Patent Description:
Modules for extending the range of functions of a centrifugal pump's control unit are generally known. For example, the company WILO SE offers a function module, also called IF module (IF = interface), under article number <NUM> for its centrifugal pump series named 'Stratos', which expands the control electronics of said pump by a serial communication interface for BACnet in order to be able to connect the centrifugal pump to a building automation system. The IF module provides both the electrical connection (here RS485) for connecting the pump to a BACnet and the necessary communication protocol. A similar function module is offered by WILO SE under part number <NUM>, which achieves a corresponding extension of the pump through the industry standard MODBUS. Thus, a user can optionally supplement the centrifugal pump and specifically adapt it to his needs and the local communication infrastructure. The two function modules are plugged alternatively into the same electrical interface of the centrifugal pump unit.

Meeting current and future customer needs requires a steady increase in the functional scope of centrifugal pumps or their pump electronics respectively, especially with regard to wired or wireless communication interfaces. As existing communication technologies continue to develop (e.g. mobile communications like <NUM> (GSM) -> <NUM> (UMTS) -> <NUM> (LTE Advanced) -> <NUM>; Bluetooth -> Bluetooth Low Energy) and new technologies (ZigBee, enOcean, RFID) are added, there is also a demand for rapid availability of functionally enhanced centrifugal pumps on the market, which is difficult to meet due to the necessary product development time and, in particular, the required product certification, especially for radio-based communication technologies integrated in the pump electronics. Additionally, despite the increase in functionality, there is the desire to be cost-effective.

A solution that meets all these requirements is to provide functions or function groups on a modular or building block basis in the form of electronic extension module that supplement the main product, i.e. the centrifugal pump unit or its pump electronics respectively. This reduces the development time and the duration until availability on the market, because the development can essentially be limited to a new electronic extension module. Furthermore, no recertification of the main product is required, as certification is limited to the electronic extension module. This means that new technologies can be combined with or integrated into the main product in a timely manner. Furthermore, since extension modules permits to equip the main product with specific functions or function groups on an "as needed basis" in a targeted manner, functionalities that are not required by a customer can be omitted from the main product, resulting in an overall cost saving.

Considering that the size of future extension modules cannot be anticipated as it depends on the space the electronics inside occupies that, in return, depend on the function or function groups the module provides as well as the technology implementing the function or functions, the module should be arranged outside the pump's terminal box. Consequently, the size of the terminal box can be kept small.

However, the externalization of functions or function groups into electronic extension modules requires certain demands on the electrical interface between the electronic expansion module and the pump electronics as well as on the arrangement or mounting of the expansion module at the terminal box. Among other things, the aspects of operational safety, robustness, susceptibility to faults, protection against contact, insulation, tightness, handling and fastening must be taken into account. Furthermore, a uniform mounting mechanism is desirable, so that different expansion modules, in particular differing in their size, can be plugged to the same electrical interface of the pump electronics and can be fixed easily and securely at the terminal box in the same manner.

Therefore, it is an object of the present invention to provide a mounting mechanism between a pump's terminal box and an electronic extension module that fulfils the mentioned needs.

This object is solved by an arrangement according to claim <NUM>. Advantageous further developments are given in the depending claims and/ or are described hereinafter. According to the present invention, it is proposed an arrangement comprising a terminal box for a centrifugal pump accommodating a pump control, an electronic extension module extending the pump control by at least one additional hardware and/or software function, and at least one locking element for securely holding the module at the terminal box, wherein the module is removeably mountable at the terminal box and has a pluggable electric interface extending from the underside of a base plate through an opening into the terminal box to electrically connect the pump control for establishing a data link. The locking element is slidably accommodated within a cavity of the terminal box and can be moved tool-less from a first position to a second position and removed from said second position to said first position by means of a tool. The first position is an open position enabling plugging the module at the terminal box, whereas the second position is a locking position preventing unplugging the module. Furthermore, the locking element has, at a first side, a resilient latch engaging with either a first recess at the terminal box keeping the locking element in the first position, or a second recess at the terminal box keeping the locking element in the second position. The locking element is configured to give free way for plugging the module in the first position, and to arrest the module in the second position by means of at least one projecting bar arranged at a second side of the locking element. The module comprises at least one pillar extending in parallel to the electric interface from the base plate, whereas the pillar is insertable through an opening into the cavity, when the locking element is in the first position, and the pillar has a notch for engaging with the bar in a form-fit manner, when the locking element is in the second position.

In a preferred embodiment, the latch is arranged at the end of a resilient arm. I other words, the resilient arm enables the latch to be removed from the first or second recess by pushing the arm backwards during the movement of the locking element. An arrangement of this kind is very simple, robust und reliable. Preferably, the other end of the arm extends integrally into a central core portion of the locking element.

The module can comprise at least one pillar on either side of the electric interface each of which having a notch for engaging with one locking element. In addition, the arrangement further comprises two locking elements each of which having at least one respective bar engaging, in a form-fit manner, with the notch of a corresponding pillar, when the locking element is in the second position, so that the module cannot be unplugged again. This means that the extension module is fixed at two points, one point at either side of the electric interface. The two locking element can be arranged symmetrically with respect to the electric interface.

In a further development, additionally or alternatively to the previous embodiment, the module comprises two consecutive pillars each having a notch, and the locking element or elements comprise(s) an overall longitudinal shape having two consecutive projecting bars each of which engaging with one of the notches of the consecutive pillars in a form-fit manner in the second position. This means that the at least one locking element arrests the extension module at two points. In an embodiment having two locking elements, and two times two consecutive pillars with a corresponding notch each, the extension module is fixed at four points at the terminal box. This embodiment is preferably used if the extension modules has a large housing.

Preferably, the latch comprises a leading forehead of rounded shape. This eases moving the locking element from the first to the second position and pushing the arm backwards with little force.

In a preferred embodiment, the latch has the shape of a hook comprising a detention surface interacting with a front inner sidewall of the first recess to be retained by the first recess. Correspondingly, the first recess can comprise a front inner sidewall configured to prevent the latch being moved out of the cavity. In other words, said inner sidewall is an abutment and, in cooperation with the hook shaped latch, limits the movement of the locking element beyond the first position when it is moved from the second to the first position. It follows that the front inner sidewall of the first recess keeps the latch within the first recess and, consequently, keeps the locking element in the first position, so that it cannot be removed inadvertently from or fall out of the cavity.

In an advantageous further development, the first recess can comprise a rear inner sidewall configured to push the latch backwards during the movement from the first to the second position, more specifically at the beginning of said movement. Thus, when the locking element is pushed to move from the first to the second position, the leading forehead of the latch is pushed against the rear inner sidewall of the first recess that deflects the acting force towards the locking element, resulting, thanks to the resilience of the arm, in an evasive action of the latch. The latch, with continued movement of the locking element into the cavity, slides along the rear inner sidewall that pushes the latch increasingly backwards to a core portion of the locking element thereby bending the arm. Consequently, the latch moves more and more out of the first recess. Thus, the rear inner sidewall of the first recess contributes to easily moving the locking element from the first to the second position with little force. Preferably, said rear inner sidewall is plain and arranged at an oblique angle of lesser than <NUM>° with regard to the locking direction, i.e. to said movement of the locking element from the first to the second position. For example, said angle may be between <NUM>° and <NUM>°, in particular about <NUM>°.

In another advantageous further development, additionally or alternatively to the one explained before, the second recess can comprise a front inner sidewall configured to push the latch backwards during the movement from the second to the first position, more specifically at the beginning of said movement. Thus, when the locking element is pulled to move from the second to the first position, the detention surface of the latch is pushed against the front inner sidewall of the second recess that deflects the acting force towards the locking element, resulting, thanks to the resilience of the arm, in an evasive action of the latch. The latch, with continued movement of the locking element out of the cavity, slides along the front inner sidewall that pushes the latch increasingly backwards to a core portion of the locking element thereby bending the arm. Consequently, the latch moves more and more out of the second recess. Thus, the front inner sidewall of the second recess enables to move the locking element from the second to the first position when pulled out of the cavity by means of the tool. Preferably, said front inner sidewall is plain and arranged at an oblique angle of lesser than <NUM>° with regard to the unlocking direction, i.e. to said movement of the locking element from the second to the first position. For example, said angle may be between <NUM>° and <NUM>°, in particular about <NUM>°.

In the forgoing the expressions "front" and "rear" refer to the direction of movement of the locking element when it is moved from the first to the second position. In this direction, the object designated as "rear" is arranged behind the object designated as "front".

In a preferred embodiment, the locking element has a longitudinal shape comprising a central core portion at opposing sides of which are arranged the at least one bar and the latch. In other words, the central core portion is arranged between the projecting bar and the latch.

According to another aspect of the present invention, the underside of a central core portion of the locking element is arranged slidingly within a guiding track at the bottom of the cavity. In other words, said guiding track delimits the cavity, supports the locking element and contributes to keep it in position. Preferably, the guiding track is a shaped area of the terminal box that opens to the cavity. The central core portion can lay within the guiding track in a form fit manner. The central core portion can be that central core portion that is arranged between the projecting bar and the latch.

In order to easily push and pull the locking element it can comprise, at one axial end, a head formed by an end area of a central core portion and a left and right side wing protruding therefrom at opposing sides. By means of the side wings, the axial end of the central core portion is enlarged to form an operating surface big enough to act on comfortably with a thumb, for example. Of course, the central core portion could also have a cross-section along its entire axial length that corresponds at least to the size of said operating surface, but the embodiment according to the invention leads to a considerable material saving in the manufacture of the locking element. Moreover, the side wings allow applying the tool behind the head to act on a side wing's rear surface in order to pull the locking element out of the cavity. The central core portion can be that central core portion that is arranged slidingly within the guiding track and/ or that is arranged between the projecting bar and the latch.

Preferably, the cavity opens to an outer surface, especially to a front face of the terminal box via a window, wherein the locking element, in the first position, protrudes from said outer surface, and in the second position, a head of the locking element is situated within the window. Thus, in the first position, the locking element is easily accessible and can be pushed by hands into the cavity. Furthermore, in the second position, the locking element is safely stowed, i.e. there are no protruding parts on which you can hurt yourself. In addition, for safety reasons, it is not possible to unlock the arrangement by hand. The head of the locking element is preferably that one being formed by an end area of the central core portion and a left and right side wing protruding therefrom at opposing sides.

To ease application of the tool, the window can have an extension area at one side to insert a flat end of the tool into a space behind a side wing of the head. In other words, the window is bigger than the head. This enables to lever the locking element out of the cavity.

The invention further relates to a centrifugal pump having a pump electronics and an extension module that is plugged into the pump electronics and locked according to the invention.

As mentioned in the opening part, there may be at least a first extension module having a first housing size and at least a second extension module having a second housing size, wherein the second housing size is larger than the first housing size. More specifically, the surface area of the bottom of the housing of the first extension module is larger than the surface area of the bottom of the housing of the second extension module. Nevertheless, according to the invention, the kind of locking of this first and second extension module is identical in such a way that either the first or the second extension module can be plugged into the pump electronics and locked in the same manner by pushing the locking element or elements from the first position to the second position. In other words, the spatial arrangement of the locking elements in relation to the pillar or pillars is the same for the first and second extension module.

In a first example, the first extension module may have two pillars, whereas the second extension module may have four pillars. Preferably, the pillars can be symmetrically arranged with regard to the electric interface. In this case, on the side of the terminal box, there will be four openings to insert the pillars of both the first and second extension module. Furthermore, there will be two locking elements each having two protruding bars to lock either the first or the second extension module. However, as the first extension module has only has two pillars, the second protruding bar of each locking element is not acting. In a another example, the mounting mechanism is formed by four pillars at each of the first and second extension module and two locking elements at the side of the terminal box. The pillars can be arranged in or near the corners of the underside of the housing of the smaller first extension module, whereas in the case of the second extension module, due to its structurally larger housing, at least two of the locking elements are set back from the corners of the underside of this housing. As can be seen, although the housing of the first and second extension module may be different, they both fit to the mounting mechanism according to the present invention.

It is also an object of the invention to provide a set comprising at least a first and a second extension module of the aforementioned type wherein the surface area of the underside of the first extension module is larger than the surface area of the underside of the second extension module, but the electrical interface and the spatial arrangement of the locking elements with respect to the electrical interface are identical in the two extension modules.

Further objects, features, advantages, characteristics and effects of the invention will become more apparent from the following detailed description of embodiments of the present invention when considered in conjunction with the accompanying figures.

It should be noted that, in the context of the present description, the terms "have", "comprise", "comport" or "include" in no way exclude the presence of further features. Furthermore, the use of the indefinite article with an object does not exclude its plural.

<FIG> shows a front view of an arrangement <NUM> of a first plug-in electronic extension module <NUM> and a terminal box <NUM>, wherein the module <NUM> is mounted removable at the terminal box <NUM>. More specifically, <FIG> only shows a base plate <NUM> of said extension module <NUM> and the upper portion <NUM> of the terminal box that forms a base frame <NUM> for the mounting mechanism. A broken line indicates each of the housing of the module <NUM> and the terminal box <NUM>. The terminal box <NUM> is part of a centrifugal pump (not shown) and accommodates in its housing a pump control <NUM> for controlling the pump and the speed of its electric motor respectively. The electronic extension module <NUM> also accommodates in its housing an electronics <NUM> extending the pump control <NUM> by at least one additional hardware and/or software function. For example, the additional function provided is a wired bus or a Bluetooth interface. The arrangement <NUM> further comprises two locking elements <NUM> symmetrically arranged in the upper portion <NUM> of the terminal box <NUM> for securely holding the module <NUM> at the terminal box in a locked stated.

As will become more apparent from <FIG>, the extension module <NUM> has a pluggable electric interface <NUM>, 6a protruding from the underside <NUM> of the base plate <NUM> and extending through an opening <NUM>, <NUM> into the terminal box <NUM> to electrically connect the pump control <NUM> for establishing a data link. The electrical interface <NUM>, 6a comprises a socket <NUM> and electrical contacts 6a, indicated in <FIG>. The electrical contacts 6a protrude from the socket <NUM> and they are electrically plugged to corresponding electrical contacts at the side of the pump control <NUM>. The electrical contacts 6a are in the form of electrical tracks on a printed circuit board. The printed circuit board extends through a slot <NUM> in the base plate <NUM> into the socket <NUM>.

The module <NUM> comprises two consecutive pillars <NUM> on either side of the electric interface <NUM>, 6a extending in parallel to the electric interface <NUM>, 6a from the base plate <NUM>. In the top of the upper portion <NUM> there are four openings <NUM> corresponding to the arrangement of the pillars <NUM>, i.e. two consecutive openings <NUM> on either side of the opening <NUM>, <NUM> for the electric interface <NUM>, 6a. Each of the two consecutive openings <NUM> lead into one common cavity <NUM> so that there are two cavities <NUM>, one on either side of the opening <NUM>, <NUM> for the electric interface <NUM>, 6a. The pillars <NUM> are insertable through said openings <NUM> into the respective cavity <NUM> when the locking elements <NUM> are in a first position defining an unlocked state, as shown in <FIG>. The pillars <NUM> each have a notch <NUM> so that the pillars <NUM> have an overall hook shaped appearance. The notches <NUM> each open to the side. More specifically, the notches <NUM> of the right consecutive pillars <NUM> open to the right, and the notches <NUM> of the left consecutive pillars <NUM> open to the left. The function of the notches <NUM> is to engage with a bar of the respective locking element <NUM> in a form-fit manner when the locking elements <NUM> are in a second position, defining a locked state.

Each one of the locking elements <NUM> is slidably accommodated within the respective cavity <NUM>. The cavities <NUM> combine the two consecutive openings <NUM> with a window <NUM> in the front face <NUM> of the terminal box <NUM>. The locking elements <NUM> have been inserted into the respective cavity <NUM>, with an insert end <NUM> ahead, through the respective window <NUM>. The locking element <NUM>, in the first position, protrudes from said front face <NUM> so that it can be pushed tool-less, i.e. by hand, in particular by means of a thump, from the first position to the second position. In the second position, a head <NUM> forming an axial end of the locking element <NUM> is situated within the window <NUM> so that the locking element <NUM> can only be removed from said second position to said first position by means of a tool. This is done by inserting a flat end portion of the tool into a free space <NUM> behind the head <NUM> for levering the respective locking element <NUM> out of the cavity <NUM>. In order to facilitate the application of the tool, the window <NUM> is enlarged at the side of the free space <NUM> forming an extension area <NUM>, the sidewall <NUM> of which is inclined to direct the flat end of the tool directly into the free space <NUM> behind the head <NUM>.

As becomes more apparent from <FIG>, the socket <NUM> is hollow enclosing in its interior the slot <NUM> for the printed circuit board. The outer shape if the socket is trapezoidal in cross section to prevent an inadvertent or willful mismounting of the module <NUM>. At its basement, the socket <NUM> broadens to a pedestal <NUM> wearing at its outer circumference a gasket <NUM> comprising two parallel lips <NUM> as can be seen more clearly in <FIG>. In mounted state of the module, the pedestal <NUM> is accommodated within a trough <NUM> in the upper portion <NUM> of the terminal box <NUM> and sealed by the gasket <NUM>. <FIG> shows that, in the bottom <NUM> of the trough <NUM> there is an opening <NUM> leading into the interior of the terminal box <NUM>. The outer shape of said opening <NUM> corresponds to the shape and size of the socket <NUM> so as to form a form-fit connection of the "poka-yoke" principle.

Furthermore, base plate <NUM> comprises holes <NUM> for screws as alternative or additional mounting option for the extension module. Corresponding screw receptions <NUM> are provided in the top of the terminal box <NUM>.

Whereas in <FIG>, the pillars <NUM> are not specified any further, <FIG> differentiates between front pillars 20a and rear pillars 20b viewed from the front face <NUM> of terminal box <NUM>. The front pillars 20a are next to the electrical interface <NUM>, 6a and are substantially aligned with the socket <NUM> whereas the rear pillars 20b have a greater distance to the electric interface <NUM>, 6a. The rear pillars 20b are also aligned with each other.

<FIG> gives free view through openings <NUM> into the cavities <NUM>, as the locking elements <NUM> are in the first position, i.e. in unlocked state. The bottom area of the cavities <NUM> being aligned with the openings form a bottom closure <NUM> as depicted in <FIG>. Thus, the cavities <NUM> are completely closed to the interior of the terminal box <NUM>.

As can be seen from <FIG> and <FIG>, the arrangement <NUM> is symmetric with regard to the center of front face <NUM> of the terminal box <NUM>. In other words, the right side of the upper portion <NUM> of terminal box <NUM> is mirror symmetric to the left side. For that reason, only the left side is explained in more detail hereinafter.

<FIG> shows the locking element <NUM> in the second position, i.e. in locked state, so as it is completely housed within the cavity <NUM>. An enlarged view of functional areas <NUM>, <NUM>, <NUM>, <NUM> of the cavity <NUM> and the locking element are also given in <FIG>. In the following, the left locking element <NUM> and its cooperation with said functional areas <NUM>, <NUM> of the cavity <NUM> is explained hereinafter in conjunction with <FIG> giving a more detailed view of the locking element <NUM>.

The locking element <NUM> has, at a first side 11b (see <FIG>), a resilient latch <NUM> engaging with either a first recess <NUM> of the terminal box <NUM> keeping the locking element <NUM> in the first position, or a second recess <NUM> of the terminal box <NUM> keeping the locking element <NUM> in the second position. The first and second recess <NUM>, <NUM> form part of the cavity <NUM>. The latch <NUM> is arranged at the end of a resilient arm <NUM> so that the resilient arm <NUM> enables the latch <NUM> to be removed out of the first or second recess <NUM>,<NUM><NUM> by pushing the arm backwards during the movement of the locking element <NUM>. As can be seen from <FIG>, the other end of the arm <NUM> extends into a root portion <NUM> that is integrally formed with a central core portion 11a of the locking element <NUM>. The central core portion 11a extends along the completely axial length of the locking element <NUM> and forms its main part. There is a free space <NUM> between the arm <NUM> and the central core portion 11a enabling the resilient backwards movement of the latch <NUM> and the arm <NUM>, respectively, towards the core portion 11a.

The latch <NUM> has a leading forehead <NUM> or crown of rounded shape. The forehead <NUM> continues into a tangential surface <NUM> that progressively moves away from the arm <NUM> and then bends into a detention surface <NUM>, which in turn moves toward the arm <NUM>. Consequently, the overall outer shape of the latch <NUM> is a kind of a duck's head that acts like a hook. The detention surface <NUM> of the latch <NUM> interacts with a front inner sidewall <NUM> of the first recess <NUM> that is plain and perpendicular to the direction of movement of the locking element <NUM>, see <FIG>, to retain the latch <NUM> within the first recess <NUM>. Thus, said front inner sidewall <NUM> is an abutment and, in cooperation with the detention surface <NUM>, it limits the movement of the locking element <NUM> beyond the first position when it is moved from the second to the first position. In other words, the front inner sidewall <NUM> prevents the latch <NUM> being moved out of or falling out of the cavity <NUM>.

The first recess <NUM> also comprises a rear inner sidewall <NUM> that is configured to push the latch <NUM> backwards to the core portion 11a (into free space <NUM>) during the movement from the first to the second position, more specifically at the beginning of said movement. As depicted in <FIG>, said rear inner sidewall <NUM> is plain and arranged at an oblique angle of about <NUM>° with regard to the locking direction, i.e. to said movement of the locking element <NUM> from the first to the second position. Thus, when the locking element <NUM> is pushed from the first to the second position, the leading forehead <NUM> of the latch <NUM> is pushed against the rear inner sidewall <NUM> of the first recess <NUM> that deflects the acting force towards the central core portion <NUM> of locking element, resulting, thanks to the resilience of the arm <NUM>, in an evasive action of the latch <NUM>. It follows that, the latch <NUM>, with progressive movement of the locking element <NUM> into the cavity <NUM>, slides along the rear inner sidewall <NUM> that pushes the latch <NUM> increasingly backwards to the core portion 11a of the locking element <NUM> thereby bending the arm <NUM>. Consequently, the latch <NUM> moves more and more out of the first recess <NUM>.

In a corresponding manner, the second recess <NUM> that is situated behind the first recess viewed from the front face <NUM> of the terminal box <NUM> comprises a front inner sidewall <NUM> and a rear inner sidewall <NUM>. Said rear inner sidewall <NUM> has a shape that corresponds substantially to that for the leading rounded forehead <NUM> forming an end stop for the locking element <NUM>. Said front inner sidewall <NUM> is configured to push the latch <NUM> backwards during the movement from the second to the first position, more specifically at the beginning of said movement. As depicted in <FIG>, said front inner sidewall <NUM> is plain and arranged at an oblique angle of about <NUM>° with regard to the unlocking direction, i.e. to said movement of the locking element <NUM> from the second to the first position. Thus, when the locking element <NUM> is pulled to move from the second to the first position, the detention surface <NUM> of the latch <NUM> is pushed against the front inner sidewall <NUM> of the second recess <NUM> that deflects the acting force towards the central core portion 11a of the locking element <NUM>, resulting, thanks to the resilience of the arm <NUM>, in an evasive action of the latch <NUM>. It follows that, the latch <NUM>, with progressive movement of the locking element <NUM> out of the cavity <NUM>, slides along the front inner sidewall <NUM> that pushes the latch <NUM> increasingly backwards to the core portion 11a of the locking element <NUM> thereby bending the arm <NUM>. Consequently, the latch <NUM> moves more and more out of the second recess <NUM>.

In order to form the first and second recess <NUM>, <NUM> by means of injection moulding, core elements are used that leave residual holes <NUM> within the top of the terminal box <NUM>.

At a second side 11c (see <FIG>), that is, here, opposite to the first side 11b, the locking element <NUM> is configured as to give free way for mounting the module <NUM> in the first position, and arresting the module <NUM> in the second position. The latter is achieved by means of two protruding locking bars <NUM>, <NUM>, spaced apart from each other, one bar <NUM>, <NUM> for engaging with each one of the two consecutive pillars 20a, 20b.

As can be seen from <FIG>, the locking element <NUM> has an overall longitudinal shape. It comprises the central core portion 11a at opposing sides 11b, 11c of which are arranged the locking bars <NUM>, <NUM> and the latch <NUM> with arm <NUM>. In other words, the central core portion 11a is arranged between the protruding bars <NUM>, <NUM> and the latch, <NUM>. The cross section of the central core portion 11a is substantially rectangular. The bars <NUM>, <NUM> protrude from the central core portion 11a at opposing axial ends so as to form a front bar <NUM> and rear bar <NUM>, defining a free space <NUM> between them. In the first position, this free space <NUM> is aligned with the front opening <NUM> to leave the front pillar 20a pass. In the second position, the front bar <NUM> engages into the notch <NUM> of the front pillar 20a and the rear bar <NUM> engages into the notch <NUM> of the rear pillar 20b thereby arresting the pillars 20a, 20b form being removed.

In the combined top area of the front bar <NUM> and core portion, a first and second mark <NUM>, <NUM> is embossed. The first mark <NUM> is a direction indicator <NUM>, in this example in form of a triangle, indicating the direction of movement of the locking element <NUM> for locking the module <NUM>. The second mark <NUM> is a position indicator <NUM>, in this example in form of a bar, indicating the position of the locking element <NUM>. It helps to verify if the locking element <NUM> has correctly reached the first position for unplugging the module.

The underside <NUM> of the central core portion 11a of the locking element <NUM> forms a sliding surface. Said underside <NUM> is arranged slidingly within a guiding track <NUM> at the bottom of the cavity <NUM>, indicated in <FIG> and <FIG>. The guiding track <NUM> is a plan surface delimiting the cavity <NUM>, supporting the locking element <NUM> and contributing to keep it in position. The central core portion 11a lay within the guiding track <NUM> in a form-fit manner.

At the front axial end, the head <NUM> of the locking element <NUM> is formed by an end area of a central core portion 11a, a left side wing <NUM> and a right side wing <NUM>. The side wings <NUM>, <NUM> protrude from the central core portion 11a at opposing sides, thereby enlarging the axial face of the central core portion 11a to form an operating surface comfortable to act on with a thumb, for example. Between the left side wing <NUM> and the root portion <NUM> of the arm <NUM> there is the free space <NUM> in order to position the flat end of the tool behind the left side wing <NUM> and to act on its back surface <NUM> for levering the locking element <NUM> out of the cavity <NUM>. For that, the tool props at the inclined inner wall of the window extension area <NUM> whereas the flat end of the tool pulls the locking element off the cavity by exerting a pushing force against the back surface. Said back surface <NUM> is inclined in the locking direction so that the flat end of the tool can get in planar contact.

The back surface <NUM> of the right side wing <NUM> is parallel to the head's front face <NUM>. This back surface <NUM> contacts, in the second position, a right side rear wall <NUM>, as can be seen in <FIG>. In front of the right side rear wall <NUM> there is a space for accommodating the right side wing <NUM>.

At the side 11b of the central core portion 11a opposing rear bar <NUM> a guiding portion <NUM> protrudes from the central core portion 11a that guides the rear end of the locking element <NUM>. The underside <NUM> of said guiding portion <NUM> is stepped back in comparison with the underside <NUM> of the central core element 11a, so that solely said underside <NUM> of the central core element 11a is enclosed within the guiding track <NUM>.

As can be seen in <FIG>, the uttermost edge <NUM> of latch <NUM> is inclined in that the top surface extends beyond the bottom surface. Correspondingly, the inner wall <NUM> portion of the second recess <NUM> (see <FIG>) facing latch's inclined edge <NUM> is inclined as well, as can be seen in <FIG>.

<FIG> give a more detailed view on the mounting mechanism according to the present invention using axial and radial cross sections through the arrangement <NUM>, wherein <FIG> refer to the unlocked state and <FIG> refer to the locked state.

<FIG> designates a line J-J defining a horizontal cross section at a height Z crossing the pillars 20a, 20b below the notch <NUM>. The corresponding cross sectional view along line J-J is given in <FIG>.

In <FIG>, the rear part of cavity <NUM> is visible as the locking element is in the first position, partly extending into the cavity <NUM> and partly protruding from the front face <NUM> of the terminal box <NUM> the upper portion <NUM> of which is cut in <FIG>. Said upper portion forms a base frame. The cavity <NUM> is provided within that base frame. The latch <NUM> engages with the first recess <NUM>. In the rear part of cavity <NUM>, you can see the linear guiding track <NUM> as well as an elevated bottom area <NUM> of the cavity <NUM> supporting the guiding portion <NUM>.

<FIG> designates a line H-H defining a vertical cross section at a depth Y centrally crossing the front pillar 20a. The corresponding cross sectional view along line H-H is given in <FIG>.

In <FIG>, you can see the guiding track <NUM> bordering the central core portion 11a at its bottom and forming the lowest area of the cavity <NUM>. Next to the guiding track <NUM>, there is the elevated bottom area <NUM> that also supports the arm <NUM>. In the unlocked state shown in <FIG>, no physical component engages with the notch <NUM> as the free space <NUM> coincide with the notch <NUM> giving free view to the lateral face of the rear bar <NUM> that is located between the front pillar 20a and rear pillar 20b as indicated by broken lines in <FIG>.

<FIG>, showing the locked state of the arrangement <NUM>, designates.

The cross sectional view along first line A-A is given in <FIG>, along second line B-B is given in <FIG>, along third line C-C is given in <FIG> and along fourth line D-D is given in <FIG>.

As can be seen from <FIG>, in the second position of the locking element <NUM>, i.e. the locked state, the front bar <NUM> engages the notch <NUM> of the front pillar 20a. Simultaneously, as shown in <FIG>, the rear bar <NUM> engages the notch <NUM> of the rear pillar 20b. As can be seen in <FIG>, the cavity <NUM> comprises a side compartment for the locking bars <NUM>, <NUM>, that extends parallel to the central core portion 11a and that is aligned with the notches <NUM> in the pillars 20a, 20b. In <FIG>, the free space <NUM> coincide with said side compartment.

Besides, in <FIG>, you can see the latch <NUM> engaging with the second recess <NUM>. The bottom area <NUM> of the second recess <NUM> is lower than the elevated bottom area <NUM> of the cavity <NUM> supporting the guiding portion <NUM>, and is higher than the bottom area of the guiding track <NUM>. This has the advantage that small particles that may fall through the residual hole <NUM> of the second cavity are collected at the lower bottom area <NUM> and will not block the engagement of the latch <NUM> and the second recess <NUM>.

<FIG>, also showing the locked state of the arrangement <NUM>, designates.

The cross sectional view along first line E-E is given in <FIG>, along second line F-F is given in <FIG> and along third line G-G is given in <FIG>.

Considering <FIG> in conjunction, you can see that in the lower (<FIG>) and middle (<FIG>) area of the cavity there is no interaction between the locking element <NUM> and the pillars 20a, 20b. Interaction, however, is present in the upper area of the cavity <NUM> as can be seen from <FIG> where the locking bars <NUM>, <NUM> engages with the pillar's notches <NUM> so as to arrest the pillars 20a, 20b and to prevent the module <NUM> being removed from the terminal box <NUM>.

Simplified radial cross sections of the locking element <NUM> and surrounding base frame <NUM> are presented in <FIG> in order to explain the functions of the different outer surfaces or surface portions of the locking element <NUM>. <FIG> corresponds to the cut D-D in <FIG> whereas <FIG> shows a radial cut immediately behind the pillar 20b. The cross sectional outer shape of the locking element <NUM> is defined by the surface areas P, Q, R, S, T, U, V, Wand X that are rectangular or parallel to each other. In <FIG>, surface areas W-T-Q prevent a clockwise rotation of the locking element <NUM> as they are opposed to said direction. Surface areas P-S-V prevent an anti-clock wise rotation of the locking element <NUM> as they are opposed to said direction. Surface areas P-Q form a robust end-stop against module pulling action. In <FIG>, only surface areas T-Q are opposing a clockwise rotation of the locking element <NUM>, whereas surface area W forms a robust end stop in front of the lower section of the pillar 20b which is located below notch <NUM>. Furthermore, only surface area S is opposed to the anti-clockwise rotation of the locking element <NUM> as surface areas P and V have no function. Finally, only surface area Q forms a robust end-stop against module pulling action as surface area P is in front of nothing as it is directed to opening <NUM>.

In summary, the mounting mechanism according to the present invention is particularly characterized as follows:.

Claim 1:
Arrangement (<NUM>) comprising
- a terminal box (<NUM>) for a centrifugal pump accommodating a pump control,
- an electronic extension module (<NUM>) extending the pump control by at least one additional hardware and/or software function, and
- at least one locking element (<NUM>) for securely holding the module (<NUM>) at the terminal box (<NUM>)
the module (<NUM>) being removeably mountable at the terminal box (<NUM>) and having a pluggable electric interface (<NUM>, 6a) extending from the underside (<NUM>) of a base plate (<NUM>) through an opening (<NUM>, <NUM>) into the terminal box (<NUM>) to electrically connect the pump control (<NUM>) for establishing a data link,
characterized in that the locking element (<NUM>)
- is slidably accommodated within a cavity (<NUM>) of the terminal box (<NUM>) and can be moved tool-less from a first position to a second position and removed from said second position to said first position by means of a tool,
- having, at a first side (11b), a resilient latch (<NUM>) engaging with either a first recess (<NUM>) at the terminal box (<NUM>) keeping the locking element (<NUM>) in the first position, or a second recess (<NUM>) at the terminal box (<NUM>) keeping the locking element (<NUM>) in the second position,
- further being configured to give free way for plugging the module (<NUM>) in the first position, and to arrest the module (<NUM>) in the second position by means of at least one projecting bar (<NUM>, <NUM>) arranged at a second side (11c) of the locking element (<NUM>), and
the module (<NUM>) comprising at least one pillar (<NUM>, 20a, 20b) extending in parallel to the electric interface (<NUM>, 6a) from the base plate (<NUM>) and the pillar (<NUM>, 20a, 20b) being insertable through an opening (<NUM>) into the cavity (<NUM>), when the locking element (<NUM>) is in the first position, the pillar (<NUM>, 20a, 20b) having a notch (<NUM>) for engaging with the bar (<NUM>, <NUM>) in a form-fit manner, when the locking element (<NUM>) is in the second position.