The gas meter crank mechanism

Subject of the invention is a gas meter, particularly a bellows gas meter, crank mechanism making the temperature compensation possible. The mechanism transmits the drive from bellows to the gas meter counting device.

The PL 196156 patent specification presents a solution of gas meter with crank mechanism which includes the temperature compensation mechanism with a part rotating around the axis, at least one crank element connected with the rotating part in a rotation securing way, at least one inclining arm connected by articulated joint with the crank element, at least one coupling element connected with the inclining arm and also the temperature-dependent compensation element determining the inclining arm angular position. The temperature- dependent meter error curve may be optimised by appropriate radial and tangent (stroke and plane motion) gauge element adjustments, caused by the compensation element and determined by a specifically shaped groove .

Also known are other solutions transmitting the membrane movement through the crank element to the counting device. As a rule, in those cases the rotating connection arm, connected with the compensation element, moves radially to the rotating part axis causing change of the membrane stroke and therefore change of the unit calculation volume.

Such mechanisms are used for eliminating the gas temperature change impact on the counting element

volume reading. The impact is very significant as the gas temperature change by 3K corresponds to the volume change by about 1%. Such gas temperature changes occur when the meter is located outside the building. The meter operates then in different seasonal temperatures. Therefore, the crank mechanism adjusts the volume of gas passing through the meter to the outside temperature .

The aim of the invention is to obtain such a crank mechanism that will compensate the gas meter temperature dependence by adjustment of the crank element in accordance with the specific temperature relation.

The crank mechanism of a gas meter with temperature compensation, particularly a bellows gas meter as in the invention, includes a rotating part, whose axis is also an axis of rotation of a crank disc, and at least one crank element connected with the temperature- dependent compensation elements. Its characteristic feature is that the crank element is directly coupled with another compensation element and indirectly, through a slide, coupled with the first compensation element. The crank element is durably connected with the free end of the second compensation element. The second compensation element is durably connected with the slide. The crank mechanism has a slide which moves in a straight line guide in the crank disc. The slide has an articulated joint connection with the declining arm of the first compensation element and the first compensation element is non-rotationally fixed in the crank disc. The first compensation element has an

inclining arm with a limited displacement capability for temperatures lower than the basic temperature due to a stop element fixed in the crank disk. The first and second compensation elements are "U" -shaped thermal bimetals .

In the presented invention, the compensation elements allow to adjust the crank element radially. Radial displacement of the crank element changes the membrane stroke, which causes up or down shift of the error curve in relation to the zero line. A particularly beneficial feature is that the crank element is adjusted by two independent compensation elements - one of them, operating in accordance with its temperature characteristics, moves the crank element in the radial direction, the other supports the first element and moves the crank element slide, i.e. the crank element itself, in the radial direction.

It is an important feature of the invention that the crank element slide movement is strictly dependent on the compensation element deformation. The compensation element shape is such that it secures proper temperature-dependent deflection. The compensation element may be adjusted by moving it in relation to the crank element slide stop profiles. The used compensation element shape gives different deformations at the positive and negative temperatures, therefore a deformation stop is provided for temperatures lower than the base temperature, which limits the length of compensation element operation.

The subject of invention, in an implementation example, is shown in the drawing presenting a schematic diagram of the gas meter crank mechanism operation.

The invention crank mechanism has a rotating part H ₁ , with crank disc 2_ mounted on it . On the crank disc 2_, __ through intermediate elements, the crank element _3 is mounted, which in this case converts the gas meter membrane reciprocating motion, via levers, into rotary motion.

On the crank disc 2 _^ , which is mounted on the rotating part JL, the first compensation element 4_ is fastened, which in this case is a "U" -shaped thermal bimetal . The first compensation element <4 is on one side fastened to the sleeve ES fixed in a non-rotational manner in the crank disc .2, and the other end of the first compensation element 4 is a free inclining arm jϊ. The first compensation element 4_ is connected with slide 1_ by the inclining arm 6 _^ , which is placed between the stop profiles 8 _^ of slide 1_. Slide J7 is mounted in the guiding element 9_ of crank disc 2 _^ . The guiding element 9_ is parallel to the line connecting the axis of crank element J3 with the axis of rotating part JL. Besides, the second compensation element JLJD, also a ¹¹ U" -shaped thermal bimetal, is fastened to slide 1_. One end of the second compensation element JLJ) is durably fixed in slide 1_ by means of the collet JLJL, the other free end of the second compensation element JLO_ is a support for the crank element 3_.

It is an important feature of the proposed solution that the shape of the first compensation element 4 requires some motion limitations to be

introduced. This is due to disproportionate deflection of the inclining arm β_ of first compensation element 4 uniformly in the positive and negative direction of temperature impact on the thermal bimetal . On the crank disc 2^ tangently to the free inclining arm 6> of the first compensation element 4_, the stop part 12 is mounted, which effectively limits the motion of inclining arm 6_ of the first compensation element 4 in the direction of thermal bimetal deflection under the negative temperatures.

The gas meter compensation method consists in using a crank mechanism for compensation. The crank mechanism includes crank disc :2, rotating on the axis of rotation _1. The first compensation element 4_ is by one end fastened to the crank disc 2_ by means of sleeve _5. The other free end of the first compensation element 4_ is the inclining arm 6_, which is placed between two stop profiles J3 of slide 1_. Under the impact of temperature change, the inclining arm 6_ of the first compensation element 4_ deflects and pushes the slide 1_, which moves along the guiding element 9_ of crank disc 2 _^ . The declining arm 6_ deflects freely towards the axis of rotation _1, but it is limited in the opposite direction by the stop part \2_. The second compensation element IJ) is fastened by one end to slide 1_ by means of collet 1_1. At the free end of compensation element 10 the crank element 2_ is fastened. The second compensation element l_0 deflects under the temperature impact . The crank element 2_ moves together with the second compensation element IJD in accordance with its deflection characteristics. Summing it up, the crank

element 3 _^ moves and changes the distance from the axis of rotation 1_ due to deflection of the inclining arm 6 _^ of the first compensation element £, and also due to the second compensation element 10.