delphion offeres a one day free trial via the google ads. There you can download these:
US03380031__.pdf ->Non-HP; very interesting calculator
US03588873__.pdf ->Information Display Apparatus
US03623156A1.pdf
US03641328A1.htm
US03668697__.pdf ->Noncontacting Keyboard (used in desktop calcs)
US03675213__.pdf
US03678466__.pdf
US03693162__.pdf
US03711690A1.pdf ->Calculator and tester thereof
US03737871A1.pdf
US03749899__.pdf ->Binary/BCD ALU
US03750105A1.pdf
US03755697__.pdf
US03757068__.pdf
US03766370A1.pdf ->Cordic CPU
US03769621A1.pdf
US03781820__.pdf
US03825736__.pdf
US03839630__.pdf
US03855461__.pdf
US03859635__.pdf
US03863060__.pdf
US03892958__.pdf
US03893173__.pdf ->Card reader
US03941953__.pdf ->Tactile feedback keyboard
US03946218__.pdf
US03955074__.pdf
US03967370__.pdf ->Keyboard/switch manufacturing
US03971925__.pdf
US03973110__.pdf
US03976926__.pdf
US03986186__.pdf
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US03996562__.pdf
US03997765__.pdf
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US04001569__.pdf
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US04012725__.pdf
US04028538__.pdf
US04035627__.pdf
US04037092__.pdf
US04047012__.pdf
US04052604__.pdf ->binary adder
US04054788__.pdf
US04055757__.pdf
US04059750__.pdf
US04063221__.pdf
US04075679__.pdf
US04078257__.pdf ->Calc with electronically alterable key symbols
US04089059__.pdf
US04091270__.pdf ->Calc with Bar code reader
US04099246__.pdf
US04106677__.pdf
US04109315__.pdf ->HP-01
US04126898__.pdf
US04127897__.pdf
US04143809__.pdf
US04145742__.pdf
US04145752__.pdf
US04152769__.pdf
US04152770__.pdf
US04152771__.pdf
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US04156918__.pdf
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US04158228__.pdf
US04158231__.pdf
US04158233__.pdf
US04158285__.pdf ->HP-01
US04159525__.pdf
US04161031__.pdf
US04162532__.pdf
US04164019__.pdf
US04164039__.pdf
US04172281__.pdf ->Microprogrammable Control Processor
US04177518__.pdf
US04177520__.pdf
US04178633__.pdf
US04180854__.pdf
US04181965__.pdf
US04181966__.pdf
US04187547__.pdf
US04197586__.pdf
US04198684__.pdf
US04203152__.pdf
US04232382__.pdf ->HP-01
US04281390__.pdf
US04291385__.pdf
US04309761__.pdf
US04314112__.pdf
US04322816__.pdf
US04330839__.pdf
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US05175828__.pdf
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US05202994__.pdf
US05216627__.pdf
US05258748__.pdf
US05260886__.pdf
USD0244862__.pdf
USD0245107__.pdf
USD0245810__.pdf
USD0249090__.pdf
USD0249243__.pdf
USD0249244__.pdf
USD0256133__.pdf
USD0321865__.pdf
USD0333129__.pdf
USRE032040__.pdf ->Elec. alterable key symbols