1. A process for preparing a rigid polyurethane foam, comprising
a) forming a reactive mixture consisting of
1) a polyol mixture that includes (i) a reaction product of a C2-C4 alkylene oxide with 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, or a mixture thereof, the reaction product having a hydroxyl functionality of 3.7 to 4.0 and a hydroxyl equivalent weight of from 100 to 130, (ii) 20 to 70% of a sorbitol or sucrose and glycerin initiated polyether polyol having an average functionality of 4.5 to 7 hydroxyl groups and a hydroxy equivalent weight of 100 to 175 (iii) 2 to 20% by weight of an ethylenediamine-initiated polyol having an equivalent weight of 100 to 225 and (iv) 0 to 15% by weight of a non-amine-initiated polyol having a functionality of 2.0 to 3.0 and a hydroxyl equivalent weight of 200 to 500;
2) at least one hydrocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, fluorocarbon, dialkyl ether or fluorine-substituted dialkyl ether physical blowing agent; and
3) at least one polyisocyanate;
4) water;
5) one or more catalysts for the reaction of the polyols and water with the polyisocyanate;
6) a surfactant; and
7) optionally one or more of a filler, a colorant, an odor mask, a flame retardant, a biocide, an antioxidant, a UV stabilizer, an antistatic agent; and
b) subjecting the reactive mixture to conditions such that the reactive mixture expands and cures to form a rigid polyurethane foam.
2. The process of claim 1, wherein the alkylene oxide is ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. In a tape drive system performing readwrite operations for a tape by inserting a tape cartridge into a tape drive, said tape cartridge having a tape on which servo and data tracks are arranged longitudinally and a predetermined servo pattern is recorded on each of said servo tracks, a method for stabilizing a servo system for said tape drive comprising the step of:
re-setting coefficients of a low-pass filter for servo control of said tape drive, each time said tape cartridge is inserted into said tape drive, in response to the characteristics of the inserted tape cartridge.
2. The method according to claim 1, further comprising the steps of:
reading a servo pattern recorded on the tape in said tape cartridge inserted into said tape drive;
performing a frequency analysis of said read servo pattern;
detecting, from frequency components obtained by said frequency analysis, a singularity that exceeds a predetermined spectrum range; and
setting said coefficients of said low-pass filter so as to cancel a power spectrum of said singularity.
3. The method according to claim 2, wherein said servo pattern consists of a pattern of repetitive magnetic transitions recorded in non-parallel directions, and said step for performing a frequency analysis of said servo pattern includes the steps of measuring intra-pattern and inter-pattern intervals in said repetitive pattern and performing a fast Fourier transform on the measured results.
4. The method according to claim 3, wherein said step for detecting a singularity includes the steps of setting multiple windows each having a predetermined frequency at its center, for data obtained by said fast Fourier transform, and detecting a singularity in each of said windows.
5. The method according to claim 4, wherein said step for detecting a singularity compares a median for all signal values in each of said windows with each of said signal values, and defines as said singularity a frequency of a signal value having a difference from said median which exceeds a predetermined threshold value.
6. The method according to one of claims 2 to 5, wherein said step for setting coefficients of a low-pass filter includes the steps of preparing multiple sets of filter coefficients in advance by simulation, and selecting a set of filter coefficients in accordance with said detected singularity.
7. A tape drive into which a tape cartridge is inserted, said tape cartridge having a tape on which servo and data tracks are arranged longitudinally and a predetermined servo pattern is recorded on each of said servo tracks, comprising:
servo control means including a low-pass filter for servo signals; and
means for re-setting coefficients of said low-pass filter each time a tape cartridge is inserted, in response to the characteristics of the inserted tape cartridge.
8. The tape drive according to claim 7, wherein said re-setting means comprises:
means for reading a servo pattern recorded on the tape in said tape cartridge inserted into said tape drive;
means for performing a frequency analysis of said servo pattern;
means for detecting, from frequency components obtained by said frequency analysis, a singularity that exceeds a predetermined spectrum range; and
means for setting said coefficients of said low-pass filter so as to cancel a power spectrum of said singularity.
9. The tape drive according to claim 8, wherein said servo pattern consists of a pattern of repetitive magnetic transitions recorded in non-parallel directions, and said means for performing a frequency analysis of said servo pattern includes means for measuring intra-pattern and inter-pattern intervals in said repetitive pattern and performing a fast Fourier transform on the measured results.
10. The tape drive according to claim 9, wherein said means for detecting a singularity includes means for setting multiple windows each having a predetermined frequency at its center, for data obtained by said fast Fourier transform, and detecting a singularity in each of said windows.
11. The tape drive according to claim 10, wherein said means for detecting a singularity compares a median for all signal values in each of said windows with each of said signal values, and defines as said singularity a frequency of a signal value having a difference from said median which exceeds a predetermined threshold value.
12. The tape drive according to one of claims 8 to 11, wherein said means for setting coefficients of said low-pass filter includes means for preparing multiple sets of filter coefficients in advance by simulation, and selecting a set of filter coefficients in accordance with said detected singularity.