Pickup arm assembly

A phonograph pickup arm assembly in which one end of the arm is fitted with a quick-connect socket for receiving a cartridge shell. The socket is slotted and the cartridge shell includes a pin for insertion into the slot. The socket includes a tapered surface and a nut cooperates with the tapered surface to force a resiliently deformable portion of the socket into tight engagement with an embraced portion of the cartridge shell.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to mounting devices for joining a 
cartridge shell to the free end of a pickup arm of a phonograph record 
player. 
2. Description of the Prior Art 
A typical phonograph pickup arm of the type intended for use with a plug-in 
cartridge shell is provided with a socket disposed at the free end of the 
pickup arm. A plug-like formation on the cartridge shell is held in the 
socket by a nut encircling the end of the pickup arm. Usually pin and slot 
or spline arrangements ensure that the shell will not rotate when the nut 
is turned and that the cartridge is vertically aligned. Unfortunately, 
such prior art arrangements do not provide sufficient rigidity so that the 
shell exhibits a resonant frequency of its own, rather than the shell and 
arm forming a mechanically united assembly with an overall resonant 
frequency. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide a coupling device for 
joining a cartridge holding shell to a phonograph pickup arm, whereby 
precise alignment of the cartridge shell is ensured. 
Another object of the present invention is to provide a coupling device for 
joining a cartridge holding shell to a pickup arm so that the rigidity of 
the coupling is enhanced, whereby misalignment or tilt of the cartridge 
shell is prevented. 
Another object of the present invention is to provide a phonograph pickup 
arm assembly in which the cartridge holding shell and arm form a 
mechanically united assembly to minimize or reduce a separate mechanical 
reasonance of the cartridge. 
A further object of the present invention is to provide resiliently 
deformable locking means for rigidly joining a phonograph cartridge to a 
pickup arm for angularly locating the cartridge with respect to the pickup 
arm and preventing misalignment and tilt with respect thereto. 
A still further object of the present invention is to provide a pickup arm 
assembly which is simply constructed, can be manufactured by mass 
production techniques, and is inexpensive. 
In accordance with the foregoing features there is provided a pickup arm 
assembly comprising a first hollow cylindrical member mounted on a pickup 
arm, said member having at least one radially disposed slit; a head shell 
having a plug to be inserted into said first hollow cylindrical member; a 
second cylindrical member disposed and longitudinally movable on said 
first cylindrical member; and locking means for reducing the diameter of 
said first cylindrical member in response to a longitudinal displacement 
of said second cylindrical member, whereby said plug is locked in said 
second cylindrical member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring initially to the prior art pickup arm assembly shown in FIG. 1, 
the outer portion or free end 3 of a pickup arm is indicated. Shell 1, 
containing a cartridge 18, includes a plug 2 from which a radially 
disposed pin 6 protrudes. The pickup arm 3 receives a hollow cylindrical 
member 5 which is longitudinally slotted as shown at 5a. The member 5 is 
provided with a flange 8. An insulating ferrule 11 is positioned within 
cylindrical member 5 and retains the usual spring loaded electrical 
contacts. A nut 9 bears against the flange 8 at one end and longitudinal 
movement is restricted by a washer 7 disposed between a shoulder 4'on the 
cylindrical member 5 and an outer edge of the pickup arm 3. The pin 6 
engages a thread formation 10 on the interior of the nut 9. The plug 2 is 
drawn into and held in the member 5 by the cooperation between the pin 6 
and the thread formation 10 when the nut is rotated. 
FIG. 2 shows a cross-section of the prior art pickup arm assembly shown in 
FIG. 1 taken along the lines II--II. The pin 6 of the plug 2 is shown 
extending through the slot 5a in member 5 and into a space between threads 
of the thread formation 10. 
The prior art device thus described lacks adequate rigidity, thereby 
permitting the shell to move upwardly to the position shown in chain-dot. 
The rigidity of such a device can only be improved through the adoption of 
unacceptably high manufacturing tolerances which restrict 
interchangeability of cartridge shells made by different manufacturers. 
Referring now to FIG. 3, a coupling device according to the present 
invention is shown having a shell 14 carrying a cartridge 18. Plug 17 is 
affixed to shell 14. A radially aligned pin 16 protrudes from the side of 
the plug 17. The end of a pickup arm 19 receives a socket member 20 which 
includes a radially aligned longitudinal slot 29 into which the pin 16 may 
slide. The socket member 20 is terminated with a flange 27 whose outer rim 
28 is tapered. 
A portion 25 of the outer cylindrical surface of the socket 20 is threaded 
to engage a corresponding internal thread formation on a nut 24. The outer 
end of the nut 24 has an internal taper corresponding to and abutting the 
taper on the rim 28 of the socket. A washer 31, disposed between the end 
of the arm 19 and the socket member 20, restricts longitudinal movement of 
the nut 24. 
In operation, the plug 17 with its pin 16 aligned with the slot 29 is 
pushed manually into the socket 20 and, simultaneously, the nut 24 is 
screwed outwardly until the tapered surface thereon abuts the 
corresponding tapered surface 28 on the socket. This action provides an 
inwardly directed thrust as shown by arrow 24b which rigidly joins the 
shell to the arm. 
Referring now to FIG. 4, there is shown a slightly simplified version of 
the embodiment shown in FIG. 3. In this case, the male thread 25 is formed 
directly adjacent the end of the pickup arm 19. In other respects the FIG. 
4 embodiment functions in like manner to that shown in FIG. 3. 
It is to be understood that both the FIG. 3 and FIG. 4 embodiments may be 
simplified further through the use of one, rather than two, tapered 
surfaces. 
Although an illustrative embodiment of this invention has been described in 
detail herein with reference to the accompanying drawings, it is to be 
understood that the invention is not limited to that precise embodiment, 
and that various changes and modifications may be effected therein by one 
skilled in the art without departing from the scope or spirit of the 
invention as defined in the appended claims.