Flexible or portable closure – partition – or panel – Roll type – With brake or stop
Reexamination Certificate
1999-07-26
2001-12-18
Lev, Bruce A. (Department: 3634)
Flexible or portable closure, partition, or panel
Roll type
With brake or stop
C160S191000, C160S170000
Reexamination Certificate
active
06330903
ABSTRACT:
BACKGROUND OF THE INVENTION
Window shades and blinds have been provided with various mechanisms to facilitate lifting. Among the roller shade mechanisms are the common spring loaded shade roller, shade rollers which are operated by chain wheels, inverted shades with rollers at the bottom, and shade rollers with internal motors. Blind mechanisms include the common venetian models and others mostly distinguished by the type of blind rather than the lifting method.
Of the above, only the common shade roller provides a means to balance the weight to be lifted and, even so, the shade must be overbalanced for proper operation of the mechanism. Furthermore, there is no arrangement to provide consistency in the balancing force versus the changing load of the shade as it is rolled up. This is apparent to anyone who has ever let go of a window shade without first setting the latching mechanism and has watched the shade abruptly snap upwards.
This invention uniquely provides a variable balancing force to track the changing load as a shade or blind is lifted. The mechanism is useful for shades, where the load decreases as the shade is lifted, and for blinds or inverted shades, where the load increases as the blind is lifted. The mechanism is also useful for other applications requiring constant balance of moving loads, particularly where space for the lifting mechanism is limited.
OUTLINE OF THE INVENTION
In the invention, constant balance is maintained by providing a lifting force, preferably from a spring, through a mediating mechanism comprising a variable pitch screw arrangement such that the mechanical advantage of the mediating mechanism changes to allow the continuously decreasing spring force to apply an appropriate lifting force at all times. Where the required lifting force can be matched by the spring constant, the pitch variability is zero and the screw pitch is constant.
The variable pitch screw preferably takes the form of a twisted bar. Methods to manufacture the bar are disclosed. Although the twisted bar is preferred, it will be obvious to one skilled in the art that there are other useful screw forms, each of which has an appropriate form for its nut or follower. For example, the screw may be a pair of (constant or variable) helixes (helices), offset 180 degrees from each other, milled into a cylindrical bar. In that case the nut preferably engages the screw with a pair of opposed pins.
Achieving constant balance allows the use of various actuators which were not previously practical. The mechanism can be overdriven to allow short throw levers, cords, or chains that, in a non-balanced system would require excessive force to operate. The bottom bar of a shade or blind can be directly pulled down or lifted by hand and will remain where it is released. The need for latches, clutches, or cleats is eliminated. Motorized embodiments can take advantage of the reduced operating force to use smaller and quieter motors. Motors for systems comprising the invention may be battery operated, particularly using solar cells (which collect light from the window being shaded) to recharge the batteries.
Friction in these systems tends to act equally in both directions and so is not usually taken into account in the design process. In some cases it may be useful to overbalance in one direction or the other so that friction is overcome for that direction of operation. This concept comes into play for ,e.g., instances of direct manual operation of a shade or blind. It is easier to pull down than to lift so the system may be overbalanced to favor lifting. Thus the force to overcome friction is added primarily to the pull down direction of operation.
The invention is, however, not limited to window blind and shade mechanisms, but is intended for use in any application requiring constant balance of a predictable, variable load. Such applications include projection screens, security gates, garage doors, tailgates, and piano lids. There are also uses that can benefit from the invention even where the variable load may be only roughly predicted. Such uses include automobile hoods or awnings which may carry snow as unpredictable added loads. The invention also is intended for applications comprising only constant loads, but where physical constraints do not allow for counterweights.
In some uses (see
FIG. 1
) the cup or follower is the more active member, in others (see
FIG. 2
) the twisted bar is the more active member.
In some uses (see
FIG. 1
) the load may be directly connected to the mechanism, in others (see
FIG. 3
) an intermediate actuator may be used.
In some uses (see
FIG. 1
) the load decreases as it is raised, in others (see
FIG. 2
) the load increases as it is raised, in others the load variation may change sign as the load is raised or the load may be constant.
In some uses (see
FIG. 1
) the load varies non-linearly with respect to the rotation angle between the screw and follower, in others (see
FIG. 2
) the load varies linearly.
In some uses (see
FIG. 1
) there are compression springs, in others (see
FIG. 2
) extension springs.
It is also useful in some applications to apply the driving force to rotate one component (preferably the screw) of the screw-follower set which then balances a load connected to the translating component (preferably the follower).
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