EP0061630A1 - Flushable gear pump - Google Patents

Abstract

For gear pumps in paint spraying systems, a lockable side channel (59) for flushing, filling and pressure limitation (when using stepped piston rods) is shown in the flow direction behind the teeth parallel to the meshing area and a finely branched flushing net for dead spaces in the area of influence of the color is specified.

Description

The invention relates to a flushable gear pump for color change systems, consisting of a pump body with an inlet for connection to an inflow line, an inlet chamber connected to the inlet, an outlet for connection to a drain line, an outlet chamber connected to the outlet, and a first gear and a second Gear wheels which are rotatably engaged in the pump body and which mesh with one another at least at one point between the inlet chamber and the outlet chamber in order to convey the fluid material (paint) supplied through the inlet from the inlet chamber via the outlet chamber to the outlet.

Color changes are necessary in industrial productions if production goods in different colors are to be coated on a spraying station or on a conveyor belt. In most cases, it is uneconomical to set up separate spraying stations or conveyor belts for each color or larger series than necessary just to avoid color changes and thus dead times.

In such cases, color change systems are advantageous which allow many colors to be sprayed from a single spray gun. In the conventional spraying systems, there are several fluid reservoirs, each containing a different color, and each of the fluid reservoirs can be connected to a separate motor-driven feed pump or a pressure source. Via an inflow line, which is controlled by means of valves, these are in turn connected to the spray gun. To spray a certain color, the associated valve is opened and fluid material flows through the inflow line to the spray gun. After the spray coating with the fluid material of one color has been completed, the inflow line and the spray gun are rinsed with a detergent of solvent and compressed air for cleaning and the system is thus prepared for a new operation for spraying with a different color.

Although the types of color change systems mentioned allow a certain degree of versatility when spraying several differently colored fluid materials with a single spray gun, the required flushing in the case of color changes takes up a great deal of time, which reduces the effective spraying time and thus the capacity. This is especially true for paints that are difficult to remove when cleaning. For this reason, such color change systems lack versatility for use on conveyor belts where quick color changes are necessary.

In many spray coating applications, it is necessary to precisely measure or dose the coating material quantities fed to the spraying system so that a quantity of material required for the prescribed layer thickness is sprayed or so that the correct relationships between the quantities of different fluid materials combined in the spray mist are maintained in the case of multi-component systems. Gear pumps for conveying the fluid material are often used for this purpose as part of a color change system.

Although gear pumps are well suited to deliver metered amounts of the coating material to spray coating apparatus, difficulties arise when used in color change systems. This is because the fluid material flows through the gear pump, so that when the color changes, it must first be cleaned thoroughly in order to prevent contamination of the new coating material. Due to the special design of conventional gear pumps, cleaning takes a long time when changing colors, so that large loss times can be expected.

The object of the invention is to find a rinse for a color change system with a gear pump, in which sufficient amounts of detergent reach all the parts which are loaded with paint, in order to achieve flawless cleaning in the shortest possible time. At the same time, the makeready time when changing colors is to be improved and a predetermined pressure of the delivery flow of the gear pump should not be exceeded.

According to the invention, the gear pump is provided with at least one flow system that can be shut off by a valve, as a result of which sufficient amounts of rinsing liquid or fluid material can get directly to all locations exposed to fluid material, bypassing the low delivery capacity of the gear pump, so that the cleaning or the insertion of new paints in the shortest possible time can be done. Despite these short makeready times, a dirty effect when changing colors is avoided.

In a special embodiment, this flow system is formed by a side channel which can be closed by means of a valve and which consists of a first flushing channel, a connecting channel and a second flushing channel and which bypasses the meshing area of the gear wheels of the gear pump. This assignment allows two switching positions of the valve.

When the side channel is blocked, the gear pump works according to the known principle. The fluid material flowing from the inlet chamber into the tooth gaps is conveyed along the housing wall when the gearwheel is turned, until it is pressed into the outlet chamber by combing the oppositely meshing gearwheels:

When the side channel is open, a second flow flows parallel to the gear pump via the side channel, which consists of a flushing channel in the extension of the inlet chamber, a connecting channel transverse to the latter and a flushing channel to the outlet chamber. This makes it möglichin short time large amounts of flushing medium for cleaning or _F luidmaterial to send when introducing new colors by the gear pump through.

In a further embodiment, the valve consists of a cylinder with a piston which can be acted upon on two sides by control valves and which has an elongated piston rod with the end of which a flushing channel lying in front in the same axial direction can be closed at the end. Depending on the position in front of the first or second flushing channel, liquid pressure in the inlet or outlet of the gear pump can thus be controlled via the air pressure in the cylinder.

In a special embodiment, the piston rod has a step in the region of the connecting channel. This improves the pressure limitation. If an overpressure arises in the area of the gear pump, the valve opens as long as the balance of the three forces, namely pressure of the guide air on the piston in the cylinder, pressure of the fluid material on the stage of the piston rod and pressure of the fluid material from the opposite side of the gear pump is disturbed on the end face of the piston rod. The valve thus automatically limits the pressure in the fluid material generated by the gear pump to a maximum value specified by the air control variable, which prevents damage caused by overpressure.

In one embodiment, a separate channel network is arranged as a flow system, which has outlets for sufficient flushing of the gaps in the treads and dead spaces in the interior of the sealed area of the gear pump, as a result of which sufficient amounts of flushing agent also reach inaccessible places, so that perfect cleaning is accomplished in a short time can be.

According to the invention, all mentioned embodiments of the invention can be combined in a single gear pump, so that the entire inner surfaces can be cleaned thoroughly by the detergent.

• Fig. 1 teilgeschnittene Ansicht einer Zahnradpumpe mit Anordnung von Zahnrädern, Eingang und Ausgang;
• Fig. 2 teilweiser Schnitt längs der Linie 2-2 der Fig. 1 durch Zahnradpumpe und Ventilgehäuse;
• Fig. 3 Schnitt längs der Linie 3-3 der Fig. 2 mit Seitenkanal und geöffneten Ventil in Verlängerung der Eingangskammer;
• Fig. 4 Schnitt durch Seitenkanal mit geschlossenem Ventil in Verlängerung der Eingan^gskammer;
• Fig. 5 Schnitt durch ein Ventil in Verlängerung der Eingangskammer, mit einem im Verbindungskanal abgesetzten Kolben;
• Fig. 6 Schnitt durch ein Ventil in Verlängerung der Ausgangskammer mit einem im Verbindungskanal abgesetzten Kolben;
• Fig. 7 - 10 Schnitte durch Zahnradpumpen mit separaten Kanalsystemen für Spülmittel.

The mentioned and other objects, advantages and features of the invention are explained in more detail with reference to the following description of exemplary embodiments of the invention. It shows:

• Figure 1 is a partial sectional view of a gear pump with an arrangement of gears, input and output.
• Fig. 2 is a partial section along the line 2-2 of Figure 1 by gear pump and valve housing.
• Fig. 3 section along the line 3-3 of Figure 2 with side channel and open valve in the extension of the input chamber.
• Fig. 4 is sectional view through the side channel with a closed valve in the extension of Eingan ^g skammer;
• 5 shows a section through a valve in the extension of the input chamber, with a piston offset in the connecting channel;
• 6 shows a section through a valve in the extension of the exit chamber with a piston which is offset in the connecting channel;
• Fig. 7 - 10 sections through gear pumps with separate channel systems for detergent.

1 and 2 show a type of gear pump 20 in which the teachings of the invention can be advantageously used.

The gear pump 20 has a front plate 22, a central plate 24 with a bore 30 + 32, a rear plate 26 and a motor housing 28. In the bore 32 is a driven or loose gear 34 which is rotatably mounted on a shaft 36, while the bore 30 receives a driven gear 38 which meshes with the loose gear 34 and is rotatably seated on a shaft 40. The driven shaft 40 is keyed onto a motor shaft 42 of a motor 44 placed on the motor housing 28, so that the motor can rotate the gear 38 and thus also the gear 34. In front of the area where the gears 34 and 38 interlock in the direction of rotation, there is an outlet chamber 48 in the plates 24 and 26 and after the area where the gears stop meshing, an inlet chamber 46 is provided in these plates. An O-ring 50 seals the shaft 40 on the back plate 26, while an O-ring 52 serves as a seal between the back plate 26 and the motor housing 28.

When fluid material enters inlet chamber 46, each tooth fills as gears 34 and 38 rotate gap 54 with fluid material. As the gears continue to rotate, the fluid material is conveyed along the inner walls of the bores 30 and 32 into the tooth spaces 54 until it reaches the outlet chamber 48, where the two gears 34, 38 comb the fluid material into the outlet chamber 48. Since the capacity of the tooth gaps is known and the speed of rotation of the gear wheels can be regulated, the pump can dose precise volumes essentially independently of changes in the viscosity, pressure and temperature of the fluid material.

According to FIGS. 2 to 4, a first flushing channel 56 aligned with the inlet chamber 46 and a second flushing channel 58 aligned with the outlet chamber 48 extend through the front plate 22. A valve housing 63 connects to the front plate 22, in which the connecting channel 57 to the two Flushing channels 56, 58 is located, and in addition the valve housing 63 contains a pneumatically actuated valve 62 which has a piston 64 and a piston rod 66, with one end 68 of which the opening of the flushing channel 56 can be closed.

By opening one of the control valves 72 or 74, compressed air flows into the cylinder 70 against one or the other side of the piston 64 and moves the piston rod 66, the passage through the connecting channel 57 opening in one end position or the end 68 in the other end position the piston rod 66, the opening to the flushing channel 56 is closed.

Filling the color change system with coating material is significantly accelerated by opening the side channel. For this purpose, the control valve 72 is opened so that the valve 62 clears a path through the side channel. Then the input 78 of the gear pump is connected via an inflow line 79 to the fluid material container of a selected color and one of the inflow valves 80a-d is opened, which then clears the way for the fluid material. Coating material then passes through the inlet chamber 46 to the gears 34 and 38 which convey it in the tooth spaces 54 between the teeth of the gears to the outlet chamber 48 and the outlet 82 and at the same time fluid material flows through the side channel to the outlet chamber for filling. This is in turn connected by a delivery line, not shown, to a paint spraying system, also not shown.

After the filling process, the control valve 72 is closed, and the control valve 74 is opened. The piston 64 moves in the direction of the valve seat 76 until the end of the piston rod 66 closes it. In normal operation, the gear pump 20 conveys the fluid material from the inlet chamber 46 directly to the outlet chamber 48, from where it is then delivered to the paint spraying system.

When the spraying process with fluid material of one color has ended and in preparation for the spraying process with fluid material of another color, all inflow valves 80a-d are closed, a flushing agent valve 84 in FIG Inflow line to the entrance is opened, the control valve 74 is closed and the control valve 72 is opened to actuate the valve 62 to open the side channel 59. Under these conditions, with the gear pump rotating, a relatively large amount of flushing agent can flow between inlet 78 and outlet 82 through inlet and outlet chambers 46 and 48, flushing channels 56 and 58, connecting channel 57, and along the teeth of gears 34 and 38 quickly clean the gear pump and its feed and return lines of fluid material. The flushing agent valve 84 is then closed and one of the inflow valves 80a-d is opened in order to supply the paint spraying system with the next selected coating color.

The special structure of the valve 62 is more advantageous than e.g. a slide valve. Only a single O-ring seal 86 is required to seal the valve against material in the channel, and the seal is never within the side channel. Therefore, the problem of sticking the valve due to the accumulation of fluid material in the area of the seal is eliminated. The valve always remains free to move. _

FIG. 5 shows an embodiment of a valve 62 with automatic control and limitation of the maximum pressure that can occur at the outlet of the gear pump. The valve works in the same way as has already been explained in FIGS. 3 and 4.

Notwithstanding these valves, the valve 62 is provided to _F-i gur 5 with a piston rod 88 which has a step 90 in the region of the connecting channel. When the valve for closing the side channel is actuated, the stage 90 is located in the connecting channel and forms a surface against which the pressure of the fluid material - as transmitted from the pump outlet through the flushing channel 58 - exerts a force that is proportional to the pressure and directed opposite to the force exerted on the piston 64 by the air introduced through the control valve 74. When the force transferred from the material pressure to the stage exceeds the opposite force with which the air supplied through the valve 74 loads the piston 64, the piston rod moves and clears the way through the communication channel so that the material flow from the outlet 82 can flow to the input 78 of the gear pump. This limits the outlet pressure to a maximum value and any overpressure that may arise is immediately reduced. Thus, by controlling the pressure of the air supplied by the control valve 74, the maximum pressure of the fluid material is automatically regulated and limited. Overpressures are avoided which, as is well known, can reach an order of magnitude of 10,000 psi (689.5 bar), which could then lead to component bursting and / or damage to the paint spraying system.

In the arrangement of the valve 62 shown in FIG. 6, it is arranged so that the end of the piston rod 92 can close the flushing channel 58. Thus, the material pressure at the outlet from the gear pump exerts a force against the end of the piston rod that is proportional to the pressure and opposite to the force with which air enters through control valve 74, piston 64 and through the fluid material entering from the inlet the stage is loaded, whereby when sufficient pressure is generated at the outlet of the pump, the valve is moved in the direction in which the flushing channel is opened and a path between the outlet and the inlet of the pump is opened in order to limit the outlet pressure to a maximum value and Relieve overpressure condition. In this way, by regulating the pressure of the air entering the cylinder 70 through the control valve 74, the maximum pressure developed by the pump can be automatically limited and controlled. If desired, the mechanical movement of the valve can be determined in response to an overpressure developed by the pump and a signal can be generated which warns an operator and informs of an error.

Although the side channel and valve are shown and described as part of the pump structure, they can also be separate. For example, the valve housing 63 can be omitted and a valve located away from the pump can be connected via lines to the flushing channels 56 and 58. A valve between inlet 78 and outlet 82 of the gear pump can also be used for rapid flushing of the inlet and outlet lines, although this does not affect the flushing of the pump itself. Alternatively, for rapid rinsing, the detergent introduced at the inlet 78 can simply be discharged to a spout or to a collection point after the rinsing channel 56, while at the same time other detergent is let into the rinsing channel 58, which leaves the gear pump again through the outlet.

Figure 7 shows a gear pump, in which the gear 38 is pressed on the driven shaft 40 so that there is no gap between the two parts, in which the axis 36 is pressed stationary and also gap-free into the plate 26 and in which the loose gear 34 rotates about axis 36. In the plate 26, an inlet fitting 94 is inserted for connection to a detergent source, not shown, to which a channel 96 connects, which extends in the plate to the bore for receiving the shaft 40. The shaft 40 includes an annular groove 98 which is permanently connected to the channel 96, a diametrical channel 100 which is connected at the ends to the annular groove 98, and an axial channel 102 which is located in the axis of the shaft 40 between the diametrical Channel 100 and an opposite end of this shaft is located. With the gear pump rotating, the flushing agent introduced through the inlet fitting 94 flows via the channel 96, the ring 98 and the channels 100, 102 both into the spaces 104a-e between the driven shaft 40 and the pump body and into the spaces 106a-b between the sides of the gear 38 and the pump body, from where it then leaves the outlet 82 of the gear pump via the tooth gaps 54 of the gears 34, 38. All parts that the detergent flows past are cleaned.

For flushing the driven part of the gear pump, a channel 107 extends through the back plate 26 between the annular groove 98 and an annular groove 108 which surrounds the axis 36. A channel 109 runs diametrically through the axis 36 and is open at the ends to the annular groove 108. From this, a channel 110 branches off axially to the axis 36, which is connected at one point via a diametrical channel 111 and a further annular groove. In this way, the flushing agent entering the inlet fitting 94 also flows the channels 107, 109, 110, 111 and the annular groove 108 into the gap 112a between the gear 34 and the axis 36, in column 112b-c between the sides of the gear and the Pump body and in a space 114 between one end of the shaft and the pump body and from there into the tooth gaps 54 of the gear 34, from where it flows through the outlet of the gear pump, the entire driven part of the gear pump is completely cleaned of fluid material.

As can be seen, the flushing agent admitted to inlet fitting 94 does not enter the gear pump through inlet 78, and the amount of flushing agent is less than when flushing agent is input at the inlet and a side channel is used. To facilitate cleaning the It is therefore provided that the pump and its inlet and outlet lines are combined with the embodiment of the invention shown in FIG. 7 with the embodiment in which a side channel is provided for the gear pump, or in another way in which a large volume flow of detergent through inlet and outlet chambers and corresponding lines can pass through.

Figures 8-10 show a further embodiment of the gear pump, which enables thorough cleaning of the entire pump interior if it is a gear pump in which the driving and driven shafts 36 and 40 each rotate within the pump body, and the driven and the driving Gear 34, 38 are attached to their associated shafts by pins 115 so that there are gaps between the shafts, the gears and the pump body.

To clean the pump, an inlet 116 in the motor housing is connected to a detergent source (not shown) and is connected via a channel 118 to a chamber 120 which is formed in the motor housing and the back plate 26 next to the shaft 40 and along it. In the surface of the shaft there is a longitudinal spiral groove 122 which is connected to the chamber 120 at one end of the shaft, the arrangement being such that during the rotation of the shaft always part of the groove with the Chamber communicates. Another groove 124 is located in the surface of the shaft 36 and is connected to the motor housing 28 with the chamber 120 via a channel 126. The channel 126 is so large that the groove 124 remains in communication with it during the rotation of the shaft 36. Flushing agent introduced into inlet 116 therefore enters chamber 120 and grooves 122, 124 and then flows into and through all of the spaces between shafts 36 and 40 and the subsequent surfaces of the gears and pump body to clean them.

To clean the gaps between the sides of the gear wheels 34, 38 and adjacent pump body parts, a plurality of inlets 128a-d can also be connected to the detergent source and are located in the front plate 22 or rear plate 26, via associated channels 130a-d with corresponding semicircular grooves 132a-d. in connection. The detergent entering the inlets 128a-d therefore passes through the grooves 132a-d into the gap between the sides of the gears and the plates in order to clean them thoroughly.

The flushing agent introduced into the gear pump at the inlets 116 and 128a-d finally reaches the tooth gaps 54 of the gear wheels 34 and 38, in order to flow out from there through the outlet of the gear pump.

To facilitate cleaning of the inlets and outlets as well as the material inlet and outlet lines of coating material, the detergent source can also be used two channels 134 and 136 are connected, which are connected to the inlet chamber 46 and the outlet chamber 48, respectively. During the connection of the flushing agent source to the channels 134 and 136, the material inlet and outlet lines are open at their ends facing away from the gear pump, so that the flushing agent let into the channels through the chambers 46, 48, the inlet 78, the outlet 82 and the inlet or outlet lines to clean them thoroughly. Alternatively, it is also possible for the channels 134 and 136 to be optionally connected to one another via a bypass channel controlled by an installed or removed valve, so that the gear pump is flushed as previously described.

Claims (6)

1) Flushable gear pump (20), for color changing systems consisting of a pump body with an inlet (78) for connection to an inflow line (79), an inlet chamber (46) connected to the inlet (78), an outlet (82) for connection to a Drain line, an outlet chamber (48) connected to the outlet (82) and a first gear wheel (38) and a second gear wheel (34) which are rotatably supported in the pump body in mutual engagement and which are at least at one point between the inlet chamber (46). and combing the outlet chamber (48) with one another in order to convey the fluid material (paint) supplied through the inlet (78) from the inlet chamber (46) via the outlet chamber (48) to the outlet (82), characterized in that the gear pump (20 ), in particular for flushing, is provided with at least one flow system which can be shut off by a valve (62). 2) Gear pump according to claim 1, characterized in that this flow system is formed by a side channel (59) which can be closed by means of a valve (62) and which comprises a first flushing channel (56), a connecting channel (57) and a second flushing channel (58) exists and which bypasses the meshing area of the gears (34, 38) of the gear pump (20). ₃ ) Gear pump according to claim 1-2, characterized in that the valve (62) from a cylinder (70) with a bilateral control valves be there is an openable piston (64) which has an elongated piston rod (66) with the end (68) of which a flushing channel (56, 58) lying in front in the same axial direction can be closed at the end. 4) gear pump according to claims 1-3, characterized in that the piston rod (68) in the region of the connecting channel (57) has a step (90). 5) Gear pump according to claim 1, characterized in that a separate channel network is arranged as a flow system, which has outlets for sufficient rinsing of all gaps in the treads and dead spaces in the interior of the sealed area of the gear pump. 6) gear pump according to claims 1-5, characterized in that the different flow systems are used in combination in a gear pump.

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