The Door into Summer (1956) by Robert A. Heinlein

Wikipedia wrote:The novel opens in 1970 with Daniel Boone Davis, an engineer and inventor, well into a long drinking binge. He has lost his company, Hired Girl, Inc., to his partner Miles Gentry and the company bookkeeper, Belle Darkin. She had been Dan's fiancée, deceiving him into giving her enough voting stock to allow her and Miles to seize control. Dan's only friend in the world is his cat, "Pete", a feisty tomcat who hates going outdoors in the snow.

Hired Girl, Inc. manufactures robot vacuum cleaners, but Dan had been developing a new line of all-purpose household robots, Flexible Frank, when Miles announces his intention to sell the company (and Flexible Frank) to Mannix Enterprises in which Miles would become a vice-president. Wishing to stay independent, Dan opposes the takeover, but is outvoted and then fired as Chief Engineer. Left with a large financial settlement, and his remaining Hired Girl stock, he elects to take "cold sleep" (suspended animation), hoping to wake up thirty years later to a brighter future. The examining doctor at the cold sleep facility immediately sees that Dan has been drinking. He warns him to show up sober or not at all 24 hours later for the actual procedure.

Wikipedia wrote:After becoming sober, Dan decides instead to mount a counter-attack. First he mails his Hired Girl stock certificate to the one person he trusts, Miles' stepdaughter Frederica "Ricky" Virginia Gentry. Dan confronts Miles and finds Belle in Miles' home. Belle injects him with an illegal "zombie" drug, reducing him to somnolent compliance. Belle and Miles discover Dan's plans to go into cold sleep and have him committed.

Dan wakes up in the year 2000, with no money to his name, and no idea how to find the people he once knew. What little money Belle let him keep went with the collapse of Mannix in 1987. He has lost Pete the cat, who fled Miles' house after Dan was drugged, and has no idea how to find a now middle-aged Ricky.

Dan begins rebuilding his life. He persuades Geary Manufacturing, which now owns Hired Girl, to take him on as a figurehead. He discovers that Miles died in 1972, while Belle has become a shrill and gin-sodden wreck. All she recalls is that Ricky went to live with her grandmother about the time Dan went into cold sleep. Her scheme with Miles collapsed, as Flexible Frank disappeared the same night she shanghaied Dan.

Dan finds Flexible Frank in use everywhere, acting as hospital orderly, bellhop, and a thousand other menial jobs once filled by people. It is called "Eager Beaver", made by a company called "Aladdin Auto-engineering," but Dan can see that someone has taken his prototype and developed it. He is even more baffled to find that the patent is credited to a "D. B. Davis."

His friend Chuck at Geary lets slip that he once saw time travel working, in a lab in Colorado. At that point Dan finds that Ricky has been awakened from cold sleep and left Los Angeles for Brawley, California. Dan tracks her to Yuma, Arizona, where she was apparently married. When Dan looks at the marriage register, he finds that she married "Daniel Boone Davis". He immediately empties his bank account and heads for Colorado.

In Boulder, he befriends Dr. Twitchell, a once-brilliant scientist reduced to drinking away his frustrations. Eventually, just as Chuck had told him, Twitchell admits to having created a time machine of sorts. With the machine powered up, Dan goads Twitchell into sending him back to 1970, some months before his confrontation with Miles and Belle.