The Patent for Patting Yourself on the Back
In 1986, the USPTO granted a patent for a device consisting of a simulated human hand on a spring-loaded arm, mounted so that a person could reach up, pull it down, and administer a congratulatory pat to their own back.

US4608967 was granted on September 2, 1986. The title is "Apparatus for Patting a Person on an Upper Portion of a Back of the Person" — which is a remarkably precise way of describing a machine for patting yourself on the back. The drawings show exactly that: a simulated human hand, mounted at the end of a pivoting arm, arranged so that the user can grasp a handle, swing the hand up and over their own shoulder, and deliver a series of approving pats to their own back.
The patent explains its purpose without a trace of irony. It observes that people frequently deserve congratulation for their accomplishments but do not always have anyone present to provide it, and that the gesture of a pat on the back is a well-understood form of positive reinforcement. The device, therefore, allows a person to supply this reinforcement to themselves, at will, whenever a moment of self-congratulation is required.
The engineering
The mechanism is described in full technical detail. There is a pivot, an arm, a counterweight or spring arrangement to control the motion, and the hand itself — molded to approximate a real human hand so that the pat feels appropriately authentic. The patent specifies the geometry required to bring the hand into contact with the correct "upper portion" of the back, and describes the pivoting action that produces the patting motion rather than a single static press.
Someone worked this out carefully. The figures are neat and properly labeled. The claims are drafted in the formal, hedge-everything language of real patent prosecution. The application was examined and granted like any other. By every procedural measure, the self-back-patting machine is exactly as legitimate a patent as the telephone.
Why it endures
The pat-on-the-back apparatus is a fixture of "most ridiculous patents" collections, and it belongs to a specific and beloved subgenre: the sincere novelty. It is not a method patent of questionable obviousness, and it is not a cynical attempt to monopolize something ordinary. It is a real, buildable mechanical device whose entire reason for existing is a small, human, faintly melancholy joke — the idea that a person might need, and be unable to obtain, a simple gesture of encouragement, and might therefore build a machine to provide it.
There is no evidence the device was ever manufactured or sold, which places it among the enormous population of patents that exist only as documents — granted, archived, and never built. But it captures something the more famous patents do not. The telephone and the transistor tell you what people needed. The machine for patting yourself on the back tells you something about how they felt.
See the original
The full text and figures of US4608967 are on patents.us.
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