Added Matter Objection Considered

Western Oilfield Equipment Rentals Ltd v M-I LLC 2019 FC 1606 O'Reilly J
            2,664,173 / Shaker and Degasser Combination

Previous posts have given an overview of Western Oilfield Eqpt v M-I and discussed the best mode requirement. Western Oilfeild also considered an objection based on added mater. The specification of the 173 patent was amended after the application was filed, and Western argued that the amendment added new subject matter that could not reasonably be inferred from the original specification, contrary to s 38.2(2) of the Act and (then applicable) Rule 181. (Rule 181 has since been removed, presumably because it is redundant in light of 38.2(2).) O'Reilly J noted that “there is little Canadian law on the point” [238], and I must say that I am not aware of any at all. While O'Reilly J’s decision on the point largely turned on the facts, a brief discussion is warranted given the paucity of case law dealing with this provision.

O'Reilly J began by noting that:

[236] At trial, I ruled that the factual circumstances surrounding the amendments were not relevant to this issue. It is a matter of logic, not fact, whether the amendments are reasonably inferable.

In the first sentence of the paragraph O'Reilly J appears to be saying that the patentee’s motivation for introducing the amendments is not relevant. The second sentence is a bit confusing. As a general matter, I would have thought that whether the amendments would be reasonably inferable would be a matter of mixed fact and logic, as the question is to be answered by looking through the eyes of a skilled person. And indeed, in the subsequent analysis, O'Reilly J referred extensively to the evidence of the experts as to what could have been inferred.

As noted, O'Reilly J’s decision otherwise turned on the facts, but it is perhaps worth quoting one paragraph from the decision to illustrate the analysis.

Recall from my previous post that the invention relates to a machine called a “shale shaker,” used in the oil and gas industry to remove solids, aka “cuttings,” from the slurry that emerges from an active well, in order to separate the drilling fluid for reuse [6]. A shale shaker shakes the slurry over a screen to allow the fluid to fall through while the rock cuttings are carried away. Shaking alone does not remove all of the fluid, and the cuttings remain wet after passing through a standard shaker [33]. The invention consisted of a method and system for applying a vacuum (“pressure differential generator”) to the cuttings to recover more of the drilling fluid [35].

The prior art had disclosed a similar system using a continuous vacuum to suck fluid from the cuttings. The problem with that technique is that the continuous suction could cause cuttings to stick to the screen, clogging it and preventing fluid flow. The invention addressed this problem by varying the pressure, so that fluid would be sucked off in the high pressure intervals, and the rock cuttings would be released from the screen when the pressure dropped. This was described as “toggling” in the original claims, and “controlling air flow” in the amended claims. The point was crucial because Western’s product did not “toggle” the pressure differential, and so did not infringe claims limited to “toggling,” but it did control the air flow, and so infringed the amended claims [239]. O’Reilly J held as follows:

[251] First, while toggling was indeed an essential element of the original claims (and for that reason, Western did not infringe them), the original specification contemplated something broader. Paragraph 34 mentioned pulsing and toggling, but it went on to refer to the fact that “[m]anipulating the valve by opening and/or closing the valve, at least partially, may disrupt the flow of vapour from the sump, thereby affecting the pressure differential.” The concept of controlling air flow, not just pulsing and toggling, is reasonably inferable from this passage.