1. Field of the Invention
The present invention relates to mortise locks, and particularly to an improved powerpack for mortise locks having a dual-independent return mechanism for inner and outer door operators, and a lockout feature.
2. Description of the Background
A mortise (or mortice) lock requires a pocket (the mortise) to be cut into the door to which the lock is to be fitted. Mortise locks are popular in commercial and upscale residential buildings in the United States due to their security and flexibility.
A typical mortise lock includes a lock body installed inside the mortise pocket, lock trim including various designs of faceplates, inner and outer “operators” which may be doorknobs, levers or other external operators, a latch bolt which is extendable out from the lock body to lock the door, a latch bolt driving assembly for translating torque from the latch bolt operators into linear motion of the latch bolt, a keyed cylinder journaled into the lock body to lock the latch bolt, and a strikeplate installed on the door frame with holes aligned to the bolt. Many mortise locks additionally include a locking deadbolt for more security. There are many variations, and indeed one of the primary advantages of mortise locks is that they accept a wide range of various manufacturers' cylinders, trim and accessories.
Most mortise locks are configured so that the inner operator mounted on the inside and the outer operator mounted on the outside of the door can operate independently. The outside operator can either be rotated to retract the latch bolt, or locked against rotation to prevent retraction of the latch bolt. Preferably, the inside operator can always be rotated to retract the latch bolt. The operators turn the latch bolt driving assembly rotary motion to linear retraction of the latch bolt, and a “powerpack” is used to return the operators to their rest position after being rotated to open the door. The locking of the outside operator (against rotation to prevent retraction of the latch bolt) is usually controlled by an actuator, such as, for example, a push button or a pivoted toggle, which is exposed at the edge of the mortise lock. The manual actuator selectively engages the spindle, latch bolt driving assembly or other component so as to prevent rotation from the outside. The inside latch knob or handle is usually unaffected by the actuator and remains rotatable at all times.
Conventional powerpacks are simple helical torsion springs, which can be included either inside the mortise lock body (internal) or as part of the operator (e.g., integral to the external operator), but not both. Since mortise locks are intended to accept a wide range of various manufacturers' trim including external operators, and since many manufacturers supply external operators with built-in powerpacks, mortise lock manufacturers have traditionally had to maintain two types of mortise locks in inventory, one with and one without the internal torsion spring. Moreover, helical torsion springs are themselves problematic, inasmuch as they are relatively weak, exert increasing torsion with turning, have a short fatigue life, and non-adjustable torsion coefficient. Mortise locks need to live up to their reputation as high-security locks, and this demands utmost durability.
It would be greatly advantageous to provide the mortise lock with a modular powerpack incorporating independent return mechanisms, one for the inside operator and one for the outside, each using linear springs so that the force deflecting the spring is in direct proportion to the distance the spring travels, both allowing adjustable torsion, and further including a lockout feature for selective “locking out” of the internal return mechanisms to accommodate external operators with built-in powerpacks.