delivery rate of the pump (HP) , which is delivered in the maximum pressure build-up time (Tma.x) required to build up the maximum pressure (Pmax) and v> that the pressure accumulator (DSp) is preloaded to an initial counterpressure (Pv) which is equal to or greater than the pressure required to adjust the tensioning device. 3. Hydraulic control circuit according to claim 2. da- «ο marked by. that the working pressure generated by the pump (HP) is slightly greater than the maximum pressure (Pm: i \). 4. Hydraulic Stcucrkreis according to claim 2 or 3, characterized. tv-> that the electric motor (M) of the pump (IIP) is via a working cone (y 12) of a soundproofing system (S Heinschaltbai). that the switching protection (S I) can be switched on via a normally open contact of the pushbutton switch (TS) and is kept excited via its own holding work contact (stt) , the pressure gauge switch contact (mk) being looped into the holding circuit of the contactor (S 1) ,
that the pressure gauge switch contact (mk) interrupts the holding circuit for the contactor (S 1) when the specified pressure is reached and that the supply voltage for the contactor CS1) and the electric motor (M) of the pump (HP) is supplied via a valve contact (vk) which is closed in the switch-off position (AS) of the switching valve (UV). 5. Hydraulic control circuit according to claim 4. characterized marked, that the valve contact (vk) is designed as a wraparound contact. which switches to the working position (VS and RS) of the switching valve (UV) assigned to the forward and backward adjustment of the tensioning devices and switches on the electric motor (M) of the pump (HP) directly . 6. Hydraulic control circuit according to claim 2 or 3, characterized in that that the electric motor (M) of the pump (HP) can be switched on via a normally open contact fs 21) of an auxiliary contactor (S2). that the auxiliary contactor (S2) can be switched on via a normally open contact (s 12) of a main contactor (S 1) and a pressure gauge switch contact designed as a normally closed contact (niA ^. that the main contactor (Si) can be switched on via a normally open contact of the push button switch (TS) and is kept energized via its own holding normally open contact ('s 11), that the pressure gauge switch contact (mk) interrupts the circuit for the auxiliary school (S 2) when the specified compression pressure is reached and switches off the electric motor (M) of the pump (HP) , when the compression pressure drops the circuit for the auxiliary contactor (S2) closes again and the electric motor (M) of the pump (HP) switches on again,
that the supply voltage for the electric motor (M) of the pump (HP), the auxiliary contactor (S2) and the Hauptschülz (Sl) via a valve contact ^ V / ir ^ closed in the off position (AS) of the switching valve (UV) is supplied and
that when the switching valve (UV) is set to a working position (VS or RS), the valve contact (vA:; the Hauplschüt / (.S "I) switches off. 7. Hydraulic control circuit according to claim fa, characterized marked. that the valve contact (1 k) ah Umschahekontakt is formed, which switches to the working positions (VS and KS) of the switching valve ((7V) assigned to the forward and reverse positions of the clamping devices and the electric motor (/ V ^ of the pump (HP) b /. w. the auxiliary contactor (S2) switches on directly. 8. Device according to one of claims 1 to 7, characterized in that When the pressing pressure is reached via the Mnnomelei-Schaltkuntiikt (mk), a Zcitsehaltkrcis is an-Mcuerbar, which prevents the direct control of the hydraulic control device via the valve connector (vk) of the switching valve (./^.