Patent Application
20080179468
1. Field of the Invention
The present invention relates generally to model railroad switches and more particularly to a model railroad switch assembly, which employs a lead screw actuator driven by an electric motor.
2. Background Art
Historically, the actuators for implementing a track switch for redirecting miniature rolling stock comprise solenoid coils. Such coils are typically configured for moving a plunger, which is connected to the track switch through a linkage. Unfortunately, such solenoid coil based switches are not very good simulations because they move quickly in a pulse-like motion and not in a slow steady motion which would be much more realistic in its operation. In an effort to provide a more realistic deliberate and steady switching motion, prior art switch machines have been substituting an electric motor operated switch for a solenoid coil operated switch. One example of such a prior art electric motor type actuator is disclosed in U.S. Pat. No. 4,695,016 to Worack. The Worack actuator employs a high gear ratio electric motor to slowly move one end of an elongated pin or wire around a fulcrum point. The other end of the pin or wire is secured to the throw bar of the track switch. Unfortunately, the Worock actuator is too large and cumbersome to be located at the track switch. Instead, it is implemented beneath the support surface (i.e., table) on which the track is assembled. However, installing such actuators beneath the table so that each is perfectly aligned with the track switch to which the pin is connected, is a difficult and inconvenient task that can be described as backbreaking. Other electric motor operated track switch actuators, such as those disclosed in U.S. Pat. No. 5,752,678 to Riley and U.S. Pat. No. 6,308,920 to Zander, are designed to be installed on the track side of a table adjacent the track switch. However, they too are large bulky devices which detract from realistic simulation based upon their size and complexity.
Therefore, there is still an unresolved need for an electrical motor operated switch actuator which is sufficiently small to be mounted directly beneath a track switch, which has a slow smooth actuator motion and which does not detract from realism of simulated railroad appearance because it is essentially hidden from view and yet is installed above the table supporting a layout.
The present invention satisfies the aforementioned need by providing a track switch actuator which has the advantages of slow, smooth realistic operation, small package size that permits installation directly to the bottom of a track switch and unobtrusive, simple design which does not detract from realistic appearance. In fact, the preferred embodiment is sufficiently small to be marketed as a combination with the actuator assembly installed onto a track switch before the track switch is installed into the layout and is then essentially hidden from view.
In the preferred embodiment of the present invention, a small low voltage DC motor is installed into an elongated ABS plastic extrusion having an elongated radial opening. The motor shaft is affixed to a lead screw on which a threaded slider travels from one end to another depending on the direction of lead screw rotation. An actuator arm in the form of a nail-like projection, is soldered or otherwise firmly affixed to the slider exterior so that the projection travels with the slider along the lead screw with the projection extending perpendicularly from the lead screw. The free end of the projection extends into an aperture in the throw bar of the track switch for switching same with travel along the lead screw.
Thus, it will be seen hereinafter that the preferred embodiment of the present invention overcomes the noted deficiencies of the prior art with these advantageous features:
1) It obviates “under the table” installation which can be very inconvenient and backbreaking.
2) It is sufficiently small to be installed on the bottom of a track switch before the track switch is installed in a layout.
3) It can be readily sold in the marketplace in combination with the track switch and already attached thereto and operational therewith.
4) It is substantially invisible and therefore doesn't detract from simulated appearance in a railroad prototype.
The aforementioned objects and advantages of the present invention, as well as additional objects and advantages thereof, will be more fully understood herein after as a result of a detailed description of a preferred embodiment when taken in conjunction with the following drawings in which:
Referring to the accompanying figures, it will be seen that a track switch actuator assembly 10 is mounted directly to the bottom of a track switch 12 in a model train layout 21 on which there is at least one model train 14. The actuator assembly 10 is preferably hidden in or partially obscured by a simulated track bed 16 as shown best in
The actuator assembly 10 is affixed to the track switch immediately below a throw bar 15 which has at least one aperture 17 (see
The illustrated embodiment of the actuator assembly 10 comprises an extruded plastic housing 22, a cylindrical DC motor 24 having a shaft 25, a lead screw 26 axially attached to said shaft, a rubber tube 28, a hex nut 30, a slider 32 threadably engaged on said lead screw, a bushing/bearing 34, and an end cap 36. The housing holds the motor, lead screw, slider and other components and is preferably glued or otherwise affixed to the bottom surface of track switch 12. Hex nut 30 is permanently affixed to the open end of lead screw 26 and provides a means of frictional engagement with the interior of tube 28. End cap 36 is secured at the head end of lead screw 26 and provides an axle-like support for bushing/bearing 34. Also included in the actuator assembly 10 is an actuator arm 38, which is affixed by soldering, gluing or the like, to a flat surface of slider 32. Arm 38 is positioned to extend perpendicularly from the slider 32 which, in turn, is threadably mounted onto lead screw 26 so that upon rotation of shaft 25 by motor 24, the slider and actuator will travel along the lead screw 26 in a direction dependent upon the direction of rotation of the shaft as depicted in
The housing has an elongated opening 23, which permits movement of the extended actuator arm 38 with slider 32 with rotation of the lead screw 26, so that the arm can cause full activation of the track switch 12. As shown best in
Those having skill in the model railroading art will now understand that the present invention provides a uniquely advantageous track switch actuating assembly. It will also be apparent that while a preferred embodiment of the invention has been disclosed in sufficient detail to enable fabrication and use thereof, various modifications may be made without deviating from the inventive features described herein. Accordingly, the scope hereof is to be limited only by the appended claims and their equivalents.
