US3628113A

US3628113A - Controlled caging and uncaging mechanism

Info

Publication number: US3628113A
Application number: US41431A
Authority: US
Inventors: Robert M Steudl
Original assignee: National Aeronautics and Space Administration NASA
Current assignee: National Aeronautics and Space Administration NASA
Priority date: 1970-05-28
Filing date: 1970-05-28
Publication date: 1971-12-14
Anticipated expiration: 1988-12-14

Abstract

A positioning mechanism intended for remote locking and releasing of instruments having a geared down motor driving a cam, the direction and duration of motor rotation being controlled by a circular printed circuit mounted for rotation on the cam shaft, the printed circuit cooperating with a plurality of wiper contacts to effect reversal of polarity in the motor to prevent overtravel thereof.

Description

United States Patent represented by the Administrator of the National Aeronautics and Space Administration CONTROLLED CAGING AND UNCAGING MECHANISM Primary Examiner-Lewis H. Myers Assistant ExaminerH. Huberfeld Attorneys-R. F. Kempf, E. Levy and John R. Manning ABSTRACT: A positioning mechanism intended for remote 2Clalrns,6Drawlng Figs. locking and releasing of instruments having a geared down motor driving a cam, the direction and duration of motor rotac 12 4/ 3 tion being controlled by a circular printed circuit mounted for I CI rotation on the cam shaft, the printed circuit cooperating with ui g 26 a plurality ofwiper contacts to effect reversal of polarity in the o motor to prevent overtravel thereof.

IIII I 1 I I II I2 L I 24" w 2 i E I I BA I I 32 I6 I 33 I 9 IILI I I l I I Patented Dec. 14, 1971 2 Sheets-Sheet 2 ML ED w WT S M W Du BY 4M Liz/J ATTORNEYS used by-or for the United States Government for Governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION This invention relates to a mechanism for automatically locking and unlocking instruments where the actuated mechanism weight is small in relation to the locking force required.

In the past, systems have been designed to actuate and/or shut down mechanisms in response to a signal from a remote point such as instruments used in lunar landings. These systems have taken the form of bulky mechanical arrangements coupled with the necessary electrical circuitry to actuate them or a pneumatic device using an explosive actuator arrangement which utilizes the force of a small explosion to lock or unlock the instrument.

The disadvantages of such prior systems are numerous. They are incapable of being cycled automatically and require replacement of parts. The explosive-type system has the inherent drawback of transmitting a significant amount of shock to the device being actuated. If a gas is used to impart an explosive-type force, the system may experience gas leakage. Also, the explosive actuator has to be placed at some distance from the instrument to minimize the shock.

The electromechanical systems do not meet the weight or capability requirements needed under the general parameters of this invention.

It is these past problems, especially in activation and deactivation of instruments used in lunar landings that led to the development of the present invention.

GENERAL DESCRIPTION This invention utilizes a motor to drive a cam and gear mechanism, which cam actuates a plunger or other directional force transmitting means to lock or unlock an instrument. A disc having a printed circuit thereon is utilized in conjunction with a plurality of biased contacts to automatically stop the motor in predetermined lock and unlock positions in regard to plunger disposition. A switch, which can be actuated by suita ble electronics upon receiving a remote signal, activates the motor which is preferably geared down. A worm gear and worm wheel are usedto transmit motor rotation to rotation of a shaft carrying the cam and printed circuit disc. The design of the printed circuit is such that the motor circuit is broken when the plunger reaches a predetermined position. The design of the disc printed circuit also sets up the circuit for motor reversal upon reactivation ofthe switch.

The invention can be applied to lock and unlock, position, or drive, with controlled velocity. items in hazardous environments where space or weight are extremely limited.

OBJECTS OF THE INVENTION Accordingly it is an object of this invention to provide an automatic locking and unlocking device.

A further object of this invention is to provide an automatic locking and unlocking mechanism that can be cycled continuously.

A still further object of this invention is to provide an automatic positioning mechanism that can be tested without necessitating replacement of any parts.

A further object of this invention is to provide an automatic positioning mechanism having a shock-free operation and readily adjustable in the test area.

A further object of this invention is to provide an automatic positioning mechanism which includes a motor driving a disc which has a printed circuit thereon engaging biased contact arms and adapted to automatically stop rotation of the motor and set up the circuitry for reversal of the motor.

These and other objects will become apparent during the following description taken with reference to the drawings in which:

FIG. 1 is a front view of the positioning mechanism showing it functioning with a lunar seismometer.

FIG. 2 is a plan view of the device shown in FIG. 1 with the seismometer apparatus removed.

FIG. 3 is a front view of the position mechanism in a slightly difierent seismometer housing and showing the biased contact arms.

FIG. 4 is a partial side view of the mechanism of FIG. 3 showing the motor and worm gear arrangement.

FIG. 5 is a partial perspective of the positioning mechanism showing the printed circuit disc and the relationship between the printed circuit and the biased contact arms.

FIG. 6 is an electrical circuit diagram of the positioning mechanism.

Referring now to FIG. I, there is shown a seismometer cage 2 consisting of base plate 4, a guide plate 6 and a top plate 8. Plate 4, as shown in FIG. 2, is generally the shape of an equilateral triangle with a generally square portion 5 extending therefrom.

Securing top plate 8 to guide plate 6 are elongated spacers l0, 12 which are internally threaded at one end to receive threaded studs such as 18 which are mounted in guide plate 6. Screws 20 lock the top plate to the elongated spacers 10, I2. Securing guide plate 6 and base plate 4 are connected together in the same manner by

short spacers

14, 16; it being understood that there is another elongated spacer and short spacer not visible in FIG. 1.

Positioned within the cage, provided by the elongated spacers, is a seismometer mass 22 which is suspended by a wire 23 to a mass suspension arm (not shown). The numerous details of the seismometer are not shown since the seismometer forms no part of this invention. The cage and mass of the seismometer are only shown to demonstrate the relationship ofone instrument to the positioning mechanism.

The base of mass 22 is countersunk as at 24 to receive the tapered end ofa plunger 26 which is mounted for vertical sliding movement in guide plate 6.

On base plate 4, there are secured two

shaft mounting brackets

28 and 30, each bored to receive shaft 32. Mounted on shaft 32 intermediate the brackets is a cam 34 held in position on the shaft, below and in contact with plunger 26, by a setscrew 31 passing through an annular section 35 of the cam as shown in FIG. 2. A locking member 33 is secured to one end of the shaft and is held there by a screw similar to 31. A nonconductive disc 36 is mounted on the shaft by a set screw passing through an annular section 37 thereof. A printed circuit 39 is provided on the end face of disc 36. The disc 36 and locking member 33 preclude longitudinal movement of shaft 32.

A gear 38 is mounted on shaft 32 and is positioned to engage a worm 40 mounted'on the shaft 42 of a motor 44.

Motor 44, as seen in FIGS. 3 and 4, is held within a circular bracket 46 having

extension ears

48 and 50. Base plate 4 has a mounting flange 53, and the extension ears of the bracket 46 are mounted thereto by a pair of screws 52 and nuts 54.

Also mounted on base plate 4, by any suitable means (not shown), is a nonconductive plate 45. As seen in FIGS. 3 and 5, a series of biased contact arms FIG. 62, 64 and 66 are mounted thereto and are adapted to resiliently engage the printed circuit 39 on disc 36. The configuration of the arms may be as shown in FIG. 5 where, in the case of arm 60, it has a portion 61 bent at right angles to the portion secured to the plate 45 and a further portion 63 bent atapproximately right angles to portion 61. A more preferred form is illustrated in FIG. 2 in the case of arm 60', where the portion 63' is offset from portion 61' by approximately 45 and has a lip 65'. The juncture of lip 65' and portion 63' engage the printed circuit 39.

Referring now to FIGS. 5 and 6, the printed circuit 39 on disc 36 is seen to have an outer closed loop which connects with an inner open loop 72 by radial portion 71.

Loops

70 and 72 and portion 71 constitute one circuit designated as X. Positioned between

loops

70 and 72 is an open loop 74 which connects with a smaller inner closed loop 76 through a radial portion 75.

Loops

74 and 76 and portion 75 constitute a second circuit designated as Y. As shown in FIG. 6, contact 60 engages loop 70, contact 62 engages loop 74, contact 64 engages loop 72 and contact 66 engages loop 76. Le,

contacts

60 and 64 engage circuit X and

contacts

62 and 66 engage circuit Y.

Contacts

60 and 66 are connected to

battery sources

82 and 84, respectively; they are also connected to opposite poles of the batteries.

The opposite poles of the batteries are connected to motor 44 which, in turn, is connected with a switch 80, a double throw type of switch.

Contacts

62 and 64 are connected to the switch 80.

OPERATION OF THE MECHANISM When the switch 80 is moved, by any suitable means, such as by hand or by a relay (not shown) energized by a remote signal. to an up position, as viewed in FIG. 6 by a dash line, the electrical circuit is completed in circuit X through

loops

70 and 72 and radial portion 71. This energizes motor 44 which turns shaft 32 to rotate cam 34. If the plunger 26 is already in a locking position, rotation of cam 34 releases plunger 26 and unlocks mass 22. The plunger 29 may be spring biased downwardly if desired. When the gap 90, between the end of loop 72 and radial portion 75, reaches contact 64, the circuit X is broken and the motor is stopped. if the shaft 32 overtravels, the wiper contact 64 on loop 74 touches the radial portion 75 (assuming clockwise rotation as viewed in FIG. 6) between

loops

74 and 76, thus reversing the polarity to the motor. This reversing action negates the motor overtravel and stops the movement with wiper contact 64 in the gap 90 between the end of loop 72 and radial portion 75.

Reverse movement, to lock or unlock, depending upon the original condition is accomplished by moving the single pole double throw switch 80 to the down position to energize circuit Y to drive the motor 44 counterclockwise. When the gap 92, between the end of loop 74 and radial portion 71, reaches wiper contact 62, the circuit Y is opened, thus locking the plunger in place. Overtravel of the shaft 32 is prevented by polarity reversal when the contact 62 contacts radial portion 71

bridging loops

70 and 72.

The cam 34 may be adjusted to any suitable position by loosening setscrew 31 and manually rotating the cam on shaft 32.

It is seen that overtravel is prevented by the reversal of polarity thereby reversing the direction of rotation of the motor to effect an open circuit. The position of the disc is set up for a counter rotation the original direction of rotation, by repositioning the movable contact arm of switch 80.

The motor is preferably a DC motor which is internally geared down from 16,700 rpm. to 283 rpm. to provide 5.5 ounce-inches of torque. The external worm gear reduction is on the order of 37: I.

it is apparent that the positioning mechanism has many other applications besides that of locking and unlocking a seismometer. It can be used to position other instruments where a highly reliable mechanism is desired when the requirements are that the system weight must be small with respect to the locking force involved. In the embodiment shown, the entire system weighs only 57 grams including a 23 gram motor and it provides over 200 pounds of locking force along the plunger axis.

The mechanism thus can be used in many other applications, too numerous to mention, where the requirements are such that conventional systems are too heavy or impart a shock to the device being positioned or locked. it is further apparent that many changes and modifications will be obvious to one skilled in the art without departing from the scope of the appended claims.

What is claimed is: 1. A mechanism for caging and uncaging an instrument comprising;

motor means;

motion translating means having a shaft with a cam attached thereto;

gear reduction means coupling said motor means to said shaft of said motion translating means;

plunger means operated by said cam to cooperate with said instrument to achieve caging and uncaging thereof; power source means;

planar circuit means operatively connected to said shaft of said motion translating means and adapted to rotate therewith, said planar circuit means comprising a disc having a printed circuit pattern on one face thereof formed of four concentric conductive loops including an outer closed loop, an inner closed loop and two middle loops located between the outer closed loop and the inner closed loop, said outer closed loop being connected to the innermost one of said two middle loops by a first radial conductive portion, said inner closed loop being connected to the outermost one of said two middle loops by a second radial conductive portion, the printed circuit pattern providing gaps in the outermost one of said middle loops and the innermost one of said middle loops;

four wiper contacts, each riding on a respective one of said four concentric conductive loops;

switch means;

second circuit means connecting said motor means, said power source means, said switch means and said four wiper contacts to form, in conjunction with said printed circuit pattern, two sub-circuits adapted to control the rotation of said motor means in opposite directions and to reverse the polarity of said motor means at a predetermined point in its rotation, in either direction, in accordance with the location of said gaps, the middle two wiper contacts of said four wiper contacts adapted to respectively engage said gaps to open the respective subcircuit to stop said motor means and to reverse polarity of said motor means if overtravel occurs, thereby permitting said cam to position said plunger to precisely cage and uncage said instrument.

2. A mechanism as in wiper 1 wherein said reduction gear means comprises a worm driven by said motor means and engaging gear means on said shaft; said power source means comprises two batteries; said switch means is a single pole double throw switch; and said second circuit means connects opposite poles of said batteries to said motor means and said motor means to the single pole of said switch, the other opposite poles of said batteries being connected respectively to said wiper contacts riding on the outer closed loop and the inner closed loop, the middle two of said four wiper contacts being connected to said switch, whereby actuation of said switch effects clockwise or counterclockwise rotation of said motor means depending upon the direction of throw of said switch.

Claims

1. A mechanism for caging and uncaging an instrument comprising; motor means; motion translating means having a shaft with a cam attached thereto; gear reduction means coupling said motor means to said shaft of said motion translating means; plunger means operated by said cam to cooperate with said instrument to achieve caging and uncaging thereof; power source means; planar circuit means operatively connected to said shaft of said motion translating means and adapted to rotate therewith, said planar circuit means comprising a disc having a printed circuit pattern on one face thereof formed of four concentric conductive loops including an outer closed loop, an inner closed loop and two middle loops located between the outer closed loop and the inner closed loop, said outer closed loop being connected to the innermost one of said two middle loops by a first radial conductive portion, said inner closed loop being connected to the outermost one of said two middle loops by a second radial conductive portion, the printed circuit pattern providing gaps in the outermost one of said middle loops and the innermost one of said middle loops; four wiper contacts, each riding on a respective one of said four concentric conductive loops; switch means; second circuit means connecting said motor means, said power source means, said switch means and said four wiper contacts to form, in conjunction with said printed circuit pattern, two sub-circuits adapted to control the rotation of said motor means in opposite directions and to reverse the polarity of said motor means at a predetermined point in its rotation, in either direction, in accordance with the location of said gaps, the middle two wiper contacts of said four wiper contacts adapted to respectively engage said gaps to open the respective sub-circuit to stop said motor means and to reverse polarity of said motor means if overtravel occurs, thereby permitting said cam to position said plunger to precisely cage and uncage said instrument.

2. A mechanism as in claim 1 wherein said reduction gear means comprises a worm driven by said motor means and engaging gear means on said shaft; said power source means comprises two batteries; said switch means is a single pole double throw switch; and said second circuit means connects opposite poles of said batteries to said motor means and said motor means to the single pole of said switch, the other opposite poles of said batteries being connected respectively to said wiper contacts riding on the outer closed loop and the inner closed loop, the middle two of said four wiper contacts being connected to said switch, whereby actuation of said switch effects clockwise or counterclockwise rotation of said motor means depending upon the direction of throw of said switch.