CN1074729C - Pressure indicating device - Google Patents

Abstract

The present invention discloses a pressure indicating device (2), which is used for being fixed on a tyre air valve for example. The present invention is pressed on the wall of a permanent air-tight hollow cavity with specified pressure, and comprises an air-tight flexible thin film (7). Mechanical connecting rods (10, 12) move according to the fact that pressure of the tyre provided with the present invention is higher than or lower than that of the hollow cavity (8) and rotate a double color ball (14), and a displayed color provides a visual signal. The signal indicates whether the pressure of the tyre is higher than or lower than the specified pressure, and people can easily find out that the tyre leaks or air leaks.

Description

pressure indicating device

This invention relates to a pressure indicating device and in particular, but not exclusively, to a device for indicating the pressure of an automobile tire.

A wide variety of pressure indicating devices have been available for quite some time, most of which provide accurate measurement of pressure, especially of gases and liquids.

In some situations, precise measurement of pressure is not required, but a simple and clear indication of pressure changes is desired. For example detecting leaks in pressure vessels. In this case, it is more practical to provide a very intuitive "one-look" indication that a leak is occurring rather than an accurate digital measurement of the pressure in the vessel.

Such devices are known in the current art. For example, a device indicating whether the gas path is pressurized has a trade name of ROTOWINK (produced by ex Norgren Martonair Co., Ltd.). The device is suitable for being installed on the control board, and its inlet is connected with the gas circuit part, such as the pressure vessel such as the storage tank of the gas compressor. The device consists of an air impermeable flexible membrane stretched over the inlet. The membrane supports a spring-returnable piston.

A connecting rod and crank mechanism extending from the piston terminates at the head of the unit, away from the inlet, and the connecting rod is connected to the crank within a rotatable ball with opposite halves of a different color, such as red and green. The ball is housed under a mirror through which one side of the ball is clearly visible from outside the unit.

For example, due to the air pressure generated in the pressure chamber connected to the inlet of the device, a pressure difference is generated across the membrane, causing the membrane to bend towards the head of the device, which pushes the piston and connecting rod towards the head. This movement causes the crank to cause the ball to turn so that the other side of the ball is seen through the lens. The opposite side of the ball in contrasting color provides a clear visual signal that pressure has developed within the pressure chamber.

It is highly desirable for vehicle tires to be kept at optimum pressure for safety, fuel economy, comfort and to prolong the life of the tires. Therefore, it is best to check the tire pressure regularly. However, this chore is often overlooked, as lower than optimal tire pressures are only perceived when the tire looks dangerously flat and/or the ride is uncomfortable, e.g. Or a drop in pressure due to inaccurate measurements on the pump or compressed air supply when the tire pressure is already well below optimal pressure. Obviously, the use of the vehicle between the time the loss of air pressure begins and when it is detected will greatly reduce tire life and place the vehicle driver and passengers at some risk.

It can also be dangerous to drive such a car with one or more tires over-inflated rather than under-inflated, although this does not happen often.

Various tire pressure detection devices have been tried to provide in the past. US Patent Specification 4814745 describes a cap that fits over the tire valve after the tire is inflated and includes an alarm circuit that de-energizes when the tire is inflated to the proper pressure. But the cap must include its own power supply and other wiring components, which is overly complex, prone to damage and too expensive.

US patent specification 4819686 discloses a purely mechanical device comprising a membrane in a cavity. The membrane can deform, giving a visual indication of the state of pressure inside the tire. On one side of the membrane is the so-called reference cavity, which is inflated to the pressure inside the tire when the device is mounted on the tire valve core. The reference cavity is then sealed, while the other side of the membrane is subjected to the pressure inside the tire, so that if the pressure in the latter decreases, the membrane moves. The structure is rather complicated, and the cap provides no indication that the tire is inflated to the correct pressure. This device is only effective at representing the pressure drop over time. UK Patent Specification 2277802 discloses a similar device, but wherein only a hand-held device is used for tire pressure status indication, the device being adapted to be placed close to the valve core. It has the same disadvantages as above.

US-A-2689481 describes a tire pressure indicating device comprising a housing which is screwed onto the tire valve core and which comprises an inlet for pressurized air from the tire into a transparent wall cavity. The cavity includes an airtight bellows, the degree of compression of which changes its length, which in combination with markings on the outside of the cavity, provides an indication of tire pressure.

According to the present invention, there is provided a pressure indicating device comprising a housing having an inlet for pressurized air, a permanently airtight cavity containing the pressurized air, a flexible member between the inlet and the cavity, and A signaling device, the signal of which is related to the pressure difference between the inlet and the cavity, the pressure indicating device is characterized in that the flexible member is a flexible gas-impermeable membrane which is bent towards the pressurized cavity when the inlet pressure increases Stretching, and the means includes a connection between the membrane and the signaling means adapted to activate the signaling means to provide a signal representative of the inlet pressure relative to the pressure of the sealed cavity. The signaling device is preferably located within the sealed cavity.

If such a device is used as a tire pressure indicating device, when the device is mounted on the valve core in place of a conventional dust cap, the inlet can be fitted into sealing contact with the valve, and when the device is tightened further, the tire valve opens so that The pressure at the inlet is the same as the pressure inside the tire.

It is best to inflate the cavity to just below the optimum tire pressure for your particular vehicle (optimum tire pressure is taken from the pressure recommended by the vehicle manufacturer). Thus, when the device is connected to the valve and opens the valve, the pressure differential between the higher tire pressure and the lower cavity pressure causes the air impermeable flexible membrane to flex, stretching towards the pressurized cavity and activating the signaling device, to provide a signal representative of tire pressure relative to seal cavity pressure.

The film structure can be a flat disc or (which improves lifetime and film sensitivity) rolled film.

The signaling device preferably provides at least two visually distinguishable signals. This is most easily achieved with a mechanism such as mounted as a rotatable ball, one color on one side and a contrasting color that can still be judged on the other, any mechanism that provides such a signal can be substituted. Preferably, the signal is clearly visible over a wide viewing angle, such as a viewing angle of 110 degrees or more.

The means connecting the gas impermeable flexible membrane to the signaling means is preferably a simple mechanical linkage which transmits any movement of the membrane when the membrane activates the signaling means. Preferably, a spring return piston is mounted on the membrane with an elongated member hinged at the end to a crank connected to the rotating ball signaling means. In use, any bending or flattening of the membrane will cause the ball to turn one way or another.

According to a particularly advantageous feature of the invention, the membrane can have a weakened zone, which ruptures if the tire pressure exceeds the cavity pressure by a predetermined value. With this membrane, when the unit is fitted to an over-inflated tire, the indicator will momentarily indicate the proper tire pressure, then the membrane ruptures and everything is rendered useless.

The inlet of the device preferably has a threaded hole and at one end of the hole there is an axial projection positioned to press the center pin of a conventional tire valve and open it. In order to ensure a sealing contact between the valve and the device, and to prevent air from escaping from the inside of the tire, the inlet preferably contains an O-ring in place.

Therefore, the tire pressure indicating device of the present invention can be easily mounted on any conventional tire air valve, and displays a clear visual signal to indicate the air pressure state of the tire. It can be mass-produced cheaply. It is also a lightweight integral part and provides an indication of self-rupture.

The device of the present invention is now described by way of example only with reference to the accompanying drawings, in which:

Fig. 1 is a vertical cross-sectional schematic view through the pressure indicating device of the present invention, wherein the film is in a fully bent state,

Figure 2 is the arrangement of Figure 1 with the membrane in a position where the inlet has not been mounted on the tire valve.

Referring to FIG. 1 , a tire low pressure warning device 2 with a substantially cylindrical shell 9 is mounted on the vehicle tire valve by screwing on the valve housing 1 . A protrusion 6 at the end of the screw hole 4 in the device 2 housing has pressed the center pin 21 of the valve. The O-ring 5 ensures a sealing contact between the device and the valve housing 1 . Push pin 21, can make compressed air pass through oblique hole 3, enter the space between boss 6 and the airtight flexible film 7 that is sealed on shell 9 from tire.

The flexible membrane 7 is stretched over the inlet and is positioned with a flange 11 on the inner wall of the housing 9 . It has a weakened zone 18 which ruptures if the inlet pressure exceeds the cavity pressure by a predetermined value.

Inside the housing 9, the cavity 8 shown above the membrane 7 is pressurized and is completely permanently airtight when the device is manufactured. The cavity 8 has a piston 10 which is pushed against the membrane 7 by a compression spring 13 . The spring 13 bears against an annular bead 24 inside the housing 9 . Piston rod 12 extends upwards and is hinged to shaft 20 which does not pass right through the center of dichroic ball 14 . The ball 14 has on its outside two small pins which define the axis of rotation 22 and which are positioned in corresponding two formations in the housing 9 so that the ball 14 is mounted rotatable about the axis 22 inside the housing. Through the transparent mirror area 16 of the housing 9, the ball 14 is visible from the outside of the device. Half of the ball is represented by G and colored green, and the other half is represented by H and colored red. Rod 12 passes through the arc groove on the ball. The piston 10 has perforations 17 to ensure equal pressure on both sides of the piston.

The cavity 8 is hermetically sealed during manufacture. Its pressure is higher than atmospheric pressure. But slightly below the optimum pressure for the tire that will hold the unit. So, if the pressure of the tire is optimal, the higher pressure behind the membrane 7 causes the membrane to bend towards the position shown in FIG. 1 . If the device is screwed onto a tire valve, this membrane movement will raise the piston 10 and rod 12 to the position shown in FIG. This provides a clear visual signal that the tire pressure is well above the pressure of the cavity 8 , overcoming the force exerted by the spring 13 .

However, if the tire on which the device is installed has slow deflation, the tire pressure will decrease. As the tire pressure and seal cavity pressure equalize, the pressure drop behind the flexible membrane 7 will cause the membrane to flatten. If the pressures are approximately equal, the flexible membrane 7 flattens so that the piston 10 and the rod 12 fall under the action of the spring 13 to the position shown in FIG. 2 .

This downward movement rotates the ball 14 so that the red half R is visible from the transparent mirror 16, thus providing a clear visual signal that the tire pressure has decreased.

It will be appreciated that the balls may also be colored other colors in order to indicate intermediate states between the fully bent and fully flattened positions of the film.

Phenomena such as slow deflation of vehicle tires, especially modern "low profile" tires, which are usually not noticed until the tires are viewed alone, can be easily detected by the device of the present invention. The device can be easily manufactured to "switch" pressure ranges to accommodate the recommended tire pressure ranges for a wide range of vehicles. If required, two sets of these are available as standard, one for when the vehicle is unladen or only slightly loaded, and the other for loaded vehicles, where a slightly higher tire pressure is often recommended.

It should be noted that if the device of the present invention is damaged itself, such as a rupture of the membrane 7, this damage will be immediately indicated to the user; when the tire is inflated to the correct pressure, the device is installed on the tire valve core, and the cavity 8 pressure Rise to be equal to tire pressure, but because of spring 13 reason, mechanical link does not have action, thereby seems that tire is still underpressure as if. If the device is unscrewed, the failure of the ball to turn is immediately apparent.

Similarly, if the sealing ring 5 fails, or the housing near the sealing ring cracks due to over-tightening of the threads. Then the tire pressure drops and the indicator turns red.

If the seal of the cavity 8 fails, the large pressure difference will rupture the membrane 7 in the region 18, as the membrane bursts. The membrane can also rupture if the pressure at the inlet exceeds the pressure of the cavity 8 by a given limit value, for example the tire pressure is more than twice the pressure of the cavity 8 . If the tire on which the device is screwed is subjected to significant overpressure, the device will rupture thereby, so if the device is screwed onto the valve core, it gives the user a very clear indication that there has been a serious problem.

In an alternative to providing the weakened area 18, a loss of pressure in the cavity 8, or a large tire overpressure could cause the rod 12 to buckle and release something in the cavity, distorting the appearance of the window.

The above specific description of the preferred embodiments and the general description of the invention refer to the device in connection with the tyre, but the device is not limited to this use. It can therefore be used in similar situations where it is desirable to detect any pressure drop below a preset value, such as detecting the status of a charged fire extinguisher, detecting the bladder pressure of a hydraulic accumulator and detecting the integrity of a closed pipe. In the last application, such as in mechanical or civil engineering, the interior of a closed pipe is pressurized to a specified value and fitted with the device of the invention. If there is a crack in the pipe, such as the weld at one end of the pipe, the pressure inside the pipe will drop, which can be felt immediately by watching the device of the present invention mounted on it.

Claims (15)

1. A pressure indicating device, which comprises a housing (9), the housing has a pressure air inlet (3), a permanent airtight cavity (8) containing pressure air, a pressure between the inlet (3) and the cavity The flexible part (7) between the cavity (8), and a signal device (14), the signal of the signal device is related to the pressure difference between the inlet and the cavity, it is characterized in that: the flexible part is a flexible air-tight film (7 ), when the inlet (3) pressure increases, the membrane (7) is bent to stretch towards the pressurized cavity (8), and the device includes a connecting device (10) between the membrane (7) and the signal device (14) , 12, 20), which is suitable for activating the signaling device (14) to provide a signal representing the inlet pressure relative to the pressure of the sealed cavity. 2. Pressure display device according to claim 1, characterized in that the signaling device (14) is located in the cavity (8). 3. A pressure indicating device according to claim 1 or 2, characterized in that the inlet is adapted to open the tire valve (1, 21) and to form a sealing contact (5) with the valve. 4. A pressure indicating device according to claim 3, characterized in that the cavity is inflated to a pressure just below the optimum tire pressure for the particular vehicle and its loading condition. 5. A pressure indicating device according to any one of the preceding claims, characterized in that the inlet comprises a protruding head (6) adapted to press against the valve's valve when the device is mounted on the housing of the tire valve. center pin (21). 6. Pressure indicating device according to claim 5, characterized in that the inlet comprises a seal (5) adapted to seal the connection between the tire valve housing (1) and the device housing (9). 7. A pressure indicating device according to any one of claims 1 to 6, characterized in that the signaling means (14) is capable of providing at least two distinguishable signals. 8. A pressure indicating device according to claim 7, characterized in that the signaling means is mechanical. 9. Pressure indicating device according to claim 8, characterized in that the signaling means is a rotatably mounted ball (14) which has at least two color zones. 10. A pressure indicating device according to any one of claims 1 to 9, characterized in that the indicating means is a visual indicator whose indication status is observable from the outside of the device at a viewing angle of at least 110 degrees. 11. A pressure indicating device according to any one of claims 1 to 10, wherein the connecting means is a mechanical linkage. 12. The pressure indicating device according to claim 11, characterized in that the connection means comprises a piston (10), an elongated member (12) and a crank arrangement (20) in which the piston (10) is installed against the membrane ( 7), the crank device (20) is connected to the signaling device (14), and the elongated member (12) extends between the piston (10) and the crank device (20). 13. Pressure indicating device according to claim 12, characterized in that the piston (10) is biased towards the membrane by a spring (13). 14. Pressure indicating device according to one of the preceding claims, characterized in that the membrane (7) is designed as a safety diaphragm (18) or includes a safety diaphragm (18). 15. The pressure indicating device according to claim 14, characterized in that the safety diaphragm (18) is designed such that if the acting pressure on the side of the membrane (7) away from the cavity (8) exceeds twice the cavity pressure, rupture occurs.

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