Dual rotating mechanical lock

A mechanical lock of the type in which axial translational movement of a rod is prevented by a coil spring which encircles the rod and grips it and being readily released by application of a relatively small force through a relatively short stroke, thereby permitting the mechanical lock to be controlled by a pushbutton control. Rotating bushings adjacent the ends of the springs have beveled faces which cause the locking turns at the ends of the spring to become cocked on the rod to provide a true locking action. The device is unlocked by rotation of the rotating bushings, which unwind the locking turns of the spring, thereby releasing the grip of the spring on the rod. The rotating bushings are rotated in opposite directions by actuating levers which extend outside of the housing of the device. The actuating levers are provided with rollers and are located at the same station along the axis of the rod. A symmetrical wedge-shaped cam is mounted so that it can be drawn axially between the rollers, forcing them apart circumferentially and thereby rotating the actuating lever about the axis of the rod. The wedge-shaped cam is drawn in an axial direction by a cable which is connected to the pushbutton control. The structure of the device simplifies its assembly, thereby reducing the production cost.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is in the field of mechanical locking devices and 
specifically relates to a device of the type in which the locking is 
effected by a coiled spring which grips a rod, for clamping two members 
against translational motion and for selectively enabling such motion when 
the ends of the springs are twisted in opposite directions simultaneously 
to unwind the coiled springs, thereby relaxing its grip on the rod. 
2. The Prior Art 
The present invention includes a rod which extends into a cylindrical 
housing. Normally, the present invention locks the rod with respect to the 
housing so that axial translational motion of the rod relative to the 
housing is prevented. The mechanical lock can be selectively actuated to 
an unlocked state in which motion of the rod is enabled. In the present 
invention, the opposite ends of the spring are each connected to actuator 
levers which are used to rotate the opposite ends of the spring in 
opposite directions to unwind the spring, so that its diameter increases 
slightly, thereby causing the spring to relax its grip on the rod, which 
may then be moved freely axially relative to the housing. 
The use of a coiled spring to grip a rod extending coaxially through the 
spring is well known. A number of locking devices making use of this basic 
principle have been patented. While all of the patented devices use this 
same fundamental principle, the implementations employed are patentably 
distinct. The present invention is believed to provide still another new 
and useful implementation. 
In U.S. Pat. No. 3,230,595 issued Jan. 25, 1966 to Kedam, there is shown a 
rod-clamping device in which both ends of the spring are rotated 
simultaneously to lock and unlock the device. However, rotation of the 
ends of the spring is not produced by an actuator lever, but instead by 
grooves which exert a camming action on the ends of the spring. The device 
described in Kedam's patent includes no provision for causing the last few 
turns at each end of the spring to become cocked on the rod to produce a 
more positive locking engagement. 
This latter feature is shown clearly in U.S. Pat. No. 3,249,180 issued May 
3, 1966 to Torossian and in U.S. Pat. No. 2,750,994 issued June 19, 1956 
to Howell. However, in these patents, only one end of the spring is 
rotated to lock and unlock the device and therefore the stroke required is 
longer than in the present invention. 
In U.S. Pat. No. 3,874,480 issued Apr. 1, 1975 to Porter et al., there is 
described a friction brake mechanism in which two springs are unwound 
simultaneously to unlock the grip of the springs on a rod. Also, in U.S. 
Pat. No. 3,064,766 issued Nov. 20, 1962, Hanizeski shows a spring lock in 
which two separate springs are simultaneously unwound by an 
electromagnetic device to produce the desired unlocking. 
All of the above-mentioned inventions can be distinguished on the basis of 
their structures from the device of the present invention. The present 
invention arose from the desirability of having a true locking action of 
the type wherein the last few turns at the ends of the spring become 
cocked on the rod, but at the same time being releasable by actuation 
through a relatively short stroke and by means of a cable which extends in 
the axial direction. This particular combination of features was 
unavailable in the known prior art and necessitated the present invention. 
SUMMARY OF THE INVENTION 
In the present invention, both ends of the spring are rotated 
simultaneously to unlock the device. This is done in a balanced manner by 
means of a novel actuator in which the motion of a cable in a direction 
parallel to the axis of the rod pulls a wedge-shaped cam between two 
actuating levers to rotate them equally, but in opposite directions in a 
balanced manner. 
The actuating motion is transmitted from the actuating levers to rotating 
bushings which in turn engage the ends of the spring. The faces of these 
rotating bushings adjacent the spring are bevelled so that any force 
applied to the rod will tend to cause the last few turns on the spring to 
become cocked on the rod to provide a true locking engagement in which the 
locking force increases as the disturbing force applied to the rod 
increases. 
Because the spring is unwound from its ends which lockingly engage the rod, 
a very short stroke of the actuator is possible, because it is not 
necessary for the entire spring to be unwound, but only the first few 
turns at each end. 
The short stroke achieved with the actuator used in the present invention 
permits pushbutton control of the device, which is desirable from a 
styling and convenience standpoint. 
The novel features which are believed to be characteristic of the 
invention, both as to organization and method of operation, together with 
other objects and advantages thereof, will be better understood from the 
following description considered in connection with the accompanying 
drawings in which a preferred embodiment of the invention is illustrated 
by way of example. It is to be expressly understood, however, that the 
drawings are for the purpose of illustration and description only, and are 
not intended as a definition of the limits of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning now to the drawings, in which like parts are denoted by the same 
reference numeral throughout, it is seen that the preferred embodiment of 
the invention includes a rod 12 having a mounting 13 at its free end, and 
selectively slideable axially within a housing 40 having a mounting 
attachment 42 at one end. Normally, motion of the rod 12 with respect to 
the housing 40 is prevented by the spring 14 which normally grips the rod 
12 tightly. 
Rotating bushings 20, 22 are located at opposite ends of the spring 14, and 
axial motion of the rotating bushings 20, 22 is prevented by the fixed 
bushing 32, 34, which are swaged to the housing 40. 
The spring 14 includes radially-extending tangs 28, 30, which fit into 
axially extending slots 25, 27 in the rotating bushings 20, 22. The 
rotating bushings 20, 22 include bevelled faces 24, 26 against which the 
locking coils 36, 38 of the spring 14 bear, thereby becoming cocked with 
respect to the rod 12 to lock the rod against axial translational motion 
with respect to the housing 40. 
Actuating levers 16, 18, best seen in FIGS. 2 and 4, are shaped to encircle 
the spring 14, and portions 44, 46 of actuating levers extend into the 
same axially-extending slots 25, 27 in the rotating bushings 20, 22 as the 
tangs 28, 30 of the spring 14, so that as the actuating levers are rotated 
about the axis of the rod, that motion is coupled by the portions 44, 46 
to the rotating bushings 20, 22 and thence to the tangs 28, 30 of the 
spring 14 causing the spring to unwind slightly, thereby releasing its 
grip on the rod 12. Because the locking coils 36,38 of the spring 14 are 
the coils nearest the end of the springs, and because it is those ends of 
the spring that are rotated by the rotating bushings 20, 22, the amount of 
stroke of the actuating levers 16, 18 is minimized. In some locking 
devices known in the prior art, it is necessary to unwind the entire 
length of the spring to release the rod, and this requires a much longer 
stroke than is required in the present invention. 
Also, in some mechanical locks known in the prior art, two springs are 
employed, and to unwind both of those springs requires a greater actuating 
force than is required in the present invention which employs only a 
single spring. 
Because of the reduced stroke and reduced actuating force in the present 
invention, it is practical to use a push-button for unlocking the 
mechanical lock of the present invention. The use of a pushbutton for 
actuation is very desirable from the standpoint of styling and 
convenience. 
When an operator presses on the control button to release the lock, the 
cable 48 is drawn to the right as viewed in FIG. 1. One of the novel 
features of the present invention is the manner in which this motion of 
the cable is used to operate the actuating levers 16, 18. 
As best seen in FIGS. 3 and 4, each of the actuating levers 16, 18 includes 
a roller mounted on it, and in accordance with a preferred embodiment of 
the invention, rollers 52, 54 are forced apart as indicated by the arrows 
in FIG. 3, when the wedge-shaped cam 50 is drawn in the direction shown. 
This separating movement of the rollers 52, 54 is opposed by the spring 14 
which is being unwound as the wedge-shaped cam 50 is drawn between the 
rollers 52, 54. This unwinding of the spring 14 releases the grip of the 
spring on the rod 12. A plastic housing 56 encloses the roller mechanism 
and serves to keep foreign matter from contaminating it. In the preferred 
embodiment, the wedge-shaped cam 50 includes a guide bar 58, which is 
rigid, as opposed to the flexible cable 48, and grooves 60 in the walls of 
the plastic housing 56 cooperate with the guide bar 58 to maintain proper 
alignment of the wedge-shaped cam 50. In an alternative embodiment, a 
return spring may be included within the plastic housing 56 to urge the 
wedge-shaped cam 50 leftward as viewed in FIG. 3, to its normal locked 
position. 
The advantages of using the wedge-shaped cam 50 and the rollers 52, 54 to 
operate the actuating levers 16, 18 can readily be seen. From FIG. 3 it is 
clear that the actuating levers 16, 18 will be rotated simultaneously in 
opposite directions about the axis of the rod by equal amounts, thereby 
insuring that both ends of the spring 14 are unlocked at the same instant. 
Further, the rollers 52, 54 are centered along a line perpendicular to the 
axis of the rod 12, and therefore the forces between the wedge-shaped cam 
and the rollers 52, 54 are balanced and there is no tendency to produce a 
torque on the device; the mechanical lock is subjected to an axial force 
only. Finally, the mechanism employed in the present invention is a 
compact and convenient way of converting an axial motion of the cable 48 
into two balanced opposed rotational motions of the roller. 
As best seen in FIG. 1, assembly of the mechanical lock is simplified by 
its structure. Typically, the fixed bushing 32, the rotating bushing 20, 
the spring 14, the rotating bushing 22, and the fixed bushing 34 are slid 
onto the rod 12. A slot 60 extends axially in the housing 40 to permit the 
actuating levers 16, 18 to be slid into position encircling the spring 14. 
Because this slot would not permit proper swaging at the right-hand end of 
the device as shown in FIG. 1, a sleeve 62 is applied over the housing 40 
prior to the swaging operation. Also, a control bracket 64 is positioned 
adjacent the fixed bushing 34 prior to the swaging operation so that the 
control bracket 64 will be permanently fastened to the lock when the 
suaging operation has been completed. The plastic housing 56 consists of 
two halves in a preferred embodiment, and these snap together and are held 
at a proper position circumferentially by means of a tang in the housing 
40. 
Thus, there has been described a mechanincal lock which has a structure 
that permits the lock to be controlled by a pushbutton. This is made 
possible by the low stroke and actuating force requirements of the device. 
It is also seen that the structure of the device facilitates assembly of 
the mechanical lock and this, in turn, helps to reduce the production 
costs. 
The foregoing detailed description is illustrative of a preferred 
embodiment of the invention, but it will be understood that additional 
embodiments thereof will be obvious to those skilled in the art. The 
embodiments described herein, together with those additional embodiments 
are considered to be within the scope of the invention.