Background
Vacon Oyj (Vacon) sought patent protection on its invention called "Limitation of voltage pulse" on 20 June 2007. The application consisted of two independent claims (1 and 5) and dependent claims 2-4 and 6-12. The Patent and Registration Office (PRH) granted a patent for the invention (FI 119669) on 30 January 2009.
| FI 119669, Figs. 1-2. |
ABB Oy (ABB) lodged an invalidation claim against the patent. Vacon answered by filing amended patent claims (independent claims 1 and 5 and dependent claims 2-4 and 6-11), but PRH accepted the invalidation claim and revoked the patent on 22 March 2012. According to PRH, the independent claims 1 and 5 are lacking novelty and the claims 1-11 do not involve an inventive step.
Vacon did not agree with the decision of PRH and lodged an appeal at the Market Court. Vacon requested the Market Court to reverse the decision of PRH. Furthermore, according to Vacon, the patent application should be accepted in accordance with the amended claims that were under examination in the decision of PRH.
The Market Court
According to section 2 of the Patents Act (550/1967), patents may only be granted for inventions which are new in relation to what was known before the filing date of the patent application, and which also involve an inventive step with respect thereto. Everything made available to the public in writing, in lectures, by public use or otherwise is considered to be known.
The independent claims 1 and 5 (translated with the help of EP2020742):
Claim 1:
Method for controlling the output voltage pulses of a PWM frequency converter, in which PWM frequency converter is a network bridge (10) for rectifying the alternating voltage of the supply network into the DC voltage (UDC) of the DC intermediate circuit, which is filtered with a filtering capacitor (CDC), a load bridge (11) comprised of phase switches implemented with power semiconductor components, which forms the AC output voltage (U, V, W) from the DC voltage of the intermediate circuit for controlling the load (M),
characterized in that for setting the average speed of change in the output voltage in connection with each change of state of the output voltage at least one power component controlled by a phase switch is controlled such that before the output voltage remains in its position subsequent to the change of state it is on at least once for a short period, typically of less than 1µs (a micropulse), in the position prevailing before the change of state, and a filter containing passive components, with which the voltage of the micropulses is filtered into the final output voltage of the frequency converter.
Claim 5:
Arrangement for controlling the output voltage pulses of a PWM frequency converter, in which PWM frequency converter is a network bridge (10) for rectifying the alternating voltage of the supply network into the DC voltage (UDC) of the DC intermediate circuit, which is filtered with a filtering capacitor (CDC), a load bridge (11) comprised of phase switches implemented with power semiconductor components, which forms the AC output voltage (U, V, W) from the DC voltage of the intermediate circuit for controlling the load (M), and a control unit,
characterized in that for setting the average speed of change in the output voltage in connection with each change of state of the output voltage at least one power component controlled by a phase switch is fitted to be controlled such that before the output voltage remains in its position subsequent to the change of state it is on at least once for a short period, typically of less than 1µs (a micropulse), in the position prevailing before the change of state, and that the arrangement comprises a filter containing passive components, with which the voltage of the micropulses is filtered into the final output voltage of the frequency converter.
Novelty
Prior art contains the following documents:
- D1: Deisenroth H., Trabert C. Vermeidung von Überspannungen vei Pulsumrichterantrieben. ETZ. 1993, Bd. 114, Heft 17, s. 1060–1066, and
- D2: DE 4203054.
The court considered that the invention is new in relation to what was known before the filing date of the patent application. According to the court, the prior art does not include a solution in which a micropulse technique is combined with a filter containing passive components.
Inventive step
The court considered that the purpose of the combination of a micropulse technique and a filter containing passive components is to reduce the average speed of change in the output voltage. If the speed of change is too high, it could damage a motor connected to the frequency converter. The description of the invention does not define any other effect which is acquired by using simultaneously a micropulse technique and a filter containing passive components.
According to the court, the reduction of the speed of change by using a micropulse technique or a filter containing passive components is known from the prior art D1. Therefore, it would have been obvious to the person skilled in the art to combine a micropulse technique with a filter containing passive components.
The appellant also argued that the invention is reducing the costs, size and weight of the required apparatus. The court dismissed these arguments because the claims do not include any features that would clearly highlight these benefits.
Therefore, the invention does not involve an inventive step.
The action was dismissed.
