Patent Grant
7071428
1. Field of the Invention
The invention relates to products having operator-access covers which protect operators from dangerous machine elements (rotating hardware, moving parts, etc.) but which need to be regularly opened by operators for service access and maintenance.
2. Background Art
The use of an interlock actuator for an operator-access cover is required in certain applications. Such operator-access covers are required, as a matter of product design requirements and/or regulatory standards, to incorporate some automatic interlock feature which will de-energize any dangerous machine element when the cover is opened and render the exposed parts of the machine safe for operator access. Such interlock function is usually provided by an electrical switch or switches, which break the supply of electrical power to the exposed machinery and/or send a signal to the controlware of the machine, which in turn breaks the power supply and/or otherwise renders the machinery safe.
Such electrical switches are typically highly regulated as to type and construction by the regulatory agencies who specify interlock functions and certify compliance. Switches, for example, must typically be double-pole, of approved construction and contact separation, non-defeatable without the use of special tools (incapable of being “cheated”) and self-resetting when overridden for service. One consequence of these regulatory requirements is that such switches typically have a very narrow range of motion in which they are guaranteed to operate. For example, a plunger switch may have a range of plunger motion in which the maker guarantees correct closed contact configuration of +/−0.015 inches.
Such operator-access covers are typically hinged to open and close. Workers in the art are aware of the great difficulty of mounting and configuring such switches to ensure reliable operation (given their narrow operating range) while still making covers, hinge systems and the like within normal manufacturing tolerances. It is very easy for normal manufacturing tolerances to accumulate through the various parts of the cover, hinges and switch mounts to the point where the operating range of the switch is exceeded by the possible range of tolerances in the various parts. For this reason, switches are often actuated through a separate adjustable actuator, which can be adjusted to compensate for tolerance accumulation.
Leaving aside the added cost, such adjustable actuators are less-than-desirable because it is virtually impossible to ensure that they are adjusted to actuate the switch fully. In other words, the actuator may be adjusted so that the switch is seen to work correctly (as tested by electrical measurement, for example) but there is no practical way to tell whether the switch is at one limit or the other of its operating range, and liable to fail at any time due to part variation, vibration or the slightest change in the intervening parts. Another problem is that of over-travel—where the actuator is adjusted so that it over-actuates the switch, causing unacceptable pressures on the switch assembly and poor fit or closure of the cover. Such switches and adjustable actuators are a continual source of service attention and unplanned downtime.
For the foregoing reasons, there is a need for an improved interlock actuator for a hinged cover.
It is an object of the invention to provide a self-adjusting interlock actuator for a hinged cover. In preferred embodiments of the invention, a hinged operator-access cover provides a self-adjusting actuator function which will always operate an interlock switch correctly and provides automatic force and travel limit functions which ensure that the switch is never over-actuated. Further, in preferred embodiments, these functions are provided in a way that is completely independent of variations in cover and hinge parts.
The invention involves a self-adjusting interlock actuator for a hinged cover. Such hinged covers are often used as operator-access covers which protect operators from dangerous machine elements but need to be regularly opened by operators for service and maintenance purposes. One place where such hinged covers are used is in document processing systems.
The self-adjusting interlock actuator assembly includes a cover hinge that attaches to the cover and defines a hinge axis. A pivoting switch actuator rotates, preferably on the same axis as the hinge axis, and is driven by the cover hinge via compliant spring means. The spring means provides adequate actuating force to actuate the interlock switch with the switch actuator when the cover is closed. It is preferred to configure the spring means such that the force on the switch cannot exceed a maximum permissible force regardless of cover position or manipulation.
Put another way, the cover hinge is rotated as the cover is rotated. The pivoting switch actuator rotates and is driven by a spring means connected to the cover hinge. In this way, the pivoting switch actuator is indirectly driven as opposed to being strictly fixed to the cover hinge. This indirect drive approach ensures that the interlock switch is operated correctly independent of variations in hinge and cover parts.
It is appreciated that the invention at the more detailed level comprehends additional features that are implemented in preferred embodiments of the invention. One such feature is a limit stop mechanism incorporated into the assembly which ensures that the switch can never be over-actuated regardless of cover or hinge position. Another such feature is to arrange the assembly such that the interconnection between the pivoting cover and pivoting switch actuator ensures that the switch opens before the cover is opened far enough to exceed regulatory limits, regardless of variations in cover and hinge parts, and that the cover always closes fully and completely regardless of variations in actuator or switch parts.
It is appreciated that in embodiments of the invention, self-adjusting interlock actuator assemblies may take many forms. The cover hinge, switch actuator and spring means may be implemented in various ways depending on the application provided that in the assembly, the pivoting switch actuator is indirectly driven via the spring means as the cover hinge is rotated.
Further, it is to be appreciated that it is preferred that the pivoting switch actuator rotates on the same axis as the hinge axis. However, in an alternative embodiment, it would be possible to have the pivoting switch actuator rotate about an axis that is offset from the hinge axis. Accordingly, the limit stop mechanism would need to be configured appropriately to accommodate the translation motion in addition to the rotation motion of the switch actuator with respect to the cover hinge.
The parts pivot about pin 24 which is secured by clips 26 and 28. Switch actuator 16 includes flange 30 to which one end of spring 18 is affixed. Pin 32 is secured to cover hinge 12, and extends through slot 33 in switch actuator 16. The other end of spring 18 is affixed to pin 32. Spring 18 is under tension when affixed between flange 30 and pin 32. In this way, spring 18 biases switch actuator 16 in the cover closing direction.
In
When the cover is closed, pivoting switch actuator 16 is driven by cover hinge 12 via spring 18 to actuate the interlock switch with end 34 of switch actuator 16 when the cover is closed. More specifically, rotating cover hinge 12 about hinge axis 14 causes pivoting switch actuator 16 to rotate about axis 14, thereby causing pivoting switch actuator 16 to actuate the interlock switch with end 34. Also shown, redundant switch element 50 may be provided such that element 50 engages a mating element when the cover is closed, providing an additional switch that indicates when the cover is closed.
As shown in
With continuing reference to
In accordance with the invention, system 51 may have any number of hinged operator-access covers which protect operators from machine elements and cooperate with an interlock switch to disable machine elements when the cover is opened. Assembly 10 may be utilized at any of these covers. For example, various processing devices along the document track may include covers where a self-adjusting interlock actuator assembly 10 may be incorporated.
While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3430011 | Skelton | Feb 1969 | A |
| 3453613 | Kay | Jul 1969 | A |
| 4262176 | Kapitza et al. | Apr 1981 | A |
| 5153395 | Schantz et al. | Oct 1992 | A |
| 5691520 | Hapke et al. | Nov 1997 | A |
| 5726402 | Katz et al. | Mar 1998 | A |
| 6118090 | Osvatic et al. | Sep 2000 | A |
| 6653581 | Bassi | Nov 2003 | B1 |
