Key alignment system for keyed safety interlocks

A key alignment system for safety interlock switches uses alignment holes, and alignment pins to compensate for misalignment between a body assembly and a key assembly. The misalignment is often due to normal wear and tear or outright abuse of a gate or other movable member that should be safely interlocked. The key is fixed to a floating plate connected to a mounting plate by a suspension. The alignment pins and holes on or in a fixed alignment assembly and the floating plate can move the floating plate into a position such that the key enters the key hole. Some embodiments incorporate the fixed alignment assembly into the body assembly. The normal function of a keyed safety interlock wherein the key can be caught and held or released is preserved and enhanced by compensating for misalignment.

TECHNICAL FIELD

Embodiments relate to safety interlocks, trap and hold mechanisms. Embodiments also relate to electromechanical systems, electromechanical actuators, and solenoids. Embodiments further relate to self alignment and mechanical suspensions.

BACKGROUND OF THE INVENTION

Safety interlock switches are used in industrial settings to lock entryways or to cut machinery power unless a person takes a positive action such as pressing a button. For example, a gate can deny access to a mine shaft. The gate can automatically swing shut and lock when it is not held open by a person or object. This is a desirable feature because it denies access to the unwary and to the uninvited. Another example is that the access to a large press can be denied when the press is energized.

Gates can sag on their hinges because either the gate is too heavy or because something heavy, such as a person, hangs on the gate while it is open. Sagging gates often fail to close unless physically lifted. Sagging or misaligned gates can also be closed when an alignment mechanism compensates for the misalignment by lifting or shifting the entire gate, which can require great strength.

Current solutions require considerable force or strength for continued gate operation with the end result that misaligned gates are often left unlatched. Unlatched gates are merely inconvenient in some environments. In other environments, an unlatched gate is a safety hazard or a security breach. Systems and methods for easily latching misaligned gates are needed.

BRIEF SUMMARY

It is therefore an aspect of the embodiments that a safety interlock switch has a body assembly and a key assembly. The body assembly has a key hole and the key assembly has a key attached to a floating plate. A suspension connects the floating plate to a mounting plate. The suspension allows the floating plate to move in two dimensions relative to the mounting plate to compensate for misalignment such that the key can enter the keyhole.

It is also an aspect of the embodiments that alignment pins moving into alignment holes can cause the floating plate to shift and thereby align the key with the keyhole. The alignment pins can be fixed to the floating plate, body assembly, or a fixed alignment assembly. Alignment pins fixed to the floating plate enter into alignment holes in the body assembly or in the fixed alignment assembly. Alternatively, alignment holes in the floating plate can be entered by alignment pins connected to the body assembly or to the fixed alignment assembly.

DETAILED DESCRIPTION

The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof. In general, the figures are not to scale.

A key alignment system for safety interlock switches uses alignment holes, and alignment pins to compensate for misalignment between a body assembly and a key assembly. The misalignment is often due to normal wear and tear or outright abuse of a gate or other movable member that should be safely interlocked. The key is fixed to a floating plate connected to a mounting plate by a suspension. The alignment pins and holes on or in a fixed alignment assembly and the floating plate can move the floating plate into a position such that the key enters the key hole. Some embodiments incorporate the fixed alignment assembly into the body assembly. The normal function of a keyed safety interlock wherein the key can be caught and held or released is preserved and enhanced by compensating for misalignment.

FIG. 1illustrates a key alignment system for a keyed safety interlock switch100in accordance with aspects of the embodiments. A body assembly102can be attached to a frame101and a key assembly114can be attached to a gate112. Alignment pins108enter into alignment holes107when the gate112is shut against the frame101. Notice that the alignment pins108are illustrated as pointed and that the alignment holes107are illustrated as countersunk to facilitate the alignment pins108entering the alignment holes107when the gate112and frame101are misaligned.

The key assembly114has a mounting plate111attached to the gate while a suspension made of springs109allows the floating plate113to move in two dimensions relative to the mounting plate111. InFIG. 1, those two dimensions are left-right and in out (of the page) but not up down. Movement of the floating plate allows a key110attached to the floating plate113to enter into a key hole106in the body assembly102. A solenoid104can extend and retract a plunger105to trap and hold or to release the key. The solenoid can receive electrical power from wires103.

FIG. 2illustrates a floating plate113suspended from a mounting plate111by coil springs109on the sides in accordance with aspects of the embodiments.FIG. 2is a top view of the key assembly114ofFIG. 1. Four coil springs109comprise the suspension201. In this top view the floating plate can move up-down and left right but not into and out of the page. As such, the floating plate113can move in two directions relative to the mounting plate111and those two dimensions are coplanar with the page and perpendicular to the long axis of the alignment pins108.

FIG. 3illustrates a floating plate113suspended from a mounting plate111by coil springs301in the corners in accordance with aspects of the embodiments.FIG. 3illustrates a four spring suspension302very similar to that ofFIG. 2.

FIG. 4illustrates a floating plate113suspended from a mounting plate111by leaf springs401in accordance with aspects of the embodiments. The four leaf springs401form a leaf spring suspension402.

FIG. 5illustrates a body assembly501with attached fixed alignment assembly502in accordance with aspects of the embodiments. The fixed alignment assembly is the area of the body assembly501having alignment holes107.

FIG. 6illustrates a key alignment system600for a keyed safety interlock switch in accordance with aspects of the embodiments. The body assembly601has alignment pins605that can go into alignment holes608in the floating plate607. A suspension of coil springs606allows the floating plate to move within the mounting plate602. The floating plate607, however, is also captured by the mounting plate602in that the floating plate can not escape from the mounting plate602. Notice that the suspension could also use leaf springs.

FIG. 7illustrates a captured floating plate607suspended from a mounting plate602in accordance with aspects of the embodiments. The key assembly603ofFIG. 7is a top view of the key assembly603ofFIG. 6. The springs of the suspension can not be seen because the view is occluded by the mounting plate602.

FIG. 8illustrates a cut view of a captured floating plate607suspended from a mounting plate602by coil springs606in the corners in accordance with aspects of the embodiments. The key assembly603ofFIG. 8is a cut view and top view of the key assembly603ofFIGS. 6 and 7. The springs of the suspension can now be seen because the view is cut such that the suspension is not occluded by the mounting plate602.

FIG. 9illustrates a body assembly901with a separate fixed alignment assembly904in accordance with aspects of the embodiments. The body assembly901has the key hole902along with any internal mechanism such as a solenoid. The alignment assembly904has alignment holes903. Both the body assembly901and the alignment assembly904can be fixed to a frame or gate such that they do not move in relation to one another. A key assembly's floating plate can then use the fixed alignment assembly to align a key with the key hole902.

FIG. 10illustrates a high level state diagram of a fail open catch and release body assembly in accordance with aspects of the embodiments. Applying power1001puts the body assembly into the hold state1002. In the hold state1002, a key can enter the key hole, perhaps pushing past a solenoid plunger, but can not exit the key hole. In the catch key1003substate, no key is caught in the key hole, but any key pressed into the key hole will be caught. In the hold key1004substate a key is in the key hole and will not be released. When power is turned off1005the body assembly moves into the release state1006, perhaps by retracting a solenoid plunger. If a key had been captured, it is released1007. A key will not be caught while the body assembly is in the release state1006.

The state diagram ofFIG. 10is called “fail open” because when electrical power fails the system goes into the release state. A “fail closed” version would transition into the hold state when electrical power is removed from the system.

FIG. 11illustrates a high level state diagram of a fail closed catch and release body assembly in accordance with aspects of the embodiments. The difference betweenFIG. 11andFIG. 10is that the “Power Off” and “Power On” blocks have traded places. As such, applying power1102puts the body assembly into the release state1006whereas removing power1101puts it into the hold state1002.