Current transmission device for a force measuring device, in particular for a weighing device

Abstract

To provide a current transmission device for a force measuring apparatus, in particular, for a metering apparatus, which can be used in an atmosphere having a risk of explosion, since the force measuring apparatus is configured as an explosion-proof system, and can be embodied in a simple and low-cost manner.SOLUTION: A coupling member (216) penetrates a housing wall (208) in an operational state in a contactless and arc-through prevention manner. The coupling member (216) is configured as a movable cable passage part, which directs a first cable (220) into the interior of a housing. A cable insertion part (206) fixed to the housing directs a second cable into the interior of the housing. An electric connection part having a low force shunt for both cables is provided inside the housing. A current transmission device (200) is configured so as to be assembled inside the housing (102) or outside the housing (102) of a force measuring apparatus (100).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a current transmission device for a force measuring device, in particular for a weighing device.

Background Art

[0002] When current or electrical energy is transmitted between relatively movable regions of a force measuring device, appropriate safety measures need to be taken when the force measuring device is used in an explosive atmosphere. Such a force measuring device can be, for example, a weighing device having a conveyor belt with an electric drive that acts as a preload on a weighing cell disposed within the housing of the weighing device. In that case, usually, not only an electrical supply line is provided that leads from a power supply unit provided in the housing of the weighing device, for example, or from a power supply unit disposed in the housing of the weighing device within a separate housing, to the electric drive of the conveyor belt, but also a communication line is provided that leads from a control unit provided in the housing of the weighing device to the electric drive of the conveyor belt.

[0003] For configuring a weighing device of this type in an explosion-proof manner, various methods are known. For example, the entire housing can be filled with a protective gas atmosphere. In the weighing device, since the load-receiving part or a member linked thereto must always be led out of the housing in a non-contact manner as much as possible, i.e., with a minimal force shunt, in the area of the insertion opening for the load-receiving part, a completely sealed seal, for example a bellows, must be provided with a minimal force shunt as much as possible between the load-bearing part, or a sufficiently small gap can be provided between the load-receiving part and the insertion opening and sealed by a labyrinth seal. In the case of a completely sealed seal, the housing may be (statically) filled with a protective gas atmosphere. If a gap remains between the load-receiving part and the insertion opening, in order to avoid the protective gas atmosphere becoming diluted to the extent that an explosive atmosphere occurs over time, the protective gas must be continuously supplied (dynamic protective gas atmosphere). Thereby, a minimal overpressure is generated in the housing to prevent an explosive atmosphere from being formed in the housing. In this case, normal indoor air can also be used instead of the protective gas, provided that it is guaranteed that this indoor air does not contain components that are at risk of explosion.

[0004] Such a metering device can be manufactured in an explosion-proof manner by having a pressure-resistant housing or a pressure-resistant capsule. The housing or the capsule must, in some cases, withstand the pressure of the explosive mixture that may occur inside the housing and prevent the explosion from spreading to the outside. At this time, when an explosion of the mixture occurs inside the housing, it is also necessary to avoid the components of the housing or the capsule flying out of the housing like bullets. Furthermore, when an explosion occurs inside the housing or the capsule, in order to avoid causing an explosion outside the housing when there is an explosive atmosphere dangerous outside the housing or the capsule, it must be ensured that no arcing to the surroundings occurs. For example, when the housing has an opening, for example, an insertion opening for a movable component, through such an opening, high-temperature particles generated by the explosion, which are sufficient to cause ignition of an explosive atmosphere that may exist in the external space, must not be configured to escape to the outside. Therefore, the outflowing gas must not exceed a certain maximum temperature. To ensure this, the opening, for example, the annular gap around the member inserted into the housing wall, can be dimensioned so as to provide a sufficiently small cross-section (the gas outflow direction extends perpendicular to this cross-section). Furthermore, the outflow opening must have a predetermined minimum length (when viewed in the outflow direction) so that the outflow temperature of the gas does not exceed a predetermined maximum value.

[0005] However, these measures for configuring the metering device in an explosion-proof manner require correspondingly high design costs, which increase the design size and weight of the device housing and are further associated with corresponding manufacturing costs. Providing a static or dynamic protective gas atmosphere, or supplying ambient air (where there is no explosion hazard) dynamically, also requires corresponding costs for gas supply and leads to high operating costs.

[0006] It is known to induce an electrical connection with substantially no force shunt between the stationary components inside the housing of such a weighing device and the electric drive part of the conveyor belt by passing corresponding conducting wires inside a load-bearing part inserted through the housing wall. An electrical wiring board having contacts connected to the conducting wires passing through the load-bearing part is provided in the lower end region of the load-bearing part inside the housing of the weighing device. Another wiring board configured to be stationary is provided inside the housing, which also has contacts, and these contacts are connected to corresponding supply conductors or control conductors coming from corresponding components inside or outside the housing. Both of these wiring boards have bridge contacts for each conducting wire, and two bridge contacts assigned to each other are connected via a sufficiently flexible electrical bridge usually configured to be short, in the form of a thin electrical conductor. These electrical conductors are usually not insulated, or in cases where they are not, they are insulated with a thin paint layer to ensure sufficient flexibility. In this way, sufficient mobility of the load-bearing part with respect to the stationary area of the appropriate measurement recording part is ensured while simultaneously under a minimal force shunt.

[0007] The measurement recording part may be, for example, a weighing sensor operating based on the principle of electrodynamic force compensation. In that case, only a very small or infinitesimally small deflection is required between the load-bearing part and the body. Accordingly, the electrical bridge may also be configured to be very small.

[0008] However, in such cases, in order to ensure explosion protection, it is necessary to configure the entire housing of the weighing device in an explosion-proof manner. This is because the signal transmission through the load-bearing part or the transmission of the electric drive output in the manner described above may cause arcs or terminal discharges that ignite the atmosphere with an explosion risk inside the housing in the event of a failure such as a short circuit, which may occur between the respective bridge conductors. However, this also involves corresponding costs.

Summary of the Invention

[0009] Based on such prior art, the object of the present invention is to provide a current transmission device for a force measuring device, in particular for a weighing device, which is configured in an explosion-proof manner and can thus be used in an atmosphere where there is a risk of explosion, and which can be embodied simply and at low cost. A further object of the present invention is to provide a force measuring device, in particular a weighing device, having a current transmission device of such a type.

[0010] In the following, the term "weighing device" refers to any device for detecting the force of weight.

[0011] The present invention solves these problems by the features of independent claims 1 to 15.

[0012] The finding on which the present invention is based is that it is not necessary for the entire housing to meet the explosion-proof requirements, but rather that the explosion-proof property for a force measuring device having a housing can be ensured only by arranging the current transmission device according to the present invention inside the housing of the force measuring device or only by connecting it externally to the housing of the force measuring device. Such a current transmission device serves for the wired transmission of electrical energy, in particular for the supply of energy to any component (for example an electric drive unit) and / or for wired communication (for example for the transmission of electrical signals).

[0013] At this time, the current transmission device according to the present invention has a pressure-resistant housing having a housing wall, and this housing can be mechanically and fixedly coupled to the base region of the force measuring device. The base region of the force measuring device may be, for example, the housing of the force measuring device. Further, the current transmission device has a coupling member at an outer end region protruding from the housing, which can be mechanically and fixedly coupled to the movable region of the force measuring device in the operating state. This may be, for example, the region of a load receiving part protruding from the housing of the force measuring device, or a component coupled thereto, for example, a load plate outside the housing. In the case of the weighing device example described above, having a housing and a conveyor belt outside the housing that acts as a preload on the force sensing part (for example, a weighing cell) arranged in the housing, the conveyor belt may be arranged on such a type of load plate.

[0014] The coupling member protruding from the housing of the current transmission device is configured to penetrate the housing wall in a non-contact and arc-proof manner in the operating state. Here, the concept of "arc-proof" means that the insertion of the coupling member through the housing wall is carried out so that the explosion protection property is guaranteed (taking into account the corresponding regulations and various grades of explosion protection in some cases).

[0015] At this time, the coupling member of the current transmission device is configured as a movable cable passage portion, and a first cable having at least one electrical conductor is passed through the coupling member in the outer end region (i.e., outside the housing of the current transmission device) and penetrates it. Inside the inner end region of the coupling member that penetrates into the housing, the cable is passed through the housing. In this way, the cable is passed through the housing within the coupling member, and the insertion of the cable into the coupling member must be configured at least in an arc-through prevention manner. For example, the cable may be passed through a notch in the coupling member and attached to this notch. Instead of attachment, by appropriate design measures, the cable may be clamped within this notch of the coupling member. Further, it is possible to expose the individual cores of the cable (hereinafter referred to as conductors) from the cable outer sheath within a certain axial range and adhere them to the notch of the coupling member. In this way, it is possible to prevent overpressure (in the case of an explosion) generated inside the housing from swelling the cable outer sheath outside the housing and possibly leading to an explosive rupture. In such a case, even the risk of arc-through can occur.

[0016] Of course, instead of a single cable, it is also possible to pass a plurality of cables each having a single conductor or a plurality of conductors (referred to as cables in this case) through the coupling member into the housing of the current transmission device.

[0017] At this time, the insertion of at least one cable into the coupling member must be pressure-resistant, which is to avoid the notch in the coupling member from cracking for the cable in the case where overpressure is generated by an explosion inside the housing. In such a case, ultimately, arc-through may occur, or a part of the cable or the component for cable insertion may come off and fly out.

[0018] Furthermore, the housing of the current transmission device has a housing-fixed cable insertion part configured to insert a second cable having at least one electrical conductor into the housing wall in a pressure-resistant and arc-tight manner. Also in this case, instead of a single cable, a plurality of cables each having a single conductor can be used. Regarding the insertion into the housing, the above description regarding the insertion into the coupling member applies mutatis mutandis.

[0019] A movable contact device mechanically and fixedly coupled thereto is provided in a second end region of the coupling member, and a housing-fixed contact device mechanically and fixedly coupled to the housing is provided inside the housing, and at least one flexible electrical contact bridge is formed between the movable contact device and the housing-fixed contact device.

[0020] At least one conductor of the first cable is coupled to the movable contact device both mechanically and electrically, and at least one conductor of the second cable is coupled to the stationary contact device both mechanically and electrically, such that electrical and mechanical contact is formed between at least one conductor of the first cable and at least one conductor of the second cable via at least one contact bridge.

[0021] This at least one flexible electrical contact bridge is manufactured such that the force shunt induced by the first and second cables between the base region and the movable region of a force measuring device having such a type of current transmission device generated thereby is less than a predetermined threshold value. This threshold value can of course be selected depending on the required measurement accuracy of the force measuring device. The electrical contact bridge may be configured, for example, as a thin flexible gold tape or from a number of individual thin wires.

[0022] In one embodiment of the present invention, the current transmission device is configured such that the coupling member is substantially cylindrical, the housing wall has a predetermined thickness in the region of the through-opening for the coupling member, the through-opening is configured to have a predetermined cross-section, and these are selected such that an arc-blocking annular gap is formed between the coupling member and the inner wall of the through-opening in the operating state.

[0023] The prerequisite for such an arc-blocking annular gap is that its cross-section (viewed in the direction of the long axis of the coupling member) and its length are determined such that even in the case of an explosion inside the housing, arcing into the space surrounding the housing is guaranteed not to occur, even if there is an atmosphere with an explosion hazard therein. At this time, the cross-section of the annular gap may vary along the long axis of the coupling member.

[0024] In another embodiment, the housing has a housing cover detachably coupled to the housing, and the housing cover is configured to cooperate with at least one stopper shoulder on the outer circumference of the coupling member with an engagement region extending into the housing, so that a limiting stopper for the movement of the coupling member is induced with respect to the movement of the coupling member in at least the outward movement direction from the housing.

[0025] For this purpose, the housing cover can have a flange that extends into and preferably circumscribes the housing to form the engagement region.

[0026] At least one stopper shoulder may be formed by a notch such as a groove on the outer circumference of the coupling member.

[0027] Such a limiting stopper prevents the coupling member from being ejected like a bullet from the accommodation opening in the case of an explosion inside the housing of the current transmission device.

[0028] In addition to such a stopper shoulder that restricts the movement out of the housing, another stopper shoulder may be provided to prevent the coupling member from moving too far into the housing. In this way, it is possible to avoid damage to at least one contact bridge, or even a movable contact device or a housing-fixed contact device.

[0029] For example, one groove on the outer circumference of the coupling member can embody both stopper shoulders simultaneously.

[0030] For easier assembly of the current transmission device, an annular mounting member may be provided that surrounds the coupling member and is configured to be slidable between an adjustment position and an operating position in the direction of the long axis of the coupling member thereon. Further for this purpose, the through-opening for the coupling member may be configured as an engagement region for the annular mounting member in a region facing outward with respect to the housing. At this time, the mounting member and the engagement region may be configured such that the coupling member is positioned in the housing such that an arc-preventing annular gap is formed between the coupling member and the inner wall of the through-opening, except for the engagement region, and can cooperate in this way under the mounting member in the adjustment position. In this adjustment position, the coupling member can be mechanically coupled to the movable region of the force measuring device and the housing of the current transmission device to the base region of the force measuring device, respectively. In this way, after the mounting member and the engagement region are disengaged, the movement of the coupling member (substantially only in the axial direction) becomes possible in the through-opening. That is, in this operating position, the mounting member releases the coupling member, that is, the coupling member penetrates the through-opening in a non-contact manner.

[0031] In this way, very easy assembly of the current transmission device can be performed on the surface or inside of the force measuring device, and high-precision adjustment of the coupling member with respect to the housing of the current transmission device can be guaranteed.

[0032] In one embodiment of the present invention, the mounting member may be configured to be lockable to the coupling member when in the operating position and / or the adjustment position. By being locked in the operating position, the mounting member can stay with the coupling member without preventing the free movement of the coupling member within the through-opening when in the operating state.

[0033] The mounting member, when in the operating position, may be configured to jointly form, in particular, a labyrinth seal that protects the annular gap against the ingress of water, dust, or other particles, i.e., to form part of the labyrinth seal.

[0034] In another embodiment of the present invention, the mounting member is surrounded by an annular member that is movable from the mounting position to the working position, and the annular member is offset and positioned in the direction towards the housing with respect to the mounting member when in the working position, and forms a labyrinth seal together with the mounting member and the housing.

[0035] The annular member can be locked to the mounting member and, accordingly, also to the coupling member even when in the working position. This working position may be selected such that the lower end face of the annular member, i.e., the end face of the annular member facing towards the outside of the housing, forms a stopper against the movement of the coupling member entering the housing.

[0036] Furthermore, the housing can preferably have a protruding flange surrounding the through-opening, which is surrounded by the annular member, for the co-formation of the labyrinth seal, and an annular gap is formed between the inner wall of the annular member and the outer wall of the flange. This annular gap can also form part of the labyrinth seal.

[0037] In another embodiment, the movable contact device and the housing-fixed contact device may each be configured as a wiring board. At least one flexible electrical contact bridge between the corresponding contacts of the wiring board may be configured as a flexible electrical conductor, in particular as a metal conductor, for example as a gold tape.

[0038] In order to simplify the assembly of the current transmission device according to the present invention, the wiring board forming the movable contact device and the wiring board forming the housing-fixed contact device may be mechanically coupled to each other when in the assembled state. For example, both coupled wiring boards can be coupled to the housing, or to the inner end of the coupling member, after insertion of the coupling member into the housing. At this time, the coupling member may be in a position where the assembly member engages with the inlet region of the housing at an adjustment position above the coupling member, whereby the coupling member is positioned relative to the housing such that the coupling member penetrates the housing in a non-contact manner. Subsequently, the connection between the two wiring boards can be released without the risk of damaging at least one contact bridge that is susceptible to influence.

[0039] At this time, each wiring board may be coupled, in particular, via a separation location, thereby enabling the integral production of each wiring board. The separation location is defined by a selected portion of the wiring board that is correspondingly thin or narrow.

[0040] Accordingly, the current transmission device according to the present invention provides a force measuring device having a simple and low-cost structure, in which an electrical conductor connection that generates only a very small force shunt between two relatively movable regions of the force measuring device is configured, for use in an atmosphere where there is a risk of explosion. At this time, the current transmission device according to the present invention is configured in a modular form and can also be used for relatively simple retrofitting or equipment modification to existing force measuring devices. Furthermore, the modular configuration enables use for various types of force measuring devices. At this time, the current transmission device according to the present invention can also accommodate other electrical components that are not intrinsically safe configurations that, without the current transmission device according to the present invention, would have to be arranged in the housing of the force measuring device (in such a case, if the current transmission device according to the present invention is not used, the entire housing of the force measuring device would have to be configured in an explosion-proof manner).

[0041] Other embodiments of the present invention will become apparent from the dependent claims. Next, the present invention will be described in detail with reference to the embodiments shown in the drawings, which should not be construed as limiting the basic central idea of the present invention described above. The following are shown in the drawings:

Brief Description of the Drawings

[0042]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0043] Figure 1 shows a perspective view of a force measuring device in the form of a weighing device 100 having a housing 102 with a bottom plate 104, a surrounding side wall 106, and an upper housing wall 108. A load plate 110 is mechanically coupled to three support members guided by the upper housing wall 108, and these support members penetrate the upper housing wall 108 in a non-contact manner. Corresponding break portions in the upper housing wall 108, or rather, the annular gaps formed by the inner wall of the break portion and the outer wall of the support member penetrating it, are each "sealed" by a labyrinth seal 112. In this case, sealing means that the annular gaps extending in a meandering shape in cross-section, formed by each labyrinth seal, prevent the intrusion of water, dust, and other particles. At this time, the insertion of the support member is kept non-contact and does not generate any force shunting.

[0044] In Figure 1, a bush device 114 is provided on the left side of the housing wall 106, through which electrical energy can be supplied to the weighing device 100, and through which a unidirectional or bidirectional communication connection can be established between the weighing device 100 and a higher unit, for example, between the weighing device 100 and an external control unit (not shown).

[0045] The housing 102 of the weighing device 100 is not manufactured in an explosion-proof manner. Nevertheless, the weighing device 100 as a whole should be configured to be operable in an atmosphere with an explosion hazard, taking into account the corresponding regulations.

[0046] Figure 2 shows the weighing device 100 of FIG. 1 without the surrounding side wall of the housing 102. As is apparent from this drawing, inside this housing 102, a force detection unit 116 is provided which operates on the principle of electromechanical force compensation in the illustrated embodiment. The force detection unit 116 has a body 118 which, on the one hand, includes a base portion 120 and, on the other hand, includes a load introduction region 122 coupled to the base portion 120 via a lever mechanism. The load introduction region 122 has a support plate 124 on its upper surface, and this support plate is further coupled to the support member described above which is inserted into the upper housing wall 108 of the housing 102 in a non-contact manner. The support plate 124 may be screwed to the load introduction region 122, for example.

[0047] In this way, the force detection unit 116 can detect the force of the weight acting on the load plate 110. The load plate 110 can be coupled to another device, for example a conveying device (not shown), for example an electrically driven conveyor belt, to apply a load. At this time, electrical energy must be supplied to the electric drive unit of the conveyor belt. In such a case, there is a need to establish a communication connection between the weighing device 100 or between the weighing device and another external unit connected to the weighing device via the bush device 114. For this purpose, usually a cable connection is used between the weighing device and another device fixedly coupled to it mechanically. Here, the concept of "cable connection" is used in the sense of a wired connection arbitrarily configured for the transmission of current (regardless of what purpose the current is used for). FIGS. 1 and 2 partially show a cable 126 of this type of cable connection, and only the portion of the cable 126 inserted into the upper housing wall 108 of the housing 102 of the weighing device 100 is shown.

[0048] Figure 2 shows a current transmission device 200 having a housing 202 disposed in the internal space of the housing 102. The housing 202 has a closing cover 204 provided on the front side wall, which is coupled to the housing 202 by a plurality of screws. The housing 202 has a cable insertion portion 206 fixed to the housing on its right side wall. In Figure 2, only the coupling part 208 coupled to the housing is shown without the cable that is inserted into the coupling part 208 and held therein. This cable passed through the housing 202 of the current transmission device 200 may be connected to, for example, the bushing device 114. By connecting the bushing device 114 in this way, a corresponding wire connection can be established from an external unit (not shown) to the current transmission device 200 and from here to a unit connected to the load plate 110, for example, a conveyor belt.

[0049] The current transmission device 200 connects a cable (not shown) passed through the housing 202 at its side wall via the cable insertion portion 206 fixed to the housing to the cable 126, so as to enable causing only a very small force shunt with respect to the relatively movable parts of the force sensing unit 116 (and accordingly the weighing device 100).

[0050] FIG. 3 shows a cross-sectional view of the current transmission device 200 in a vertical central plane (with respect to the drawing of FIG. 2). The first thing that becomes apparent from this drawing is that the housing 202 has a very thick wall that causes the pressure resistance of the housing. The coupling part 208 of the housing-fixed cable insertion part 206 is screwed into the right side wall of the housing. Naturally, this screw connection must also be configured in a pressure-resistant manner, which is to prevent the coupling part 208 from flying out of the housing 202 like a bullet in the event of an explosion inside the housing 202. The cable (not shown) inserted through the coupling part 208 must be coupled to the coupling part 208 at least in an arc-tight manner. As already explained above, this can be done by a clamping mechanism (not shown in detail) or by pasting or casting. Since the cable usually has a plurality of conductors bundled therein, in order to improve the connection between the cable and the coupling part 208, the material in the axially inner region of the coupling part 208 may be removed, whereby the individual conductors can be connected to the coupling part 208 individually, for example, by adhesion or casting.

[0051] In the internal space of the housing 202, there is further arranged a housing-fixed contact device 210, which may be screwed to the housing by, for example, two screws 212 (only the left screw 212 is shown in FIG. 2). The housing-fixed contact device 210 has a connection contact 210a that can be connected to the end of the conductor contained in the cable. This can be done by soldering or by any clamping mechanism.

[0052] A through-opening 214 is formed in the upper wall of the housing 202, and a coupling member 216 extends through it. The coupling member 216 is inserted into the through-opening 214 in a non-contact and arc-preventing manner at least when the coupling member 216 is in an operating state where it is coupled to the movable part of the metering device 100, particularly to the support plate 124 and accordingly to the load plate 110. For this purpose, the cross-section of the through-opening 214 is dimensioned such that an arc-preventing annular gap is formed between the inner wall of the through-opening 214 and the outer wall or outer circumference of the coupling member 216 in the operating state with respect to the cross-section of the coupling member 216 (in the region of the through-opening 214). Along with this, for the operating state, it is of course a prerequisite that the housing 202 and accordingly the coupling member 216 are positioned accurately enough with respect to the through-opening 214.

[0053] As is apparent from FIG. 3, the coupling member 216 may be configured in a cylindrical shape, particularly a circular cylindrical shape, at least in the region where the coupling member 216 passes through the through-opening 214. This results in a simple design structure. This is because the through-opening 214 can be produced as a bore.

[0054] The coupling member 216 has, in its upper region, a receiving region for another coupling part 208 that can have the same design structure as the coupling part 208 of the housing-fixed contact device 210. This results in a simple design structure. However, of course, this region of the coupling member 216 may be configured in any other suitable arbitrary manner. Even in such a case, the coupling part 208 is held in the coupling member 216 in a pressure-resistant manner.

[0055] The coupling member 216 is configured as a cable passage as a whole, and for this purpose, it has a notch 218 that extends through the entire length of the coupling member 216. The upper region of the notch 218 is configured to have an internal thread that cooperates with the external thread of the coupling part 208 for receiving the coupling part 208.

[0056] The coupling component 208 screwed into the upper region of the coupling member 216 houses the cable 220 of the cable connection 126 (FIG. 2) and passes it through the notch 218 at least in an arc-preventing manner. Naturally, the cable 220 can also have a plurality of conducting wires, and these can also be individually fixed within the coupling component 208 as described above.

[0057] The cable 220 or the corresponding conducting wire is passed through the notch 218 and, with its inner end, penetrates into the internal space of the housing 202. The inner region of the coupling member 216 also penetrates into the internal space of the housing 202, whereby, as is apparent from FIG. 3, a movable contact device 222 can be attached to the inner end of the coupling component 208. This attachment can also be carried out using the same screw 224.

[0058] The movable contact device 222 also has a connection contact 222a that is coupled to the end of at least one conducting wire (not shown) included in the cable 220. This coupling can also be carried out, for example, by soldering or by means of a suitable clamping mechanism. In this way, the movable contact device 222 is movable together with the coupling member 216 and can perform a relative movement with respect to the housing 202. At this time, the movement path is determined depending on the configuration of the force detection unit 116. However, in the case of a force detection unit based on the principle of electrodynamic force compensation, at most an infinitesimally small movement path may be performed. This measurement principle relies on keeping the load-bearing part at a pre-defined position as much as possible, because the current required for this serves as a measure representing the force of the weight to be detected.

[0059] The connection contact 210a of the housing-fixed contact device 210 and the contact contact 222a of the movable contact device 222 are connected via a contact bridge 226, and the contact bridge 226 connects the contact contact 210a to the attached contact contact 222a respectively. Accordingly, the conducting wire of the cable passed through the housing 202 by the cable insertion part 206 is connected to the attached conducting wire of the cable passed through the housing 202 by the coupling member 216. The contact bridge 226 is made of a very flexible electrical conductor, such as a gold wire or a gold tape, in order to reduce the force shunt as much as possible. The contact bridge may be connected to the contact contacts 222a to 210a by bonding, soldering, etc. If the contact bridge 226 is to be configured to pass a relatively high current intensity, two or more wires may be connected to the corresponding connection contacts respectively.

[0060] The contact devices 210 and 222 may be configured as wiring boards as shown in FIG. 3, and the connection contacts 210a to 222a may be configured in the form of corresponding strip conductors or strip conductor regions. The connection contacts 210a and 222a can each have a head region and a terminal region that may be connected via one or more strip conductor paths. Accordingly, the region where each end of the contact bridge is connected to the connection contact can be located at a location different from the region of the connection contact that is connected to the corresponding each end of the conducting wire passed through the cable.

[0061] In the embodiment shown in FIG. 3, the wiring boards of the contact devices 210 and 222 are still coupled to each other via the coupling web 228. This is because the wiring boards of the contact devices are manufactured as a single wiring board which, in this embodiment, has a first region forming the contact device 210 and a second region forming the contact device 222. Thereby, the assembly of the current transmission device 200 is simplified. For example, first, the still integral substrate forming the contact devices 210 and 222 can first be inserted into the housing 202 and attached with screws 212. Then, the end of the conductor of the cable passed through the housing by the cable insertion portion 206 can be connected to the connection contact 210a. Then, the coupling member 216 can be inserted into the through-opening 214 until the inner end of the coupling member 216 is positioned relative to the wiring board so that the wiring board can be coupled to the coupling member 216 with screws 224. In this state, the cable 220 does not have to be yet screwed onto the upper region of the coupling member 216 together with the coupling part 208. However, it may be applicable.

[0062] However, in this assembled state of the coupling member 216, it is not guaranteed that the coupling member 216 penetrates into the through-opening 214 in a non-contact manner. The corresponding annular gap has extremely small dimensions, and just the attachment of the coupling member 216 via the wiring board forming the contact devices 210 and 222 is not sufficient for such precise positioning.

[0063] For the purpose of such precise positioning, an annularly formed assembly member 230 is provided on the coupling member 216 which surrounds the coupling member and is slidable on the coupling member 216 in the axial direction (the direction of the long axis L of the coupling member). The assembly member 230 surrounds the coupling member 216 without clearance, but slidable in the axial direction, whereby the coupling member 216 passed through it is also accurately positioned at the corresponding position under the fixed assembly member 230.

[0064] As is apparent from FIG. 3, the housing 202 has an engagement region 232 in the region of the through-opening 214 in the upper housing wall portion, and this engagement region is configured to cooperate with the lower region of the mounting member 230 for the accurate positioning of the mounting member 230 and, accordingly, the coupling member 216. For this purpose, for example, the engagement region 232 can have a circumferential annular shoulder 234 having an inner wall extending in the vertical direction that cooperates with the vertical outer wall of the lower region of the mounting member 230. The outer wall in the lower region of the mounting member 230 and the inner wall of the annular shoulder 234 can be exactly coaxial with respect to the major axis L. At this time, the annular shoulder, or its (vertical) inner wall extending coaxially with respect to the major axis L, can be formed in a region of the housing wall that protrudes with respect to the surface of the upper housing wall and / or in a region of the housing wall that is offset inward with respect to this surface. In this way, by engaging the lower region of the mounting member 230 with the engagement region 232, accurate positioning of the coupling member 216 can be achieved.

[0065] Instead of the circumferential annular shoulder, it is of course also possible to provide members or regions that are only distributed regionally around the circumference of the mounting member 230, which cause accurate positioning of the coupling member 216 in a similar manner.

[0066] The mounting member 230 can be configured to be lockable to the coupling member 216, for example, by one or more socket head screws 236 that extend perpendicular to the major axis L in the direction of the coupling member 216 inwardly in the wall portion of the mounting member 230.

[0067] Accordingly, the assembly of the current transmission device 200 described above can be supplemented as follows: After the wiring boards forming the contact devices 210 and 222 are coupled to the coupling member 216, the assembly member 230 can be pushed downward into the engagement region 232 and locked in that position. Then, the coupling web 228 can be split and the closing cover 204 can be inserted and screwed to the housing 202. The pre-assembled current transmission device 200 can be stored, packaged, or assembled to the weighing device 100 in this way.

[0068] The current transmission device 200 may be provided at any suitable position inside the housing 102, for example, near the mounting point of the force detection unit to the bottom plate 104, near the load introduction region 122, or in the region of the rotation joint of the lever mechanism of the force detection unit 116.

[0069] In order to ensure an arc-proof annular gap between the coupling member 216 and the inner wall of the through-opening 214 against the ingress of particles, water, etc., the assembly member 230 can form a labyrinth seal 238 together with the engagement region 232. At this time, in particular, the lower end face of the assembly member 230 can act as a partition wall for the labyrinth seal 238.

[0070] As is apparent from FIG. 3, the assembly member 230 is surrounded by an annular member 240, which also contributes to the formation of the labyrinth seal 238. The annular member 240 has an inner cross-section that substantially corresponds to the outer cross-section of the assembly member 230, whereby the annular member 240 substantially encloses and seals the assembly member 230. The annular member can also be fixed onto the assembly member 230 by the socket head screw 236. To achieve axial positioning of the annular member 240 on the assembly member 230, the assembly member 230 can have two notches 242, into which the socket head screw 236 in the annular member 240 can engage. The first notch 242, which can be seen in FIG. 4, can serve to lock the annular member 240 onto the assembly member 230 when in the upwardly displaced state, enabling the assembly member 230 to engage the engagement region 232. As shown in FIG. 4, in the downwardly displaced state, the socket head screw 236 in the annular member 240 engages another notch in the assembly member 230, thereby locking the annular member onto the coupling member 216 in the downwardly displaced position. In this position, the labyrinth seal 238 is formed by the engagement region 232, the annular shoulder 234, the lower end face of the assembly member 230, and the annular member 240, as is apparent from FIG. 3.

[0071] In this working position displaced downward, the lower end face of the annular member 240 facing the upper housing wall can also act as a limiting stopper to limit the axial movement of the coupling member 216 into the housing 202.

[0072] Such a limitation of the sliding path of the coupling member 216 can also be caused by the closing cover 204 having a flange 204a that projects substantially horizontally into the housing interior, and this flange engaging a groove 244 of the coupling member provided on the circumference of the region extending into the housing interior. At this time, the horizontally extending surface of the groove 244 has an axial spacing selected such that the coupling member 216 can perform a sufficiently large axial sliding movement with respect to the thickness of the flange 204a.

[0073] For example, the attachment of the current transmission device 200 to the force measuring device in the form of the weighing device 100 can be carried out as described below:

[0074] As described above, the pre-assembled current transmission device 200, together with the mounting member 230 engaged in the engagement region 232 (in the state of the adjusted and optionally locked current transmission device 200), is coupled to the stationary region of the weighing device 100. For this purpose, the housing 202 can be coupled to the bottom plate 104 of the housing 102 of the weighing device 100. This can be done, for example, by screwing. In order to couple the load receiving part or load introduction region of the force detection part 116 and the coupling member 216, as is apparent from FIG. 2, the upper head region of the coupling member 216 configured substantially cylindrically can have two surfaces 246 extending parallel to each other in a suitable axial region. With this axial region, the head region of the coupling member 216 can be engaged with the slit of the fork-shaped region of the support plate 124. Then, a nut 248 is press-fitted onto the upper head region of the coupling member, and the coupling member 216 can be mechanically and fixedly coupled to the support plate 124. Next, the upper housing wall 108 of the housing 102 can be placed thereon, and at this time, the upper region of the coupling member 216 and the other three members extending upward from the support plate 124 penetrate the upper housing wall 108. Then, a labyrinth seal 112 can be produced not only in the region of the through portion of the upper region of the coupling member 216 passing through the upper housing wall 108 but also in the region of the other members, and the load plate 110 can be assembled. In the next step, another device such as a conveyor belt can be placed on the load plate and coupled thereto. The cable 220 can be connected to an electrical device of another device, for example, a drive part of the conveyor belt.

[0075] After such an assembly process, the assembled member 230 can be displaced to an upper position and locked there. Finally, the annular member 240 can be moved to a lower position and locked there. Finally, the cable drawn out from the housing 202 of the current transmission device 200 by the housing-fixed cable insertion portion 206 can be connected to the bush device 114. After attaching the housing side wall, the assembly process is completed.

[0076] It should be noted that, of course, one or more steps of the assembly process described above can also be executed in a different order. For example, the housing 102 may be configured as a folding housing, that is, the upper housing wall 108 and the side wall 106 are integrally formed.

[0077] The current transmission device 200 configured in this modular form can be retrofitted in a simple manner with only minor modification measures in an existing force measuring device, and in that way, the corresponding force measuring device can be configured to be explosion-proof or jointly cause explosion protection. Due to the modular structure, the same current transmission device 200 can also be applied to variously different types of force measuring devices.

[0078] Finally, it should be noted that in addition to the electrical connection with less force shunting described above, other electrical components or electronic components that are not intrinsically safe can also be arranged in the housing 202, whereby no critical components that may cause ignition of the atmosphere with the risk of explosion inside the housing 102 of the metering device 100 are accommodated in the housing 102 of the metering device 100.

[0079] The entire current transmission device 200 can also be arranged outside the housing of the force measuring device, for example, on the same bottom frame, or can be coupled to the housing of the force measuring device.

Description of Reference Numerals

[0080] 100 Metering device 102 Housing 104 Bottom Plate 106 Circumferential Side Wall 108 Upper Housing Wall 110 Load Plate 112 Labyrinth Seal 114 Bush Device 116 Force Detection Unit 118 Body 120 Base Portion 122 Load Introduction Region 124 Support Plate 126 Cable Connection 200 Current Transmission Device 202 Housing 204 Closing Cover 206 Cable Insertion Port 208 Coupling Component 210 Housing-Fixed Contact Device 210a Connection Contact 212 Screw 214 Through Opening 216 Coupling Member 218 Notch 220 Cable 222 Movable Contact Device 224 Screw 226 Contact Bridge 228 Coupling Web 230 Assembly Member 232 Engagement Region 234 Annular Shoulder 236 Socket Head Screw 238 Labyrinth Seal 240 Annular Member 242 Notch 244 Groove 246 Surface L Long Axis

Claims

1. A current transmission device for a force measuring device, the force measuring device (100) having a housing (102) and a base region and a movable region which are movable relative to each other, (a) a pressure-resistant housing (202) having a housing wall, the pressure-resistant housing (202) being mechanically and fixedly connectable to the base region of the force measuring device (100), and a connecting member (216) at an outer end region protruding from the housing (202) and being mechanically and fixedly connectable to the movable region of the force measuring device (100) when in an operating state, (b) the coupling member (216) is configured to penetrate the housing wall in a contactless and arc-proof manner when in an operative state; (c) the coupling member (216) is configured as a movable cable passage, and a first cable (220) having at least one electrical conductor is passed through the coupling member (216) at an outer end region thereof and through the coupling member (216) at an inner end region thereof into the housing (202); (d) the housing (202) has a cable passage (206) fixed to the housing and configured for passing a second cable having at least one electrical conductor through the housing wall in a pressure-tight and arc-tight manner; (e) a movable contact device (222) is provided in the inner end region of the coupling member (216) and is mechanically and fixedly coupled thereto, and a housing-fixed contact device (210) is provided in the housing (202) and is mechanically and fixedly coupled thereto, and at least one flexible electrical contact bridge (226) is formed between the movable contact device (222) and the housing-fixed contact device (210), (f) at least one conductor of the first cable is mechanically and electrically coupled to the movable contact device (222) and at least one conductor of the second cable is mechanically and electrically connected to the contact device (210), such that electrical contact is formed between at least one conductor of the first cable and at least one conductor of the second cable via at least one electrical contact bridge (226); (g) the current transmission device (200) is configured to be mountable within or outside the housing (102) of the force measuring device (100); Current transmission devices.

2. 2. The current transmission device according to claim 1, characterized in that the coupling member (216) is configured as a substantially cylindrical member, the housing wall has a predetermined thickness in the region of a through opening (214) for the coupling member (216), the through opening (214) having a predetermined cross-section, which are selected such that an arc-proof annular gap is formed between the coupling member (216) and an inner wall of the through opening (214) in an operating state.

3. 3. The current transmission device according to claim 1 or 2, characterized in that the housing (202) has a housing cover (204) removably connected thereto, the housing cover being configured with an engagement area (204a) extending into the housing interior to cooperate with at least one stop shoulder on the outer circumference of the coupling member (216), in such a way that a limit stop is created for the movement of the coupling member (216) at least in the direction of movement out of the housing (202).

4. The current transmission device of claim 3, wherein the housing cover (204) has a flange (204a) extending into the housing (202) forming an engagement area.

5. 4. The current transmission device of claim 3, wherein at least one of said stop shoulders is formed by a notch (218) in the outer circumference of said coupling member (216).

6. (a) the through opening (214) for the coupling member (216) is configured in an outwardly facing area with respect to the housing (202) as an engagement area (232) for an annular mounting member (230) which is configured to surround the coupling member (216) and be slidable thereon in the direction of the longitudinal axis (E) of the coupling member (216) between an adjustment position and an operating position, the mounting member (230) and the engagement area (232) being configured such that the coupling member (216) is positioned in the housing (202) in such a way that, with the exception of the engagement area (232), an annular arc-proof gap is formed between the coupling member (216) and the inner wall of the through opening (214), and so cooperate with the mounting member (230) in the adjustment position; 3. The current transmission device of claim 2, wherein: (b) said mounting member (230) releases said coupling member (216) when in an operative position.

7. 7. The current transmission device according to claim 6, characterized in that the mounting member (230) is configured to be lockable with the coupling member (216) when in an operating position and / or an adjustment position.

8. The current transmission device of claim 7, wherein the mounting members (230) are configured to cooperate to form a labyrinth seal (238) when in an operating position.

9. 9. The current transmission device of claim 8, wherein the mounting member (230) is surrounded by an annular member (240) that is movable from an assembly position to a working position, the annular member (240) being positioned offset relative to the mounting member (230) in a direction toward the housing (202) when in the working position to form a labyrinth seal (238) with the mounting member (230) and the housing (202).

10. 10. The current transmission device of claim 9, wherein the housing (202) has a protruding flange (234) surrounding the through opening (214) for co-forming the labyrinth seal, and an annular gap is formed between an inner wall of the annular member (240) and an outer wall of the flange (234).

11. 2. The current transmission device according to claim 1, wherein the movable contact device (222) and the housing-fixed contact device (210) are each configured as a circuit board.

12. 12. The current transmission device according to claim 11, characterized in that at least one said flexible electrical contact bridge (226) is configured as a flexible electrical conductor.

13. 13. The current transmission device according to claim 11 or 12, characterized in that the circuit board forming the movable contact device (222) and the circuit board forming the housing-fixed contact device (210) are mechanically coupled to each other when in an assembled state.

14. 14. The current transmission device of claim 13, wherein the wiring boards are coupled via a separation point (228), the separation point (228) being part of the wiring boards.

15. A force measuring apparatus comprising a current transmission device (200) according to claim 1.

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