Appeal from the District Court of the United States for the Eastern District of New York.
Before MANTON, L. HAND, and CHASE, Circuit Judges.
The plaintiff, a New York corporation, which as assignee owns all right and title to United States letters patent No. 1,771,020, brought suit for infringement of that patent against the defendant, another New York corporation, whose principal place of business is located in the Eastern district of New York.
The patent, granted to Thurn and Engels, July 22, 1930, is for a traveling-tray oven designed for baking food products and more especially relates to the baking of bread. The oven claimed to infringe was used by the defendant to bake bread; was purchased by it of the Petersen Oven Company of Chicago which openly defended this suit; and was used at the defendant's premises in Brooklyn, N.Y.
The advantages which were considered attainable by this patent over what had gone before related to a practical separation of what is called loaf-conditioning and bake-finishing so that the first was virtually carried to completion in a conditioning chamber before the latter commenced. This feature is well set forth in the following quotation from the specifications:
"So far as we are aware, conditioning and finishing have not heretofore been definitely segregated in ovens of the horizontal or vertical and multiple-pass, traveling-tray type, but usually the two operations have been mixed and allowed to occur more or less together. The result, oven control that is inherently imperfect, has prevented the general adoption of ovens of the multiple pass tray type for use in small and medium capacity general purpose bakeries. Such plants must produce various goods, requiring an oven adaptable to many kinds of loaf treatment.
"This invention enables the baker to produce from one oven any desired kind of goods, for he can properly apportion the supply of heat, the relative humidity and the baking time in each of the various chambers or passes. If he desires a loaf with large volume and a glossy top he can increase the humidity in the conditioning chamber, decrease the burner heat, and by changing the rate of tray travel, can lengthen the baking time.
"To change to a small volume, dull crust loaf, he decreases humidity, increases burner heat and slightly shortens baking time. For pound cake he increases both humidity and heat supply in the conditioning chamber and lengthens the baking time.Moreover, he can quickly re-adapt the functioning of the various passes of this oven from the requirements of white bread to those of rye or so-called hearth bread, or cakes, biscuits and other products. Any combination of such changes is easily brought about in a few minutes in an oven having the improvements herein described."
And what is meant by loaf-conditioning and by bake-finishing is defined by the specifications:
"Loaf-conditioning as the term is here used, is the conversion of a piece of proofed dough into a loaf that is virtually sized, shaped and preheated, but unbaked. Bake-finishing is the conversion of the conditioned loaf into a finished article by baking."
The oven of the patent has a slowly moving chain conveyor equipped to carry trays of dough which so closely follow one another as to form a continuous line of material when the oven is in operation. There are pulleys over which the conveyor passes to change its course through the oven to carry the dough first through the conditioning chamber; then up and on through the bake-finishing stage by carrying it back toward the front of the oven over the conditioning chamber; then up again and on to the back of the oven; then down and toward the front again to appear as fully baked bread at a point near the original place of entry where the same operator who puts in the dough takes out the bread.
After the dough leaves the conditioning chamber, there is nothing new about what happens to it in the rest of the oven which it traverses by means of the rather ingeniously arranged conveyor system. Heat at the required temperature to finish baking it by the time it arrives at the exit is applied by gas burners to the parts of the oven through which it passes. Of course bread baking goes back into the haze of antiquity, and baking on a conveyor moving in an oven is itself admittedly old.
The construction of the conditioning chamber is, however, interesting, and it is there that whatever novelty there is in this patent resides. As is generally known, the dough which ultimately is baked into bread is mixed with yeast to "raise" it. The increase in the size of the dough as it passes through the conditioning chamber is primarily due and theoretically, at least, entirely due to the action of the yeast. While it may be that in the patented oven some expansion there takes place because of the independent action of heat, it is at best slight and may be ignored. In practice, the yeast continues to expand the dough until a point is reached ...