1. A buffering device, comprising:
a cylindrical casing comprising a base plate;
a shielding piece pivotally attached to the base plate; and
a piston module movably mounted in the cylindrical casing and capable of moving towards or moving away from the base plate;
wherein the shielding piece comprises a main piece, a pivot mounting flange extends from the main piece, and a pivot hole is surrounded pivot mounting flange; a pivot post extends through the pivot hole for pivotably mounting the shielding piece on the base plate; an air inlet and an air outlet are defined in the base plate; a diameter of the air inlet being greater than that of the air outlet; when the piston module is moving towards the base plate, pressure inside the cylindrical casing causes the shielding piece to rotate to a closed position, thereby blocking the air inlet; and when the piston module is moving away from the base plate, environmental pressure causes the shielding piece to rotate to an open position, thereby opening the air inlet.
2. The buffering device of claim 1, further comprising a pair of latching members, wherein two ends of the pivot post protrude from opposite sides of the pivot mounting flange and are latched by the pair of latching members.
3. The buffering device of claim 2, wherein each latching member has a U-shape, and a pair of mounting holes is defined in the base plate for mounting two ends of each latching member.
4. The buffering device of claim 3, wherein the air inlet has a circular shape, and a width of the shielding piece is greater than a diameter of the air inlet, but less than the diameter of the cylindrical casing.
5. The buffering device of claim 1, wherein the piston module comprises a piston rod, a valve attached to one end of the piston rod, and a curved mounting portion extending from another end of the piston rod; and a rim of the valve abuts against an inner surface of the cylindrical casing.
6. The buffering device of claim 5, further comprising a cover attached to the cylindrical casing for shielding an opening of the cylindrical casing, a mounting hole is defined in a central portion of the cover, and the piston rod extends through the mounting hole.
7. The buffering device of claim 6, wherein a diameter of the mounting hole is substantially equal to that of the piston rod.
8. A buffering device, comprising:
a cylindrical casing comprising a base plate;
a piston module, movably mounted in the cylindrical casing, and comprising a piston rod and a valve attached to the piston rod; and
a shielding piece pivotally attached to the base plate;
wherein the shielding piece comprises a main piece, a pivot mounting flange extends from the main piece, and a pivot hole is surrounded pivot mounting flange; a pivot post extends through the pivot hole for pivotably mounting the shielding piece on the base plate; an air inlet and an air outlet are defined in the base plate; a diameter of the air inlet is greater than that of the air outlet; when the valve is moving towards the base plate, pressure inside the cylindrical casing causes the shielding piece to rotate to a closed position, thereby blocking the air inlet; and when the piston module is moving away from the base plate, environmental pressure causes the shielding piece to rotate to an open position, thereby opening the air inlet.
9. The buffering device of claim 8, further comprising a pair of latching members, wherein two ends of the pivot post protrude from opposite sides of the pivot mounting flange and are latched by the pair of latching members.
10. The buffering device of claim 9, wherein each latching member has a U-shape, and a pair of mounting holes is defined in the base plate for mounting two ends of each latching member.
11. The buffering device of claim 10, wherein the air inlet has a circular shape, and a width of the shielding piece is greater than a diameter of the air inlet, but less than the diameter of the cylindrical casing.
12. The buffering device of claim 8, wherein the piston module the valve is attached to one end of the piston rod, and a curved mounting portion extending from another end of the piston rod; and a rim of the valve abuts against an inner surface of the cylindrical casing.
13. The buffering device of claim 12, further comprising a cover attached to the cylindrical casing for shielding an opening of the cylindrical casing, a mounting hole is defined in a central portion of the cover, and the piston rod extends through the mounting hole.
14. The buffering device of claim 13, wherein a diameter of the mounting hole is substantially equal to that of the piston rod.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. Method for monitoring the operation of a gas discharge lamp operated with an AC voltage, in which method a lamp voltage signal dependent on the voltage dropped across the gas discharge lamp is filtered with an attenuation that is different for a DC component and for a component having the frequency of the AC voltage, a positive and a negative peak value of the filtered lamp voltage signal are determined, an average value of the two peak values is determined and compared with a limit value, and a difference value between the two peak values is determined and compared with a limit value.
2. Method according to claim 1, wherein, in order to determine the two peak values, a positive storage capacitance is charged depending on the positive half-cycle of the lamp voltage signal and a negative storage capacitance is charged depending on the negative half-cycle of the lamp voltage signal, and after a further processing of the voltage of a storage capacitance said storage capacitance is partly discharged.
3. Method according to claim 2, wherein the storage capacitances are partly discharged in each case by temporary connection to at least one discharge capacitance.
4. Method according to claim 1, wherein the partial discharge of the storage capacitances is controlled by a controller that also controls the generation of the AC voltage.
5. Method according to claim 1, wherein the AC voltage for operating the gas discharge lamp is generated by a half-bridge connected to a DC voltage.
6. Method according to claim 1, wherein the average value of the two peak values is compared with an upper limit and a lower limit of a signal range and an alarm signal is generated if the average value is outside the range.
7. Method according to claim 1, wherein an average value alarm signal is generated depending on the comparison of the average value of the two peak values with a limit value and a difference value alarm signal is generated depending on the comparison of the difference value between the two peak values with a limit value, and the average value alarm signal is forwarded to an alarm device, only if it was active for longer than an average value alarm duration, and the difference value alarm signal is forwarded to the alarm device only if it was active for longer than a difference value alarm duration, wherein the difference value alarm duration is longer than the average value alarm duration.
8. Monitoring device for the operation of a gas discharge lamp from an AC voltage comprising an input for receiving a lamp voltage signal that is dependent on a voltage dropped across the gas discharge lamp and is filtered with an attenuation that is different for a DC component and for a component having the frequency of the AC voltage, comprising a positive peak value rectifier, which determines a positive peak value of a filtered lamp voltage signal, and comprising a negative peak value rectifier, which determines a negative peak value of a filtered lamp voltage signal, comprising an average value comparator, which compares an average value of the two peak values with a limit value, and comprising a difference value comparator, which compares a difference value between the two peak values with a limit value.
9. Monitoring device according to claim 8, which additionally has a filter, which has a different attenuation for a DC component and a component having a frequency of the AC voltage and filters the lamp voltage signal.
10. Monitoring device according to claim 8, wherein the peak value rectifiers have respectively a storage capacitance and respectively a discharge device which, after the evaluation of a peak value of the respective peak value rectifier, partly discharge the storage capacitance thereof.
11. Monitoring device according to claim 8, comprising an average value storage element, which stores in clock-controlled fashion the result of the evaluation of the average value of the two peak values and comprising a difference value storage element, which stores in clock-controlled fashion the result of the evaluation of the difference value between the two peak values.
12. Monitoring device according to one claim 8, comprising two timer elements, which in each case forward a connected evaluation signal only if the evaluation signal was active for a minimum time duration dependent on the respective timer element.
13. Monitoring device according to claims 8, wherein the monitoring device is part of a drive circuit for a gas discharge lamp and the drive circuit has a half-bridge circuit for generating an AC voltage for the operation of the gas discharge lamp and a controller that controls the half-bridge circuit and stops the operation of the gas discharge lamp depending on an alarm signal supplied to the controller by the monitoring device.