Early in 1936 zippo’s 3-barrel hinge was replaced by a 4-barrel one for more durability. The hinge remained on the outside of the lighter case
On March 6th 1936 the patent on zippo lighters was approved and from that moment on zippo’s were marked “pat. 2032695” on the bottom of the case. An example of this can be seen in the picture below. Late in 1936 the hinge was moved to the inside of the case.
1938
In 1938 zippo stated using an all new pressing machine which made the production of zippo lighters less labour intensive. Instead of soldering the top and bottom to the lighter case the upper and lower cases were now pressed from one piece of brass. This meant that outer cases no longer excisted of 8 parts (Top and bottom case, top and bottom, camstop, upper and lower hinge and the hinge pin) but
of only 6 parts. Because a large part of the soldering process could now be left out zippo’s could be produced cheaper and quicker.
Changes to the insert were also made to lower the production costs and improve production speed. The little piston and spring assembly under the cam was replaced by a humped leafspring which was held by a rivet through which the wick was pulled.
The all new 1938 model zippo replaced the square type zippo’s and had smooth rounded corners, a flat bottom and rounded top. Zippo advertised it to be the more streamlined model.
Advertising and personalisation of zippo's wasn't done
with metalliques anymore because zippo had just bought an engraving machine.
This also helped to lower the costs and speed up production to the growing
demand. An example of the new type of zippo with engraved advertising can
be seen above.
1940
Though a 1940 model looks and feels like a 1938 one there
is a slight difference between the two. Instead of soldering the camstop
in the upper case half zippo now made it part of the hinge. Now there were
only 18 parts needed to build a zippo instead of 23 parts in 1933. Zippo
sales grew steadily and zippo production was more efficient than ever before.