Patent Application
20160358720
The subject matter of the invention relates to an explosion-proof cross-type limit switch.
Cross-type limit switches comprise a cruciform actuating lever that is actuated via stops arranged along an operating path. DE 1 112 182, for example, shows a limit switch comprising a multi-arm actuating lever that is connected to a lever shaft that, at the same time, acts as a switching shaft. Fastened to said shaft are switching cams that are brought into engagement with an appropriate number of switch contacts. Furthermore, arranged on this shaft is a detent disk that ensures that the limit switch engages in defined positions. Due to the lever shaft and the switching shaft being of the one-piece type, it is not possible to distinguish between a 0° and a 360° position of the actuating lever.
Other limit switches are shown in document WO 2012/065955 A1. Here the limit switch comprises a gear mechanism that is coupled with an input shaft, wherein the gear mechanism drive is coupled with a cam shaft. The limit switch comprises an additional angle-measuring device for measuring the angular position of the input shaft.
The aforementioned limit switches are suitable for use in non-explosive environments. In contrast, in explosive environments the components of a limit switch must comply with a certification guideline for explosion protection. Retrofitting a limit switch with an already certified housing with a gear mechanism may either be impossible because of space problems or necessitate a comprehensive new design.
DE 1 797 089 shows a gear drive comprising several pinions and wheels in a closed housing for running gears in precision engineering. Respectively one pinion and one wheel are coaxially combined in one unit, wherein the units of pinion and wheel are directly supported in cutouts of the housing, with the cutouts matching the form of the units. The gearwheels are supported without axles and shafts on their flat sides and tooth tips.
It is an object of the present invention is to provide a cross-type limit switch that can be derived from an already certified housing.
The cross-type limit switch according to the invention is explosion-proof. For example, the cross-type limit switch may comply with the explosion protection types “flame-proof encapsulation” (ex-d) and/or “increased safety” (ex-e). The cross-type limit switch according to the invention includes a housing. Preferably, the housing is explosion-proof, in which case the housing complies with the explosion protection type “increased safety” (ex-e) and/or “flame-proof encapsulation” (ex-d). The housing contains a gear mechanism that includes a gear mechanism cover plate, a gear mechanism base plate and at least one intermediate plate arranged between the gear mechanism cover plate and the gear mechanism base plate. The intermediate plate has at least one cutout in which a first gearwheel is arranged and a second cutout in which a second gearwheel is arranged. The first gearwheel has a first plug-through opening and the second gearwheel has a second plug-through opening. A shaft carries an actuating lever arranged outside the housing and is radially supported and axially rotatable in a first bearing arrangement connected to the housing. Preferably, the first bearing arrangement is a part that is separate from the gear mechanism. The shaft is arranged in the first plug-through opening and rotationally coupled to the first gearwheel (i.e. the shaft and the gearwheel are non-rotatably coupled one to another). The first gearwheel is radially and also axially supported via a shaft. Furthermore, a rotary switch is arranged in the housing, with the switch comprising a switch shaft that is rotatably supported in a second bearing arrangement and in the second plug-through opening. The switch shaft is rotationally coupled to the second gearwheel, supporting it in axial and radial directions.
As a result of the structural design of the gear mechanism consisting of plates, a stacked design of the gear mechanism is achieved, this being particularly space-saving and easy to manufacture. In addition, the first cutout can hold or position the first gearwheel and the second cutout can hold or position the second gearwheel during assembly to such an extent that no additional holders or positioning aids are necessary during assembly. However, the gear mechanism does not support the first gearwheel and the second gearwheel.
Preferably, the first gearwheel and/or the second gearwheel are arranged with play in the first and second cutouts. In that regard, this is to mean a radial play, wherein the radial direction refers to the direction of rotation of the shaft of the switch shaft. However, the term “play” does not refer to a bearing play but, rather, the term “play” refers to the radial distance or the mean radial distance of the gearwheel from the respective cutout. Preferably, the play is greater than the radial bearing play of the shaft and/or the switch shaft. In this manner, the first gearwheel and/or the second gearwheel preferably moves—without contacting the wheel surface with the cutout and, hence, in a frictionless manner. The torques necessary for actuating a mains-voltage-conducting of a control-voltage-conducting switch can be readily transmitted in a reliable and low-wear manner.
The play is preferably smaller than a bezel or rounding provided on the shaft end face, wherein the comparison relates to the radial extension of the bezel or rounding. In this manner, the positioning through the cutouts is accurate enough so that the shaft or switch shaft can be easily inserted into the first or second plug-through opening. The shaft and/or the switch shaft may have a central outside hexagonal section and have, on both ends of the shaft and/or the switch shaft, a cylindrical section each, such section also being described as a round section. Preferably, the round section is disposed to support the shaft and/or the switch shaft. A bezel may be provided at a transition from a cylindrical section to an outside hexagonal section.
The first cutout and/or the second cutout preferably have straight walls in passage direction, with such walls radially delimiting the first and the second cutout, respectively. The first and/or the second cutouts are preferably passage openings though the intermediate plate transversely with respect to the plane defining the intermediate plate. Preferably, each of the first and/or the second cutouts have walls extending parallel to the axis of rotation. That is particularly preferred if the walls extend parallel to the axis of rotation. For example, the cutouts may be produced by punching, water jet cutting or laser cutting. A more cost-effective flexible small-series manufacture is thereby possible.
The first and the second cutouts may be provided in an intermediate plate. Preferably, the first cutout and the second cutout come into lateral engagement with each other. The first cutout and/or the second cutout are preferably circular but they may also be polygonal or follow another regular or irregular form. In a preferred embodiment, the first cutout and the second cutout overlap and form a passage opening of a first circular part and a second circular part, wherein the first part has a smaller diameter than the second part.
Preferably, the first cutout encloses the first gearwheel and the second cutout encloses the second gearwheel. The term “comprise” is to mean that the respective cutout encloses the gearwheel by more than 180°. In a first embodiment in which the first cutout encloses the first gearwheel and the second cutout encloses the second gearwheel, with the cutouts being arranged in an intermediate plate, sections of the intermediate plate form projections or noses in the gearwheels between the cutouts. As a result of this, a respective cutout a gearwheel is held such that the gear mechanism can be easily assembled.
The gear mechanism cover plate, the gear mechanism base plate and/or the intermediate plate are preferably elements with one planar upper side and one planar underside. Such planar elements can be made of plate-shaped base material by straight cuts extending in the direction of the later passage opening. The gear mechanism cover plate, the gear mechanism base plate and/or the intermediate plate preferably have walls extending transversely with respect to the underside or upper side. Preferably, the walls are perpendicular to the upper side or underside. This allows the aforementioned efficient manufacturing processes.
In a preferred embodiment the first gearwheel and/or the second gearwheel has a planar upper side and a planar underside. The first gearwheel and/or the second gearwheel preferably have walls extending transversely with respect to the underside and/or the upper side. In this manner, the first gearwheel and/or the second gearwheel are particularly easy to manufacture.
In a preferred embodiment the first gearwheel meshes with the second gearwheel. In a particularly preferred embodiment the gear mechanism comprises a first gearwheel and exactly one second gearwheel. Preferably, the first gearwheel is smaller than the second gearwheel. In a preferred embodiment the conversion of the movement of the shaft into the movement of the switch shaft is accomplished with the aid of a gear reduction. In doing so, a rotary movement of the first gearwheel that is coupled with the actuating lever is converted into a rotary movement of the second gearwheel, with the latter wheel covering a smaller angle. The first gearwheel and the second gearwheel are preferably arranged in one plane. The first gearwheel and/or the second gearwheel have, particularly preferably, a single gearwheel plane, so that the gearwheel has teeth only on a circumference having one diameter. Such a gearwheel can be manufactured in a particularly simple manner, for example by vertical cuts transversely to a planar upper side or underside of a plate-shaped starting material.
In a particularly preferred embodiment the shaft is coupled with a detent arrangement. The detent arrangement comprises a detent arrangement base plate, a detent arrangement cover plate and at least one detent arrangement intermediate plate with a pocket. Arranged in the pocket is a star wheel, in which case the star wheel is arranged on the aforesaid shaft. On its circumferential surface the star wheel is in engagement with a spring catch that initially inhibits a rotation of the star wheel out of its rest position and then, after overcoming a switch point, promotes the continuous rotation into the next rest position. The low friction of the gear mechanism having the design specifically described herein makes it possible for the detent arrangement to specify—in a low-tolerance manner—the rest positions subject to the action of the spring catch. In doing so, a safe switching of the cross-type limit switch is ensured.
Like the gear mechanism, the detent arrangement is essentially a plate stack, as a result of which a simple, space-saving design and a simple manufacture are made possible. The gear mechanism and the detent arrangement may be stacked to form a package, wherein the gear mechanism cover plate is arranged under the detent arrangement base plate. As a result of the stacked design a particularly space-saving construction of the detent arrangement is accomplished.
Preferably, the star wheel is arranged with play in the pocket, said pocket being preferably a cutout in the detent arrangement intermediate plate. Preferably, this is a passage opening transverse with respect to the plane defining the detent arrangement intermediate plate. Preferably, the star wheel is arranged with play in the pocket, this meaning the radial distance or the mean radial distance of the star wheel in the detent arrangement intermediate plate with respect to the wall delimiting the pocket in radial direction. In this manner, the star wheel may remain centered during the assembly of the cam switch in any event in such a manner that the shaft can be plugged simply through the passage opening of the star wheel.
The first bearing arrangement has a side that faces the inside of the housing and has a side that faces the atmosphere outside the housing. The first bearing arrangement may have a flame-proof gap. The first bearing arrangement may have one or several sliding bearings or antifriction bearings. The first bearing arrangement preferably comprises a bearing bushing.
The switch shaft of the rotary switch is preferably a cam shaft that can be brought into engagement with a switch element array located in the housing. The switch elements may be explosion-proof units that, for example, may be configured so as to comply with the explosion protection type “increased safety” (ex-e). Each of the switch elements, for example, may also be configured so as to comply with the explosion protection type “flame-proof encapsulation” (ex-d) in combination with the protection type “increased safety” (ex-e).
The second bearing arrangement is preferably completely arranged within the housing. A part of the second bearing arrangement may consist, for example, of an intermediate plate of the gear mechanism or a detent arrangement intermediate plate. For example, the bearing bushing may be arranged in the intermediate plate and/or the detent arrangement intermediate plate.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.
While the invention is susceptible of various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention.
Referring now more particularly to
Inside the housing 12 there is an operating unit consisting of a gear mechanism 24 and a detent arrangement 26. The gear mechanism 24 and the detent arrangement 26 are composed of plate-shaped elements, as will be explained in greater detail in conjunction with
Within the housing 12 below the gear mechanism 24 there is arranged a switch element assembly 30. The switch element assembly 30 also is fastened by means of screws 32 to the gear mechanism 24.
Located inside the housing 12 there is a passage 34 for electrical conductors (not illustrated) that are electrically connected to the switch elements of the switch element assembly 30, as will be understood by a person skilled in the art.
The housing 12 may be configured to comply with the explosion protection types “flame-proof encapsulation” (ex-d) and/or “increased safety” (ex-e). In particular, referring to the flame-proof encapsulation, all joints may be flameproof, wherein the joints might represent a potential connection between the inside 36 of the housing and the atmosphere.
The second gearwheel 58 has an arcuate oblong hole 68 into which engages the detent pin 52. As a result of this arrangement, the second gearwheel 58 cannot turn beyond a certain angle. In addition, this specifies a reference position of the actuating lever 18, which position potentially being disposed for verifying the setting of the limit switch 10. Overall, this arrangement thus ensures a safe limit stop. The gear mechanism base plate 48, the gear mechanism cover plate 38 and the intermediate plate 42 are preferably made of plate-shaped base material.
The gear mechanism base plate 48, the gear mechanism cover plate 38 and the intermediate plate 42 are manufactured, for example, by laser cutting or water jet cutting with cuts that are only perpendicular with respect to a plane 74 defining the plate. It is also possible to use a standard plate material that already displays the desired thickness. Using the intermediate plate 42 as an example, the first cutout 44 has a first wall 70 and the second cutout 46 has a second wall 72, each being transverse to the plate plane 74.
The first gearwheel 54 has a planar upper side 76 and a planar underside 78 and a first circumferential surface 80 that consists of wall sections 82 extending perpendicular to the planar upper side 76 and the planar underside 78. The first plug-through opening 56 is a hexagonal socket with walls that are parallel to the planar upper side 76. A corresponding hexagonal section of the shaft 20 is arranged in the first plug-through opening 56 so that the shaft 20 and the first gearwheel 54 are non-rotatably coupled one to another. The first gearwheel 54 is manufactured by cuts perpendicular to the plane of the plate-shaped base material of the first gearwheel 54, for example produced by laser cutting or water jet cutting. Preferably, the first gearwheel 54 is manufactured only by cuts vertical to the plate plane 74.
The second gearwheel 58 is plate-shaped flat with a planar upper side 86 and a planar underside 88 and has a second circumferential surface 90 that consists of wall sections 92 extending parallel to the axis of rotation. The second plug-through opening 60 is also a hexagonal socket with walls that a parallel to the upper side 86 and the underside 88. A corresponding hexagonal section of the switch shaft 138 is arranged in the second plug-through opening 60, so that the second gearwheel 58 is non-rotatably coupled with the switch shaft 138. Also, the second gearwheel 58 is thus manufactured by cuts perpendicular to the plane of the plate-shaped base material of the second gearwheel 58, for example by laser cutting or water jet cutting. Preferably, the second gearwheel 58 is manufactured with cuts vertical to the plate plane 96.
Due to the round cutouts 102a-c, a pocket 112 is formed for a star wheel 114 that is arranged in the pocket 112. The star wheel 114 has a central star wheel plug-through opening 116 that is disposed for the accommodation of a shaft 20. The star wheel 114 has a planar upper side 118 and a planar underside 120.
The oblong cutouts 100a-c, together, form a space that is disposed for the accommodation of two spring catches 124. One spring catch 124 has a spring 126 that forces a detent block 128 into engagement with the star wheel 114 in order to engage the position of the actuating lever 18 in a specific position. The detent arrangement 26 may be made up of two or more detent arrangement intermediate plates 104, 108 in order to be able to use standard sheet metal, i.e., metal sheets having standard thicknesses, and to be able to use, at the same time, standard springs.
The plate-shaped elements such as, e.g., the gear mechanism cover plate 38, the gear mechanism base plate 48, the intermediate plate 42 as well as the detent arrangement base plate 98, the first detent arrangement intermediate plate 104, the second detent arrangement intermediate plate 108 and the detent arrangement cover plate 110 are preferably laser-cut along cutting lines extending perpendicularly to the respective planar upper sides and undersides.
The sliding bearing 156 displays a certain radial bearing play that is defined by the difference of half the inside diameter of the bearing opening 162 and half the outside diameter of the shaft 20. The first gearwheel 54 that is arranged on the shaft 20 is arranged in the first cutout 44 with play, in which case this refers to the radial distance of the first gearwheel 54 from the first cutout 44. Preferably, the first gearwheel 54 is still arranged flush in the first cutout 44 so that the first cutout 44 centers the first gearwheel 54 at least to such an extent that the insertion of the shaft 20 in the gear mechanism 34 is possible without additional centering means. The shaft 20 may have a bezel 166 at its shaft end face 164 (see partial view in
The star wheel 114 is also arranged with play in the round cutouts 102a-c. Preferably, the radial bearing play of the sliding bearing 156 is less than the play of the star wheel 114 in the round cutouts 102a-c.
The switch shaft 138 is arranged in a bearing in the first detent arrangement intermediate plate 104 provided in the first bearing opening 106. A second bearing point is formed by the second bearing opening 134 that is arranged in the holding bracket 136. Overall, the bearing in the first bearing opening 106 and the second bearing opening 134 forms a second bearing arrangement. The second bearing arrangement displays radial play. The second gearwheel 58 has a certain play in the second cutout 46. Preferably, the radial play of the switch shaft bearing is less than the play of the second gearwheel 58 in the second cutout 46. Preferably, the second gearwheel 58 is nevertheless arranged flush in the second cutout 46 so that the second cutout 46 centers the first gearwheel 54 at least to such an extent that the insertion of the shaft 20 in the gear mechanism 24 is possible without additional centering means. The switch shaft 138 can have a bezel on its shaft end face. Preferably, the play of the second gearwheel 58 in the first cutout 44 is less than the dimensions of the bezel (analogous to partial view A).
From the foregoing, it can be seen that a cross-type limit switch 10 is provided that has a housing 12 in which a gear mechanism 24 is arranged, which gear mechanism has a gear mechanism cover plate 38, a gear mechanism base plate 48 and at least one intermediate plate 42 arranged between the gear mechanism cover plate 38 and the gear mechanism base plate 48. The intermediate plate 42 has at least one first cutout 44 in which a first gearwheel 54 is arranged. The intermediate plate 42 also has at least one second cutout 46 in which a second gearwheel 58 is arranged. The first gearwheel 54 has a first plug-through opening 56 and the second gearwheel 58 has a second plug-through opening 60. A shaft 20 bears an actuating lever 18 arranged outside the housing 12 and is mounted rotatably in a first bearing arrangement 22 connected to the housing 12. The shaft 20 extends through the first plug-through opening 56 in order to couple in rotationally fixed fashion to the first gearwheel 54 and to mount said gearwheel radially. The cross-type limit switch 10 also has a rotary switch 30, which is arranged in the housing 12 and has a switch shaft 138, which is mounted rotatably in a second bearing arrangement 106, 34 and extends through the second plug-through opening 60 in order to couple in rotationally fixed fashion to the second gearwheel 58 and to mount said gearwheel radially.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102014102403.6 | Feb 2014 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/053926 | 2/25/2015 | WO | 00 |
