Measuring device with additional display unit for overload detection

Abstract

Measuring instrument for measuring and displaying a physical quantity, comprising a rotatably mounted pointer shaft (14) and a pointer (8) attached thereto, a pointer drive by means of which the pointer shaft (14) can be rotated from an initial position depending on the value of the measured quantity, a driver (15) which is directly or indirectly attached to the pointer shaft (14) and participates in its rotation, and a movably arranged display element, wherein the driver (15) can come into contact with the display element when the pointer shaft (14) is rotated from its initial position and then carries or triggers the display element, wherein the display element is arranged such that it is activated before or upon reaching a pointer shaft position corresponding to a predetermined maximum value of the measured quantity.is carried along or triggered by the driver (15) and that, upon or after reaching this maximum pointer shaft position, it loses contact with the driver (15) and moves into an end position in which the indicator element is fixed, characterized in that a preloading device, which acts on the indicator element and exerts a spring-elastic force on it, moves the indicator element into its end position and holds it there.

Description

TECHNICAL AREA

[0001] The invention relates to a measuring instrument for measuring and displaying a physical quantity, such as pressure, and more precisely to a measuring instrument with at least one trailing pointer device which can be coupled to the axis of rotation of a pointer and which can, for example, assume two bistable states. STATE OF THE ART

[0002] Analog rotary indicators are familiar from numerous measuring instruments. These consist of simple, braked pointers that can be moved in one direction by the main indicator pointer via a stop and driver.

[0003] For example, it is important to reliably indicate when the permissible pressure of a container or hydraulic pump is exceeded, as this can happen briefly without being noticed in the absence of the operator or qualified personnel. This can, however, pose a risk to the continued operational safety of the system.

[0004] If such a limit has been exceeded and indicated, it may be expedient or necessary that this indication cannot be reset by individuals without further effort. Once overpressure has been reached, safety devices in a system often need to be checked or replaced, seals serviced, or any leaked material safely disposed of.

[0005] For this purpose, it is advantageous if exceeding a maximum permissible limit is clearly indicated and mechanically irreversibly displayed, or if resetting forces a shutdown or depressurization of the system. For example, US 1,732,338 A and US 877,314 A show and describe measuring devices where exceeding a predefined threshold can subsequently be permanently indicated.

[0006] Conventional drag indicators are unsuitable for this purpose. They are susceptible to manipulation or not vibration-resistant. If a reliable, permanent, and irreversible indication of an exceedance of a permissible value is required to warn people or operators of potential hazards, a display must be created that securely logs the exceedance of a critical limit.

[0007] The present invention is therefore based on the objective of providing a measuring device that irreversibly indicates, in a simple manner, an exceedance of a predetermined or permissible threshold / maximum value. This objective is achieved according to the invention by a measuring device with the features of claim 1. SUMMARY OF THE INVENTION

[0008] According to the invention, a measuring device used for measuring and evaluating a physical quantity comprises a measuring element for detecting the physical quantity, wherein the measuring element, for example a Bourdon tube or the like, moves in accordance with a change in the physical quantity, i.e., converts a change in the physical quantity into a detectable movement. Furthermore, the measuring device comprises a pointer mechanism that rotates a pointer in a pointer plane around a pointer axis in accordance with the movement of the measuring element, wherein the pointer is provided with a driver. The measuring device has a movable indicator element, wherein the driver can come into contact with the indicator element when the pointer shaft rotates from its initial position and then either moves or triggers the indicator element.The indicator element is arranged such that, before or upon reaching a pointer shaft position corresponding to a predetermined maximum value of the measured quantity, it is engaged or triggered by the driver, and upon or after reaching this maximum pointer shaft position, it loses contact with the driver and moves into a fixed end position. The measuring instrument further comprises a biasing device that acts on the indicator element and exerts a spring-like force upon it, moving the indicator element into its end position and holding it there.

[0009] A drag pointer is spring-loaded and rotatably mounted in a first recess and in a sleeve, and can lock into a second recess when actuated by the pointer.

[0010] The second recess is located below the first, thus ensuring that the driver of the main pointer can now move over this position of the second recess without having to actuate the sweep pointer again or remove it from its final position.

[0011] The measuring device according to the invention preferably further comprises a dial on which the pointer indicates the physical quantity based on a measured value. The sweep pointer mechanism is preferably mounted below the pointer axis to indicate when maximum values ​​are exceeded. However, it can also be mounted at various locations or on the outer circumference of the dial.

[0012] Further tasks, advantages and aspects arise from the dependent claims, the description of the exemplary embodiments and the drawings.

[0013] The invention is described in more detail below using an exemplary embodiment with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a drawing of a measuring instrument according to the invention as prior art. Fig. 2 is a front view according to the preferred embodiment; Fig. Figure 3 is a perspective view of the display element in its resting position; shortly before it is triggered by the pointer; Fig. Figure 4 is a perspective view of the triggered display element, or of the trailing pointer in the end position which was triggered by the pointer according to the preferred embodiment; Fig. Figure 5 is a perspective view of the display element in exploded view. DETAILED DESCRIPTION OF THE PRIORITY EXECUTION EXAMPLE

[0014] The view in Fig. Figure 1, a preferred embodiment of the measuring instrument according to the invention, shows, among other things, a measuring instrument housing 1. The main body 11 of the measuring instrument housing 1 has a pot-like shape.

[0015] Furthermore, a spring carrier 2 of a Bourdon tube 3 acting as a measuring element is shown, which, in its assembled state, is arranged in the cylindrical main body of the measuring instrument housing 1. The spring carrier 2 has a process connection 4 on its underside and a pointer mechanism 5 on its upper side. A connecting element 6 of the pointer mechanism 5 is directly connected to a free end 7 of the measuring element in its assembled state, and a pointer 8 of the pointer mechanism 5 indicates the measured value on a dial 9.

[0016] The measuring device is covered at the front by a seal 10, a viewing window 11, and is secured by a rotating bayonet ring 12. Such bayonet rings 12 are typically only removable on-site by hand with special tools and considerable force, as the high clamping force applied during closure can be applied mechanically, particularly during the manufacturing of the measuring device. The rear of the device is optionally equipped with a blow-out cover 13 and a seal, which opens to the rear in the event of a leak from the measuring element. However, the rear can also be permanently sealed.

[0017] The view in Fig. Figure 2, a preferred embodiment of the measuring device according to the invention, shows the measuring device from the front. The dial 9, mounted in the housing 1, has a recess in the center for the pointer shaft 14. The pointer 8, which carries a driver 15, is attached to this shaft. Below the pointer shaft 14, the auxiliary device for indicating overload is mounted. The indicator element consists of a pointer pin 16 and an auxiliary pointer 17 attached to it, which is rotatably mounted in a sleeve 18. Optionally, the auxiliary pointer 17 is printed with an inscription 19, which visually indicates the rest position and a triggered position 20 of the auxiliary pointer 17 by color.

[0018] The view in Fig. Figure 3, a preferred embodiment of the measuring device according to the invention, shows the auxiliary indicator in its rest position during normal operation. The pointer pivot 16, which is rotatably mounted in a sleeve 18, carries the auxiliary pointer 17, which lies in a stable rest position in the region of the scale's full scale value or in the region of a critical value of the pointer 8, either visibly on or optionally concealed behind the dial 9.

[0019] Upon reaching the critical value, the driver 15 comes into contact with the auxiliary pointer 17, takes it along during its further rotational movement, lifts it out of the shown rest position, and leads it further to the end position 22.

[0020] For documentation purposes, a sealing wax or a self-adhesive seal can be attached by gluing over pointer pin 16 and sleeve 18 in area 30.

[0021] The view in Fig. Figure 4, a preferred embodiment of the measuring device according to the invention, shows the auxiliary indicator, or auxiliary pointer 16, in its triggered end position. The spring 19 acting on the pointer pin 16 now holds it securely in this end position, which is lower than the rest position. The auxiliary pointer 17 is thus pivoted out of the effective range of the pointer 8 or its driver 15. However, the spring 19 is also suitable for holding the auxiliary pointer 17 under tension in its rest position. A single triggering of the auxiliary indicator 17 irreversibly indicates that a limit value has been exceeded. Any seals 30 are destroyed in the process. The device must be removed, replaced, or opened to reset the auxiliary indicator.

[0022] The view in Fig.Figure 5, a preferred embodiment of the measuring device according to the invention, shows the auxiliary indicator in a disassembled view. The pointer pin 16 receives the auxiliary pointer 17 in a bore. As already described, the auxiliary pointer 17 can assume either the rest position 21 or the end position 22 after activation, which are clearly shown again here.

[0023] It is conceivable that the parts shown are made of metal or plastic.

[0024] In the case of a plastic construction, the additional device can also be manufactured as a single piece, with the individual elements interacting via film hinges. Furthermore, the spring preload can be achieved using a leaf spring, or the entire function can be implemented similarly to a mousetrap, using a rocker arm.

[0025] The invention thus relates to a device for measuring and displaying a physical quantity, comprising a rotatably mounted pointer shaft 14 and a pointer 8 attached thereto, a pointer drive by means of which the pointer shaft 14 can be rotated from an initial position depending on the value of the measured quantity, a driver 15 which is attached directly or indirectly to the pointer shaft 14 and participates in its rotation, and a movably arranged display element, wherein the driver 15 can come into contact with the display element when the pointer shaft 14 is rotated from its initial position and then carries or triggers it.

[0026] This measuring instrument is characterized by the fact that the display element is arranged in such a way that, before reaching a pointer shaft position corresponding to a predetermined maximum value of the measured quantity, it is carried along or triggered by the driver 15, and that upon reaching this maximum pointer shaft position, it loses contact with the driver 15 and moves into an end position in which the display element is or becomes fixed.

[0027] It is preferably provided that the display element is irreversibly fixed in its end position.

[0028] Furthermore, the measuring instrument preferably comprises a dial 9 with a scale in front of which the pointer 8 is arranged, and can further be designed in such a way that the predetermined maximum value of the measured quantity is assigned to an upper scale limit value or a predetermined exceedance of the upper scale limit value.

[0029] The measuring instrument further comprises a preloading device which acts on the indicator element and exerts a spring-elastic force on it, which moves the indicator element into its end position and holds it therein, or is characterized in that the indicator element comprises a pointer pin 16 and an additional pointer 17 attached thereto, wherein the pointer pin 16 is rotatably mounted in a sleeve 18.

[0030] Optionally, the pointer pin 16 is arranged to be axially displaceable in the sleeve 18, the sleeve 18 having a detent recess into which the additional pointer 17 enters while simultaneously being displaced in the axial direction of the pointer pin 16 and is thereby fixed when the maximum pointer shaft position is reached.

[0031] The axis of rotation of the pointer pin 16 of the display device can run coaxially to the pointer shaft 14 or parallel to and at a distance from the axis of rotation of the pointer shaft 14.

[0032] In any case, the pointer pin 16 can also be arranged to be axially displaceable in the sleeve 18, wherein the sleeve 18 has a detent recess into which the additional pointer 17 enters while simultaneously being displaced in the axial direction of the pointer pin 16 and is accordingly fixed when the maximum pointer shaft position is reached.

[0033] This additional manometer device for displaying overpressure that is impermissible for the measuring system or the plant can be mounted either on the visible dial side, inside the housing, or in an additional, attached housing for the user / reader, and in either case concealed.

[0034] Apart from its use in a manometer, other applications for the previously described setup are conceivable. For example, the sweep pointer mechanism of the auxiliary pointer 17 used in the measuring instrument can be used in any other conceivable measuring device with an analog display. It suffices if a pointer element is equipped with a driver 15 in the broadest sense. Here, a small magnet on the pointer 8 or an element mounted behind the dial 9 can act magnetically on the auxiliary display, in the form of a sweep pointer mechanism as described above, acting as the driver 15.

[0035] The drag pointer device can also be evaluated electrically and displayed in a control room. For this purpose, the usual 4-20 mA or a digital protocol such as HART can be selected, with the triggering being detected via contacts, reed switches, or contactlessly using Hall effect sensors, GMR sensors, capacitive or inductive sensors.

[0036] The invention is not limited to the detailed embodiment described above. It can be modified to the extent specified in the following claims.

Claims

[1] Measuring instrument for measuring and displaying a physical quantity, comprising a rotatably mounted pointer shaft (14) and a pointer (8) attached thereto, a pointer drive by means of which the pointer shaft (14) can be rotated from an initial position depending on the value of the measured quantity, a driver (15) which is directly or indirectly attached to the pointer shaft (14) and participates in its rotation, and a movably arranged display element, wherein the driver (15) can come into contact with the display element when the pointer shaft (14) is rotated from its initial position and then carries or triggers the display element, wherein the display element is arranged such that it is activated before or upon reaching a pointer shaft position corresponding to a predetermined maximum value of the measured quantity,is carried along or triggered by the driver (15) and that, upon or after reaching this maximum pointer shaft position, it loses contact with the driver (15) and moves into an end position in which the indicator element is fixed, . characterized by , that a preload device which acts on the display element and exerts a spring-elastic force on it, moves the display element into its end position and holds it there. [2] Measuring device according to claim 1, characterized by , that the display element is irreversibly fixed in its final position. [3] Measuring device according to claim 1 or 2, characterized by a dial (9) with a scale in front of which the pointer (8) is arranged, and in that the specified maximum value of the measured quantity is assigned to an upper scale limit or a specified exceedance of the upper scale limit. [4] Measuring device according to any one of claims 1 to 3, characterized by, that the indicator element comprises a pointer pivot (16) and an additional pointer (17) attached thereto, wherein the pointer pivot (16) is rotatably mounted in a sleeve (18). [5] Measuring device according to claim 4, characterized by , that the pointer pin (16) is arranged to be axially displaceable in the sleeve (18), wherein the sleeve (18) has a detent recess into which the auxiliary pointer (17) enters while simultaneously being displaced in the axial direction of the pointer pin (16) and is thereby fixed when the maximum pointer shaft position is reached. [6] Measuring device according to claim 5, characterized by , that the axis of rotation of the pointer pivot (16) runs parallel to and at a distance from the axis of rotation of the pointer shaft (14). [7] Measuring device according to any one of claims 4 to 6, characterized by , that the driver (15) is attached to the pointer (8) and is intended to make contact with the auxiliary pointer (17). [8] Measuring instrument according to any one of claims 1 to 7, wherein the physical quantity to be measured is pressure or temperature. [9] Measuring device according to any one of claims 1 to 8, characterized by , that the pointer drive comprises a measuring element which can be acted upon with the physical quantity to be measured and which performs a movement depending on its value, as well as a pointer mechanism (5) which converts the movement of the measuring element into the rotation of the pointer shaft (14). [10] Measuring device according to any one of claims 1 to 9, characterized by , that the pointer drive including the pointer shaft (14), the pointer (8), the driver (15) and the display element are arranged together in a closed measuring instrument housing (1). [11] Measuring device according to claim 10, characterized by , that the display element cannot be manipulated from outside the measuring instrument housing (1). [12] Measuring device according to any one of claims 1 to 11, characterized by, that the display element is provided with sealing elements, which are preferably attached by gluing, and are destroyed when the display element is triggered.

Images