Window sash counterbalance with varying lift
CA 2106557 A1 · Owner: Caldwell Manufacturing Company · Inventors: Davis, Donald D.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A counterbalance for a window sash (28) includes a torsion spring (10), a follower nut (20) and a spiral rod, (22) threadably engaged with the follower nut (20). The spiral rod (22) has a pitch that is varied along one part of its length to produce a substantially constant lifting force throughout most of a range of sash travel between a lowered position and an intermediate position. However the pitch is, further varied along another part of the length of the spiral member to produce a larger lifting force within a remaining portion of the range of sash travel from the intermediate position to the raised position.
Read the whole patent
Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Filed September 20, 1993. No grant is recorded for it in Canada; had it been granted, its 20-year term would have ended September 20, 2013.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by September 20, 2015.
- We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
Timeline
Timeline From CIPO dates
Sources & verification
Official CIPO records
Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.