Significant accounting policies Other intangible assets with definite lives (Details) (USD $)	Jan. 31, 2014	Jan. 31, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Patents, Gross	$ 2,600,000
Finite-Lived Intangible Assets, Accumulated Amortization	2,230,000	2,180,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	48,900
Finite-Lived Intangible Assets, Amortization Expense, Year Two	45,700
Finite-Lived Intangible Assets, Amortization Expense, Year Three	41,900
Finite-Lived Intangible Assets, Amortization Expense, Year Four	38,800
Finite-Lived Intangible Assets, Amortization Expense, Year Five	28,800
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	$ 168,400