Plaintiff, complaining that the defendant had infringed and was continuing to infringe upon its United States Letters Patent No. 2,753,877, sought an injunction and damages. The defendant attacked the patent as invalid and denied infringement.

After a full trial to the court without a jury, and upon detailed findings of fact and conclusions of law, that the patent was valid but not infringed, the district judge gave judgment for the defendant, and plaintiff has appealed.

Here, attacking the findings of fact and conclusions of law, that the device constructed and used by defendant does not infringe the patent in question, appellant argues that appellee’s structure is a copy of appellant’s structure with certain minor changes.

Appellee, taking strong issue with appellant on this point and arguing that what is before the court is simply a review of the sufficiency of the evidence, urges upon us that, when the crowded state of the prior art and the necessarily narrow scope of plaintiff’s combination unit are considered, the district court’s finding of non-infringement must be sustained and the judgment affirmed.

Agreeing that the invention is a narrow one in an already crowded field and that, in interpreting the patent, it is to be strictly construed with regard to the prior art and the alleged infringing device, we find ourselves in agreement with appellee and the district judge that there was no infringement. The judgment is, therefore, affirmed.