GEAR PUMP
The invention relates to a gear pump having two meshing gear wheels configured of a driven gear wheel and a gear wheel moving along with the same. A rotatably supported drive shaft is provided for driving the gear wheel, the shaft being held in the pump housing by bearing means. A sealing means is associated with the drive shaft at the circumference between the gear wheel and the bearing means, the sealing means comprising a pressure ring resting against a face of the gear wheel. In order to prevent the gear wheel in the pump housing from starting to run, a second sealing means having a second pressure ring is disposed on the opposite face of the gear wheel at the circumference of the drive shaft between a second bearing means and the gear wheel, wherein both pressure rings have a sealing shoulder opposite the gear wheel, the shoulder being pressed against the face of the gear wheel under the action of a spring means.
The invention concerns a gear pump for transport of paints according to the preamble of Claim 1.
A generic gear pump is known from EP 1 280 996 B1. The known gear pump has two meshing gears mounted to rotate within a pump housing. One of the gears is connected to a drive shaft mounted in a bearing site within the pump housing. The drive shaft penetrates the pump housing in the bearing site and is connected to a drive outside the pump housing. For sealing of the outward guided drive shaft a sealing device is assigned to the gear on the drive shaft, which seals the bearing device of the drive shaft relative to a feed space formed on the periphery of the gear. Here the seal has a ceramic ring that is supported on one face of the gear under a bias.
Through this one-sided support of the seal on the face of the gear the gear is forced against the pump housing with the opposite face so that non-uniform sealing gaps are produced because of nonsymmetric loading of the gear. The suspicion that force balance occurs during operation with the operating force acting on both sides of the gear because of the larger opposite face of the gear is also not true, since, according to experience, a pressure drop occurs over the length of the sealing gap between two bodies. Nonsymmetric loading of the gear also persists during operation so that increased friction occurs between the gear and the pump housing on the face of the gear opposite the seal.
Another gear pump to convey and meter paints is known from DE 10 2005 016 670 A1 in which seals are arranged in the pump housing on both faces of the driven gear in order to separate the feed area within the pump housing from the bearing area of the drive shaft. The seal here is formed by a seal and spring element that loads the seal with a small force in the direction toward the gear. Symmetric loading of the gear on both sides does occur here, but with the drawback that the seal is arranged in an outer peripheral area of the gear so that the seal because of the relatively large diameter rubs against the faces of the gear with relatively large contact surface and therefore leads to higher wear phenomena. In addition, because of the sealing grooves formed in the pump housing only relatively small spring elements can be integrated, which according to experience can only generate limited friction forces for pressing the seal. Only limited sealing of the gap between the faces of the gear and the pump housing can be achieved in this respect. Another drawback of the known gear pump is due to the fact that leaks of the sealing sites directly lead to a situation in which paint reaches the bearing site of the drive shaft, which is particularly difficult to remove especially during rinsing.
It is now the task of the invention to modify a gear pump of the generic type so that, on the one hand, high sealing relative to the bearing sites of the drive shaft against the gear is achieved and, on the other hand, good rinseability of the pump is retained.
Another objective of the invention is to devise a gear pump of the generic type in which bearing friction of the drive shaft remains essentially constant during operation.
This task is solved by a gear pump with the features according to Claim 1.
Advantageous modifications of the invention are defined by the feature combinations of the corresponding dependent claims.
The invention has the particular advantage that the driven gear is guided freely in the pump housing and forms a relatively uniform sealing gap on each face with the pump housing. For this purpose a second seal with a second sealing ring is arranged on the opposite face of the gear on the periphery of the drive shaft between a second bearing and the gear, in which both pressure rings each have a sealing shoulder on both faces of the gear and are forced against the faces of the gear by a spring device. The gear is tightened between the pressure rings and therefore independent of the position of the drive shaft. Run-up of one of the faces against one of the housing plates is avoided on this account and the gear forms an equally large sealing gap relative to each face with the pump housing. The sealing rings biased on both sides as well as the position of the gear fixed on this account permit a high sealing effect so that the paint emerging from the feed space advances essentially into the lateral sealing gap only up to the sealing shoulders of the pressure rings. The bearings within the pump housing remain free of paint so that rinsing of the bearing sites of the drive shaft is unnecessary. The requirements for rinseability can therefore be omitted in designing the bearings.
In order to prevent even small paint residues from passing through the sealing site between the pressure rings and the gear and the pressure rings and the pump housing and reaching the bearings, the modification of the invention is preferably used in which the seals each have a sealing ring, which shield the bearings on both sides of the gear relative to the pressure rings and delimit a rinsing space formed between the pressure ring and the sealing ring on the periphery of the drive shaft. The sealing rings, which are arranged on the periphery of the drive shaft and have a sealing effect between the pump housing and the drive shaft form a second seal arranged after the pressure rings in order to separate the bearing sites from the feed space. Even residues of paint entering the rinsing space are therefore kept away from the bearings.
Since the gear pumps used to convey paints are rinseable to execute a paint change it is prescribed that each of the rinsing spaces is connected to a rinsing connection through a rinsing channel on the pump housing. The paint that has entered the rinsing space can therefore be flushed out before a paint change by means of a rinse liquid fed via the rinsing connection.
In order to be able to flush the joint gap that forms between the gear and the drive shaft with a rinsing agent it is proposed according to a modification of the invention to connect the two rinsing spaces by several rinsing channels between the drive shaft and the pressure rings as well as the between the drive shaft and the gears.
Because of a high sealing effect between the bearing sites and the feed area of the gear pump all common gears can be used to support the drive shaft. The bearing devices can therefore be formed by bearing sleeves for plain bearing of the drive shaft, but in which outside agents are used in the case of bearing lubrication. In order to obtain the highest possible lifetimes and operating times of the gear pump the bearings to support the drive shaft are preferably formed according to an advantageous modification of the invention by at least two roller bearings whose roller bodies are held in an annular chamber filled with lubricant. Grease fillings are preferably used here as lubricants so that the drive shaft can be driven with relatively limited bearing friction.
During feed of paints, for example, in painting installations for painting of auto body parts for vehicles it must be kept in mind in particular that the supplied amount of paint is adjustable via the speed of the drive shaft and remains constant during operation during selection of a drive speed. For this purpose it is essential that tooth engagement of the driven gear and the idling gear occur with the least possible play in order to avoid tolerance-related feed fluctuations. To this extent the modification in which the idling gear is connected to rotate in unison with a shaft pin, which is supported on both sides of the gear by several bearings, is particularly advantageous in order to guarantee constant feed. In this case a seal is provided on the periphery of the shaft pin on both sides of the gear, each of which has a pressure ring lying against one of the faces of the gear.
The bearings of the shaft pin can then also be preferably shielded by sealing rings relative to the pressure rings so that no paint residues soil the bearings. Sealing rings form with the pressure rings on the periphery of the shaft pin on each side of the gear a rinsing space which is connected through a rinsing channel and pump housing to a rinsing connection. The leakage emerging on the idling gear through the gap between the pump housing and the gear can also be removed by rinsing after entering the rinsing spaces.
To rinse the joint gap between the gear and the shaft pin it is also proposed that the two rinsing spaces be connected to each other by several rinsing channels between the shaft pin and the pressure rings and between the shaft pin and the gear.
The bearings to support the shaft pin are preferably designed identical to the bearings of the drive shaft. Plain bearing with bearing sleeves would be possible. The bearings to support the shaft pin, however, are preferably formed by at least two roller bearings whose roller bodies are held in an annular chamber filled with a lubricant.
In order to minimize wear of the seals relative to the gear, on the one hand, and to obtain a high sealing effect relative to the bearings, on the other, according to a modification of the invention the pressure rings are formed from a ceramic material and the sealing rings are designed as so-called groove rings.
For the sealing effect of the sealing sites formed between the pressure rings and the gears the bias force generated by the spring device is decisive, with which a sealing shoulder of the pressure ring is held against the face of the gear. It is essential here that the generated bias force remains essentially constant during the operating time of the pump. To this extent the modification of the invention in which the spring device is formed by a belleville spring stack has proven itself as a spring device for pressing the pressure rings. In this case high spring forces can be generated even in small design spaces on the periphery of the drive shaft or shaft pin.
The advantageous modification of the invention in which the faces of the gears are formed from a ceramic material has the particular advantage that even with larger bias forces of the pressure rings increased wear phenomenon cannot occur. In addition, the friction forces generated between the faces of the gears and the sealing shoulders of the pressure rings made from ceramic remain relatively low.
In order to keep the gap that forms between the gears and the pump housing within the narrowest possible tolerance with high sealing effect, the pump housing is preferably designed in several parts, the faces of the gears being held between two housing plates. The plate design permits precision machining of the pump housing so that high plane-parallelism can be set between the gears and the housing plates.
In another advantageous modification of the invention it is proposed to form the drive shaft from a bearing shaft and a coupling shaft connected to the bearing shaft through a releasable rotary connection, in which the bearing shaft is connected to the gear within the pump housing and supported by the bearing. The coupling shaft, on the other hand, is mounted to rotate outside of the pump housing in a support housing through a support bearing and can be connected to the drive on the free end. The external forces acting on the drive shaft can also be advantageously taken up by the support bearing.
The gear pump according to the invention is further explained below by means of some practical examples with reference to the accompanying figures.
In the figures
A first practical example of the gear pump according to the invention is shown in a schematic sectional view in
The gear pump has a pump housing 1, designed in several parts and consists of housing plates 1.1 and 1.2 as well as the center plate 1.3 held between housing plates 1.1 and 1.2. The housing seals 1.4 and 1.5 are arranged between the faces of the housing plates 1.1 and 1.2, through which the gap between the center plate 1.3 and the housing plates 1.1 and 1.2 is sealed outward. The center plate 1.3 has recesses for two meshing gears 4 and 5. In the overlapping area of gears 4 and 5 a feed channel system 6 is formed in the housing parts, which is connected to a pump inlet 2 formed in housing plate 1.2 and to a pump outlet 3 formed in housing plate 1.1. The feed channel system 6 is preferably formed by holes and recesses in housing plates 1.1 and 1.2 as well as center plate 1.3.
The gear 4 is splined to a drive shaft 7. For this purpose the gear 4 is forced through a center hole 28 of the drive shaft 7. A connection device 29 (shown with a dashed line here) is provided between the periphery of drive shaft 7 and the hole 28 of gear 4, through which a shape-mated and splined connection is formed between the drive shaft 7 and gear 4. The drive shaft 7 has a bearing end 7.1 within pump housing 1 and a coupling end 7.2 outside of pump housing 1. For this purpose a through mounting hole 18 is provided in housing plate 1.1 and housing plate 1.2, which is essentially penetrated coaxially by drive shaft 7. A seal 9.1 and 9.2 and a bearing 8.1 and 8.2 are arranged in the housing plate 1.1 and the housing plate 1.2 between the periphery of drive shaft 7 and the mounting hole 18 of housing plates 1.1 and 1.2. Each of the seals 9.1 and 9.2 has a pressure ring 10.1 and 10.2. The pressure rings 10.1 and 10.2 are axially movable in the periphery of the drive shaft 7 and each supported with a sealing shoulder 16.1 and 16.2 on the faces of gear 4. The pressure rings 10.1 and 10.2 as well as the faces of gear 4 are preferably formed from a ceramic material for this purpose. The gear 4 and the pressure rings 10.1 and 10.2 can also be completely formed from a ceramic material.
A spring device 11.1 and 11.2 is arranged on the side of each pressure ring 10.1 and 10.2 opposite sealing shoulders 16.1 and 16.2. The spring device 11.1, which is formed in this practical example as a belleville spring stack, is tightened between a retaining ring 17 fastened in housing plate 1.1 and the pressure ring 10.1. The spring device 11.2 acts on the opposite side of gear 4, also being designed as a belleville spring stack, between an additional retaining ring 17 fastened in housing plate 1.2 and pressure ring 10.2.
The seals 9.1 and 9.2 also each have a sealing ring 12.1 and 12.2 on the side facing the bearings 8.1 and 8.2, which is held between the periphery of drive shaft 7 and the mounting hole 18 in the housing plates 1.1 and 1.2. The seals 12.1 and 12.2 in this practical example are formed by groove rings which generate radially acting pressure forces between the drive shaft 7 and the mounting holes 18.
The sealing rings 12.1 and 12.2 are held with a spacing relative to pressure rings 10.1 and 10.2 on the periphery of the drive shaft 7 so that a rinsing space 13.1 and 13.2 is formed in the intermediate space between the drive shaft 7 and the mounting hole 18. Rinsing space 13.1 is coupled via a rinsing channel 14.1 in housing plate 1.1 to a rinsing connection 15.1. The rinsing space 13.2 formed on the opposite side of gear 4 in seal 9.2 is connected via rinsing channel 14.2 in housing plate 1.2 to a rinsing connection 15.2. During operation the rinsing connections 15.1 and 15.2 are connected to a rinsing system.
The rinsing spaces 13.1 and 13.2 are connected by several rinsing grooves 36.1 and 36.2. The rinsing grooves 36.1 here each denote the rinsing groove that extends between the pressure ring 10.1 and the drive shaft 7 and the pressure ring 10.2 and the drive shaft 7. The rinsing groove 36.1 can be formed here by a groove on the periphery of the drive shaft or by a groove on the inside diameter of the pressure ring. The rinsing groove 36.2 denotes a connection between the faces of gear 4, in which this can be formed by a groove in the hole 28 of gear 4 or by a groove on the periphery of drive shaft 7.
To support the drive device the bearings 8.1 and 8.2 are each arranged in the outer areas of housing plates 1.1 and 1.2. The bearings 8.1 and 8.2 are formed for this purpose by roller bearings 32 having a number of roller bodies 30, which are held in closed annular chamber 31 between an inner and outer race. The roller bearings 32 are held in the axial direction by a retaining ring 17 fastened in the housing plates 1.1 and 1.2. A grease filling is preferably contained as lubricant in the closed annular chamber 31, which preferably guarantees lubrication of roller bodies during the operating time of the gear pump.
The mounting hole 18 in housing 1.1 is closed outward by cover 27. On the opposite drive side of pump housing 1 the coupling end 7.2 of drive shaft 7 protrudes from the mounting hole 18 of housing plate 1.2. The coupling end 7.2 of drive shaft 7 has a diameter shoulder 33 in the end area on which a support ring 20 lies. The support ring 20 is designed L-shaped and held in a recess of a support housing 19.
The support housing 19 has a recess 21, penetrated by the drive shaft 7 completely so that the free coupling end 7.2 of drive shaft 7 protrudes from the support housing 19 for connection of a drive. The support housing 19 is firmly connected to pump housing 1.
The gear 4 driven by drive shaft 7 engages with gear 5, which rotates freely between housing plates 1.1 and 1.2 and is held in center plate 13. The gear 5 is held with its hole on a bearing pin 34. The bearing pin 34 in this example is not mounted in the housing plates 1.1 and 1.2 so that the gear 5 is only guided through the housing plates 1.1 and 1.2 and through center plate 1.3 and is driven by gear 4.
In the gear pump depicted in
The leaks that might emerge through the gap between pressure ring 10.1 and 10.2 and housing plates 1.1 and 1.2 are taken up by the tolerances 13.1 and 13.2. Hermetic sealing relative to bearings 8.1 and 8.2 occurs through the sealing rings 12.1 and 12.2 assigned to the pressure rings 10.1 and 10.2 so that no leaks can enter the bearings 8.1 and 8.2.
In order to eliminate the leaks with paint residues from the rinsing spaces 13.1 and 13.2 and the gaps between the gear 4 and drive shaft 7 during a paint change, a rinse liquid is introduced to the pump housing through rinse connections 15.1 and 15.2 and flushes the intermediate spaces between the drive shaft 7, the housing plates 1.1 and 1.2 and gear 4. The feed channel system 6 within the pump housing is then also flushed by means of a rinse liquid via pump inlet 2 and pump outlet 3 so that the gaps between the gears 4 and housing plates 1.1 and 1.2 and center plate 1.3 can also be flushed.
Another practical example of the gear pump according to the invention is schematically depicted in
The drive shaft 7 splined with gear 4 is formed in this practical example by a bearing shaft 25 and a coupling shaft 26, which are connected to each other by a rotary connection 24. The bearing shaft 25 is mounted to rotate via bearings 8.1 and 8.2 in the mounting holes 18 of housing plates 1.1 and 1.2. The seals 9.1 and 9.2 assigned to the bearings 8.1 and 8.2 are formed on the periphery of bearing shaft 25 and bearings 8.1 and 8.2 identical to the previous practical example so that reference can be made to the preceding description.
The bearing shaft 25 essentially extends over the width of housing plates 1.1 and 1.2, the bearing shaft 25 being coupled to the coupling shaft 26 on the drive side. For this purpose moldings are made on the ends of bearing shaft 25 and coupling shaft 26, which represent the rotary connection 24.
The coupling shaft 26 is mounted to rotate via a support bearing 22 in a support housing 19. The coupling shaft 26 is then held both in the actual direction and in the radial direction by the support bearing 22 in support housing 19. The coupling shaft 26 has a free end protruding from support housing 19, which can be connected to a drive (not shown here).
The idling gear 5 is connected on the periphery of a shaft pin 23 to rotate in unison with it. The shaft pin 23 for this purpose penetrates the hole in gear 5 and is mounted on both sides of the gear 5 in mounting holes 35 of housing plate 1.1 and housing plate 1.2. On the periphery of shaft pin 23 on both sides of gear 5 the bearings 8.3 and 8.4 are provided. The bearings 8.3 and 8.4 are formed by roller bearings 32 which are identical in design to the roller bearing 32 to support the drive shaft 7. To this extent each of the roller bearings 32 has several roller bodies 30, which are held in a closed annular chamber 31 with a grease filling.
For sealing of bearing 8.3 and 8.4 seals 9.3 and 9.4 are provided on the periphery of shaft pin 23 between gear 5 and bearings 8.3 and 8.4. The seals 9.3 and 9.4 are designed identical, each of the seals 9.3 and 9.4 having a pressure ring 10.3 and 10.4. The pressure rings 10.3 and 10.4 are held via spring devices 11.3 and 11.4 against the ends of gear 5 under bias. For this purpose each pressure ring 10.3 and 10.4 has a sealing shoulder 16.3 and 16.4, which is supported on the faces of gear 5.
The spring devices 11.3 and 11.4 in this practical example are formed by belleville spring stacks that are fastened in the mounting hole 35 by retaining ring 17.
With a spacing to pressure rings 10.1 and 10.2 the seal rings 12.3 and 12.4 are assigned to the bearings 8.3 and 8.4 and the periphery of the shaft pin 23, the sealing rings 12.3 and 12.4 being designed as groove rings that seal the annular space between the shaft pin 23 and the mounting hole 35 outward. A rinsing space 13.3 and 13.4 is formed on the periphery of shaft pin 23 between the pressure ring 10.3 and the sealing ring 12.3 and between the pressure ring 10.4 and the sealing ring 12.4. The rinsing spaces 13.3 and 13.4 are each connected through a rinsing channel 14.3 in housing plate 1.1 and a rinsing channel 14.4 in housing plate 1.2 to a rinsing connection 15.3 on housing plate 1.1 and a rinsing connection 15.4 on housing plate 1.2.
The mounting hole 35 is closed outward in housing plate 1.1 and housing plate 1.2 by a cover 27.
In the practical example depicted in
Practical examples depicted in
1 Pump housing
1.1 Housing plate
1.2 Housing plate
1.3 Center plate
1.4 Housing seal
1.5 Housing seal
2 Pump inlet
3 Pump outlet
4 Gear (driven)
5 Gear (idler)
6 Feed channel system
7 Drive shaft
7.1 Bearing end
7.2 Coupling end
8.1, 8.2, 8.3, 8.4 Bearing
9.1, 9.2, 9.3, 9.4 Seal
10.1, 10.2, 10.3, 10.4 Pressure ring
11.1, 11.2, 11.3, 11.4 Spring device
12.1, 12.2, 12.3, 12.4 Sealing ring
13.1, 13.2, 13.3, 13.4 Rinsing space
14.1, 14.2, 14.4, 14.5 Rinsing channel
15.1, 15.2, 15.3, 15.4 Rinsing connection
16.1, 16.2, 16.3, 16.4 Sealing shoulder
18 Mounting hole
19 Support housing
20 Support ring
21 Recess
22 Support bearing
23 Shaft pin
24 Pressure connection
25 Bearing shaft
26 Coupling shaft
27 Cover
28 Hole
29 Connection device
30 Roller body
31 Annular chamber
32 Roller bearing
33 Diameter shoulder
34 Bearing pin
35 Mounting hole
36.1, 36.2 Rinsing groove
Claims
1.-15. (canceled)
16. A gear pump comprising:
- two meshing gears configured to convey paints, said gears comprising a driven gear and an idling gear; and
- at least one drive shaft mounted to rotate, which is splined to the driven gear and is held by bearings in a pump housing, in which the drive shaft can be connected to a drive and in which a seal is assigned to the drive shaft on the periphery between the driven gear and one bearing, which includes a pressure ring lying against one face of driven gear,
- wherein a second seal with a second pressure ring is arranged on the opposite face of gear on the periphery of the drive shaft between a second bearing and the driven gear and wherein both pressure rings have a sealing shoulder opposite the driven gear, each of which is forced against the face of the driven gear by a spring device.
17. The gear pump according to claim 16, wherein the seals each have a sealing ring and wherein the sealing rings shield the bearings on both sides of the driven gear relative to the pressure rings and delimit on the periphery of the drive shaft a rinsing space formed between the pressure ring and the sealing ring.
18. The gear pump according to claim 17, wherein each of the rinsing spaces is connected by a rinsing channel in the pump housing to a rinsing connection.
19. The gear pump according to claim 17, wherein the two rinsing stations are connected to each other via several rinsing grooves between the drive shaft and the pressure rings and between the drive shaft and the driven gear.
20. The gear pump according to claim 16, wherein the bearings are formed to support the drive shaft by at least two roller bearings whose roller bodies are held in an annular chamber filled with a lubricant.
21. The gear pump according to claim 16, wherein the idling gear is splined to a shaft pin, which is supported on both sides of the idling gear by several bearings and wherein a seal is arranged on both sides of the idling gear on the periphery of the shaft pin, each of which has a pressure ring lying against the face of the idling gear.
22. The gear pump according to claim 21, wherein the seals each have a sealing ring and wherein the sealing rings shield the bearings on both sides of the idling gear relative to pressure rings and delimit a rinsing space formed on the periphery of the shaft pin between the pressure ring and sealing ring.
23. The gear pump according to claim 22, wherein each of the rinsing spaces is connected via a rinsing channel in the pump housing to a rinsing connection.
24. The gear pump according to claim 22, wherein the two rinsing spaces are connected to each other via several rinsing grooves between the shaft pin and the pressure rings and between the shaft pin and the idling gear.
25. The gear pump according to claim 21, wherein the bearings are formed to support the shaft pin through at least two roller bearings whose roller bodies are held in an annular chamber filled with lubricant.
26. The gear pump according to claim 16, wherein the pressure rings are formed from a ceramic material and wherein the sealing rings are each designed as a groove ring.
27. The gear pump according to claim 16, wherein the spring devices for pressing the pressure rings are each formed from a belleville spring stack.
28. The gear pump according to claim 16, wherein the faces of gears are formed from a ceramic material.
29. The gear pump according to claim 16, wherein the drive shaft is formed from a bearing shaft and a coupling shaft connected by a releasable rotary connection to bearing shaft, wherein the bearing shaft is connected to the driven gear within the pump housing and is supported by the bearings and wherein the coupling shaft is mounted to rotate outside of the pump housing in a support housing through a support bearing and can be connected to a drive on the free end.
30. The gear pump according to claim 29, wherein the support housing is firmly connected to the pump housing and is penetrated by the drive shaft in a recess.
Type: Application
Filed: Apr 2, 2008
Publication Date: Aug 5, 2010
Inventors: Ulrich Helbing (Burscheid), Arkardiusz Tomzik (Bergisch Gladbach), Dietrich Witzler (Rommerskirchen)
Application Number: 12/598,322
International Classification: F01C 1/18 (20060101); F01C 19/02 (20060101);
