The USPTO Patent Assignment Search database contains all recorded patent ownership information from August 1980 to the present.  According to USPTO, “When the USPTO receives relevant information for its assignment database, the USPTO puts the information in the public record and does not verify the validity of the information. Recordation is a ministerial function--the USPTO neither makes a determination of the legality of the transaction nor the right of the submitting party to take the action.”

For US patent, here is an example:

• Go to Patent Assignment Search 
• Quick look > Assignor 
• Type: Hlavinka  (Hlavinka is an individual inventor) 
• Look into each record to find Assignee info, or may use text mining tool to identify changing ownership.
• One may also search by company name. e.g. Gambro bct. 

Tip:

• "Assignor" refers to the one giving away the patent rights, "assignee" refers to the one receiving the rights
• An original patent application may often lead to continuing applications. All continuing applications steaming from the original usually also belong to the assignee 
• Keep in mind that patent ownership may change over times and the change is not required to be reported 

For more info, see USPTO website.