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US Patent: 1,845,428
Screw Thread Lock
Ernest R. Llewellyn - Arlington, MA

USPTO Classifications:
192/131R, 38/39

Tool Categories:
metalworking machines : metalworking machine mechanisms

Hendey Machine Co. - Torrington, CT

Not known to have been produced

none listed

Patent Dates:
Applied: Jun. 30, 1930
Granted: Feb. 16, 1932

Patent Pictures:
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"Vintage Machinery" entry for Hendey Machine Co.

This invention relates to screw threads and more particularly to means for preventing relative rotary motion between two threaded members, and while not limited thereto is particularly adapted to locking an externally threaded screw in an internally threaded member.

It is well known that the camming action of a screw thread will, under vibration, cause a screw to become loose and to back out of a tapped member. To overcome this action to some extent it has been necessary to hold a very limited tolerance between the screw thread and the tapped member and while this is a costly operation its effectiveness is not assured. Another general practice has been to secure a screw in a tapped hole by means of superimposing a so-termed jamb-screw after the first screw has been positioned. This is in accordance with the check nut theory. This practice is not advanta eous when it is desired to obtain a required a justment of the first screw as the tightening of the jamb-screw has a tendency, when it comes in contact with the first screw, to rotate and tighten the first screw. It is also possible for the above camming action to cause both of this practice it is often necessary to use a larger diameter amb-screw which requires an additional drilling and tapping operation.

To overcome the above disadvantages my locking device is contained permanently within the screw as is best illustrated by a fillister or headless screw wherein a screwdriver is inserted into a slot to rotate the screw. When the screw-driver is inserted into the screw slot, the locking device is actuated and disengaged from the internally threaded member. As the screw-driver is withdrawn from the screw slot my locking device automatically engages with the threaded portion of the internally threaded member thereby locking the two members in position thus preventing further relative rotary motion between the two members.

The object of my present invention is to provide a self-contained locking screw that may be positioned in a tapped member and when so positioned further relative rotary movement is arrested.

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