WO1997047885A1

WO1997047885A1 - Bidirectionally operable, unidirectionally feeding pump

Info

Publication number: WO1997047885A1
Application number: PCT/DK1997/000255
Authority: WO
Inventors: Gunnar Lyshøj HANSEN; Jørn Holger KLAUSEN; Ingvard Mosby Madsen; Peter FRØSLEV
Original assignee: Danfoss A/S
Priority date: 1996-06-14
Filing date: 1997-06-12
Publication date: 1997-12-18
Also published as: AU3165697A; DK66396A

Abstract

The invention concerns a gear pump comprising a housing (12) provided with an inlet (17) and an outlet (19), an internally toothed ring (3) and an externally toothed gear wheel (2) which is arranged inside and meshing with the toothed ring. A cylindrical bore (7) is provided in the gear wheel, and a bearing unit (6) is arranged in the cylindrical bore for rotatable bedding of the gear wheel with respect to a rotation axis (A) arranged eccentrically in relation to the ring axis (C) and with the bearing unit being pivotable around the gear wheel axis. The gear ring is fixed to the housing, and means is provided for driving the gear wheel into an orbiting movement within and in relation to the gear ring to create a number of expanding chambers (16) and a number of contracting chambers (18) between the gear wheel and the gear ring. A commutator plate (20) is arranged next to the gear wheel and the gear ring in a space in the housing, and connected to the driving means in a way to rotate at the speed of the orbiting motion around the gear ring axis. The commutator plate has channels (32, 33) connecting the expanding channels and the contracting channels with the inlet and outlet respectively.

Description

Bidirect onally operable, unid rect onally feeding pump

The invention concerns a bidirectionally operable, unidi¬ rectionally feeding pump comprising a housing with an inlet and an outlet, an internally toothed ring having a ring axis, and an externally toothed gear wheel having a gear wheel axis, the gear wheel being arranged inside and mesh¬ ing with the ring, a cylindrical bore being provided in the gear wheel coaxially with the gear wheel axis, a bearing unit being arranged in the cylindrical bore for rotatable bedding of the gear wheel with respect to a rotation axis arranged eccentrically in relation to the ring axis, the bearing unit being pivotable around the gear wheel axis; and with a limiter for limiting the pivotation of the bear- mg unit to substantially 180 degrees.

DE 1.528.988 describes various pump embodiments. One em¬ bodiment comprises a housing with a shaft. An outer inter¬ nally toothed gear wheel is fixed to the housing and an inner externally toothed gear wheel is fixed to the shaft. The shaft comprises a first section and a second section. The second section has a centre, which is displaced by an eccentricity in relation to a centre of the first section. The centre of the first section is arranged in a rotation axis for the shaft. On shaft rotation the inner gear wheel will make an orbiting movement around the rotation axis.

However, the pump described in this document has one con¬ siderable disadvantage. It requires starting of the shaft with a fixed rotation direction, either clockwise or anti¬ clockwise. If the shaft starts in the opposite direction of the one fixed, the pump will work oppositely. Small pumps driven by small motors may experience that the motor starts the shaft in a random direction, either clockwise or anti- clockwise. This is not critical for small centrifugal pumps, ordinarily known from domestic appliances. However, if these small motors are used together with gear wheel pumps, special means are required to ensure the pump func¬ tion.

EP 0 486 164 Al describes a bidirectionally drivable gero- tor pump, which comprises a lobed annulus containing a lobed rotor journalled on a cylindrical boss, which is free to turn on an eccentric pin between two positions. The pump is driven by a shaft, which drives the lobed annulus and by meshing with the rotor, it rotates around the pin. The pressure difference between the one side of the pump and the other due to the direction of turning causes the boss to rotate between fixed positions. In this way the inlet and outlet ports have a fixed position independent of rota- tional direction of the drive shaft, causing the motor to have unidirectional feed.

While the annulus is rotating frictional forces occur be¬ tween the housing and the annulus. If the motor is a small and cheap electric motor the frictional forces between the annulus and the housing may be bigger than the starting torque of the motor. If the motor starts, the power loss caused by the frictional force is still high compared with the power from the motor.

The purpose of the invention is to provide a pump with small frictional power loss and small starting torque, where only simple means are required to ensure unidirec¬ tional pumping independently of the rotation direction of the driving shaft.

This task can be solved by means of a pump as described in the introduction, m that the ring is fixed m relation to the housing, and that the pump comprises driving means for driving the inner gear wheel into an orbiting movement within and in relation to the r ng to create between gear wheel and ring a number of expanding chambers and a number of contracting chambers, a commutator plate being arranged next to gear wheel and ring in a space m the housing, connected m a way that the commutator plate rotates at the speed of the orbiting motion around the ring axis, and that the commutator plate has channels connecting the expanding chambers with the inlet and the contracting chambers with the outlet.

This gives a bidirectionally operable, umdirectionally feeding pump, m which a bearing unit enables the gear wheel to switch between two positions in relation to the rotation direction of the driving means. The gear wheel changing its position causes that commutation of the pump remains unique m relation to the driving means. Thus a commutator can rotate with the driving means without having to change its position on a change of the rotation direc¬ tion.

The driving means may be a rotating shaft having within the cylindrical bore of the gear wheel a semicircular cross section with a first plane surface co-operating with a second plane surface on the bearing unit also having a semicircular cross section, such that the plane surface of the bearing unit bears against the plane surface of the shaft in a first position during clockwise shaft rotation, whereas the plane surface of the plane unit bears m a second position against the plane surface of the shaft during anticlockwise shaft rotation.

This enables a displacement of bearing unit and gear wheel in relation to the shaft, as the first and the second plane surfaces permit a displacement. During the switchover be¬ tween a first rotation direction and a second rotation direction of the shaft the gear wheel stands still in rela¬ tion to the ring. Only when the first plane surface of the shaft bears against the second plane surface of the bearing unit will the inner gear wheel be started by the shaft. This means that the required starting torque of the shaft is reduced, as the shaft is already rotating when the gear wheel starts in relation to the ring. If a motor operating the pump shaft starts in a direction opposite to the rota¬ tion direction of the latter operating situation, the torque required will be limited to a torque corresponding to a switching of the semicircular bearing unit from a first position to a second position. Only when the bearing unit has moved to a different position will the pump start displacement of a medium to be pumped. During the switching from the first position to the second position the motor reaches a rotation torque, which is able to overcome the starting torque of the pump. In cases where the motor oper¬ ating the pump shaft starts in the same direction as in the latter operating situation, the required starting torque may be higher than the torque which the motor is able to supply. Many inexpensive motors will automatically turn the rotation direction and try to start in the opposite direc¬ tion. The required starting torque will then, as mentioned above, be limited. Thus it is possible to use smaller and less expensive motors for the pump operation.

The cylindrical bore in the gear can have a first diameter D and the shaft can have a second diameter d and the ring axis is merging with the rotation centre of the shaft, the gear wheel axis during operation being displaced by an eccentricity e in relation to the rotation centre of the shaft. This enables displacement of the gear wheel by the eccentricity e in two opposite directions in relation to a neutral position.

The diameter D of the cylindrical bore in the gear wheel may be at least the shaft diameter d plus two times the eccentricity e. This gives a simple dimensioning of shaft and cylindrical bore.

The inlet can lead to a centrally arranged opening in a side plate connected via a first channel in the commutator plate to the expanding chambers between the ring and the gear wheel, also the contracting chambers might be con¬ nected to the outlet via a second channel in the commutator plate. By using a central connection for the inlet flow to the commutator plate, the inlet flow communication is inde¬ pendent of the rotional position of the commutator plate.

The second channel can comprise a cut-out in the commutator plate and a ring-shaped channel encircling the commutator plate and communicating with the cut-out, as set forth in claim 6. The ring-shaped channel is always in fluid commu¬ nication with the outlet independent of the position of the commutator plate.

The second channel can communicate with the outlet through an eccentric bore in a side plate of the pump.

The first channel can comprise a second cut-out in the commutator plate. The second cut-out makes a fluid communi- cation from a central bore in the side plate to the expand¬ ing chambers.

In an alternative embodiment the inlet and the outlet communicate with the channels via the driving shaft. This causes that the shaft is both the driving element of the pump and forms the basis of an inlet channel and/or an outlet channel.

The rotation of the gear wheel in relation to the ring may take place on a rotation of shaft and gear wheel, while the ring stands still. The rotation of the gear wheel in rela- tion to the ring may be caused by a rotation of the ring during standstill of shaft and gear wheel.

It is possible to let the pump and the motor driving the pump be parts of a complete unit, in which the motor can be an electromotor, and motor and pump have a common flange containing means for sealing along a common axis, and the flange may contain a common bearing.

The ring might be part of the pump housing. The ring will stand still in relation to the side walls of the pump. Thus friction between the ring and the side walls will be elimi¬ nated. Friction between ring and pump housing, a common fact in a gerotor machine, is also eliminated.

In the following the invention will be described with ref¬ erence to the enclosed drawings, showing:

Fig. 1 A schematic view of a pump embodiment according to the invention in a resting position for mounting

Fig. 2 A schematic view of a pump embodiment in a posi¬ tion for switching from mounting position to a first operating situation Fig. 3 A schematic view of the pump embodiment in the first operating position

Fig. 4 A schematic view of the pump embodiment in a position for switching from the first operating position to a second operating position Fig. 5 A schematic view of the pump embodiment in the second operating position

Fig. 6 A first detailed drawing of a preferred pump embodiment according to the invention Fig. 7 A second detailed drawing of the preferred pump embodiment according to the invention Fig. 1 shows an embodiment of a pump according to the in¬ vention in a position for mounting. The figure shows an externally toothed gear wheel 1, 2, an internally toothed ring 3,4, a shaft 5 and a bearing unit 6. The shaft 5 ex- tends into a cylindrical bore 7 in the gear wheel 1. The shaft 5 has a plane surface 8, being plane in the shown embodiment. The shaft has a diameter d, and the cylindrical bore has a diameter D.

The bearing unit 6 is arranged in the bore 7 in the gear wheel 1, and also has a semicircular cross section t₆. The cross section t₆ of the bearing unit 6 is approximately half as big as the diameter of the hole 7 in the gear wheel 1. The bearing unit 6 has a plane surface 9, being plane in the shown embodiment. The shaft 5 has a rotation axis A displaced by an eccentricity e in relation to a centre C of the bore 7 in the gear wheel 1.

On rotation of the shaft 5 the gear wheel 1 will mesh with the ring in an orbiting movement, and rotate in the oppo¬ site direction around the shaft.Fig. 2 shows a switching from the mounting position in fig. 1 to a first operating position (see fig. 3) . The shaft 5 has started anticlock¬ wise rotation and has rotated by an angle rotation α. A first edge of the plane surface 8 of the shaft 5 bears against the plane surface 9 of the bearing unit 6.

Fig. 3 shows a first operating position for the pump ac¬ cording to the invention. The shaft 5 has rotated one angle rotation β anticlockwise in relation to the position shown in fig. 1. The angle β is approximately 90°. One rotation of the shaft 5 has brought along the bearing unit 6, and the whole plane bearing surface 8 of the shaft 5 now bears in a first position against the plane bearing surface 9 of the bearing unit 6. The shaft rotation β of about 90° has not yet made the gear wheel 1 rotate. Only a further anticlockwise rotation of the shaft 5 will make the gear wheel 1 rotate. The shaft 5 and the bearing unit 6 have thus already started rotating, when the gear wheel 1 starts rotating. The shaft has made a rotation of 90° at a low torque. This position will remain unchanged during operation.

Fig. 4 shows a switching from the first operating position shown in fig. 3 to a second operating position (see fig. 5) . The shaft 5 has started clockwise rotation and has rotated one angle rotation δ. A second edge 11 of the plane surface 8 of the shaft 5 bears against the plane surface 9 of the bearing unit 6. The angle δ is 90°.

Fig. 5 shows a second operating position for the pump ac¬ cording to the invention. The shaft 5 has rotated one angle rotation γ clockwise in relation to the position shown in fig. 3. The angle γ is 180°. On this rotation the shaft 5 has brought along the bearing unit 6, and the whole plane surface 8 of the shaft 5 now bears in a different position against the plane surface 9 of the bearing unit 6.

On the shaft rotation γ of 180° the gear wheel 1 has not yet started rotating. Only a further clockwise rotation of the shaft 5 will make the gear wheel 1 start rotating. Thus, the shaft 5 and the bearing unit 6 are already rotating, when the gear wheel 1 starts to mesh with the ring 3.

The switching shown in fig. 4 from a first operating posi¬ tion to a second operating position will take place, if the shaft 5 of the pump according to the invention starts ro¬ tating in a direction, which is opposite to the direction in a previous, first operating situation. The switching from the first operating position to the second operating position depends on a distance between the plane surface 8 of the shaft 5 and the plane surface 9 of the bearing unit 6 in a position, where the plane surfaces 8, 9 are paral¬ lel, as shown in fig. 1. In the shown embodiment, where the bearing unit 6 has a cross section t₆, which is half the diameter ti of the bore 7, and where the shaft has a semi¬ circular cross section, the distance between the plane surface 8 of the shaft 5 and the plane surface 9 of the bearing unit 6 is equal to the eccentricity e between the rotation axis A of the shaft 5 and the centre C of the bore 7.

Fig. 6 and 7 show two different sections, at right angles to each other, of a possible embodiment of the pump. It comprises a housing 12 having a suction pipe branch 17 and a pressure pipe branch 19. The housing comprises a side plate 14 to which the ring 3 is fixed, and inside the ring 3, also bearing on the side plate 14, the gear wheel 1 is arranged. The gear wheel 1 has a cylindrical bore 7, partly filled by the semicircular bearing unit 6, and by a shaft 5 arranged in a bore in the side wall 14. Opposite the side wall 14 the gear wheel 1 and the ring 3 are supported by a commutator plate 20 driven by the shaft 5. A circular pas¬ sage 31 extends around the commutator plate 20 and is con¬ nected with a recess 22 in the commutator plate.

The commutator plate 20 also comprises a recess 21, from which two channels 32, 33 form the connection to a third recess in the commutator plate 20 for admission of the semicircular end of the shaft 5. From the commutator plate centre through a side plate 13 there is a bore 25 having connection to the suction pipe branch 17. A spacer 30 having the same thickness as the ring 3 and the gear wheel 1 is also arranged between the side plates 13 and 14. A spacer 29 with the same thickness as the commuta¬ tor plate 20 is also available. Together with the spacers 30 and 29 the side plates 13 and 14 are joined by the bolts 15 and 28 to one unit. Sealmgs m the shape of O-rings 27 are available around the flow connections 23, 25 and 24, 26 between the side plate 13 and the housing 12.

In operation the pump 12 has a suction pipe branch 17 from which a suction connection 23 forms fluid communication through an opening 25 in the side plate 13 to a central recess m the side plate 13 for admission of the extension of the rotating shaft 5. From the recess channels 32, 33 in the commutator plate 20 are connected with the recess 21 m the commutator plate 20. From the recess 21 there is a fluid connection to the expanding volume between the orbit¬ ing gear wheel 1 and the stationary ring 3. As the commuta¬ tor plate 20 follows the rotation of the shaft, or, in other words, rotates at the orbiting speed of the gear wheel, the recess 21 will remain across the expanding cham¬ bers between gear wheel 1 and ring 3.

A medium transport will take place between the orbiting gear wheel 1 and the stationary ring 3 to the contracting chamber, from which an additional recess 22 forms the pres^¬ sure connection from the contracting chamber to the ring channel 31. From the side plate 13 through a bore 26 there is a connection to the pressure channel 24, from which there is a connection to the pressure pipe branch 19.

Claims

Patent Claims

1. A bidirectionally operable, unidirectionally feeding pump comprising a housing (12) with an inlet (17) and an outlet (19), an internally toothed ring (3) having a ring axis, and an externally toothed gear wheel having a gear wheel axis, the gear wheel being arranged inside and meshing with the ring (3), a cylindrical bore (7) being provided in the gear wheel (2) coaxially with the gear wheel axis, a bearing unit (6) being arranged in the cylindrical bore (7) for rotatable bedding of the gear wheel (2) with respect to a rotation axis arranged eccentrically in relation to the ring axis, the bearing unit (6) being pivotable around the gear wheel axis; and with a limiter for limiting the pivotation of the bearing unit (6) to substantially 180 degrees, charac¬ terised in that the ring (3) is fixed in relation to the housing (12), and that the pump comprises driving means (5) for driving the inner gear wheel (2) into an orbiting movement within and in relation to the ring (3) to create between gear wheel (2) and ring (3) a number of expanding chambers and a number of contract¬ ing chambers, a commutator plate (20) being arranged next to gear wheel (2) and ring (3) m a space in the housing (12), connected m a way that the commutator plate (20) rotates at the speed of the orbiting motion (5) around the ring axis, and that the commutator plate has channels connecting the expanding chambers with the inlet and the contracting chambers with the outlet.

2. A pump according to claim 1, characterised in that the driving means comprise a rotating shaft (5) having within the cylindrical bore (7) of the gear wheel (2) a semicircular cross section with a first plane surface co-operating with a second plane surface on the bearing unit (6) also having a semicircular cross section, such that the plane surface of the bearing unit (6) bears against the plane surface of the shaft (5) m a first position during clockwise shaft rotation, whereas the plane surface of the bearing unit (6) bears m a dif¬ ferent position against the plane surface of the shaft (5) during anticlockwise shaft rotation.

3. A pump according to claim 1 or 2, characterised in that the cylindrical bore (7) m the gear wheel (2) has a first diameter (D) , that the shaft (5) has a second di¬ ameter (d) , and that the ring axis is merging with the rotation centre of the shaft (5), the gear wheel axis during operation being displaced by an eccentricity (e) in relation to the rotation centre of the shaft.

4. A pump according to one of the claims 1 to 3, charac¬ terised in that the diameter (D) of the cylindrical bore (7) in the gear wheel (2) is at least the shaft diameter (d) plus two times the eccentricity (e) .

5. A pump according to one of the claims 1 to 4, charac¬ terised in that the inlet (17) leads to a centrally ar- ranged opening (23) in a side plate (13) connected via a first channel (21) in the commutator plate (20) to the expanding chambers, and that the contracting cham¬ bers are connected to the outlet (19) via a second channel (22, 31) in the commutator plate.

A pump according to one of the claims 1 to 5, charac¬ terised in that the second channel (22, 31) comprises a cut-out (22) in the commutator plate and a ring-shaped channel (31) encircling the commutator plate and commu- nicating with the cut-out (22) .

7. A pump according to one of the claims 1 to 6, charac¬ terised in that the second channel communicates with the outlet through an eccentric bore in a side plate of the pump.

8. A pump according to one of the claims 1 to 7, charac¬ terised in that the first channel comprises a second cut-out (21) in the commutator plate.

9. A pump according to one of the claims 1 to 8, charac¬ terised in that the inlet and the outlet communicate with the channels via the driving shaft.