WO2014077571A1

WO2014077571A1 - Non-contact fuel level measurement device using change in capacitance

Info

Publication number: WO2014077571A1
Application number: PCT/KR2013/010269
Authority: WO
Inventors: 이우주; 이해정
Original assignee: 주식회사 루멘월드
Priority date: 2012-11-13
Filing date: 2013-11-13
Publication date: 2014-05-22
Also published as: KR101443262B1; KR20140062192A

Abstract

The present invention provides a device that measures the fuel level in a fuel container in a non-contact manner. According to the non-contact fuel level measurement device of the present invention, a variable capacitance unit has: a plurality of fixed plates that are formed of a non-ferrous metal, have the same area, and are fixed in a state in which the plurality of fixed plates are apart from each other at regular intervals; and a rotating plate of the same size that is formed of a non-ferrous metal and connected to a rotating shaft so as to be inserted between the plurality of fixed plates by means of the rotation of the rotating shaft. Capacitance is changed by a change in an area overlapped by the rotation of the rotating plate with respect to the fixed plates. A floating portion has: an arm that is connected to the rotating shaft; and a float that is connected to an end portion of the arm, floats on the fuel surface in the fuel container, and is moved according to the level of the fuel surface so as to rotate the rotating shaft. A measurement unit measures the fuel level based on a change in the capacitance in the variable capacitance unit.

Description

Non-contact fuel level measurement device using change of capacitance

The present invention relates to a non-contact fuel level measuring apparatus using a change in capacitance, and more particularly, capacitance according to an opposing area between a rotating plate and a fixed fixed plate rotated by a floating part whose position changes up and down according to the fuel level. It relates to a non-contact fuel level measurement device for calculating the fuel level using the amount of change of.

As a method of always detecting the amount of fuel charged or injected into the existing fuel container, the surface of the coil wound on bobbin is brought into contact with the contact plate connected to the float end to measure the change in the current value according to the change in the coil resistance. There is a method of measuring the amount of fuel by measuring the change in resistance value detected by sliding a contact terminal on a conductor of a ceramic resistance card made by printing a conductor and a resistance pattern on a new material ceramic surface.

However, efforts to reduce carbon dioxide and exhaust gas emissions during the combustion process of fuels, and the use of alternative fuels (vegetable bio, alcohol, LNG, etc.), which are concerned about the relative increase in fuel costs due to the depletion of fossil fuels, have increased the existing contact. Fuel gauges present many problems.

Accumulation of fuel contamination and contaminant inflow leads to unstable contact functions, resulting in poor measurement accuracy, resulting in consumer complaints. In addition, in the case of a hybrid vehicle where consumers inject poorly refined fuel, use alcohol, and use a mixture of bio oil (vegetable oil) and diesel oil, the fuel gauge core must be maintained for a long time in the fuel container to maintain performance. Unexpected chemical problems caused corrosion of parts and materials, resulting in a significant deterioration in durability and reliability, resulting in a rapid deterioration in quality.

Therefore, it is necessary to develop a fuel level detection device that improves durability and reliability to ensure long-term guarantee of fuel detector performance due to diversification of fuels and use of mixed fuels. As a sensing device that constantly detects and manages fuel amount of energy (such as ultra low temperature LNG) fuel, there is an increasing need for an apparatus for measuring fuel level in a non-contact manner.

The problem to be solved by the present invention, not only can measure the fuel level by using the same variable capacity unit, regardless of the shape and capacity of the fuel container, but also contact failure and component oxidation generated in the conventional contact fuel level measuring device. The present invention provides a non-contact fuel level measurement device using a change in capacitance, which can prevent malfunction in fuel level measurement due to corrosion or corrosion.

The non-contact fuel level measuring apparatus according to the present invention for solving the above problems, a plurality of fixed plates made of non-ferrous metal and having the same area and fixed at regular intervals, and made of non-ferrous metal and connected to the rotating shaft A variable capacity part having a rotary plate inserted into the spaced apart state between the plurality of fixed plates by the rotation of the rotary shaft, and the capacitance changing according to a change in the area overlapped by the rotation of the rotary plate relative to the fixed plate; A floating part having an arm connected to the rotary shaft and a float connected to an end of the arm and floating on a fuel surface inside the fuel container to move in accordance with the level of the fuel surface to rotate the rotary shaft; And a measuring section for calculating a fuel level based on the capacitance change in the variable capacitance section.

And according to the embodiment, the variable capacity portion may be disposed in the lower portion of the fuel container to be deposited on the fuel. And when the variable capacity portion is disposed in a state of being deposited in the fuel, the variable capacity portion preferably further comprises a fuel filter for filtering impurities contained in the fuel. By such a fuel filter, the fuel penetrating into the variable capacity part can solve the disadvantage caused by the foreign matter since the fuel is in the filtered state.

According to another embodiment of the present invention, the variable capacity portion is disposed above the fuel container so as not to be deposited on the fuel.

According to an embodiment of the measuring unit, the storage unit stores a capacity-level correspondence table corresponding to a fuel level value to a capacitance value, and based on the measured capacitance value and the capacity-level correspondence table. And a level calculator for calculating the fuel level in the fuel container.

According to another exemplary embodiment, the measuring unit may further include an adjustment switch that is pressed by the user when the fuel container is full of fuel or when the fuel container is empty, and the level calculator may control the fuel when the adjustment switch is pressed. The fuel level is calculated based on the capacitance value when is full or the fuel is empty.

According to another embodiment, the measurement unit, the inclination sensor for detecting whether the fuel container is inclined and the inclination, and when the fuel container is inclined, the detected inclination is an error between the actual fuel level and the calculated fuel level. It is configured to further include a tilt error correction unit to correct.

The measurement unit may further include a warning display unit which lights a warning lamp or outputs a warning sound when the calculated fuel level is equal to or less than a predetermined threshold value.

According to another embodiment of the present invention, the float is made of metal, and has a groove in which the arm is inserted and fixed around the body, wherein the arm exceeds half of the total diameter of the float. It fits in the groove and engages with the float.

According to the present invention having such a configuration, it can be seen that the fuel level of the fuel container is measured by a non-contact method, not by the way in which the parts for measuring the level of the fuel in the fuel container are in contact with each other. Therefore, it can be expected that the problems caused by oxidation or corrosion of the parts and problems caused by poor contact, such as in the conventional contact type can be expected.

In addition, the measuring apparatus according to the present invention may also expect the advantage of measuring the fuel level using the same variable capacity unit regardless of the shape, capacity, and type of the fuel container. That is, it can be said that the measuring device of the present invention also has an advantage that can be applied to any container or shape in any field.

1 is an exemplary view illustrating a non-contact fuel level measuring apparatus using a change in capacitance according to the present invention.

Figure 2 shows the structure of the variable capacity in the absence of fuel, (a) is a perspective view and (b) is a side view.

Figure 3 shows the structure of the variable capacity in the state of full fuel, (a) is a perspective view and (b) is a side view.

4 is a diagram illustrating a change in overlapping area of a metal plate according to fuel capacity.

5 is an exemplary view in which a variable capacity unit is installed on an upper portion of a fuel container.

6 is an exemplary view in which a variable capacity unit is installed under a fuel container.

7 is a block diagram showing the measurement unit in detail.

8 illustrates an instrument panel for a user.

9 is an exemplary view showing a configuration for connecting the float and the arm.

Hereinafter, the present invention will be described in detail with reference to the embodiments illustrated in the accompanying drawings.

1 is a view illustrating a non-contact fuel level measuring apparatus using a change in capacitance according to the present invention. As shown in FIG. 1, the non-contact fuel level measuring apparatus 100 using the change in capacitance according to the present invention includes a float part 120 floating on a fuel surface which is a fluid, and a position of the float part 120. The variable capacitance unit 110 causes a change in capacitance according to the change, and a measurement unit 130 that calculates a fuel level (fuel amount) based on the change in capacitance in the variable capacitance unit 110.

In the measuring device 100 of the present invention, the float part 120 is to move up and down in accordance with the change of the amount of fuel in the fuel container 150, and is floating on the fuel surface of the liquid fuel by buoyancy itself. Keep it. And the float portion 120, the position is changed according to the fuel change amount, which causes a change in the variable capacity portion (110). The float unit 120 maintains the state of floating on the fuel surface of the fuel and moves with the level of the fuel 121, and one end of the float 121 is connected to change the position of the flow 121 It is configured to include an arm 122 for transmitting to the variable capacitance section (110).

In addition, the variable capacitance unit 110 of the present invention plays a role of causing a change in capacitance according to the opposing areas of the fixed plate and the rotating plate. In addition, the fuel level in the fuel container 150 may be measured based on the change in capacitance generated by the variable capacitance unit 110. Such a structure of the variable capacitance unit 110 is illustrated in FIGS. 2 and 3.

As shown in FIG. 2 and FIG. 3, the variable capacity unit 110 is a fixed plate 111 that maintains a fixed state and a rotating plate that rotates in accordance with the movement of the float unit 120 with respect to the fixed plate 111. (112). The rotating plate 112 is supported by the rotating shaft 113 made of metal to be interlocked together.

The fixing plate 111 is made of a non-ferrous metal, each composed of a plurality of metal plates having the same area, each of which is arranged while maintaining a constant interval. The plurality of fixing plates 111 are electrically connected in parallel without being in contact with each other. The fixing plate 111 is maintained in a fixed state. For example, the fixing plate 111 is assembled in a fixed state to the casing C to maintain a fixed state. In the illustrated embodiment it can be seen that the fixing plate 111 has a substantially rectangular shape.

The rotating plate 112 is also made of a non-ferrous metal like the fixed plate, and is composed of a plurality of arc-shaped metal plates each having the same area. The rotary plates 112 are also arranged without contact between the fixed plates 111 while maintaining a constant interval, respectively. The rotating plate 112 is supported by a rotating shaft 113 made of metal and is electrically connected to each other. In the illustrated embodiment, it can be seen that the rotating plate 112 is configured in an arc shape having an angle of about 90 degrees. The above-mentioned fixing plate 111 and the rotating plate 112 is preferably made of a non-ferrous metal or a non-ferrous metal alloy containing at least one of aluminum, copper, and stainless to prevent oxidation.

The metal rotating shaft 113, which can be referred to as the rotation center of the rotating plate 112, is coupled to the arm 122. Therefore, when the level of the fuel amount in the fuel container 150 changes, the arm 112 also rotates around the rotation shaft 113 as the float portion 120 moves. As the arm rotates, the metal rotating shaft 113 rotates, so that the rotating plate 112 coupled with the metal rotating shaft 113 also rotates. That is, it can be seen that the rotating plate 112 rotates within a certain angle range in response to a change in the level of fuel in the fuel container 150.

The plurality of rotating plates 112 may be inserted between the plurality of fixing plates 111 according to the rotation of the rotating shaft 113. The plurality of fixing plates 111 and the plurality of rotating plates 112 are spaced apart from each other to be electrically insulated and are not designed to physically contact each other. Here, it can be said that the rotary plate 112 does not contact each other even when inserted between the fixed plate 111.

When the position change of the float 121 is transmitted to the rotating plate 112 through the arm 122 and the rotating shaft 113, the area facing between the fixed plate 111 and the rotating rotating plate 112 in a fixed state changes. Done. In this way, the capacitance changes as the opposed (overlapping) area between the fixed plate 111 and the rotating plate 112 changes. The fuel level in the fuel container 150 can be measured based on the change in the capacitance value.

FIG. 2 exemplarily shows a perspective view (a) and a cross-sectional view (b) of the variable capacity unit 110 in a state where fuel is empty in the fuel container 150. In other words, if there is no fuel in the fuel container 150, the float 121 is substantially positioned at the bottom dead center, and the arm 122 is almost in a vertical state as shown. In the state where there is little fuel in this way, as shown in FIG.2 (b), the area Se which the fixed plate 111 and the rotating plate 112 oppose (overlap) mutually becomes minimum.

3 illustrates a perspective view (a) and a cross-sectional view (b) of the variable capacity unit 110 when the fuel container 150 is full of fuel. That is, when the fuel is filled inside the fuel container 150, the float 121 will be located at a relatively top dead center, and thus the arm 122 will be in a state close to the horizontal. In the state where fuel is full in this way, the area (area overlapped) Sf which the stationary plate 111 and the rotating plate 112 oppose each other becomes maximum.

On the other hand, the value of capacitance varies depending on what dielectric is present between each metal plate constituting the fixed plate 111 and each metal plate constituting the rotating plate 112. For example, air is also a dielectric, and various fuels (eg, gasoline, diesel, LPG, LNG, biofuel, or alcohol) necessary for powering an engine are also dielectrics, so the value of the capacitance varies depending on the type and characteristics of each dielectric.

In addition, when the stationary plate 111 and the rotating plate 112 are locked in the fuel, when the opposite (overlapping) area of the fixed plate 111 and the rotating plate 112 facing each other is changed, the capacitance value is set to the opposite (overlapping) area. Depends. In this case, when the variable capacitance unit 110 is in the air instead of being locked in the fuel, the capacitance becomes different according to the overlapping area of the fixed plate 111 and the rotating plate 112 as described above.

The present invention uses this principle, and the opposite (overlapping) area of the fixed plate 111 and the rotating plate 112 of the variable capacity unit 110 changes according to the level change of the fuel amount, and eventually the capacitance is measured to measure the inside of the fuel container. Implement to measure the fuel level. According to the present invention, it can be seen that the fixed plate 111 and the rotating plate 112 is configured to be in a non-contact type while the rotating plate 112 is rotated and inserted between the fixed plate 111.

4 exemplarily shows a change in the opposed area of the metal plate according to the fuel capacity. In FIG. 4A, an opposing area Se between the two

metal plates

111 and 112 in a state where the fuel container 150 is empty is shown. In FIG. 4B, the fuel container 150 has about half the fuel. The opposing area S _1/2 between the two

metal plates

111 and 112 in the filled state is illustrated by way of example, and (c) both metal plates 111 and the fuel container 150 in the state where the fuel is full. The opposing area Sf between 112 is illustrated. As shown in (a) to (c) of FIG. 4, it can be seen that the overlapping area of the fixed plate 111 and the rotating plate 112 changes depending on the level of fuel.

5 and 6 are views illustrating an embodiment in which the mounting position of the variable capacitance part may be changed. 5 illustrates an embodiment in which the fixed plate 111 and the rotating plate 112 are mounted on the upper portion of the fuel container 150 so as not to be immersed in the fuel. That is, since the variable capacity unit 110 is disposed above the fuel container 150, the variable capacity unit 110 is not submerged in fuel.

6 illustrates an embodiment in which the fixed plate 111 and the rotating plate 112 are mounted to the lower portion of the fuel container 150 to be immersed in the fuel. In this embodiment, the variable capacity unit 110 is locked to the fuel by being disposed at the bottom of the fuel container 150, that is, the bottom of the fuel container 150.

When the fuel container 150 is easily contaminated by a material into which the fuel container 150 is introduced or a fuel containing impurities is injected into the fuel container 150, impurities are deposited between the metal plates forming the fixed plate 111 and the rotating plate 112. The capacitance can then be measured incorrectly. Therefore, when a fuel containing a large amount of impurities is used or the fuel container 150 may be easily contaminated, the variable capacity unit 110 may be disposed above the fuel container 150.

In the embodiment illustrated in FIG. 6, since the variable capacity unit 110 is immersed in fuel, it is preferable to add a fuel filter 180 for filtering impurities or precipitates. When the fuel filter 180 is installed in the variable capacitance unit 110 as described above, the fuel that penetrates between the two

metal plates

111 and 112 of the variable capacitance unit 110 passes through the fuel filter 180 and thus, The precipitate is removed.

Referring back to FIG. 1, the float unit 120 is a component that moves up and down according to a change in the amount of fuel charged or injected into the fuel container 150. The float 121 and the arm 122 ) Is as described above. When the float 121 is moved up and down according to the amount of fuel injected, the arm 113 having one end connected to the float 121 and the other end connected to the rotation shaft 113 rotates the rotation shaft 113. Naturally, the arm 113 and the rotation shaft 113 may be integrally formed.

In this way, since one end of the arm 122 is coupled to the float 121 and the other end of the arm 122 is coupled to the rotation shaft 113, the height of the float 121 changes as the amount of fuel changes, and accordingly the arm The rotating shaft 113 coupled with the arm 122 and the arm 122 are also rotated to change the opposing area between the metal plates constituting the rotating plate 112 and the fixed plate 111. 1, 5, and 6 show an embodiment of the arm 122 of the float portion 120, the shape of the fuel container 150 and the mounting position of the variable capacity portion 110, etc. In consideration of this, the arm 122 may be implemented as a metal rod having an intermediate portion bent at an angle.

In addition, the measurement unit 130 measures the capacitance in the variable capacitance unit 110 and serves to measure the fuel level in the fuel container 150 as the measured capacitance. 7 is a block diagram showing such a measuring unit in detail. As shown in FIG. 7, the measurement unit 130 includes a capacitance sensing unit 131 that senses capacitance. The measurement unit 130 may include at least one of a level calculator 132, a level display unit 133, a warning display unit 134, a storage unit 135, an adjustment switch 136, and an inclination error correction unit 137. It may further include.

The capacitance detecting unit 131 measures a capacitance value based on the signal generated by the variable capacitance unit 110. The level calculator 132 calculates a fuel level existing in the fuel container 150 based on the capacitance value measured by the capacitance sensing unit 131. The level calculator 132 calculates the fuel level existing in the fuel container 150 based on the capacitance value measured by the capacitance sensing unit 131 and the capacity-level correspondence table of the storage unit 135 described later. do.

In order to calculate the level, the storage unit 135 stores a capacity-level correspondence table in which fuel level values correspond to respective capacitance values. The capacity-level correspondence table may have different correspondences depending on the shape, capacity, and fuel type of the fuel container 150. Therefore, when the shape, capacity, and fuel type of the fuel container 150 are determined, an appropriate capacity-level response It is preferable to set the table in such a manner that the table is stored in the storage unit 135 in advance.

The level display unit 133 outputs the fuel level calculated by the level calculator 132 through various methods such as a screen or a lamp so that the user can see with the eyes. The level display unit 133 may display a state in which fuel is filled in the fuel container 150 in a digital format in a range of 0% to 100%, or in an analog format such as a scale display.

The warning display unit 134 outputs a warning message to the screen, outputs a warning sound, or lights a warning lamp when the fuel level calculated by the level calculator 132 is lower than a predetermined threshold. It is a reminder that it is time for replenishment. The limit value can be changed by setting, and this limit value is stored in the storage unit 135.

On the other hand, the adjustment switch 136 also changes the signal value generated in the variable capacity unit 110 due to the deterioration of the charged fuel or the mixing of impurities, and thus a deviation between the actual fuel level and the fuel level calculated by the level calculator 132. Switch to adjust if The adjustment switch 136 may also be used when it is recognized that there is a deviation between the capacity-level correspondence table value initially set for the fuel tank and the actual fuel injection amount.

As a method of adjusting the deviation between the actual fuel level and the fuel level calculated by the level calculator 132, when the fuel container 150 is full, the adjustment switch 136 is pressed to store the capacitance value at that time. 135). When it is recognized that the fuel is exhausted to the lowest point, the adjustment switch 136 may be pressed to store the capacitance value at that time in the storage unit 135.

Thus, when the adjustment switch is pressed at the time of fullness and / or the exhaustion of the lowest point, the level calculation unit 132 performs the capacitance when the fuel stored in the storage unit 136 is full and / or when the fuel is exhausted to the lowest point. The capacitance value can be used to adjust the variation in fuel level.

Meanwhile, the measurement unit 130 may further include an inclination error correction unit 137 that corrects an error between the amount of fuel actually contained in the fuel container 150 and the measured fuel level when the fuel container 150 is inclined. The inclination error correcting unit 137 includes a hardness sensor 138 for detecting the inclined neck and the inclination of the fuel container 150, and using the inclination detected by the inclination sensor 138 in the level calculator 132 Correct the calculated fuel level.

In the case of the conventional fuel-type touch sensing device using a ceramic resistance plate, there was a problem of designing and manufacturing a ceramic resistance plate according to the shape or capacity of the fuel container, but applying the characteristics of the variable capacity unit 110 as in the present invention. In this case, the same variable capacity unit 110 may be used regardless of the shape or capacity of the fuel container. However, it is only necessary to adjust the length or shape of the arm 122 holding the float 121 according to the height and capacity of the fuel container 150. In addition, when the

metal plates

111 and 112 of the variable capacity unit 110 are made by reducing the shape of the cross section of the fuel container 150 cut up and down as a method to further apply the characteristics of the variable capacity unit 110. The amount of fuel that changes according to the shape of the fuel container 150 can be measured more accurately.

8 is an exemplary view of an instrument panel for a user. As shown in FIG. 8, the user instrument panel of the non-contact fuel level measuring apparatus 100 according to the present invention is a warning display lamp by the

level display lamps

1331 and 1332 by the level display unit 133 and the warning display unit 134. 1341 and adjustment switch 1361. The fuel level may be displayed in the digital format in the range of 0% to 100% on the level display lamp 1331 (1331), or the fuel level may be displayed on the level display lamp 1332 in an analog format such as a scale display. In addition, when the fuel level is equal to or less than a predetermined threshold, the warning display lamp 1321 lights up. The user instrument panel is not limited to the embodiment of FIG. 8 and may be implemented in various ways.

9 is a diagram illustrating the actual configuration of the float and the arm. As shown, when the float 121 is fixed to the arm 122 in the present invention, a groove 1211 is formed in which the arm 122 can be inserted and fixed in a circle around the body of the float 121, The arm 122 is assembled into the groove 1211 of the float 121 so as to exceed 1/2 of the total diameter of the float 121.

When the fuel is stored at a very low temperature such as LNG, it is preferable to use a metal float such as SUS (Steel Use Stainless) because the float of rubber or plastic is broken and cannot be used. 9 shows a configuration for easily assembling the float 121 and the arm 122 made of metals.

In the above described the present invention with reference to the specific embodiment shown in the drawings, but this is only an example, those of ordinary skill in the art to which the present invention pertains various modifications and variations therefrom. Therefore, the protection scope of the present invention should be interpreted by the claims to be described later, and all the technical ideas within the equivalent and equivalent ranges should be construed as being included in the protection scope of the present invention.

The present invention having the configuration described above may be applied to a fuel container for storing fuel necessary for driving an engine, and is simply applied to any type of fuel container, thereby enabling a reliable fuel level measurement.

Claims

A plurality of fixed plates made of non-ferrous metal and having the same area and fixed at regular intervals, and a plurality of fixed plates made of non-ferrous metal and having the same area and connected to the rotating shaft so as to be spaced apart from the fixed plates between the plurality of fixed plates by the rotation of the rotating shaft. A variable capacitance part having a rotating plate which changes in capacitance according to a change in an area overlapped by rotation of the rotating plate relative to the fixed plate;

A floating part having an arm connected to the rotary shaft and a float connected to an end of the arm and floating on a fuel surface inside the fuel container to move in accordance with the level of the fuel surface to rotate the rotary shaft; And

And a measuring unit for calculating a fuel level based on a change in capacitance in the variable capacitance unit.
The method of claim 1, wherein the variable capacitance unit,

Non-contact fuel level measurement device using a change in capacitance, characterized in that disposed in the lower portion of the fuel container to be deposited on the fuel.
The method of claim 2, wherein the variable capacitance unit,

Further comprising a fuel filter for filtering impurities contained in the fuel,

The fuel penetrating into the variable capacitance portion is a fuel filtered by the fuel filter, non-contact fuel level measurement device using a change in capacitance.
The method of claim 1, wherein the variable capacitance unit,

Non-contact fuel level measurement device using a change in capacitance, characterized in that disposed on the fuel container so as not to be deposited on the fuel.
The method of claim 1, wherein the measuring unit,

A storage unit for storing a capacitance-level correspondence table corresponding to the fuel level values respectively to the capacitance values; And

And a level calculator for calculating a fuel level in the fuel container based on the measured capacitance value and the capacity-level correspondence table.
The method of claim 5, wherein the measuring unit,

Further comprising a control switch that is pressed by the user when the fuel container is full of fuel or when the fuel container is empty,

And the level calculation unit calculates a fuel level based on a capacitance value when the fuel is full or the fuel is empty when the adjustment switch is pressed. The non-contact fuel level measuring apparatus using the change in capacitance.
The method of claim 5, wherein the measuring unit,

An inclination sensor for detecting whether the fuel container is inclined and inclined; And

When the fuel container is inclined, non-contact fuel level measurement device using a change in capacitance, characterized in that it further comprises an inclination error correction unit for correcting the error between the detected fuel level and the actual fuel level. .
The method of claim 5, wherein the measuring unit,

And a warning display unit which lights a warning lamp or outputs a warning sound when the calculated fuel level is less than or equal to a predetermined threshold value.
The method of claim 1,

The float is made of metal, and has a groove in which the arm is inserted and fixed around the body,

And the arm is fitted into the groove to engage with the float so as to exceed half of the total aperture of the float.