Pumps – Condition responsive control of pump drive motor – Responsive to change in rate of pump fluid flow
Reexamination Certificate
2000-03-14
2001-08-14
Walberg, Teresa (Department: 3742)
Pumps
Condition responsive control of pump drive motor
Responsive to change in rate of pump fluid flow
C417S038000
Reexamination Certificate
active
06273684
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a centrifugal pump unit and more particularly, a centrifugal pump unit comprising an electromagmetic flow switch and a two-armed, pivotally mounted lever.
Centrifugal pump units are used today for increasing the pressure, as so-called booster pumps. In particular, where the central water supply does not constantly have an adequately high operating pressure it is usual to install storage tanks in the roof, wherein then the water is filled from the central water supply up to a certain degree of filling into the storage tank and from here when required flows to the water tapping location in the households located thereunder. By way of this, water may also be tapped when in the central supply conduit the delivery pressure falls or the supply is stopped. Since the static pressure of account of the height difference between the storage tank and the tapping location is mostly only very slight, when electrical or gas-driven water heaters or comparable apparatus which demand a minimum water through-flow are used, it is then necessary to use such booster pumps. Booster pumps are typically used for pressure increases of 0.6 to 0.8 bar with a delivery flow of 0.5 to 1 m
3
/h.
Since the pressure increase is only required when water is removed, thus when the water heater or a similar apparatus is operated, these pumps are equipped with a flow switch which controls the electric motor of the centrifugal pump unit. When a tap valve is opened at a tapping location and water begins to flow on account of the low present static pressure, this flow switch is stimulated which thereupon switches on the motor of the centrifugal pump unit in order in this manner to produce the desired pressure increase.
Such centrifugal pump units belong to the state of the art. A known such unit is specially designed for this application purpose and comprises a terminal box which covers the motor housing up to the pump housing and here comprises an electromagnetic switch device which is in active connection with a two-armed, pivotably mounted lever arranged in this region in the flow path. This lever with one arm projects in the flow path and on the other arm carries a magnet which controls the switch device in the form of a reed contact.
The disadvantage with this type of construction is the fact that almost all components are usable exclusively for this pump type, in particular that the terminal box with regard to design is adapted to this special centrifugal pump unit.
SUMMARY OF THE INVENTION
Proceeding from this it is the object of the invention to provide a centrifugal pump unit with regard to design such that to a great extent standardised components from mass-produced manufacture may be applied in order to reduce the manufacturing costs.
In one aspect of the invention, this invention comprises a centrifugal pump unit with a flow switch arranged within the pump housing in the flow path of the delivery fluid and essentially consisting of an electromagnetic switch device and a two-armed, pivotally mounted lever whose one arm projects into the flow path and whose other arm carries a magnet which is in contact-free active connection with the switch device, wherein the switch device is arranged within a terminal box mounted on the unit housing, wherein at least the part of the lever carrying the magnet is surrounded by a switch housing which is hermetically sealed to the outside and which is separated from the terminal box and is arranged neighboring this.
The basic concept of the invention is the arrangement of the terminal box spacially and physically from the flow switch in order in this way to be able to apply a terminal box as is also applied for other centrifugal pump units of this size, in particular, heating circulatory pumps. Furthermore by way of the switch housing incorporated into the pump housing in a cartridge-like manner the centrifugal pump unit may be selectively used with or without a flow switch by placing on a suitable sealing cap. The pump unit is thus not only simplified in design, but is also more comprehensive with regard to the application use.
Within the switch housing which to the outside is hermetically closed and is sealed with respect to the pump housing, there is located according to the invention the switch lever which with its one arm projects into the flow path and whose other arm carries a magnet. The magnet thus lies within the switch housing, whilst the switch device as previously remains arranged in the terminal box. The terminal box and switch housing are thus only magnetically actively connected to one another, and are otherwise however spacially and physically completely separated from one another. It is to be understood that the terminal box and the switch housing are to be arranged neighbouring one another in order to ensure the magnetic active connection. Otherwise the terminal box in the known way and manner may be fastened on the motor housing wherein also sealings are to be provided only for the electrical safety, sealings for the delivery medium however are completely done away with. Since the switch housing is hermetically closed towards the outside, thus where, after installation into the pump housing, it is accessible from the outside, a sealing with respect to the pump housing is sufficient in order to ensure a sealing with respect to the delivery flow to the outside. For this a simple ring seal is sufficient if the part of the switch housing projecting into the pump housing is designed cylindrically. Such a cylindrical shape with suitable openings in the region of the flow channel is not only advantageous with regard to the previously mentioned sealing but also simplifies the assembly, since by simple turning any twistings on application may be removed.
Preferably, the switch housing is designed such that the housing part lying outside the pump housing is formed completely closed. In this manner, no sealing arrangements within the switch housing are necessary, the tightness of the arrangement is reliably ensured.
Usefully, the lever pivotably mounted within the switch housing is formed by a one-piece injection moulded part which not only comprises both lever arms, thus the arm projecting in the flow path as well as the arm carrying the magnet, but furthermore, also a pivoting axle with which the lever is mounted within the housing.
In order to guarantee that the lever arm projecting in the flow path is deflected out already with a very low through-flow, it is useful to form this paddle-shaped, thus such that when it lies transverse to the flow it forms a large flow resistance and in the direction of the flow it forms as low a resistance as possible. The outer contour of the paddle-like lever arm should at the same time correspond essentially to the flow channel cross section in order to permit a sensitive as possible reaction.
Although the solution according to the invention permits the lever with the two lever arms to be arranged in the delivery fluid, it is thus not necessary within the switch housing to arrange a seal between the two lever arms—it is however useful to protect, with respect to the switch housing, the lever arm which carries the magnet as well as the pivoting axle by way of an elastic sleeve. In this manner contamination or deposits are prevented from penetrating in this region of the switch housing or flows forming within this housing part are prevented.
Preferably, the lever arrangement is designed such that the flow force acting on the lever reduces with an increasing deflection of the paddle-like lever out of the flow path. On the one hand this may be effected by a suitable shaping of the paddle-like lever arm and on the other hand may be supported by a suitable design of the lever restoring arrangement. The lever restoring is effected preferably also by way of magnet force, wherein for this within or also outside the switch housing a further magnet (auxiliary magnet) may be provided, which according to the arrangement acts in a repelling or attracting manner. Usefully the auxiliary magnet
Jensen Niels Due
Nórgaard Carsten
Schmidt Jorgen
Fastovsky L
Grundfos a/s
Jacox Meckstroth & Jenkins
Walberg Teresa
LandOfFree
Centrifugal pump unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Centrifugal pump unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Centrifugal pump unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2442059