Extensible rod

The telescoping elements of an extensible rod may be coupled sequentially to a coaxial, partly threaded spindle by respective internally threaded coupling members, each element being drivingly engaged with the spindle by a previously engaged, abuttingly coupled element. A yieldably resilient mounting for the coupling member or for one of two cooperating abutment members permits smooth engagement of the spindle threads with the coupling members.

This invention relates to extensible rods, and particularly to a rod whose 
length may be varied under remote control. 
The term "rod", as employed herein, will be understood broadly to designate 
an elongated structural member of adequate strength to retain its shape 
under the stresses for which it is intended. An extensible rod may 
constitute the radio antenna of a motor vehicle or an arm of a remotely 
controlled manipulator, and many other applications will readily suggest 
themselves. 
It is a primary object to this invention to provide an extensible rod which 
may be collapsed to a small fraction of its extended length and is rigid 
when extended, yet of relatively low weight. 
With these and other objects in view, as will become apparent hereinafter, 
the extensible rod of the invention is equipped with a motor-driven, 
partly threaded drive spindle and includes a plurality of rod elements 
elongated in the direction of the spindle axis. Engaged guides on the 
elements guide relative, axial element movement. First couplings 
associated with respective elements sequentially couple the elements to 
the spindle and thereby move each element axially in response to the 
rotation of the spindle. The first coupling device includes an internally 
threaded coupling member matingly engageable by the threads of the 
spindle. A second coupling device can couple each element, while coupled 
to the spindle threads, to another element for joint axial movement until 
the coupling member associated with the other element is engaged by the 
threads. One of the coupling devices includes a yieldably resilient 
component which permits limited axial movement of the coupling member 
associated with the other element relative to the element already coupled 
to the spindle threads during joint axial movement of the two elements.

Referring to the drawing in detail, there is shown as much of the arm of a 
remotely controlled manipulator as is needed for an understanding of the 
invention. The arm is mounted on a housing 1 in which a reversible 
electric motor 2 is mounted in a conventional manner, not specifically 
illustrated, on a speed-reducing gear transmission 3 which connects the 
obsecured output shaft of the motor 2 to a coaxial spindle 4. The spindle 
passes through an opening in an end plate 5 of the housing carrying the 
transmission and serves as a pivot for a carrier plate 6 rotatably 
supported on the end plate 5. A gear rim 7 on the carrier plate 6 is 
drivingly engaged by a pinion 8 journaled in the housing 1 an driven by a 
non-illustrated motor. The output shafts of both motors are equipped with 
selsyn generators 9 whose output signals set remote instruments indicating 
the angular positions of the spindle 4 and of the carrier plate 6, only 
the generator on the motor 2 being shown. 
Four tubes 10, 11, 12, 13, coaxial with the spindle 4, are mounted on the 
carrier plate 6. The bottom end of the outermost tube 10 is fastened to 
the carrier plate 6 by a flange 14. The top ends of the tubes 10, 11, 12 
carry respective upper guide rings 15, 16, 17 which project radially 
outward and inward of the tubes. The non-illustrated top end of the 
innermost tube 13 may carry an instrument or a tool not directly relevant 
to this invention and not shown. 
The rings 15, 16, 17 slidably engage the outer cylindrical faces of the 
tubes 11, 12, 13 respectively and thereby guide the tubes for coaxial 
relative movement. Each of several, circumferentially distributed, radial 
bores in each ring receives a spherical detent 18 and respective springs 
19, 20, 21 which differ in length as the associated rings differ in radial 
width, and differ in stiffness, the shortest springs 19 on the outermost 
tube 10 being stiffer than the springs 20 of the tube 11 which in turn are 
stiffer than the springs 21. Only one of the detents associated with each 
guide ring is shown in FIG. 2. Axial ribs 22 on the outer faces of the 
tubes 11, 12, 13 are received with minimal clearance in grooves of the 
rings 15, 16, 17 and prevent significant angular movement of the four 
tubes about their common axis. 
An abutment ring 23 is mounted at the lower end of each rib 22 near the 
bottom of each tube 11, 12, 13 by means of a radial flange 24 and 
circumferentially distributed, helical springs 25 covered by the abutment 
ring 23. The flange 24 and springs 25 permit, but resiliently resist, 
limited axial movement of the ring 23 on the associated tube. The radially 
extending abutment faces of the ring 23 converge in an outward direction 
so that the cross-sectional shape of the ring is trapezoidal. In the 
illustrated condition of the apparatus, the ring 23 on the innermost tube 
13 abuttingly engages a conforming face of the ring 17 while the detent 18 
on the tube 12 is received in a lower recess 26 of the tube 13. The 
detents 18 mounted on the tubes 10, 11 may be received in respective upper 
recesses 27 provided in the outer faces of the tubes 11, 12 near the guide 
rings 16, 17 to hold the rings 15, 16, 17 and the associated tubes in the 
respective rest positions illustrated in FIG. 2. 
The lower ends of the tubes 11, 12, 13 carry respective lower guide rings 
28 which slidably engage the inner faces of the tubes 10, 11, 12. Each 
lower guide ring 28 movably retains the outer circumference of a normally 
flat, annular spring steel diaphragm 29 whose inner circumference is 
similarly retained in a circumferential groove of a nut 30. The free end 
of the spindle 4 carries threads 31. The portion 32 of the spindle 4 
adjacent the carrier plate 6 is free from threads and of smoothly 
cylindrical, reduced cross section over an exposed, axial length only 
slightly greater than the combined axial length of two nuts 30. In the 
position of the apparatus shown in FIG. 2, the nut 30 on the tube 13 is 
coupled to the spindle 4 by the threads 31 near the free end of the 
spindle 4 while the nuts 30 associated with the tubes 11, 12 freely 
receive the smooth spindle portion 32. 
When the motor 2 turns the spindle 4 in a direction to lift the tube 13 
from the illustrated position, the abutment ring 23 on the tube 13 and the 
guide ring 17 and detent 18 on the tube 12 couple the tubes 12, 13. The 
detent spring 20 on the tube 11 is overcome by the axial force transmitted 
from the spindle 4 to the coupled tubes 12, 13, and the tube 12 moves 
jointly with the tube 13 (FIG. 1) until the angularly fixed nut 30 on the 
tube 12 engages the lowermost turn of the threads 31 on the rotating 
spindle 4. In the event of an angular mismatch of the internal threads in 
the nut 30 on the tube 12 with the threads 31, the diaphragm 29 on the 
tube 12 and/or the springs 25 in the abutment ring 23 of the tube 13 yield 
to permit relative axail movement of the nut 30 relative to the driving 
tube 13 until the rotating threads 31 can engage the nut on the tube 12. 
The tube 11 is retained in the illustrated rest position by the detent 
spring 19 on the tube 10. 
For a few revolutions of the spindle 14, both tubes 12, 13 are driven by 
the spindle. The nut on the tube 13 then slips from the top of the 
spindle, and the tube 13 thereafter is moved axially by the detent 18 on 
the tube 12. The spring 21 is chosen stiff enough to prevent release of 
the associated detent 18 from the tube 13 under the weight of the tube and 
of any nonillustrated devices which it may carry. 
Unless the motor 2 is stopped first by remote control, the abutment ring 23 
on the tube 12 abuttingly engages the upper guide ring 16 on the tube 11, 
the detent 18 of the latter drops into the lower recess 26 in the tube 12, 
and the nut 30 on the tube 11 is lifted into engagement with the threads 
31 shortly before the tube 12 is disengaged from the top of the spindle 
14. When subsequently the tube 11 is lifted from the illustrated position, 
its abutment ring 23 ultimately engages the upper guide ring 15 on the 
axially fixed tube 10 while the spings 19 on the latter drive detents 18 
into lower recesses 26 on the tube 11. 
A limit switch 33 on the outermost tube 10 is simultaneously engaged by the 
lower guide ring 28 of the tube 11 and deenergizes the motor 2 in a 
conventional manner, not shown, in the fully extended position of the 
manipulator arm. To guard against malfunctioning of the limit switch 33, 
the transmission 3 is provided with an overload-preventing, slipping 
clutch, conventional in itself and not specificlly illustrated. The nut 30 
of the tube 11 remains engaged by the threads 31 when the rotation of the 
spindle 4 is terminated by the limit switch 33. A notch (not shown) in the 
abutment ring 23 on the tube 11 permits the ring to travel axially over 
the switch 33 without tripping the same. 
When the motor 2 is energized to rotate in a direction to retract the 
manipulator arm toward its fully collapsed or retracted position, the tube 
11 is moved toward the carrier plate 6, and the rotating spindle 4 
overcomes the restraint of the spring 19 to release the associated detent 
18. The lower guide ring 28 on the tube 11 releases the limit switch 33 
which does not respond to the downward movement and does not prevent the 
reversed rotation of the motor 7. The tubes 11, 12, 13 move jointly inward 
of the tube 10, until the nut 30 on the tube 11 is released by the threads 
31 on the spindle 4 shortly after the nut on the tube 12 is engaged by the 
threads. Ultimately, the tubes 11, 12, 13 are fully retracted and 
releasably retained in their retracted positions by detents 18 engaging 
respective upper recesses 27. The motor 2 is stopped in a manner not 
specifically shown by a relay actuated by the selsyn generator 9 in 
response to the return of the spindle 4 to its rest position. 
In that position, the nuts 30 on the tubes 11, 12 loosely envelop the 
smooth portion 32 of the spindle 4 while the nut on the innermost tube 13 
remains engaged by the threads 31 so that the spring 21, and only the 
spring 21, will be compressed to release the associated detent 18 and the 
tube 13, when the motor 2 is again energized. 
The carrier plate 6 and the tube 10, 11, 12, 13 may be turned jointly 
relative to the spindle 4 by the pinion 8 through an angle necessary for 
the operation of the nonillustrated device attached to the innermost tube 
13 in all axial positions of the tube. 
The manipulator arm of the invention has been shown to have four coaxially 
telescoping, tubular elements in order not to crowd the drawing, but will 
be understood to be operable in an obvious manner with more or fewer 
elements. While the nuts 30 have been shown mounted on resilient 
diaphragms 29 for smooth engagement with the threads 31 on the spindle 4, 
the diaphragms may be replaced by rigid spiders if the springs 25 permit 
adequate axial movement of the abutment rings 23 on the associated tubes. 
Conversely, the abutment rings 23 may be fixedly mounted on the 
corresponding tubular elements of the manipulator arm if the diaphragm 29 
may be deflected axially by the axial spacing of two successive turns of 
the threads 31. 
Other variations in the illustrated embodiment of the invention will 
readily suggest themselves to those skilled in the art. It should be 
understood, therefore, that the foregoing disclosure relates only to a 
preferred embodiment of the invention, and that it is intended to cover 
all changes and modifications of the example of the invention herein 
chosen for the purpose of the disclosure which do not constitute 
departures from the spirit and scope of te appended claims.