This is an excerpt from a discussion to be found on the Industry Canada web site on Intellectual Property Policy
Invention can result from a combination of well–known features or elements which contribute to an improved result, particularly if the combination has never been made before, and more particularly, if the result has some special value proved by its utility and appreciation. It has been authoritatively stated that the art of combining two or more parts into a new combination whether they are new or old, or partly new and partly old, so as to obtain a new result, or a known result in a better, cheaper, or more expeditious manner, is valid subject–matter if there is sufficient evidence of thought, design, and ingenuity in the invention, and novelty in the combination.
On the other hand, there can be no invention in a mere combination of features, each of which is well–known and contributes no more than its well known functions. There is no invention in altering proportion of ingredients that were used before in combination when the proportion is not necessary to success, nor to alter the size and shape of the articles or to merely substitute materials. Invention exists where fresh advantages have been developed and disadvantages overcome. Ordinarily, the use of one material instead of another in constructing a device or carrying on a known process is obvious and not an invention. It can, however, be called an invention if some new and useful results, such as an increase in efficiency, or an overall saving in operation is a result. A new means of using an old machine, or the adaption of an old machine to produce a new result, or the use of an old thing to cure a defect in an old machine may be sufficient to show invention.
It is well established that a mere “scintilla of invention” is sufficient to support the validity of a patent. In the Federal Court Case, O’Cedar of Canada Limited v. Mallory Hardware Products Limited, Thorson P. summarizes a number of decisions in supporting his findings that simplicity does not negate invention. In many cases a small or slight difference can produce large results.