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BACKGROUND OF THE INVENTION
This invention relates to camera mounts, and particularly to such mounts
for adapting field portable cameras to fit on studio mounts and tripod
bases.
In the television art, field-portable cameras of lightweight and compact
construction are used for news gathering and other field uses, while in
the studio, larger more elaborate cameras are mounted on cranes, tripods
or heavy wheeled bases. In the interests of flexibility and economy, it
has lately become the practice to provide special housings for adapting
portable cameras to studio mounts, such housings being arranged, first, to
solidly mount the portable camera; second, to carry the more elaborate
electronic and other equipment associated with studio cameras; and, third,
to attach solidly to the tripod or other studio base required.
A common form of special housing includes or is comprised by a front plate
with a bottom plate extending horizontally from the bottom edge of the
front plate to support the bottom of the camera and to attach to the
studio base. The lens then is attached solidly to the camera, e.g., by
means of a bayonet-ring coupling, and extends from the camera through an
opening in the front plate, which does not directly support either the
camera or the lens.
When very large lenses are to be employed, however, special problems arise.
Such large lenses may weigh nearly as much as the portable camera itself.
Consequently, the lens assembly tends to sag out of its delicate optical
alignment with the camera, and requires separate bracing, usually in the
form of cantilever-type extension brackets. The resulting assembly is
often awkward, cumbersome, and visually unpleasing.
Accordingly, it is an object of the present invention to provide a studio
mount for portable cameras and heavy lens assemblies in which optical
alignment of camera and lens is preserved without the need for cantilever
extension brackets for the lens;
It is another object of the invention to provide a studio mount for
portable cameras in which moments exerted by the camera are precisely
countered.
SUMMARY OF THE INVENTION
This and other objects of the invention are attained in the present
invention by means of a camera mount of the type including a front plate
having an attachment to the lens-mounting frontal side of a
camera-and-lens assembly, and a bottom plate extending rearwardly,
parallel to the lens axis, from the lower portion of the front plate for
supporting the rearward portion of the camera and for mounting the camera
on a base structure, characterized in that means are provided on the
bottom plate for engaging and supporting the rearward portion of the
camera and for countering the moment exerted by the weight of the camera
about its attachment; and means are provided for clamping the camera to
the bottom plate and to the supporting means thereof.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevation view of a portable camera and heavy lens assembly
mounted in a studio mount according to the invention;
FIG. 2 is a perspective view, partly fragmented and in phantom, of a
portion of the apparatus shown in FIG. 1;
FIG. 3 is a cross-sectional elevation view, to an enlarged scale, of a
portion of the apparatus enclosed in lines 3--3 of FIG. 1;
FIG. 4 is a perspective view, to an enlarged scale, of portions of the
apparatus shown in FIG. 1;
FIG. 5 is an exploded perspective view of portions of the apparatus shown
in FIG. 4;
FIG. 6 is a plan view, partly in phantom, of the apparatus shown in FIG. 4;
and
FIG. 7 is a cross-sectional elevation view taken on the plane of lines 7--7
of FIG. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, there is shown a portable television camera 11
having a carrying handle 12 and shoulder saddle 13. A heavy lens assembly
14 is attached to the camera 11 by means of a coupling including a bayonet
ring 16, and the assembly 11-14 is mounted in a studio mount 17 as by
means of a lens mounting plate 18 extending from the lens assembly 14 and
attached to a front plate 19 of the mount 17. The remainder of the mount
17 includes a bottom plate 21 extending horizontally and rearwardly from
the bottom of the front plate 19, portions of a studio base or tripod
attachment means 22 extending from the bottom plate, protecting and
handling cage grille bars 23 attached to the front and bottom plates, and
a viewfinder apparatus 24, attached to the bars 23.
The apparatus so far described is known in the art; including the
attachment means 16, 18 and 19, which is described further as follows.
The lens mounting plate 18, see also FIG. 2, has a three-point connection
with the mount front plate 19, namely through a pair of upper wedge
elements 26 extending from the plate 18 and engaging and locking into
corresponding wedge elements 27, which extend from plate 19, and a lower
spring-loaded wedge element 28, which projects into an opening 29 in the
front plate 19, springily engaging only the upper interior surface of the
opening 29. To make certain that full engagement of the mating surfaces of
the elements 26, 27 and 19, which are all gauge surfaces, is not inhibited
the opening 29 is made substantially wider than the element 28, and
precise lateral positioning of the lens plate 18 is provided by means of a
positioning pin 25 extending from plate 18 and fitting loosely in a
vertical direction, but snugly in a lateral direction, in an upwardly
opening slot 30 in the upper portion of front plate 19. A clamp 31, here
shown as a double-action pressure clamp of the type CL-150-HTC
manufactured by the Carr Lane Co. of St. Louis, Missouri, may be mounted
on the lower front portion of the front plate 19 to clamp the lens plate
18 solidly thereto.
As shown in FIGS. 2 and 3, the bayonet ring 16 is rotatably threaded onto a
tubular portion 33 of the lens assembly 14, and presents three
circumferentially equispaced bayonet lugs 34 each of slightly less than 60
degrees arcuate dimension, between which may be passed a similar trio of
lugs 36 extending from a tubular portion 37 of the camera 11. The ring 16
may then be rotated about 60 degrees on its threads 38 to bring the lugs
34 into circumferential locking registration with the lugs 36, and to
concurrently snug the lugs 36 tightly against an end flange of the lens
tube 33. In FIG. 2 the lugs 34 are shown in the open (unlocked) position,
and in FIG. 3 they are shown in the rotated (locked) position.
Also shown in FIG. 1 is a pair of wedge elements 41, 42, which may be used
to retain the front portion of the camera 11 when a smaller lens is to be
used and when, in consequence, it is not necessary to employ the lens
plate 18 or its coupling to the front plate 19. For such use, the wedge
element 42, on the plate 21, is pivoted 180 degrees horizontally to cause
its wedge face 43 to face rearwardly, and the forwardly facing wedge face
44 of element 41 can then engage face 43, with the flat bottom of the
element 41 supporting the weight of the front portion of the camera upon a
plateau 46 formed on the element 42.
To support the rearward portion of the camera, whether element 42 is used
or plate 18, the present invention contemplates a structure 51, also shown
in FIGS. 4-7, for precisely countering the vertically downward rotational
moment of the camera.
Upon the rearward portion of plate 21 is secured a frame member 52, as by
bolts or machine screws 53, which pass through openings 54 in member 52,
the openings 54 being elongated in a forward-rearward direction to permit
later positional adjustment. A shoe 56 extends downwardly from camara 11
and rests upon a pressure distributing plate 57, which in turn is pivoted
on a shaft 58 journalled on set-screw pins 59 between two arms 60 of the
frame 52. To support the plate 57, a torque screw 61 is threaded upwardly
through frame 52 to engage the plate 57 beneath shoe 56. The torque screw
61 shown is of a type TS-30 manufactured by Ace Drill Co. of Newark, N.J.
and has an end pressure of 18-22 pounds, described as the maximum pressure
that may be supported by the upper end of the screw while the screw
retains its ability to turn in the threads of the screw hole. When this
pressure is exceeded, a springloaded detent ball 63 slips out of a small
recess in a metal bearing plate 64 which is retained by a retaining ring
66 inside the screw's manually rotatable knob 67, permitting the knob to
turn freely with respect to the threaded screw body 68.
Thus, to counter the moment of the camera-lens assembly, it is merely
necessary to turn the knob 67 until it begins to turn freely around the
screw body 68, the end-pressure characteristic of the torque screw having
been selected to precisely counter-balance that moment.
To assist in clamping the shoe member 56 to the plate 57, the shoe is
formed with an upward and rearwardly opening conical recess 71, the
vertical axis of which lies outside the body of the shoe, and a floating
conical detent member 72 is arranged to seek and seat itself in the recess
71. The conical member 72 is mounted on a leaf spring member 73 as by
means of a slot 74 (FIG. 5) formed in the member 72 for the leaf 73, and a
screw 76 passing through the upper portion of the conical member 72 and
the leaf 73 and threaded into the lower portion of member 72. The leaf 73
has elongated end slots 78 by which the leaf may be mounted for lateral
sliding motion between brackets 79 as by means of bolts 81, while vertical
seeking and seating motion of the conical detent 72 is permitted by the
flexibility of spring leaf 73. The brackets 79 form part of a
forward-rearward slider member 82, from which extend a pair of forwardly
directed slider rods 83, which slide in bores 84 of member 52, the rods
being springloaded for rearward (retracting) movement, and being urged
forwardly to seat the conical detent 72 as by means of a bell-crank toggle
handle 86, which in closed position (phantom, FIG. 6) bears against a
spring leaf 87 mounted at the ends in slots in member 82. The ends of leaf
87 have a trapezoidal inclination, so as to assure retention of the leaf
in its slots in member 82 when inserted from below. The handle 86 is
separately mounted, being pivoted by a bolt 91 to a plate 92 that is
(forwardly-rearwardly) adjustably mounted on frame 52 by means of bolts
93. A spring clip 96 extends from plate 92 to secure the handle 86 in
closed position; the clip end may be manually depressed to release the
handle.
To move the conical member 72 forwardly for seeking and seating in the
conical recess 71 of the camera, the forward end 101 of the crank 86
transmits force through the spring leaf 87 to the end of a sliding shaft
102, on the forward end of which is mounted a friction plate 103. The
plate 103 has a roughened forward surface 104 confronting and engaging a
similar surface 106 formed on a friction element 107, which in turn is
mounted on the spring leaf 73 by means of a bolt 108. Thus, while the
conical element 72 is moving forwardly but has not yet seated firmly in
the conical recess 71, the conical element 72 has freedom for seeking and
seating motion in upward-downward directions 109 (FIG. 5) and in
horizontal lateral directions 111, all orthogonal to the forward-backward
seating and retracting directions 112 in which it is moved by the crank 86
or springs 84; but when the conical element 72 reaches its final seating
position in the conical recess 71, the friction elements 103, 107 become
locked in pressurized frictional engagement and cannot easily be shifted
laterally with respect to one another. The shaft 102 is provided with
lateral saw cuts 113 from alternating sides so as to springly apply the
needed pressure to the friction elements 103, 107. The shaft 102 may be
secured) e.g. magnetically to the leaf 87, or otherwise spring loaded for
retraction when released by the crank 86.
It will be understood that the conical element 72 will usually seat in the
recess 71 so as to be engaged therewith only tangentially, i.e., along
substantially only a single generatrix of the member 72 and a single
generatrix of the surface 71, for as the member 72 rises with respect to
the surface 71, each portion of the element, which has a given radius of
curvature, encounters portions of the surface 71 of greater and greater
radius of curvature. This essentially linear contact between the two
elements is useful in permitting play of the element 72 in its seeking and
seating movements.
What has been described is a camera mount of the type including a front
plate having an attachment to the lens-mounting frontal side of a
camera-and-lens assembly, and a bottom plate extending rearwardly,
parallel to the lens axis, from the lower portion of the front plate for
supporting the rearward portion of the camera and for mounting the camera
on a base structure, characterized in that means are provided on the
bottom plate for engaging and supporting the rearward portion of the
camera and for countering the moment exerted by the weight of the camera
about its attachment; and means are provided for clamping the camera to
the bottom plate and to the supporting means thereof.
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