Extendible arms

The disclosure relates to an extendible arm for a camera stand or the like, comprising an outer elongate rigid sleeve and an inner elongate rigid sleeve telescopically slidable with respect to the outer sleeve to extend therefrom by a variable amount. One end of the inner sleeve disposed within the outer sleeve has a detent mechanism for locking the inner sleeve in any of a number of positions of extension with respect to the outer sleeve and a release member for the detent mechanism is provided at the other end of the inner sleeve which projects from the outer sleeve with a connection between the release member and detent mechanism extending through the inner sleeve for remote operation of the detent mechanism by the release member.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to extendible arms for camera stands and the like 
and in particular for spreader units embodied in camera stands to support 
the legs of the stand. One spreader unit in which the extendible arm may 
be incorporated is described and illustrated in our UK Patent Application 
No. 9504929.2. 
2. Background Prior Art 
Telescopically extendable struts are widely used in a variety of 
applications. In some instances friction between members is relied on to 
hold the strut at a particular extension. Where rigidity is required 
locking arrangements are provided. These can take the form of push buttons 
mounted on an inner member to project and engage in a selected hole in a 
range of holes in an outer member. Other arrangements involve a rotary 
locking device at the open end of the outer member to lock with the inner 
member. For adjustment of all these arrangements it is necessary for the 
operator to reach to the region where an inner member extends from an 
outer member to operate the lock. 
SUMMARY OF THE INVENTION 
This invention provides an extendible arm for a camera stand or the like, 
comprising an outer elongate rigid sleeve, an inner elongate rigid sleeve 
telescopically slidable with respect to the outer sleeve to extend 
therefrom by a variable amount, one end of the inner sleeve disposed 
within the outer sleeve having a detent mechanism for locking the inner 
sleeve in any of a number of positions of extension with respect to the 
outer sleeve, a release member for the detent mechanism at the other end 
of the inner sleeve which projects from the outer sleeve and a connection 
between the release member and detent mechanism extending through the 
inner sleeve for operation of the detent mechanism by the release member. 
The detent mechanism may comprise at least one detent member mounted on 
said one end of the inner sleeve for radial movement with respect to the 
sleeve toward and away from the outer sleeve and the outer sleeve has stop 
means to receive the detent member at selected positions along the outer 
sleeve to lock the inner and outer sleeves together. 
More specifically the detent member may be pivotally supported on the inner 
sleeve for movement into and out of engagement with the outer sleeve. 
In one arrangement according to the invention said one end of the inner 
sleeve may have an enlarged head which is a sliding fit in the outer 
sleeve and said detent member is pivotally supported in the head to extend 
and retract into and out of engagement with said stop means. 
In the preferred arrangement the detent member comprises a rocker arm 
pivotally supported part-way along the arm in the head and having a detent 
finger at one end thereof to project outwardly of the head, the head 
having an outwardly facing slot for the detent finger and means are 
provided within the head operated by said release member for pivoting the 
rocker to extend and retract the detent finger thereon into and out of 
engagement with said stop means. 
In the preferred arrangement the detent member comprises a rocker arm 
pivotally supported part-way along the arm in the head and having a detent 
finger at one end thereof to project outwardly of the head, the head 
having an outwardly facing slot for the detent finger and means are 
provided within the head operated by said release member for pivoting the 
rocker to extend and retract the detent finger thereon into and out of 
engagement with said stop means. 
The outer sleeve may have apertures at spaced locations along the sleeve to 
receive the detent finger to lock the sleeves together. 
The rocker arm may have an inner cam surface and the means for pivoting the 
arm comprises a shuttle mounted for longitudinal movement in the head and 
engageable with the cam surface on the arm which is shaped so that 
movement of the shuttle in one direction tilts the arm to extend the 
detent finger from the slot and in the opposite direction retracts the 
detent finger into the slot. 
The cam surface on the inner side of the rocker arm may comprise inwardly 
projecting cam lobes at either end of the rocker arm between which the 
rocker arm pivots and with which the shuttle is engageable to tilt the arm 
in one or the other direction. The cam lobes may each have a ramp to ride 
up an end of the shuttle to pivot the arm in one or another direction and 
flats at the peaks of each lobe to engage a side of the shuttle and 
thereby hold the arm with the detent finger extended or retracted 
respectively. 
Preferably a pair of rocker arms are provided on opposite sides of the head 
and the shuttle is disposed between the rocker arms to extend and retract 
the detent fingers on the arms. 
Further a rod may connect the shuttle to the release member at said other 
end of the inner sleeve for operation of the shuttle. 
The release member may comprise a trigger member secured to the end of the 
rod at said other end of the inner sleeve and projecting outwardly of the 
sleeve through longitudinal slots in the sleeve. 
More specifically the trigger member may have a cover encircling the inner 
sleeve to enclose and conceal the slots in the sleeve over the range of 
movement of the trigger. 
A spring may be provided in the sleeve acting on the release member in a 
direction to extend said detent, the detent being released by movement of 
the release member against the action of the spring.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The drawings show a telescopic arm which is suitable for use in a variety 
of applications but, in this particular instance, is intended for use in a 
spreader unit for stabilising the legs of a camera mounting tripod. The 
spreader unit comprises a central hub and three such arms radiating from 
the hub and coupled to the legs of the tripod to hold the legs in their 
selected spread orientation and thereby stabilizing the tripod. An example 
of such a spreader unit is described and illustrated in our UK Patent 
Application No. 9504929.2. 
The telescopic arm is indicated generally at 10 and comprises an outer 
elongate rigid metal sleeve 11 of oval cross-section and an inner elongate 
rigid sleeve 12 of circular cross-section spaced within the outer sleeve. 
The outer sleeve 11 is closed at one end 13 by an attachment 14 for 
securing the sleeve to the central hub of, for example, a tripod. The 
other end 15 of the outer sleeve is closed by a plug 16 secured in the end 
of the sleeve and having a central bore 17 through which the inner sleeve 
12 extends. The end 18 of the inner sleeve within the outer sleeve has an 
enlarged oval cross-section head 19 secured thereto by an integral spigot 
which is fixed in the end 18 of the tube. The head 19 is a sliding fit in 
the outer sleeve and thus the inner sleeve is supported for sliding 
movement into and out of the outer sleeve. 
The head 19 has an inner end 20 adjacent sleeve 12 and an outer end 21. A 
bore 22 extends centrally in to the head 19 from the outer end and has 
radial slots 23 on either side thereof which extend lengthwise of the 
bore. Midway along each slot 23 from the outer end of the head 19 the 
sides of the slot 23 are stepped as at 24 to reduce the slot width. The 
end of the slots 23 at the outer end of the head have radial openings 25 
to the outer side of the head 19. A pair of rocker arms 26 are located for 
pivotal movement in the respective slots. Each arm is flanked by integral 
arcuate bearing faces 27 formed midway along the arms to engage with the 
abutments in the slots to allow limited pivoting and movements of the arms 
in the slots 23. 
The ends of the rocker arms 26 of the outer end of the head 19 have 
outwardly extending detent fingers 28 which project through said openings 
in the head 19. The outer tube 11 is formed with pairs of apertures 29 in 
the tube wall at spaced locations along the tube to receive the detent 
fingers 28 to lock the tubes together at different positions of telescopic 
adjustment of the inner tube with respect to the outer tube. 
The rocker arms 26 each have a pair of cam lobes 30, 31 formed on their 
inner sides adjacent the respective end of each arm. Each lobe comprises a 
ramp 32 and a flat 33 at the peak of the lobe. A push rod 34 extends 
through the sleeve 12 and has one end 35 extending into the bore in the 
head 19. A shuttle 36 is mounted on the end 32 of the push-rod and is 
secured thereto by a pin 37. The shuttle 36 engages between the rocker 
arms 26. 
Movement of the shuttle towards the outer end 21 of the head 19 causes the 
shuttle 36 to engage ramps 32 of the cam lobes 30 on the rocker arms 26 
forcing the ends of the arms apart to extend the detent fingers 28 from 
the head. Eventually the shuttle 36 locates between the flats 33 of the 
cam lobes 30 with the sides of the shuttle 36 engaging the flats 33 to 
lock the outer ends of the rocker arms 26 with the detent fingers 28 in 
their extended positions as shown with the detent fingers 28 engaged in 
the selected apertures 29 in the outer sleeve 11. The sides of the detent 
fingers 28 which engage the openings in the head and the aperture in the 
outer sleeve 11 tie at right angles to the sleeve/head axis so that there 
is no tendency for the outer sleeve to force the detent fingers 28 
inwardly. In any event the shuttle 36 is locked between the ends of the 
rocker arms 26 preventing inward movement of the arms with respect to the 
shuttle 36. Thus the risk of the head inadvertently releasing the outer 
sleeve is most unlikely. 
When the shuttle 36 is moved towards the inner end of the head, the cam 
lobes 30 of the rocker arms 26 are released and the shuttle 36 engages 
between the cam lobes 31 at the other ends of the arms forcing those ends 
of the arms apart and thereby retracting the detent fingers 28 disengaging 
them from the slots 24 to allow the inner and outer sleeves of the arm to 
be adjusted. 
The other end of the inner sleeve 12 projects from the outer sleeve 11 
through the plug 16 and an attachment 40 is secured to the end of the 
sleeve by a plug 41 glued into the end of the sleeve. The attachment 40 is 
connected to a tripod leg. 
A cross-pin 42 is fixed in the end to project to either side of the 
push-rod and a compression spring 43 acts between the plug 41 and 
cross-pin to force the push rod in a direction to extend the aforesaid 
detent fingers for locking the inner and outer sleeves together. A collar 
44 is slidably mounted on the end part of the inner sleeve 12 projecting 
from the outer sleeve and is formed with radially inwardly extending lugs 
45 which pass through elongate slots 46 in the inner sleeve to engage the 
opposite side of the cross-pin 42 to the compression spring. The collar 44 
is formed with an encircling finger plate 47 for drawing the collar 
against the action of the spring 45 to retract the detent fingers 28, 30, 
31 for adjustment of the arm. The length of the collar 44 is such that the 
slots 46 for the lugs 45 are concealed throughout its range of movement. 
The sleeve 12 may be formed with encircling grooves at spaced locations 
along the sleeve which correspond to positions of adjustment of the inner 
and outer sleeve determined by the locations of the apertures 26 in the 
outer sleeve so that when a groove is revealed at the bush 16, the detent 
fingers are aligned with an appropriate pair of slots 26. Conveniently the 
grooves may be coloured to identify particular positions of adjustment of 
the arms.