U.S. patent application number 11/740318 was filed with the patent office on 2007-11-01 for camera track and dolly system.
This patent application is currently assigned to A&C LTD.. Invention is credited to Frank FLETCHER, David SHERWIN.
Application Number | 20070251408 11/740318 |
Document ID | / |
Family ID | 36589869 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070251408 |
Kind Code |
A1 |
FLETCHER; Frank ; et
al. |
November 1, 2007 |
CAMERA TRACK AND DOLLY SYSTEM
Abstract
A system for moving a camera along a predefined path in space,
the system comprising: a track (2), the track comprising at least
one rail (10, 12); a dolly (4) adapted to ride on the track; and a
rack and pinion drive mechanism (6) for driving the dolly along the
track. The drive mechanism includes a rack (40) extending along the
track and a driven pinion (60) mounted on the dolly, and the rack
is positioned vertically inline with the at least one rail of the
track.
Inventors: |
FLETCHER; Frank;
(Borehamwood, GB) ; SHERWIN; David; (Watford,
GB) |
Correspondence
Address: |
STITES & HARBISON PLLC
1199 NORTH FAIRFAX STREET, SUITE 900
ALEXANDRIA
VA
22314
US
|
Assignee: |
A&C LTD.
Harrow
GB
|
Family ID: |
36589869 |
Appl. No.: |
11/740318 |
Filed: |
April 26, 2007 |
Current U.S.
Class: |
104/247 |
Current CPC
Class: |
B61B 13/02 20130101;
B61C 11/04 20130101; F16M 11/18 20130101; B66C 9/04 20130101; F16M
11/425 20130101 |
Class at
Publication: |
104/247 |
International
Class: |
B61F 9/00 20060101
B61F009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2006 |
GB |
0608279.6 |
Claims
1. A system for moving a camera along a predefined path in space,
the system comprising: a track, the track comprising at least one
rail; a dolly adapted to ride on the track; and a rack and pinion
drive mechanism for driving the dolly along the track, the drive
mechanism including a rack extending along the track and a driven
pinion mounted on the dolly; wherein the rack is positioned
vertically inline with said at least one rail of the track.
2. The system according to claim 1, wherein the track comprises two
parallel rails, the rack being positioned vertically inline with
one of the rails.
3. The system according to claim 1, wherein the rack and rail are
held in position relative to one another by a common support
member.
4. The system according to claim 2, wherein the rack and rail are
held in position relative to one another by a common support
member.
5. The system according to claim 3, wherein the rail is formed
integrally with the support member.
6. The system according to claim 3, wherein the rack is formed
integrally with the support member.
7. The system according to claim 3, wherein the rack is a separate
component mounted on the support member.
8. The system according to claim 7, wherein the support member is
an extruded member.
9. The system according to claim 8, wherein the cross-section of
the extrusion is shaped to provide one or more locating and/or
retaining formations for locating and/or securing in position the
separate rack component.
10. The system according to claim 9, wherein the locating and/or
retaining formations include a recessed channel and one or more
lip(s).
11. The system according to claim 1, wherein the rack includes a
flexible rack component that can conform to the shape of a curved
track.
12. The system according to claim 1, wherein the pinion is mounted
on the dolly such that when the dolly rides on the track and the
pinion engages with the rack, a rotational axis of the pinion
pivots about a vertical axis in line with a vertical center line of
the rail with which the rack is associated.
13. The system according to claim 1, wherein the system further
comprises a camera mounted on the dolly.
14. A rack and rail assembly for use with a system according to
claim 1, the assembly comprising: a support member; a rail fixed to
the support member for engaging one or more wheels of the dolly and
protruding from the support member so that a vertical center line
of the rail is offset to one side of the support member; and a rack
member fixed to the support member to protrude from the support
member to the same side as the rail, with the pitch circle diameter
of the rack being inline with the vertical center line of the
rail.
15. The assembly according to claim 14, wherein the support member
is an extruded member.
16. The assembly according to claim 15, wherein the cross-section
of the extrusion is shaped to provide one or more locating and/or
retaining formations for locating and/or securing in position the
rack member.
17. The assembly according to claim 14, wherein the rack member is
flexible so that it can conform to the shape of a curved track.
18. An extruded support and rail member for use with the system
according to claim 1, the extruded member comprising: a support
portion; a rail portion for engaging one or more wheels of a dolly
and protruding from the support portion so that a vertical center
line of the rail portion is offset to one side of the support
member; and one or more rack locating and/or retaining formations
formed on the side of the support portion to which the rail portion
is offset for retaining the rack of a rack and pinion drive
mechanism with the pitch circle diameter of the rack inline with
the vertical center line of the rail.
19. The member according to claim 18, wherein the locating and/or
retaining formations include a recessed channel and one or more
lip(s).
Description
FIELD OF THE INVENTION
[0001] The present invention relates to camera track and dolly
systems for moving cameras (e.g. film and/or video cameras) along a
predetermined path.
BACKGROUND
[0002] When creating films and videos it is very often necessary to
change the orientation and position in space of one or more cameras
during shooting. To control the orientation of a film or video
camera it is known to mount the camera on a remote control head,
enabling pan, tilt and roll movements of the camera and lens.
Movement of the camera in space is typically achieved by mounting
the camera (generally on its remote control head) on a carriage,
known as a "dolly", that rides on a linear track.
[0003] Known track and dolly systems typically use tracks having a
pair of parallel rails. The rails are held a fixed, constant
distance apart by sleepers spaced along the track at regular
intervals. Some systems use only straight tracks but other use
curved tracks or combinations of straight and curved tracks (curved
in two or three dimensions).
[0004] The dolly is generally a rectangular carriage with wheels
that are profiled to guide the dolly along the track. In some known
systems the profile of the wheels serves to hold the dolly onto the
rails even when the dolly is inverted.
[0005] Generally the dolly is driven along the track. Various drive
arrangements are known, including frictions drives mounted on the
dolly and winch systems, in which the drive is fixed at one or both
ends of the track and the dolly is driven back and forth (or
sometimes just in a single direction) by a cable or belt connected
between the dolly and the winch drive. For curved tracks friction
drives are most common because winch systems can only be used where
a track curves by no more than about 10 degrees. For straight
tracks it is also known to use a rack and pinion drive, with a rack
running between the two rails or outside of the rails (e.g. on the
edge of the sleepers) and a driven pinion mounted on the dolly.
[0006] When shooting film and video footage, the repeatability of
camera positions can be important, especially as scenes are
typically shot and re-shot multiple times. It is important,
therefore, that track and dolly systems and their drive mechanism
enable accurate and repeatable positioning and movement of the
camera along the track.
[0007] Straight track systems using friction drives perform well in
this regard. On curved tracks, however, friction drives have been
found to slip, resulting in less accurate repetition of camera
movements. A winch drive can give better accuracy for repeating
movements on curved tracks but, as noted above, this approach
significantly restricts the extent to which the track can
curve.
[0008] The most accurate and repeatable drive arrangement,
especially in a straight line, is a rack and pinion because no
slippage can occur. Rack and pinion arrangements are, however, not
easy to use with curved tracks as it is necessary to ensure that
the correct pitch circle diameter ("PCD") of the pinion relative to
the rack is maintained along the length of the track and it can be
particularly difficult to do this at transitions between straight
and curved sections of track. Curved racks are also expensive.
SUMMARY OF INVENTION
[0009] In one aspect, the present invention provides a system for
moving a camera along a predefined path in space, the system
comprising: [0010] a track, the track comprising at least one rail;
[0011] a dolly adapted to ride on the track; and [0012] a rack and
pinion drive mechanism for driving the dolly along the track, the
drive mechanism including a rack extending along the track and a
driven pinion mounted on the dolly; [0013] wherein the rack is
positioned vertically inline with said at least one rail of the
track.
[0014] Preferably the track comprises two parallel rails, the rack
being positioned vertically inline with one of the rails.
[0015] By mounting the rack inline with a rail of a (single or twin
rail) curved track the pitch circle diameter of the rack is the
same as the pitch circle diameter of the rail with respect to the
pinion of the rack and pinion drive mechanism and remains so as the
dolly (on which the pinion is mounted) rides along the curved
track. In this way it is much easier to ensure that the PCD of the
pinion relative to the rack is maintained along the length of the
track even at transitions from straight to curved sections of the
track and vice versa.
[0016] The term "vertical" as used herein (above and further below)
is to be taken as a relative term (relative to the geometry of the
track) and not necessarily strictly as vertical in space because
the track will not necessarily be arranged strictly horizontal in
space along its full length (or even at any point along its length
in some cases). For twin rail tracks, the vertical center line of
the rail is a line extending through the rail perpendicular to both
the length direction of the rail and the width direction of the
track (i.e. perpendicular to a line joining the two rails).
[0017] The rotational axis of the pinion is generally parallel to
the vertical center line of the rail.
[0018] Preferably the rack and rail are held in position relative
to on another by a common support member. The rail and/or the rack
may be formed integrally with the support member. Preferably at
least the rail is formed integrally with the support member. For
instance, the support member can be formed as an extrusion with the
rail provided as an integral portion of the extruded
cross-section.
[0019] Whilst is would be possible to machine or otherwise form a
rack onto an extruded member, this would be costly. Preferably,
therefore, the rack is a separate component mounted on the support
member.
[0020] The support member may include means for locating and/or
securing in position a separate rack component. For example, where
the support member is an extruded member (with or without the rail
formed integrally with it) the cross-section of the extrusion may
be shaped to provide one or more locating and/or retaining
formations for the rack. Suitable locating/retaining formations
include protruding lugs and recessed channels (preferably with lips
that can retain corresponding shoulders on the rack section).
[0021] One preferred form of the support member is a generally
vertically extending plate-like section with the (preferably
integrally formed) rail portion protruding from the top (or bottom)
edge and off-set laterally so that the center line of the rail is
to one side of the plate section. The rack can then be mounted on
one side face of the plate section (the side to which the rail is
offset) such that it lies directly below (or above) the rail, in
line with the rail center line.
[0022] Preferred embodiments of the present invention use a
flexible rack component, e.g. of a moulded rubber or plastics
material, that can readily conform to the shape of a curved track.
This allows the rack to be flexed to assemble it with a curved
support member section (for a correspondingly curved rail), for
example by introducing it at one end of the support member section
and sliding it into or onto locating and retaining formations on
the support from that end.
[0023] The pinion of the rack and pinion drive mechanism is mounted
on the dolly such that when the dolly sits on the rail or rails of
the track the pinion (typically a spur gear) engages the rack. By
driving the pinion the dolly can therefore be moved back and forth
along the track and the positive engagement of the pinion with the
rack results in very accurate and repeatable positioning of the
dolly (and hence the camera that it carries) along the length of
the track.
[0024] Furthermore, with the rack component of the rack and pinion
drive mechanism mounted in the preferred manner discussed above,
the rack is by default retained inline with the rail along the
complete length of the track, enabling the relative position of the
rack and pinion to be easily maintained irrespective of the
curvature of the track.
[0025] To further ensure that the pinion (more specifically the PCD
of the pinion) can maintain its optimum position with respect to
the rack, the pinion is preferably mounted on the dolly in a manner
that allows its rotational axis to itself pivot about a vertical
axis in line with the vertical center line of the rail with which
the rack is associated. For example, the drive shaft of the pinion
(which is at its rotational axis) can be mounted on a swinging arm
that pivots on a bearing mounted on the dolly to be inline with the
vertical center line of the rail as the dolly rides along the
track. This enables some degree of movement of the pinion relative
to the dolly to ensure that it remains properly engaged with the
rack at all times, especially at transitions between straight and
curved sections of the track.
[0026] In another aspect, the invention provides a rack and rail
assembly for use with a system in accordance with the first aspect
above, the assembly comprising: [0027] a support member; [0028] a
rail fixed to the support member for engaging one or more wheels of
the dolly and protruding from the support member so that a vertical
center line of the rail is offset to one side of the support
member; and [0029] a rack member fixed to support member to
protrude from the support member to the same side as the rail with
the pitch circle diameter of the rack being inline with the
vertical center line of the rail.
[0030] The assembly may be curved along its length to provide a
rail for a curved section of dolly track.
[0031] The rail is preferably formed integrally with the support
member. The integral support member and rail may be an extruded
member.
[0032] The rack is preferably a separate component mounted on the
support member. Most preferably the rack is flexible so that it can
easily conform to the shape of the rail/support member along its
length.
[0033] The support member may have one or more formations to locate
and retain the rack member in the manner already discussed
above.
[0034] In a further aspect, the invention provides an extruded
support and rail member for use with preferred embodiments of the
camera dolly and track system of the present invention, the
extruded member comprising: [0035] a support portion; [0036] a rail
portion for engaging one or more wheels of a dolly and protruding
from the support portion so that a vertical center line of the rail
portion is offset to one side of the support member; and [0037] one
or more rack locating and/or retaining formations formed on the
side of the support portion to which the rail portion is offset for
retaining the rack of a rack and pinion drive mechanism with the
pitch circle diameter of the rack inline with the vertical center
line of the rail.
[0038] The locating and retaining formations may take any of the
forms already discussed above.
BRIEF DESCRIPTION OF DRAWINGS
[0039] An embodiment of the invention will now be described, by way
of example only, with reference to the accompanying drawings, in
which:
[0040] FIG. 1 shows, in cross-section (perpendicular to the
direction of motion) and camera dolly and track system in
accordance with an embodiment of the present invention;
[0041] FIG. 2 shows, on an enlarged scale, in cross-section, one
rail extrusion and rack assembly of the system of FIG. 1; and
[0042] FIG. 3 shows a schematic plan view, on a reduced scale, of
the system of FIG. 1, illustrating a dolly moving from a straight
track section onto a curved track section.
DESCRIPTION OF EMBODIMENT
[0043] The figures illustrate a presently preferred embodiment of
the camera dolly and track system of the present invention. In
overview, the system includes a track 2 and a dolly (carriage) 4
that rides on the track 2. A camera (not shown) can be mounted on
the upper side of the dolly 4, for example on a remote control head
(also not shown). The dolly 4 is driven along the track 2 by a rack
and pinion drive mechanism, indicated generally at 6.
[0044] The track can include straight and curved sections (see FIG.
3) and the dolly drive mechanism 6 is configured in the manner
described below to ensure that it operates to accurately and
repeatedly move the dolly 4 (and hence the camera mounted on it)
along the track 2 on curved as well as straight sections of the
track and at transitions between curved and straight sections. This
ability to use rack and pinion type drives with curved dolly tracks
offers significant advantages of the prior art curved systems using
friction drives and winch drives: specifically, it offers greater
accuracy and repeatability compared with friction drives on curved
tracks and allows for tracks with more curvature than is possible
using winches.
[0045] The track 2 may run along the ground or may be elevated
above the ground on a series of stanchions or other supports that
lift or suspend the track above ground level. The track is laid out
to follow a desired path (two-dimensional or three-dimensional)
along which a camera is to travel for shooting a scene (or part of
a scene) in a film or video or the like. When elevated, the
elevation of the track above the ground may vary along the length
of the track and some parts of the track may be elevated whilst
other parts of the track are on the ground.
[0046] In more detail, and looking initially at FIGS. 1 and 2, the
track 2 includes a pair of rails 10, 12 that extend along the track
parallel with one another, held at a fixed distance apart by
sleepers 14. Each rail 10, 12 is an extruded member (preferably of
a light weight material such as an aluminium alloy) having a
support portion 16 and a rail portion 18. The two rails have the
same cross-section and are laid such that the form of one rail
mirrors the other about a center line of the track.
[0047] Each rail 10, 12 has a generally `L` shaped configuration
forming the support portion 16 with a bulbous head forming the rail
portion 18. The base of the `L` provides a mounting surface 20 for
fixing the rail to a respective end of each sleeper 14. The upright
part of the `L` , includes a recessed channel 22 on one side (in
this example the side to which the base of the `L` projects). The
channel opening is formed with a pair of lips 24 top and bottom to
provide the channel with a mouth 26, opening to one side of the
support portion 16, that is narrower (in its vertical dimension)
than the main part of the channel.
[0048] The rail portion 18 protrudes above and is offset to one
side of (the same side as the channel opening) the upright part of
the support portion 18. As best seen in FIG. 2, in this example,
the rail portion 18 has a generally rhombus shape cross-section.
Its lateral dimension is slightly greater than its vertical
dimension in this instance but other shapes of rail can be
used.
[0049] The wheels 30 of the dolly 4 engage the rail portion 18 to
locate the dolly 4 on the track. In this example the wheels are
pairs of horizontally opposed `V` rollers 32 that engage opposite
sides of each rail. In this way they serve to hold the dolly 4 on
track 2 (as well as locating it) on sections of the track that are
inclined or even inverted. There are four sets of rollers 32
respectively at the front and rear of each side of the dolly (two
sets engaging each rail), as best seen in FIG. 3. Although in this
example each set of rollers includes two opposed rollers, each set
of rollers can include two or more rollers.
[0050] A flexible rack 40 of the rack and pinion drive system 6 is
mounted in the channel 22 on the inside of one of the rail
extrusions 12 (the right-hand rail as seen in FIG. 2). The rack 40
is moulded in a flexible rubber-like polymer material. The rack may
be a DURACON rack available for example from KHK Co., Ltd. of
Kawaguchi City, Saitama, Japan (e.g. KHK's rack, part number
DR1-200).
[0051] The flexible rack 40 has a base portion 42 that is received
in the channel 22 and a narrower, toothed rack portion 44 that
protrudes through the mouth 26 of the channel 22 so that the PCD of
the rack is vertically below the rail inline with the vertical
center line (shown in chain-link line in FIG. 2) of the rail. The
lips 24 of the channel 22 retain the rack 40 in place. To assemble
the rack 40 with the rail extrusion 12, the rack 40 can be slid
into the channel from one end of the extrusion.
[0052] Referring again to FIG. 1, the dolly 4 comprises a dolly
chassis 50 that mounts the various components of the dolly and its
drive mechanism (not all of which are shown) and the camera with
its mount (also not shown).
[0053] Each pair of rollers 32 (i.e. wheels) of the dolly 4 is
mounted on a bogie 52, 54 by a pivot 56 that is inline with the
vertical center line of the respective rail. This allows the roller
pairs to pivot slightly to negotiate curves in the track. The
rollers 32 themselves are mounted for rotation on the bogie 52, 54
in respective bearings 58.
[0054] The bogie 54 on the rack side of the dolly 4 is extended
towards the center of the dolly chassis 50 to provide a further
bearing 62 for mounting the pinion 60 of the rack and pinion drive
mechanism 6. The pinion bearing 62 (and hence the rotational axis
of the pinion 60) therefore pivots with the bogie 54 about an axis
on the center line of the rail 12. By mounting the pinion 60 on a
swinging arm in this manner, the correct relationship between the
pinion 60 and the flexible rack 40 that it engages.
[0055] The pinion 60 itself is mounted on a drive shaft 64 that
extends through the bearing 62 to suspend the pinion 60 below the
dolly chassis 50 alongside the rack 40 mounted on the rail 12. The
pinion 60 is a spur gear in this example with teeth on its
periphery that mesh with the rack 40.
[0056] The drive shaft 64 terminates at its upper end above the
dolly chassis 50 (it passes through a part circular slot in the
chassis 50 to enable its pivoting motion on the swinging arm). The
pinion is driven by a dolly drive motor (not shown) mounted on the
dolly chassis 50 via a series of pulleys 66, 68, 70. Two of the
pulleys 66, 68 are mounted vertically above the rail 12 in line
with the vertical center line of the rail. The third pulley 70 is
fixed to the upper end of the pinion drive shaft 64. A toothed belt
(not shown) extends from the dolly drive motor to the upper one 66
of the pulleys mounted in line with the rail. This pulley is locked
to the lower pulley 68 to rotate with it. A further toothed belt
(also not shown) extends from the lower pulley 68 to the pulley 70
at the top end of the pinion drive shaft 64. The motor drives to
upper pulley 66, and consequently the lower pulley 68, via the
first toothed belt, the lower pulley in turn driving the pulley 70
at the top of the pinion drive shaft 64 via the second toothed belt
in order to drive the pinion 60 itself and propel the dolly 4 along
the track 2. The direction of rotation of the motor can be
controlled to control the direction of movement of the dolly 4
along the track 2. The described arrangement of pulleys 66, 68, 70
enables the appropriate tension to be maintained in the toothed
drive belts as the bogie/swinging arm 54 pivots in use.
[0057] Referring to FIG. 3, which shows the dolly 4 in two
different positions along the track 2, it can be seen that as the
dolly 4 travels along the track 2 from a straight section of the
track 2 to a curved section (the direction of motion is indicated
by arrow `A`), the bogies 52, 54 pivot to allow the dolly 4 to
negotiate the curve and the pinion 60 pivots on bogie/swinging arm
54 to maintain the correct position of the pinion 60 relative to
the rack 40 mounted on the rail 12. By mounting the rack 40 on the
rail 12 with its PCD coincident with the vertical center line of
the rail it becomes possible to maintain this correct relationship
between pinion 60 and rack 40 without a complex design of curved
rack irrespective of the curvature of the track. The use of a
flexible rack insert retained in the rail extrusion also minimises
manufacturing difficulties and therefore costs.
[0058] The skilled person will appreciate that the specific
embodiment described above is given by way of example only. Many
and various modifications are possible within the scope of the
invention.
* * * * *