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On December 24, 2009, the Osaka District Court found that the patent (JP 3117169 B) in suit was invalid and unenforceable because the application fails to comply with a requirement under former Article 36 (5) (v) which reads that the invention for which a patent is sought must be disclosed in the detailed description (“Support Requirement”).  
 
INVENTION

The invention in this case is directed to an electric level sensor which generates a signal to an apparatus for measuring a liquid level in a liquid tank and controlling various functions, for use, in particular, in a sewage pump unit for energizing/de-energizing a pump.  One of the purpose of the invention is to provide a level sensor which is designed so as to attain its functions properly even when it is exposed to an intensive external force from rapid flow of liquid or floating members (‘169 Patent, at paragraph [0008]).  For this purpose, the independent claim 1 below includes a limitation “a weight of said counterbalancing weight is at least 30% of a total weight of said sensor when said sensor is surrounded by air.”

Independent claim 1 is reproduced below:
1. A level sensor for connecting/disconnecting an electric function so as to energize/de-energize a motor in an electrically driven pump according to a level of a medium to be pumped, characterized in that
    said sensor comprises a hollow body suspended freely by an electric cable (2), said cable being connected to a micro-switch (15) mounted within said hollow body;
    said switch is operable into a connecting/disconnecting position with an aid of a movable weight provided within said hollow body;
    said movable weight, which is designed as a counterbalancing weight, is supported within said hollow body for rotation about an axial line extending through said counterbalancing weight between two different terminal positions, so that one of surfaces of said counterbalancing weight activates directly or indirectly said micro-switch (15);
a weight of said counterbalancing weight is at least 30% of a total weight of said sensor when said sensor is surrounded by air, said sensor being made of said hollow body (1), said micro-switch (15), said counterbalancing weight (9), and means (5, 6, 7, 8) for rotatably supporting said counterbalancing weight within said hollow body;
a gravity center (10) of said counterbalancing weight (9) is on one side of a vertical line extending through a center of a profile of said hollow body of said sensor when said sensor is surrounded by said air to take a principal vertical position; and
said sensor is inclined from a vertical position while being freely supported from said electric cable when said sensor is immersed in a liquid. (Emphasis added)

DISCLOSURES
The specification describes as follows:
[0012] In the position shown in Fig. 1, the body is completely or substantially completely surrounded by air.  In this state, the gravity center 10 of the counterbalancing weight in on the left side of the bearings 6, 8, so that the counterbalancing weight 9 tends to rotate in the counterclockwise direction about its bearing.  The rotation completes when one of the surfaces brings into contact with the left-side edge of the circular connecting plate 5.  Immediately before the counterbalancing weight reaches this position, the surface 13 thereof activates the elastic yoke 16 on the micro-switch 15 mounted on the connecting circular plate 5 to connect or disconnect the electric circuit of the micro-switch.
[0013] As long as the level sensor is primarily surrounded by air, i.e., the water level of the sewage, the sensor retains the vertical position and the micro-switch maintains its connecting/disconnecting position.
[0014] As the water level begins to elevate, the level sensor eventually initiates to incline and, finally, reaches the primarily horizontal position shown in Fig. 2.  By suitably selecting the volume and weight, the sensor takes the horizontal position, irrespective of how much the water level goes up above the sensor.
[0015] If the sensor starts from its the horizontal position, the counterbalancing weight 9 below and on the right of the bearings 6, 8 rotates in the clockwise direction about the bearings 6, 8.  This rotation is restricted when one of the surfaces of the counterbalancing weight 9 brings into contact with the inner surface of the hollow body 1.  During this movement, the surface 13 of the counterbalancing weight loses any contact with the connecting circular plate or the elastic yoke 16.  Then, the micro-switch is activated to take another position which means that the switch is connected or disconnected.
[0016] In order for the micro-switch to stop reliably, the counterbalancing weight 9 is relatively heavy and constitutes a considerable part of the total weight of the level sensor.  Simultaneously, however, the sensor should not be too heavy due to the manufacturing reasons.  Although the acceptable, secure minimum value is 30% of the total weight, the appropriate value is from 50% to 80%.  Also, the relationship of the total weight/volume will be selected in relation with the density of the liquid to be controlled, to ensure that the level sensor takes the primarily horizontal position when it is surrounded by liquid.
     
DEFENDENT’S ARGUMENT
The defendant argued that although the specification describes that the micro-switch can reliably be turned off by employing a structure in which the micro-switch moves into the connecting/disconnecting position in response to the rotation of the counterbalancing weight about rotational axis according to the change of the liquid level and also by setting the weight of the counterbalancing weight 30% of the total weight of the sensor, the technical reason of the limitation that the weight of the counterbalancing weight be at least 30% of the total weight of the sensor is not supported theoretically or experimentally.  

DECISION BY THE COURT
In determining whether the application complies with the support requirement, the court relied on the IP High Court’s landmark decision H17(Gyo-Ke)10042 (IP High Court. 2005) (en banc), which says that that “whether the description of the claim complies with the written description requirement of the specification should be determined, through the comparison between the descriptions of the claim(s) and the specification; by
Q1: whether the claimed invention is fully described in the detailed description to the extent that those skilled in the art could understand from the detailed description that the problems to be solved by the invention is solved by the invention; or
Q2: even if not disclosed or suggested in detailed description, whether the problem to be solved by the invention is such that those skilled in the art can understand in light of the technical common sense available at the time of filing.
Regarding the first question, the court found that the detailed description fails to disclose the reason why the limitation of the weight of counterbalancing weight relative to the total weight of the sensor is significant in retaining the level sensor substantially in the horizontal position and, thereby, turning off the micro-switch reliably.  Also, regarding the second question, the court found that it is not a technical common sense that the weight ratio of the counterbalancing weight to the sensor is significant in supporting the level sensor stably in substantially the horizontal position.  
In view of the foregoing, the court said that those skilled in the art could not understand the technical significance, in light of the technical common knowledge at the time of filing or the description of the application, in setting the weight of the counterbalancing weight 30% of the total weight of the sensor or in setting the weight of the counterbalancing weight more than a certain ratio of the weight of the sensor, in order to attain the advantage that “the switch is reliably activated even if it is exposed to external forces from the rushing flow of liquid or the floating substances during it operation”.  Accordingly, the court concluded that the specification fails to comply with the support requirement and, therefore, the patent is invalid and unenforceable.

http://www.courts.go.jp/hanrei/pdf/20091225094252.pdf