Horology: time measuring systems or devices – Power supply details – Electrical
Reexamination Certificate
2001-03-16
2004-10-12
Martin, David (Department: 2841)
Horology: time measuring systems or devices
Power supply details
Electrical
Reexamination Certificate
active
06804171
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a temperature difference drive unit that acquires mechanical energy based on temperature fluctuation in the environment in which the drive unit is used and generates a drive force or electrical power from the mechanical energy. The invention also relates to an electric device, a timepiece and a light electrical appliance employing such a temperature difference drive unit.
2. Description of the Related Art
Mechanical timepieces such as wristwatches and pocket watches which are driven by mechanical energy accumulated in a main spring are widely in use. Some mechanical timepieces are of the manual-winding type whereby the main spring is wound by hand. Since this type of timepiece stops when the mechanical energy accumulated in the main spring is completely released, periodic winding of the main spring is required. Further, since the manual-winding mechanical timepiece no longer shows accurate time once it has stopped, the timepiece also has to be reset. Periodic winding and resetting of such a timepiece is inconvenient to the user.
Accordingly, a self-winding watch having a rotatably oscillating weight for automatically winding the main spring has been used. Since the main spring of the self-winding watch is automatically wound by movement of the watch, mechanical energy is accumulated in the main spring when the user wears the watch (e.g., on the wrist) during normal activity, so that the self-winding watch keeps moving without stopping under such conditions. However, such a self-winding watch stops accumulating energy in the mainspring when it is detached from the user's wrist and placed at rest. If such a watch remains at rest too long, the mechanical energy stored in the main spring will be released and the watch will stop.
While the self-winding function is useful for wrist watches which can be moved during normal use, it is not applicable for timepieces, such as table clocks, that are intended to remain at rest. Accordingly, a table clock that obtains drive energy from a temperature change in the natural environment has been proposed. For instance, a table clock “ATMOS” of Jaeger Lecoultre Co., Ltd. obtains drive energy from the temperature change in the natural environment using the expansion force of a material. Specifically, a phase change material in which the phase changes between gas and liquid at room temperature is accommodated in an expandable container, such that the main spring is wound as a result of the volume change of the phase change material which is caused by the temperature change. The clock is then driven by the mechanical energy accumulated in the main spring. The phase change material is a material whose phase changes between gas and liquid such as ammonia, carbon dioxide, alcohol and methyl chloride. Since the main spring of the clock has the capacity to store enough mechanical energy to continuously drive the clock for approximately seventy-two hours, enough mechanical energy can be stored in the main spring from the temperature changes that occur in an ordinary environment to prevent the clock from stopping in most circumstances, thus allowing semipermanent movement thereof.
However, since an electronic device such as a high accuracy electronic timepiece that employs a quartz oscillator cannot be driven by the above arrangement, there is another arrangement where a power generator is driven by the drive energy obtained by the temperature change (Japanese Patent Laid-Open Publication No. Hei 10-14265, Japanese Patent Laid-Open Publication No. Hei 6-341371). In this case, a phase change material whose phase changes between gas and liquid at room temperature is accommodated in an expandable container, as in the above-described table clock. A volume change of the phase change material caused by the temperature change is converted into a rotary drive force by a rack and the rotary drive force used to actuate the power generator. A prime mover such as a motor is driven by the electric power generated by the power generator to obtain the drive force for driving the timepiece.
In order for the rack to convert the volume change of the phase change material into the rotary drive force, the rack is fixed when the temperature continues to increase or decrease. When the temperature change reverses direction, the fixed rack is released as the phase change material rapidly and completely expands or contracts, thereby improving efficiency of converting electric power. Accurate time keeping can be maintained by installing a wave correction function into the timepiece.
There are certain disadvantages in using a phase change material that changes between the gas and liquid states to provide the initial source of energy. When the phase change material changes to gas, its thermal conductivity is significantly lowered, thus deteriorating resistivity to change in ambient temperature. Thus, the time from decrease in ambient temperature to volume reduction of the phase change material can be delayed. Accordingly, such a phase change material does not generate mechanical energy responsively in accordance with temperature difference, thus deteriorating conversion efficiency.
Further, since mixing different types of phase change materials whose phases change between gas and liquid results in a chemical reaction, the phase change temperature cannot be adjusted by mixing such different types of the phase change materials. As a result, the phase change material is contained in a variable volume container, where the internal pressure (i.e., the pressure applied to the phase change material) is increased by contracting the volume of the container in order to set the boiling point (phase change temperature) of the phase change material at a desired temperature.
Accordingly, such a container containing the phase change material is required to have a variable volume and be extremely airtight to avoid leakage of the high-pressure air to the outside, thus making production of the container difficult.
Further, since the above container contains the phase change material as a gas, a substantial amount of volume is required and a compressing means such as a strong spring is required in order to maintain the high pressure inside the container, so that size reduction of the whole device is difficult.
Moreover, since a phase change material has a prominently large expansion rate in changing between the gas and the liquid phases, a large pressure results when the phase change material is evaporated to saturated vapor, causing a large fluctuation in the pressure. Further, the high internal pressure to which the container is subjected, increases the likelihood that the container will experience mechanical fatigue, thereby making it difficult to manufacture a container having sufficient durability, thus further making production of the container difficult. While using a rigid and heavy container improves durability, such a container increases the size and weight of the device.
In the power generator described in the above-identified publications, since the fixed rack is released to intermittently generate power when the temperature change direction is reversed, the power generator is actuated many times when the temperature increase and decrease are repeated again and again within a short period of time.
Also, since the power cannot be efficiently generated until the power generator reaches a predetermined number of revolutions, drive energy is lost when the power generator is actuated many times within a short period of time, and is thus unable to sufficiently improve electric power conversion efficiency.
Further, in the aforesaid device, since number of revolutions of a rotor of the power generator is increased and decreased so that the voltage applied to the load of the power generator becomes constant, the rotor cannot be always rotated with the best power-generating efficiency. Therefore, the power-generating efficiency cannot be so improved and, since the available energy relative to the inputted th
Fujimori Shigeyuki
Miyazawa Kenichi
Takahashi Osamu
Goodwin Jeanne-Marguerite
Martin David
Seiko Epson Corporation
LandOfFree
Temperature difference drive unit, and electric device,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Temperature difference drive unit, and electric device,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperature difference drive unit, and electric device,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3311979