DE3412821A1 - Differential-pressure switch for two-component injection systems - Google Patents

Abstract

The invention relates to an apparatus which is subjected to pressure from two supply lines and emits a signal as soon as a pressure difference exceeding a predetermined magnitude occurs over a predetermined time period between the two supply lines. In a two-component high-pressure injection system, the signal can be used to interrupt the supply or (for example via corresponding control of the pump drives) to match the pressures in the two supply lines to one another. The connections of the apparatus to the supply lines are designed to be self-cleaning so that the switching operation cannot be adversely affected by dried supply medium. <IMAGE>

Description

Differential pressure switch for 2-component spray systems

The invention relates to a device that is operated by 2 delivery lines with pressure is applied and emits a signal as soon as over a predetermined period of time In addition, there is a pressure difference between the 2 delivery lines that is a predetermined value In a 2-component high-pressure spray system, the signal serve to interrupt the funding or (e.g. via a corresponding control of the pump drives) to adapt the pressures in the 2 delivery lines to each other Connections between the device and the delivery lines are self-cleaning, see above that the switching function is not impaired by the dried pumping medium can.

In 2-component high-pressure spraying systems, packages can be damaged or blocked Valves (e.g. as a result of foreign bodies), insufficient supply to the pumps (e.g. as a result of leaky suction lines, debris in the pumped medium, increased viscosity of the Pumped medium) etc. lead to the fact that the pumps do not reach the previously set quantities This has a different mixing ratio of the 2 components and one result in reduced or unsatisfactory quality of the end product. It is therefore desirable that the Constantly check the mixing ratio during operation.

Flow sensors on the suction side of the pumps obstruct the material supply, in particular with highly viscous media and are therefore undesirable.

Flow sensors on the pressure side of the pumps have proven to be high Prints proven to be prone to failure.

Pressure sensors (membrane type and piston type) previously had an or several drawbacks below and were therefore in favor of continuous use Unsuitable: -Dried pumping medium blocked the connection to the pressure line.

- Pressure filling, which can be traced back to the valve slip, was not eliminated.

-Pressure differences resulting from different line resistances to maintain a constant material flow ratio at the pump outlet required have not been neutralized.

The device according to the invention works with pressure errors, but avoids the disadvantages mentioned above! In picture 1 is a training form of value 1 and 2 are conveying lines for component I and component II, respectively, of the 2-component otateriales.ßei 3 and 4, the delivery lines are connected to the font roll device. 5 and 6 are check valves in the delivery lines immediately after the pressure sensors.7,8 and a, lG are pressure sensors (cylinder 7,9 with piston 8,10), which in one Housing 19 are axially connected to one another in such a way that between the cylinders 7 and 9 a gap arises which coincides with the 2 switching paths of the switches 20,21 plus the thickness of the signal piston 17. Two spiral springs 15,16 hold the signal piston 17 including driver 18 in a neutral position. Via line 22, the Switch 20,21 supplied with energy. The output lines 23,24 of the switches 20,21 are connected to the display devices 25, 25 and to an OR gate 27. The OR gate causes switch 20 or switch 21 to produce a signal on line 28. Auf the OR element 27 is followed by a delay element 29. It delays the signal from the line 28 for a specified period of time or suppresses it completely if switch 20 or 21 return to their rest position during the delay period.

Figure 2 shows one of the 2 pressure sensors in more detail, from which it can be seen that one end of the cylinder 7 and the piston 8 protrude into the delivery line and from The pumped medium must be constantly cleaned. Packings 11 and nut 12 are at the outermost The end of the cylinder 7 is arranged towards the conveying line to the area in which The pumped medium can settle and dry, as far as possible.

In the event of a pressure drop, e.g. in line 1, the check valve prevents 5 a pressure equalization from the delivery line. The higher pressure in line 2 moves the piston 10 in the direction of line 1. If the pressure difference is large enough to generate the restoring force to overcome the spring 15, the driver 18 of the signal piston 17 of the switch 20 actuated and given a signal to the delay element 29 via the OR element 27 Indicator 25 shows that line 1 does not have enough pressure. If the signal remains is received beyond the delay time set in the delay element it is then fed into line 30 and can be used, for example, to run the 2-component high-pressure spray system to turn off.

The springs 15 and 16 cause pressure differences in the 2 delivery lines, the do not occur when the pumped medium is flowing as a result of different flow resistances lead to a switching process.

The delay element 29 causes different shutter times of the pump valves (which are caused, for example, in different viscosities of the 2 conveyed Components) do not cause a signal on line 30.

Switches 20 and 21, OR gate 27, display devices 25 and 26 and delay element 29 can be electrical devices as well as pneumatic valves the switches 20,21 with OR gate 27 replaced by a single pressure switch operated by a cam slide with 2 cams. - Blank page -

Claims (7)

Claims 1) Differential pressure switch consisting of 2 pressure sensors of the piston / cylinder type, a signal piston, two return springs and a housing in that the 2 pressure sensors are arranged axially in the housing such that between them a free space is created in which the signal piston from the piston of the Pressure sensor can be moved back and forth. 2) Differential pressure switch as under 1), characterized in that the signal piston in the space between the 2 pressure sensors of 2 compression springs in is held in a neutral position. 3) Differential pressure switch as under 1), its 2 pressure sensors each are connected to a pressure line, characterized in that one cylinder end and one piston end of the pressure sensors in the neutral position as in the activated one Position are washed around by the print medium. 4) Differential pressure switch as under 1), its 2 pressure switches each are connected to a pressure line, characterized in that the seals are arranged between the piston and cylinder at the outermost end to the pressure line. 5) Differential pressure switch as under 1), its 2 pressure sensors each are connected to a pressure line, characterized in that in each pressure line a check valve is arranged such that the pressure sensor each between Check valve and pump are located. 6) Differential pressure switch as under 1), but also with 2 switches, the are operated by a driver on the signal piston and connected to an OR gate are, characterized in that the output line of the OR gate with a delay element connected is. 7) differential pressure switch as under 5), characterized in that the switches, the OR element and the delay element are pneumatic valves.