Flow detector with a housing

A flow detector has a housing (1) with tongues (8), which allow to anchor it to a support to withstand pulling forces. The housing further comprises pegs (41) provided to mate with openings or recesses in the same support, which allow to secure it against lateral forces. The tongues (8) and pegs (41) are mounted to a hull (7) of a housing (1) of the detector, which carries on its opposite side an inlet (4a) and an outlet (4b) for the fluid to be measured. Connectors (5) are provided on the same side as the tongues (8) and the pegs (41) for connecting the detector to an external system. This design is robust and allows to mount the detector to the support in quick and secure manner.

BACKGROUND OF THE INVENTION

The invention relates to a flow detector with a housing, an inlet and an outlet. It also relates to an assembly of such a flow detector and a support plate.

An embodiment of such a flow detector is shown in US 2004/0118218. It comprises a housing having opposite first and second sides. An inlet and an outlet for the fluid are arranged at the first side of the housing. The inlet and outlet are connected by means of a flow channel arranged in the housing. A sensor chip is located at a side of the flow channel and measures the flow therein. At the second side of the housing, electrical connectors are provided for connecting the flow detector to an external system. The connectors extend from the second side of the housing and can e.g. be soldered into a printed circuit board. The connectors are held in a filler material of glass, which, however, may be damaged when mechanical strain is exerted to the housing.

BRIEF SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a flow detector of this type with higher mechanical stability.

In a first aspect of the invention, this object is achieved by a flow detector comprising

a housing having opposite first and second sides,

an inlet and an outlet for said fluid arranged at the first side of said housing,

a flow channel arranged in said housing and connecting said inlet and said outlet,

a sensor chip arranged at said flow channel and adapted to measure said flow in said flow channel,

electrical connectors connected to said sensor chip for connecting said flow detector to an external system, wherein said connectors extend from the second side of said housing, and

a plurality of tongues, in addition to said connectors, extending away from the second side of said housing for mechanically mounting said housing to an external support.

In a second aspect of the invention, this object is achieved by a flow detector comprising

a housing having opposite first and second sides,

a hood formed by a single plastic piece and forming said first side of said housing,

an inlet and an outlet for said fluid arranged at the first side of said housing, wherein said inlet and said outlet are integrally attached to said hood and extend away from said hood,

a flow channel arranged in said housing and connecting said inlet and said outlet,

an internal printed circuit board arranged in said hood,

a sensor chip arranged on said internal printed circuit board at said flow channel and adapted to measure said flow in said flow channel,

electrical connectors connected to said sensor chip for connecting said flow detector to an external system, wherein said connectors extend from the second side of said housing and are mounted to said internal printed circuit board, and

a plurality of tongues, in addition to said connectors, integrally connected to said hood and extending perpendicularly to said internal printed circuit board away from the second side of said housing for mechanically-mounting said housing to an external support.

In a third aspect of the invention, the object is achieved by an assembly of a flow detector for measuring a flow of a fluid and a support plate, said assembly comprising

a housing having opposite first and second sides, with said second side lying against a surface of said support plate,

an inlet and an outlet for said fluid arranged at the first side of said housing and extending in a direction perpendicular to said support plate,

a flow channel arranged in said housing and connecting said inlet and said outlet,

a sensor chip arranged at said flow channel and adapted to measure said flow in said flow channel,

electrical connectors connected to said sensor chip connecting said flow detector to said support plate, wherein said connectors extend from the second side of said housing into said support plate, and

a plurality of tongues, in addition to said connectors, extending perpendicularly to said support plate and away from the second side of said housing into openings in said support plate for mechanically mounting said housing to said support plate.

Accordingly, a plurality of flexible tongues is provided, in addition to the connectors, extending away from the second side of the housing, i.e. extending into a direction away from said housing. These tongues can be used for mechanically mounting the housing to an external support, i.e. a support external to said housing, such as to the printed circuit board mentioned above. Accordingly, mechanical strain can now be received by the tongues, which allows the detector to withstand additional strain.

Advantageously, the tongues have free ends suited for insertion into openings of the external support. Advantageously, they have a comparatively thin neck and a comparatively thick head, with the neck extending from the second side of the housing to the head. Such tongues allow to anchor the detector in suitably sized holes of the support and to hold it therein against pulling forces perpendicular to the support surface. However, in an alternative embodiment, the tongues may also have constant or tapering diameter if they are to secure the device against lateral movements.

In a further advantageous embodiment, one or more pegs are provided at the second side of the housing, in addition to the connectors and the tongues. These pegs project perpendicularly from the second side of the housing. The diameter of the pegs remains constant or decreases with increasing distance from the second side of the housing. Such pegs allow to secure the detector in suitably sized holes of the support and to hold it therein against shearing forces parallel to the support surface.

Advantageously, the housing comprises a hood forming its first side, with the tongues and/or pegs being integrally attached to the same. Such a design allows to transfer mechanical strain from the first side of the housing (such as exerted by tubes attached to the inlet and outlet) directly to the support.

DETAILED DESCRIPTION OF THE INVENTION

The detector ofFIGS. 1-6comprises a housing generally denoted by1having a first side2(FIG. 3) formed by a first, substantially flat surface of the housing and a second side3(FIG. 1) formed by a second, substantially flat surface of the housing. An inlet4aand an outlet4b(FIG. 3) project from first side2, each formed by a hollow stub suited for being connected to a tube guiding the fluid. A series of electrical connectors5, each formed by a metal pin6, project perpendicularly from second side3of housing1(FIG. 1).

As can best be seen fromFIG. 2, housing1comprises a hood7, which forms first side2. Hood7is a single plastic piece e.g. manufactured by injection molding. Hood7carries at least two, advantageously four tongues8, which extend from second side3. They serve to mechanically mount housing1to a support or support plate10, such as an external printed circuit board, as shown inFIG. 5. Support or support plate10is external to housing1, i.e. not an integral part thereof. Second side3of housing1rests against a surface of support plate10.

As can be seen e.g. fromFIG. 3, the subs of inlet4aand outlet4bextend parallel to the tongues8, namely in a direction perpendicular to the surface of the second side3of housing1as well as perpendicular to support plate10.

As can be seen fromFIG. 2, hood7forms a recess11, which receives a plate12, e.g. a printed circuit board. To distinguish this printed circuit board from the external printed circuit board formed by plate10, it is called the internal printed circuit board.

As can be seen fromFIGS. 4 and 5, plates10and12are arranged parallel to each other. Plate12carries on a first side13thereof, a sensor chip14. Sensor chip14is e.g. a thermal flow sensor such as described in US 2002/0043710. The backside of sensor chip14lies flush against plate12, while the front side of sensor chip14, which carries the flow sensing elements, is facing a flow channel16that connects inlet4awith outlet4b. Plate12also carries the connectors5, i.e. the connectors5are mounted to plate12. The connectors5project from a second side14of plate12. Leads on plate12as well as bond wires are used to electrically connect the connectors5to contact pads on sensor chip14.

Plate12forms part of the second side3of housing1. It is held in recess11by a frame17, which is also inserted into recess11and has been welded to its walls. Frame17pushes against second side14of plate12, thereby holding it in place. A sealing ring18of an elastic material, such as silicone, is arranged between frame17and plate12for preventing the fluid from exiting at second side3of housing1. Sealing ring18in particular covers a gap19between the outer rim of plate12and the inner walls of hood7for sealing the same. Sealing ring18obviates the need for a fluid tight seal right at the rims of flow channel16—such a seal would be difficult to achieve, in particular in the region of sensor chip14.

Flow channel16is formed as a groove extending along an inner side of a wall20of hood7. Wall20forms first side2of housing1. Flow channel16is covered by plate12and sensor chip14.

The design of the inner side of wall20is best seen fromFIG. 6. Apart from the groove forming flow channel16, wall20further comprises a recess21, which serves to provide room for the bond wires and a protective glob used to connect sensor chip14to plate12.

As can be seen fromFIG. 6, flow channel16extends in a plane parallel to first side2of housing1. It has a first end23connected to inlet4aand a second end24connected to outlet4b. First end23and/or second end24, advantageously both of them, are looped around at least 180° of inlet4aand outlet4b, respectively. In this context, “looped around at least 180°” means that, the path of the end section is wound at least around 180° of the circumference of the inlet and outlet, respectively.

This allows to increase the actual length of flow channel16, which in turn decreases the risk of turbulences at the location of semiconductor chip14.

Hood7of housing1is further provided with screw holders for receiving attachment screws or attachment pins, which allow, if necessary, to mount housing1more securely to a support. In the embodiment shown here, two types of screw holders are provided, which will in the following be called “first screw holders” and “second screw holders”. The first screw holders26extend parallel to first side2and second side3of housing1, while the second screw holders27extend perpendicular thereto. Thus, the first screw holders are structured to hold a screw parallel to first side2and second side3, while the second screw holders are structured to hold a screw perpendicular thereto. To allow to mount the same housing1in two different orientations, namely with side3parallel to a support10, such as shown inFIG. 5(where the second screw holders27can be used to attach hood7to base10), or with side3perpendicular to support10, such as shown in the embodiment ofFIG. 8(where the first screw holders26can be used to attach hood7to base10).

As can be seen, the embodiment shown here has a total of four screw holders, namely one first and one second screw holder on a third side30of housing1(FIG. 3), and one first and one second screw holder on a fourth side31of housing1, with third side30being opposite to fourth side31and both of them being perpendicular to first side2and second side3of housing1.

A larger number of screw holders could be provided as well, in particular for large housings1.

Each first screw holder is formed by a first through-hole through hood7and each second screw holder27is formed by a second through-hole through hood7. The through-holes are adapted to e.g. receive a screw or pin. In order to achieve a compact design, the first through-hole and the second through-hole on the same side of housing1intersect.

As mentioned, the tongues8serve to anchor housing1in support10and to secure it against pulling forces. For this purpose, each tongue8is provided with a thin neck34and a thicker head35(FIG. 1). Neck34extends between hood7of housing1and head35. Head35, whose maximum diameter exceeds the diameter of neck34, is wedge-shaped and tapered towards its end36facing away from housing1. Hence, each tongue8can easily be inserted into suitably positioned and sized openings37in support10(seeFIG. 5), where they snap in once that head35has passed fully. Hence, the heads35form hooks that hold housing1tightly in support10, securing it against pulling forces.

For inserting the tongues8into the holes37of support10, the tongues need to be deformed laterally. To facilitate such a deformation, each tongue is mounted in a recessed section38of the side walls of hood7, as shown inFIGS. 1 and 3, which allows to increase the length of neck34, thereby making it more resilient.

As can best be seen fromFIG. 6, the tongues are arranged “with rotational asymmetry in respect to any axis of rotation extending through the first and second side of the housing”. This is to be understood such that there is no axis of rotational symmetry perpendicular to the first and second side2,3of housing1. In other words, on a support10parallel to first and second side2,3, the detector can be mounted in a single orientation only if the tongues8are to be inserted into the openings37. Thereby it can be assured that the measured signal has the correct sign and the connector5is oriented properly. In the embodiment ofFIG. 6, this is achieved by placing one tongue closer to the longitudinal axis40of housing1than the other tongues.

The resilience of the necks34facilitates the insertion of the tongues8into the holes37, but it renders the tongues8poorly suited to withstand lateral forces against housing1. In addition to this, the holes37in support10must have a larger diameter than the necks34for allowing passage of the heads35, which can give rise to lateral play of the fully inserted housing1. Hence, in addition to the tongues8, housing1comprises at least one, advantageously at least two, pegs41projecting perpendicularly from second side3. These pegs41can best be seen inFIGS. 1 and 6. Each peg41has a diameter that remains substantially constant or decreases with increasing distance from second side3of housing1, such that it can be inserted tightly into a suitably sized hole42of support10(FIG. 5). The pegs41are therefore able to secure housing1against lateral movements in respect to support10.

The pegs41are, as the tongues8, integrally attached to hood7.

As mentioned, the connectors5are formed by a plurality of pins6. In the embodiments shown here, the pins6are arranged in a single line. They project perpendicularly from second side3of housing1.

If the detector is to be mounted in the position ofFIG. 5, the pins6are advantageously straight such that they can be inserted into suitable openings in position10.

If, however, the detector is to be mounted on a support10perpendicular to first side2and second side3, angled pins6′ have to be used, as shown inFIGS. 7 and 8. These angled pins have a first section10aextending substantially perpendicularly from second side3of housing1and a second section10bextending at a right angle to first section10a.

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practised within the scope of the following claims.